Workshop report on atomic bomb dosimetry-residual radiation exposure: recent research and suggestions for future studies.

There is a need for accurate dosimetry for studies of health effects in the Japanese atomic bomb survivors because of the important role that these studies play in worldwide radiation protection standards. International experts have developed dosimetry systems, such as the Dosimetry System 2002 (DS02), which assess the initial radiation exposure to gamma rays and neutrons but only briefly consider the possibility of some minimal contribution to the total body dose by residual radiation exposure. In recognition of the need for an up-to-date review of the topic of residual radiation exposure in Hiroshima and Nagasaki, recently reported studies were reviewed at a technical session at the 57th Annual Meeting of the Health Physics Society in Sacramento, California, 22-26 July 2012. A one-day workshop was also held to provide time for detailed discussion of these newer studies and to evaluate their potential use in clarifying the residual radiation exposures to the atomic-bomb survivors at Hiroshima and Nagasaki. Suggestions for possible future studies are also included in this workshop report.

Biophysics and medical effects of enhanced radiation weapons.

Enhanced radiation weapons (ERW) are fission-fusion devices where the massive numbers of neutrons generated during the fusion process are intentionally allowed to escape rather than be confined to increase yield (and fallout products). As a result, the energy partition of the weapon output shifts from blast and thermal energies toward prompt radiation. The neutron/gamma output ratio is also increased. Neutrons emitted from ERW are of higher energy than the Eave of neutrons from fission weapons. These factors affect the patterns of injury distribution; delay wound healing in combined injuries; reduce the therapeutic efficacy of medical countermeasures; and increase the dose to radiation-only casualties, thus potentiating the likelihood of encountering radiation-induced incapacitation. The risk of radiation-induced carcinogenesis is also increased. Radiation exposure to first responders from activation products is increased over that expected from a fission weapon of similar yield. However, the zone of dangerous fallout is significantly reduced in area. At least four nations have developed the potential to produce such weapons. Although the probability of detonation of an ERW in the near future is very small, it is nonzero, and clinicians and medical planners should be aware of the medical effects of ERW.

Medical implications of enhanced radiation weapons.

During the 1960s through 1980s the United States and several other nations developed, and even considered deploying, enhanced-radiation warheads (ERWs). The main effect of ERWs (sometimes called "neutron bombs"), as compared to other types of nuclear weapons, is to enhance radiation casualties while reducing blast and thermal damage to the infrastructure. Five nations were reported to have developed and tested ERWs during this period, but since the termination of the "Cold War" there have been no threats of development, deployment, or use of such weapons. However, if the technology of a quarter of a century ago has been developed, maintained, or even advanced since then, it is conceivable that the grim possibility of future ERW use exists. The type of destruction, initial triage of casualties, distribution of patterns of injury, and medical management of ERWs will be shown to significantly differ from that of fission weapons. Emergency response planners and medical personnel, civilian or military, must be aware of these differences to reduce the horrible consequences of ERW usage and appropriately treat casualties.