Reactor and spent fuel storage pool

A description of the fuel basin is given to help in drawing conclusions from the results. The basin was built during the last reconstruction of the reactor, i.e. between 1986 and 1992. The reconstructed reactor went critical for the first time in December 1992. Regular operations started in November 1993, and the basin has been in use since then, i.e. the first spent fuel elements were removed from the reactor core and immediately put into the basin in 1994. The fuel elements are normally used up to a relatively high burnup of 60%. They are exposed to temperatures of up to 60°C in the reactor. The temperature of the storage pool is about 20°C, with very limited seasonal variations. 

The coupon racks were positioned about 2 m above the fuel elements and 2 m below the water surface. The y radiation dose was measured only occasionally. The dose rates at the upper ends of the fuel elements were last measured on 2000-02-23. They were 10, 16 and 22.8 Sv/h at three different positions just above the relatively fresh fuel elements. The dose rate near the rack could not be measured with low sensitivity devices. An upper limit was nevertheless determined, and the dose rate did not exceed a few millisieverts per hour. The pool water is continuously recirculated by pumps. There are no stagnant areas within the pool. Water parameters such as pH, conductivity and radioactivity were measured regularly, some on a monthly basis and some more frequently. Summaries of these measurements are given in Table 8.1. Chemical analyses were carried out approximately every three months. The results of the chemical analyses are given in Table 8.2. 

On the basis of the results presented in Tables 8.1 and 8.2, it can be concluded that the quahty of the water in the storage basin was good during the entire period of the CRP investigations, i.e. from May 1997 to May 2000. 

Date Total p activity (Bq/mL) Y activity (Bq/mL) Co Y activity (Bq/mL) Electrical conductivity (pS/cm) pH 

TABLE 8.2. RESULTS OF QUARTERLY WATER ANALYSES (CONCENTRATIONS IN mg/L) 

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