Paper 90. Steam cycle water chemistry improvements with on-line ion chromatography

Hydrogen and hydrazine co-injection into a boiling water reactor was considered as a new mitigation method of stress corrosion cracking. To confirm decrease of electrochemical corrosion potential by the reduction of oxygen and hydrogen peroxide in bulk water using reducing agent, reaction of hydrazine with oxygen or hydrogen peroxide under simulated downcomer conditions (temperature: 280 C, duration: 4.2 s and gamma-irradiation) was examined. All the oxygen was consumed above the equivalent concentration for the reaction with oxygen within this short time (gammairradiation case) and almost all the hydrogen peroxide was consumed. Reaction rates were accelerated more than five times by gamma-irradiation in each case. Reaction rates with oxygen were compared with other reducing agents such as hydrogen, methanol and ammonia. From the viewpoint of reaction rate and formation of by-product, hydrazine was the most suitable agent. Using a simple model based on the experimental results, water chemistry for the bottom region was calculated for the case of no hydrogen injection and for the case of 0.2 mmolÁkg À1 hydrogen injection into feed water. For both cases, concentrations of dissolved oxygen and hydrogen peroxide were estimated to decrease enough to mitigate SCC, with concentration of ammonia suppressed below the management criteria for reactor water chemistry.

Section: Resultsmentioning

confidence: 99%

“…However injection of an appropriate amount of hydrogen suppresses the nitrite formation. 10,18) Nitrite may affect SCC susceptibility and/or corrosion of fuel cladding. 9) The final reason is to suppress the production of oxygen and hydrogen peroxide by water radiolysis.…”

Section: Concept Of the New Mitigation Methodsmentioning

confidence: 99%

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (II)

Ishida

Wada

Tachibana

et al. 2006

“…The relation in Fig. 5, therefore, can be regarded as temperature dependence of reaction ( 6 ). The activation energy of 34.4 k]/mol is applied to reaction ( 6 ).…”

Section: G-values and Rate Constantsmentioning

confidence: 99%

Behavior of Nitrogen Compounds in Radiation Field and Nuclear Reactor Systems

Ibe

Karasawa

Nagase

et al. 1989

Formation of nitrogen compounds in N,-H 2 0 systems under radiation was studied. A reaction scheme with 24 species and 73 reactions was proposed. Two trigger reactions for nitrogen atom generation: N, ~ 2N (o-value of 1.6 pmol per 1 kJ absorbed energy in N 2 molecules), and N2+H20*-NH 2 +NO (k=3.0 x 10 9 s-at 298 K with activation energy of 34.4 kJ/mol) were included. Calculated results with the reaction scheme agreed within an error factor of two with ammonium formation rates from an aqueous solution with dissolved nitrogen and hydrogen gasses under r-irradiation at temperatures of 288-473 K. The reaction scheme was also verified with BWR plant observations on nitric acid formation from in-leaked air under hydrogen water chemistry and ammonium injection tests.

Radiation Chemistry of Radioactive Nitrogen Species in BWR Reactor Cores

Ibe

Karasawa

Uchida

1991

Chemical behavior of nitrogen species in intense radiation fields was studied. Simulation models and a N/H/0 reaction scheme were developed and verified with a series of experiments.The following results and suggestions were obtained:(1) Ammonium formation rates in water pressurized with H2 and N2 gases at temperatures of 288~473 K were measured and numerically simulated with the reaction scheme within an error factor of 2. (2) Chemical behaviors of radioactive nitrogen (I'N and 'BN) were also theoretically analyzed.Computer simulations demonstrated that the major species of radioactive nitrogen released to the main steam was nitric oxide (NO). This prediction was partly supported by a 13 N analysis in the main steam of an actual BWR: About 85% of the 13 N was found to be in anionic species whose precursor was supposed to be NO.