This is a progress report on the activities of the Japanese Nuclear Data Committee (JNDC) for the period of April 1979-March 1981. As special topics, the progress and status of Japanese Evaluated Nuclear Data Library, version 2 (JENDL-2), its integral tests, and the study of decay heat are presented. Activities of the working groups are also reported briefly.

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Using the primary neutron standard in the Electrotechnical Laboratory, the moderating-type neutron Rem-Counter with internal absorber (Studsvik 2202D type) in the Institute for Nuclear Study of the University of Tokyo was evaluated as a secondary standard detector by measuring its energy response function. By combining this energy response function with that obtained at PhysikalischTechnische Bundesanstalt in West Germany, the value of neutron dose equivalent was evaluated based on this secondary standard detector. Furthemore, the same type detectors of the six labolatories in Japan were intercompared in the neutron fields formed by ²⁵²Cf and ²⁴¹Am-Be neutron sources, and the standardized value of neutron dose equivalent was transferred to these detectors. Some discussions have been carried out about problems in transferring and using this value of neutron dose equivalent in order to establish the traceability of neutron standard.

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Coprecipitation of radioactive technetium with hydroxides has been studied for the purpose of the management of the high level waste from the nuclear fuel reprocessing. Pertechnetate ion was reduced to Tc(IV) by ferrous ion (Fe²⁺), and then coprecipitated with Fe(OH)₂ (I) as TcO₂. The pH of nitric acid solution containing TcO_4- was adjusted to 1.0 with NaOH, and TcO₂ was precipitated by reducing coprecipitants i.e. (I), Fe(OH)₂-Zr(OH)₄ (II), Fe(OH)₂-Si(OH)₄ (III) and Fe(OH)₂-Zr(OH)₄-Si(OH)₄ (IV). Pertechnetate ion quantitatively coprecipitates under the conditions: Fe²⁺>3.6×10^-3M; pH=6-12 for (I), pH=4.2-12 for (II), pH=8-12 for (III) and pH=6-12 for (IV). The presence of excess Fe²⁺ prevents the dissolution owing to air-oxidation of TcO₂ coprecipitated. Pertechnetate ion can be also removed from the waste solution by boththe ferrite precipitation method and the iron powder precipitation method.

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