Decay without RET

An impoitint aqiect of die distance distribution analysis is Icnowledge of the donor dec dme. Tbis is typicaUy 

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Estimates of batch release concentrations are performed without decay correction since the exact time of the release is not known at the time of the measurement, the release Is in the near future (usually less than six hours from analysis) and failure to incorporate a decay correction maximizes the reported activity for any isotope. Samples are analyzed for a length of time (usually 5,000 seconds) which will ensure the LLD requirements are achieved for each individual sample. This concept must be Incorporated since the YNPS RETS require notification of the NRC, on a yearly basis, of all samples for which the LLD has not been achieved. This concept is tantamount to establishing the last spectral evaluation of the sanple in question as the latest a-priori LLD estimate for the sample under investigation (i.e. the analysis incorporates all of the interferences specific to that sample at that time) (2). 

ABSTRACT Technological advancements in area of sensor-based online maintenance systems have made the possibility of repairing some failed safety support systems of Nuclear Power Plants (NPP) such as electrical supply, I C systems, ventilation systems. However, the possibility of repair during accident situation is yet to be included into PSA level-1. Therefore, this paper presents a scheme of PSA level-1 by implementing an integrated method of Repairable Event Tree (RET) and Repairable Fault Tree (RET) analysis. The Core Damage Frequency (CDF) is calculated from consequence probabilities of the RET. An initiating event of Decay Heat Removal (DHR) systems of ASTRID reactor is analyzed. The proportionate CDFs estimated with repair and without repair have been compared and found that the recoveries can reduce CDF. In sum, this paper attempts to deal with the possibility of repair of some safety systems in PSA and its impacts on CDF of the NPP. 

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