ORNL-TM-4174 POSTIRRADIATION EXAMINATION OF MATERIALS FROM THE MSRE H. E. McCoy B. McNabb AR e This report was prepared as an account of work sponsored by the United States Government, Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. " a 48 " & ORNL-TM-4174 Contract No. W-7405-eng-26 METALS AND CERAMICS DIVISION POSTIRRADIATION EXAMINATION OF MATERJIALS FROM THE MSRE H. E. McCoy B.McNabb DECEMBER 1972 } NOTICE " This report was prepared ss an account of work sponsored by the United States Government. Neither * ; the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, com- pleteness or usefulness of any information, apparatus, product or process disclosed, or represents that its use i - would not infringe privately owned rights, l f ; OAK RIDGE NATIONAL LABORATORY fiy Oak Ridge, Tennessee 37830 operated by UNION CARBIDE CORPORATION for the U.S. ATOMIC ENERGY COMMISSION ~ PISTRIBUTION OF THIS DOCUMENT IS UNLI ITED ~ a 4% CONTENTS ADSIIACE . ot ittt ittt ittt it aa e e it et 1 Introduction . .............. @t e e et e e, 1 The MSRE and Its Operation .. ... ..c.ovuiiniiiininrnneneoeneeasosenenrasascasosoannsns 1 DS P O . L o ettt et it e i ie e e e 2 HStOTY « ot iee et et ie ettt aas it as i et 2 Examination of a Graphite ModeratorElement ........ ... ... ... il 6 Description of Graphite Elements ......... ..o oo 6 Visual Examination of Element 1184 . ...... e e et e e e 8 Chemical Analysis of the ModeratorElement .. ......... .. ..o, 10 Summary of ObServations .. ..........uneinitmiiiiinti it 14 Examination of the Graphite and INOR-8 Surveillance Specimens . .. ...............ocoiivinnn. 14 Examination of INOR-8 Control RodThimble ......... ... i iiiiiiiiiiiann. 15 Physical Description .. ........coiiiieiiininiiniinnannn e ittt 15 UndeformedSamples ...........oiiiiiiiieiiininnann, et etare e 18 Deformed Samples ... ..ovvttiii i i et 23 Summary of Observations . ............uururanniinnenneaoiiiiteteeeiiaaaaes 31 Examination of Freeze Valve 105 ... ... ittt ittt rrieectaonnansrtonnsnnns 31 Physical Description ..............c.ouann. e e e ee e e e 31 Visual and Metallographic Examination ... ..... ... oottt 31 Mechanical Property Tests .. .....ccuiiitiiiirnnnroieascientnnnntnrsoensaosaecsensas 39 Summary of Observations ..............ccceiviiirnnnn et eeesaiaeeceae e 44 Examination of the Sampler Assembly ... ..........oiiiiiiiiiiinon.ts e 44 Physical Description ........ S P 44 11 ) (3 o 021 S R R RN 47 Mist SHield .. .ovie ettt iii e iiettiaeeasaaeaaar st aaa e 54 Summary of Observations ................. Versanen e Cernesieetsanaacesaues 62 Examination of a Copper Sample Capsule ............ e ettt ieree it 65 Physical Description . ... ... e et P 65 Examination...........ccoiiiiiiiennones ettt ia et aanee e 65 Summary of Observations . ... ....uuuiiiniieentor oottt 69 Examination of the Primary Heat Exchanger ....................... I ... 69 Physical DesCrpPtON ... vvvves vt teninteeseneeenmersonsstrtaneranenaaateessuneanns 69 Examination......... e e e ettt et 70 Summary of ObServations .. .........iieeeirenreiae ittt 79 iii Examination of the Coolant Radiator .................... e ettt iteiataea e 79 Physical Description . ... c.iiitiuiitiniiiii ittt ieatarettaratanrensaoasansnacnans 79 DS VAt OIS . o o v ottt eet e ittt ittt et e st e et e 80 Summary 0f Observations .. .....ciiiiiiiadaiieriititireetaataateacataanantrssaaanns 92 UMY L.ttt et ittt i ieseeeeeoaaaasocneasasosusnsnsosnnensnensasosensssnaasanss 92 Acknowledgment ... ... .. oo i i i e i it i e e s 95 L} ¥, Py | POSTIRRADIATION EXAMINATI'ON OF MATERIALS FROM THE MSRE H.E.McCoy B.McNabb - ABSTRACT The Molten-Salt Reactor Experiment operated very successfully. The fuel loop was above 500°C for 30,807 hr and contained fuel salt for 21,040 hr. A surveillance program was active during operation to follow the property changes of the graphite moderator and the INOR-8 structural material. After operation was discontinued in December 1969, several components were removed for examination. These included a graphite moderator element from the core, a control rod thimble, freeze valve 105, the sample cage and mist shield from the fuel salt pump bowl, a copper sampler capsule, tubes and a portion of the shell of the primary heat exchanger, and tubes and two " thermocouple wells from the air-cooled radiator, Examination of these materials showed excellent mutual chemical compatibility between the salts, graphite, and INOR-8. The INOR-8 exposed to fuel salt formed shallow intergranular cracks believed to be due to the ingress of the fission product tellurium. The INOR-8 was also embnttled by exposure to thermal neutrons, and this was attributed to the formation of helium by the ! B(n,a) Li transmutation. ‘ INTRODUCTION The Molten-Salt Reactor Expenment was a unique fluid- fuel reactor' It operated at temperatures around 650°C for more than 30 ,000 hr between 1965 and December 1969. Operation was terminated in 1969 because the technical feasibility and promise of molten salt systems had been demonstrated, and the operating funds were needed for development work associated with advanced concepts of molten-salt reactors. ' S | Surveillance samples of graphite and INOR-8 were removed periodically during operation of the MSRE, and these were examined in detail. After operation, parts of several components were examined. The details of the examinations of the various sets of INOR-8 surveillance samples were reported, 25 and some of the observations made on the various components were discussed in a topical report® dealing with intergranular crackmg of INOR-8. The present report consolidates the observations made on the surveillance samples and the components. The components include a control-rod thimble from the core, a freeze valve that isolated the reactor vessel and a fuel drain tank, the salt sampler cage and mist shield from the fuel salt pump bowl, a portlon of the shell and several tubes from the primary heat exchanger; two thermocouple wells from the coolant circuit, and several tubes from the air radiator i in the coolant c1rcu1t : * THE MSRE AND ITS OPERATION The MSRE and an account of most of its history are described by Haubenreich and Engel,! and Robert- son’ has described in detail all components and systems. Because these references are widely available, the 1. P. N. Haubenreich and J. R. Engel, “Experience with the MSRE,” Nucl. Appl. Technol. 8, 118 (1970). -2, H. E. McCoy, An Evaluation of the Molten-Salt Reactor Experiment Hastelloy N Surveillance Specimens — First Group, ORNL-TM-1997 (November 1967). - 3. H. E. McCoy, An Evaluation of the Molten-SaIt Reactor Expenment Hastelloy N Surveillance Specimens — Second Group, ORNL-TM-2359 (February 1969). 4, H. E. McCoy, An Evaluation of the Molten-Salt Reactor Expenment Hastelloy N Survetllance Specimens — Third Group, ORNL-TM-2647 (January 1970). 5. H. E. McCoy, An Evaluation of the Molten-Salt Reactor Experiment Hastelloy N Survetllance Specimens — Fourth Group, ORNL-TM-3063 (March 1971). 6. H. E. McCoy and B. McNabb, Intergranular Cracking of INOR-8 in the MSRE, ORNL-4829 (November 1972). 7. T. C. Robertson, MSRE Design and Operations Report, Part I — Description of Reactor Design, ORNL-TM-728 (January 1965).. description here is restricted to that necessary for the reader to understand the function of each component - and the significance of the postoperation examination. Descnptron The parts of the MSRE with which we will be concerned are included in the flowsheet in Fig. 1. The - MSRE consisted basically of the primary circuit mcludmg the reactor vessel, a fuel pump, and an intermediate heat exchanger a coolant circuit including the tube side of the intermediate heat exchanger, a coolant pump, and an air radiator; and several auxiliary components associated with fuel and coolant salt storage and fission gas- processing. Al metallic parts that contacted salt were made of a nickel-base alloy known as INOR-8 and now available commercially under the trade names of Hastelloy N and Allvac N. This alloy, developed at Oak Ridge National Laboratory® specifically for use in fluoride salts, has the nominal ' composition Ni—16% Mo—7% Cr—5% Fe—0.05% C. The graphite moderator was made of a special low-porosity graphite, grade CGB, to exclude salt from the. graphite pore structure.’ The graphite was produced in the form of bars 2.5 in. square by 72 in. long. These were machined to 2 in. square with a channel on each face for fuel salt flow. The fuel salt composition was LiF-BeF, -Z1F 4 -UF,4 (65-30-5<1 mole %); the coolant was LiF—34 mole % BeF, . At full power the 1200-gpm fuel stream normally entered the reactor vessel at 632°C and left at 654°C; the maximum outlet temperature at which the reactor operated for any substantial period of time was 663°C (1225°F). When the reactor was at low power, the salt systems were usually nearly isothermal at about 650°C. During extended shutdowns the salt was drained into tanks, where it was kept molten while the c1rculat1ng loops were allowed to cool. Plugs of salt frozen in flattened sections of pipe (“freeze valves™) were used to isolate the drain tanks from the loop. The liquidus temperature of the fuel salt was about 440°C and that of the coolant salt was 459°C, so the loops were heated to 600 to 650°C with external electric heaters before the salt was transferred from the storage tanks Hehum (sometlrnes argon) was the cover gas over the fuel and coolant salts. ~ During operation, samples of fuel salt were obtained by lowering small copper buckets (capsules) into the pool of salt in the pump bowl. The pump bowl served as the surge space for the loop and also for separation of gaseous fission products from a 50-gpm stream of salt sprayed out into the gas space above the salt pool. To protect the sample bucket from the salt spray in the pump bowl, a spiral baffle of INOR-8 extended from the top of the bowl down into the salt pool. A cage of INOR-8 rods inside the spiral baffle guided the sample capsule in the pump bowl. | o The fuel system was contained in a cell in which an atmosphere of nitrogen containing from 2 to 5% oxygen was maintained. This containment atmosphere was recirculated through a system that provided cooling for the control rods and the freeze valves. Most of the coolant piping was exposed to air. History ‘The history of the MSRE during the four years in which it operated at significant power is outlined in Fig. 2. Construction was finished and salt was charged into the tanks late in 1964. Prenuclear testing, including 1100 hr of salt circulation, occupied January through May 1965. During nuclear startup experiments in May through July 1965, fuel salt was circulated for 800 hr. The salt was dreined_, and final H. E. McCoy, “The INOR-8 Story,” ORNL Review 3(2), 35 (1969). 8 . 9. H. E. McCoy and I. R. Weir, Materials Development for Molten- Salt Breeder Reactors, 0RNL-TM-1854 p. 46 (June 1967). - «) N ORNL-DWG 65- 114108 LEGEND " FUEL SALT — COOLANT SALY sevsnsencsnss HELIUM COVER GAS RADIOACTIVE OFF -GAS i —— i ! -1 . OFF-GAS A N T A It DT Y (R LR ABSOLUTE FILTERS BLDG. ra’vtmurm STACK FAN b emrtfimetsans 0 : : X FROM ! FREEZE VALVE (TYP) ~tign COOLANT ; . L g F" SYSTEM t" ¢ __.fi;r;-: i - . y ¥ o 1 1 ABSOLUTE g - P o WATER STEAM Zo_ b #o FILTERS WATER STEAM L : s t i goerdliesd ODOLANT DRAIN TANK Fig. 1. Design flowsheet of the MSRE. INVESTIGATE OFFGAS PLUGGING REPLACE WALVES AND FILTERS RAISE POWER REPAR SAMPLER ATTAN FULL POWER CHECK CONTAINMENT FULL ~POWER RUN =— MAIN BLOWER FALURE ‘REPLACE MAIN BLOWER MELY SALT FROM GAS LINES REPLACE CORE SAMPLES TEST CONTAINMENT RUN WITH ONE BLOWER > WNSTALL SECOND BLOWER ROD QUT OFFGAS LINE CHECK CONTAINMENT 30-doy RUN AT FULL POWER }REFLEEARLNE - DISCONNECTS - SUSTAINED OPERATION AT HIGH POWER REPLACE CORE SAMPLES © TEST CONTAINMENT 02 4868 89 POWER {Mw) Fig. 2. Qutline of the four years of MSRE power operation. SALT N FUEL LOOP POWER S — ORNL~DWG 69-.T253R2 XENON STRIPPING INSPECTION AND REPLACE CORE SAMPLES TEST AND MODIFY FLUORINE DISPOSAL PROCESS FLUSH SALT PROCESS FUEL SALT LOAD URANIM -233 REMOVE LOADING DEVICE 233y 7ERO -POWER PHYSICS EXPERMENTS INVESTIGATE FUEL SALT BEHAVIOR CLEAR OFFGAS LINES REPAR SAMPLER ANO CONTROL ROD DRIVE 233, DYNAMCS TESTS INVESTIGATE GAS W FUEL LOOP HIGH-POWER OPERATION 10 MEASIRE B3y o /e, INVESTIGATE COVER GAS, XENON, AND FISSION PRODUCT BEHAVIOR ADD PLUTONIUM IRRADIATE ENCAPSULATED U MAP F.P. DEPOSITION WITH GAMMA SPECTROMETER MEASURE TRITIUM, SAMPLE FUEL REMOVE CORE ARRAY PUT REACTOR IN STANDBY %, . ) ORNL-DWG T0-2164 120 Ho 100 8 CHROMIUM (ppm) 3 40 30 RUN 8 1 FLUSH & ¢ tie 2 DJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASOND 19€9 1966 1967 1968 - Fig. 3. Corrosion of the MSRE fuel circuit in 235y and 233y power operations, as measured by chromium concentration in the fuel salt. preparations for power operations were made in the fall of 1965. Low-power experiments in December led into the history covered in Fig..2 (see Haubenreich and Engel’° and MSR Program semiannual progress reports for more detail). The nuclear fuel was 33%-enriched 23U, and the UF, concentration in the fuel salt was 0.8 mole % until 1968. Then the uranium was removed by fluorination and 2*2UF, was substituted. The UF, concentration required with 223U was only 0.13 mole %. The composition of the fuel salt was observed by frequent sampling from the pump bowl.!! Aside from the 23U loading and periodic additions of small increments of uranium or plutonium to sustain the nuclear reactivity, the only other additions to the fuel salt were more or less routine small (~10-g) quantities of beryllium and, in two or three experiments, a few grams of zirconium and FeF,. The purpose of these additions was to adjust the U(III)/U(IV) ratio, which affects the corrosion potential and the oxxdatlon state of corrosmn-product iron and nickel and fission product niobium. ' The primary corrosion mechanism in the fuel salt system was selective removal of chromium by - 2UF, + Cr(in alloy) = 2UF; + CrF,(in salt) , and the concentration of chromium in salt samples was the primary indicator of corrosion. Figure 3 shows chromium concentrations observed in the MSRE fuel over the years of power operation. The step-down in chromium concentration in the salt in 1968 was effected by processing the salt after the 235U fluorination. The total increase in chromium in the 4700-kg charge of fuel salt is equivalent to leaching all of the chromium from the 852 ft*> of INOR-8 exposed to fuel salt to a depth of about 0.4 mil. Since the coolant salt did not contain uranium, the corroslon rate was extremely low. During operation, the chromium content of the coolant salt remained at 32 ppm, w1th1n the accuracy of the analysis. 10. P. N. Haubenreich and J, R. Engel, “Experience with the MSRE,” Nucl. Appl. Technol. 8, 118 (1970). 11. R. E. Thoma, Chemical Aspects of MSRE Operation, ORNL-4658 (Decembér 1971). EXAMINATION OF A GRAPHITE MODERATOR ELEMENT Description of Graphite Elements The properties of the grade CGB graphite used to fabricate the moderator elements are given by McCoy and Weir.!2 It is basically a petroleum needle coke that was bonded with coal-tar pitch, extruded to rough shape, and heated to 2800°C. High density and low permeability were achieved through multiple impregnations and heat treatments. The product was well graphitized and highly anisotropic. | The graphite was produced as bars 2.5 in. square by 72 in. long. These bars were machined to several configurations, but most of them had the geometry shown in Fig. 4. These elements were assembled as shown in Fig. 5 to form the core. The elements fit together to form channels for salt flow. Four moderator blocks were left out to leave spaces for three control rod thimbles and a surveillance assembly. The five elements “enclosed” by the four spaces had INOR-8 lifting lugs so that they could be easily removed for examination. 12. H. E. McCoy and J. R. Weir; Materials Debelo_pment for Moiten-Salt Breeder Reactors, ORNL-TM-1854, p. 46 (June 1967). - ' : ORNL~LR-DWG 56874 R TYPICAL MODERATOR STRINGERS SAMPLE PIECE NOTE: NOT TO SCALE Fig. 4. Typical graphite stringer arrangement. @ -t Fig. 5. Reactor core block assembly plan, drawing D-BB-B-40416. | \ i ; PARTS LIST A\ ‘ ‘fi e, MATIOriAw CIRBN 20| . 2. €O) — TOP — b s | owana foo pesomemon {2 e, L mea s WATERM T NATIC AL CARBON CO. AN Y lossssonr| 4 | CORE BlLOCK cP5236 Cz2 | - | N KRR et g sy ae. : L1, ANV Gasssvim | T T i 1.y l . A A b ¥ ; - e s . . - D . i L. ye. S, $ lo#sssceis |¢do C 2 - s w a SENL PAETNC ced CE &G ¢ 5 ) 40 y c/e | - - o o 30 - : FLAT SIDE OF LOWER R Sy _SERIAL A Frry oA 738 ! END OF CORE Block &y 8 (347 Owh. 0048.8-41423) | e e ] . y o Yo K- 7 , s . = Fre ror'o £ core ’ 000-0-dot8| 7 | CORE Biock - cuf [~ ] T Ces . _ L B34 loessit? Z -...._' Ce an e e e _..__.W._-._ . TN . €% c . ¥ I ) ¢ L 3. e|aa |20 7alk2 4|30 [12e forety N D 2 — si3 T i 2ahc < €7 T TYPICAL FUal 43 2 = AEGEND rg: , /od||3 ERIK s 18| [ere 203 CHINNEL 4824 aa T e o S RO - ’ K. - T . /ee0] 98 2 535 = NO SCALL ’ - e e ' - co EllstrUs% Uelslls s88! oks|ls Py X it . ": 2 o o o2 T oL Z 2 car |- : r 72 M ETBMET 20T € 7 . . < — & - € L i cfi 19 s UeSalls wlioy Uccollrifa ‘. e e SEE DETAL A ;a': : ¢ = ’i ol CIa M ETR (6T MCip €A ) CIR[167 [160 1S 7 : €/ ean €z e i . ‘ &) 734 | v T - cay T s PALLEL L% $UA0L SlLENLD, £ U,f:l<2 o8 Lo [esF /54 e 5 ~+~ gL 62| 1A PICIE €77 (1678 [} S/E [1€7p [1€! &, €L ER €7 €iLfy€ SENR) 1€ X fo21x ‘ /4 2 ‘ ¢ne | s 790 2 7£' 0 £ .’fl r{ ‘2 ’£ { 2 3?0 1£ l": 43 A i ::«:’ SR 2 1L g;" - . /a e/A1C/ Lo NEA Y8 < A" €, £43 [1e4 ixf1cL3 1€ /% M, ¢ €/, - .. seEpETAIL'S’ . o b e _“ — - is4 ['4 € \.4 4 4 Al A £ 2ILND Al <4 e L ¥ 1 .f e 1= fce7 . ; P ddedr? | 2 — e e 2 E 3O S 43l EIx NEig ricip M€F N3 116 (198 (19811272 [ N1€4 3 NZ0ZNZNZ NZ N2 N2 N 1632 DPA 27/ PLAN | 58 ¥ 3 : c2g | 133 * 4 L ITRAN {2sax M a'g; : r? Io{l n{ g n{ 4, o?:. : 7 sie scALEA;-LNO NE ’ /PA_pasagerw | 2 c sz ‘ 77 (1673 NCIE [1€7F (167, € STt cle 7 M €A (1€ [ #L 7 % 78 2 v c53 | — vlld, % a“ / o7l arires 8y ) 2 ,.‘1 136 Llnrvallviza L) P : :::_.__ FI ~ c.;’: =y ZENZNE 0? ZNZ ez. €7 1A cik)e £/ ”? S &4 . < /2 feramed, €/ 1211¢/ € el < 50 keV), and the resulting dimensional changes should have been less than 0.1%.2° These dimensional changes should not have resulted in significant changes in the mechanical properties of the graphite, so no tests were run on the samples. Numerous samples were used to study fission product deposition and penetration into the graplnte, and the results of these studles have been summarized elsewhere.? INOR-8 specimens were removed from the surveillance facilities inside and outside the reactor vessel. These specimens were examined visually and metallographically and were subjected to various mechanical property tests. The details of these examinations are presented in other reports??2™25 and will only be summarized here. 16- 16. W. H. Cook, MSR Program Semiannu. Progr. Rep. Aug. 31, 1966, ORNL-4037, pp. 97—-102. 17. W. H. Cook, MSR Program Semiannu. Progr. Rep. Aug. 31, 1967, ORNL4191, pp. 196-200. 18. W. H. Cook, MSR Program Semiannu. Progr. Rep. Aug. 31, 1968, ORNL-4344, pp. 211~-15. 19. W. H. Cook, MSR Program Semiannu. Progr. Rep. Aug. 31, 1969, ORNL-4449, pp. 165—-68. 20. C. R. Kennedy, MSR Program Semiannu. Progr. Rep. Aug. 31, 1968, ORNL-4344, pp. 233--35. (1972). : 22. H. E. McCoy, An Evaluation of the Molten-Salt Reactor Experiment Hastelloy N Surveillance Specimens — First Group, ORNL-TM-1997 (November 1967). 23. H. E. McCoy, An Evaluation of the Molten-Salt Reactor Expenment Hastelloy N Surveillance Specimens — Second Group, ORNL-TM-2359 (February 1969). 24. H. E. McCoy, An Evaluation of the Molten-Salt Reactor Expenment Hastelloy N Surveillance Specimens — Third Group, ORNL-TM-2647 (January 1970). 25. H. E. McCoy, An Evaluation of the Molten-Salt Reactor Experiment Hastelloy N Surveillance Specimens - Fourth Group, ORNL-TM-3063 (March 1971). : 21. M. W. Rosenthal et al., The Development Status of Molten-Salt Breeder Reactors, ORNL-4812, pp. 116-35 4 X o} #) 15 Specimens outside the reactor vessel were above 500°C up to 17,483 hr and received a peak thermal fluence of 2.6 X 10'° neutrons/cm?. They were oxidized, and metallographic examination revealed that the oxide penetrated about 5 mils. The specimens from the core were exposed to fuel salt and were only slightly discolored. They were above 500°C for periods up to 19,136 hr and received thermal fluences up to 1.5 X 10?! neutronsfcm?. Metallographic examination revealed only minor changes in microstructure. A shallow layer of modified structure less than 1 mil thick was noted. This layer etched more rapidly and contained some lamellar product. The amount of this modified layer did not vary systematically with time or temperature of exposure. Experiments produced evidence that the effect was likely due to cold work from machining, causing carbide to precipitate more rapidly near the surface during h1gh -temperature service. This structural change is not of significant importance. The postirradiation mechanical property tests on the INOR-8 samples showed that the high?t_emperature fracture strain of the alloy was decreased by irradiation. This is attributed to the helium produced by the 10B(n,a)?Li transmutation. However, considerable progress has since been made in developing an alloy with modified chemical compositiori that has improved resistance to helium-induced embrittlement.?® Metallographic examination of the deformed surveillance samples revealed shallow intergranular cracking, particularly in samples deformed at 25°C. This type of cracking indicates intergranular embrittlement, and considerable evidence shows that the embrittlement is due to the inward diffusion of the fission product telturium.?” Although the cracks were only a few mils deep in samples from the MSRE, there is considerable concern over how cracks would propagate by this process in a power reactor over a 30-year operating period. o EXAMINATION OF INOR-8 CONTROL ROD THIMBLE Physical Description The MSRE used three control rods fabricated of Gd,0; and Al,0; canned in Inconel 600.2® The control rods 0peiated iriside' thimbles made of 2-in.-OD X 0.065-in.-wall INOR-8 tubing. The assembly before insertion in the MSRE is shown in Fig. 10. Thimble 3 was examined in some detail. The detailed shop drawings for the thimble are shown in Fig. 11. The thimble tubing was made from INOR-8 heat Y-8487, and spacers were machined from INOR-8 heat 5060 (see Table 4 for compositions). The spacers were joined to the thlmble by beads of weld metal that were deposxted on the tubmg through clearance holes in the sleeves. The exterior of the thlmble was exposed to fuel salt and the intefior to the cell enwronment of N, + O,. The tubing was above 500°C for 30,807 hr and received a peak thermal fluence of 1.9 X 10?1 neutrons/cm?. The lower portion of the control rod thimble was severed by electnc arc cutting and moved to the hot cells for examination. Flgure 12 shows the electric arc cu_t at the left (about at the midplane of the core),-the spacer sleeves, and the end closure (located at the bottom of the core). The fuel salt appears “to have wet the INOR-8 near the center of the core, where the tempereture and flux were highest (as shown around the left and_;center;sp'acer 'sleeves), but not at the bottom (as shown on the _right sleeve). Some of 26, M. W. Rosenthal P. N. Haubenrelch H. E. McCoy, and L. E. McNeese, “Recent Progress in Molten-Salt Reactor Development,” At. Energy Rev. 9(3), 60150 (September 1971). 27. H. E. McCoy and B. McNabb, Intergranular Cracking of INOR-8 in the MSRE, ORNL-4829 (November 1972). 28. G. M. Tolson and A. Taboada, MSRE Control Elements: Manufacture, Inspecnon Drawings, and Specifications, ORNL-4123 (July 1967). Fig. 10. Control rod thimble assembly before insertion in the MSRE, Table 4. Heats of INOR-8 examined after exposure in MSRE | PHOTO 74410 § . Content (%) Heat Location Mo Cr Fe Mn C Si S P Cu Co Al v Ti w B Y-8487 Control rod thimble 168 73 41 03 0.05 0.17 0.0075 0.004 0.03 0.1 0.16 0.25 0.007 5060 Rod thimble sleeve 164 7.05 39 045 0.06 0.52 0.006 0.001 001 0.07 001 0.28 0.01 0.005 5094 Freeze valve 105 163 7.1 3.8 0.52 0.07 0.76 0.007 0.001 0.01. 0.08 0.02¢ 0.39 0.05 0.004 5059 Sampler cage 169 6.6 39 035 007 0.59 0.003 0.001 0.07 0.01 0.21 0.01 0.04 5075 Sampler mist shield 164 6.6 40 046 0.07 0.58 0.006 0.003 0.01 006 0.02 0.26 0.02 = 0.09 0.001 5068 Heat exchanger shell 16.5 6.45 4.0 045 0.05 0.58 0.008 0.03 002 0.1 0.01 0.27 0.01 _ - N2-5101 Heat exchanger tubes 164 6.9 39 045 0.06 0.60 0.009 0001 001 0.1 0.01 0.33 0.01 0.06 0.006 5097 Radiator tubes 16.2 7.0 42 047 0.06 0.62 0.01 0.001 0.01 0.18 0.02¢ 0.33 0.20 - 0.02 24717 Thermocouple wells 163 7.1 43 004 0.057 0015 0.003 0.008 0.10 0.14 0.055 - 0.10 047 Y-8699 Radiator header 169 638 32 030 0.06 0.13 0.003 0.03 0.20 0.002 0.24 " 8Al plus Ti. ‘e o« H « " 91 o 17 r—— SMCER SLERVE[PAT'Y) RETANRR BEADS N\ SAALL BE OBFWINED OY BOILDING WITRVALS ?é s \ 490 #ss0 7o sxgrofomnhrod nian mar®s toy \ AL NOTBE WELDEP TO MRT 4 - : + \ WELDS T2 TNRU /T ARE NOME add | COUNTER=CLOCK W/SE PROM PGINT .‘.:3 . ..\ #m> mmom TOM ro sOTTOM 3t : \, L S - l. i > \ e \ : w ‘ »‘!%5 @TNIU- @ - - @m@ @m@ ) (i @mm@ R AR Weok . | cEena e 3 dcu.n ‘ 2 SELL 2 ‘ ~ \ 2z s | k= ke N bkm i ) + { 2 J: I 2 b l ’ < o \\ e : T . Ny et e . [ _ 1 (1 - 1 L | B ; i . . . i -:-f-‘ s ‘ g i : : ‘@3‘ L7 D)~ i1 “'@— : 'l S . [T jsooren waveezis i | 4 . . ‘ - \ . - t - .o ™ . . - \ ?:v:ia::zmnru ! s coem) . 7 i et effe- e —_——af + [9masn remng D apras _grwens (87 RER) - oo z ' : b > _ 1 s — FNIS PARY §RVOLVED 234" YO SHOW ZETAINER BEAD GENER L wu™ & FWEBLE AILEsY. i Tc Tz sART Y/ DEFPORE ATTA e TRS TR A A | E-WEBLLING REQL. 440 - m 2 i P TR NS IT A AL, s i INSPECTyOd MET. #I8-F . v.“ * i kb poe e FoSgnct. ri—— Y Torean - ¢ -4 v ' n. it - -e. PARTS LiST . = _—- ' 55 7 POAT ows, wa. | e DEZCRIPTION (NAME 812,57C., MITER A, L - - - « n — TesTR £y v ¢ FEOG | &\ coNTROL ROD BOTTOM THIMBLE ~ASLKIY IND S A Pogse s ‘ 294} T Y L L . T, i e \ t! - e e o e ——— e e ~ / e -t e 8 y | Y e e °3 9 ' ‘ n ol e £/ t . . £ = e i 0° - a *. \0“ “ b: "" : ) t . — K - i - ol E TN ey . 3 . | . - 7 . . J— —-‘—-nd, a——— and co L_._, F Y . ‘ i~ / | . ’ _i, °;";:’gi:f’;"r?”u""" e e\ SIECTIONATA—S - T/ NAT A=A . T . - ) h‘.*"‘.”‘u‘“‘” ::..A.‘.i.l:' 152 : NE:' k. No. m'“ xxllPTIOIIMJf“tn‘) MIATREIAL, R Lth i e e edt—t b | rwgoms| 4 |Top mia- .x83xhxS2fsLe. inoR-a ‘ - ctil 2 [rweoeu| 9 |sorrommis-.zasxhx8fce. . : L 9 Yeeses-a] | [499% TwRoaT : ; 4. &1 15 (omacon riva. ! |« e ¢+ |rom sanD-s8ee sax imisli.xx vion - . WAOETR AN 7O BLOPED PORVION . | IEEL DETRIL O TRRONY sl ek, (v iy A qm)L Q . _ ! T & \ pezase @) | ? NS | i / - - 3 iy - @ - - 1 | ~ ! L AL . s aen o0 amere— - | & ‘ o8 o . : (mms).. _ : I l e ¢4 - ‘ /22 ~1REpUnL amua{'ffnfi}—_-—_——{ '* . ; a - § . | s VIEW SCALL: FULL YERTICARl YLEN, GENERAL NOTES -' ! ScaLe: FuLi 1~ WaLOING REDLIREMENT]S, ' »3 28 INSPRETION MET-WE- 259 "—5% TYP &O PLACAS — " l’-' 3 SCH. K, . per o e WSS Tl s e A e LA S oW ! L a REPERENCE DRAWINGS 0. v _:: N OAK 0oL NATIONAL LABORATORY r . Py ‘Aw' + PLAGED oPTRATED WY 3 i senz Umion Cansipe NucLEAR ComPany : ¥ g DIVISION OF UMION CARMIDE e | eerau © nETALL o o, momeser \h r - sy FEALA: R " 4 @ ’Tmnm ynLE L2 g~ - .5 ' . Pra = * GENERAL SPECITCATIONS on vtz i ) , | e LN TP 4 sLacHs ScaLe: 21" oy 'z"“ TRt ¥ ) -y . TP, ‘.I ~— SEE prrau.@ PACTIONS & 1 ShENK AL BHARP EDEES. 1/od WAL COR T 3 B ES, Lt T L FLE REVNIONS ATE o e I# Prxr® o4 om rrap TYP WELD DETA/. 4 soor tto pme & e e = - | VRS e et o 15 e e T /5763 ‘ SLOT SMEN 310N TYE 83 MAcks bavmine s AR AL, - 2225 2 FOUEIES MOt OF 0 ‘ L.z Ajad? M@ :"t:n‘:. ,w.::f_ fi-.m:mmym % ’-’55"’9‘ l Scaik: B e s nende R | SN A4S NOrED 20 =1 Socoromce R ‘38{ ’**f-e.:‘ E 40+ M, 3 TYe ¥ FuacES - e L1198 925,29 - s et ot . . MZCTHA KB IUT . Fig. 11. Control rod bottom thimble assembly and details, drawing BB-B-56346E. 18 Fig. 12. Portion of control rod thimble examined after operation of MSRE was terminated. The thimble is made of 2-in.-OD X 0.065-in.-wall INOR-8 tubing (heat Y-8487). The electric arc cut on the left was near the center line of the core. : the variations in light and dark areas are due to uneven lighting for the several photographs that make up Fig. 12. | The first saw cut was made through the sleeve and thimble nearest the electric arc cut. The spacer sleeve had been machined with ribs 0.100 in. high and 0.125 in. wide to position it relative to the graphite moderator, and the sleeve had four drilled holes through which weld beads were deposited on the thimble to hold the sleeve in place. According to the shop drawings, the minimum and maximum diametral clearances between the thimble and the sleeve were 0.000 and 0.015 in, respectively. Thus salt would likely enter this annular region and be in contact with most of the metal surfaces. Undeformed Samples Samples of the control rod thimble and the spacer sleeve were cut and examined to determine their condition at the end of service. Typical photomicrographs of the inside of the thimble tube are shown in Fig. 13. This surface was oxidized to a depth of about 2 mils by the cell environment of nitrogen containing 2 to 5% 0, . The oxidation process modified the microstructure to a depth of 4 mils, likely by the selective removal of chromium. o ‘_ | Photomicrographs of one of the weld beads are shown in Fig. 14. All of the surface shown was exposed to flowing fuel salt. Some grains were dislodged near the surface, and grain boundaries are visible in the as-polished condition to a depth of 1 to 1.5 mils. | | Photomicrographs involving the interface between the thimble and sleeve are shown in Fig. 15. Figure 15(2) shows the annular region with a separation of about 7 mils and some salt present. Few surface irregularities are visible at a magnification of 100x, indicating that they are considerably below 1 mil. Figure 15(b) is a 500x view of the thimble and shows some surface cracks to a depth of 0.3 mil. The outside of the sleeve is shown in Fig. 15(c); a few grain boundaries to a depth of about 1 mil are visible. Additional photomicrographs of the sleeve are shown in Fig. 16. The sleeve material does not appear to have received much work, since the carbide is very inhomogeneously distributed. Grain size is larger than usual away from the stringers. The inner and outer surfaces both have modified structures. A higher magnification view of the inner surface [Fig. 16(b)] shows that much of the modification is a high density of primary carbide. The outer surface [Fig. 16(c)] has a shallow layer of small grains, likely due to a working operation, o «h n ) (2} 19 R— 54244 D.038 INCHES I ' - Fig. 13. Inner surface of INOR-8 control thimble in as-removed condition. This surface was exposed to cell environment of N, containing 2 to 5% O,. (@) As polished;_ (b) etched; (¢} etched, typical microstructure. Etchant: aqua regia. Reduced 30.5%. ' ’ o S | 20 R-54237) - I~ e 0.007 INCHES 500 o o 8 IS 0.007 INCHES S00X fem Fig. 14. Outer surface of INOR-8 control rod thimble showing weld deposit made to hold spacér sleeve. The weld . surface was exposed to flowing salt. (@) As polished; (b) etched with aqua regia. o _ . i i - - «} ) —_— e 10010 . - I 0.035 INCHES 100X oo™ - 0.007 INCHES 300x% Fig. 15. As-polished surfaces of INOR-8 control rod thimble and sleeve. (@) Annulus between thimble and sleeve; thimble surface is in upper part of picture. (b) Outside surface of control rod thimble, showing presence of some salt and shallow surface cracking. (¢) Outside surface of sleeve; surface exposed to flowing fuel salt. 22 100X 0.035 INCHES r—————————— ey tog0 . 1 0.030 In. 123 0.007 INCHES » kst 900X o I 1= 15 0.007 INCHES !u 300X I Fig. 16. INOR-8 control rod sleeve. Etched with aqua regia. (@) General microstructure; inner surface is on left and outer surface is on right. (b) Inner surface of sleeve. (c) Outer surface of sleeve. Reduced 30.5%. oy " s -l * ) ) 23 A second cut was made away, from the sleeve, and typical photomicrographs are shown in Fig. 17. This part of the thimble was exposed: to flowing salt. Some of the grain boundaries are v1s1b1e in the as-polished condition. to a depth of about 4 mils, and there is some surface modxficatlon [Fig. 17(a)] Etching [Fig. 17(b)] delineates more of the grain structure and shows the shallow surface modification. Microprobe scans were run on the thimble samples that were taken from under the sleeve and outside the sleeve. In the first case the thimble wall was exposed to almost static fuel salt, and no gradients in iron and chromium concentration could be detected within the 3-um region of uncertainty near the surface, The sample outside the sleeve, which was exposed to flowing fuel salt, was depleted in chromium to a depth of almost 20 um and in iron to a depth of 10 um (Fig. 18). Thus the amount of corrosion that occurred varied considerably in the two regions. Measureménts were not actually made, but we would expect similar results for the spacer sleeve. The inside surface was exposed to almost static salt and was likely not corroded detectably. The outside surface was exposed to flowing salt and probably was depleted in iron and chromium. Deformed Samples The next step was to deform some of the thimble and the sleeve to determine whether surface cracks were formed similar to those noted in the surveillance samples. Since the product was tubular, we used a relatively quick and cheap ring test. The fixture shown in Fig. 19 was made by (1) cutting % in. through a 1-in.-thick carbon steel plate with a 2.in.-diam hole saw, (2) cutting out the partially cut region with ample clearance around the hole, (3) cutting the plate in two along the diameter and removing 1% in. of material on each side of the cut, and (4) tapping a % -in.-diam thread into the two pleces Then rings % in. wide were cut from the thimble and the sleeve. They fit into the groove and were pulled to failure, with the resultant geometry shown in Fig. 19. The initial loadmg curves include strain associated with the ring conforming to the geometly of the grip, so we cannot tell precisely how much the sample is deforming. Thus the yield strength and the elongation are only relative numbers, but the ultimate tensile strength and reduction in area obtained from these tests are true values. Obviously, this type of test is deficient in giving good mechanical property data, but is sufficient for deforming the matenal and observing the mcxdence of surface cracking. : " The tensile properties of the rings are shown in Table 5. The test results show the following important facts: - ' 1. All the unannealed specimens of heat Y-8487 tested at 25°C have a “yield stress” of 52,000 to 61,000 psi, with these values appearing to be random in the variables examined. 2. At 25°C the crosshead displacement was about 1.2 in. for the unirradiated tubing and O 4 to 0.5 in. -for the irradiated tubing. Again the variations from 0.4 to 0.5 in. appeared random. *3. The yield stresses at 650°C were about equwalent for irradiated and unirradiated tubing. However the crosshead displacement before fracture decreased from about 0.4 in. to 0.1 in, after irradiation. This was due to embrittlement from helium formed from the ' *B(r, @)’Li transmutation. .4. No material of heat 5060 (sleeve matenal) is available for unirradiated tests, but the vendor’s cé;tification sheet showed a yield stress of 46,300 psi, an ultimate tensile stress of 117,000 psi, and a fracture strain of 52%. The values that we obtained show higher strengths and lower ductility. Several of the specimens that had been strained were examined metallographically to determine the extent of cracking during straining. Photomicrographs of the control rod thimble, which was exposed to flowing salt, are shown in Fig. 20. The inside surface was oxidized, and the oxide cracked as the specimen was strained. The oxide should be brittle, but it is important that these cracks did not penetrate the metal. 1 o ) x00¢ | 0] —fi = |-a e @ \'\ y Jrl / .I ;t’ ‘= Z’ {2 ,’/“::,0 :;’ /2 A 4 veccsssoa] Z 1TURING KoL X :4’ Whve A8 are Nt ‘I,_i_, ~ ;_i ot 7 . g =% e 1 o A 2 e ||/ s JA & [péiesssars| fEul-LE ZoRJanTEL METAL TS -‘?“-a &fi 55155_._ i | T s $ j’-’l =t = t [ & [Pamd-asy 2 [500.TC imcomel swemrm - _ sl |; ; il 5‘ . l c‘b‘fi”’;flzc ;%" 7 ©Go.cosEsN 4 '}‘ Tow, FIBER FRAX IntoL. Pasta TCOE STOH{‘!T" "9 Tr:_‘"'fi 2 ‘ r 7 " \ Pl Bewome Arrdcwning B [oiscassmey Av RO SUEET 18 ML Tw i N T : X ‘_3 A - ! T T __ N ’ ' 2 PEC-Eygmy | Sna STock S™M e Tmon 277 100 NS S ba fl;' | :fl"—;%be‘b'- THR o 16H ! : " . i \"L:;' ! —_ Ps.2§ ) : - ' ‘ NOTES: ' 2N ———— 3 ‘ o AND ‘ ' /,/‘; I» PREFIRE INSULATION - ITEM 7 (@/600°F /¥ AiR ' weLn HID FOR 4 HouRsS. 9 E\fup of Hasker Box C2UTEM @) TO BE CUT TO MATCH COUNT.». e =~ CF ‘QLEZ,_'.'. YAVE <fis.za AL , 3. ITEM S USED ON ITEM{@ OK % M - DLEENDING SN LOCATION IN SYYTEM. Sid (D . . F%%E 26 VALVE E WG E' 5G-D-4i1%12. ' . P IENTATION ] | 3 — = ‘ e DWG, E-NN-B 55449 i £, 1o f FUEL PROCEJHNG_QEL._L._ ' . T - 5 : B ' | A“"' A FOR FV, 104, /05, dma- SEE —_—— — = — =YYV | F&%EI%J%ATYS}QVE —— ] / Owa.£-65-0-52395 ! \ O e é‘rqy_'fifl-____.f , (E-G6-0-ai512) RBAIN CLLE , / N FIELD i ! T BROUGNT Cur %o ' : DS CONNETT — a 2YCS &£AlN END LOCATE MEAT TO| SHAOUD . A\ | A A / ‘ _ , . e | }ew J;AD 2 el elte ‘ END PLATE AND CENTER e . W~ 8 - JauacH SND , * Cw Tom Gm VALrE " wok -8 INSUL.AT 124 =i i e _ _ see ey A ‘) WD FAD [ ' Ri2y 1’ I ‘ D-wi-8 2503/, _ @ !!_—___,_ 5L IL $H. 40 (NOX-B PiP&E.(Ker) _ B ‘ NO INSULA P R APl o \ 3 o " - -—-‘_.--__._..._._\ . r . \, - -..'w E. ) \/ - ) N / . : B A » i _ ! e — i N . : '\. N S A ! _\S - \ . red o0 _ el |1] e [ BAND-As e0D (Smidces) 7 | - | Ve Wil Iaore SweeT Yoo / Is — M =, 020 THK L S&wD| SHedTw To mry. Do Nor psip / . , . _ _ | g:,‘f:;?""’”‘ Fomca / ' _ 878" 3 Lons WELDING _REQUIREMENTS Tt T ’ ;T T - ') INTERNAL E)m' L I\ . : e e ' A TYe -’! A < 4 i neof?f?a"g RS WELDING | INSPECTION | INSP, ST | WEL m*fl! ‘ M Vik r#as 28 vave MoDiFicATION P A108-105 126 Iz 2Gurit $5385 (1 é’r” i o | P3.2s Mar.waaod CE* 3%% A FRisze ik, £ AHATER inSvinyion) Emmzs7490 (1 . - - . = = ' - e ! '“‘M‘) 26,35 [werwezo0] E* Imer-wi-glmer.ws-a :’E' P'-""""'O.':" - FRELZE VAwves . :*.E'""-:"."- f R5-23 |Mer-wkzea] €0 [Merwa-Z |Meiv-ws.3 _ F:: "‘"‘;,‘“""" ““‘t _M-S-_n:aw ‘ Pserl [Merwit 2oy *ET* | Mar-Wa hagraws E§ETF VALvg S-767 Few le ! NOTE : % UG 35 OTrHaRwWIsE Nergd Rpwg Inv Reactil FoaL Fusd 202 Tave Coue g .- -'.~ . ‘m‘fmcouFuj (Fes) smdee ”5: v _ ’ REFERENCE DRAWINGS NO. . ATTACHED N dccomEAnce WirH : . RIDGE NATIONAL LABORATORY I MSR-G3-940; ENTITLED Onx o':*mm o ; ‘PEOCEDURE FOR WeELDNG THERMO COUpLES o UNioN CARBIDE NUCLEAR COMPANY _ . ! O MSRE FPrrinG f COMponenTS" : S _ DIVISION OF UNION CARBIDE CORPORATION i TAreD Mo /132, 1963 OAK RIOGE, TENNESSEE | ; { B | maufb see Den 30 AT ' LTS ON DIMENSIONS UNLESS BLDG. _ _ o , GENERAL SPECIFICATIONS _ | MSRE NO. 72, - Ald 7 See Dow 2737 Foar? 'Y r/ : ! , onmt*mvu - 72, - ?LT : FRACTIONS & ——— | 1. BREAK ALL SHARP EDGES 1/64 MAX. " , NO. REVISIONS DATE [APPO| APPD - ‘ . |é MSRE FREEZE VALVE DRAWN T DATE ?ar e DECMALS AR . : o CHURTE Inerraa](y 11916 —_— 3. ROUGHNESS HEIGHT OF MACHINED, 5 | : _ BREACIQ 17RO APPAOAD _ ANGLES * SURFACES BHALL NOT EXCEED \/ D m DATE 2&3 . B inats . - : (mmmmmm A ) Liomiles, m = X it Fig. 26. Fabrication drawings for freeze valve 105, drawing D-GG-C-55509. _— ARE IN ACCORDANCE WATH ASA ) —0 =5C | . [ ol 2 et gl , _‘ , | SME ) 846.11968) g 453 %433.251D | sz 5| k 5 | M7Z0TA4RG 133D @ 33 i - — &, DESCRIFTION .a” 0 # - AL PREFIRE INSULATION - ITsMiSER? & e 'C IN AR FOR 4 pOURS. ; . oqp—{*s 23 SUBSELTI0 METHOD OF MiDis.inT - N | 1 DEise OUT PoOP RIVETS CEAMEST ! ! S HALYES o HEATER BALE & LAt § . N R liiree BaLE, - . 1) LEUTMLVIMCM S, Z& SLETS IN ~SATER BrSE A oer FOR COCLING AIR TUBES. o \ TRIMTO <5 ?s 7 #udem 3 MARE THER MISIEIIHT _ns AL SHCWA ' i - : e dted N DWW & Ty i . ! 3 SN2, . . s " ;I 3 noard DY RREASIEV I8 NENTER BASE ¥ N5TML: _- I' I i H . S ATUFR OPEN.' 25 ARE .G St NG | L 4 ' \]-/ : TVBES Witrm FIBFLABAL INSUEH T % f ! " l ; ! INSTARLL INSULAT N S8R SLATEL. it ; ~ ' v I I 4 A : ! ! ! F I~ ; oo 1 t:‘ . " “BEND FEv YD roatian o, . » ' |t - OF wialin huu ¥, 7mcK, P ¢ t i 3,23 ".‘ t I . oy ._ ./ :': ey 3 o ]y i | ~ a ; 3 ', t ! ' PEATER SRGE \fl'x.r' - ‘ : ‘ kgl LUR MIBROR INSULATION N - : . ’ ;fi",g ‘ Co. Dwa. ~o%. . ‘/ - | o it =+ . Firt L @17y Got1BA : i . o h J ‘ §-1/58 §.'_‘ -") ! e !.‘ 5_”5_‘: (_‘;_;/-. . L K ¢ . ; i o e h‘ - S & M. ¥ _' ' ! 2y Aered £ORIS, DERESU IMDICATED WELL ! - BEROAE- DL ING g NOLE FOR ITEM @ or il 8 DER SECTION ) 4— & : A : Fom ComrwuAniont 5 e ; o 1 oer or scats - see DV 24a vy B 1P\ - =: --'" - - e . . e . / o7 N S o } 210 seass rFrEx posE o080 AL A : 24T L& . (Cor i FNETH TO ’ suiT), —y 7Y . - J ORIEAT INLET. - ttF TO SUIT EXSTA% AR S.=r.y, ‘ | . THI% DRAWING RTFLECTS . T AA T "‘.":"“’ ~BLOW _DOWN NEe B2 .5 33ites (\ ) ‘ oLl ATTACHING TC v, " . CrahGEs . 2-23. AN L R S * n,,_&é.L, ’e”" !“!{ Aim 3:3-5 I L il WEAIBAT A5 NEIEC - e il 5 e | £ JIrmwe) Imerows-s REFERENCE BRAVINGS | m Py 35 F_erwe ¥ Lyerasa uum—m 2oa oL £ & Jignweg iNerygy . od . e U, 7. . P31 5 ."“c"" per-n ey .: x3-3 llmemm cmmmn . i "‘ll'h:l! mm TITEANAL FADRICATION | EXTEMNAL FABRICATION < - = UG ~ ® INSPECTION PROCEDURE MSRE w C.3 ‘Jo - |_GENERAL SPECIFICATIONS | TOLEWCES UMLESS et P i - P o ssemmmonm s s oo an o wer ety T R SRORGS - i FREEZS VALYE MIDFiCa™ 5, stmes-se Semcimsdcieire o mame Saurmes et et |1 o s sware epoes. |emacrions - - ST T BV 'S8, 23,010 DR\ o) P e v e ) pEChALS - 0T | s 12504 ' g P gt iyl it S S raoiirlt SRR —_ T NPPROVED ! ATe NPROND :' ATt m/ P T AR PR WP SeE-o 3m" SURFACE Fimsh |ANGLES ] ) Yin S ] - _ SHALL NOT EXCEED: ;< - APPROVED Vo MPRVD | T - L) =4 1ASA BARL 196D A S : 33 433-6.51 3 lseyns ‘: Fig. 27. Modifications for freeze valve 105, drawing R-GG-C-56395. P2CTAGKE o= ORNL~DWG 71-2450 1% in. SCHEDULE 40 PIPE 0.0239-in, THICK SHIM STOCK I L i ) ™ A I, : / ) 0.005-in. THICK Z i ; Z 2 ,'/1 / . i g kY \ s i} i . \INSULAT|ON %-in. ODx 0042 - in.-WALL TUBING THERMOCOUPLES (a) ORIGINAL DESIGN THERMOCOUPLE LT //////////////////I///I,,/ 7, ) z Y & Y ///////////I/IJ"////////// N LOCATION OF FAILURE 0.800~in. OD x0020- in.~WALL TUBING AIR INLET OUTLETS | (4) MODIFICATION Fig. 28. Diagram showing possible cause of freeze-valve failure after modification. (\1‘:——-‘-—‘/ ! 1o priuw ¢ __\-———1———‘ - ST \ s uRATER SLENYES | _mem_coum BMATENLION AV _TUSEMOLOUELE: DETRILS - BRE - WG T060 ‘ ‘ L P Lo 0P Vibw Yo ll:u— oy ;"!J.fi—‘!_ 35 /EQ;’ T o7V -...___'._.__|zé'_ — Lue- %109 :’a "_ I:V 08 “'k e, 54 L11N o e e ———— - ————— BELLOWE AL JURSOD viEwAA e e F‘QEEZ(‘.’ VALVE * FV |Q5 /k"‘ Tletantue__mesie to $ert) , ]\ . =~ Yo sy _tmetwo o OTC - IYPICAL LoOP EREEZE VALVES V107, BV40B, V109 t EV-1O une 204 SUEATILC THIRMECOUPLE LAADY Lot 204 A0 THEY AL ouTLlt TUDS LOCATE ok WDR PACHE AL MeRELE WLAY LiNE L VOCATE on 408 BACIG MR WeTILE WLET NS e A F:.‘? H;Z L‘ _ -.\/A;L_'V £ Y EN-104 Te . N TN el 1!;1-) 3‘(’7» e i g N8 | ] ; UL 1TICE T : s s e e . ne B (Lranat itr.LaT 2080 : . - ] ehisas Witen TG DETAILA 3 cpap, N0 3 e wo. rEvON TYPICAL 0P \nE_-w = - 10 ST - - 9-%.63 ‘.S - ;Clu“’ REEZE VALVES §4-104 -105 .- =108, <109, w1lO , -1, o FOR CousTRUCTION AND TWARMOCOUPLE DRTAWS e O-GG-C-53509 Fig. 29. Freeze valve and thermocouple locations, drawing D-HH-B-4054 3. i f EQEEZE‘ VALVES EV- |05 ¢ FV- lO(. o DT *2 2] _ER TolwA®mo LT T MY AMITwa — WS g, Lt S 1T Te tetuo — PP_!_JP_!..Y‘_E!. st DOTAL . o ) gy . s q‘i— . - 5" .-‘- 5 - i ..... EEZE VALVES EV-NLERV-NZ . - Eie M s - am g . - - e YRL LOADINGY STG. BYS. MY LINA T/C LOSATICNT (K aw® S04SR WTMARE BRRRE vAwe w/sinansy e - S5OV '-ns u‘lan 1 flm sfltm Wil Eee, VLI D A -A »- Q...,.} lvu. ".mfl Ilu flst w\- m‘m. I"ur.u o Dihig WAL Mqfl | -afl.lfl" M-‘ Smtb\ N\\' lf?uu.‘wu Vhy Nt'- 'sh-'| ‘Uflttu\ u\n APUCATIo BiAn nu.t Tutlutstufl.t 'thlus.fl el b e Ly, sonot - - - |ll-'-ic'1‘0 d\ avk § l\\n - ‘7004 PEARLE VMW En - lssinlq 4 'It- ¢ - Suaa” [FLOV « DTAR S18idm - DRAWS "A0K € _;‘_,ls TR CovLAmT HaLy HYY am & LA .8nY | LU P, | FURL § COOLALT BT Svn 8t - HAT St iy [Feeadsin0 . REFERENCE DRAWINGS WG, NO. MOLTEL AT EEALCTER T kRiMi=nT -..'...',53‘ FREEZt VALVES THEQUOCOUPLE (ocA™ious ommmmmm Union CARBIDENUCLEARCOMPANY Mol — APPROVE D L] m’ e e 5-n-¢3l . | oenus- 2054317 120734KH LD n - -~ Fig. 30. Bottom portion of freeze valve 105. e e —————— Fig. 31. Closeup of the bottom of freeze valve 105 showing INOR-8 gas inlet and outlet line of type 304 stainless steel that was commoded completely. The crusty substance is the salt. Note that there is no salt in the air annulus. R-54212 Fig. 32. Weld at one end of cooling shroud. The crack begins at the round salt stain and ’proceed's for about 1 in, along the pipe. The arrow points to the salt stain with the crack at 90° to the arrow. ' - ' . R-b5164 i 37 Fig. 33. INOR-8 tube wall of freeze valve 105 where the failure occured. As polished, S0X. Bottom surface was exposed to fuel salt and the upper surface to air, with some salt after the leak occurred. Reduced 15%. 38 PHOTO 4185-71 "y Fig. 34. INOR-8 tube wall of freeze valve 105 where the faflure occurred. The weld supports the end of the cooling shroud; the failure occurred outside the cooling shroud. Etchant: aqua regia. 50X. Reduced 15%. a“ , 39 A comparison of the etched and Unetched views shows that somié attack occurred along the crack and the -outer surface of one tubing and that etchmg completely removed material from the attacked region. The attack was likely due to the simultaneous exposure of the INOR-8 to salt and moist air, and probably involved the selective removal of chromium and iron, leaving metal that was heavily attacked by the etchant. No such attack occurred on the inside, where only salt was present. The failure that released salt was due to thermal fatigue. The cooling shroud was 1mt1ally 0.020 in. thick, but the added cooling tubes increased the thickness to 0.083 in. on the bottom. This made the shroud relatively rigid on the bottom. During freezing and thawing, the outer part of the shroud changed temperature more rapidly than the wall of the salt-containing tube. Whereas the outer part of the shroud was- originally thin enough to deflect to accommodate the differences in length of the two members, the field modifications made the bottom portion quite rigid. The result was that differences in temperature imposed on the cooling shroud a stress that was tranéférred by the rigid (%-in.) end plate to the tube wall. A crack was nucleated at the surface and propagated through the pipe wall during the numerous cycles. . Parts of three tubes are visible in Figs. 30 and 31. The large tube in .reldtively good condition is the type 304 stainless steel air inlet tube, the center tube is the original INOR-8 air outlet tube with two ‘thermocouples visible, and the hole is the remains of the type 304 stainless steel outlet tube. The original 'INOR-8 air inlet line was capped off and is hidden by the salt. Attack of the type 304 stainless steel by salt when air was present is as expected. The relative nobility of INOR-8 in this environment is a strong argument for the use of INOR-8 where salt may be present. Mechanijcal Properfy Tests Three rings % ¢ in. wide were cut from the pipe away from the flattened section and were pulled in tension in the same manner as previously described for the control rod thimble rings. One rectangular piece was cut and bend-tested with the inside surface of the pipe in tension. Table 6 lists the observed mechanical . properties. The yield stress was essentially unchanged, and the ultimate stress was reduced about 15% from the vendor’s certified properties. The elongation was reduced considerably but was still greater than 25%. A gage section is difficult to define in a ring test, so crosshead travel and reduction in area are reported for the rings from freeze valve 105 rather than percent elongation. The bend test was discontinued because of strain limitations of the bend fixture after 0.41 in. crosshead travel, which corresponds to 33% strain in the outer fibers of the specimen and to a 90° bend angle. The yield stress calculated from the forces on the bend specimen is too high because elastic formulas were used in the calculation and the specimen deformed plastically, but this calculated quantity is useful for comparison with other bend tests that will be reported later for the mist shield. ' Table 6. Results of mechanical property tests on specimens from freeze valve 105 (heat 5094) at 25°C and a deformation rate of 0.05 in./min Yield Ultimate Crosshead Reduction Type of test stress tensile stress travel in area (psi) (psi) (in.) (%) ~ Vendot’s, tensile - 45,800 106,800 52.6 Ring, tensile 45,800 89,700 0.72 25 Ring, tensile " 48,900 - 90,100 0.59 29 Ring, tensile 41,900 90,300. 0.73 37 Wall segment, bend 71,300 0.41 334 2Maximum strain in outer fibers. 40 * Fig. 35. INOR-8 surfaces exposed to salt in freeze valve 105 after deformation at 25°C. (z) Fracture of ring specimen pulled in tension. Note surface cracks near fracture. 4X. (b) Surface of bend specimen. Note some cracks on surface and edge cracks. 7X. Reduced 18.5%. Figure 35 shows the tension side of the bend specimen. Some very fine shallow cracks are visible on the surface in tension, and cracking is visible at the edges in the burrs remaining from the remote cutting operation. . _ | _ One of the three tensile-tested rings was examined metallographically. Figure 36 is a composite of photomicrographs of a section through the specimen showing the inside surface, which was exposed to fuel salt (top), and the outside, which was exposed to the cell environment of 2 to 5% O, in nitrogen. The reason for the unevenness of the oxide on the outside is not known. Possibly it was due to corrosion after the leak, although the rings were cut approximately 4 in. away from the nearest visible residue from the salt leak. Figure 37 shows at 500x the oxide in one of the worst areas. The crack ends tend to be blunted and did not penetrate the metal beyond the oxidized surface. Figure 38 shows at 500x the inside of the pipe exposed to fuel salt. About 1 crack per grain or 240 cracks per inch show, but the cracks are shallow and blunt, having an average depth of 0.75 mil and a maximum depth of 1.5 mils. Figure 39 shows that a large amount of strain occurred before fracture. -—— O — Fig. 36. Composite of photomicrographs of INOR-8 ring from freeze valve 105 that was pulled in tension. Upper surface was exposed to salt and the lower surface to thg‘ cell environment of Ny plus 2 to 5% O;. Top portion is the tension side, and the lower part is the compression side. a ¥ 42 | = u 100°0L U £00'0) S3H X00S | Ul SO0 ut hCo.o“ oNELOQC ‘ul _O0.0m W E000p X00S | w S00°Q) S3IHONI 2000 n LOO'Q) —t] The 8 B -9 Q S Comy Q m - O g o= sg § & Yoy ES ~ 3 25 §F o g g s owing s Fig. 37. INOR-8 tensile sample of freeze valve 105 sh: cracks penetrated only the depth of the oxide. (g) As polished 43 ‘ul }O0'0) T4 | WE00'0] X00S | U600 -5IHINL LOO'C - S & G R < w100l W 1000 s e - .M 4 i i WEOO' X00S | W 6000 U 200°0) Ay S3IHONI L0070 e P S S i s s S i (b) etched with lactic acid, ished; (a) As pol from freeze valve 105 ile specimen 8 tens de of an INOR- ig. 38. Salt si F HNO;, HCi 44 Fig. 39. Fracture of an INOR-8 ring specimen from freeze valve 105 that was deformed at 25°C. {a) As pollshed ) etched with lactlc acid, HNO3, HCL. 40X . Reduced 29.5 %. Summary of Observations The failure in freeze valve 105 was due to thermal fatigue as a result of the cooling shroud being too rigid. The mechanical properties of the INOR-8 in the freeze valve were not degraded seriously by the long exposure to fuel salt containing some fission products. Numerous intergranular cracks were formed on the surfaces exposed to the salt during postoperation deformation. These cracks were similar to those on the surfaces from the primary circuit but were shallower. EXAMINATION OF THE SAMPLER ASSEMBLY Physical Description A schematic view of the MSRE fuel pump is shown in Fig. 40; more details are reported elsewhere.?? The components examined were the mist shield and the sampler cage. The fabrication drawings for these parts are shown in Fig. 41, Salt-sample capsules or additions of uranium or beryllium were lowered by a windlass arrangement into the sampler cage. The mist shield was provided to minimize the amount of salt spray that would reach the sampler. The vertical sampler cage rods were Y, in. in diameter and were made of INOR-8 heat 5059, and the mist shield was made of Y;-in. sheet of INOR-8 heat 5075 (see Table 4 for 29. R. C. Robertson, MSRE Design and Operatiohs Report, Part I, Description of Reactor Design, ORNL-TM-728 (January 1965). 45 3 A A R e . ORNL-LR-OWG-36043-8R2 ‘e - WA 1 v‘\ s \ s ! AN/ | /‘// ;&a SHAFT ?‘fi\ _ © COUPLI COOLED ' \ _ R _ MOTOR ,\/ Ny SHAFT SEAL R/ {Sea Inset) cmpoe—— . ) ¢§ S==CT f / \1 LEAK ' N DETE Ol BREATHE & / \ LUBE OIL IN e N / /] ! / % BALL BEARINGS / j /% (Face to Face) BEARING HOUSING 5\ 7 : ¢ / § BALL BEARINGS GAS PURGE IN / ' A\? : (Bock to Bock ) _-SHAFT SEAL (Ses Insat}—/ ' A ] " i - LUBE oL ouT SHIELD COOLANT PASSAGES % 7 SEAL OIL LEAKAGE {In Parallel With Lube Oil) | . S : ' DRAIN SHIELD PLUG | " LEAK DETECTOR- GAS PURGE OUT (See Inset) | | © SAMPLER ENRICHER GAS FILLED EXPANSION - L , (Out of Section) SPACE (See Inset) BUBBLE TYPE LEVEL INDICATOR OPERATING LEVEL STRIPPER {Sproy Ring) SPRAY i ) . e e ey To Overflow Tank Fig. 40. Section of MSRE fuel 'pump with details of several areas. The mist shield and the sampler cage examined are shown in the lower left insert. . _ z —% Ok DRILL THRU | 3 HOLES AS SHOWN ! NPT 00\ i)\ A _ ‘_//—IE ‘ & | ¥ ) 1{ N { AUSY. NO. — Fi00Gd ARSENBL TTLE _ VI DnawING ko, ACSGAG=/E MaTRRALIBOR™) (METLH5334] AN ; 2 NN N\ R 3 ) 128 — A : '_.f,&.\ __A NOTE: : RISV NO. e PHiDOGH AETER MACHINING , THIS BISE€ SHALL MEED THE INSPECTION & s DrawING x0T DEGE" /| OF ORNL SPECIFICATIONS MET~NOT-3 (ILTRASONIC) AND MET-NDT-4 (LIQUID T, _GAYE _PENETRANT). i NATERIALAOLY W : : ACALR AUAL NyMRY nmm l—.“?' [ l I ‘. c" ' — — m Q S ® 5 bl £ Q 8 - £ o S &% ing as po wall 84 tion of INOR-8 tub side of pipe 2 : g3 « 2 4 @ s 8 it % B0 ,.F Inside of ‘Ul }000) L VE000] X005 | ‘w G000 1M 2000] v ¥ ] W 400’0 W E00'0] X00G | U GOO'O} w2000 = SIHONI 2000 — } _ J ‘ o~ SIHONI L0070 1 s diator. (a) ™~ o - - o ) > Y-101102 ing from the outlet end of the MSRE ra ished. wall, as pol 85 tion of INOR-8 tub ide of pipe al sec (b) outs m a tud. ia regi +* ngi with glycer ructures of a lo etched t . Micros ipe wall ig. 81 de of p F Insi ' i i i i | i i { i 86 Kig. 82. Asreceived INOR-8 tubing used in the MSRE radiator. Etched electrolytically in aqueous solution of 5% sodium citrate, 5% sodium acetate, 1% citric acid, 1% potassium thiocyanate. 600 mV, 1.5 mA for 15 sec plus 700 mV, 2.5 mA for 10 sec. (@) 250X ; (b) 1000X. 87 an. 83. Tubing from the inlet end of the MSRE INOR-8 radlator. Etched electrolytxcally in an agueous solution of 5% sodium citrate, §% sodium acetate, 1% citric acid, 1% potassmm thiocyanate. 700 mV for 10 sec, started at 8 mA and dropped to 4 mA. (a) 250X ; (p) 1000X. 1 = : = N T YA101190 1 ; AT Fig. 84. INOR-8 thermocouple well removed from the inlet line to the radiator of the MSRE. Much of the discoloration and the fragments of metal resulted from cutting the part out with a coated welding electrode. g i i { Fig. 85. Cross section of INOR-8 thermocouple well from the inlet line to the MSRE radiator. From left to right the components are the 5-in. coolant line, the weld, and the thermocouple well. The side having the most weld metal was exposed to air, and the other side was exposed to coolant salt. o -t -89 Table 10. Chemical analyses of sections Qf as-received : i INOR-8 radiator tubing - o U S . Silicon (%) ; -+ Carbon (%) " Inner 5 mils of wall 0.53 0.095 ~ Center 62 mils of wall 0.79 0.073 Outer § mils of wall - 079 0.036 Bulk composition 0.62°% 0.067 4Vendor analysis; others made at ORNL. Table 11. Tensile properties at 25°C of INOR-8 tubing from the outlet end of the MSRE heat exchanger and as-received material Yield Ultimate Fracture Reduction stress tensile strain, in (psi) stress(psi) %in2in. area (%) As received 63,500 123,100 52.0 44.1 Heat exchanger 64,600 123,800 38.8 29.5 Metallographic examination of the mounted cross section shown in Fig. 85 revealed that the weld had cracked on the salt side of the pipe. The cracks on both of the polished surfaces in Fig. 85 are shown in Fig. 86. In the worst case the cracks penetrated to a depth of about 3 mils. The remaining half of the well was cleaned by acid etching to remove the metal left from the cutting operation, and the weld was checked with dye penetrant. A photograph of the weld with dye still present is shown in Fig. 87. Note that the crack, as indicated by the dark color, extends almost completely around the weld. There is also an area where penetration of the root. pass was incomplete. We propose that the cracks formed as the weld was made, because of the poor fit-ip of the parts to be welded. The welds were not stress relieved, and the fact that the cracks did not penetrate further attests to the lack of stress and crevice COI‘l’OSlOIl by lithium-beryllium fluoride salts. _ ' ; We did not section the outlet well but we did clean the weld and examine it with dye penetrant. No cracks were observed. The outside surface of the S-in. ‘pipe was exposed to air and was ox1dlzed Figure 88 shows the spotty nature of the oxide and its maximum thickness of about 3 mils. A cross section from the bottom of the well was examined. A macroscoplc view of this section is shown m Fxg 89 The inside of the well was prepared by drlllmg, and the pointed shape of the drill is still apparent at the bottom The weld metal deposit on the bottom was made to ensure that salt did not leak along the carbide stringers. The amount of oxidation was greater at the bottom of the well than further up. The transition to the thinner oxide about % in. from the bottom is apparent in Fig. 89. Figure 90(a) shows the oxide layer of about 5 mils at the bottom of the well, and Fig. 90(b) shows the abrupt transition about %4 in. from the bottom. Since lubricant would have been used during drilling, we suggest that this difference may have been due to the bottom of the well not being as clean as the sides. ' A further significant observation was that the surfaces of the well exposed to the salt looked qu1te similar to those of survelllance samples removed from the MSRE (Fig. 91) We have previously attributed this modified surface structure to cold workmg from machining and have shown that it can be produced in the absence of salt. The structure likely results from carbide formmg on the slip bands produced by machmmg Thus there is no ev1dence of corrosion of this part. 20 Y-101 78 in 100X Jou Fig. 86. Cracks in the root pass of the inlet weld. The cracks occurred at the fusion line and likely resulted from the poor fit-up of the parts. As polished. M v-101474 Fig. 87. Underside (salt side) of half of the INOR-8 thermocouple well from the inlet line to the MSRE radiator. The part was acid etched and coated with dye penetrant. Note the indication of a crack around most of the weld and an incomplete root pass region. . 91 Y:101571 » f ) w I LI zlo ol2 " olz o &) | Y-101785] o , o lo ; £ " 8 =T i I Sl S8 . o 0-—- 3 <€ ) 8 : e ‘ £ I~ O © . 1ic Fig. 88. Oxide formed on the outside of the 5-in. INOR-8 coolant line. As polished. (a) 100X ; (b) 500X. i | i | ! | i | 92 Y-101579 Fig. 89. Cross section of the infet INOR-8 thermocouple well. The outside was exposed to coolant salt, and the inside contained the thermocouple in air. 8X; as polished. Summary of Observations The surfaces of the radiator (tubes and thermocouple wells) that were exposed to air formed a shallow adherent oxide, while the surfaces exposed to salt were clean and showed no evidence of corrosion, Two slight modifications of microstructure were noted. A shallow layer on the inside surface of the tubing etched more readily, and we attribute this to contamination of the tubing by fabrication lubricants. A structural modification near the surface of the machined thermocouple well was similar to that noted on surveillance specimens and is attributed to the effects of cold working on carbide precipitation. ' The cracked weld where the inlet thermocouple well was attached to the 5-in. pipe header likely resulted from poor fit of the parts during welding. The crack probably formed when the weld was being made, and it is encouraging that it did not propagate further during service. SUMMARY The Molten-Salt Reactor Experiment operated above 500°C for 30,807 hr and was filled with fuel salt for 21,040 hr. Operation of the system was never detained by materials problems, but the examination of INOR-8 and graphite surveillance samples during operation and several cornponents after operation resulted in several important observations. 1. Graphite exhibited excellent compatibility with the fuel salt. Machining marks and numbers were clearly visible, with no evidence of chemical interaction with the fuel salt. 2. The INOR-8 surveillance specimens clearly demonstrated a progressive decrease in the creep ductility with increasing fluence. The MSRE vessel did not become brittle enough to cause termination of operation, but an alloy with better resistance to embrittlement by neutron irradiation will be necessary for power reactors with a 30-year design lifetime. Considerable progress has been made in developing a modlficatlon of INOR-8 that contains 2% Ti and has improved resistance to embrittlement. 3s _35. M. W. Rosenthal et al., “Recent Progress in Molten-Salt Reactor Development,” Atomic Energy Review 9(3), 601-50 (September 1971). i 1 1 1 1 | ; i i ' i i i - - 93 Y-101575¢ __ 0.035 INCHES N 100X 1Y - 0.035 INCHES [ 100X T Flg. 90. Oxide inside the inlet INOR-8 thermocouple well As pohshed (@) At the bottom; (b) transition in depth about /3 in. from bottom of well. 94 Y-101573 Fig. 91. The outside of the inlet INOR-8 thermocouple well that was exposed to coolant salt. Note the modified layer near the outer surface. Etchant: glyceria regia. 3. The INOR-8 surveillance samples and components removed from the fuel salt were slightly discolored, but no evidence of corrosion could be detected by standard metallographic examination. The selective removal of chromium and iron from metal from the core was detectable by the electron microprobe. No composition gradients were detectable in metal from the coolant circuit. (The coolant salt did not contain uranium.) Thus the corrosion rate was very low in the fuel circuit, and this observation agrees well with the chemical changes observed in the fuel salt.®® 4. Some of the INOR-8 surfaces showed shallow microstructural modlficatlons One type involved increased carbide precipitation in a lamellar pattern and was likely due to cold working from machining. The second type was noted only on tubing and was likely due to carbon contamination from fabrication. Neither modification is thought to be of practical significance. 5. Grain-boundary embrittlement was noted on all INOR-8 surfaces exposed to fuel salt. The shallow intergranular cracks were often visible in polished sections of INOR-8 as removed from the MSRE. In most instances the material had to be strained to make the cracks visible. Cracking similar to that noted in the MSRE was produced in laboratory experiments by exposure of INOR-8 to the fission product tellurium.®? This experimental work has shown that the extent of cracking is very dependent on the alloy composition. 6. Freeze valve 105 failed from thermal fatigue due to nnproper construction and not from a basic materials problem. ' 36. R. E. Thoma, Chemical Aspects of MSRE Operation, ORNL-4658 (December 1971). 37. H. E. McCoy and B. McNabb, Intergranular Cracking of INOR-8 in the MSRE, ORNL-4829 (November 1972). 95 7. A crack was noted in the weld that attached the thermocouple well to the radiator coolant salt header. This crack was restricted to the root pass and was likely a result of poor fit-up of the parts. The crack probably formed when the weld was made and did not propagate during service. 8. Oxide films were formed on all the INOR-8 surfaces éprsed to air or the cell environment of nitrogen containing 2 to 5% Q,. The oxide generally consisted of a uniform surface layer about 1 mil thick and a selective oxidation front extending to a depth of 4 or § mils. This depth and type of oxidation are what would be expected for an alloy that contains only 7% Cr, such as INOR-8. 9. A copper sample capsule that had been in the fuel salt pump bowl for several thousand hours was very brittle. Chemical analysis showed that constituents of the fuel salt and INOR-8 had penetrated the copper, but the element responsible for the embrittlement was not identified. " ACKNOWLEDGMENT The observations in this report cover several years and include contributions from many individuals. W.H. Cook and A. Taboada designed the surveillance fixture, and W. H. Cook was responsible for its assembly and disassembly. The MSRE operations staff, headed by P. N. Haubenreich, exercised extreme care in handling the surveillance fixture and in removing the various components for examination. The Hot-Cell Operation Staff, headed by E. M. King, developed several special tools and techniques for various examinations and tests of materials from the MSRE. The metallography was performed by H. R. Tinch, E.H. Lee, N. M. Atchley, and E. R. Boyd. The microprobe scans were made by T. J. Henson and R. S. Crouse. The mechanical property tests were performed by B. C. Williams, H. W. Kline, J. W. Chumley, L. G. Rardon, and J. C. Feltner. The chemical analyses were performed under the supervision of W. R. Laing, E.I. Wyatt, and J. Carter. Assistance was received from several members of the Reactor Chemistry Division in several phases of this work. J. W. Koger, J. R. DiStefano, P. N. Haubenreich, and J. R. Weir reviewed the manuscript of this report and made many helpful suggestions. Kathy Gardner made the original drafts of this report, and the drawings were prepared by the Graphic Arts Department. s 3 (20) 3 Central Research Library ORNL — Y-12 Technical Library - Document Reference Section Laboratory Records Department Laboratory Records, ORNL R.C. ORNL Patent Office G. M. Adamson, Jr. C.F.Baes C. E. Bamberger R. Blumberg E. G. Bohlmann R. B. Briggs S. Cantor E. L. Compere . H. Cook Crowley Cunningham Haubenreich Hill Huntley ouye Kasten Wmsgwawsuchuuuu-flué . L. .L. .E. .M. .H. .R. .R. . E. .H. Flye Jr. .R. . H. .0. .N. .R. .R. .n .R. INTERNAL DISTRIBUTION ) (%) EXTERNAL DISTRIBUTION ORNL- -4174 J w L .N. Lyon . G. MacPherson . E. MacPherson .R. W] E L. E. McNeese A. S. Meyer R. B. Parker P. Patriarca A. M. Perry M. W. Rosenthal H. C. Savage Dunlap Scott J. L. Scott J. H. Shaffer G. M, Slaughter P. Smith A. Strehlow E. Thoma B. Trauger M. Weinberg R. Weir C. White V. G. R. R. D. A. J. J. L. V. Wilson BABCOCK & WILCOX COMPANY, P.O. Box 1260, Lynchburg, VA 24505 BLACK AND VEATCH, P.O. Box 8405, Kansas City, MO 64114 BRYON JACKSON PUMP, P.O. Box 2017, Los Angeles, CA 90054 B. Mong C. B. Deering G. C. Clasby 08 CABOT CORPORATION STELLITE DIVISION, 1020 Park Ave., Kokomo, IN 46901 T. K. Roche CONTINENTAL OIL COMPANY, Ponca City, OK 74601 J. A. Acciarri EBASCO SERVICES, INC., 2 Rector Street, New York, NY 10006 " D.R. deBoisblanc T. A. Flynn THE INTERNATIONAL NICKEL COMPANY, Huntington, WV 25720 J. M. Martin UNION CARBIDE CORPORATION, CARBON PRODUCTS DIVISION; 12900 Snow Road, Parma, OH 44130 R. M. Bushong USAEC, DIVISION OF REACTOR DEVELOPMENT AND TECHNOLOGY, Washmgton DC 20545 David Elias J.E.Fox Norton Haberman C. E. Johnson T. C. Reuther S. Rosen ~ Milton Shaw J. M. Simmons USAEC, DIVISION OF REGULATIONS, Washington, DC 20545 A. Giambusso USAEC, RDT SITE REPRESENTATIVES QOak Ridge National Laboratory, P.O. Box X, Oak Rldge TN 37830 D.F. Cope Kermit Laughon C. L. Matthews USAEC, OAK RIDGE OPERATIONS, P.O. Box E, Oék Ridge, TN 37830 Research and Technical Support Division USAEC, TECHNICAL INFORMATION CENTER, P.O. Box 62, Oak Ridge, TN 37830 (2