Precise Evaluation of Corrosion Environments of Structural Materials under Complex Water Flow Condition, (II)

In order to clarify the corrosion environment of nuclear reactor structure material precisely, the water radiolysis evaluation considering a flow of reactor water was performed. This study focused on the downcomer region of a Boiling Water Reactor (BWR). Radiation intensity of the region is high and water radiolysis reaction occurs well. Therefore, the region is recognized as important for recombination of oxygen, hydrogen peroxide and hydrogen back to water under hydrogen water chemistry (HWC) condition. Precise evaluation of water chemistry in the region with consideration of water flow, however, has not been performed. In the downcomer region water flow is very complicated because the jet pumps are close together and water flows out to the recirculation system through only two nozzles. A new water radiolysis model was developed which can simulate water radiolysis under the three-dimensional water flow condition. The calculation was performed using the result of water flow analysis obtained by the computer code “a-Flow.” The water chemistry near a shroud wall and the reactor pressure vessel (RPV) wall differed greatly, and especially so under HWC condition. Also, the detailed distribution of the electrochemical corrosion potential (ECP) of structural materials was clarified by using the water chemistry analysis result.

[1]  H. Christensen,et al.  Reactions of Hydroxyl Radicals with Hydrogen Peroxide at Ambient and Elevated Temperatures , 1982 .

[2]  R. L. Cowan.  Experience with hydrogen water chemistry in boiling water reactors , 1986 .

[3]  Toshihisa Tsukiyama,et al.  BENCHMARK VALIDATION OF TORT CODE USING KKM MEASUREMENT AND ITS APPLICATION TO 800 MWE BWR , 2003 .

[4]  G. R. Sunaryo,et al.  Radiolysis of water at elevated temperatures—II. Irradiation with γ-rays and fast neutrons up to 250°C , 1995 .

[5]  A. Motta,et al.  Modeling Water Chemistry, Electrochemical Corrosion Potential, and Crack Growth Rate in the Boiling Water Reactor Heat Transport Circuits—I: The DAMAGE-PREDICTOR Algorithm , 1995 .

[6]  E. Ibe,et al.  Radiolytic aspects in boiling water reactor primary systems: results from numerical simulations and statistical regression analyses , 1985 .

[7]  R. L. Cowan,et al.  Paper 13. Experience with hydrogen water chemistry in boiling water reactors , 1986 .

[8]  W. Burns,et al.  Radiation chemistry of high-temperature (300–410 °C) water. Part 1.—Reducing products from gamma radiolysis , 1981 .

[9]  C. P. Ruiz.  Model calculation of water radiolysis and electrochemical potentials in BWR primary coolant II , 1992 .

[10]  A. Elliot,et al.  Temperature dependence of g values for H2O and D2O irradiated with low linear energy transfer radiation , 1993 .

[11]  H. C. Christensen,et al.  Reaction of hydroxyl radicals with hydrogen at elevated temperatures. Determination of the activation energy , 1983 .

[12]  N. Ichikawa,et al.  Precise Evaluation of Corrosion Environments of Structural Materials under Complex Water Flow Condition, (I) , 2003 .

[13]  J. M. Watt.  Numerical Initial Value Problems in Ordinary Differential Equations , 1972 .

[14]  F. R. Smith,et al.  Decomposition of hydrogen peroxide in aqueous solutions at elevated temperatures , 1991 .