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Fact Sheet – Page 3

Courtesy of MM2 Dick Lund (56-60)


The third part, also sponsored by DOD, addressed a military problem that was newer: nuclear weapons in air and ballistic missile defense. The HARDTACK tests directed toward this problem consisted of three high-altitude shots, two of which (TEAK and ORANGE) were rocket borne and conducted at Johnston Island. The third of these high-altitude tests. YUCCA, was carried aloft by a balloon over the ocean between Enewetak and Bikini. These high-altitude tests used device placemant techniques and data-recording operations that were new to nuclear weapons testing.

Central to the test series was the experimental program. This program and its requirements dictated the form of the test organization and the detail of personnel participation. HARDTACK’s experimental program incorporated two aspects, the first of which was the development of the weapons themselves, and the second involved the measurement of the explosive and radiation effects. Unlike earlier nuclear test series, the HARDTACK test operartions supporting each aspect were in large part separate.

These two aspects can serve as a rough measure of differentiation of interest between the major particpants: the AEC interest in weapon developemnt, and the DOD interest in the military application of the effects of the explosions. The servearl perts of the weapon development and effects studies each had particular features that led to the possibility of radiation exposure.


For Operation HARDTACK, CJTF 7 was directed to “assume overall resopnsibility for the radiological safety of Task Force personnel and of populated islands.” To carry out this responsibilty, the JTF 7 Operation Plan further directed that a Fallout Plotting Center be set up and the capability be established to keep the task force in CINCPAC informed of the fallout situation at all times, including the annoucement of safe reentry times. Fallout stations were to be set up and technical assistance given to personnel in the Trust Territory of the Pacific Islands. Monitors and couriers were to be provided for radioactive sample centers.

In addition, the Operation Plan specified that task group commanders establish radiation safety (radsafe) units within the task groups iwth adeaquate sepcial clothing and radiac instrumentation. Task groups were also to provide a roster of their personnel for film badge preparation.

The radsafe program for Operation HARDTACK was divided into two parts: on-site and offsite. Onsite radsafe activities were conducted by the various task groups, with the scientific task group given the responsibility for all radsafe functions associated with diagnostic experimental programs and for dosimetry and other technical services to the entire task force. The operation of the offsite program and the coordination of the onsite activities were conducted by the Radsafe Office of Hq JTF 7.


A maximum permissible exposure (MPE) for personnel was set at 3.75 roentgens (R) (gamma only) per consecutive 13-week period with a maximum of 5 R for the operation. Exceptions were made for emergency and other tactical situations. The operation was defined as the period from 15 days before the first ready date to 15 days after the last shot. A special MPE of 10 R or emergency, and additional exposure of 10 R would be accepted. Any exposure in excess of 20 R total would be considered as an overexposure for aircrew samplers.

The limit of 3.75 R per 13-week period was slightly greater than the National Council on Radiation Protection and Measurements and the International Commission on Radiation Protection limit of 3 R per 13-week period in effect at the time. The limit of 5 R for the operation is equivalent to the exposure currently permitted per year by Federal guidelines for radiation workers. Appropriate remarks were to be included in the medical records of personnel who exceeded the 3.75 and 5 R limits. Military personnel were to be advised that they should not be exposed to furher radiation until sufficient time elapsed to bring their average radiation exposure down to 0.3 R/week. Civilian personnel in the category were to be informed that limitations of further radation exposure were to be determined by the laboratory or agency having administrative jurisdiction over such personnel.

A film badge program provided an exposure-indicating device to all JTF 7 personnel to maintain complete exposure information on everyone entering the EPG during the operation. The commander of the scientific task group assigned overall badging responsibility to a special task unit. Beginning 1 April 1958, film badges were issued to all individuals upon their arrival at the EPG with instructions that the badge be worn at all times and turned in on recall, upon exit from any contaminated area, or upon departure from the EPG.


The table on the following page documents the numbers and percent of task force personnel who received exposures in various categories. These data are based on the latest data available and may be added to as research is completed. Of the some 19,600 individuals baadged on HARDTACK, 99 percent had exposures that did not exceed the current Federal guidelines of 5 R per year. The highest recorded exposure for the series was 12.41 R. The overall joint task force mean exposure was 0.87 R.

During the conduct of the series only one incident occurred of an exposure of a large group of JTF 7 personnel to significanyly elevated radiation levels. This happened on 14 May with the base insland (Enewetak and Parry) at Enetetak Atoll received fallout from a test shot that had been detonated at Bikini two days before. This fallout episode, which lasted about 60 hours, could have contributed as much as 1.2 to 1.5 R total dose to personnel on Enewetak Atoll adepnding upon the island on which they lived and their work activities. However, since nearly all personnel wore film badges, this fallout exposure is reflected in the film badge doses.

There was one known incident of offsite fallout. Two Japanese research vessels operationg outside the danger area set up around the EPG detected an increase in radiation after shot POPLAR. An investigation by the JTF 7 Staff Surgeon revealed that this exposure was small , amounting to, at most, 0.085 R for the crew, and even this figure did not reflect the decontamination procedures that were used to lower the contamination.

The detonations during HARDTACK I, including those at Johnston Island, did not expose the Hawiian Islands to fallout.

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