e ety e — i 1 . e St . 1 » 5 Contract No, W=7405-eng-26 REACTOR PROJECTS DIVISION MEASUREMENTS THROUGH A HOT CELL WINDOW USING OPTICAL TOOLING A. A. Abbatiello DATE ISSUED APR 2 3 1958 .. OAK RIDGE NATIONAL LABORATORY o Ock Ridge, Tennessee operated by UNION CARBIDE CORPORATION for the U.5. ATOMIC ENERGY COMMISSION ORNL-2658 vy 1 MEASUREMENTS THROUGH A HOT CELL WINDOW USING OPTICAL TOOLING! A. A, Abbatiello ABSTRACT . Optical tooling was evaluated for the measurement of physical dimensions of radicactive parts through hot cell windows. Instruments were set up outside a 4-ft-thick lead-gloss window. Al- though the window was not specially selected, the readings were within 1.0% of the true dimension. Use of a calibration chart of the window variations reduced the error to 10.1%. The method is considered feasible and sufficiently fast for @ wide range of hot cell measurements., of the window's measurement qualities. The reflections of a point light source from the lead-glass laminae form @ convenient indicator } INTRODUCTION The dimensional measurement of irradiated parts has become one of the problems connected with reactor development, These measurements are important to determine strain, creep, and metal- lurgical changes in parts which have become radio- active and therefore inaccessible to ordinary measuring tools. A number of measurement methods . have been considered, one of which is optical tooling working through hot cell windows. The principal advantages of this system are: (1) parts . may be measured without direct contact or con- tamination, (2) convenient and comfortable working areas can be utilized, (3) the cell interior is entirely free for useful working space, and (4) ac- ceptable accuracy "is attainable. Essentially, optical tooling is measurement by means of o telescope (called a transit square) which is capable of moving in horizontal “and vertical directions (Fig. ‘1). It is referenced from an independent optical control line and may be aligned with the object point located in space, Direct recdings taken from a vernier scale mounted on the carriage are subtracted to obtain the net distance between two points. In the cases where measurements are made through windows, a calibration - factor for . optical distortion is then applied to obtain a cor- rect reuding.'."Optifi:dl"tooli‘hg? has been in use in ‘Prepared for the 7th Hot Cell Conference. 2 W. L. Egy, ‘‘Optical Toeoling,'” The Tool Engr. (April 1955). ¢ aircraft plants for years and is now being applied in other industries requiring accurate location of widely separated points, as on large assembly iigs, heavy machinery fabrication, and shipbuilding. The purpose of this test was to determine the feasibility of taking accurate measurements with an optical tooling system through a 4-ft-thick lead- glass window. The locations and the effect on the readings of optical defects in the window were desired as well as the time required to take typical measurements, Optical tooling instruments were set up in front of a new 4-ft-thick hot cell window. Although this window was selected mainly because it was avail- able, its optical properties proved adequate for an acceptable range of accuracy. By calibrating a specific window, the accuracy can be further in- creased by applying the correction factors which are determined by test. ' DESCRIPTION Measurement by the use of optical tooling re- quires that the points on the object to be measured be visible in o direction perpendicular to the win- ~dow syrface thrb(:gh which it is viewed, and that it be possible to turn the object so that the points lie in a plane paraliel to the window. A cell _gfiuipped with a lift and turntable would be most useful for the larger parts which would be en- countered in a typical reactor program, Smaller parts might be adequately handied by manipulators, or merely set up in front of the window aend prop- erly oriented. - ALIGNMENT TELEsc07 TOOLING BAR TO OBTAIN DIMENSION "X" TAXE TWO VERNIER READINGS AND SUBTRACT. UNCLASSIFIED ORNL-LR-DWG 34274 Fig. 1. Optical Tooling Principles. In order to provide the necessary range of meas- urement, a transit-type instrument is held in a plumb position and perpendicular to the window surface, as shown in Fig. 2. Mechanical means are provided to move the instrument in horizontal and vertical directions to cover the complete window area. An alignment scope generates a reference line to which the 20-power transit scope is set perpendicularly at the vertical plane and elevation of interest. - An,obticclly flat mirror, magnetically held on a steel optical flat mounted on the wall at the side of the window, provides the vertical reference ‘plane. from which the transit square and alignment scope are positioned. This system is used to establish a horizontal plane at each new elevation . (see Fig, 2). Fundamental Steps of Alignment The following describes the basic steps in setting up this optical tooling system: 1. The tooling bar is positioned parallel to the front of the hot cell window in a convenient loca- tion. The transit scope and alignment scope are set respectively 90° from and parallel to the win- dow (Fig. 2). . 2. The optically flat mirror mounting bar (straight- edge) is placed in a vertical position beside the: window and adjusted parallel with its front surface, The optical mirror is held magnetically to the optical flat, - | o 3. The transit scope is aligned perpendicular to the plane of the optical flat {Fig. 3). 4, Without disturbing the previous setup, the’ alignment scope is positioned from the fransit - * C .y STEEL OPTICAL T ALIGNMENT TELESCOPE TOOLING BAR VERTICAL SCALE ._ : : a , N Yo/ ot ceLt UNCLASSIFIED ORNL-LR-DWG 34275 WINDOW PRECISION LEVEL LEVELING . ELEVATING GEAR Fig. 2. Onficdl Tooling for Hot Cell Test. - scope and udiusted to bring it square by means 'of - the built-in transit scope mirror, thus providing a fixed reference line parallel to the front of the ~window. This - control reference line is- ‘then available for cll subsequent mecsurements at thuf, o " level, : ' : 5, The transn square is moved to the flrst position and aligned (Fig. 4). 6. The transit square is aligned with the part (Fig. 5) and the vernier is read, 7. The transit square is moved to the second posmon, allgned and read, ;8._,,A_; change to unother elevation is made by repositioning the magnetically mounted wall mirror B '(Fig'.' 2) along the steel optical flat, and repeating - the - perpendicular setting of the transit scope to this mirror. The alignment scope is then raised and positioned from the transit scope, thus estab- lishing a new reference line in a plane parallel to Fig. 3. Tronsit Square Is Set with Opiicu"y Fliat Reference Surfuée. UNCLASSIFIED PHOTQ 414763 Fig. 4. Transit Square Is Adjusted Perpendicular to the Alignment Scopg. o UNCL ASSIFIED PHOTO 41764 « Fig. 5. Truns!t Square Is Aligned with Grid Plate. UNCLASSIFIED PHOTO 41765 " the front of the window, and at the elevation de- sired for the new set of measurements. Equipment Requii‘é& L Commercially available optical tooling equip- ment was set up for evaluation under practical hot cell conditions. Vertical measurement was impro- vised using a vertical height gage and a precision level (Fig. 6). In a typical hot cell envisioned, the test arrangement would be replaced with a combination tooling bar as sketched in Fig. 2, The purpose of the combination tooling bar is to provide easier manipulation in the vertical plane than is available with the standard tooling bar. It has been estimated that the combination tooling bar and all the associated equipment for one com- plete setup would cost about $6000, GENERAL PROCEDURE System evaluation was done by setting up the instruments at the hot cell window and taking - readings of an accurately scribed plate at three locations: (1) outside the cell, (2) with the plate hung just inside the cell (to determine the wedge displacement of the window), and (3) repeating the readings with the plate at the most distant (about 9 f1) portion of the cell, to get the maximum angular deviation, ' Typical Example of Measuring a Part - A cylinder was placed in the cell ot a point about 5 ft back from the cell window, and the diameter was recorded using. the optical tooling instruments, Table 1 shows a first and a second try, with the cylinder moved to o new position for the second test in order to view through a different portion of the window. The cylinder was 6,800 + 0,002 .in.,-in diameter and had @ shiny surface, which was not considered the ideal for best accu- racy, but was used as an example of practical system evaluation, A view of a part inside the cell is shown in Fig. 7, DISCUSSION Although the instruments may appear complex, they were surprisingly easy to operate, During the calibration of the cell window, the complete cycle of raising the tooling bar, precise leveling, squaring with the optical wall mirror, taking 18 sets of readings on the horizontal scale using the transit square, and also toking 18 corresponding points vertically with the optical micrometer attach- ment were made in about 1 hr. Operators were trained rapidly in the use of these instruments, During the course of this test, four different assistonts were used, some for as little as one day, and each was able to learn the technique and The reproducibility of the results was determined by taking a set of readings along the same hori- zontal line on three different occasions when the instruments had been removed and replaced. These data, plotted in Fig. 8, show a dispersion of about 0.030 in, for length measurements of 20 to 30 in., which indicates a reproducibility of about 10.1%. - Further improvement probably could be obtained by using a more permanent setup with refinements -such as floor plates having dowel bushings mounted in the floor. This would have the added advantage of making it easy to remove the instry- “ments” for use at other installations, or to free " Table 1. Measurement of a Cylinder : :Fir'st Try Second Try Right side of cylinder, vernier reading, in. .~ 48.959 44.488 " Left side of cylinder, vernier reading, in. 42,160 | 37.664 . ,Differqnce{ '(éylindér ;Vlii',.nm;eter zfilllc'ortect'ed.), in, 7 6.799 6.824 ' _B-eéd-’.a:.s'q.-.:th'i..r_;_'obiec'f'w,u."_srot' 5 ft, _u#@‘/z -cdrr_ecfiqn : -0.022 | —0.018 - (from a Vf_ub'le_pr‘epoired‘.for this winde);-_ i_h; : ’ : Cdrriec'féd_dirarhe‘tér, )i'rrs. | 6777 | 6.806 Accuracy 6.777/6.800 = 99.7% 6.800/6.806 = 99.9% UNCLASSIFIED PHOTO 41862 'Fig. 6. Data Taken Using Vernier Height Gage, Precision Level, and Optical Micrometer, S 5 | PHOTO 41864 'Fig. 7. Measurement of a Part Inside Cell. NOTE: UNCLASSIFIED ORNL~-LR-DWG 34276 THE INSTRUMENTS HAD BEEN REMOVED AND REPLACED EACH DAY GRID PLATE WAS 9ft 9in. BACK OF CELL WINDOW 2 0.250 , — w o . ‘ B 2 © 0.200 | Z A OCT 4. A/?? o O OCT 7. A . u b w 0450 I~ ¢ ocT 9 - a w ‘ ‘ — > 0.100 > 0.050 == 2 0. 3 | o Az . | o a 8 12 16 . 20 24 28 32 DISTANCE ALONG WINDOW AT LOWEST VISIBLE LINE (in.) Fig. 8. Window'Calib_rution.‘ the window when other work is in progress, Work- ing area may be provided directly .in front of the window without interfering with the optical tooling, since the distance over which the instruments operate may -be increased considerably without appreciable loss of accuracy. A permanently mounted optical flat at the side of the window would aid in maintaining a common reference plane as the basic starting point. No special effort was made to use a selected window; the one tested merely happened to be available, and therefore high optical accuracy was not expected. It is of interest to note that a pin- point light source revealed noticeable variations, although the window is of acceptable accuracy. If all laminae have parallel surfaces and are assembled into a paraliel pack, the light-source images would lie in o straight line when viewed from any position. The use of a simple light source appears useful as an aid when assembling windows, because the alignment of each lamina could be checked easily as it is being placed. .~ SUMMARY 1. The method proposed for linear measurements through hot cell windows is considered feasible on 10 the basis of the equipment and methods used in a hot cell test at ORNL, Views of the components in use are shown in Figs. 3, 4, and 5, 2. The accuracy of measurements taken through this particular window without correction is about 99% and 99.87% respectively for readings taken 93/4 ft and 6 in. inside the cell window. 3. By using the calibration chart produced for this window during the test (Fig. 8), accuracy can be improved to about 99.9% (or 10.1% variation) - for long cell distances, which approaches the practical accuracy of routine shop measurements in non-radioactive work using conventional methods, As the work is brought closer to the window, errors are proportionately reduced. | 4., The speed and accuracy of taking measure- ments is high for hot cell work. It may be com- pared to typical experience using a cathetometer or a sutface plate and vernier height gage. 5. A pin-point light reflection test is a simple method to evaluate a window for potential accu- racy, and might be developed further to assist the manufacturer in selectively assembling glass sections for best precision, ' 6. A zinc bromide or other liquid-filled window, having the minimum humber of light-refracting sur- faces, would be preferred for measuring purposes. C -} el “Since optical tooling is used perpendicular to the viewing surface, chromatic aberration is not a problem. Because of the lower density of zinc bromide, however, greater thickness would be necessary to obtain equivalent shielding. 7. Operators can be rapidly trained in the use of these instruments, 8. Hot cells planned for accurate parts meas- urements could use this measuring system by calibrating a window or selecting one with suit- able properties. ACKNOWLEDGMENTS The assistance of W. W. Alto, Chief Engineer of the Brunson Instrument Company, is acknowl- edged for the contribution of the idea of an opti- cally flat reference surface from which to align the transit scope for different elevations. A. N. Brunson, President of the Brunson {nstrument Company, Kansas City, Missouri, provided the instruments which were loaned for this test, The assistance of R. J. DeBakker in setting up the equipment is acknowledged, as well as the cooperation of D. E. Ferguson and C, P. Johnston for the use of the cell. Credit is also due to T. E. Crabtree, H. W. Hoover, C. K. McGlothlan, and J. J. Platz for help in operating the equipment and taking daota, The complete review of this report and the many helpful comments of D. B. Trauger are gratefully acknowledged; also, the assistance and encourage- ment of M. Bender, W. F. Boudreau, and F. R. McQuilkin are appreciated. 1 INTERNAL DISTRIBUTION - 1. C. E. Center 67. 2. Biology Library 68. . 3. Health Physics Library 9. 4-5. Central Research Library 70. 6. Reactor Experimental 71. Engineering Library 72. - 7=26. Laboratory Records Department 73. 27. Laboratory Records, ORNL R.C. 74. 28. A. M. Weinberg 75. 29. L. B. Emlet (K-25) 76. 30. J. P. Murray (Y-12) 77. 31. J. A. Swartout 78. 32-36. A. A. Abbatiello 79. 37. S. E. Beall 80. 38. M. Bender 81. 39. D. S. Billington 82. 40. E. P. Blizard 83. 41. A.L.Boch 84. 42, C. J. Borkowski 85. 43. W. F. Boudreau 86. 44. G. E. Boyd 87. 45. E. J. Breeding 88. 46. R. B. Briggs 89. 47. W. E. Browning 90. 48. R. S. Carlsmith 9. 49. R. A, Charpie . 92, 50. R. Clark 93. 51. W. B. Cotirell 94. 52. G. A. Cristy 95. - 53. F. L. Culler 9. 54. R. J. DeBakker 97. . 55. S. E. Dismuke R ¢ 56. H. G. Duggan 99. 57. D.E. Ferguson . 100. 58. W. F. Ferguson g 101.- 59. A. P. Fraas 102, 60. E. A. Franco-Ferreira - 103, 61. E. J. Frederick 104. ' 62.- J. H Frye, Jr. 105. 63. W.R. Grimes 106, 64. E.Guth - 107, 65. C.S. Harrill - 108. - 66, W. R. Harwell 109. EX TERNAL DIS TRIBUTION 110. Dmsmn of Resecrrch und Deve |opment, AEC ORO 1”-633. Given distribution as shown in TID-4500 (14th ed.) under Instruments category H. A. A, C. w. G. C. M. J. R. R. M. H. W. E. J. F. A. K. G. M. A. P. A. E. P. F. A H A H R E 0. M. A. E. D. C. G. ORNL.2658 Instruments TiD-4500 (14th ed.) W. Hoffman Hollaender S. Householder P. Johnston . Jordan . Keilholtz . Keim . Kelley . Lane . Lindaver Livingston Lundin . MacPhetson . Manly R. Mann R. McNally R. McQuilkin J. Miller Z, Morgan Morris L. Nelson R. Olsen Patriarca M. Perry E. Pierce M. Reyling Ring, Jr. DO wpP—4 V=T . F. Rupp . W. Savage . W. Savolainen . E. Seagren . P. Shields . D. Shipley Sisman J. Skinner H. Snell H. Taylor - B. Trauger D. Watson D. Whitman - G. C. Williams - C. E. Vinters - ORNL ~ Y-12 Technical Library, Document Reference Section