Preliminary evaluation of effluent radioactivity monitoring systems for BWR plants

The need for upgrading the effluent monitoring systems at commercial nuclear power plants was recognized following the TMI-2 accident in 1979 (NUREG-0737, ''Clarification of TMI Action Plan Requirements''). Improvements have been made to these systems since then, but not all problems dealing with the measurement of radioactive releases during severe accident scenarios have been addressed. This report discusses some of the generic issues associated with the transport and subsequent sampling of noble gases, particulates, and iodine species that utilities must consider to ensure accurate reporting during severe accident conditions. In light of these generic concerns, 'specific postaccident upgrade is discussed, major measurement uncertainties are identified, and recommendations are made. The focus of these recommendations is the transport behavior of iodine; sample-line losses may result in an order of magnitude error for near-real-time measurements. Finally, a recommendation for a laboratory sample-line test program is made. The laboratory effort would better define the uncertainty of the commercial measurements and also provide data for the improvement of line-loss algorithms. 16 refs