The argument for low hydrogen and lithium operation in PWR primary circuits
- Pennsylvania State Univ., University Park, PA (United States). Center for Advanced Materials
The use of high hydrogen levels in the primary circuit of a pressurized water reactor (PWR) is believed to be a possible cause of cracking of Alloy 600 steam generator tubes and other components fabricated from a variety of stainless steels and nickel-base alloys. Cracking occurs due to the electrochemical potential (ECP) being in the region for hydrogen-induced cracking, or in a region for stress corrosion cracking. In order to estimate the corrosion potential of these alloys in PWR primary environments, a series of algorithms has been developed. These algorithms have been used to determine the pH of aqueous LiOH + B(OH){sub 3} solutions, to calculate the concentration of radiolysis products produced in the core due to the neutron and {gamma}-photon fluxes, and to estimate the ECP under simulated operating conditions. From these calculations, the ECP for various hydrogen concentrations, lithium to boron ratios (as specified by a given pH), and dose rates were evaluated. The authors show that under the prescribed operating conditions for PWRs ([H{sub 2}] = 25--50 cc/kg), the corrosion potential is more negative than the critical potential ({minus}0.8 V{sub SHE}) for the onset of hydrogen induced intergranular cracking in Alloy 600. However, by lowering the hydrogen concentration to less than 4 cc/kg at a pH of 7.5 and to less than 10 cc/kg at a pH of 7.0, the authors predict that it would be possible to protect Alloy 600 from fracture.
- OSTI ID:
- 203747
- Report Number(s):
- CONF-950816--; ISBN 1-877914-95-9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
BORON HYDROXIDES
CRACK PROPAGATION
INCONEL 600
LITHIUM HYDROXIDES
MATHEMATICAL MODELS
PH VALUE
PRIMARY COOLANT CIRCUITS
PWR TYPE REACTORS
RADIOLYSIS
STAINLESS STEEL-304
STEAM GENERATORS
STRESS CORROSION
THEORETICAL DATA
TUBES
WATER CHEMISTRY