RADIATION MEASURING APPARATUS, APPARATUS FOR IDENTIFYING WHETHER FUEL DEBRIS IS PRESENT AND MEASURING POSITION OF FUEL DEBRIS USING THE SAME, AND METHOD OF DETERMINING WHETHER FUEL DEBRIS IS PRESENT AND MEASURING POSITION OF FUEL DEBRIS

• Main Authors: OKADA KOICHI, MORI ISATO, HIRANO KATSUHIKO
• Format: Patent
• Language: English; Japanese
• Published: 03.08.2015
• Subjects: MEASUREMENT OF NUCLEAR OR X-RADIATION; MEASURING; PHYSICS; TESTING

PROBLEM TO BE SOLVED: To discriminate a gamma-ray sum peak of interference nuclides from a gamma-ray peak of a measuring target nuclide, and to identify whether a fuel debris is present and the position of the fuel debris in a nuclear reactor plant.SOLUTION: A radiation measuring apparatus comprises: a radiation detector 1 for detecting a radiation; a gamma-ray energy analyzer 3; a display device 4 for displaying a gamma-ray energy distribution; a collimator 91 for limiting a viewing angle of the radiation incident on the radiation detector 1; collimator drive means; and a shield body 25 for shielding the radiation detector 1. The collimator drive means moves the collimator 91 forward or backward with respect to the radiation detector 1 and the shield body 25, thereby making variable the viewing angle of the radiation incident on a radiation incident unit. The gamma-ray energy analyzer 3 finds a sum peak count value generated by the simultaneous incidence of a plurality of gamma-rays radiated from a plurality of radioactive nuclides other than the measuring target nuclide from a gamma-ray peak count value of the gamma-ray energy distribution, and calculates a gamma-ray peak count value of the measuring target nuclide from a difference between a gamma-ray peak count value of the measuring target nuclide obtained by the gamma-ray energy distribution and the sum peak count value. 【課題】妨害核種のγ線サムピークを測定対象核種のγ線ピークより弁別し、原子炉施設内での燃料デブリ有無及び位置を特定する。【解決手段】放射線を検出する放射線検出器１と、γ線エネルギー分析部３と、γ線エネルギー分布を表示する表示装置４と、放射線検出器に入射する放射線の視野角を制限するコリメータ９１と、コリメータ駆動手段と、放射線検出器を覆う遮蔽体２５とを備え、コリメータ駆動手段は放射線検出器及び遮蔽体に対してコリメータを前後に移動させることにより放射線入射部に入射する放射線の視野角を可変にし、γ線エネルギー分析部はγ線エネルギー分布のγ線ピーク計数値から測定対象核種と異なる複数の放射性核種から放射される複数のγ線の同時入射により生成されるサムピーク計数値を求め、γ線エネルギー分布より得られる測定対象核種のγ線ピーク計数値とサムピーク計数値との差分により測定対象核種のγ線ピーク計数値を算出する。【選択図】図９Ｂ