S. Uchida et al., APPLICATION OF HYDROGEN WATER CHEMISTRY TO MODERATE CORROSIVE CIRCUMSTANCES AROUND THE REACTOR PRESSURE-VESSEL BOTTOM OF BOILING WATER-REACTORS, Nuclear technology, 110(2), 1995, pp. 250-257
Many efforts to preserve the structural integrity of major piping, com
ponents, and structures in a boiling water reactor (BWR) primary cooli
ng system have been directed toward avoiding intergranular stress corr
osion cracking (IGSCC). Application of hydrogen water chemistry (HWC)
to moderate corrosive circumstances is a promising approach to preserv
e the structural integrity during extended lifetimes of BWRs. The bene
fits of HWC application are (a) avoiding the occurrence of IGSCC on st
ructural materials around the bottom of the reactor pressure vessel (R
PV) and (b) moderating the crack growth rate, even if microcracks are
present on the structural materials. Several disadvantages caused by H
WC (e.g., turbine dose rate increase, Co-60 radioactivity buildup, and
effects on fuel cladding) are evaluated to develop suitable counterme
asures prior to HWC application. The advantages and disadvantages of H
WC are quantitatively evaluated based on both BWR plant data and labor
atory data shown in unclassified publications. Their trade-offs are di
scussed, and suitable applications of HWC are described. It is conclud
ed that an optimal amount of hydrogen injected into the feedwater can
moderate corrosive circumstances, in the region to be preserved, witho
ut serious disadvantages. The conclusions have been drawn by combining
experimental and theoretical results. Experiments in BWR plants - e.g
., direct measurements of electrochemical corrosion potential and crac
k growth rate at the RPV bottom - are planned that would collect data
to support the theoretical considerations.