Fuel cladding leak tightness coefficient

After SCALE had been used to calculate the volume activity of Cs inside each fuel assembly, and measurements of the volume activity of Cs outside each fuel assembly had been taken via the sipping in pool, 36 values for the fuel cladding leak tightness coefficient fct were obtained (see Table 4.3). All values were fitted to a distribution function (Figure 4.2) to determine the mean value /r and the standard deviation cr. This means that any fuel assembly with Arpcr = 1-1 x 10 ° 6.5 x 10 or ip, + a), does not have any leakages. Fuel assemblies producer criteria for the released y activity of fission products is 10 Ci/1 (3.7 x 10 Bq/1). 

X 10 ° to 8 X 10 values of the fuel cladding leak-tightness coefficient for a fuel assembly with a suspected leakage, A fct(SL) ... 

The fuel cladding leak-tightness coefficient kpcr is optimally applied during the periodical monitoring of fuel assemblies. Because of the low level of residual y activity in the coolant, six fuel assemblies are monitored at the ISFSF in Jaslovskd Bohunice per year. Two assemblies are used as references, while the other four assemblies are chosen at random. Values of the fuel cladding leak tightness coefficient kpcT were calculated for the two reference assemblies. For both of these assemblies... 

Fuel cladding leak tightness coefficient kpcr... 

Figure 4.3 Limit values for the fuel cladding leak-tightness coefficient fepcr...

It is therefore necessary to adopt an approach that is as conservative as possible. If we compare the volume activity of released fission products around the fuel assembly Aq (measured by the sipping in pool) and the volume activity of fission products inside the whole fuel assembly A (calculated by the SCALE code), we can estimate the condition of the fuel cladding. We therefore introduce the cZ cladding leak tightness coefficient Atfct ... 

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