Probabilistic Safety Criteria and Core Degradation Mechanism
Volume 6, Number 1, January 2010 - Paper 1 - pp. 3-18
ALOK MISHRA1, MAHESH D. PANDEY2, and MICHAEL KNOCHENHAUER31ScandPower Risk Management Inc., 1331 Lamar, 4 Houston Centre, Suite- 1270, Houston, TX-77010, USA
2Institute for Risk Research, University of Waterloo, Ontario, N2L 3G1, Canad
3Relcon ScandPower AB, Englundavägen 13, P.O. Box 1288, SE-172 25 Sundbyberg, Stockholm, Sweden
(Received on May 30, 2008, revised on June 11, 2009)
As nuclear power plant age, degradation of structure, systems and components can be expected to occur. The understanding of the effect of the age related degradation is important to ensure safe operation of the nuclear power plant. The pressure tubes in CANDU reactors are critical components and its failure has consequences of concern. These cold worked Zr-2.5% Nb pressure tubes may degrade due to ageing mechanisms like creep and delayed hydride cracking. It is important to periodically monitor the serviceability these tubes over the service life. This paper discusses the estimation of the allowable conditional failure probability of the pressure tubes for meeting the risk informed regulation criteria of the US-NRC regulatory guide RG. 1.174.
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