Advanced Nuclear Power Jan2002

Advanced Nuclear Power - The Magazine of Framatome ANP

"Framatome (ANP) did a good job and we are pleased with the results," said Lew Myers, senior vice president of FirstEnergy Nuclear Operating Company (FENOC) at the Beaver Valley nuclear power plant in the US. He was referring to completion of the first visual inspection of reactor vessel (RV) head control rod drive mechanism (CRDM) nozzle penetrations under the Nuclear Regulatory Commission's (NRC) new Alloy 600 inspection guidelines. Beaver Valley did not find any problems.

Background
In November 2000, discovery of cracked and leaking Alloy-600 vessel head penetration (VHP) nozzles at Oconee Unit 1, followed by a similar situation at Arkansas Nuclear One (ANO) Unit 1 in February 2001, raised concerns about potential safety implications and the prevalence of this type of cracking in the US. This problem was not completely new. The French discovered similar cracking problems in their reactors several years ago but opted to replace the reactor vessel heads to solve the problem. The cracking discovered in France in the early 1990's was primarily nozzle inner surface initiated which differs from the outer surface initiated cracking found at Oconee 1 and ANO-1.

As a result of these and subsequent discoveries of similar cracking, the NRC in August 2001 issued Bulletin 2001-01 requesting that many PWR plants in the US perform a qualified visual inspection of the CRDM nozzles and their welds. Each plant was assigned a susceptibility ranking, based upon the plant operating time (effective full-power years) and the reactor head temperature. Those with the highest susceptibility were requested to perform the inspection before December 31, 2001 or provide the NRC with a basis for concluding that applicable regulatory requirements would continue to be met until the inspection was performed. Those with a lower susceptibility were requested to identify future inspection plans and provide a basis for concluding that applicable regulatory requirements would continue to be met until an inspection was performed. Those of the lowest susceptibility were not requested to perform any additional inspection.

Framatome ANP Beats the Competition in Developing the Technology
Because of Framatome ANP's involvement with Oconee and ANO and because the company invested in developing both inspection and repair technologies, the company had more experience than anyone else when this problem surfaced.

Framatome ANP has Electric Power Research Institute/Material Reliability Program (EPRI/MRP) approved inspection and repair techniques
The technology is applicable to all PWR RV head nozzles for Combustion Engineering (CE), Westinghouse (W), and Babcock & Wilcox (B&W) plants
The technology addresses all known failure modes at once, including both nozzle ID and OD defects plus significantly degraded nozzles with multiple axial and circumferential indications
All repairs are fully qualified to the ASME code, are covered by Framatome ANP's 10CFR50 Appendix B QA program and have been accepted by the NRC.

Framatome ANP's Experience Sought After by Many Plants
The Beaver Valley 1 inspection went so well that Framatome ANP was asked to perform the same inspection on Beaver Valley 2. Surry 1 and 2 also asked Framatome ANP to perform their inspection, based upon the reported success at other plants, as have both Three Mile Island (ultrasonic inspection and repair) and Crystal River. These will be followed by Calvert Cliffs 1 (2002) and 2 (2003).

Benefits of Framatome ANP Approach

Balanced approach uses automation to reduce dose and minimize impact on outage schedules while remaining cost-effective
Design life maximized by remediating the heat-affected zone in the repair area
The technology leaves no crevice. Framatome ANP offers replacement reactor vessel heads, if desired and promises on-time delivery.