biological problems. Users of tracer nicthods in the study and development of new pharmaceuticals will find more than the surprisingly small use that has been made of them so far, aiid no one can doubt that tracers can contribute much more usefully to diagnostic medicine than they yet have done. Applications so far have been fairly simple in character, and the possibilities inherent in such experiments as those a t the University of California Radiation Laboratory ( 5 ) have yet to be developed. Such developments are likely to make use of tritium and other cheaper and short-lived isotopes, wherever possible, rather than carbon-14. I n the study of chemical reaction mechanisms the uses of tracers are unique but limited, but in prepsratire chemistry gencrally the facility of analysis by tracer methods is so great that nonessential uses in the study of reaction yields and by-products will certainly increase when chemists generally are more familiar with the possibilities and have overcome some of their inhibitions about radioactive tracers. In normal analytical practice progress in using this new tool to advantage n-ill again depend on the enterprise of analytical chemists, who will need to acquire a realistic grasp of what tracers can aiid cannot do as a preliminary to finding more analytical problems nliich their unique powers can solve.
(4) Bacher, F. A., Boley, 8. E., Shonk, C. Z., ANAL. CHEJI. 26, 1146 f 1954). (5) Biker, E. M., Tolbert, B. &I., Rfarcus, M., Proc. SOC.Ezptl. Biol. Med. 88, 383 (1955). (6) Berson, S. A,, Yalow, R. S., Volk, J . Lab. Clin. X e d . 49, 331 B. i\’.. (1957). Boos, R. N., Jones, S. I,., Trenner, X. R., ANAL. CHEX. 28, 387 (1956). Brown, E. V., Cerwonka, E., Anderson, R. C., J . i l m . Chem. Soc. 73,3735 (1951). Burtle. J. G.. Rvan. J. P., AXAL. CHEif. 27. 1215-11d55 (10) Calvin, >I.,’ and bthers, “Isotopic Carbon,” Wilev, Kew York, 1949. (11) Catch, -tical chemistry of high level samples is complicated not only by high radiation levels but also by the effect of the fission products as interferences in analytical methods. Tn general, highly radioactive samples are processed by dilution of sample, separation oft desired constituent, remote analysis, or in-line analysis. Dilution of Sample. The simplest plan of analyzing radioactive samples is based on cutting off a small amount of solid sample or diluting a sniall volume of liquid sample, then transferring and analyzing aliquots of below tolerance activity level on the open bench. The only shielded or remote apparatus required is some type of nicchanical cutting or coring apparatus or pipetter and a transfer mechanism. This dilution technique is commonly used for radiochemical analyses. Outside of this, the technique is limited to ions for which sensitive methods are available. Separation of Desired Constituent. The next simplest way nith regard to apparatus is to separate the constituent to be analyzed from the radioisotopes. High accuracy requires quantitative separation-a difficult task in view of the complexity of the chemistry of the fission products. This technique has been essentially limited to ion exchange and liquid-liquid extraction for separation of thorium, uranium, and plutonium. This technique costs more than the dilution technique, because of initial outlay and maintenance of the shielded or remote scparation apparatus. Remote Analysis. T h e technique of confining the entire analytical procedure t o a shielded enclosure is termed “remote analysis.” Enclosures run the gamut from a lead brick barricade in a hood with a simple tong to a cell
Figure 1 .
Atomics International hot cell
vith thick concrete walls, viewing xindow, and elaborate manipulators. T o be economically feasible, the high initial cost of such installations must be offset by increased production, reduction of radiation hazard, and improved accuracy obtained with niacrosamples. In-Line Analysis. The ultimate goal for the analysis of highly radioactive streams is in-line process control. The petroleum industry, one of the largest and oldest in chemical technology, is perhaps the farthest advanced in this new field. Application of this technique to plants processing radioactive material is made difficult by the nenness and complexity of the processes and because equipment must be virtually maintenance-free. In spite of these difficulties, the advantages are so great that several Atomic Energy Commis4on installations are engaged in active research and development programs in this field. FACILITIES
General Design Considerations. The very purposc of high level analytical facilities-to protect the analyst from radiation exposure-demands specially designed adequate shielding. Lead, cast iron, ordinary concrete. high-density concrete, high-density glass. and zinc bromide solution are all used. The latter tiTo serve as material for viewing n indows. Ingestion of activity, particularly through the respiratory tract, is particularly damaging. The flow pattern of air from personnel areas to shielded enclosures maintained by pressure control is universally used. Filters and other devices such as scrubbing towers
trap particulate niatter before release into the atmosphere. The specific design of a high level facility is governed by the types and frequencies of analyses, and vhether for a research installation or production plant, This latter classification has given rise to tn-o types of analytical facilities, the “versatile” group and the “specialized” group. Versatile Type, designed to provide analytical service for research installations. It must be able to handle a wide variety of work, with rapid change-over from one analytical procedure t o another. Conventional laboratory equipment is used, for which master slave manipulators are particularly well suited. Specialized Type, for routine process control in production plants handling radioactive materials. The facility is characterizpd hy specialized apparatus for each analytical procedure, designed to relieve the analyst of tedious or difficult operations. Simple tonglike manipulators, less rxpensive than master slave manipulators, are most often used. The conimercial type of tong manipulator is not designed for shielding thicaknesses of more than several inches; hrnce lead and cast iron are the shielding material instead of cnncrete. VERSATILE LABORATORIES
Hot Cell for Pyroprocessing Experiments [Atomirs International). This facility, located in Caiioga Pal k , Calif., is described fully by Foltz, Gardner. and Rosen ( 7 ) . One purpose of the cell is to obtain sniall representative portions of solid samples and prepare them for unshielded anal! sis. This characterizrs it as a ‘,dilution of sample” facility. Duplicate cells are 4 feet deep, 6 fwt VOL. 2 9 , NO. 12, DECEMBER 1957
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long, and 6 feet high (Figure 1). The exterior walls are 27 inches thick, made of high density concrete blocks. In each cell is a composition viewing window (high-density glass and zinc hromide solution) and two master slavetype manipulators. The cell air is changed about five times per hour, with both incoming and outgoing air filtered. Figure 2 shows the cell interior after installation of equipment. Of special interest are the secondary enclosures of Lucite which confine contamination. High Radiation Level Analytical Facility (Oak Ridge National Laboratory). This fa,cility for remote analysis, described by Frederick (Q), consists of a line of eight cells, seven of which serve as work cells, the other as a centrally located sample storage cell (Figure 3). Each work cell measures 6 feet wide by 5 feet deep; the storage cell is somewhat larger. Shielding is provided in general by 3 feet of concrete. Barytes concrete, a special high-density concrete, is used for the front face of the work cells, where recesses are provided for various purposes. The storage cell is constructed entirely of this high-density concrete. The Viewing window in the storage cell is of cerium stabilized glass; the work cell windows are of the zinc bromide solution type. Ventilation is handled in the conventional manner, with air flow progressing from uncontaminated to contaminated areas. Transfer between cells is provided by two conveyors, each serving the storage cell and one bank of work cells. Supplies and reagents from the operating area are introduced through transfer drawers in the front face of each cell. Entrance to the work cells is through rolling doors a t the rear of the cells, of concrete block construction with integral dollies for moving them. Figure 4 shows many of the above fea,tures. The position of the masterslave manipulators can also be seen in Figure 5. Two manipulators are provided for each cell except the storage cell, which has one. Controls and instruments are grouped around the operating face of each cell.
Figure 2. Interior of Atomics International hot cell with equipment
Figure 3. Plan view of ORNL hig.. laboratory
.-.-, -...-..,..--.
SPECIALIZED LABORATORIES
Six-Inch Lead Shield Facility (University of California Radiation Laboratory). The UCRL facility (10) is designed to serve primarily a separations process concerned with preparing samples of irradiated materials for analysis. The process is carried out in three boxes, positioned behind G i c h lead shielding (Figure 6). At each box position is a high-density glass viewing window and a pair of “castle”-type manipulators. In the ventilation system are scrubbers and condensers to remove contaminants from the air. 1732
ANALYTICAL CHEMISTRY
Figure 4.
Section through ORNL work cell
Figure 5. Operating face of ORNL high level analytical laboratory
Figure 6. UCRL 6-inch lead shield facility
Materials are transferred between boxes by means of interconnecting doors. Each box is outfitted for specific functions such as dissolution, centrifugation, and ion exchange separation. After the desired constituent has been isolated, it is removed from the facility for further work. The analysis may be completed in a junior cave with 2 inches of lead shielding (Figure 7), 8 “piano”-type glove box (Figure S), or even the open bench. Remote Analytical Facility (Idaho Chemical Processing Plant). This laboratory (4) is designed for routine process control analysis of highly radioactive process samples for the Chemical Processing Plant. The facility consists of two parallel lines of 16 boxes each, shielded by 9 inches of Meehanite (a high-carbon cast iron). Each box POsition is equipped with two castle manipulators, a lead glass viewing window, and utility supply connections (Figure 9). The basic features are patterned after the UCRL facility (10). Samples, reagents, and supplies are introduced into the head end of the lines through shielded doors or through dumbwaiters. The latter connect the lines to a conventional laboratory on the second floor. Dry waste is stored a t the far ends of the lines. Transfer between boxes is by an electric dolly traveling beneath the boxes. All boxes can he installed in and remove from the line without personnel‘s having to enter the area behind the shielding. This reduces maintenance costs, as a defective box can be removed from the high background area for repair. A general view of the remote lines is shown in Figure 10. As with the UCRL facility, each box contains specialized equipment designed to handle a specific determination or step in au analysis. Some analyses are carried out in their entirety in. these boxes; others are completed in a conventional laboratory after separation of the constituent to be analyzed. EXAMPLES
OF REMOTE APPARATUS
Liquid Sampling Equipment. Most samples of radioactive materials are received in the liquid state. For these, the initial analytical step is pipetting a known volume of sample. Figure 7. UCRL junior cave for low level analysis
An example of a remotely operated sample pipetter is the Servo-Pipettor, a product of the Oak Ridge National Laboratorv 119). This unit iFieure 11) is a positi;eAiipIaceent, sGrvc7-moto;operated device. I n operation, the needlelike tip pierces a rubber diaVOL. 29,
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Vhragm that seals the sample bottle and the sample is drawn into the barrel of the pipetter by suction. With the pipetter thus filled, a.ny desired sample volume up to 800 PI. can he delivered. The control dial is calibrated directly in microliters. After each aliquot is delivered, the pipetter needle must be rinsed to ensure that no sample clings to the needle. In Figure 11 the control box normally located outside the shielding is shown a t the left. Next is the deeapper unit for sample bottles not having rubber diaphragms. In front of the pipetter is a magnetic stirrer and a t the right are the vacuum solenoid valve and liquid traps. The precision of measurement for this pipetter was stated to be within =t0.2%(unitsnot given). Solid Sampling Equipment. Preparation of solid samples for analysis customarily involves dissolution. I n a conventional laboratory, metal turnings or drillings are used in the dissolution. This machine operation is difficult to accomplish remotely, and a simpler technique-electrolytic dissolution (Figure 12)-has been developed for sampling metallic uranium in the Atomics International hot cell
(8.
Figure 8. STORAGE
UCRL piano-type glove box
