Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 80
6 Uncertainty Analysis by Individual Test Series The United States conducted 19 atmospheric nuclear weapons test operations spanning the period from July 1945 to November 1962 (Table 6-1~. Each test operation was different in some aspect of personnel film badge dosimetry. The type and number of nuclear test detonations varied, environmental conditions were not the same in the Pacific as at Nevada Test' Site, type of film badge used changed, dosimeter film components used also changed, and film calibration and processing procedures differed for some operations. To assure that all these different factors affecting film dosimetry programs were considered, the film dosimetry bias and uncertainty for each test operation were analyzed separately. A full analytical discussion for each test operation follows in this chapter. Each of the individual discussions include consideration of personnel exposed; technical factors such as type of film badge, issue, processing and calibration procedures; availability of records; tabulation of bias and uncertainty values established; and tables showing deep-dose equivalent and 95% confidence limits of these values as functions of exposure. For some test operations, significant differences were found in uncertainties associated with results from badges worn by flight personnel, i.e., those who flew cloud sampling or similar missions in aircraft, and those worn by ground person- nel, including those aboard ships. In these cases, separate tabulations are pro- vided for flight and ground personnel. Relatively large radiological-spectrum bias and uncertainty values resulted when film badges used during some test operations were analyzed. These badges generally had an insufficient thickness of filter material and were used during the earlier operations. Another factor affecting dosimetry in early test operations was inadequate exposure-range cover 80

OCR for page 80
81 A) A, it .§ a. o of 3 c) e o d cat Ha. - 1 - D Cal .' - - a' a It u U. C ~ ~ ~ 9 9-, ~ ~ Y 9 _ Y Y . Y ' 7 E 9 s I y c ~ ~ ~ | ~ ~ 9 ~ · ~ ~ ~ g t ~ L 9 8 8 ,, g ~ ~ ~ ~ 8 ~ ~ _ ~ ~ c" s ~ ~ ~ - ~ c~ w) ~ ~ Go t~ _ so ~ _ t~ ~ ~ t#~ t~ ~ _ - _ ~_ o E E E E g Z Y Y Y e 3~ E = ~g s 5 y 9 0 -c ~82~ ~ t~ \0 ~ ~ ~ - ~ ~ ~ ~ ~ ~ ~ - $ ~ - ' ~ ~ ~ ~ _ ~ _ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0\ ~ ~ E Z 9 9 o o y u E 3 E 9 9 o 9 0 = j ~3 U! ~o °° C~ . C,,

OCR for page 80
82 FILM BADGE DOSIMETRY llV ATMOSPHERIC NUCLEAR TESTS age of the dosimeter film or films used. Uncertainties in this regard are not listed in particular test operation bias and uncertainty tables, but are presented, where appropriate, in narrative form after tables which convert from film badge exposure to deep-dose equivalent. Bias and uncertainty tables conclude with overall values for converting film badge exposures of 0.2 R or more to deep-dose equivalents. PROJECT TRINITY Background Project STY was the first test of a nuclear explosive device. The detona- tion occurred atop a tower at the Alamogordo Bombing Range in New Mexico on July 16, 1945. The device was identical to the one in the weapon dropped on Nagasaki, Japan, a few weeks later. The yield (tons of 'iNT explosive that would release an equivalent energy) of both detonations was 21 kilotons (kt). The test was the culmination of the "Manhattan Project", the code name given to the atomic bomb development program directed by the Manhattan Engineer District of the Army Corps of Engineers. Scientists from the Los Alamos Scientific Laboratory (LASL), part of the Manhattan Engineer District, devel- oped, constructed, and detonated the device. LASL personnel also provided radiation protection and film badge monitoring. Personnel Exposed Only a few hundred people observed the detonation near the test location (Maag and Rohrer 1982~, but the total number of observers, experimenters, and workers who had visited the site by the end of 1946 was about 1000. The highest recorded cumulative exposure was 15 R and was received by an individual who made several entries to "Ground Zero" shortly after the detona- tion. Most exposures occurred at or near "Ground Zero" but several people were exposed off-site while tracking the fallout cloud. Type of Film Badge A special film badge was used at Project TRINITY and was not used in any subsequent operations. The badge contained two film packets that were placed side by side in a brass holder. The brass was 0.020 inches (0.508 millimeters) thick and acted as a filter which reduced the characteristic over-response of film to low-energy photons. One film packet was manufactured by the Eastman Kodak Company and

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES - TRINITY 83 contained a single Type K film. The other packet was manufactured by Du Pont and was a special Type 552 packet. It-contained three films; a Type D-1 and two Type D-2 films (Reinert 1946; Littlejohn 1946; LASL 1945~. The Type D-1 and D-2 fUms are believed to correspond with Du Pont Type 502 and 510 films, respectively, manufactured later. The measurement range of the Type K film was generally considered to be 0.05 R to 5 R (Buckland 1945; Dessauer 1947~. Exposures as low as 0.0L R were reported for people who visited the site many months after the test (Reinert 1946~. The Type D-1 film had a range from 0.1 R to 10 R (Storm 1951; Ehrlich and Fitch 1951~. The Type D-2 film was less sensitive and measured exposures between 5 R and 40 R (Storm 1951; Ehrlich and Fitch 1951~. Conceptually, no problems should have been caused by overlap of the meas- urement ranges of the films. For unknown reasons, data for each of the films were not always recorded nor used in exposure evaluation. Some exposures were assessed using the Type K and the two D-2 films, some with the Type K and the D-1 films, and some with Type K alone. The first case produced overlap problems. The poor agreement that often occurred between the two D-2 films aggravated the problem. Badge Issue and Exchange Badges were generally issued at the test site. For the first few days after the detonation, entries were controlled by a "Going-In Board." This procedure as- sured that all personnel entering radiation areas were properly badged. The primary source of information concerning badge issuance is that presented in a report on safety and monitoring of personnel (Aebersold 1947~. There is no evidence that cohort badging was used (see Operation CROSSROADS). Calibrations, Processing, and Interpretation Calibrations were performed with a radium-beryllium source. The source activity was approximately 1000 millicuries (mCi) (LASL 19459. All films were exposed at a distance of 49.5 cm from the source with the time varied to achieve different levels of exposure. Seven exposure levels were used ranging from 0.19 R to 10.29 R (LASL 1945~. Calibrations were infrequent and the same character- istic curve was used for many developing batches. Developed films were evalu- ated with a Marshal densitometer (LASL 1945; Littlejohn 1946; Reinert 19461. An unexposed film was developed with each group of personnel film to account for base fog (LASL 1945). The exposure reported for individuals was obtained by averaging the exposure determined from the separate films. As indicated, the number of films used to calculate the exposure varied because some films were not always evaluated. Of

OCR for page 80
84 FILM BADGE DOSIMETRY IN ATMOSPHERIC NUCLEAR TESTS the 51 readings above 1 R. 19 were calculated from the K and both D-2 films. The rest used the K and D-1 films or the K by itself (Buckland 1945~. Current Availability of Records No personnel dosimeter films are available for review from the TRINITY event Density and exposure data for personnel films and films sent to various post offices in New Mexico are listed in LA Notebook 1144 (LASL 1945~. Data for two calibrations are available also. A summary of personnel exposures was reported by Buckland (1945) for those people exposed during the first few days after the detonation. Exposures occurring later were reported in Los Alamos Scientific Laboratory memoranda (Littlejohn 1946; R,einert 1946~. Estimated Bias and Uncertainty The following table presents bias and uncertainties that result from different influences on film badge performance. These values are appropriate for exposures ranging from approximately 0.2 R to 3 R. The brass filter created a positive bias, as it was unable to fully compensate for Bias (B) and Uncertainty (K) For Project TRINITY Source B K Laboratory 1.0 1.3 Radiological Spectrum 1.6 1.4 Wearing 0.8 1.1 Backscatter 1.1 1.1 Total Radiological 1.4 1.5 Environmental 1.0 1.1 Overall (Exposure) 1.0 1.4 Conversion to Deep-Dose Equivalent 1.3 1.2 Overall (Deep-Dose Equivalent) 1.8 1.6

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES TRINITY 85 the over-response of the films to low-energy photons. For 100 keV photons, Type K film filtered with 0.020 inches (0.508 mm) of brass over-responded by a factor of 10 (Storm and Bemis 19503. Allowing for other low energy photons that do not produce such a large over-response, the estimated bias is 1.6 for spectral depend ence. Larger uncertainties are associated with laboratory bias estimates at lower and higher exposures. For the lower exposures, the increase is attributed to the imprecision that occurs when films are used at their lower ranges of detection. Some additional uncertainty is introduced by the varying number of films used to determine exposure. For exposures over 3.0 R. the assignment procedure introduces even more uncertainty because of the disagreements between the two D-2 films. For ex- ample, the readings of the D-2 films in one badge were S.4 R and 11.S R while the Type K film in the badge indicated an exposure of 5.4 R. The exposure assigned from these readings was 8.5 R. but it is obvious that a large uncertainty exists. At the highest doses, when both D-2 films and the K film were averaged, a positive bias was created by the unequal weight applied by using both D-2 films. More confidence can be placed on the K film based on the available calibration data, but it represents only one third of the average value. The small numbers of high readings allowed each high exposure to be re- viewed. The overall effect of the film capabilities and assignment procedures is to create a laboratory bias of about 1.3. For the reasons presented above and the fact that the D-2 films were not always used, the uncertainty of the bias estimate is larger than that for lower exposures. Application of Bias and Uncertainty The following table gives deep-dose equivalent values and ranges of deem dose equivalents within the 95% confidence limits resulting from application of the above overall bias and uncertainty factors to film badge readings in the TRINITY series. Film badge readings between 0.2 R and 3.0 R may be converted by multiplying by the factors in the next-to-the-last line of the table, which were obtained from the overall bias and uncertainty factors for TRINITY given above. Readings between 3 and 15 R may be converted by multiplying by the factors in the last line of the table; no exposures above 15 R were recorded. Readings below 0.2 R may be converted by reading directly from the table; these values allow for additional laboratory uncertainty for low readings as described in Section S.B under laboratory Uncertainties.

OCR for page 80
86 FILM BADGE DOSIMETRY TV ATMOSPHERIC NUCLEAR TESTS Deep-Dose Equivalent and 95% Confidence Limits for Project TRINITY Film Badge Best Estimate of 95% Confidence Limits for Exposure Deep-Dose Equivalent Deep-Dose Equivalent (R) (rem) (rem) 0.04 (MDL) 0.02 (0.00,0.05) 0.05 0.03 (0.01, 0.06) 0.06 0.03 (0.02, 0.07) 0~07 ~0.04 (0.02, 0.07) 0.08 0.04 (0.02, 0.08) 0.09 0.05 (0.03, 0.09) 0.10 0.06 (0.03, 0.10) 0.12 - 0.07 (0.04, 0.1 1) 0.14 0.08 (0.05, 0.13) 0.16 0.09 (0.05, 0.15) 0.18 0.10 (0.06, 0.16) 0.20 0.11 (0.07, 0.18) 0.20 OCR for page 80
6 UNCERTAI=YAlIALYSES BY TEST SERIES CROSSROADS Operation CROSSROADS Events 87 Name Date Type Yield (kt) ABLE 07/01/46 BAKER 07/25/46 Airdrop, detonated 21 at 520-foot altitude Underwater, in lagoon, detonated at 90-foot depth on the target ships at the time of the detonations. Most personnel were on the remaining (support) ships of the fleet. Personnel were primarily exposed to radiation during the period when they entered the lagoon after shot BAKER and boarded the target vessels that had been engulfed in a water plume, surface wave and spray resulting from the underwater explosion, during efforts to decontami- nate the ships, beginning ten days after shot BAKER, and during ammunition offloading of target ships that had been towed or sailed to Kwajalein. Because the ABLE detonation was 520 feet above the ocean and 1500 to 2000 feet from the target ships, residual radioactivity in the target array was mostly from neutron activation and it decreased rapidly. Accordingly, the number of film badges issued for ABLE decreased from 1,627 on 1 July to none on 7 July, with a total during this time interval of 2,132 (Berkhouse et al. 1984~. Only 71 badges were issued from 7 July until 24 July, the day before test BAKER. Badges issued from 24 July until 31 August, when most support ships had left Bikini, totaled 8101 (REECo 1982~. This time period included both recoveries after BAKER and attempts to decontaminate target vessels. More than 8000 film badges were issued on a daily basis to about 700 personnel unloading ammunition from target vessels at Kwajalein, beginning about 30 August and continuing until the end of the year (Berkhouse et al. 1984~. The test series was designed with the objective of keeping the daily exposure below 0.1 R. and badges were used to measure the daily exposure in order to limit work activities if a greater exposure was experienced on a single day. Type of Film Badge The film badge contained a single component type K double-emulsion dental film pack. It was covered by a 0.020-inch-thick lead cross filter, the arms of which were bent over the edges of the pack about 1/4 inch. The badge was in a

OCR for page 80
88 FILM BADGE DOSIMETRY IN ATMOSPHERIC NUCLEAR TESTS plastic envelope to minimize damage to the film by exposure to moisture. The badge was intended to cover the exposure range 0-2 R with a minimum detectable exposure of approximately 0.05 R. The lead filter thickness (0.020 inches) was thinner than was later found to be optimum (0.028 inches) for minimizing the excess response of the film emulsion to low energy components of the gamma and x-ray spectrum. Badge Issue and Exchange Badges were intended to be issued on a daily basis. That was the typical experience although a few badges were retained for 2 or 3 days and as long as 9 days. Badges were not issued to all personnel working or living in radiation areas. They were typically issued only to one or a few Rad-Safe monitors in a group. The film badge exposure of the Rad-Safe monitor was intended to be representa- tive of the exposure of all members of the group, a concept called cohort badging. During the major ship decontamination effort between August 4 and 10 there were typically two monitors per 100 personnel. All personnel in aircraft that were within 20 miles of the explosions were badged at the time of the test detonations. About 15% of the Navy personnel in the task force were issued at least one badge sometime during the test series. The largest number of badges issued to one person (a Rad-Safe monitor) was 19. Calibration, Processing, and Interpretation Calibration, processing, and interpretation took place aboard the USS Haven. Calibrations were performed with a radium source at constant distance with variable time to produce exposures varying by approximate factors of 2 between 0.05 R and 2 R. Calibration films were not processed with each batch of films that was developed. The calibrations were assumed to be valid over a series of successive development batches. New calibration curves were made at least for each new emulsion batch from the film badge manufacturer. An unexposed control badge was included in each development batch to determine the base fog of the film. The development temperature was controlled at 68°F but only to + 1°F accuracy (rather than + 0.5°F called for in later test series). Each developed film was read in four positions corresponding to locations under the arms of the lead cross and close enough to the edge to also be under the bent-over ends of the anus. The film density was read to a maximum optical density of 3, correspond- ing to an exposure of about 2 R. The average of the four optical-density readings on one film, minus the density of the unexposed film developed in the same batch, was used with the density versus exposure calibration curve to interpret the exposure to an individual badge. Optical-density readings also were taken in the

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES - CROSSROADS 89 unshielded four corners of each film for beta-exposure determination. As previ- ously discussed in Section 4.B, however, beta-dosimetry results in Operation CROSSROADS were not reliable. Film badges worn at Operation CROSSROADS were subject to the high temperature and humidity of the Pacific test site and were not free of env*on- mental damage in spite of the plastic "tropical" envelope. Recent evaluation of available film badges from that test series indicates substantial film darkening due to environmental damage. This darkening may have been difficult to separate from the density produced by radiation at the low densities typical of most of the films in the archives. Current Availability of Records Only a part of the more than 18~000 films from badges worn at Operation CROSSROADS is currently available. The films from the ammunition unloading operation at Kwajalein, more than 8000 films, are all that are in REECo archives at Las Vegas, Nevada. The film badge records that were made at the time of the tests are generally available. Even though the record keeping at the time of the tests was not uniformly done and penmanship was sometimes poor, 85-90% of the Navy badge records have been matched to individuals. The method of record keeping evolved during the test series. Because of the unexpected level of contamination of the ships following test BAKER, the large number of badges issued led to establishing a card file on each Rad-Safe monitor to record his daily exposures. At the time ammunition was unloaded from the target vessels at Kwajalein, the record keeping was greatly improved, so that each person had his daily and cumulative exposure record kept on a single SxS inch card. Estimated Bias and Uncertainty The following table presents bias and uncertainties that result from different sources. These values are appropriate for exposures greater than 2 R. The laboratory procedures seem to have been well established and free of bias. The broader range within which the temperature was controlled leads to the greater-than-normal value for the laboratory K. The thinner-than-optimum lead filter biases the results to overestimate the exposure and also increases the uncer- tainty in the effect of the filter. Film badge location and backscatter contributions to the exposure bias and uncertainty are similar to those in other test series. The uncertainty in the environmental effects of heat and water are reflected in the K value of 1.3. The bias and uncertainty in conversion of exposure to dose are assigned the values used throughout this report. The lack of a second film component to evaluate exposures greater than

OCR for page 80
go FILM BADGE DOSIMETRY TV ATMOSPHERIC NUCLEAR TESTS Bias (B) and Uncertainty (K) for Operation CROSSROADS Source B K Laboratory 1.0 1.3 Radiological Spectrum 1.3 1.3 Wearing 0.8 1.3 Backscatter 1.1 1.1 Total Radiological 1.1 1.5 Environmental 1.0 1.3 Overall (Exposure) 1.1 1.7 Conversion to Deep-Dose Equivalent 1.3 1.2 Overall (Deep-Dose Equivalent) 1.5 1.8 approximately 2 R was rarely significant because the individual daily exposures were not this large. Cumulative exposures to a few test participants exceeded 2 R. but the lack of a second film component is only significant on an individual film badge, not on the cumulative exposure derived from several badges. The minimum detectable exposure of 0.05 R is in some places stated as 0.04 R. At this level of exposure, the uncertainty in the exposure deduced from the net film density is larger than this apparent inconsistency. Application of Bias and Uncertainty The following table gives deep-dose equivalent values and range of deep-dose equivalents within the 95% confidence limits resulting from application of the above overall bias and uncertainty factors to film badge readings in the CROSS- ROADS series. Film badge readings above 0.2 R may be converted by multiply- ing by the factors in the last line of the table, which were obtained from the overall bias and uncertainty factors for CROSSROADS given above. Readings below 0.2 R may be converted by reading directly from the table; these values allow for additional laboratory uncertainty for low readings, as described in Section S.B under L aboratory Uncertainties.

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES DOMINIC I Operation DOMINIC I Events 175 Event Type Yield ADOBE 04/25/62 Airdrop 20 to 1000 kt AZTEC 04/27/62 Airdrop 20 to 1000 kt ARKANSAS 05/02/62 Airdrop Low megaton FRIGATE BIRD 05/06/62 Rocket YUKON 05/08/62 Airdrop 20 to 1000 kt MESILLA 05/09/62 Airdrop 20 to 1000 kt MUSKEGON 05/11/62 Airdrop 20 to 1000 kt SWORDFISH 05/11/62 Underwater <20 kt ENCINO 05/12/62 Airdrop 20 to 1000 kt SWANEE 05/14/62 Airdrop 20 to 1000 kt CHETCO 05/19/62 Airdrop 20 to 1000 kt TANANA 05/25/62 Airdrop <20 kt NAMBE 05/27/62 Airdrop 20 to 1000 kt ALMA 06/08/62 Airdrop <20 kt TRUCKEE 06/09/62 Airdrop 20 to 1000 kt YESO 06/10/62 Airdrop 20 to 1000 kt HARLEM 06/12/62 Airdrop 20 to 1000 kt RINCONADA 06/15/62 Airdrop 20 to 1000 kit DULCE 06/17/62 Airdrop 20 to 1000 kt PETIT 06/19/62 Airdrop <20 kit OTOWI 06/22/62 Airdrop 20 to 1000 kt BIGHORN 06/27/62 Airdrop Megaton range BLUE S TONE 06/30/62 Airdrop Low megaton Personnel Exposed Because all of the DOMINIC I tests, except the underwater test, were high- altitude airbursts, little or no fallout resulted and no residual radioactivity re- mained at surface ground zero, except for a radioactive pool of water after the underwater test Film badge readings thus were generally low, wi~ maximum exposures being reported for cloud-sampling pilots and crews, Navy personnel on the USS sioux who sampled the radioactive water pool, personnel who retrieved instrumentation pods and rocket nosecones, and Rad-Safe monitors. An attempt was made to monitor all participants who had- a potential for exposure, in a con- tinuation of REDWING and HARDTACK I film badging policies. About 25,300

OCR for page 80
176 FILM BADGE DOSIMETRY TV ATMOSPHERIC NUCLEAR TESTS individuals were film badged. About 3,000 participants on remote islands, however, who were manning radiation detection instruments or conducting ex- periments at a distance from the tests, were not badged (Berkhouse et al. 1983b). About 43,000 film badges were used. Two dosimetry sections processed about 33,000 badges. The remaining approximately 10,000 badges were processed at the Nevada Test Site Rad-Safe laboratory after DOMINIC I (Mudgett 1964; Brady 1982~. Type of Film Badge The film badge design used in DOMINIC I was the same as in HARDTACK I, a Du Pont packet with a 0.028-inch-thick lead filter dipped in wax and sealed in a rigid PVC holder. The DuPont packet, however, was not the 559 with Type 502 and 508 components, but the 556 with Type 508 (0.02 - 10 R) and Type 834 (5-800 R) components. The badge was designed to be moisture-resistant, and it apparently functioned as intended during HARDTACK I. Near the end of DOM- INIC I, however, sealing of the case was found to be defective, and some badges exhibited considerable excess film optical density from moisture damage (Knipp 1963~. In addition, some 100 films were damaged when a band saw used to cut open the film badge cases nicked the film packets, causing light leaks and resulting in considerable excess optical density (Brady 1982~. Other limitations of the film badge used during the two test series were spectral response, angular response, shielding by the body, and environmental effects not discussed above. These limitations were discussed under Type of Film Badge and Estimated Bias and Uncertainty in the section on HARDTACK I, and the same bias and uncertainties apply to DOMINIC I, with certain exceptions involving environmental effects. While the HARDTACK I radiological safety report stated that film badges could be worn for six months with no significant failure observed, examination of DOMINIC I films showed some environmental damage, increasing with the time film badges were worn or not returned. A large number of DOMINIC badges were worn or not returned for long periods of time, up to three or more months. This damage could be attributed to heat and emulsion ageing, also observed with badges used in continental desert environment tests, where humidity and moisture are not the problems. Damage of this type causes increased optical density with accompanying overestimates of exposure. Considering that only participants in the four categories previously mentioned should have had positive film badge readings, it is likely that almost all other reported exposures were the result of environmentally damaged film badge emulsions. Remaining limitations of film badges related to field use include various types of physical damage to the film packets. As in HARDTACK I, most of these were

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES DOMINIC I 177 avoided by use of the hard plastic case protecting the film packets. Only the band- saw damage observed for a small percentage of DOMINIC I packets appears to be a problem not easily dealt with by investigation of individual exposure conditions. Film-component overlap limitations were discussed in Section 4.D. Figure 44 shows that selection of the Type 502 and 834 components essentially solved the overlap problems with previously used film-component types. The response- curve slope in the overlap region of Figure 44 changes very little, compared to other combinations, indicating little change in uncertainty for exposures in the overlap range. Badge Issue and Exchange Two dosimetry sections were required for the DOMINIC I Operation. One was at Christmas Island and the other in Honolulu, Hawaii. The Dosimetry section on Christmas Island was responsible for firm processing for the Johnston Island site and Barbers Point personnel (Knipp 1963~. Film badge support locations and their functions for DOMINIC I were as follows: Christmas Island: Film-badge issue and collection Photodosimetry services Johnston Island: Film-badge issue and collection Honolulu: Photodosimetry services Nevada Test Site: Photodosimetry services (Mudgett 1964; Knipp 1963) 04/25/62-07/11/62 06/03/62-11/03/62 03/15/62-11/10/62 11/07/62-01/30/63 DOMINIC I Radiological Safety Regulations, Annex J to Op Plan 2-62 (Star- bird 1962), stated that "All task-force personnel will be required to wear film badges. Certain cases may arise, such as outlying stations, where such a require- ment may not be practical." The regulations also stated that "all persons in aircraft at shot time, or at subsequent times, shall wear film badges when engaged in operations in or near the cloud or RADEX (radiation exclusion area) track." Badge issuance was relatively complete; that is, almost all individuals who could be considered participants were badged. Personnel on remote islands

OCR for page 80
178 FILM BADGE DOSIMETRY IN ATMOSPlIERIC NUCLEAR TESTS providing support at a distance from the tests were not issued film badges. On Christmas Island, Task Group 8.4 (Air Force personnel) assisted in film badge issue and return. This task unit was responsible for issuing firm badges to sampling aircrew mission members (including pilots, crew, and ground person- nel). After each mission, Task Group 8.4 would collect all film badges used on the mission and return them to the JTE-8 dosimetry section for development (they were processed within 6 hours). Badges also were exchanged weekly for all 8.4 personnel exposed to radiation. Task Group TO 8.4 also maintained a record which listed all Task Group 8.4 personnel exposed to ionizing radiation. Ap- proximately 2,500 film badges were issued by this task group. Near the end of the operation, the Christmas Island photodosimetry operation was closed and relo- cated with the Honolulu group (Knipp 1963~. Dosimetry record cards (5x8-inch cards) were prepared in the Honolulu sec- tion. Approximately 20,000 Sx8-inch dosimetry cards were typed and initial doses posted (Knipp 1963~. Use of the charge-a-plate identification system adopted for previous Pacific test series was initiated after the DOMENIC 1 operation began (Mudgett 1964~. The Honolulu Photodosimetry section was closed November 1, 1962 (Allen 1962; Rueter 1962~. Photodosimetry equipment and both unexposed and exposed films were sent to the Nevada Test Site (NTS) for completion of processing and posting of exposure records. The NTS photodosimetry section processed am proximately 10,000 film badges and posted approximately 30,000 records. These records then were finalized and coded for ADP (automatic data processing) keypunching. These dosimetry records were retained by Reynolds Electrical & Engineering Company, Incorporated (REECo) (Brady 1982~. Calibration, Processing, and Interpretation Calibration of film badges during DOMINIC I was in accordance with the Los Alamos Scientific Laboratory procedures and included use of a cobalt 60 source, a recently NBS-calibrated it-meter, and constant time-variable distance calibra- tion exposures. Master calibration curves were prepared, and control and stan- dard films were developed with each batch of personnel films. Film development was under controlled and timed conditions at a temperature of 68 + 0.5°F (Lit- tlejohn 198Sc). During DOMINIC I, Joint Task Force ~ was responsible for radiological safety. George Littlejohn of Los Alamos trained the RSSU dosimetry personnel and developed films at the Christmas Island Facility with assistance from Holmes and Narver (the AEC support contractors personnel. Mechanical difficulty with the curve follower first used in HARDTACK I prevented its use during DOM

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES DOMINIC I 179 INIC I, and the REDWING procedure of manually posting film badge results on Sx8-inch cards for each individual was resumed. Eberline FD-II densitometers were used at both the Christmas Island and Honolulu, Hawaii, facilities. Current Availability of Records Stored in the archives of REECo at Las Vegas, Nevada, are processed films from DOMINIC I film badges, 5x8-inch card individual exposure records, NavMed 1432 forms listing personnel and their exposures by film badge on specific ships, an alphabetical summary report of DOMINIC I participants and their exposures, for about 75 percent of the film badges issued, supplementary reports for the remaining 25 percent of the film badges processed at N1S, and organizational reports listing data from both the summary and supplementary reports. Esimated Bias and Uncertainty Estimated bias and uncertainties for DOMINIC I film badge exposures greater than 200 mR are listed in the following table. Also included are overall B and K for exposure, B and K for conversion to dose, and overall B and K for dose. These B and K values, however, apply to only some of the DOMINIC I film badge results, as discussed after the table. Bias (B) and Uncertainty (K) for Operation DOMINIC I Source B K Laboratory 1.0 1.2 Radiological Spectrum 1.1 1.2 Wearing 0.S 1.2 Backscatter 1.1 1.1 Total Radiological 1.0 1.3 Environmental 1.2 1.1 Overall (Exposure) 1.2 1.4 Conversion to Deep-Dose Equivalent 1.3 1.2 Overall (Deep-Dose Equivalent) 1.5 1.5 1

OCR for page 80
180 FILM BADGE DOSIMETRY IN ATMOSPIlERIC NUCLEAR TESTS The environmental bias of 1.2 expresses a normal positive bias for environ- mental damage in the Pacific' not related to radiation exposure. While sealing of the film badge cases used during HARDTACK I apparently was adequate, and the bias of 1.2 applies, sealing of the cases for DOMINIC I was not adequate. Sealing failure resulted in moisture damage, and, together with long wearing periods and long times before processing, resulted in a large number of film badges which indicated exposure when no exposure had occurred. DOMINIC I film badge exposures should be related to known activities of the wearers. If an individual was not in a cloud-sampling and crew unit, not on the ship (USS Sioux) that sampled water from the radioactive pool, not involved in recovering instrument pods, nosecones, or other contaminated or activated material, or not a Rad-Safe monitor, then any indicated film badge exposure was likely to have been caused by environmental damage. The above B'and K, then, apply primarily to film badge results of personnel who were in categories of pamcipants that may have been exposed to gamma radiation, and thus whose film badges were exchanged more frequently than the majority. Light damage from the band saw used to open film badge cases apparently occurred in DOMINIC I. Less than 100 badges were involved, and most of these have been reevaluated to verify reductions in exposure previously made by 1st RSSU personnel. All of the apparent exposures caused by band-saw damage light leaks have been verified as reduced to less than 3 R. except for about six film badges worn on the ship which was sampling water from the radioactive pool. Application of Bias and Uncertainty The following table gives deep-dose equivalent values and ranges of deep- dose equivalents within the 95% confidence limits resulting from application of the above overall bias and uncertainty factors to film badge readings in the DOM- INIC I series. Film badge readings above 0.2 R may be converted by multiplying by the factors in the last line of the table, which were obtained from the overall bias and uncertainty factors for DOMINIC I given above. Readings below 0.2 R may be converted by reading directly from the table; these values allow for additional laboratory uncertainty for low readings, as described in Section 5.B under Laboratory Uncertainties.

OCR for page 80
6 UNCERTAI~IY ANALYSES BY TEST SERIES DOMINIC 11 181 Deep-Dose Equivalent and 95% Confidence Limits for Operation DOMINIC I Film Badge Best Estimate ofDeep- 95% Confidence Limits for Exposure Ddse Equivalent Deep-Dose Equivalent (R) (rem) (rem) 0.04 (MDL) O.03 (0.00, 0.06) 0~05 0.03 (0.02, 0.07) 0.06 0~04 (0.02, 0.08) 0.07 0.05 (0.03, 0.08) 0.08 0.05 (0.03, 0.09) 0.09 0.06 (0.04, 0.10) 0.10 0.07 (0.04, 0.1 1) 0.12 0.0X (0.05, 0.13) 0.14 0.09 (0.06, 0.15) 0.16 0.11 (0.07, 0.16) 0.18 0.12 (0.08, 0.18) 0.20 0.13 (0.09, 0.20) >0.20 0.67 E (0.44 E, 1.00 E) where E is the film badge exposure (my Use of the Type 834 film component to replace the Type 606 essentially solved the overlap problem previously experienced in the 10 - 15 R range (see Section 4.D). OPERATION DOMINIC II Background Operation DOMINIC II (named Operation SUNBEAM by DOD) was con- ducted during mid-July at the Nevada Test Site (NTS). Four weapons were detonated to obtain data about the effects of low-yield explosions. Ancillary experiments were performed to evaluate the ability to detect nuclear detonations in foreign countries. This Operation was comprised of the four tests listed below. Associated with Little Feller I was a military maneuver, Exercise IVY FLATS. This exercise

OCR for page 80
182 FILM BADGE DOSIMETRY IN ATMOSPHERIC NUCLEAR TESTS centered on the test of a Davy Crockett weapon fired from a mobile rocket launcher under simulated tactical conditions. Operation DOMINIC II Events Event Date Type Yield(kt) LITTLE FELLER II 07/07/62 Surface Low* JOE BOY 07/11/62 Surface 0.5 SMALL BOY 07/14/62 15-foot tower Low* LITTLE FELLER I 07/17/62 Surface Low* *Low is less than 20 kt Personnel Exposed The actual number of people involved in conducting the Operation is unknown and difficult to reconstruct because all persons at the NTS wore film badges. Other nuclear testing programs were ongoing at NTS concurrent with Operation DOMINIC II. Many personnel from the Atomic Energy Commission and its contractors supported these programs and are not uniquely associated with one operation. The films and records are stored by process date and not by operation. Over 200,000 film badges were processed at NTS during 1962 for a permanent work force of several thousand personnel, and for transients of an equal or greater number. Approximately 3000 DOD-affiliated personnel participated in the DOMINIC II operation. The highest exposure received at NTS during the DOMINIC II operational period was 5.8 R. Type of film Badge The film badge for Operation DOMINIC II was the standard badge used at the NTS during 1962. Also used during Operation HARDTACK II, the badge consisted of a Du Pont Type 559 film packet containing Type 502 and Type 834 components with 0.028-inch-thick lead strip covering part of the front and back surfaces. The badge was enclosed in a polyethylene bag, 0.004 inches thick.

OCR for page 80
6 UNCERTAINTY ANALYSES BY TEST SERIES ~ DOMINIC II 183 The U.S. Army created a separate radiation safety program for IVY FLATS within the NTS program. REECo provided technical support which included radiation-safety training, film badges, and instruments. All IVY FLATS par~tici- pants wore the NTS film badge. Records were established for all issued badges. Upon issue of film badges, individual IBM identification cards aided the process of relating a person to a film badge number. Badge Issue and Exchange The procedures for issuing and exchanging film badges were the same as those that had been used since 1957. The Radiological Safety Division of REECo, the site operating contractor, supervised all aspects of the- film badge program. Key to the issuance and exchange program was the union of the film badge with the security badge. Security officials were instructed to verify that an appropriate film badge was worn as an individual passed through various check points at the test site. Identification of the film badge was coded by an identifica- tion plate and colored tape. Different colors signified different monthly issue periods. Film badges were issued at the main gate and the site control point by REECo staff. Participants in Exercise IVY FLATS were issued badges by Army person- nel under the REECo Rad Safe Program. Air Force personnel issued badges supplied by REECo at Indian Springs and Kirtland Air Force Bases only to pilots, crew or others whose duty could result in exposure to radiation. Badges were collected after entry to a radiation area, or if an exposure greater than 0.1 R was suspected. Badges were processed the evening of their collection so that exposure record cards could be updated by the next day. These cards were reviewed when permits were granted for access to radiation areas. Calibration, Processing, and interpretation Calibration, processing and evaluation procedures had been implemented by REECo in 1955 and had continued during the 1957 PLUMBBOB, 1958 HARD- TACK II, and interim operations at the NTS. These were continued during Operation DOMINIC II. Films were calibrated with a cobalt 60 source. Cali- brated films were processed with each developed batch of films worn by opera- tion participants, as were two unexposed control films to account for base fog (REECo 1958~. After developing and drying, films were analyzed with an Eberline Model FD-II densitometer. The film net optical density under the lead filter was used to determine whole body exposure.

OCR for page 80
184 FILM BADGE DOSIMETRY IN ATMOSPHERIC NUCLEAR TESTS Current Availability of Records All films, issue cards, and exposure records for the 'DOMINIC II Operation period are stored at the REECo/DOE repository in Las Vegas. Estimated Bias and Uncertainty The film badge program at the NTS had served previous operations. Experi- enced staff and proven methods minimized the number and types of problems. The table below presents bias estimates and uncertainties for exposures greater than 0.2 R. 'The performance of the 502 film was 'examined in a REECo report (1957~. Laboratory reproducibility was good. The report noted decreased relative preci- sion at low exposures. As discussed previously under DOMINIC I, use of the Type 502 and Type 834 film components t essentially solved the overlap problem (See Figure 44~. Unlike some other operations, additional uncertainties from long wearing periods and environmental factors were not significant because the operation was of short duration and moisture damage was not a problem. The number of one-day participants in IVY FLATS also minimized the impact of environmental effects that would be more likely to affect monthly badges. Film badges were exchanged when personnel exited radiation areas and exposures of 100 mR or more were expected. Otherwise, badges were exchanged monthly. Overall, film badge uncertainties for Operation DOMINIC II were among the lowest of the atmospheric testing program. Bias (B) and Uncertainty (K) for Operation DOMINIC II Source B K Laboratory 1.0 1.2 Radiological Spectrum '1.1 1.2 Wearing 0.8 1.1 - Backscatter 1.1 - 1.1 Total Radiological 1.0 1.3 Environmental 1.0 1.1 Overall (Exposure) 1.0 1.4 Conversion to Deep-Dose Equivalent 1.3 1.2 Overall (Deep-Dose Equivalent) 1.3 1.4

OCR for page 80
6 UNCERTAIN-I Y ANALYSES BY TEST SERIES DOMINIC II Application of Bias and Uncertainty 185 The following table gives deep-dose equivalent values and ranges of deep- dose equivalents within the 95% confidence limits resulting from application of the above overall bias and uncertainty factors to film badge readings in the DOM- INIC II series. Film badge readings above 0.2 R may be converted by multiplying by the factors in the last line of the table, which were obtained from the overall bias and uncertainty factors for DOMINIC II given above. Readings below 0.2 R may be converted by reading directly from the table; these values allow for additional laboratory uncertainty for low readings as described in Section 5.B under Laboratory Uncertainties. Deep-Dose Equivalent and 95% Confidence Limits for Operation DOMINIC II Film Badge Best Estimate of Deep- 95% Confidence Limits for Exposure Dose Equivalent Deep-Dose Equivalent (R) (rem) (rem) 0.04 (MDL) 0.03 (0.00,0.07) 0.05 0.04 (0.02, 0.08) 0.06 0.05 (0.03, 0.08) 0.07 ~0.05 (0.03, 0.09) 0.08 0.06 (0.04, 0.10) 0~09 0.07 (0.04,0.11) 0.10 ~0.08 (0.05, 0.12) 0.12 0.09 (0.06, 0.14) 0.14 0.11 (0.07, 0.16) 0.16 0.12 (0.08, 0.18) 0.18 0.14 (0.10, 0.20) 0.20 0.15 (0.1 1, 0.22) >0.20 0.77 E (0.55 E, 1.08 E) where E is the film badge exposure (R) Use of the Type 834 film component to replace the Type 606 essentially solved the overlap problem previously experienced in the 10 - 15 R range (see Section 4.D).