Continued from the reports (III), (IV) and (V), variations of iodine concentrations ¹³¹I, ¹³³I and ¹³⁵I in the primary coolant during the load following operation of reactor are analyzed for surface contamination of UO₂, existing cladding defects and happening of new defects.
These analyses show that various defects can be grasped at each condition and reactor operators are able to have the chance to detect the most unfavorable occurrence.

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This is a progress report on the activities of the Japanese Nuclear Data Committee (JNDC) for the period of April 1981-March 1983. As special topics, the completion of Japanese Evaluated Nuclear Data Library, version 2 (JENDL-2), its sensitivity analysis and integral tests, and the Present status of version 3 library (JENDL-3) are presented. Evaluation of gamma-ray.production cross section and nuclear data requirements in new fields are also reported toplcally.

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Fukushima Prefecture is expected to have three nuclear power stations along the Pacific coast. One of them has already been in operation, the other two are now under construction or planning. The original plan includes 14 reactors (ca. 13, 000MWh) in all.
Thus, in 1974, Environmental Radioactivity Research Institute of Fukushima Prefecture was established in Okuma town by the local government. The activities of this facility are asfollows:
(1) Monitoring of environmental radioactivities around the nuclear power stations.
(2) Measurement of ndioactive fallout. (This work is entrusted by the Science and Tochnology Agency.)
(3) Information of the nuclear energy.

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A mathematical model was proposed to estimate transportation and distribution of ⁹⁰Sr in fallout at an aerated zone. The distribution of ⁹⁰Sr in the aerated zone was estimated at two locations, Ibaraki and Yamagata, by using enviromental parameters such as fallout, precipitation, evaporation, distribution factor, diffusivity and field capacity, and the calculated ⁹⁰Sr profiles were compared with observed profiles to examine the validity of the model. Sensitivity analysis and robustness analysis were applied for evaluating variational characteristics of the calculated profiles.
Some valuable resu1ts were obtained in this study under the limits considered. These are as follows: (1)The mathematical model would be applicable reasonably on the practical estimation of transportation and distribution of ⁹⁰Sr in fallout at aerated zone; (2) Calculated 90Sr profile agreed satisfactorily with the observed one under the assumption of ⁹⁰Sr in fallout at composition of more sorptive fraction and less sorptive; and (3) Distribution factor, diffusivity, precipitation and more sorptive ⁹⁰Sr fraction were more sensitive to the calculated ⁹⁰Sr profile than the another environmental parameters involved in the model.

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