The impact of radiolytic yield on the calculated ECP in PWR primary coolant circuits

A Critical Review of Radiolysis Issues in Water-Cooled Fission and Fusion Reactors: Part I, Assessment of Radiolysis Models

“…Here, we discuss only those aspects of the subject that are relevant to reactor (fission and fusion) heat transport systems (HTS). The radiolysis of water in water-cooled nuclear (fission) reactor (WCNR) primary heat transport circuits has long been recognized as a potential source of corrosive, oxidizing species, such as O 2 , H 2 O 2 , and OH, and for this reason hydrogen is added to PWR primary coolant circuits [168,205,248,249,252,253,[265][266][267][268][269] and, in more recent years, to BWR coolant circuits. The hydrogen addition is made to suppress the radiolytic generation of oxidizing species and/or to displace the corrosion potential of structural components in the coolant circuits in the negative direction.…”

“…In the authors' opinion, the radiolysis work published to date on fusion reactors is in the same stage of development as was that for fission reactor work in the mid-1990s. Thus, the authors found only one reliable attempt to calculate the ECP [253] and no attempts to calculate the rates of growth of stress corrosion cracks, something that was achieved in the mid-1990s in modeling fission reactors 255,[281][282][283][284][285][286][287][288][289], although the SCC of stainless steels had been addressed experimentally [23]. Kritsky et al [27] report a study of radiolysis in the Divertor PHTS (which is part of today's IBED PHTS) assuming the water chemistry parameters that existed at that time (summarized in Table 13).…”

“…Thus, H 2 O 2 is a much more powerful oxidizing agent than is O 2 ; that is, it possesses a much more positive standard reduction potential of 1.77 V she vs. 1.23 V she , respectively, and hence has a much greater impact on the ECP than does the addition of oxygen for equivalent molar concentrations. Furthermore, experiments have shown that the addition of small amounts of oxidizing agents to hydrogenated water can result in a significant shift of the ECP in the positive direction [253]. Clearly, the most important species in affecting this shift is H 2 O 2 , and the extent to which any species contributes to the shift in the ECP is roughly proportional to the concentration, as determined by the contribution of the partial current density the reduction or oxidation of that species to the total partial current flowing at the interface under open circuit conditions.…”

Primary yields and reaction sets with corresponding rate constants for computer simulation of water radiolysis at elevated temperature

“…Likewise, it is interesting to evaluate the reliability of several reaction sets and corresponding rate constants, as well as other initial parameters, for the simulation model at high temperatures. Unlike at ambient temperatures, the accumulated experimental data at elevated temperatures are not well established [25][26][27][28][29][30]. During the past few decades, several groups have attempted to evaluate the chemical reactions and corresponding rate constants based on the accumulated experimental hightemperature data together with the extrapolation and estimation of activation energies and theoretical evaluation [31][32][33][34][35][36][37][38].…”

Electrochemical behaviour of 316L stainless steel exposed to representative chemistry in pressurised water reactors under proton radiation

“…However, it has been pointed out that zero dissolved oxygen does not necessarily mean the ECP is less than À230 mV (SHE) [21]. Concerning Irradiated Assisted Stress Corrosion Cracking (IASCC), Macdonald et al [22] and Urquidi-Macdonald et al [23] have shown that with the increasing concentration of H 2 , ECP will be shifted to a more negative value: even with low concentration of H 2 , the ECP is lower than À230 mV (SHE) in PWR primary conditions. On the other hand, according to Ishigure et al [24], ECP can be increased importantly in BWR hydrogen water chemistry conditions depending on factors as dose rate, flow rate and water chemistry.…”