| 摘要 |
PURPOSE:To prevent the occurrence of hydrogen-crack by keeping the surface potential of the metal member in primary cooling water and the furnace water of a nuclear reactor more noble than the potential becoming the active region of the metal of said metal member and the potential becoming the limit concn. of hydrogen causing no generation of hydrogen-crack. CONSTITUTION:A control rad 6 is arranged in a reactor pressure vessel 1 and constituted by receiving a B4C tube 7 wherein a fine SUS 304 tube is filled with a B4C powder in a cross-shaped sheath made of SUS 304. The specific concn. of dissolved oxygen is set in order to prevent the corrosion of the B4C tube made of SUS 304 or the piping of a recirculation system having some fear for causing hydrogen-crack. A hydrogen injection system 8 is arranged to the piping of a water supply system and operated in conjunction with a DO sensor 9. In this case, the injection amount of hydrogen is allowed to be connected with the output of the DO sensor 9 and the concn. of dissolved oxygen is controlled to 5ppb-50ppb to make it possible to hold predetermined potential. By this method, the stress corrosion cracking (SCC) of the B4C tube and the piping of the recirculation system is not generated and hydrogen-crack can be prevented.
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