Taiwanese regulatory approval of EPRI guideline document BWRVIP-75-A enabled Kuosheng Unit 2 to reduce inspections by more than 50% during its 2010 outage.

A growing number of non-U.S. nuclear utilities are taking advantage of the technical basis in BWRVIP-75-A to extend inspection frequencies and reduce the sample population for certain weld types. Taiwan Power Company received approval from its regulator earlier this year to use this EPRI guidance and was able to reduce piping inspections by more than 50% at its Kuosheng boiling water reactor plant during a 2010 outage. The inspection reduction resulted in significant savings in inspection staff resources, radiation dosage and inspection equipment setup, facilitating smooth outage completion and minimized outage duration.

Kuosheng Nuclear Power Plant

EPRI developed BWRVIP-75-A in response to concerns raised by the U.S. Nuclear Regulatory Commission (NRC) in the 1980s regarding intergranular stress corrosion cracking in small-bore and large-bore piping. In a Generic Letter issued in 1988 (GL 88-01), NRC defined its positions on material categorization and associated inspections, mitigation options, repair methods, and flaw evaluation. BWRVIP-75-A provides the technical basis to demonstrate that intergranular stress corrosion cracking is adequately managed and that existing programs exceed what is needed to manage future problems. The guidance also justifies revisions to the weld examination frequencies defined in GL 88-01.

NRC approval of BWRVIP-75-A allowed inspection frequencies to be extended and the required sample population for weld inspections to be reduced. Additional inspection reductions were approved for plants with effective hydrogen water chemistry. For example, consider non-resistant materials that have been stress improved. Within the first two years of operation, GL 88-01 requires inspections of at least 50% of the welds every 10 years and at least 25% of the welds in the first six years. With BWRVIP-75-A, the inspection frequency is relaxed to 25% every 10 years with normal water chemistry and 10% every 10 years for hydrogen water chemistry.

Many U.S. utilities have taken advantage of BWRVIP-75-A to reduce the total examination population and to choose lower dose piping welds as part of their population. This has resulted in a significant cost savings in exam costs and dose.

The practice is now spreading outside the United States, as evidenced by Taiwan Power Company’s success in gaining regulatory approval to apply the results and recommendations in BWRVIP-75-A. This approval enabled TaiPower to reduce piping weldment inspections at Kuosheng 2 from 40 to 14 during its 20th operating cycle outage, completed in April 2010. For their 21st operating cycle outage, the Kuosheng units received approval to reduce inspections from 65 to 20 for Kuosheng 1 and from 47 to 19 for Kuosheng 2.

For more information, contact Randy Stark at 650-855-2122 or rstark@epri.com.