Noble Metals Sampling Experience

摘要

In the United States, it is common for Boiling Water Reactors (BWRs) to use noble metals chemistry in conjunction with Hydrogen Water Chemistry (HWC) for intergranular stress corrosion cracking (IGSCC) mitigation. These noble metals are now commonly applied using the On-Line Noble Chem (OLNC) method. The goal is to maintain a noble metals concentration of > 0.10 μg/cm~2 on the primary system components. One method of determining when to re-apply or to provide evidence that the noble metals concentration is of sufficient magnitude is to remove coupons from the mitigation monitoring system/durability monitor, which is in the reactor water cleanup loop, and strip the corrosion products from the coupons to determine the noble metals concentrations. Another option is to collect samples from artifacts from the reactor or from the reactor core shroud itself. This paper will provide a summary of experience sampling reactor artifacts and direct core shroud sampling in the U.S.