Many types of survey instruments for measuring exposure dose from neutrons and methods for assessing the dose equivalent rate have been developed in many countries. In JAERI, extensive efforts have been made for establishing the method to assess neutron dose equivalent. The main objectives of this report are to introduce the principle of measuring neutron dose equivalent rate based on an orthonormal expansion method and to describe its application for the operational health physics in JAERI. This report also describes an experience with the various types of neutron survey instruments which have been employed for the radiation protection in JAERI since 1958.
The leak of radionuclides from a disposed container depends on some rate processes such as the dissolution of the surface of the solidified waste and the diffusion in the solidified body and the wall of the container. Concerning the diffusion processes, several methods to determine the effective diffusion coefficient were reviewed and newly developed theoretically in the former paper. Based on the one of them, effective diffusion coefficient of 3H2O, NH4Cl in the porous media such as cement paste, mortar, gel and the packed bed of resin-balls were measured and compared with the theory in this paper. And then the coefficients were explained in connection with the structure of these porous media with the concept of tortuosity factor.
The fresh shrimps (Erythropenaous akayebi var. sp.) were blenched three minutes in boiling 2% NaCl solution and then were sealed in polyethylene cells. The sudden boiled shrimps were irradiated by cobalt-60 and were preserved in the storage space of a refrigerator (3-5°C). The storage life of 0.6 megarad irradiated shrimps was extended to about 7 weeks, compared with 3 weeks for the unirradiated samples held at the same temperature.