e OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION m NUCLEAR DIVISION for the U.S. ATOMIC ENERGY COMMISSION LDCI":HEE[.;I :-ua*.-.r_u ENERGY flESE_AH:HIUB_Hnm_gs- o RN L - T M B ] 907 [IIERARER YO 1 .|'.“| “ |.‘|| |‘ il ‘I‘ | |H COPY NO. - = 3 445k 0513418 2 paTE - July 21, 1967 CORROSION OF THE VOLATILITY PILOT PLANT INOR-8 DISSOLVER AFTER SEVEN COLD DISSOLUTION RUNS E. C. Moncrief A. P. Litman ABSTRACT The Volatility Pilot Plant dissolver vessel, based on ultrasonic thickness measurements, seems to be sustaining low corrosion losses. Wall thickness changes were measured for the Volatility Pilot Plant INOR-8 dissolver a fter 204 hours of exposure to anhydrous HF and equimolar NaF-LiF fused salt contain- ing 22-52 mole per cent ZrF at 495-655°C while Zircaloy-2 dummy fuel elements were being dissolved. Measurements were taken using the "Vidigage, " an ultrasonic thickness measuring device, first after an ammonium oxalate solution wash to dis- solve residual salt, and later after an HNO3-AI(NO3)5 rinse to remove any metallic deposits that might have formed. For the dissolver, maximum wall thickness losses were nofed in the vapor region where a maximum loss of 11 mils was found. This loss corresponds to 0.054 mils/hour, based on HF exposure time, or 17.0 mils/month, based on molten salt residence time. Lower losses occurred in the vapor-salt interface region, and still less in the salt region of the vessel. Bulk metal losses due to the use of the oxalate and nitric acid-aluminum nitrate solutions were considered negligible. OAK RIDGE NATIONAL LABORATORY CENTRAL RESEARCH LIBRARY DOCUMENT COLLECTION LIBRARY LOAN COPY DO NOT TRANSFER TO ANOTHER PERSON If you wish someone else to see this document, send in nome with document and the library will arrange a loan. 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The Volatility Pilot Plant has.curréntiy completed a series of seven cold dissolution runs using Zircaloy-2 dummy fuel elements according to the head-end procedure of the fused salt Volatility Process. - .These runs were designed to evaluate the HF dissolution step of the Volatility Proc- €sS. - N A necessary part of that evaluation was the determination of the corrosion losses occurring on INOR-8, the material of construction for the dissolvef vessel Table I summarizes the corrosion rate losses nominal composition of INOR-8 is Ni: 71 wt %, Cr: and Mo: 16 wt %. runs and indicates that equimolar NaF-LiF fused salt containing 22-52 "The 7wt %, Fe: 5wt b, - Table II details the process conditions for the seven mole per cent Zth.waa used at temperatures of 495-655°C along with 1160 kg of anhydrous HF to dissolve eight dummy fuel elements schematic of the hydrofluorination operation. 'Figure 1 shows a Wall thickness measurements were made prior to the development runs and twice after run T-7 using an ultrasonic thickness measuring device, the "Vidigage." The first measurement after run T-7 followed a Wl hr wash with boiling 0.35 M ammonium oxalate solution; and the second measure- ment followed a 10 hr rinse with boiling 5 wt % HNO v 3-5 wt % AL(NO oxalate wash served to remove residual fused salt while the HNO solver walls during fuel element dissolution. . Th 3)(3 © )., ~AL{NO | 3" 3) rinse dissolved any metallic deposits which might have formed on the dis- 3 . Figures 2, 3, and 4 present the data obtained and show that measurements were made at 90 _ ° intervals . around the circumference of the dissolver at three inch height increment The present operating orientation of the dissolver vessel is also indicated Although a restricted number of readings were taken on the top cylindrical section of the dissolver because of thé presence of insulation, sufficient data were collected to indicate that the vessel had lost an average of 9.3 mils on the inside diameter of that section (see Fig. 2) 1g. I. Cathers, "Fluoride Volatility Process for High Alloy Fuels,” ORNL-CF-57-4-95, Presented at Symposium on Chemlcal Proce551ng, Brussels, Belgium, May 20-25, 1957 ru 1 w““ii\i\\"ii\“\\\\'i\iii\ii\ii\\iii\i\‘\\ii\i\ifi\i\i\i\i\i Il | N e 3 - This loss cbrresponds to 0.045 mils/hr, based on HF exposure time. The top section was exposed only to the process vapors except for occasional salt splash. However, for comparative purposes, an average rate loss figure of 14.4 mils/month, based on molten salt residence time was also calculated, The maximum wall thickness loss in the vapor region of the dissolver, 1l mils, did not deviate greatly from the average quoted. The conical section of the hydrofluorination vessel was exposed to - " both process vapors and fluoride salts during the runs described. In run T-7 the salt level was in the conical section; in all other runs salt contact was from splash. The average wall thickness loss found for this section was 4.2 mils, less than the 1% accuracy of the "Vidigage" instru- ment, although a maximum of 10 mils loss was noted at one point (see Fig. 3). Maximum rate losses were 0.0M9 mils/hr, based on HF exposure 4time or 15.4 mils/month, based on molten salt residence time, The bottom section of the dissolver consists of five cylinders of 5-1/2 inches inside diameter and varying length joined by circumferential welds'to form a right cylinder 9 feet in height. Thickness measurements of this section did not disclose significant bulk metal loss (see Fig. 4). However, two areas in the west quadrant did register unusual hlgh and low - thickness changes. These 1rregular1t1es may be due to inaccuracies in the ' base~line data collected on the dissolver vessel. Excludlng the high and low data -mentioned, a maximum loss of 6 mils was found for the bottom section, Comparison of the thickness Jata before and after the nitric acid- aluminum nitrate rinse (Figs. 2, 3, and 4) ihdicated that negligible changes occurred outside the accuracy of the "Vidigage" instrument. The Volatility Pilot Plant dissolver vessel, based on ultrasonic thickness measurements, seems to be sustaining low corrosion losses. ECM:1j - o o e Table I. Summary of Corrosion Rate Losses on Volatility Pilot Plant INOR-8 Hydrofluorinator after Seven Runs Corrosion Rate S . a ‘e b Region ' Mils/hr . _ Mils/mo Dissolver - Average Maximum - Average: Maximum - Top - 0.0k45 0.05k 14,4 17.0 Cone ' 0.021 . 0.0k49 - 6.5 15.4 "Bottom . . 0.003 . 0.05h 1 17.0 ®Based on HF exposure time of 204 hr. bBased on molten salt residence time of 465 hr. E . T ot N S - a.-, - » 3\ “ Table II. Summary of Zircaloy-2 Dissolution Runs in the Volatility Pilot Plant ‘ - . : | Zircaloy-2 HF F?;ziésélfiagfgfgfgiéo?’ Saltogemp" HF Dissolution Utilization : b, Rate; Time, Rate, (Over-all Run No. Initial Final . Max Min (g/min) (hr) (mg/cm®-min) Average) T-1 h2.8-21.7-35,5 30.9-17.3-51.8 560 520 104 38.0 - 0.60 : 15.0' - T2 38.3-30.1-31.6 30.2-26.8-42.9 530 525 Lo 41.5 " 0.l9 23.4 T-3 38.8-38.8-22.4 31.4-25.9-42.7 625 550 90 2.7 | 1.01 23.2 T-4 -37.3-37.3-25;3 29.3-27.3-&3.3 630 1495 90 22.5 1.01. 22.3 T-5 37.5-37.5-25.0 27.h-27.Lh-L5.2%% 625 530 ° 90 27.2 0.85 18.4 T-6 37.5-37.5-25.0 30.7-30.7-38.5%% 650 500 150% 25.7 0.87 ©11.3 T-7+ 36.9-36.9-26.3 25,.3-25.3-49.4%% 655 523 135 23.0 0.97 27.8 ¥HF rate 118 g/min (avg) first 8.5 hr; 160 g/min thereafter. . + - b | a ) Two elements dissolved during run - #%Theoretical value (analyses of final salt not available to date). —= : UNCLASSIFIED o : ' . ' " ORNL-LR-Dwg. 53572 FV-1500 " 1 ,— FV-8501 Slug Carrler-Charger Barren Salt - - ' Trons{er Tan . ::. = i ' ‘.:. vy et c_' * B A HCV-1000-2 /Ccr:\:rct;er ¢ ute Oft Sas HCV+1000-| ' o - FVy-2004 HF Cooler . ‘ : z— FV-1000 N 3 ._ 1. Dissolver Freeze Volvel FV-2005 HF Condenser ' ! | Zev-100 _ /__- : o N ‘ | * Fluorinator . : A v . _ a /S Waste Can _ - s - - aw b s mn o= - \—'/ | FV-1006 — - . HF Accumu- - ©8alt to FV-100 ' FV-1009 . lator . and waste Coustlc Neutralizer s ' - b ' _ HF D ' Q FV-4200 . FV-1207 Milton Ro -HF Vapor Generator Remote Head Y’ump Fig. . Schematic Diagram of Hydrofluorinafion Operation. /"‘,v' < ORNL-LR-DWG. 54469 A . (North) UNCLASSIFIED 1. Total HF time, 204 hr 2. BReadings taken on 1ineibeneath letters every three inches. - 3. Dissolver cleaned with boiling 0.35 M ammonium oxalate solution for 41 hr; boiling 5 wt % HNO3 5 wt % AL{NO ) .for 10 hr. { (South) Insulatiofl ¢ < 3 4 on 1] § £ | Oh 5-1/2 in. . dia 2 | / _J -9~ DNCLASSIFIED _ ~ ORNL-LR-DYG. 54471 1. Total HF time, 204 hr. ' . 2. Readings taken on line beneath letters - every three -inches. 3., Dissolver cleaned with boilihg 0.35 M ammonium oxalate solution for 41 hr; boiling 5 wt %lHHO3-5'wt % Al(N03)3 for 10 hr. Readings in Mlls _ (Accuracy ~+ 1% of Materisl Thickness) Change in Wall Thickness After Oxalate After HNO3-A1(NO3) 4 Average JReadings jevery 3 ~iinches ) | U Botthm Section (Nominal /% in. Thick) FV-1000 VPP Dissolver " Fig. 4. 'A_ B C 1D A B C D | Change - | - - |- =2t =37 =Lkp -l ~3 | -3] 6] -3 [ -3] 3] -5 -2 : -3:> 3| -2} b2} b} -3) b} 51 -3.h =2 | b b3 b -5) =30 5| -3 3.6 A1 | -k -2l a2} 5] Wb L} a2 ~3.0 01 «31 ~«2] -k § 0] =3{ +Ly O -l.k 31 +1 =31 =31 =3 +1] =3 Ol 41| ~l.1 il +3 4} L} -l +1 | ~3| 1] +1 +0.6 4] 0| 41| ~L| © O] O] <1} =1 =0.3 #L | 41| =1| -k ol +2] +1| -1 =0.1 0 O ~3{ -2 [ 41| +1| +1| =2 -0.5 41 | +2 “3 =1 0 +1 0 -2 «0.3 0 Of «1] O -1 O +L| =2 0.4 0 +1 ! -2 o 1| -1} o} -2 -0.6 0 | 42| -2| -1 O 41| 41] =1} O +1 0| -1 O ! 41| +2]| +1{ 41 +0.6 +1. 0} ~2| © +1| +2 0 0 +0.3 0 +1, O -k +1] +2| +#1] -1 0 O | =6 =1| -2 | -1| -6 +41] +1| -1.8 41 | . =T] ~1| -2} +1| -8 o +1 -1.8 +2 -1l +1 0 +2 -7 +1 +1 -1,k +1 |7 0| «3| =2 1 42| +1 1| 41 -0.1 +2- 0 o} -4 41| 0 0 0 -0.1 42 +10| -1]| «3- 0| 49| =1 0 +2.0 +1. +10| +1{ -2 0| +1q 4+ 0 +2.6 +2 | +10] -1| -1 +1| 8 0] +1 +2.5 +1 +3 ] 4| =3 +2] +2] -2 0] =-0.1 +2 41| -3} -2 +1 o} =L} =1] -0.h +1 +1 | -2 -k 0 0] =~L| =1 -0.8 w2 | 2| b -2 +2] 0] -2| -0 -0.3 +2 +1 ~-51 -3 +1| .+2 -2 0 ~0.5 -1 -2 | «1l] -2 +1] O]