OPERATION CROSSROADS, RADIOLOGICAL DECONTAMINATION OF TARGET AND NON- TARGET VESSELS Part I

Navy Reports that document the dumping of nuclear waste directly into San Francisco Bay as well as other Navy Bases, the orders, correspondence, etc.

Introductory statements to the Report

OPERATION CROSSROADS, RADIOLOGICAL DECONTAMINATION OF TARGET AND NON- TARGET VESSELS Part I pp 3-17
https://archive.org/download/DTIC_AD0473906/DTIC_AD0473906.pdf

[Note all page numbers and notes will be enclosed in these brackets]

[It is important to note that the safe radiation levels at the time did not put into consideration the cancer hazard and all they were concerned about is preventing radiation sickness. All of the sailors involved in this operation were later compensated with a settlement from the United States after Congressional Hearings in the Clinton Administration, the ones still alive of course.]

PART I

DECONTAMINATION OF TARGET VESSELS

1. As a result of Test Able on 1 July, no extensive deposit of long life radioactive fission products or alpha emitters was found on the target vessels. Radioactivity existing was induced type and was of very short half-life. Within a period of twenty four hours after fission of the bomb the level of radioactivity permitted reoccupation of surviving targets, with the exception of concrete barge YO-160, without radiological hazard. Consequently no decontamination of target vessels was required.

2. Consideration of radiological conditions which might be expected subsequent to Test Baker led to the conclusion that the most important effect from a radiological standpoint probably would be contamination of the lagoon waters. The conditions experienced in Test Able and had a close parallel in the previous three fissions, but the underwater burst was an entirely new phenomenon without precedent. A complete organization of personnel and instruments was set up to study and record the radiological conditions produced in the lagoon as a result of both Able and Baker fissions. This organization initially did not include, however, the gathering of complete scientific data concerning radioactivity on the target vessels.

3. It was recognized prior to Test Baker that (a) there was a possibility of considerable fall-out of radioactive matter from the cloud of water vapor which would be generated by the burst; (b) a wave approaching one hundred feet in height at the center of the array would dash large amounts of water against the target vessels. As a result of these two effects it was concluded that radioactive matter would be retained in undrained pockets about the weather decks of the target ships and that some would enter the interiors of the ships through vent ducts, stacks and other openings. In order to minimize this effect, all target vessels were secured as for heavy weather and temporary closures provided as practicable for openings caused by Test Able damage. Also, canvas covers were provided for stack openings, vent terminals and other openings not equipped with adequate closures. As a matter of safety and information, initial bearding teams also were instructed to note particularly the radiation conditions existing in pockets where contaminated water might collect. It is of interest to

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note at this point that the initial boarding teams were constituted primarily as a safety organization, with immediate damage and technical observation as a secondary function. Radiological conditions prevailing on the target ships were, at that time, of immediate interest to the Director of Ship Material only insofar as they related to safety of personnel reboarding the ship and in what respects they might impede reboarding, Instrument recovery, rehabilitation and complete damage inspection of the targets.

4. The lagoon was reentered by the Director of Ship Material (in RECLAIMER) with vessels of the Salvage Unit (TU 1.2.7) in which boarding teams were embarked. It was found, as expected, that the lagoon waters were much more highly radioactive than after Test Able. Four vessels (APA’s) in the southern string and one vessel in the southwest string could he approached and reboarded, as the water in their vicinity and the ships themselves were clear of radioactivity. Access to the remainder of the target array, however, was denied because of the high levels of radioactivity in the water. Some of the outer vessels were approached for short periods. It was found that every vessel approached showed from a distance, levels of radioactivity which would permit boarding for only short periods – generally less than an hour. On Baker plus one and Baker plus two it was possible to approach Hughes and Fallon, but both vessels were radioactive to the extent that taking them in tow for beaching required fast work. The forecastle of HUGHES, for instance, had a tolerance time of about eight minutes. As the radioactivity in the lagoon decreased, it was possible, on Baker plus two and three, for the Director of Ship Material in RECLAIMER to survey quickly all target vessels from about 50 to 100 feet distant. Every ship, except those noted previously, had high radioactivity levels with the exception of CONYNGHAM and CARTERET at the end of the west and southwest strings, both of which had low levels.

5. Since the nature and extent of contamination of the targets was completely unexpected, no plans had been prepared for organized decontamination measures. It was immediately recognized that the functions of the Technical Director and the Director of Ship Material in the Crossroads Tests could not be completed without inordinate delay unless a means of decontaminating the ships expeditiously could be devised. The Director of Ship Material assumed the Initiative in con-

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ducting preliminary tests, after conferences with the Radiological Safety Section, to determine whether the contaminating material was subject to removal by any simple and rapid means utilizing material and equipment readily available.

6. Observations subsequent to Test Able had revealed that pools of water found on target ships were somewhat more radioactive than surrounding deck areas. It was therefore concluded that water might take up some of the radioactive materials in solution. Consequently, on 27 July some of the fire fighting vessels of the Salvage Unit (TU 1. 2.7) were employed to wash down with salt water HUGHES, which had been beached in radiologically clear water. After a wash down of about two hours’ duration, radiation readings taken revealed that the intensity had been reduced about fifty percent. A second washing under similar conditions produced no further substantial reduction. Since the radiation readies now were 9.6 R/day on the forecastle and 36.0 R/day on the stern, it was obvious that some supplementary general contamination removal was required even to permit reboarding for limited periods.

7. The next step in the experimental removal of radioactivity was to try application of Foamite to the surfaces since abundant supplies were available in the area. Foamite has a soapy appearance and consistency, and it was hoped that it might have a detergent action with respect to removal of radioactive materials. Foamite was applied by Salvage Unit Vessels to HUGHES on 27 July and incompletely washed off with plain salt water. In areas where washing had been thorough, a resurvey indicated that the radiation intensity had again been reduced by fifty percent. Another application of Foamite was then made to HUGHES and allowed to remain overnight. The following day (28 July), a thorough wash down with salt water, again using the Salvage Unit Vessels’ firefighting facilities, once more reduced the level of activity by fifty percent. The maximum readings at this time were 3.O R/day port, and 8.5 R/day starboard, with an average of about 2.0 R/day on the main and forecastle deck levels. The high reading on the starboard side was considered attributable to the fact that the beached location of the ship allowed use of monitor nozzles only on the port side in washing, whereas portable pumps in an LCM were used for the starboard side wash. The reduction in readings obtained was

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most encouraging and, although much of it was due to natural decay, there was no doubt that considerable acceleration had been produced by the processes being used. This fact was further borne out by the differences between the radiation intensities on the port and starboard sides as mentioned. As a result of these experiments, it was felt that, pending development of better methods, washing and Foamite applications should be made in accordance with a prepared schedule as soon as practicable and as consistent with considerations of salvage operations, recovery of instruments and the value of target vessels as technical specimens. It had been found from experience in the period since Test Baker that water slightly contaminated tended to deposit its contained radioactive materials on surfaces of systems and equipment exposed to sea water and in marine growths on underwater bodies of operating vessels. It was therefore necessary to wait until the salt water surrounding the target vessels was radlologlcally clear before proceeding with the washing. It was also obvious that the washing methods developed were not by any means a complete nor a wholly satisfactory solution to the problem and that further study was imperative.

8. On 27 July a conference was held with the Radiological Safety Section in which the need for developing a satisfactory method of rapid removal of radioactive materials from the targets was emphasized. It was requested that a detailed study be undertaken immediately to evolve a suitable method. In response to this request various samples of contaminated equipment were selected for conduct of special tests by the Radiological Safety Group. The objects were blasted with soft grits such as ground corn cobs, cocoanut shells, rice, barley, ground coffee, rice hulls and sand using a diesel driven air compressor rated at 315 cu. ft. per minute at 90 psi., and introducing the material through a simple eductor arrangement. The specimens treated included electric lanterns, copper pipe, a plastic coffee maker, angle irons, aluminum angles and sheets, a brass boat hook, Junction boxes of brass and bakelite, a brass shower drain screen and galvanized steel plate. The following were the findings of the tests:

(a) Painting over the surface produced no reduction in activity since the radiation was primarily gamma.

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(b) Blasting copper pipe with grain rice reduced activity to one-half, but complete removal could be achieved only with sand.

(c) Painted objects could be partially decontaminated by blasting with coffee without injury to the surface, but complete decontamination required removal of all paint.

(d). Radiation intensity from a brass casting which was porous from dezincification was reduced from 4.5/R to 2.0 R/24 hr. by blasting with rice, but further treatment with rice or sand failed to yield additional results.

(e) Brass surfaces could be decontaminated with nitric acid. There findings showed that radioactive material could be removed from surfaces by wet sandblasting, or partially by blasting with various soft grits. However, these measures are not suitable for general decontamination of a target ship in the field and their usefulness was restricted primarily to clearing local areas.

9. The Director of Ship Material made a small scale laboratory study on 28 and 29 July to investigate the possibility of decontaminating by use of various materials available locally or readily obtainable from Pearl Harbor. The possible methods of removal of radioactive materials investigated were (a) detergent action by soap powders, lye and volatile naphtha; (b) dissolving action by acetic, hydrochloric and sulphuric acids; (c) absorption by flour, cornstarch, activated charcoal and sandblasting. The first results of the investigation revealed that the source of the radioactivity lay in the collection of radioactive materials on or in wood, paint coverings on metal, and on rough and rusted metal surfaces. It also was noted that radioactive materials were retained to a remarkable degree by all exposed organic materials such as canvas, life rafts, manila line, swabs, brooms, wood decks and the like, and all exposed items of these materials observed were very heavily contaminated. All of the reagents listed above were tried on painted wood, steel and canvas surfaces. None was successful in the removal of the radioactive materials with the exception of a prolonged washing in a five percent solution of acetic acid solution. This process was not suitable for expeditious mass application to the target ships by methods known at the time. The other reagents accomplished reduction of radioactivity only to the extent that they actually removed the paint or surface corrosion.

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10. On 28 – 30 July a series of experiments on a larger scale was conducted supplementing the laboratory studies. A vessel of the Salvage Unit sprayed exposed surfaces of TUNA first with diesel oil and later with a solution of lye and boiler compound. Each application was followed by a thorough washing with plain salt water. The diesel oil produced negligible results, but the lye and boiler compound solution reduced the average readings immediately by about sixty-six percent. The same solution on SKATE produced very poor results, but a large portion of the superstructure of this ship was missing as a result of Test Able and most of the remaining surfaces were painted with black plastic or bituminous enamels which were not affected by the lye solution. The application of lye and boiler compound on TUNA had removed a considerable proportion of the paint from exposed surfaces. Both the laboratory and large scale experiments of 28 – 30 July thus clearly indicated that the most practicable means of early decontamination of the target vessels lay in the use of a mixture having detergent qualities strong enough to remove outer layers of paint. The problem remaining was to develop techniques and procure the necessary materials and equipment to accomplish this end.

11. The method selected for the actual removal of contaminated materials was based on the reduction of radiation intensities by use of wholesale washing processes until levels were reached at which inspection and instrumentation personnel and small groups of ship’s form could remain aboard safely for periods of at least two hours. Ship’s personnel In relays would then apply detailed scrubbing, abrasive and paint removal action as necessary to reduce the radioactivity sufficiently to permit continuous habitation of the ships. It was also an urgent necessity to remove animals to obtain instrumentation records and to proceed with post-technical inspections. Some vessels required reboarding for pumping out flooded spaces. Appropriate instructions as to procedures to be followed, clothing to be worn and detailed safety precautions were promulgated to all target ships. In addition, necessary personnel were informed as to the methods to be used and the hazards involved, by conducted demonstrations to school ships’ crews in the operations to be followed. Detailed instructions issued by the Director of Ship Material are included with Appendix IV.

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12. Briefly, the program consisted of the following steps:

(a) Ship thoroughly washed down with plain salt water.

(b) Radiological monitor, DSM representative and ship’s force representative board ship, make quick preliminary survey of radiological conditions and note particularly hazardous areas. Boarding party together with Commanding Officer of salvage vessel formulate plan of action to proceed with decontamination.

(c) If conditions permit, ship’s force working party boards vessel, removes all exposed organic materials, working in relays as necessary to avoid overexposure. If radiation intensities still prohibit this action, paint removal mixture must first be applied as below.

(d) Prepare paint removal mixture of 450 lbs. lye, 600 lbs. boiler compound and 75 lbs. of cornstarch with sufficient water to produce 1000 gallons of mixture. Lye and boiler compound are added gradually to 500 gallons of water, mixed and dissolved. Cornstarch is mixed separately in a thin suspension and added gradually to produce smooth suspension. Fresh water is added to produce 1000 gallons. Batch is heated by steam hose until starch swells and boiler compound dissolves completely. The mixture is applied by Chrysler salvage pump taking suction on tank and discharging through 1 1/2″ fire hose with all-purpose nozzle or fog nozzle with applicator. All painted surfaces of the target vessel are thoroughly coated with the mixture. After an interval of about two hours ship is again hosed down vigorously using monitor nozzles with maximum force available to remove all possible paint. Care is exercised to leave no gaps and to sweep all paint chips clear frequently by use of the hose in order to minimize transfer of contamination to other surfaces.

(e) Following this process, target vessels are again reboarded by the DSM representative with a monitor, Radsafe representative and a responsible officer from the target vessel. The general radiation level is checked at this boarding to ascertain whether the vessel is not safe for small working parties is relays to apply detailed decontamination measures. All spots remaining highly

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radioactive are noted and the source of the excessive radiation determined if practicable. If the spots are too extensive and apparently the result of gaps in the paint removal process, it may be necessary to repeat the applicable steps in the paint removal procedure to reduce the activity of the recalcitrant areas. If, on the other hand the vessel is determined to be safe for working periods of four or more hours, detailed decontamination measures by the ship’s force can proceed.

(f) For prosecution of detailed decontamination procedures, all radiological dangers when found are marked clearly and if necessary roped off to keep personnel at a safe distance. Monitors are present at all times to insure that personnel do not remain on the ship beyond tolerance hours set. Detergent mixtures similar to those used for the gross decontamination are applied to painted surfaces remaining above tolerance for continuous habitation. Long handled scrubbers, holystones, and other similar devices are used to scrub the surfaces, and any available means of aiding the mixture in the removal of paint, rust, scale and the like are resorted to. Each operation is followed by a vigorous, plain salt water hosing to wash all removed contaminated material from the ship. The process is repeated several times in affected areas until tolerance limits for continuous operation are attained.

13. General washing with salt water and application of this formula carried out during the period of the above investigations in accordance with a priority list as soon as the water around each of the involved vessels became clear; the use of Foamite was abandoned as being less effective. Detailed decontamination by ship’s force in accordance with the instructions promulgated by the Director of Ship Material was commenced at once on the lightly contaminated vessels such as CONYNGHAM, WAINWRIGHT, CARTERET and SALT LAKE CITY. Meanwhile ten vessels of the Salvage Unit (TU 1.2.7) were outfitted to carry out the gross decontamination of other more heavily contaminated targets by applying the detergent mixture. This outfitting was completed on 5 August. Five APA’s, BLADEN, CORTLAND, FILLMORE, GENEVA and NIAGARA, not exposed to the radioactive fall-out, had been cleared on Baker Day. These vessels were reboarded immediately and accomplished local decontamination by scrubbing with soap and water and washing down sufficiently to obtain radiological clearance for complete rehabilitation.

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14. The application of the new gross decontamination measures progressed very satisfactorily in spite of many handicaps. Decontamination by ship’s force was begun on the following target vessels in addition to the five APA’s which had already been cleared as stated above:

SALT LAKE CITY (CA 25)

NEW YORK (BE 34)

NEVADA (BB 36)

PENNSYLVANIA (BB 38)

PRINZ EUGEN (IX 300)

CARTERET (APA 70)

WAINWRIGHT (DD 419§)

CONYNGHAM (DD 371)

MUW ORD (DD 389)

WILSON (DD 408)

PARCHE (SS 384)

DENTUDA (SS 335)

TUNA (SS 203)

SKATE (SS 305)

SEARAVEN (SS 196)        

Appendix I contains detailed reports of procedures followed on several representative ships.

15. The accomplishment of the gross decontamination measures involved many practical difficulties and many hazards. Great care was necessary to insure that the length of time during which the salvage vessel might be alongside the target without dangerous exposure was not exceeded. It was, of course, highly desirable for the salvage vessel actually to put a line over to the target vessel to insure an effective treatment of the target, but some targets were radioactive to a degree which prohibited closing to less than fifty feet except for very limited periods. Great care was necessary also to avoid washing contaminated materials into the target vessels. In addition it was necessary to skip entirely certain areas around open hatches, large air intakes and other openings to prevent introduction of large volumes of water and paint removal mixture Into the ship’ interiors. Aside from all this, the paint removal material itself, containing large quantities of lye, was

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hazardous to handle. Protection of personnel against both chemical and radioactive hazards was of paramount importance during these operations.

16. The work required by ship’s force decontamination was laborious and largely manual; it required considerable time and hazards were involved from the standpoint of both radiological considerations and danger of injury in handling paint removal mixtures prescribed. In the course of the work, decontamination of specified areas of steel decks was attempted by use of scrubbers with strong solutions of first acetic, then hydrochloric acids following each scrubbing with a thorough wash with salt water. The superiority of this process over scrubbing with plain salt water was not sufficiently marked to justify adoption. In view of later information and experience, however, it is considered that because the areas so treated were small and surrounded by large masses of radioactive material, the readings obtained were indicative of the general radiation level or “background” of the vicinity rather than the condition of the treated surface. However, general acid application was not developed into a practical method. Attempts were made to reduce the activity of wood decks by holystoning with sand, lye and boiler compound on SALT LAKE CITY and NEW YORK. NEW YORK’s decks showed considerable acceleration over natural decay rates, but SALT LAKE CITY’s indicated no improvement. The lack of success in the latter case is considered at least partially attributable to the fact that adjacent painted steel surfaces were being decontaminated simultaneously and, as a result, contaminated water was being washed over the wood decks almost constantly. Also the ship’s general radiation level undoubtedly, obscured the actual results.

17. During the course of decontamination by ship’s force, elaborate measures were required to protect personnel against radiological hazards. In addition to providing monitors on all ships at all times that personnel were aboard, rubber boots and rubber gloves were necessary since shoes and cloth or leather gloves are quickly contaminated, and the fission products attaching themselves are most difficult to remove even by laundering. All personnel were required to be fully clothed at all times and to take showers and change clothes after each operation. All clothing worn was required to be laundered after

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each day’s work. Special change facilities and showers were set aside for this purpose on the target APA’s which had been cleared. Special laundry facilities were also designated for washing the contaminated clothing in order to avoid contaminating general laundries. Even with the most elaborate precautions it was necessary to exercise constant vigilance to insure that all personnel were safeguarded adequately. In spite of all handicaps, however, the work proceeded very satisfactorily.

18. On 9 August, the Director of Ship Material requested the Radiological Safety Officer and the Commander Target Group to visit ships on which ship’s force were employing the detailed decontamination procedures. During that inspection, samples of materials were obtained from areas of the wardroom of PRINZ EUGEN for which Geiger counter readings showed radiation Intensities sufficiently low to permit extended personnel exposure without danger of injury. An analysis of the samples revealed the presence of alpha emitters which were not detectable with the monitoring Instruments in use at Bikini. Further investigation showed probable widespread presence of the alpha emitter in the target area even in spaces not obviously contaminated. Once no alpha detectors for general field use were available and the alpha emitters are one of the most poisonous chemicals known, their presence was considered a serious and indeterminate menace to personnel exposed for indefinite periods of time on contaminated target vessels without special complex protective equipment and trained personnel to detect the alpha emitters. A conference was called by the Task Force Commander on 10 August to discuss the matter. As a result of this conference, continuation of detailed decontamination was considered unsafe under the existing conditions, and all further decontamination work on the targets by ship’s force was ordered discontinued. Subsequently, all further work on these vessels by Task Force Personnel was limited to recovery of instruments, limited surveys, salvage work, and preparations for towing from the area.

19. It was unfortunate in many respects that the decontamination procedures instituted had to be discontinued as a result of the investigation requested by the Director of Ship Material on 9 August. It is fortunate, of course, that the analysis of remaining products was made since the facts revealed thereby precluded the possibility of exposing large numbers of personnel to a hazard not detectable by instruments at hand. However, the planned procedures of pre-

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liminary decontamination by spraying and washing from salvage vessels close aboard, followed by short clean-up and monitoring of upper decks, with thorough spraying and washing from alongside as necessary, and finally, detailed decontamination by the ship’s crew were not carried out for a sufficient period to permit proper evaluation or determination of ability to reduce levels of radioactivity to acceptable tolerances by these methods. Even if this had been possible, the removal of alpha emitters would still have been a problem not susceptible to field solution.

20.  In order to appraise the value and effectiveness of the decontamination procedures that were used on the surfaces of the target vessels, It is necessary to examine briefly the nature of the contamination existing. Post-Baker investigation revealed that about fifty percent of the total radioactive material produced by the explosion remained in the waters of the lagoon. Readings taken at very early stages showed that invariably the largest part of this material was deposited on the surface of the water and very little, if any, was present near the bottom. This means that most of the contamination resulted from the bars surge, the following wave and then the rain and spray fall out which covered the bulk of the target area for a considerable time after detonation. In the cloud resulting from the explosion there were in addition to the fission products, undoubtedly elements from the sea water which had Induced radioactivity, the most important being sodium. The materials were rained down on the ships over a wide area and upon evaporation of the water were deposited on the surfaces where they fell. Large quantities of highly radioactive coral and sand also were deposited on the ships. The area affected extended from about 1800 yards upwind to more than 4000 yards downwind and about 3000 yards crosswind. All but nine of the target vessels in the array *ere heavily contaminated by the rain and spray. Most of the water deposited ran off the ships and such variations as existed In degree of contamination-were probably due to the characteristics of the design of the ship, its age and the condition of the exposed surfaces rather than its distance from the center of fission. It is also possible that the rain was at an elevated temperature and tended to penetrate and soften the paint as well as deposit itself on the surface. The concept of contamination by the ” base surge”, or wave of vapor emanating from the center of fission, is as yet imperfectly understood. More study of this phenomenon may modify considerably some of the above assumptions. The retention on the surfaces also was aided by ion-ex-

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change since the long lived fission products deposited in seawater are known to be largely polyvalent cations which would displace easily the monovalent sodium and potassium cations which would normally be present on paint, rust, scale, algae and similar surfaces exposed constantly to sea water and known to have a high Ion-exchange capacity. Further, the fact that fission products were present in low concentration and-submicroscopic form, even though the solutions were highly radioactive, aided the exchange absorption of the products radioactive, aided the exchange absorption of the products.

21. Accurate evaluation of the decontamination measures instituted Is very difficult to make because of unreliability of Instrument, the Irregular variation of readings and the lack of uniformity in methods of reporting radioactivity. Also, data are incomplete since many of the ships were too highly radioactive to board prior to first gross decontamination. Probably as a result of Ion-exchange as discussed above, all rust, dirt, loose paint and organic materials tended to hold the contamination and became much more highly radioactive than clean, well-drained surfaces. The initial washing process removed much of the material of this type, but probably did very little, if anything, toward removing Imbedded or attached ionized radioactive materials from surfaces remaining. The lye-boiler compound r starch mixture developed for the purpose was designed to have a detergent action and to remove the outer paint layer and the attached or imbedded radioactive materials with it. It is significant to note that the processes used were effective only insofar as they accomplished this function. It was found in the short experience gained that difficulties of application on the large scale required also prevented better results. Furthermore, there was the necessity for haste in order to complete the Director of Ship Material and Technical Director missions, and to avoid retaining any of the Task Force in the lagoon under undetermined conditions of exposure more than a minimum of time. Some of the contamination was transferred to under surfaces, corners, scuppers and drains and resists removal by the methods in use. The procedures adopted did not have a pronounced effect on wood decks, canvas or unpainted surfaces. The abrasive scrubbing with sand and holystones was successful to some degree on wood and bare surfaces Insofar as it removed the outer and more heavily contaminated surfaces. There is some doubt as to the efficacy of the holystoning on the decks, however, as it appears that some of the activity re-

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moved was re-transferred to the cleaned surfaces in the associated washing and that one effect may have been to drive the radioactive material in deeper.

22. The gross decontamination by Salvage Unit vessels from along-side was fairly successful in cleaning the ship as a whole and also in concentrating on limited areas. The higher structures of the targets were difficult to reach to apply the paint a removal mixture. Further, this mixture did not loosen the paint to a sufficient degree to permit removal by ordinary washing but required the full force of a stream from a monitor fire-fighting nozzle to realize good results. Because of this fact, removal of paint from most of the upper decks of target vessels was incomplete since the monitor nozzles could not be brought to bear forcibly by reason of height and screening of the areas by splinter and weather shields. That the work was generally effective, however, can be illustrated by a specific case such as the BRACKEN. This vessel received a complete gross decontamination, but no ship’s force work was accomplished. On boarding to remove animals on 27 and 28 July, the average Geiger counter reading on the exposed main and superstructure decks was 11.0 R/29 hours. The ship was given a coat of Foamite on 31 July and washed the following day. The ship was again washed down on 3 August and on completion of this treatment showed an average topside reading of 1.7 R. On 6 and 7 August the ship was sprayed with paint removal mixture end after washing down showed an average reading of 0.3 R/24 hours, and an elapse of two more weeks would have been required for the average intensity of radiation to have reached 0.3 R/24 hours by natural decay.

23. It is regrettable that necessary procedures were not established for obtaining more accurate and detailed information as to conditions of radioactivity existing on target vessels both before and after decontamination. Pressure of time and limitations of facilities, instruments and personnel available, however, precluded the achievement of this goal. Much also can be ascribed naturally to the lack of Information and realization of the conditions to be expected. Consequently, it was impossible to plan for them, which is to be expected in the first experience with a phenomenon of this magnitude and scope. The decontamination measures adopted as an ex-

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pedient after Test Baker, although successful to a certain extent in the limited application they received, revealed conclusively that removal of radioactive contamination of the type encountered in the target vessels in Test Baker cannot be accomplished satisfactorily for wartime application from the standpoint of time and effort with standard equipment now readily available. The measures employed, however, were effective enough to permit removal of instruments and instrumentation records, technical inspection of the vessels, removal of animals and salvage operations. Otherwise portions of the Task Force would have been delayed in the lagoon for one to two months.

24. The following program of further action in radiological decontamination investigation and development was clearly indicated as a result of the early experience with Crossroads targets:

(a) Extensive study and analysis to determine the exact nature of the contamination resulting from Test Baker.

(b) Broad research to develop satisfactory methods of large scale decontamination of ships.

(c) Careful study of surface characteristics with respect to radioactive contamination and research to develop suitable surfaces to minimize contamination.

(d) Appropriate education of naval personnel in matters of radiological hazard and instruction in methods of decontamination when developed satisfactorily.

(e) Necessary design changes in ships to reduce contamination and its effects and to facilitate removal of such contamination as cannot be avoided.

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