US3138711A - Apparatus to simulate radioactive fallot - Google Patents

Description

June 2 1954 J. F. BATTER, JR 3,138,711

APPARATUS TO SIMULATE RADIOACTIVE FALLOUT Filed Dec. 2, 1960 3 Sheets-Sheet 1 TEST LOOP SOURCE AT START OF TEST FIG! RETURN TUBE (WHITE) PRESSURE TUBE (RED) F I G2 65 [1' U SIMULATED {RADIATION INVENTOR.

JOHN F. BATTER JR. BY

ATTORNEY June 23, 1964 J. F. BATTER, JR 3,138,711

APPARATUS TO SIMULATE RADIOACTIVE FALLOUT Filed Dec. 2, 1960 3 Sheets-Sheet 2 IN VEN TOR.

JOHN F. BATTER JR ATTORNEY June 23, 1964 J. F. BATTER, JR 7 3,138,711

APPARATUS TO SIMULATE RADIOACTIVE FALLOUT Filed Dec. 2, 1960 3 Sheets-Sheet 3 FIG.6 F|G.7

FIGS

INVENTOR.

JOHN F. BATTER JR.

ATTORNEY United States Patent ()fi ice 3,138,711 APPARATUS TO SIMULATE RADIOACTIVE FALLOUT John F. Batter, Jr., Hampton, Va., assignor to Technical Operations Incorporated, Burlington, Mass., a corporation of Delaware Filed Dec. 2, 1960, Ser. No. 73,439 6 Claims. (Cl. 25083.6)

This invention relates to methods and apparatus to simulate radioactive fallout, and more particularly to simulate a radiation fallout field of any desired configuration, such as, for example, the radiation field from fallout on an area of the ground, or on a roof, or a field from a ring-shaped area or any other shaped area, whether uniformly or nonuniformly contaminated.

The effects of radiation fallout on inhabited territories is a matter of extreme concern to society, not only as a probable consequence of nuclear attack, but also as a consequence of accident in an atomic energy facility.

Two studies attempting to evaluate the probable consequences of an all-out nuclear attack on the continental United States have predicted that if we remain completely unprepared, we shall suffer casualties of the order of 60 millions of our 180 million population. These studies are International SecurityThe Military Aspect (The Rockefeller Report), Doubleday, Garden City, New York, 1958; R322RC: Report on a Study of Non-Military Defense, The Rand Corp., July 1, 1958. Such numbers are arrived at by assuming an attack against 50 of our most important cities as well as our SAC facilities; they include deaths and injuries from fallout radiation at considerable distances from the targets as well as from direct effects of blast and heat in the cities themselves. The studies differ in their assumptions about the success of such an attack; the Rand group did not analyze enemy capability in the light of United States military defenses but simply assumed enough weapons to destroy the targets, thereby arriving at a considerably higher proportion of deaths among the casualties. However, they both agree that the order of 30 million casualties, including 20 million deaths, can be expected to result from fallout alone, independent of immediate effects, if nothing is done to help the populace to defend itself against this threat.

The Oflice of Civil and Defense Mobilization, in its task of organizing the nation against nuclear attack, is placing considerable emphasis on a fallout shelter program. As was pointed out in the Rand study, such shelters are much cheaper to construct than blast-resistant bunkers, and are thus more effective on a casualties saved per dollar basis. More importantly, many casualties could be saved by proper use of the shelter people now have available-shelter consisting of basements of residences as well as of larger public structures-4f these can be defined and made habitable now for future emergency use.

The assignee of the present application has determined that even a large attack is unlikely to produce extensive areas where the effective integrated fallout dose exceeds about 10,000 roentgens. Now it is fairly well known that though the median lethal radiation dose is about 450 roentgens, lethality drops rapidly with lower integrated dose until at 100 roentgens one has essentially 100 percentp robability of survival. These two facts demonstrate that if shelters attenuate incident radiation by factors in the neighborhood of 100, a very large proportion of the population subjected to fallout would be saved.

Investigation of the physical basis underlying radiation attenuation by complex structures, such as homes, oilice buildings, barracks, warehouses, ships, and others, has included considerable work on the physics of gamma ray 3,138,711 Patented June 23, 1964 pecially in large complex buildings.

Ideally, the attenuation which a structure provides against fallout radiation from a nuclear detonation can be measured by extensively instrumenting a structure erected in the prospective path of fallout from a test explosion. Historically, attempts have been made to perform this type of experiment. However, the unpredictability and uncontrollability of real fallout arrival on a structure have left the results either too meager to be of use or at best of questionable value. To provide adequate experimental data of sufficient quality, it has been found necessary to simulate the fallout field with an array of suitably distributed radioactive sources. Two principal factors are of importance. First the geometry of the radiation field must be meaningful in terms of likely fallout distributions and secondly the energy spectrum of the fallout field must be simulated. Since the calculation of protection factors olfered by structures is closely related to both these effects, the necessary experimental approach was strongly influenced by these considerations.

The gamma energy spectrum of fallout radiation is not only complex but also continuously changes with age. Initially at about one hour after detonation the radiation behaves as if it were concentrated at about 1.25 mev. energy. During the following 24 hours it softens until it reaches an equivalent energy of about 0.7 mev.; then harder components grow in until at about 10 days the spectrum behaves as though it were concentrated at 1.25 mev. once again. In calculating protection factors it has become customary to assume this higher energy whenever simplification was necessary since this would not tend to overestimate shelter capability. Thus the iostope cobalt- 60 with its equal numbers of 1.17 and 1.33 mev. quanta, its 5.3 year half life, and its ready availability in multicurie amounts has been chosen for most experimental measurements.

Earlier experiments involving fallout simulation employed a multiplicity of small sources arranged in a fixed pattern. Because of the difiiculty of safely distributing and recovering such sources, work in general has been limited to small sources placed in extremely simple geometric patterns.

To overcome the foregoing difliculties, it is proposed according to the present invention to use a single source of radioactive energy (e.g., gamma radiation) which can be remotely controlled, as by circulating it through tubing distributed over the area the fallout on which is to be simulated. Thus, because the path of the source can be laid out in advance without concurrently exposing the operator to radiation, the pattern can be made to any arbitrary degree of complexity and can simulate fallout deposited upon the ground, a structures roof, or other area in which fallout might collect. This technique makes it possible provide a more nearly realistic simulation of fallout geometry. By using time integrating isotropic response radiation detectors (commonly available as dosimeters) at one or a number of selected points within the structure, the radiation from such a single source is made to appear as arising from an area source.

It is an object of this invention to provide a method and apparatus to simulate radioactive fallout. Another object is to provide such method and apparatus which will enable simulation of fallout of any arbitrary pattern over any arbitrary area without danger to an operator. It is a more specific object to provide such a method and apparatus to simulate gamma ray fallout. It is a further object to provide such apparatus which is completely portable and which is fiexible in operation and can be used and maintained with facility.

Other and further objects and features of the present invention will become apparent from the following description of certain embodiments thereof. This description refers to the accompanying drawings, wherein:

, FIGS. 1 and 2 are schematic illustrations of apparatus according to the invention;

FIG. 3 illustrates one manner of practicing the method of the invention;

FIG. 4 shows a source capsule with leader attached;

FIG. 5 illustrates another manner of practicing the invention; and

FIGS. 6, 7 and 8 illustrate a storage unit for the apparatus shown in FIGS. 1 and 2.

Referring now to FIGS. 1 and 2, a storage unit 10, which will be described in greater detail in connection with FIGS. 6, 7 and 8, contains two passages, here illustrated schematically as passages 11 and 12 through which a source capsule may pass. A length of tubing 13, identified as a test loop in FIG. 1, and consisting for example of inch inner diameter polyethylene tubing, which may be a mile long is connected at one end 14 to one of the passages 12 and at the other end 15 to the remaining passage 11 in the storage unit 10. The other end of each passage is connected to further tubing and control devices as shown in FIG. 2.

Referring now to FIG. 2, a pressure line 16, also of tubing is connected at one end to the first passage 11 in the storage unit 10 via a coupling 17, labeled pressure tube" in FIG. 2. The remaining (left-hand in FIG. 2) end of the pressure tube 16 is connected via pressure relief valves 18 and 19 to a parallel arrangement of two pumps, a main pump 21 and an auxiliary pump 22 which are connected to the pressure tube via hand valves 21.1 and 22.1 respectively. The main pump is preferably a relatively slow-speed constant volume water pump for producing constant velocity of pumping of fluid in the test loop 13, and the auxiliary pump 22 is preferably a high volume, for example, a gear pump, useful for initially filling the test loop 13 and for moving water through the test loop at a relatively high speed, as will hereinafter be more particularly described. A reservoir 25 holds water 26 and the two pumps have lines 21.2 and 22.2, respectively, leading into the reservoir and preferably having filters 21.3 and 22.3, respectively, at their input ends.

A length of return tubing 28, connected at the righthand end to the second channel 12 in the storage unit 10, via a coupling unit 29 as shown both in FIGS. 1 and 2, is connected at its left-hand end in FIG. 2 to a check valve 31 and therethrough to an exhaust tube 32 into the reservoir 25. A safety by-pass valve 34 connects the pressure tube 16 to a second exhaust tube 35 and therethrough to the reservoir 25 for a purpose to be hereinafter described. Referring now to FIG. 4, a capsule generally illustrated at is adapted to hold an active volume (not shown) of radioactive material in its interior region 41 which can be closed by a screw plug 42 and sealed as by silver solder 42.1 as shown in the figure. One end of the capsule is attached to a wire rope 43 and the other end of this rope is attached to a leader 44 which has a washer, preferably a pump leather washer 45 afiixed to it to aid in propulsion of the capsule and its leader through the test loop as will be hereinafter explained in greater detail. The leader and the pump leather washer may be conveniently referred to as a piston, 45.1. The wire rope is conveniently fitted with spacing beads 46 to enable it to negotiate passage through the test loop.

Referring again to FIG. 1, the position of the capsule 40 at the start of a test run is shown in solid line in the first channel 11 in the storage unit 10 and its position at the end of a test run is shown in dotted line in the second passage 12. Referring now to FIGS. 6, 7 and 8, a practical storage unit 10 is illustrated as comprising a body 50 4 of radioactive shielding material, such as lead or spent uranium ore, having two passages 11 and 12 through it. FIG. 6 shows one of these passages 11 generally in cross section. At the ends of this passage 11, there are illustrated two couplings 11.1 and 11.2 which are suitable for the connection thereto of flexible tubing such as polyethylene tubing. The tubing can be disconnectibly connected to each passage by the use of such couplings. A pair of handling ears 51 are attached to the body 50 to enable it to be carried and a flat skid-like base 52 is provided to hold it in position at rest. The physical positions of test loop end portions 14 and 15 and of the pressure tube 16 and return tube 28 are shown in FIG. 8, in a schematic manner. The passages 11 and 12 are preferably curved so that when the source capsule 40 is at rest in the median portion of a passage the maximum shielding is afforded by the body of shielding material 50. To this end the piston comprising elements 44 and 45 shown in FIG. 4 is spaced by the leader wire rope 43 a distance from the capsule 40 such that when the piston is at one end of a passage 11 or 12 the capsule is in the median region of that passage, as can be seen more clearly in FIG. 1 where the piston unit is schematically illustrated as 45.1 and the leader 43 is illustrated by a dotted line 43.1 in each case.

The operation of the apparatus which has been described in connection with FIGS. 1, 2, 4, 6, 7 and 8 is as follows. The test loop is laid out over an area over which a radioactive fallout pattern is to be simulated as will be described below in connection with FIGS. 3 and 5. The storage unit contains a capsule containing an appropriate charge of radioactive material, for example, 200 curies of cobalt 60 or from 200 to 400 curies of iridium 192. At the start of a test the source capsule 40 is located in the median region of the first passage 11 in the storage unit 10 and the piston unit 45.1 is at the beginning of the test loop 13, namely at the end 15 thereof. Through the means of the auxiliary pump 22 water under pressure is forced into the test loop 13 and the test loop is then connected to the storage unit 10 and water pressure from the main pump 21 is then applied by opening the hand valve 21.1 and closing the hand valve 22.1 and pressure from the main pump forces the piston 45.1 through the tubing of the test loop 13, carrying the source capsule 40 behind the piston on the leader 43. The pump leather washer 45 fits snugly within the tubing 13 and acts like a piston under control of water under pressure and filling the test loop. The main pump 21, is, as has been mentioned above, preferably a constant volume pump which enables both the speed and the position of the capsule 40 in the test loop 13 to be accurately controlled. The auxiliary pump 22 is useful on the other hand for the purpose of advancing the capsule 40 rapidly to a desired position, as well as for filling the test loop with water prior to starting. The constant volume pump 21 will drive the source assembly of FIG. 4 at any predetermined rate for example between 50 and 3000 feet per hour. The higher speed pump 22 permits source assembly velocities up to about for example 20,000 feet per hour (but not necessarily at a uniform rate) when desired.

The pumps 21 and 22 are connected by means of the hand operated valves 21.1 and 22.1 to a main high pressure manifold. This manifold contains the pressure relief valve 34 set for example at pounds per square inch, which returns the pumping solution (here, for example, water) back to the reservoir 25 and remotely operated solenoid valve 18 which can either apply pressure to the rear of the source capsule 40 and piston 45.1 assembly in the storage unit 10 or return the pumping solution to the reservoir 25. Valve 19 is a part of the pressure relief valve assembly. Initially, the solenoid valve 18 is adjusted to by-pass the water fiow from the pump which is being used to the reservoir 25and the pump is started. When circulation of the source 40 is desired, the solenoid valve 18 is actuated to connect the output of the pump being used to the tube leading to the storage unit, namely the pressure tube 16. The Water flow then acts on the piston 45.1 forcing the source capsule 40 out into the test loop 13 and finally back into the opposite tube 12 in the storage unit 10.

When the source capsule 40 has returned to the second tube 12 in the storage unit 10, the piston 45.1 is brought to rest at the far end adjacent coupling 29 leading to the check valve 31 and this automatically positions the source capsule 40 in the median region of the curved tube 12. Here the piston may be retained bymeans (not shown) until the pressure in the system rises gradually to 100 pounds per square inch, which 1s well below the bursting pressure of the tube 13 (of 00 pounds per square inch, for example) at which point the pressure relief valve 34, 19 will trip and by-pass the pump which is being used to the reservoir 25 or the solenoid valve 18 may be returned to the free position which allows return of the pumping water tothe reservoir 25. Under normal circumstances, while the source capsule 40 is being circulated, the internal pressure within the test loop 13 is approximately pounds per square inch. The check valve 31 is an ordinary ball type check valve which is included to prevent reverse flow of the pumping fluid in the test loop 13.

By virtue of the disconnectible couplers illustrated for example as coupling elements 11.1 and 11.2 in FIG. 6, the storage unit can be reversed in the apparatus shown in FIGS. 1 and 2 so that the source capsule 40 in the position in which it is shown at the end of a test will then be in position for the beginning of another test run. That is, the passages 11 and 12 can be interchanged in the system simply by breaking the four connections to the tubing ends 14, 15, 16 and 28 turning the storage unit 10 180 about a vertical axis as shown in FIG. 1, and remaking these connections so that the capsule at the end of a test run then comes into a position for beginning another test run. For safety purposes, color coding as shown in FIGS. 1 and 2 illustrate at all times, in either position of the storage unit 10, which tubing end is connected to which coupling unit on the storage unit. Thus the ends of the storage unit tubes 11 and 12 which are shown as white are diagonally opposite each other as are the ends which are shown as red.

Referring now to FIG. 5 a house 60 is shown surrounded by the test loop 13 here shown in the form of a spiral 13.1 for the purpose of simulating a uniformly contaminated ground area around the building 60. FIG. 3 shows another arrangement in which the test loop 13 is arranged in a series of convolutions 13.2 on one side of a building 65, following a symmetry technique designed to reduce the area over which simulation is required in the case where a building is similarly constructed to right and left of its center so that the simulated fallout pattern can be laid out only around half the building to yield results that will be valid for both halves. As FIG. 3 shows, the reservoir 25, the storage chamber or unit 10 is located some distance from the building 65 and the pump, for example pump 21 and water reservoir 25 are located still further from the building. In actual practice the pump and water reservoir are located remotely from the storage chamber, for example the storage chamber may be in one truck and the pump and water reservoir in another so that actual control of the source capsule from the time it leaves the storage chamber 10 until it returns is exercised some distance from the storage unit 10 and the building 65 thereby virtually eliminating the possibility of danger to an operator.

As is also shown in FIG. 3 detector units 66, here labelled as ionization chambers, may be located at one or more positions throughout the building 65. The detector units are of the time-integrating radiation detector types and they integrate all energy received by them throughout a test run of the source capsule 40 through the test loop 13. These units thus integrate all the energy received from every point ni the area under test. One example of suitable detection equipment is the Victorine model 362 pocket ionization chamber. This instrument, when charged to about volts, is capable of recording integrated doses of gamma radiation up to about 250 milliroentgens and is nearly energy independent and isotropic in its response to incident gamma radiation.

When symmetry techniques, as illustrated in FIG. 3, are used to reduce the area over which simulation is required, the simulated fallout pattern is laid out only around half the building while detection instruments are placed symmetrically right and left within the structure. Then, readings from such pairs of instruments are added to provide the same result that would have been achieved from a complete simulated field.

The principal approximation to true simulation arises from the fact that radiation fields can obviously not be extended to infinity. To try to estimate the effect of cutting off the distribution at a finite distance, experimental source distributions may be laid out in annular areas or rings concentric with the center of the building. Comparison of measured results with predicted values for each ring then assists in evaluating computed intensities for source fields lying beyond those actually laid out.

As will be appreciated, the test loop 13 can be laid out in any desired pattern and the speed of the source capsule 40 can be made to be uniform through it or varied as desired. For example the test loop can be laid out over the roof of a building or over the roof of a fallout shelter or around a ship or in a straight line depending upon the type of radiation pattern that it is desired to simulate. In View of the fact that the path of the test loop 13 can be laid out ahead of time without concurrently exposing an operator to radiation, the test pattern can be made to an arbitrary degree of complexity. Thus it is possible with the present invention to provide a more nearly exact simulation of fallout geometry than has previously been possible with other methods and means.

By using time-integrating radiation detectors at selected points within the structure, for example the house 60 or the building 65 being evaluated, the effective radiation is made to appear as arising from a line or an area source as desired. This has the advantage of averaging out local effects in the structure under test such as small apertures or anomalously large chunks of material, in much the same way as would occur under conditions of actual fallout.

Safety features not illustrated in the drawings may be adapted to the apparatus shown in FIGS. 1 and 2 as fol lows. The exhaust or return tube 28 which returns pump fluid to the reservoir 25 may contain a constriction near the coupling element 29 which reduces the internal diameter of this tubing so that the piston 45.1 cannot pass through it. In this way the piston 45.1 may be accurately located at the output end of the second channel 12 in the storage unit 10 at the end of a test run. Such a constriction is preferably placed in the exhaust tubing 28 so that when this tubing 28 is disconnected from the storage unit at the time the storage unit is reversed as above described, the piston and source capsule 40 can then be free for the start of another test run. In order to prevent the source capsule from accidentally falling out of the channel 12, one may apply a cap to the output end of the channel 12 at 12.1 or one may include a piston lock (not shown) at this end. Such a piston lock might, for example, be simply a screw-type plunger adapted to be turned until it passes across the output end 12.1 of the passage 12. A similar fitting may be adapted to the output end 11.11 of the first passage 11 in the storage unit and then these two fittings or piston locks will be available at each end as desired.

It is a matter of indifference whether the test loop 13 is filled with water before the start of a test run or not. If it is desired to fill the test loop with water before a test run is started, then the end 15 of the test loop can be disconnected from the storage unit and connected directly to a pump for this purpose.

The embodiments of the invention which have been illustrated and described herein are but a few illustrations of the invention. Other embodiments and modifications will occur to those skilled in the art. No attempt has been made to illustrate all possible embodiments of the invention, but rather only to illustrate its principles and the best manner presently known to practice it. Therefore, while certain specific embodiments have been described as illustrative of the invention, such other forms as would occur to one skilled in this art on a reading of the foregoing specification are also within the spirit and scope of the invention, and it is intended that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

What is claimed is:

1. Apparatus for simulating a radioactive fallout field uniformly distributed over a prescribed area comprising a portable container having a quantity of radioactive material of known strength, means for continuously moving said container through each of successive equal increments of said area in a fixed time for each of said increments, and isotropic radiation detector means of the time-integrating type located at least at one point fixed relative to said area.

2. Apparatus for simulating a radiocative fallout field arbitrarily distributed over a prescribed area comprising a portable container having a quantity of radioactive material of known strength, a continuous hollow conduit arrayed over at least a portion of said area in a prescribed spatial pattern, means for continuously propelling said container through said conduit, and istoropic radiation detector means of the time-inegrating type located at least at one point fixed relative to said area.

3. Apparatus for simulating a radioactive fallout field uniformly distributed over a prescribed area comprising a portable container having a quantity of radioactive material of known strength, a continuous hollow conduit uniformly arrayed over at least a portion of said area in a prescribed spatial pattern, means for continuously propelling said container through said conduit at a constant speed, and isotropic radiation detector means of the timeintegrating type located at least at one point fixed relative to said area.

4. An apparatus for simulating a radioactive fallout field arbitrarily distributed over a prescribed area, said apparatus comprising in combination, a portable container for a quantity of radioactive material of known strength, a continuous hollow conduit arranged over at least a portion of said area in a prescribed spatial pattern, a radioactive energy shielding body to which each end of said conduit is connected and having passage means in register with the ends of said conduit, hydraulic means for continuously propelling said container through said conduit at a controlled speed to and from said shielding means, said hydraulic means including at least one liquid pump coupled to said passage means, and isotropic radiation detector means of the time-integrating type located at least at one point fixed relative to said area.

5. Apparatus for simulating a radioactive fallout field arbitrarily distributed over a prescribed area, said apparatus comprising in combination, a portable container for a quantity of radioactive material of known strength, a conductive hollow conduit arranged over at least a portion of said area in a prescribed spatial pattern, hydraulic means for filling said conduit with a liquid and for continuously propelling said container through said conduit at controlled speed from end to end thereof, said hydraulic means including first and second pumps of relatively different pumping capacities coupled in parallel to said conduit, at least the lower capacity pump being of the constant volume type, valve means between each pump and said conduit for selectively and alternately uncoupling one of said pumps from said conduit, and isotropic radiation detector means of the time-integrating type located at least at one point fixed relative to said area.

6. Apparatus for simulating a radioactive fallout field arbitrarily distributed over a prescribed area, said apparatus comprising in combination, a portable container for a quantity of radioactive material of known strength, a radioactive shielding storage unit for initially holding said container, means for defining a continuous elongated passageway through said area according to a prescribed space increment pattern, the ends of said passageway terminating within said storage unit, hydraulic means for continuously moving said container through said passageway to and from said storage unit according to a prescribed time increment pattern, and isotropic, time-integrating radiation detecting means disposed at least at one point fixed relative to said area.

References Cited in the file of this patent UNITED STATES PATENTS 1,662,429 Lowy Mar. 13, 1928 2,760,517 Baum June 12, 1956 2,822,776 Morganstern Feb. 11, 1958 2,874,305 Wilson Feb. 17, 1959 2,965,761 Horvath Dec. 20, 1960

Claims (1)

1. APPARATUS FOR SIMULATING A RADIOACTIVE FALLOUT FIELD UNIFORMLY DISTRIBUTED OVER A PRESCRIBED AREA COMPRISING A PORTABLE CONTAINER HAVING A QUANTITY OF RADIOACTIVE MATERIAL OF KNOWN STRENGTH, MEANS FOR CONTINUOUSLY MOVING SAID CONTAINER THROUGH EACH OF SUCCESSIVE EQUAL INCREMENTS OF SAID AREA IN A FIXED TIME FOR EACH OF SAID INCREMENTS, AND ISOTROPIC RADIATION DETECTOR MEANS OF THE TIME-INTEGRATING TYPE LOCATED AT LEAST AT ONE POINT FIXED RELATIVE TO SAID AREA.

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