Water chemistry in PWRs

Water chemistry and corrosion in pressurized water reactors (PWRs)

Figure 1 - Variation of pH with temperature

Figure 2 - Potential diagram – pH of iron at 300°C (after [1])

Figure 3 - Solubility of nickel ferrite at 300 °C as a function of pH [4].

Figure 4 - Trends in average annual collective dose per unit (reactor) in various countries [9].

Figure 5 - Estimation of oxide layer thickness (in nm) on E110 fuel alloy after 140 h exposure to primary circuit chemistry, as a function of Li content expressed in mg/kg [10].

Figure 6 - Intergranular corrosion and stress corrosion cracking of an Alloy 600 tube extracted from a PWR plant steam generator after 100,000 h of operation (EDF-GDF photo)

Figure 7 - Stress corrosion cracking zones in steam generators

Figure 8 - Influence of nickel content on the susceptibility of Fe-17%Cr-Ni alloys to high-temperature stress corrosion cracking in pure or chloridized water [12].

Figure 9 - Detrimental influence of temperature and hydrogen content on crack propagation (CSC) on the primary side [15] and [16].

Figure 10 - CSC sensitivity of various alloys as a function of sodium hydroxide content [17]

Figure 11 - Beneficial effect of zinc on the initiation of primary-side SCC cracking in Alloy 600 MA GV tubes [18].

Figure 12 - Typical pollutant concentration at various points on the secondary side of a steam generator [19].

Figure 13 - Chemical transformations linked to the thermal decomposition of condenser cooling water, with the generation of alkaline (river water) or acidic (sea water) media.

Figure 14 - Tube from Fessenheim (EDF micrograph) affected by intergranular corrosion on the secondary side

Figure 15 - Corrosion-erosion pipe rupture at the Mihama power plant (Japan) in 2004 (source: Kansai Electric Power Company (KEPCO))

Figure 16 - Influence of chromium content on corrosion-erosion rate

Figure 17 - Influence of oxygen content on corrosion-erosion rate

Figure 18 - Chemical specification for lithium in the primary circuit, depending on the boron content

Figure 19 - Chemical formulas for conditioning reagents

Figure 20 - Effectiveness of adding dispersant (polyacrylic acid /PAA) to feedwater to remove oxides when steam generators are purged [24].

Figure 21 - Power operating zones (P &gt; 25% PN) specified at steam generator blowdown for sodium and cationic conductivity

Figure 22 - Detrimental effect of a condensate treatment plant on the quantity of corrosion products [25].