Over the last years, the risk of a large scale radiological event has markedly increased, not only due to possible accidents in nuclear facilities but particularly as a result of an enhanced threat of terrorist nuclear or radiological attacks against key facilities or civil targets in major cities. The dosimetric assessment following a nuclear emergency is particularly challenging due to the complicated field of neutrons and photons. Indeed, following the Hiroshima and Nagasaki A bomb explosions, a number of attempts have been undertaken before the neutron component in the dose received by the survivors could be determined with satisfactory precision. Experience shows that a large scale radiological emergency can occur without any advance warning and may target thousands of people. Following such a scenario, there will be an acute need to quickly assess the doses received by the exposed and potentially exposed people. This will allow identifying people who require immediate medical intervention, leading to a reduced medical surge. At the same time, it will be important to provide reliable information about the risks of late effects, most notably cancer. To this end, not only the physical doses must be known, but also the neutron energies, because the biological effectiveness of neutrons is strongly related to the energy.

We have identified three areas of emergency preparedness where increased competence is needed. The corresponding three complementing questions that should be answered are:

1. What is the range of doses, the geographic distribution of radiation injuries and their degree following of a nuclear attack in an urban environment?

2. What dosimetric systems should be employed for in field measurements of neutron and photon equivalent doses after a nuclear attack?

3. Can the gene expression assay be employed as individual and quick retrospective dosimeter for a mixed neutron and gamma irradiation as expected following the detonation of an improvised nuclear device?

The aim of this project is to carry out research aiming at improving dosimetric preparedness and competence in Sweden to cope with a large nuclear emergency. The project is divided into 3 complementary tasks: 1) to simulate the radiation field and map the equivalent dose distribution as a function of distance and shielding from an improvised nuclear device detonated in a urban environment; 2) to carry out a survey of the available dosimetry systems and identify the best suited one for quick in field application following a large nuclear emergency accounting for neutrons and gamma radiation; 3) to validate gene expression as an individual, quick retrospective dosimeter for a mixed neutron and gamma irradiation as expected following the detonation of an improvised nuclear device.

The project is carried out in collaboration between the Medical Radiation Physics and Radiobiology groups of the Stockholm University. Tight contacts will also be set up with European dosimetry and emergency networks EURADOS , NERIS and RENEB.

Due to its particular nature, this project is financially supported by the Swedish Radiation Safety Authority (Strålsäkerhetsmyndigheten).

For more information contact Iuliana Toma-Dasu