Nuclear Executive Update   
An EPRI Progress Report, January 2011
TECHNICAL HIGHLIGHTS
Surveillance Campaigns Indicate No Negative Fuel Performance Impacts from Noble Metal Injection

Based on positive field experience, in terms of both stress corrosion cracking mitigation and fuel performance, the industry is transitioning to on-line noble metal chemical addition.

The use of noble metal injection to mitigate intergranular stress corrosion cracking (IGSCC) of stainless steel reactor internals in boiling water reactors has grown significantly over the past 15 years, but there have been lingering concerns about potential impacts on nuclear fuel performance. EPRI has conducted surveillance campaigns at several plants to evaluate the potential impacts of noble metals on fuel performance.

The first generation of this technology, known as classic Noble Metal Chemical Application (NMCA), involves the injection of platinum and rhodium into the feedwater at end-of-cycle and is applied every 4 to 4.5 years. The second generation of noble metal technology, known as On-Line NobleChem (OLNC), involves platinum injection into the feedwater over 10-14 days each year while the unit is at greater than 85% power. OLNC provides greater flexibility to plant operators.

One of the key considerations in the development and implementation of both the NMCA and OLNC technologies was the possible impact on fuel performance. EPRI’s Fuel Reliability Program performed multi-cycle poolside and hot cell fuel examinations in 1996 at Duane Arnold, which was the first U.S. reactor to apply NMCA. Results provided confidence to expand NMCA use across the BWR fleet. Numerous fuel inspections have been performed across the BWR fleet following the Duane Arnold demonstration as part of the technology qualification process, the majority of which indicate that NMCA has no direct adverse effect on fuel performance. Two early instances of higher-than-normal cladding corrosion have been observed, but these isolated cases have not been conclusively attributed to the use of NMCA. Nevertheless, all plants implemented conservative process controls, including that new fuel must be operated for 90 days prior to an application.

In 2005, a European BWR became the first plant to apply OLNC. Applications have been performed annually in each fuel cycle for a total of six to date. EPRI-funded fuel surveillance campaigns at this plant showed no adverse effects of OLNC on fuel performance. Similar fuel surveillance campaigns at Nine Mile Point Units 1 and 2 and other plants demonstrated no negative impacts, even with different operating conditions such as fuel duty, cycle length and water chemistry.

Based on the positive experience thus far, both from an IGSCC mitigation and a fuel performance perspective, the industry is rapidly transitioning from classic NMCA to OLNC (see figure). Currently, 13 BWR units have implemented OLNC and many more plan to transition to OLNC in the next few years. EPRI will continue to monitor fuel performance to increase confidence that this technology has no negative impact on fuel performance.

For more information, contact Aylin Kucuk at 650.855.2124 or akucuk@epri.com.