Radiation and Video Survey of Water Cleanup and Ventilation System of RFT Reactor

Abstract

The specialists of NRC "Kurchatov Institute" have conducted the dismantling of the MR multiloop research reactor and RFT reactor. The technical start-up of the 20 MW capacity experimental graphite water cooling reactor (RFT) started in 1952. The reactor was shut down 10 years after the working period. The fuel was removed and the reactor was partially dismantled. The ventilation system and water cleanup system of the RFT reactor were located in a separate building. The upper part of the reactor vent stack was dismantled in the early 60's. The water cleanup system, which consists of 6 stainless steel tanks (4 -Ø1.5m, h=5m; 2 -Ø3m, h=5m) located around the base reactor vent stack, was mothballed. To plan the dismantling work, a radiation and video survey of the water cleanup system and the reactor vent stack was carried out. For this purpose, holes were drilled in the upper ceiling of premises with the water cleanup system and at the top of vent stack. Through these holes video recording and measurement of the exposure dose rate distribution were carried out. The measurement of the exposure dose rate distribution along the height of vent stack was also carried out. Based on the result of these surveys, the measurements of distribution of activity from radioactive waste along the height of the tank were carried out. The collimated spectrometric system on the basis of a semiconductor detector CdZnTe (volume of a crystal of 60mm 3 ) was used. The measurements showed that the distribution of activity from radioactive waste along the height of the tank was non uniform. To measure the distribution of the contamination of the inner surface vent stack we used the spectrometric system with semiconductor detector CdZnTe (volume of a crystal of 500mm 3 ) with circular collimator. The results of measurements are presented and discussed. The results of the survey will be used for planning the dismantling work.