Operation Castle - Project 2.7, Distribution of Radioactive Falloutby Survey and Analyses of Sea Water (Deleted)

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Distribution of Radioactive Fallout By Survey and Analyses of Sea Water Headquarters Field Command Armed Forces Special Weapons Sandia Base, Albuquerque, New This is an extract of WT-935, Operation CASTLE, which remains classified SECRET/RESTRICTED DATA as of Extract version prepared for: DEFENSE NUCLEAR AGENCY Approved for public release;

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Operation CASTLE - Project 2.7 Distribution of Radioactive Fallout by Survey and Analyses of Sea Water Headquarters Field Command Armed Forces Special Weapons Project Sandia Base, Albuquerque, New Mexico Approved for public release; unlirliteddistribution. BEFORE COMPLETING FORY 5. TYPE or RLPORT & PCRIOO COVERLO 10. PROGRAU ELEUENT. PROJECT. TASK AREA & UORU UNIT NuUf3ERS 11. UUUBER OF PAGES This report has had the classified information removed and has been republished in unclassified form for public release. This work was performed by Kaman Tempo under contract DNAOOl-79,-C-0455with the close cooperation of the Classification Management Division of the Ilefense 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 (NTPR) Program. The objective is to facilitate studies of the low levels of radiation received by some individuals during the atmospheric nuclear test program by making as much information as possible available to all interested parties. The material which has been deleted is all currently classified as Restricted Data or formerly Restricted Data under the provision of the Atomic Energy Act of 1954, (as amended) ,or is National Security Information. This report has been reproduced directly from available copies of the original material. The locations from which material has been deleted is generally obvious by the spacings and "holes" in the text. Thus the context of the material deleted is identified to assist the reader in the determination of whether the deleted information is germane to his study. It is the belief of the individuals who have'participated in preparing this report by deleting the classified material and of the Defense Nuclear Agency that the report accurately portrays the contents of the original and that the deleted material is of little or no significance to studies into the amounts or types of radiation received by any individuals during the atmospheric nuclear test program.

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GENERAL SHOT INFORMATION Shot I Shot 2 Shot 3 Shot 4 Shot 5 Shot 6 DATE I March 27 March I 7 April 26 April 5 Moy 14 Moy Bikmi, West of Chorlre ( Nomu) Bikini, Shot I on Reef ; Croter TYPE Lond Barge Land Barge Barge Barge

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Oceanographic-survey and water-sampling techniques were employed to evaluate the amount and distribution of the fallout received over extended areas adjacent to nuclear detonations of high yields. The project was established as a result of the fallout phenomena observed following Shot 1. The operational and technical details had to be hastily contrived so that they could be put into effect within the latter phases of Operation Castle. Specifically, the experimental studies reported herein were conducted in connection with Immediately following Shot 5, a fleet tug carrying improvised radiographic and oceanographic gear cruised the oceanic area downwind of Bikini Atoll, covering 800 miles in four days, taking samples of the water at the surface and to depths of 2,400 feet, and measuring gamma ray intensities above the sea surface and also just below the sea surface. Cccasionally the gamma intensity was measured to 80 meters depth also. Two samples of open-sea plankton were netted and found to be strongly radioactive. Following Shot 6, two tugs cruised downwind of Eniwetok Atoll taking surface water samples and measuring gamma intensity at each level; simultaneously, the area was surveyed by aircraft carrying sensitive gamma detectors. Two survey results recommend the continued use and perfection of the novel techniques. Analysis of data indicates that, for a surface water detonation of a high-yield weapon, an area of approximately 5,000 square miles can be covered by contamination at levels that would be hazardous to human life if the fallout had been deposited on a comparable land area; that is, over this area the total gamma ray dose accumulating during the first 50 hours would be about 250 r at a height of 3 feet above a plane fallout catchment.

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This is a record of eqerimental data required following Shot 5 Castle together with a careful xx-evaluation of its Significance. A preliminary report was put together under great pressure and Shot 6 of Operation just following Operation Castle (and circulated in limited numbers as ITR-935, May 1954). There had been no time for thorough consultation between the collaborating organizations; certain computations were still not completed; in fact, the final calibration of gamma instruments had not been completed because the instruments themselves disappeared for several weeks in the course of transportation. The evaluation of the direct gamma measurements and oceanographic measurements was carried out at Scripps Institution of Oceanography; the analysis of water samples and their evaluation has been carri d out at U. S. Naval Radiological Defense ,Laboratory. Attempts have been made to integrate the effects at each institution. The authors wish to accord special acknowledgment to Feenan D. Jennings of Scripps Institution of Oceanography for his outstanding contributions during the cruise and in the analyses, and to John D. Isaacs and Roger R. Revelle of the same institution for their useful guidance during the planning phases prior to Shot 5. logical Defense Laboratory, who participated in the Shot 5 survey; and to many individuals of the NRDL and SIO staff who assisted in this study. Mrs. Suzanne Volkmann of the SIO staff has contributed extensively during the past year to the analyses and editing of the The facilities and experience of the U. S. Bureau of Standards were made available to SIO for the calibration of the gamma devices. The authors are grateful to L. S. Taylor, Harold Wyckoff and S. W. Smith of that institution. Finally, the success of this experiment owes much to the assistance of many individuals of Joint Task Force Seven for providing equipment and a generous amount of personal time and good will.

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This report is one of the reports presenting the results of the 34 projects participating in the Military Effects Tests Program of Operation Castle, which included six test detonations. For readers interested in other pertinent test information, reference is made tary Effects Program. This summary report includes the following information of possible general interest: (1) an overall description of each detonation, including yield, height of burst, ground zero location, time of detonation, ambient atmospheric conditions at detonation, etc., for the six shots; (2) discussion of all project results; (3) a summary of each project, including objectives and results; and (4) a complete listing of all reports covering the Military Effects Tests Program.

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2 .1.2 Calibration of Instruments ________________-____-___---- 18 2.3 Supplementary Oceanographic Measurements ___________-________ 23 CHAPTER 3 RESULTS OF SURFACE AND SUBSURFACE SURVEY BY RADIATION DETECTING 3.4 Computation of Synoptic Picture ____________________~~~~~~~~~ 32 Computations of Total Local FaIlout ----------------------- 35 Estimate of Radioactive Decay_~-~~~~~~--~-~~--~-~-~~__~_ 35 Local Dose at 3 Feet Elevation at the Synoptic Local Dose at 3 Feet Elevation at the Synoptic Effect of Time of Arrival and of Ocean Currents Plotting Fallout Contours of Iso-Dose-Rate ___-______________ 46 Plotting Fallout Contours of Total Dose--------------------- 52

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CHAPTER4 ANALYSIS OF CONTAMINATED SEA WATER -------------- 53 Calculation of A-Gamma Activity Received Per Unit Calculation of I/A-Ratio of Gamma Ionization Readings to Gamma Counts _____-----------____~~~~~~~~~~~~~~~ 63 Calculation of R/I-Ratio of Gamma Energy Emission Rate Per Unit Area to Gamma Ionization Reading Per Unit Area ,__-i---------------,,,,,,,,,,_,,,,,, 63 Calculation of Reference Dose Rate, dr ------------------------ 67 Calculation of Dose Rate, d ---------------__-__----____-___ 68 Calculation of Dose Rate d From Observed Gamma Fraction of Shot 5 and Shot 6 Devices in Fallout ---------------I-- 71 CHAPTER 5 SUMMARY, DISCUSSION AND CONCLUSIONS -------------- 77 5.2 Discussion and Conclusions ---------_____~____^~~~~~~~~~~~~ 77 APPENDIX A COMPARISON OF COMPUTED DOSE RATE OVER THE SEA WITH CERTAIN ACTUAL MEASUREMENTS--------- 79 APPENDIX B PROCEDURE USED IN CHAPTER 3 FOR ESTABLISHING THE CALIBRATION OF THE TOWED INSTRUMENTS FOR MEASURING GAMMA RAYS UNDERWATER ------------ 81 Estimates of the Source Spectra-------------------------- 83 Calculations of the Underwater Dose Spectra Corresponding to the Assumed Fallout Source Spectra-----------------,---- 83 Instrument Response Variation Due to Photon Energy Instrument Response Variation Due to Angle of Incidence Response of Mark II to Distributed Sources Comprised of wed Fallout Materials _________-____-__~_-~~---~__~~ 87 Derivation of Complete Response Curves for the Instrument APPENDIXC COMPUTATION OF DOSE AT THREE FEET C.1 Computation of Dose at Three Feet Elevation From Measurements of Dose in Water ------------------------- 88

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&terna_l configuration of towed gamma detector, Nark II __---------- Mark I calibration from distant point source of radium, Mark III calibration from distant point source of radium, Site Elmer Rad-Safe compound, 10 May 1954 ---;------------ Mark I, II, ,I& towed detector data, Shot 5 _____________________ “Pot” record in mr/hr showing correction for accumlllated Relative radiation intensity along ship’s track, Shot 5 MarkII vertical radioactivity profiles, Shot 5-- ------------------ Accumulated dose factor ____--______________~~~~~~~~~~~~~~ Estimated time of arrival of fallout from an analysis Ocean current vectors frcun Japanese hydrographic investigations, 3.10 Ocean current buoy drift data, October-November 1952 and 3.12 Total dose from time of fallout to H + 50 hours in roentgens, Calculateddecay (d/m) for Shot 6 fallout ----------------------- 58 Estimated times of arrival of fallout -------------------------- 62 Relative response of NRDL ion chamber with incident Calculated decay (d/m) for Shot 5 fallout ----------------------- 69 Estimated fallout dose rate contours for Shot 6 at H + 12 hours Location of instruments during Shot 5 ------------------------- 79 Histograms of estimated source spectra ----------------------- 82 Histograms of degraded dose spectra ------------------------- 84 Experimental response of Mark II for rays at 90 degrees Variation in response of Mark II with angle of incidence Plotofdata from Table B.4-------------------------------- 85 Schematic of reduction of readings to dose rate (mr/hr) at 3 feet elevation ______-___________-_~~~~~-~~-~~~~~ 91

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Estimation of Time of Arrival of Fallout From An AnaIysis Computation of Dose Rate and Accumulated Dose 3 Feet Above a Hypothetical Plane Catching the Fallout Iso-dose Rate Contours at 3 Foot Elevation -___ _________________ 51 Radioactivity in Water Samples From Shot 5--------------------- 56 Ratio of Gamma Ionization Readings, I To Gamma Counts, Calculation of R/I Ratio of Gamma Energy Emission Rate Per Calculation of Reference Dose Rate, dr at Height X = 3 Feet Above An Infinitely Contaminated Plane Having a Gamma Dose Rate at H + 12 Hr Calculated From Water Samples Dose Rate at ‘H + 12 Hr Calculated From Water Samples Total Beta Activity in Shot 5 Fallout at 9 Days ------------------- 72 Total Beta Activity in Shot 6 Fallout at 7 Days-------------------- 72 4.11 Beta Disintegrations and Gamma Photons Per Minute Per Fission and EstimatedP/yRatio---------------------- 75 4.13 Total Beta Activity From Devices and the Fraction of Total Beta Activity in the Fallout Shot 5 and Shot 6 Comparison of Shot 5 Gamma Field Intensities at 12 Hours L -- ------ -- 78 Above Surface and Below Surface Survey Data and Their Estimated Source Spectra _-__--_______--_____~~~~~~~~~~~~~~ 82 Effective Response Sensitivity of Mark II to Estimated Response to Uniform 4 Pi Distribution of Sources Over a Spherical Shell Relative to the Same Sources Concentrated at a Point at the Same Radius and on the Normal to theInstrument’s Axis ---------------------- 86 Computed Responses of Mark II to Uniformly Distributed Computation of Dose at Three Feet Elevation Above Fallout Plane By Method of AFSWP Report 502A ------------------- 90

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Attempts were made during Operation Castle to study the fallout patterns from nuclear devices detonated at the surface over land and water. Most of the fallout from the nuclear devices was distributed over extended occ::.~: zrt 1s out5de the atolls on which the weapons were detor.ated. It was desired to de:ermir 1~‘wil:35 the radiation levels would have been had the radioactive material from the tnrf devicl.:s fallen on extended land areas. Study of Shot 1 made cle’ar that observation of fallout on subsequent shots over larger areas was necessary. On Shot 5 alternative methods were attempted. The Division of Biology and Medicine (DRM) of the Atomic Energy Commission used airborne gamma detectors to measure activity on raft,s. Oceanographic surveys were mounted by the Scripps Institution of Oceanography (SIO) and Naval Radiological Defense Laboratory (NRDL) involving submerged counters and water sampling. Studies of these data showed need for modified techniques to give a faster synoptic survey for the remaining shot, Shot 6. This was done by limiting the observations to above-surface monitoring and surface-water sampling in conjunction with a synoptic aerial survey. The ultimate objective of the work described herein was to provide data for the determination of the amount and distribution of fallout received by ocean areas surrounding the site of a surface nuclear detonation. This information is of particular interest when related to the gamma field intensities which would exist if the fallout were received by The initial objective of the work described under Project 2.7 was to evaluate the feasibility of using oceanographic surveys and sampling techniques as a means of providing radiological information. The specific objectives were to: (1) determine the distribution in ocean water of the major fallout downwind; (2) measure depth and rate of mixing of fallout; and (3) collect otherwise-unattainable specimens, technical data, and field experience essential for the success of future operational planning and instrumentation. This study was initiated by the Headquarters, Armed Forces Special Weapons Project’s (AFSWP) suggestion that water sampling and survey techniques could be used to estimate the fallout contours. The techniques adopted, following consultation between representatives of AFSWP, NRDL, and SIO, consisted of water sampling and surveys using submergible radiation instruments at several depths. The method was based upon the existence well known by oceanographic measurements of a uniformly mixed surface-water layer. Such a layer presumably is created by the

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action of wind and, waves. There is evidence that mixing may be complete within 6 few hours to a depth, in this area, of 300 feet or more. The lower boundary of this mixed layer frequently appears as an abrupt drop in temperature. Mixing is thorough in the upper layers as evidenced by the remarkable uniformity of temperature between this boundary, called the thermocline, and the surface. It was expected therefore that the radioactive fallout would also become evenly dist+ buted throughout the mixing layer to an extent which might permit estimation of the amount of fallout by measurement of the radioactivity of oceanwater in the mixed layer. The portion of the above investigations orgnllized and performed under the direction of Task Unit 13, Program 2, was established as a separate joint SIO and NRDI, project, project 2.7. SIO has evaluated the direct gamma measurements. NRDI, has analyzed the water samples. In this report an attempt has been made to construct approximate fallout contours and calcuIate gamma field intensities on the basis of the data obtained by these two methods.

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For the survey following Shot 5, the ATF-75 (Sioux) was hurriedly fitted with hydrographic gear and with improvised radiation detectors …