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 BEST COPY AVAILABLE Approved for public release;

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2. GOVT AC CC> SIOH HO Gamna Exposure Rate Versus Time PER FOR MI MGOWGAUIZ AT ION uAU.E AND AOORESS U.S. Army Signal Research and Develop Laboratory Fort Monmouth, New Jersey CO MT FAOLLIMG OFFICE UAUE AMO AOORESS Headquarters Field Conunand Defense Atomic Support Agency Sandia Base, Albuquerque, New Mexico Approved for public release; unlimited distribut” ,. TYPE OF REPoRT A PERIOO COVERED AREA & WURK UMIT UUUECRS This report has had the classified information removed and has been republished in unclassified forinfor public release. This work was performed by Kaman Tempo under contract DNAOO1-79-C-0455 with the close cooperation of the Classification l!anagm~nt Division of the Defense Nuclear Agency.

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This report has had classified material removed in order to make the information availeble 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 ([iT?R) Prc’cjram. The objective is to facilitate studies of the low levels of r~diation received by sme individuals during the ~ti;ospheric nuclear test program by n,zking as much information ~s pcssible availsble to all interested pat-ties. The naterial which has been deleted is all currently classified as Restricted Data or Fcrmerly Restricted Data under tile provision of the Atomic Eriergy Act of 1954, (as er,ended) or is I:?tional Security Inforrlation. This report has been rept-educed directly from available ccpies of the original material. The locations from winich ititerial has been deleted is generally obvious by the spacings ~nd “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 germtine to his study. It is the belief of tile individuals wno have participated in pr~ptiring this report by deleting the classified material :nd uf tile D~fcnse Nuclear },gency that the report accurately pot-trays the contents of the original and that the deleted n,a~erial is of little or no significance to studies into the siriountsor types of t-adiation received by any individuals ouring the atmospheric nuclear test program.

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Acmkoen George %kaee]ien Baktr Enyu Arriikan Yoke Bokonfuatiu Bern Innchebl Biglren mger Bokororyuru Bravo Nuiu. Bikini Atoll. Locations of test clctonatio!).s ciuring Operation Redwing with corresponding militar:; identifiers arc gi~~en in the talxilation.

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Eniwetok Atoll. Locations of test detonations during Operation Redwing are ind.ic ated 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 mc.isure initial- and residual-garnmaexposure 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 prototype thermal detector to be used in a radiological -defense-warning system. The residual -gamma radiation was detected hy m unsaturated-ion chamber, whose output determined the frequency of pulses that v;ere recorded o~~electro-sensitive paper. hlost of the initial-gamma-radiation stations consisted of scintillation detectors whose output determined the frequency of pulses that were recorded cm magnetic tape. Some initial-gamma instruments were similar to those used during Operation Castle. The Residual-gamma-exposure rate versus time was obtained after Shots Zuni, Flathead, Navajo, and Tewa. Ti)e observed average-decay exponents for these events were 1.1 for Zuni ti,d Tewa, 1.2 for Flathead, and 1.3 for Ntivajo. In some cases, the effect of rainfall in le:whing the activity decreased the exposure rate by a factor of two. Records from Shot Flathead at 7,730 fec~ and from Shot Navajo at 13,870 feet indicated that at these locations about 2L3of the total inltitil -g.lmm[a e,xpo,su).e was delivered after the arrivai of the shock front. no usable data was obtained. The thermal -racliation detector re spon(!ed satisfactorily to a detonation at a distxnce 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 this and the other military-effect projects can be obtained from WT - 1344, the “Summary Report of the Commander, Task [;nlt 3. “ This technical summary includes: (1) tables listing each detonation with its yield, type, environment, meteorological conditions, etc.; {2) maps showing shot locatlons; (3) discussions of results by programs; (4) summaries of objectives, procedures, results, etc., for all projects; and (5) a listing of project reports for the milib~ry-effect programs.

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Graph of gamma exposure versus distance for a ~i~e-kt Schematic diagram showing the basic circuit for the Graph showing a typica! calibration curve for the Conrad Graph showing typical calibration curves for the Gustave Energy dependence of Gustave I detector norrnalixec! to Co*” Schematic diagram showing the photomuitiplier feedback Residual exqmsure rate within blast shield versl.ls time for Shot Zuni; Station 221.03, range 69,600 feet --- ------------- 29 Unshielded residual exposure rate versus 1,me for Shot Residual exposure rate ver~us time for Shot Zurti; Unshiclcled residual exposure rate versus time for Shot Unshielded residual exposure rate versus :Ime for Shut Unshielded residual exposure r:tte versus time for Shot Residual exposure- rate within blast shield vers:ls time for Shot Flatheaci, Station 221.04, range 7,730 feet- ----------- 32 Residual exposure rate witi~ln blast snicid versus time for Shot I?lathead; Station 221.05, range I0,74L feet ----------- 33 Residual exposure rate within blast shield versus time for Unshielded residual exposure rt{te versus hme for Shot Unshielcled residual exqmsure rate versus time for Shot Unshielded residual exposure rate versus time for Shot Residual exposure rate> within blast shield versus time for Shot Navajo; Station 221.03, range 7,322 feet- --------------- 35 Residual exposure rate within blast shield versus time for Shot Navajo; Station 221.04, range 10,700 feet --------------- 36 Residual exposure rate v,,ithin blast shield versus time for Shot Navajo; Station 221.05, range 13,170 feet --------------- 36 Residual exposure rate versus time for Shot Tewa; ]iesidual exposure r: te within blast shield versus time for Shot Tewa; Station 221.03, range 17,550 feet ---------------- 37 Residual exposure rate within blast shield versus time for Shot Tewa; Station 221.04, range 22,220 feet --- ---------- ‘-- 38

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3.19 Map of Bikini Atoll showing unshielded residual exposures 3+20 Map of Bikini Atoll showing ~shielded residual exposures 3.21 Map of Bikini Atoll showing unshielded residual exposures for Shot Navajo --------------------------------”--- 3.22 Map of Bikini Atoll showing unshielded residual exposures for Shot Tewa ------------------------------------ 3.23 Shielded initial exposure rate versus time for Shot Zuni; 3.24 Shielded initial exposure rate versus time for Shot Flathead; Station 221.04, range 7,730 feet ------------------------ 3.25 Shielded initial exposure raie within Mast shield versus time for Shot Xavajo; Station 221.05, range 13,170 feet --------- 3.26 Shielded initial ex~osure versus time for Shot Zuni; Station 3.27 Shielded initial exposure versus time for Shot l?lathea~ 3.28 Snielcied initial exposure versus time for Shot Navajo; 3.29 Shielded initial ex~osure versus distance, Projects 2.1 3.30 Shieldcci initial exposure versus distance, Projects 2.1 and 2.2, Shots Flathead and Navajo ---------------------- 3.1 Shot Zuni Instrumentation and Residual-Exposure Information ------- 41 3.2 Shot Flatheiid hlstrurnentation and Residual-Exposure 3.3 Shot Navajo Instrumentation and Residual-Exposure 3.4 Shot Tcwa Instrumenlmion and Residual-Exposurs

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The primary objectives of Project 2.2 v.,cre: (1) to measure the initial-gamma-exposure rate as a function of time from the c,ietoniition of Iiigh-yield-the rmonuclear devices; and (2) to measure the residl]al-gamma -exposure rate as a function of time at land fallout stations. Secondary objectives wc re: (1) to measure residual radiation at early times on the crater lip of a high-yield, land-surface shot; md (2) to field test a prototype thermalradiation detector to be used in a radiological -de fense-warniriig system. versus time for high-yield cie~’ices duriag Operation Ivy (Reference 1). It was found that high-yield devices clid not follow i he relatively simple scaling laws of low-yield devices. Gamma radiation at c. particular distance scales linearly with yield for devices up to about 100 kt. For megaton-range devices, gamma radiation scales higher with iricreasing yield. This enhance mt:n! of initial -g:lmma radiation was attributed largely to the hydrodynamic effect (Section 1. 3.4). U. S. Army Signal Research and Development from high-yield devices during [lperatioa Castle (Reference 2). The data obtained by One of the purposes of Project 2.2 w~.$ to resolve the initial -gamma-radiation-scaling would allow correlation of the hydrodynamic effect from an airburst with that from a because of a high loss of instruments curly in the op:’ration. These data indicated that the decay exponent for the re siclua! activity varicci with the type of nuclear device. Another purpose of Project 2. z was to determine ticeurate decay exponents for residual activity. tests were successful. The tietector showed a capability far in excess of the requirements. It was decided to dete rntine the response of this detector to megaton-range devices during Operation Redwing in ord~! r to complete the testing. The gamma radiation ernittecl 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 rxliation from both fallout and neutron-induced activity. 1.3.1 Initial -Gamma Radiation. For a fission-type device the initial radiations are div~d 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). The N14 (n, y) gammas become relatively more important at greater distances, and eventually become the major contributor. This applies only to devices with yields of less than 100 M, in ‘which the hydrodynamic effect is small. Figure 1.1 shows the contribution TABLE 1.1 ENERGY PARTITION IN FISSION Kinetic Energy of / Fission Product Gammas \ 2“7 I 5.4 Fission Product Betas \ 2.7 1 * Mostly absorbed in the device. gamw as, however, continue to contribute for the first 3b sec:~nds. For thermonuclear devices, in addition to gamma radiation from fission-product gammas, it is necessary to consider the inter~ction of neutrons from the fusion process with Nid. The radiation due to the fusion process may vary over wide 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 there fore 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: + = exposure rate at time t II = 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 ill ustration shows the co,ltribution from fission-procitict gammas. amp!e, the presence of Np23g 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 e~}~ntial with distance. From a point source of mono-energetic radiz. ticm, the variation of intensity with distance is ex~ressecl as: intensity at distance D total Ii near absorption coefficient ( this coefficient generally decreases with incre:,sing gamma energv)

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The absorption coefficient p in Equation 1.2 is applicable for narrow-beam geometry, and a correction shoul{! be made for field conditions where the detector is approximately a 27Tsensing 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 omni-directional 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 100-kt yield, essentially all of the initial-gamma radiation is emitted before the shock front can produce an appreciable change in the effective TABLE 102 CALCULATED BUILDUP FACTORS The buildup factor (B) given here is the factor Br (MOD, Eo) as computed by Nuclear Development Associates for AFSWP @efe rence 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 VOand radius R, and is filled with a gas of density PO and mass M. Then, Let the gas be compressed into a shell with thickness AR (R remaining constant). The new gas volume is expressed as Vi (Vl = imR2 AR) with a density of pi. 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 1/3of 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*4 (n, Y) component is not significantly enhances. The fission-product gamr,:as continue to contribute during the first 30 seconds; therefore, this radiation is strongly enhanced by the

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placed in previously prepared positions :~t the latest practic:lble time prior to each shot and Ivere recovered postshot as soon as Natl-%fe ~on{htions permitted. The residual stations were activated upon placcme nt. Their 5-day owrating period aliowed for 2 days of data -recorclillg and three 1-d~y s},ot deluys. For the surface bursts, the initial stations were :w: ivatet.1 by a minus -1-mi,lute-tirning signal for warmup, and a minus15- second sigil:il to start the recordc r. Shot Zuni ilas an exception; only a minus-lthe initial stations because cIf the limited recording time available (Cook Research Labor: itory MR 33 recorders, 4 minutes; Sanborn recorders, 15 minutes). For Shot Cherokee, the recordc rs were noL st:trted until after the device release. In desigmng lr:s!r~ln~entation for this prujcct, there w’ere two objectives: (1) to design ily ad:q~t:lble to L ivicle v:i riety uf field ]jwusuremt’nts. In view of this dwd objective, the charge. Essentially, this circ’.~it could be used with :my sensing element that had an output which was u kncwn function oi’ the radiation field. 1 bus, the circuit was …