Environmental protection: researches in National Institute of Radiological Sciences.

Some studies for radiological protection of the environment have been made at the National Institute of Radiological Sciences (NIRS). Transfer of radionuclides and related elements has been investigated for dose estimation of non-human biota. A parameter database and radionuclide transfer models have been also developed for the Japanese environments.

Effects of acute gamma-irradiation on the aquatic microbial microcosm in comparison with chemicals.

Effects of acute gamma-irradiation were investigated in the aquatic microcosm consisting of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.

Biokinetics of radiocarbon ingested as a food in rats.

Biokinetics of radiocarbon (C) in rats during 14 wk of continuous ingestion of C-wheat was investigated to obtain the dosimetric data on organic C ingested as a food. After the start of continuous ingestion of C-wheat, the concentrations of C in both wet and dry tissues gradually increased and showed a tendency towards a steady-state condition for most of the tissues, except adipose tissue. The steady-state condition was observed at 10 wk in the majority of tissues, but was obtained at 3 wk in liver.

Reconstruction of two victims' posturing based on the induced radioactivities in their bones in the criticality accident in Tokai-Mura, Japan.

On 30 September 1999, three workers were severely exposed to neutrons and gamma rays in a criticality accident that occurred at a uranium conversion facility in Tokai-mura, Ibaraki Prefecture, Japan. Radiochemical analyses of 32P and 45Ca induced by neutrons in bone matrix were carried out after the deaths of two of the victims. It was found that more than several million becquerels of both nuclides had been produced in their body skeletons.

Determination of 32P in urine for early estimation of the neutron exposure level for three victims of the JCO criticality accident.

In the criticality accident which occurred on 30 September 1999 at a uranium conversion facility in Tokai-mura, Japan, three workers were severely exposed to neutron and gamma-ray irradiation. Preliminary estimations of doses from blood properties and 24Na concentration in blood were 16-20, 6-10 and 1-4 gamma-ray gray-equivalent (gammaGyEq) respectively for the three workers. For apparent dose estimation, neutron-induced radionuclides in biological materials such as blood, hair and urine were measured.