Dose assessment for reentry or reoccupancy and recovery of urban areas contaminated by a radiological dispersal device: the need for a consensus approach.

Should an attack occur in an urban area with a Radiological Dispersal Device (RDD), guidance is available on the acceptable total dose equivalent for reentering the contaminated zone, and there is an accepted methodology for plume projection in the model used by the Federal Radiological Monitoring and Assessment Center (FRMAC). After initial characterization of the impact of the plume caused by an RDD, there will be considerable pressure from the public to allow them to return and quickly collect their belongings, and, eventually, to reoccupy residences and to reopen businesses. The FRMAC procedures principally deal with early and intermediate phase dose assessment, but do include late phase assessment procedures. However, the late phase assessments do not include complex geometries, such as the internal structure of buildings. This paper identifies areas where more specificity is needed to rapidly provide assessments to health officials and senior decision-makers. In this regard, there is no national consensus method to calculate projected dose inside buildings after an RDD event that addresses selecting the exposure pathways, scenarios, key parameters, etc. Therefore, to demonstrate an approach that exemplifies some of the technical and policy issues, which are unresolved, four exposure scenarios (residential, industrial, public park, park worker) were evaluated to determine the level of contamination that would deliver a dose equivalent of 10 mSv in the first year, excluding exposure during the first 4 d (emergency phase). In addition, the retrieval of personal belongings was simulated by assessing a 1-h exposure for the residential and industrial scenarios. RESRAD-BUILD was used to calculate the surface concentration of 60Co, 90Sr, 137Cs, 192Ir, 226Ra, 238Pu, 241Am, and 252Cf that would lead to a 10 mSv reference dose for these exposure periods. These example studies are intended to provide insights and guidance on how a municipal health agency can begin to develop a response plan, and to understand how the assessment process will determine the dose impacts resulting from an RDD event. The model's predictions heavily depend on the choice of the model's parameters; for several key ones, there are large uncertainties about their appropriate values. To avoid having to make hasty decisions during an emergency after an RDD attack, this analysis demonstrates that a detailed protocol for calculating dose should be developed prospectively so that decision-makers already are fully familiar with the process and its ensuing products.

Evaluation of an iron-filtered epithermal neutron beam for neutron-capture therapy.

An epithermal neutron filter using iron, aluminum, and sulfur was evaluated to determine if the therapeutic performance could be improved with respect to aluminum-sulfur-based filters. An empirically optimized filter was developed that delivered a 93% pure beam of 24-keV epithermal neutrons. It was expected that a thick filter using iron with a density thickness greater than 200 g/cm2 would eliminate the excess gamma contamination found in Al-S filters. This research showed that prompt gamma production from neutron interactions in iron was the dominant dose component. Dosimetric parameters of the beam were determined from the measurement of absorbed dose in air, thermal neutron flux in a head phantom, neutron and gamma spectroscopy, and microdosimetry.

An estimate by two methods of thyroid absorbed doses due to BRAVO fallout in several Northern Marshall Islands.

Estimates of the thyroid absorbed doses due to fallout originating from the 1 March 1954 BRAVO thermonuclear test on Bikini Atoll have been made for several inhabited locations in the Northern Marshall Islands. Rongelap, Utirik, Rongerik and Ailinginae Atolls were also inhabited on 1 March 1954, where retrospective thyroid absorbed doses have previously been reconstructed. The current estimates are based primarily on external exposure data, which were recorded shortly after each nuclear test in the Castle Series, and secondarily on soil concentrations of 137Cs in samples collected in 1978 and 1988, along with aerial monitoring done in 1978. The external exposures and 137Cs soil concentrations were representative of the atmospheric transport and deposition patterns of the entire Castle Series tests and show that the BRAVO test was the major contributor to fallout exposure during the Castle series and other test series which were carried out in the Marshall Islands. These data have been used as surrogates for fission product radioiodines and telluriums in order to estimate the range of thyroid absorbed doses that may have occurred throughout the Marshall Islands. Dosimetry based on these two sets of estimates agreed within a factor of 4 at the locations where BRAVO was the dominant contributor to the total exposure and deposition. Both methods indicate that thyroid absorbed doses in the range of 1 Gy (100 rad) may have been incurred in some of the northern locations, whereas the doses at southern locations did not significantly exceed levels comparable to those from worldwide fallout. The results of these estimates indicate that a systematic medical survey for thyroid disease should be conducted, and that a more definitive dose reconstruction should be made for all the populated atolls and islands in the Northern Marshall Islands beyond Rongelap, Utirik, Rongerik and Ailinginae, which were significantly contaminated by BRAVO fallout.

Protracted exposure to fallout: the Rongelap and Utirik experience.

From June 1946 to August 1958, the U.S. Department of Defense and the U.S. Atomic Energy Commission (AEC) conducted nuclear weapons tests in the Northern Marshall Islands. On 1 March 1954, BRAVO, an above-ground test in the Castle series, produced high levels of radioactive material, some of which subsequently fell on Rongelap and Utirik Atolls due to an unexpected wind shift. On 3 March 1954, the inhabitants of these atolls were moved out of the affected area. They later returned to Utirik in June 1954 and to Rongelap in June 1957. Comprehensive environmental and personnel radiological monitoring programs were initiated in the mid 1950s by Brookhaven National Laboratory to ensure that body burdens of the exposed Marshallese subjects remained within AEC guidelines. Their body-burden histories and calculated activity ingestion rate patterns post-return are presented along with estimates of internal committed effective dose equivalents. External exposure data are also included. In addition, relationships between body burden or urine-activity concentration and declining continuous intake were developed. The implications of these studies are: (1) the dietary intake of 137Cs was a major component contributing to the committed effective dose equivalent for the years after the initial contamination of the atolls; (2) for persons whose diet included fish, 65Zn was a major component of committed effective dose equivalent during the first years post-return; (3) a decline in the daily activity ingestion rate greater than that resulting from radioactive decay of the source was estimated for 137Cs, 65Zn, 90Sr and 60Co; (4) the relative impact of each nuclide on the estimate of committed effective dose equivalent was dependent upon the time interval between initial contamination and rehabilitation; and (5) the internal committed effective dose equivalent exceeded the external dose equivalent by a factor of 1.1 at Utirik and 1.5 at Rongelap during the rehabitation period. Few reliable 239Pu measurements on human excreta were made. An analysis of the tentative data leads to the conclusion that a reliable estimate of committed effective dose equivalent requires further research.

Comments on "Breast cancer: evidence for a relation to fission products in the diet".

For over 30 years, Ernest Sternglass (recently joined by Jay Gould) has claimed that large occurrences of health effects result from small exposures to ionizing radiation. A recent study published in the Journal claimed to show a "supralinear" dose-effect relationship versus curies per million persons. The authors of this article show that Sternglass and Gould did not follow accepted scientific methods, never calculated the dose equivalent to the population studied, misinterpreted the raw data, and did not evaluate any possible confounding factors that could influence the observed breast cancer mortality. The reanalysis of the raw data shows that, while there may have been changes in the mortality patterns from breast cancer in the four geographical regions reported, Sternglass and Gould failed to demonstrate a relationship between the operational histories of the Haddam Neck, Millstone, and Indian Point reactors and breast cancer mortality.

Radiation protection and environmental management at the relativistic heavy ion collider.

The Relativistic Heavy Ion Collider (RHIC) is a high energy hadron accelerator built to study basic nuclear physics. It consists of two counter-rotating beams of fully stripped gold ions that are accelerated in two rings to an energy of 100 GeV/nucleon or protons at 250 GeV/c. The beams can be stored for a period of five to ten hours and brought into collision for experiments during that time. The first major physics objective is to recreate a state of matter, the quark-gluon plasma, that has been predicted to have existed at a short time after the creation of the universe. Because there are only a few other high energy particle accelerators like RHIC in the world, the rules promulgated in the US Code of Federal Regulations under the Atomic Energy Act, State regulations, or international guidance documents do not cover prompt radiation from accelerators to govern directly the design and operation of a superconducting collider. Special design criteria for prompt radiation were developed to provide guidance tor the design of radiation shielding. Environmental Management at RHIC is accomplished through the ISO 14001 Environmental Management System. The applicability, benefits, and implementation of ISO 14001 within the framework of a large research accelerator complex are discussed in the paper.