Operation Redwing - Project 2.2, Gamma Exposure Rate Versus Time (Deleted)

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Gamma Exposure Rate Versus Time Pacific Proving Grounds Headquarters Field Command Defense Atomic Support Agency Sandia Base, Albuquerque, New Mexico This is an extract of WT-1311, Operation REDWING, Project 2.2, which remains RESTRICTED DATA as of this date. Extract version prepared for: DEFENSE NUCLEAR AGENCY

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Operation REDWING - Project 2.2 Gama Exposure Rate Versus Time U.S. Army Signal Research and Develop Laboratory Fort Monmouth, New Jersey Headquarters Field Command Defense Atomic Support Agency Sandia Base, Albuquerque, New Mexico Approved for public release; unlimited distribution. S. TYPE OF REPORT L PERIOD COVERED IO. PROGRAM ELEMENT. PROJECT. TASK AREA b WORK UNIT NUMBERS 13. NUMBER OF PAGES [his report has had the classified information ren:ovedand has been republished in unclassified forinfor public release. This work was performed by Kaman Tempo under sontract DNAOOl-79-C-0455 with the close cooperation of the Classification 'lanarJcmentDivision of the Defense Nuclear Agency.

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This report has had classified material removed in order to . make the information available on an unclassified, open publication basis, to any interested parties. This effort to declassify this report has been accomplished specifically to support the Department of Defense Nuclear Test Personnel Review (I;TPR) Program. The objective is to facilitate studies of the low levels of radiation received by scme individuals during the at;;iosphericnuclear test program by r;;ckingas much information as pcssible availzble to all interested parties. The rr:aterialk:hich has been deleted is all currently classified as Restricted Dita or Fcrmerly Restricted Data under the provision .of the Atomic Energy Act of 1354, (as azended) or This report has been reproduced directly from available ccpies of the original material. The locations from which ;;aterial has been deleted is generally obvious by the spacings 2nd "iloles" in the text. Thus the context of the material deleted is identified to assist the reader in the determination of ;;hether the deleted information is germane to his study. It is the belief of the individuals klho have participated end of l_he Defense Kucleur Agency that the report accurately portrays the contents of the original and that the deleted r;,aterialis of little or no significance to studies into the c;sounts or types of radiation received by any individuals curing the atmospheric nuclear test program.

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Bikini Atoll. Locations of test dctonatiol- ,.s during Operation Redwing are indicated by large !ettering and arro??:s. Native island names with corresponding military identifizs arc given in the tabulation.

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Eniwetok Atoll. Locations of test detonations during Operation Redwing are indicated by large lettering and arrows. Native island names with corresponding military identifiers are given in the tabulation.

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The primary objective of Project 2.2 was to measure initiai- and residual-gammaexposure rates as a function of time at various distances from high-yield-thermonuclear detonations. Secondary objectives were to measure the residual gamma-exposure rate at the lip of the crater from a high-yield, land-surface shot; and to field test a protot_ype thermal detector to be used in a radiological-defense-warning system. The residuul-gamma radiation was detected by an unsaturated-ion chamber, whose output determined the frequency of pulses that v.:ere recorded 011electro-sensitive paper. Most of the initial-gamma-radiation stations consisted of scintillation detectors whose output determined the frequency of pulses that were recorded on magnetic tape. Some initial-gamma instruments were similar to those used during Operation Castle. The exposure rate near the crater was measured with a detector-telemeter unit dropped Residual-gamma-exposure rate versus time was obtained after Shots Zuni, Flathead, Navajo, and Tewa. The observed average-decay exponents for these events were 1.1 for Zuni and Tcwa, 1.2 for Flathead, and 1.3 for PLvajo. In some cases, the effect of rainfall in leaching the activity dccrensed the exposure rate by a factor of two. Records from Shot Flathead at 7,730 fecr and from Shot Navajo at 13,870 feet indicated that at these locations about 2/3 of the tot:11 initial-gamma e,xposure was delivered after the arrival of the shock front. The crater-lip measurements indicated that the method was a feasible one; however, no usable data was obtained. The thermal-radiation detector res;)on:!ed satisfactority to a detonation at a distance of 20 miles.

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This report presents the final results of one of the projects participating in the militaryeffect programs of Operation Redwing. Overall information about #is and the other military-effect projects can be obtained from WT - 1344, the “Summary Report of the Commander, Task Lnlt 3.” This technical summary includes: (1) tables listing each detonation with its yield, type, environment, meteorological conditions, etc.; (2) maps showing shot locations; (3) discussions of results by programs; (4) summaries of objectives, procedures, results, etc., for 311 projects; and (5) a listing of project reports for the military-effect programs.

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2.2.4 Photomultiplier Feedback Circuit, lnitial Instrument Readout Error tid Accuracy of the Gustave and CHAPTER 3 RESULTS XND DISCUSSION ------------------------- 28

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1.1 Graph of gamma exposure versus distance for a one-kt 2.1 Schematic diagram showing the basic circuit for the Conrad and Gustave detectors-------------------------- 20 2.2 Graph showing a typica! calibration curve for the Conrad 2.3 Graph showing typical calibration curves for the Gustave 2.4 Energy dependence of Gustave I detector normalized to Co6’ 2.5 Schematic diagram showing the photomuitiplier feedback 3.1 Residual exT0sm.e rate within blast shield versus time for 3.2 Unshielded residua1 esposure rate versus t&me for Shot 3.3 Residual exposure rate versus time for Shot Euni; 3.4 Unshielded residual e?cposure rate versus time for Shot 3.5 Unshielded residual exposure rate versus rime for Shot Zuni; Stlltion How, range 78,OOO feet --------------------- 31 3.6 Unshielded residual exposure rate versus time for Shot 3.7 Residual exposure rate within bl:ist shield versus time 3.8 Residual c.xposure rate within blast sniclf! versus time XI) Residual exposure rate within blast shield versus time for 3.10 Unshielded residual exposure rate versus time for Shot 3.11 Unshielded residual exposure rate versus time for Shot 3.12 Unshielded residual exposure rate versus time for Shot 3.13 Residual exposure rate within blast shield versus time for 3.14 Residual exposure rate within blast shield versus time for 3.15 Residual exposure rate within blast shield versus time for 3.16 Hesidual exposure rate versus time for Shot Tewa; 3.1’7 Residual exposure r’sic within blast shield versus time for 3.18 Residual exposure rate within blast shield versus time for

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3.19 Map of Bikini Atoll showing unshielded residual exposures 3.20 Map of Bikini Atoll showing unshielded residual elcposures 3.21 Map of Bikini Atoll showing unshielded residual exposures 3.22 Nlap of Bikini Atoll showing unshielded residual exposures 3.23 Shielded initial exposure rate versus time for Shot Zuni;. . Station 220.096, range 7,000 feet ----------------------- 3.24 Shielded initial exposure rate versus time for Shot Flathead; Station 221.04, range 7,730 feet -------,-_~,---,,--,-,-- 3.25 Shielded initial exposure rate within blast shield versus 3.26 Shielded initial exposure versus time for Shot Zuni; Station 3.27 Shielded initial exposure versus time for Shot Flathead; 3.28 Shielcied jnitial exposure versus time for Shot Navajo; 3.29 Shielded initial exposure versus distance, Projects 2.1 and 2.2, Shot Zuni ____________________~~~~~~~~~~~~~ 3.30 Shield& initial exposure versus distance, Projects 2.1 1.1 Energy Partition in Fission -____-_---___--_~_~_~~~~~~~~~~ 14 3.2 Shot Flathead Instrumentation and Residual-Exposure 3.3 Shot Navajo Instrumentation and Residual-Exposure 3.4 Shot Tcwa Instrumentation and Residual-Exposure

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The primary objectives of Project 2.2 \:‘cre: (1) to measure the initial-gamma-exposure rate as a function of time from the detonation of high-yield-thermonuclear devices; and (2) to measure the residual-gamma-exposure rate 2s a ftmction of time at :and fallout stations. Secondary objectives were: (1) to measure residual radiation at early times on the crater lip of a high-yield, land-surface shot; and (2) to field test a prototype thermalradiation detector to be used in a radiological-defense-warning system. LOS Alamos Scientific Laboratory (LXX) measured initial-gamma-exposure rate versus time for high-yield devices durmg Operation Ivy (Reference 1). It was found that high-yield devices did not follo\i the relatively simple scaling laws of low-yield devices. Gamma radiation at a particular distance scales linearly with yield for devices up to about 100 kt. For megaton-range devices, gamma radiation scales higher with increasing yield. This enhancement of initial-g:mima radiation was attributed largely to the hydrodynamic effect (Section 1.3.4). U. S. Army Signal Research and Development Laboratory (USASRDL) obtained several gamma-exposure-rate-versus-time data points from high-yield devices durin, e Operation Castle (Reference 2). The data obtained by USASRDL were lower by a factor of 10 or more than the Super-Effects Handbook predicOne of the purposes of Project 2.2 was to resolve the initial-gamma-radiation-scaling laws for high-yield devices. Of pnrticular intcrcst was a high-yie!d air burst, since it would allow correlation of the hydrodynamic effect from an airburst with that from a surface burst. IYSASRDL made measurements of residual-gamma-e.xposure rates from high-yield devices during Operation CXZIC (Reference 2 ). Only bmited data were obtained because of a high loss of instruments early in the oiJc!ration. These data indicated that the decay exponent for the residual activity varied with the type of nuclear device. Another purpose of Project 2.2 was to determine accurate decay exponents for residual activity. tests were successful. The detector showed a capability far in excess of the requirements. it was decided to determine the response of this detector to megaton-range devices during Operation Redwing in order to complete the testing. The gamma radiation emitted from a nuclear cictonation may be divided into two por-

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tions: Initial radiation and residual radiation. The residual radiation may include radiation from both fallout and neutron-induced activity. 1.3.1 Initial-Gamma Radiation. For a fission-type device the initial radiations are divided approximately as shown in Table 1.1 (from Reference 5). The major contribution to initial-gamma radiation is from the fission-product gammas and the gamma radiation gammas are nearly all absorbed in the device itself and are of little significance outside of the device. The fission-product gammas predominate at close distances (Reference 5). tually become the major contributor. This applies only to devices with yields of less than 100 kt, in which the hydrodynamic effect is small. Figure 1.1 shows the contribution TABLE 1.1 ENERGY PARTITION IN FISSION Mechanism nt oi Totaq Total Energy Fission Energy per Fission Kinetic Energy of 1 k Fission Product Gammas Fission Product Betas Fission Product Neutrinos * Mostly absorbed in the device. time, the N’* (n, y) radiation is essentially emitted within 0.2 second; the fission-product gammas, however, continue to contribute for the first 36 secnnds. For thermonuclear devices, in addition to gamma radiation from fission-product gammas, it is necessary to consider the interaction of neutrons from the fusion process with N14. The radiation due to the fusion process may vary over Kide limits, depending on the design of the device. For a given yield, the number of neutrons available may be ten times’as great for fusion as for fission, and therefore a large contribution to gammaradiation exposure may be due to the N14 (n, y) reaction in a thermonuclear device (Refproduct radiation from fallout and radiation from neutron-induced activity. The decay rate of the residual radiation from fallout will follow approximately the expressions:

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Where: It = exposure rate at time t I1 = exposure rate at unit time The decay of the residual radiation is expected to vary with device design. For exFigure 1.1 Graph of gamma exposure versus distance for a one kt surface burst. This illustration shows the contribution from fission-product gammas. ample, the prescnco of N,:P~~’would tend to decrease the absolute value of the decay exponent for a period of time. 1.3.3 .Absorption in Air. The absorption of unscattered gamma radiation in air is exponential with distance. From a point source of mono-energetic radiation, the variation of intecsity with distance is eqressed as: intensity at distance D total linear absorption coefficient (this coefficient generally decreases with increasing gamma entrgv)

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The absorption coefficient p in Equation 1.2 is applicable for narrow-beam geometry, and a correction shoult! be made for field conditions where the detector is approximately a 2~ sensing element. This is done by adding a buildup factor B to Equation 1.2 to account for the scattered radiation that will be detected. Buildup factors for different energies and distances have been calculated (Reference 6), and some values are shown in Table 1.2. For omnidirectional detectors, the expression is: 1.3.4 Hydrodynamic Effect. As shown in Section 1.3.3, the attenuation of gamma radiation is highly dependent on the amount of absorber between the source and the detector. For devices of less than lOO-kt yield, essentially all of the initial-gamma radiation is emitted before the shock front can produce an appreciable change in the effective TABLE 1.2 CALCULATED BUILDUP FACTORS computed by Nuclear Development Associates for AFSWP (Reference 6). Mev Yds yds yds absorption of the air between source and detector. For high-yield devices, the velocity of the shock front is sufficiently high to produce a strong enhancement of a large percentage of the initial-gamma radiation (Reference 7). The higher the yield, the larger is this percentage. A simplified treatment of the hydrodynamic effect follows. Assume a sphere that has a volume V. and radius R. and is filled with a gas of density Let the gas be compressed into a shell with thickness AR (R remaining constant). The new gas volume is expressed as Vr (Vi = 4nR2AR) with a density of ~1. The mass has not changed; thus,

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Equation 1.6 indicates that a ray originating in the center of the sphere would traverse only l/s of the mass in the shell model that it would in the homogeneous model. The result would be an enhancement of radiation. Once the shell of material in the shock front passes the detector, an even greater enhancement results. As previously stated, the N” (n, Y) component of initial radiation is essentially emitted within 0.2 second. Since it takes at least one second for the shock front to reach a detector at a distance of 7,000 feet (even for devices in the order of 6 Mt), the N” (n, y) component is not significantly enhances. The fission-product gammas contmue to contribute during the first 30 seconds; therefore, this radiation is strongly enhanced by the

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Table 2.1 lists shot participation and instrumentation. The instrument stations were placed in previously prepared positions at the latest practicnble time prior to each shot and were recoverd postshot as soon as Had-Safe LonAtions permitted. The residual stations were activated ui,On placement. Their 5-day ouerating period aliowod for 2 days of data-recorcl;11& and three l-day shot delays. For the surface bursts, the initial statlons were activated by a minus-l-mi;lute-timing signal for warmup, and a minus15-second sig:lnl to start the recorder. Shot Zuni was an esception; only a minus-lsecond signal was :;vaiI,lble to start the recorder. Timing signals were necessary on the initial stations beI:ause of the limited recording time available (Cook Research Laboratory MR 33 recorders, 4 minutes; Sanborn recorders, 15 minutes). For Shot Cherokee, the recorders were noL started until after the device release. In designing Ir-~s~ri~lnentation for this project, there were two objectives: (1) to design ily ad:lpt:lble to L wide vzriety ibf field IiieasUrenl~!nt:~. In view of this dusl objective, the instruments ~vt?re designed to be compact, drift-free, reliable, wide in dynamic-range coverage, and io\v in cost. The basic circuit evolved mensured di!;creLe increments of charge. Essentially, this circuit could be used with any …