BWR Plants with Low Shutdown Radiation Level

Reactions of Ni and Co ions with amorphous iron (ill) hydroxide, which was synthesized by electrolysis of iron electrode, have been studied in high temperature water using an in situ method of a modified magnetic balance and using a reaction model. Formation of NiFe,O. and CoFe 2 0 4 from the amorphous iron (ill) hydroxide were explained by the reaction model incorporating two phenomena, i.e. dehydration of the iron(ill) hydroxide and diffusions of Ni and Co ions into it. The dehydration rate followed Avrami's equation. Apparent activation energy of the dehydration was 4.39 x 10 4 J/mol for the amorphous iron (ill) hydroxide used in the experiments. The diffusions of Ni and Co ions into the particle were evaluated from the diffusion equation for spherical coordinates. The diffusion coefficient of Ni ion into the amorphous iron(ill) hydroxide was much higher than that of Co ion, while its apparent activation energy was about 5.5 x 10 4 J/mol, a value close to that of Co ion. However, the diffusion rate of Co ion into a-Fe,O, was faster than that of Ni ion. Calculated values from the reaction model showed good agreement with experimental values.

Section: Ll Reaction Modelmentioning

confidence: 99%

Reaction Rates of Amorphous Iron Hydroxide with Nickel and Cobalt Ions in High Temperature Water

Nishino¹,

Sawa²,

Ohsumi³

et al. 1989

“…These impurities in the feedwater are deposited on the fuel rod surface and radioactivated through neutron irradiation. Deposit dissolution rate is one of the important factors determining radioactivity in the reactor water< 4 Therefore, in recent crudsuppressed BWR plants, the Fe crud concentration in the feedwater is controlled at the Ni concentration, within low concentrations, in order to form insoluble NiFe 2 0 4 as the deposit<'>-<'>. It is important to study the deposition of Fe crud and metallic ions on the fuel rod and those reactions in order to establish effective countermeasures for minimizing radioactivity levels in the reactor water.…”

Section: Introductionmentioning

confidence: 99%

Deposition of Nickel and Cobalt Ions with Iron Crud on Heated Stainless Steel Surface under Nucleate Boiling Conditions

Nishino

Asakura

Sawa

et al. 1991

Self Cite

Deposition behaviors of Ni(II) and Co(II) ions on a heated surface using simulated Fe crud which was mainly composed of amorphous Fe(ill) hydroxide have been studied under nucleate boiling conditions at 553K and 70atm. The deposition process of Ni(II) and Co(II) ions is divided into two stages. The first stage is the deposition of hydroxide precipitate on the heated surface by microlayer evaporation and drying out in the nucleate boiling bubble. The second is settlement by conversion of hydroxide into oxides such as NiO, NiFe,o., CoO and CoFe 2 0 4 • The effective deposition coefficients of Ni (II) and Co (II) ions, without supplying Fe crud, are smaller than that of a-Fe,O, because of the solubility of those hydroxides at a low concentration condition. Their effective deposition coefficients increase with the simulated Fe crud concentration in feedwater and saturate at a value of 0.3 which is calculated theoretically, because the Ni and Co hydroxides react with the simulated Fe crud to produce insoluble NiFe 2 0 4 and CoFe,O. on the heated surface. The reaction of Ni deposit with a-Fe,0 3 does not proceed, but NiO is produced. The reaction rate of Ni deposit with the simulated Fe crud on the heated surface is higher than that of Co deposit.

Water chemistry technology – one of the key technologies for safe and reliable nuclear power plant operation

Uchida

Katsumura

2013

Self Cite

Water chemistry control is one of the key technologies to establish safe and reliable operation of nuclear power plants. Continuous and collaborative efforts of plant manufacturers and plant operator utilities have been focused on optimal water chemistry control, for which, a trio of requirements for water chemistry should be simultaneously satisfied: (1) better reliability of reactor structures and fuel rods; (2) lower occupational exposure and (3) fewer radwaste sources. Various groups in academia have carried out basic research to support the technical bases of water chemistry in plants. The Research Committee on Water Chemistry of the Atomic Energy Society of Japan (AESJ), which has now been reorganized as the Division of Water Chemistry (DWC) of AESJ, has played important roles to promote improvements in water chemistry control, to share knowledge about and experiences with water chemistry control among plant operators and manufacturers and to establish common technological bases for plant water chemistry and then to transfer them to the next generation of plant workers engaged in water chemistry. Furthermore, the DWC has tried and succeeded arranging R&D proposals for further improvement in water chemistry control through roadmap planning. In the paper, major achievements in plant technologies and in basic research studies of water chemistry in Japan are reviewed. The contributions of the DWC to the longterm safe management of the damaged reactors at the Fukushima Daiichi Nuclear Power Plant until their decommissioning are introduced.