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of research emphasized at the individual locations, in part from the lack of opportunity to date to prove the validity of some design details, and finally from the inherent differences in the manner in which any two individuals might accomplish the same task. UNIVERSITY AND INDUSTRIAL LABORATORIES
Although the scale of construction planncd by the Atomic Energy Commission is necessarily large because of its primary emphasis on nuclear research, the greater interest, numerically a t least, probably is in the const,ruction or remodeling of laboratories on a more modest scale. University and industrial laboratories in which the emphasis is more diversified or which use radiochemical techniques merely as a research tool are concerned with, a t most, a few laboratory units usually for tracer research. The problems of designing such units and of remodeling existing laboratories are considered in separate papers in thi5 symposium.
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Vol. 41,
NO. 2
GENERAL FACTORS
Because of the wide range between the levels of radiation from the microcurie to the multicurie scale involved in current research problems, the variety of radioisotopes which are being used in chemical research, and the differences between the types and intensities of the radiation emitted by these isotopes, the problem of designing working spaces in which research may bp carried out efficiently and safely necessarily has no single solution. These factors may be subdivided on the basis of the hazards attendant on chemical operations with each. This analysis, in turn, permits consideration of the design features and manipulative methods requisite or desirable for the corresponding subdivision. RECEIVSD3 I a y 10, 1948. Based on work performed undev Contract W-35-058-eng-71 for the Atomic Energy Proieot a t Oak Ridge National Laboratory.
Impact of Radioactivity on Chemical laboratory Techniques and Design PAUL C. TO3IPKINS AND HENRI A. LEVY Oak Ridge iVutional Laboratory, Oak Ridge, Tenn. T h e radiative properties of radioactive substances are independent of their chemical properties and impose additional requirements on chemical laboratory design and practice. A general philosophy is developed through which problems associated with the handling of radioactive materials may be successfully attacked. A n attempt is made to establish a basis on which to build satisfactory standards of practice, and to evaluate the resulting impact on the facilities for implementing them. In particular, the segregation of areas of work, and types of facility appropriate to each, are discussed. Problems of ventilation, accumulation of activity, and material control are examined in the light of these considerations. The selection of laboratory furniture, surface materials, floors, and shielding is discussed.
T
111s paper discusses features of chemical laboratories and laboratory practice peculiarly ielated to the full and safe use of radioaktive materials. Present design and technique are tailored to the chemical properties of materials of investigation. Design and technique for radiochemical laboratories should be compatible as Fell with radiative properties; these, being essentially nuclear, are independent of chemical properties and impose additional variable requirements in laboratory practice. The requirements imposed by radioactivity are discussed relative t o two major parameters: radioactive contamination and pcnetrating radiation. The objective of technique and design is the execution of operations, which are chiefly prescribed by chemical considerations, n7ithout jeopardy to personnel, experiments, or products from undesired effects of radioactivity. In choosing a manipulation for carrying out a chemical operationfor example, the separation of a solid from a liquid phase-filtration by gravity or suction, or centrifugation, is no longer a matter of convenience or purely chemical effectiveness; the choice is one in which the radioactive parameters, contamination and radiation, often play a determining part. In the absence of radioactivity, the wide variety of manipulative problems encompassing the practice of chemistry is reflected in different kinds
of laboratories-for example, those for microchemistry, control analysis, physical chemistry, or general experimental chemistry. The impact of radioactivity on each will be different, but in all cases it will depend on the magnitude of the contamination and radiative levels. COhTbR.I~NA'ITONPARAMETER
By radioactive contamination is meant the unwanted migration of radioactivity into places where it may harm persons (on skin or in lungs), experiments (into reagents or analytical samples), or products. The prevention of serious contamination is really a problem of matcrial control, as radioactivity is always associated with matter. It differs from more usual problems of material control in that the amounts of material involved may range down t o small fractions of a microgram. I n discussing the problem of contamination it is uaeful to define several concepts. The critical quantity, q, is defined as that mass or volume of material containing an amount of radioactivity, a, which may bo objectionable in a given situation. For example, for hard betscontamination on an open table top, a is taken from health considerations as 0.001 microcurie per square foot. Thus, for a solution containing 0.01 pc. in 10 ml., q is 1 ml., with which there is no difficulty of control; in contrast, for a solution containing 1 mc. in 10 ml., q is 10-6 ml., a volume which can easily bc lost during chemical operations and whose control may be difficult. For solid materials, uranium is analogous to the first example, radium t o the second. The complement of the percentage of the total activity which constitutes a is defined t o be the re uired degree of control: Thus in the second example a is 1 0 - 4 of the total (1 me.) and the required control is thereforc 99.9999~&
%
Chemical operations can rarely be expected to meet such stringent control requirements. If this is the case, there pxisls a contamination potential: This term the authors define as the ratio of the quantity of material which may be lost in a given operation performed by a given technique t o the critical quantity, q. Thus in the second example quoted above, if a pipetting is made by ordinary methods, for which loss of 0.01 ml. is easily possible, the contamination potential of the operation is 0.01/10--6 = 1000. A value of the con-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
tamination potential greater than unity calls for supplementary measures, such as t o ensure t h a t radioactive material which may be thus out of control does not reach a region where it may cause actual trouble. For the example just cited, paper or trays under the apparatus would be indicated. Viewed from this standpoint the contamination problem presents two aspects: (1) t o devise techniques which reduce the contamination potential to a minimum (by increasing the degree of material control achieved), and (2) t o provide supplementary measures for rendering any loss of material harmless. The problem of controlling minute, often invisible quantities of material resembles the problems of bacteriology more than those of conventional chemistry. I n analogy, the term “radiochemical asepsis” is borrowed to describe measures which are employed as standard practice to combat a n unfavorable contamination potential. These measures include the following: Working surfaces have disposable covers such as blotting paper (changed at frequent intervals) beneath which are placed nonporous hard containers such as trays of stainless steel; vessels or equipment which may conceivably be contaminated are never handled with the bare hand, but gloves, paper protectors, or short tongs are used instead; similarly, a contaminated object such as a used pipet is never put down on the working surface directly, but instead into a tray or tank provided for the purpose; contaminated equipment is cleaned at a place where no interference with uncontaminated operations will result. The impact of the contamination parameter In design and technique is illustrated in Table I. There, four levels of total activity are distinguished. I n the lowest level, < 1 pc., the required degree of control is in the neighborhood of 99.9% (its precise value will of course depend on the value assigned t o a ) ; this is a degree achievable in‘ the main by techniques of quantitative chemistry. Nevertheless aseptic precautions are called for as a safety measure. An ordinary laboratory, modified t o make possible aseptic measures, is usually satisfactory. It should be remembered that the radioactive material may be toxic even in the low activity handled, so t h a t any ingestion or inhalation should be avoided. I n this class fall the large majority of tracer experiments involving counting of beta-particles. In the second level, 1 pc. to 1 mc., the required control may be as high as 99.999%. The techniques of quantitative chemistry may here fall short of the requirement, giving contamination potentials of 10 t o 100, while the more crude techniques of qualitative or preparative chemistry will give contamination potentials vastly higher. For example, in pouring a solution from a n open beaker, there is a high probability that -0.01 t o 0.05 ml. will run down the outside of the vessel; with a solution of concentration 0.1 mc. per ml. this common manipulation presents a contamination potential of -1000 t o 5000 and accordingly must be avoided. At this level, in addition t o standard aseptic precautions, other measures are recommended. Equipment used for materials at this level of radioactivity must be carefully segregated
+.
Level Features of technique
Special features of laboratory and equipment, in addition t o aseptic precautions Special problems
Examples
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from low-level items to avoid cross contamination. Thus, duplicated storage and cleaning facilities are advisable. The working area should be adapted to combating a mildly unfavorable contamination potential : It is recommended t h a t the working area be a well-ventilated hood with adequate air velocity through the open working face (-100 feet per minute); the surfaces should be nonporous, noncorroding, and cleanable, without cracks or sharp corners where lodged material may be difficult t o remove; utilities should be controllable from outside. A hood answering these requirements we may call a radiochemical hood; a detailed design that is completely satisfactory may have t o await further experience in the laboratory. Other special precautions in operation at this level may be undertaken, depending upon their convenience in relation to the operations involved-for example, contamination potentials may be significantly reduced, by increasing the degree of control achieved, by introducing totally closed equipment in place of the more usual flasks and beakers. Operations falling into this class include tracer experiments with gamma-counting, and the preparation of a supply of beta-tracer. At the third level, 1 me. to 1 curie, the required degree of control is beyond t h a t achievable by any conventional chemical nianipulations. Enclosed operations are mandatory: either totally closed systems of vessels, or enclosure of open equipment in a “glove-box” type of device. The use of a radiochemical hood is likewise mandatory. At this level, disposal of waste becomes a perplexing problem, for which adequate provision must be made. As one goes t o higher activities, and often more unfavorable contamination potentials, the activity borne in the ventilating system, drains, or similar facilities becomes important. T o prevent accumulation of long-lived material it is desirable t o mop ventilation ducts occasionally to remove loosely adhering deposits. I n more stringent circumstances, the incorporation of a water spray in the duct is desirable. The fourth level, > 1 curie, will be discussed only briefly. Complete enclosure of equipment is necessary (glove-box or cubical). Ducts and drains must be decontaminable. All wastes must be disposed of in a safe manner; temporary or permanent waste storage may be called for. The extreme contamination potent ials encountered call for buffer areas separating the high-level area from other areas where radioactive contamination must be kept a t a low level. The spread of contamination is a matter of probability. The precautionary measures must be sufficient t o prevent irreparable harm, even in the event of a n accident; further elaboration must be balanced against the cost of ruined experiments or ruined equipment and the hazard of inhaling contaminated air or wearing contaminated clothing. The probability of spreading contamination by second- or third-order transfers of material originally lost in a restricted area is a function of the number of items that enter and leave that area; this probability is reduced t o the extent dictated by the economy of the consequences, by segre-
TABLE I. EFFECTOF CONTAMINATION HAZARD
< 1 Microcurie Quantitative technique 99.9% control, aseptic precautions Ordinary laboratory
1 Microcurie t o 1 Millicurie 99.999% control segregation of equipment t o avoid cross contamination avoid spat,tering and soln: losses Radiochemical hood desirable, storage and cleaning facilities duolicated. nrotectbenchtops, ’ Adsorption of high specific activity material. hand contamination a d d 2nd order transfer
’
1 Millicurie t o 1 Curie 99.999999% control, enclosed operations, either equipment or area
> 1 Curie Extreme control, complete enclosure, buffer areas
Radiochemical hood mandatory. Cleanable ducts, special waste disposal
Decontaminable ducts and drains, dry box or cubical
Decontaminatable surfaces. accumulation (long-lived activity) : ventilation, protection against accidents important Preparation of stocks of y tracer. high level C14 synthesis, therapeutio work
Gas, liquid, a n d solid waste storage or disposal
~
Protection of experiments in vicinity of higher level operations Tracer level experiments with @-counting
Tracer level experiments with r-activity counting: preparation of stocks of 8tracer, process tracer application
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Vol. 41, No. 2
TABLE 11. EFFECT O F EXTERSAL R'4DIATIOX HAZARD
c
B
Level Appropriate techniques
A Ordinary methods, avoiding direct contact
Appropriate equipment and facilities
Simple handles on equipment. tongs
Standard radiative precautions; well designedstraight tongs with ordinar equip ment, or m o u n t e J e q u i p 1 ment; sampling devices
Examples
Csual &tracer scale ( p c . ) except when high specifio activity material is In concentrated form
Tracer experiment with y counting; preparation of ' &tracer stocks if accompanied b y -,; pc. samples of @-emitters i n concentrated form a n d unshielded
Protection b y distance alone permitted, straight-line control
gating work into areas of comparable contamination potential, by restricting traffic between areas, or by initiating buffer regions between areas of widely different contamination potential. This has an immediate impact on the operation of laboratorics engaged in xork covering a wide range of activity such as 0.001 fie. t o I me. The area rcquired per man becomes critically dependent on the problem, and one person may require as many as three laboratory benches instead of one. It often mcans the duplication of apparatus, hoods, cleaning, and similar facilities for doing precisely the same procedure but a t different activity levels. Therefore, what, mighb be a four-man laboratory in the absence of radioactivity may become a one-problem radiochemical laboratory, and the occupants of that rooni must be working on the same problem if cross contamination is to be avoided. Many people feel, also, that work in any one laboratory should be confined under some circumst'ances to one isotope of a given element. The proportion of the laboratory space devoted to each level is determined by the complexity of the work involved and the number of items that must be removed from the work area itself for cleaning and storage, since the latter facilities must also be isolated from the rest of the laboratory so far as common usage is concerned. These features are considcred in greater detail in relation to the conversion of chemical laboratories t o radiochemical work in another paper. EXTERNAL RADIATION PARAIVIETER
The basic problem introduced by external radiation is one of health protection; the technique and conduct of the laboratory must ensure that no person will accumulate more radiation exposure than the tolerance limit, the equivalent (in biological effect) of 0.3 roentgen per week of x-radiation. The hazard of a given exposure depends on the following factors: time exposure, amount of activity, hardness of radiation, mass associated with source, distance of source, and shielding interposed. The readily variable factors, time, distance, and shielding, are usually adjusted to reduce the exposure t o a safe value. Detailed limitations of the radiative problem are considered in other papers; here we deal with a few important generalisations. A classification of levels of the radiative parameter is shown in Table 11. Four levels are distinguished, according to the type of technique considered appropriate. Level A needs little comment; here are included operations with very little radiative hazard, and only direct contact wit,h active material must be avoided. The great majority of tracer experiments not involving gamma-activities fall here. An exception is the handling of beta-samples, even a t the tracer level, when reduced to small mass. Level B includes operations for which distance alone provides protection, This level is evidently limited when the necessary distance becomes inconveniently great, and hence may overlap the next level. It is characterized by the absgnce of shieldingthat is, straight-line control methods are applicable. At this
Shielding required, except for occasional, relatively brief exposure of source (minutes) Close shielding with modified laboratory equipment; o r small barrier with modified lab. equipment and bent tongs, or. inounted equipment with barrier hfillicurie samples of y-emitters, or @-emitters in concentrated form
D Conrinuous shielding, no exposure. other t h a n POS: sibly a few seconds duration, n o t repeated Mounted equipment with masBive harrier; aimplified manipulations; indirect vision; procedure reduced t o routine Curie samples of ./-emitter>
level and higher ones, a set of standard radiative precautions is recommended: the chief of these is the monitoring of the radiativc level a t the position and time of each manual operation. Particular attention should be paid t o radiative levels a t hand positions. Techniques a t this level often involve ordinary laboratory equipment handlcd with sufficiently long tongs. The method often suffers from a loss of manual dexterity; hence new techniques, perhaps involving mounted equipment,, are advisable. In this category fall the handling of concentrated beta-samples of low activity-, and tracer experiment.s involving countable activities of gamma-emitters. In levels C and D, techniques with shielding are required. Depending on t,he level and hardness of radiation, the departures from ordinary techniques will be greater or smaller. For example, in a limited range involving pure beta- or very soft gammaactivities it is possible to surround individual pieces of conventional equipment, or modifications thereof, with shielding up to an inch or two bhick; the shielding may be transparent. This technique is known as "close shielding." In general, required thicknesses will be too great for close shielding; then a barrier i5 erected enclosing the operations. "Bent" tongs suitable for operation over, around, or through the barrier become necessary. For the most part conventional equipment is too awkward and too risky for use in this manner, although its use is still fairly general. Perhaps the most serious indictment of t'his whole approach is that the poor maneuverability inherent in it generally drives one into the unwise practice of working with his hands behind the barrier. Modifications in the direction of mountcd equipment are recommended. At the highest levels (D), very elaborate shielding and manipulative problems are encountered. Satisfactory solutions require t'hat only simple manipillations be undertaken and that all operations be reduced t o a routine. At any level it is important to design both laboratory and techniques so that the bulk of the work is performed easily. On the spot, makeshift arrangements never work well. Therefore shielding built into walls, hoods, and table tops provides more inherent safety than does shielding provided by each individual for each experiment. It is especially important that the laboratory be designed so that persons in adjacent areas working on different prohlems arc automatically protected from radiation arising from work not their own. In t,he general case, both contamination and penetrating radiation are met simultaneously. For the most part, the appropriate principles applicable to the two parameters must be applied together. Some techniques sufficient to control contamination are inconsistent Yith radiation protection-for example, the use of a glove box-but for the most part the requirements can be reconciled. Space and distance are cheaper to provide than massive shield! and are also more easily reconciled with techniques for control of contamination. This presents a pot,ent argument for allocating space by problems, and thus devoting an entire area t o a given problem a t any one time, when working a t the millicurie levrl
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INDUSTRIAL AND ENGINEERING CHEMISTRY
and above where radiative level C is encountered more frequently. When massive shielding is necessary, as in a laboratory where chemical operations are performed routinely on gamma-activity, heavy floor loading must be provided. The frequency with which a given operation is met is important in determining when compromise measures become inadequate. Thus an ideal situation could be derived for handling the radiative problem a t level D from two extreme situations: a completely versatile, automatic, pushbutton, maintenance-free laboratory shielded on all sides, or bare space in which ideal facilities for each experiment could be built. Both are economically impractical, unnecessary, and a t variance with the requirement that there should be the minimum interference to the conduct of work. Therefore, the practical laboratory should have some features based upon both philosophies, and many facilities will be a mixture of each. Many specific examples of these points are presented in other papers of this symposium. SUMMARY
The critical factors with respect to contamination and radiation which must be established and reconciled for each laboratory facility are, for contamination, (1) the quantity, a, for different phases of laboratory operation based on the indicator most sensitive to contamination interference, (2) the upper limit for total activity and anticipated material losses based on the specific techniques being used, and the contamination potential based on both normal operation and the total sample, (3) the proportion of space needed for each activity level, and (4)the cost in time, money, and interference to the program to provide adr-
231
quate protection in the event of a mishap. All work must be planned so that both the probability risk and the consequence of a wrong guess are acceptable. The critical factors that must be established from the standpoint of radiation protection are: upper limits for the time and intensity of exposure encountered at each phase of the operation; these in turn set an upper limit to the total activity permissible with a given type and energy of radiation. If actual numbers cannot be applied to each of these limits, one should make appropriate exploratory measurements. On the basis of these data one should then examine the procedures and techniques, making alterations where indicated. The most hazardous aspects of every part in the procedure or phase of operation should be found and these points monitored with appropriate radiation-detecting devices. Particular attention should be paid to the exposure received by the hands, because they usually approach most closely to the radiation source. One concludes that in the operatioil of radiochemical Tacilities, two degrees of freedom, manipulative and procedural, are a t least partially lost, owing to the contamination and radiation parameters. Below 1 me., this need reflect only minor changes in existing laboratory design, but major changes in exist'ing laboratory practice. Above 1 me., one must specify more rigidly not only what kind and how much activity will be met, but t'he methods by which the work will be conducted. The laboratory may then be designed to meet these limits, leaving for special consideration problems that fall outside the specifications. RECEIVED August 28, 1948. Based on work performed under Contract W35-058-eng-71 for the Atomic Energy Project a t O a k Ridge National Laboratory.
Radiobiochemical laboratories WILLIAM P. NORRIS, Argonne National Laboratory, Chicago, I l l .
R adiobiocheniical laboratories, with few exceptions, may be considered, because of the nature of the work, to be concerned with levels of radioactivity not exceeding 10 mc. On a functional basis the operations involved may he considered to fall into five general categories: preparation of active materials in a form suitable for biological investigation, administration of active materials, care and housing of biological specimens containing radioactivity, preparation of samples for radioactivity measurements, and measurement of radioactivity. Ideally these operations should he carried out in separate rooms. While precautions are required to handle as much as 10 mc. of
radioactivity, protection against external exposure from sources of this magnitude may be achieved without a great expenditure of effort in most cases. A much more difficult problem is that of avoiding radioactive contamination, especially in working with animals where radioactive metabolic by-products are being eliminated. It seems advisable, therefore, to consider the installation ofwell-ventilatedisolation areas for specimens which are eliminating appreciable quantities of radioactivity. Other considerations include general laboratory ventilation, special hood facilities, surfaces which can be readily decontaminated, and construction to eliminate areas difficult to keep clean.
T
active materials in a form suitable for biological investigations, (2) administration of active materials, (3) care and housing of biological specimens containing radioactivity, (4) chemical manipulations, isolation of compounds, and preparation of samples for radioactivity measurements, and (5) measurements of radioactivity. Ideally these operations should be conducted in separate rooms equipped to require no exchange of equipment. This is desirable in order to produce reasonably clear-cut definitions of the possibilities of radioactive contamination in any single area and t o minimize the chance of cross contamination.
HE problems encountered in biochemical investigations provide opportunities for the use of a wide variety of radioactive elements with an equally wide variety of biological materials. Except in cases where large amounts of the radioactive isotope are used purposely to produce radiation effects, the quantity of radioactivity administered to the organism is ordinarily kept a t a n absolute minimum compatible with analytical sensitivity and accuracy, to ensure the least possible opportunity for the production of metabolic abnormalities. Therefore, it should be possible to carry out the majority of biological investigations, even with animals as large as dogs, without requiring more than 10 to 20 me. of radioactivity distributed throughout the experiment. Biochemical laboratories thus tend to fall within the range of semihot to low level installations, although these terms are fairly ambiguous. On a functional basis the operations involved may be oonsidered to fall into five general categories: (1) the preparation of
GENERAL CONSTRUCTION
Any area exposed to radioactive contamination should be constructed of materials which are nonporous and readily decontaminated. Of the materials considered, glass and stainless
