Survey of Radioactivity in the Sea Near Bikini and Enewetak Atolls June 11-21, 1956

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HEALTH AND SAFETY UNITED STATES ATOMIC ENERGY COMMISSION SURVEY OF RADIOACTIVITY IN THE SEA NEAR BIKINIAND ENIWETOK ATOLLS Technical Information Service Extension, oak Ridge, Term.

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Date Declassified: November 28, 1956. This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatue, method, or process disclosed in this report. As used in the above, “person acting on behalf of the Commission” includes any employee or contractor of the Commission to the extent that such employee or contractor prepares, handles or distributes, or provides access to, any information pursuant to his employment or contract with the Commission. This report has been reproduced directly from the best available copy. Printed in USA. Price 30 cents. Available from the Office of Technical Services, Department of Commerce, Washington 25, D. C. AEC Technical Information Service Extension

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SURVEY OF RADIOACT~~ IN THE SEA NEAR BIKINI AND ENIWETOK A!IX)LLS Applied Fisheries Laboratory University of Washington Operated by the University of Washington under Contract No. AT(45-1)540 with the IJnltedStates Atomic Energy Commission

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During the period of June 11 to 21, 1956, a survey party, operating from the USS Walton (DE 361), measured the radiation in plankton, water, and fish samples collected near Bikini and A continuous record of the radiation in the surface water was obtained with a probe. Plankton samples from oblique tows to a depth of 200 meters and water samples from the surface and from depths of 25, 50, 75, and 100 meters indicated radioactivity at each station. Highest radiation readings In plankton and water samples were from stations north of Bikini Atoll. Radiation decreased around the periphery of the survey area.

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Plans, Equipment and Operations at Sea Preparations for the Field Operation of the Ship The Survey Area Delineation of Area and Proposed Track The Actual Track Collection and Preparation of Samples Plankton Samples and Water Temperatures Continuous Monitoring of Water Methods of Analyses Gamma Ray Spectra Results and Conclusions Plankton and Water Temperatures Continuous Monitoring of Water Gamma Ray Spectra

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During the planning stage of were held by staff members of the Division of Biology and Medicine, Operation Redwing, discussions Atomic Energy Commission, and the Applied Fisheries Laboratory of the University of Washington on the probable need for biological surveys to define and evaluate the distribution of radioactive materials to be produced by the 1956

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The Division of Biology and Medtclne has assigned the Applied Fisheries Laboratory the following operations during and following the forthcoming test series: 1. Conduct two marine biological open sea surveys, beginning June 10 and September 1. mission of these two surveys Is to ascertain a the levels of introduced radioactivity resulting from the tests in the water, plankton, and fish, and (b) how far the activity extends westward in the North Equatorial current. lt has been recommended to the Task Force, that the ship should operate from the area of highest average fallout to the westward fringe of the detectable Introduced radloactlvlty In the water, and that you or Allyn Seymour-and the ship’s captain be briefed as to the location where fallout from each shot fell into the sea, prior to each survey.

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The ship assigned by the Task Force to the first of the two surveys was the USS WALTON (Destroyer Escort 361), a 306-foot vessel whose range and accommodations were considered adequate for oceanographical work In open waters. The WALTON arrived at used as a headquarters, most cooperative in the and shared with exchange of the HASL personnel who were use of equipment and Eniwetok on June was installed on and completed on 5, and shortly thereafter the survey equipment board. The survey was begun on Monday, June of the survey Is attributable to the support of the Division of Biology and Medicine, particularly Dr. W. R. Boss, and to the coordinated assistance given to the field team by the operational groups within Joint Task Force 7, particularly Task (M?oup7.3 (Navy). Members of the staff are especially grateful for the intelligent interest in the project demonstrated by Commander Arthur T. Emerson, Jr., captain of’ the WALTON, and for the very great understanding and assistance afforded by officers The probe for and constructed by tlon of Mr. Harris and members of the crew of the vessel. continuous water monitoring was developed the Instruments Branch of the Health and New York Operations Office, under the direcD. LeVine, Chief. The use at Eniwetok of a gamma ray spectrometer was made possible through the kindness of Mr. Robert Graveson, Chief Engineer of the Electronics Section, Instruments Branchy H,ASL,who also assisted and instructed members of the staff in its operation. The Eniwetok Marine Biological Laboratory of the Division of BioIogy and Medicine was

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one of two such AND OPERATIONS AT SEA results are reported herewith was up by the Division of Biology and Medicine for the purpose of collecting information on the levels and distribution of radioactivity introduced into the waters of the Eniwetok-Bikini area by the atomic testing program of 1956. A more extensive survey is scheduled for September 1956. As originally conceived, the survey was to be made “from the area of highest average fallout to the westward fringe of the detectable Introduced radi-oactivityin the water.” Final plans were made upon arrival in the field when a review of information available on fallout patterns indicated the desirability of a survey pattern that would provide ample sampling of water and plankton in the areas Immediately about Enlwetok and Bikini as well as to the west of Eniwetok during the ten days granted for the survey. The cruise pattern thus projected, coordinated with Task Ch?oup7,3 and reported to the Division of Biology and Medicine, anticipated the coverage of fifty collecting stations on a grid extending from a line approximately 18o miles west of Eniwetok to a line 30 miles east of Bikini. The north and south somewhat modified during the course of the survey because of the testing program. The survey, however, actually covered fifty-three stations between Monday, June 11, and Thursday, June 21, on a track of 3,300 miles over 78,000 square miles of

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Preparations for the Field: Preliminary planning coordinated by the Division of Biology and Medicine and by Joint Task Force 7, specified that the survey vessel, the WALTQN (DE 361), should report to Eniwetok on or about June 5 and that she should be available for the cruise for approximately ten days after June 10. The WALTON reported on schedule at Eniwetok, and was joined immediately thereafter by members of the survey party, who began the supervision of the installation of survey equipSurvey Equipment: The equipment used in collecting plankton, sampllng water, and continuous monitoring of surface water, was installed on the afterdeck of the WALTON, approximately above the port screw. The counters, a recorder, and chemistry laboratory facilities were placed below decks in the after cifically, the ma~or Items of equipment were: 10 A continuous surface water monitoring probe with tank and water connections (Fig. 1), a unit designed and constructed by the HASL. 2. A power winch (Fig 2), feeding 3/16 inch steel cable over an A-frame and davit, for the use of plankton nets (Fig. 3) > and water sampling bottles (Fig. 4). 3. A steel platform (Fig. 4) extending two feet over the Port side of the ship to provide space for work with nets and f water sampling bottles. 4. A temporary chemistry laboratory set up on sheet ply-

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wood work tables fastened to existing bunk frames and supplied by electrical connections with 11OAC outlets (Fig. 5). 59 Two nuclear radiation detection instruments mounted on a temporary bench built into the wardrobe space of the after 6, A bathythermograph which was a part of the equipment of the ship. Operation of the Ship: The projected cruise pattern presented to the commander of the WALTON unu~ual navigational and operational problems, and the mechanics of the sampling at the various stations required close cooperation between personnel of the ship and of the survey team. It was calculated that to cover the fifty proposed stations in ten days, with a stop of’approximately 30 minutes at each station, and with a pause for refueling at the midpoint, the ship would have to maintain a speed of advance of fifteen lmots. As the operational procedure was worked out the ship steamed between stations at 18 knots, reduced the speed to 15 lmots at survey time (ST) minus twenty-five minutes, and further reduced the speed to 10 knots for a bathythermograph drop at ST minus 10 minute3.* At ST the ship slowed to 5 hots and altered course to put wind 30 to 90 degrees on the port bow, the drop side, because the plankton net had the effect of a sea anchor. When the ship was steadied, the port screw was stopped and the starboard engine was slowed to rpm for approximately 4 knots, or to a

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Speed that would maintain the plantion net towline at an angle of 45° with the surface of the water. For the subsequent drop of the water sampling bottles the starboard engine maintained rpm for speed of about 1 knot. After each drop the ship built Up slowly to the 18-knot cruising speed to avoid unnecessarily great variations in boiler brickwork temperatures. The WALTON reported to Enlwetok for refueling on Saturday, June 16, when approximately half of the survey had been accomplished. With additioml fuel aboard, the cruise was resumed the same day. THE SURVN AREA Dellheation of Area and Proposed Track: The area to be included in the survey and the projected track of the ship were a meeting on June 9 in the offices of Captain USN, representative of the commander of Task Group 7.3. Those present at the meeting Included Captain Munson; Commander N. Purley, naval liaison officer, CTU 7.1; Commander Arthur T. Emerson, Jr., captain of the WALTON; Mr. Merril Eisenbud Determinations of area and track were made after consideration of the elements of the problem, such as fallout patterns and estimated drifts of radioactive materials, and with lmowledge of such operational factors as the overall time limit on the survey, the speed of the ship, and the need of the ship for

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additional fuel at some point during the 3,000-mile cruise. The proposed track finally was laid out on a providing distances of 45 miles betw=nstations. running northeast and southwest, although calling runs between stations than on north-south or east-west tracks, were used (a) to give continuous water monitoring readings that were only 32 miles apart, and (b) to put the operations at sea on headings that would The Actual hack: the return to Eniwetok minimize the ship’s roll. From the point of the initial drop to for fuel on June 16, the WALTON followed rather closely the track that had been laid out in advance. During the second half of the crulae, however, It was necessary to modify the track to avoid possible contamination of the ship by tests scheduled in the area and to provide, in the vicinity of Bikini, a more complete coverage of the area contaminated by the drift of radioactive materials. The track actually accomplished by the WALTON is shown in Figure 8. COLLECTION AND PREPARATIQt?OF SAMPLES ments of the activity and fish samples and continuous rneasurein the surface water were taken. Plankton Samples and Water Temperatures: Plankton samples were obtained by twenty-minute oblique tows from about 200 meters of depth using a l-meter Michael Sars type net of No. 6 mesh (Fig. 3). No. 6 mesh is equivalent to seventy-four meshes per inch with apertures of 0.24 mm. This mesh retains some microplankton as well as larger forms. Organisms longer than

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Ing. The plankton from the samples before processthrough No. 1 Whatman paper and about two grams were transferred to a 1.5-inch stainless steel planchet, dried with an infrared lamp, and then counted aboard ship. The remainder of the plankton sample was preserved for future use. Amounts of plankton were determined volumetrically. A 50 ml portion of sea water and plankton was poured Into a Buch.nerfunnel with No. 1 Whatman filter paper. The amount of plankton remaining on the filter paper was determined by subtracting the amount of filtrate from the original amount of sea water and plankton (50 ml). After returning to Eniwetok Marine Biological Laboratory the shipboard estimates of the volumes of the plankton samples were revised. The corrected volumes were calculated by multiplying the dried sample weight of the individual samples by the ratio of the average estimated volume to the average dry weight. Finally, volumes in ml were converted directly to wet weights in grams. Bathythermograph casts were made by the ship’s crew at each station during the cruise for the purpose of defining temperature change with depth. Water Samples: Samples were collected at the surface by bucket and at 25, 50, 75 and 100 meters by means of a Nansen water bottle (Fig. 4). The surface water samples were processed aboard ship and the other samples at the EMBL. One liter of surface water was passed through a Milllpore filter using Millipore AA paper. The filter paper was saved and counted. From the filtrate two 100 ml samples were processed

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for counting and a To each of the 100 500 ml sample saved for possible future use. ate was added. The precipitate was collected on 1$-inch Milllpore HA paper in a Mlllipore filter and counted. By this method 40naturally occurring K , normally present In sea water to the extent of about 600 d/m, Is eliminated from the portion which is counted. Radiocesium is also lost In the filtrate but accounts for less than one per cent of the total activity at the time of collection. The water samples processed at EMEL were treated in a similar manner except that a 500 ml sample was filtered and only one 100 ml sample was prepared for counting. Fish Samples: Time and facilities were not available to collect fish in numbers. However, three flying fish were found on deck and taken as samples. Larval forms and small fish were captured in the plankton nets but were not processed separately. In an attempt to increase the take of flying fish a section of white canvas was stretched on the starboard side near the after gun mount. A light was kept burning at night The three flying fl.shwere frozen aboard and muscle were processed at the E14BL. These for 12 hours at about 100°C on 1~-inch plates, to illumlmte the ship. The liver tissues were dried (3 hours), slurrled with alcohol and fixed to the plate …