Conditions at Bikini Atoll
Radiological Conditions at Bikini Atoll and the Prospects of Resettlement
The IAEA was requested by the Government of the Marshall Islands to review the former nuclear test sites at Bikini Atoll.
Background and history
Bikini Atoll is located 850 kilometers northwest of Majuro on the northern fringe of the Marshall Islands and is composed of more than 23 islands and islets. Four islands (Bikini, Eneu, Nam and Enidrik) account for over 70% of the land area. Bikini and Eneu are the only islands of the atoll that have had a permanent population.
In 1946, Bikini Atoll was the first site in the Marshall Islands used for nuclear-weapon testing by the United States. In 1948, Enewetak Atoll, a neighboring atoll, replaced Bikini Atoll as the test site. In 1954, Bikini Atoll was reactivated as a test site until the US terminated nuclear-weapon testing in the Marshall Islands in 1958.
Prior to the first nuclear test in 1946, the 167 Bikinians living on Bikini Island were evacuated to neighbouring islands.
By the time nuclear-weapon testing in the Marshall Islands was terminated in July 1958, sixteen nuclear-weapon tests had been conducted on Bikini Atoll over a 12-year period. All of these tests were surface or atmospheric tests. They were conducted in or over the Atoll lagoon, thereby dispersing the explosion’s effects over all of the islands of the Atoll.
The history of the radiological assessments and the movement of the local population is very important in understanding the overall concerns. In August 1968 — following a number of radiological surveys that had been carried out since 1958 to assess the impact of the US programme of nuclear-weapon testing — it was announced that Bikini Atoll was safe for habitation and approved for resettlement. A further radiological survey of Bikini Atoll was carried out in 1970.
Eventually, 139 Bikinians resettled on the Atoll. However, the Bikinian people remained unconvinced of the safety of the Atoll, and in 1975 they initiated a lawsuit against the US Government to terminate the resettlement effort until a satisfactory and comprehensive radiological survey had been carried out.
Additional radiological data were collected for evaluation in 1975, 1976, and 1978. In September 1978 it was decided to relocate the 139 Bikinians who had returned to Bikini Atoll back to Kili Island and to Ejit Island at Majuro Atoll.
After a second relocation, a new radiological survey, sponsored by the United States, was performed. This survey consisted of using detectors mounted in helicopters to plot contours of external gamma dose rates. Also, samples of vegetation, marine foods, animals and soil were collected and analyzed. Revised radiation dose evaluations were published in 1980 and 1982. They indicated that — should the Bikinians decide to resettle their island — the terrestrial food chain would be the most significant exposure pathway. This dose assessment was most recently updated in 1995 on the basis of a continuing measurement programme at the Atoll.
Following the US survey, the Government of the Republic of the Marshall Islands commissioned a separate radiological assessment. By this means, Bikini Atoll, as well as all other atolls in the Republic, were to be monitored for radioactive residues. A Scientific Advisory Panel of well-known and respected scientists provided oversight. Laboratory quality control programmes were implemented to ensure that the surveys could provide accurate measurements and reproducible data. In general, the study confirmed the findings of earlier measurement programmes. The findings of the survey were published and a report on Bikini Atoll was released in February 1995.
In August 1995, six months after the survey report was issued, the Nitejela (Parliament) of the Marshall Islands considered the survey findings but it did not accept them.
In 1994, the Government of the Marshall Islands requested the IAEA to conduct an independent international review of the radiological conditions at Bikini Atoll, and to consider and recommended strategies for the resettlement of the atoll. The IAEA responded to this request by convening an Advisory Group, which met in December 1995. The Group was convened under the framework of an IAEA technical co-operation project.
There were three main objectives of the international review:
To assess the radiological conditions on Bikini taking into account the information submitted by the Republic’s Government
To ascertain whether any corroboration of the available information on the current radiological conditions at the Atoll is needed
To determine whether any remedial actions for the purpose of radiation protection were required and, if so, the form, scale and duration of such an intervention
The international review took into account all of the available data from the Marshall Islands’ survey, as well as of a large number of other assessments made by scientists from around the world.
In May 1997, the IAEA sent an environmental monitoring team to Bikini Atoll to perform a limited programme of environmental measurements and sampling. Measurements were made of the absorbed dose rate in the air and of the concentration of the most radiologically significant radionuclides in representative samples of soil and foodstuffs.
The purpose of this survey was to validate the data that had been previously collected. Measurements taken during the survey were generally in good agreement with previously reported values.
Based on its review, the IAEA Advisory Group determined that no further corroboration of the measurements and assessments of the radiological conditions at Bikini Atoll is necessary. The data that have been collected are of sufficient quality to allow an appropriate evaluation to be performed. The limited IAEA monitoring of the area provided a good quality assurance verification of the previously collected data.
It was recommended that Bikini Island should not be permanently resettled under the present radiological conditions. This recommendation was based on the assumption that persons resettling on the island would consume a diet of entirely locally produced food. The radiological data support that if a diet of this type were permitted, it could lead to an annual effective dose of about 15 mSv. This level was judged to require intervention of some type for radiation protection purposes.
There are a number of remedial actions that could be performed that could lead to permanent rehabitation of the island. These include the periodic application of potassium-based fertilizer where edible crops are grown or the removal of the topsoil from the island. Since most of the radioactivity in the plants is due to the uptake of the radioactive caesium, the potassium would replace this element, thereby reducing the overall exposure to the population. The scraping and removal of the topsoil would cause serious environmental harm to the island and have social consequences.
It was also recommended that a simple monitoring programme of the foodstuffs and the population be continued. The purpose of this programme is to provide assurance to the local population that there is no significant uptake of radioactive material into their bodies.
This project was an example of a study where the IAEA was asked to provide an assessment of an existing radiological situation arising from the presence of radioactive residues. It provided this service to a Member State that had legitimate concerns about these situations. By providing this service, the IAEA has helped provide guidance to national authorities on possible actions that can be taken for the purpose of resettlement in areas where there are concerns about existing environmental conditions.
In 1998, the IAEA issued a report — Radiological Conditions at Bikini Atoll: Prospects for Resettlement — that covers the international review in greater detail. In July 1997, the official journal of the Health Physics Society, Health Physics, devoted a special edition to the subject, including papers of direct relevance to questions of resettlement for the people of Bikini Atoll.
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