PWR Archives

Tag Archive for: PWR

News & Views, Volume 46 | Baffle-Former Bolt Management: Cost/Benefit Studies

July 1, 2019/in Chris Lohse, News and Views, Nuclear Energy, Tim Griesbach/by Structural Integrity

By: Tim Griesbach and

For the past several years baffle-former bolt (BFB) cracking in pressurized water reactors has become a significant concern for of PWR plants. In 2016, three similar Westinghouse designed plants (Indian Point 2, Salem 1, and D. C. Cook Unit 2) experienced significant numbers of cracked BFBs, attributed to irradiation-assisted stress corrosion cracking (IASCC). These plants had common characteristics that included the 4-loop plant design, downflow configuration, and Type 347 stainless steel bolting material. BFB cracking is not an entirely new phenomenon as it was initially detected in the French PWR fleet in the 1990s. However, the extent of cracking found in some of the US plants has greatly exceeded prior cracking. Extensive industry programs have identified and categorized by tier group the most susceptible plants, and the EPRI Materials Research Program (MRP) has published guidance regarding baffle-former bolt UT inspections for PWR plants for detection of degraded and cracked bolts in the baffle-former assembly (MRP-2017-009).

News & Views, Volume 45 | Interval Relief from RPV Threads in Flange Examination Requirements

January 1, 2019/in News and Views, Nuclear Asset Integrity, Nuclear Energy, Reactor, Scott Chesworth/by Structural Integrity

By: Scott Chesworth

ASME Code Section XI requires that the RPV Threads in Flange component (Category B-G-1, Item Number B6.40, see Figure 1) be inspected each inspection Interval using volumetric examination. However, there is general agreement that the inspection does not contribute to the overall safety of the RPV. Industry experience indicates that these examinations have not been identifying service-induced degradation and that they have negative impacts on worker exposure, personnel safety, and outage critical path time. Savings from the elimination of this inspection can be applied to other more meaningful inspections of other more risk-significant plant components.

EPRI Report 3002007626 (March 2016) provides the basis for eliminating the RPV Threads in Flange examination requirement. This report includes the results of an industry survey in which 168 units provided the status of their RPV Threads in Flange examination, as well as insight into the impacts of conducting these examinations.