SHIELDING BODY FOR RADIATION MEASUREMENT

PURPOSE:To enable an absorption of a deviation with an extent of a setting error generated from a positioning relationship between primary cooling system pipings and detector guide tubes by forming a space between a neutron shielding material and a lead shielding body to absorb the setting error of the detector guide tubes. CONSTITUTION:Around a neutron flux detector 2, neutron shielding materials 5 such as polyethylene which moderate neutrons and improve a detection efficiency, are provided at an outside of a detector guide tube 4. Around a moderator 5, a lead shielding body 6 which weakens a gamma ray from a primary cooling system pipings 1 to a level lower than an allowable back ground level of the detector 2 and also prevents a back ground to be raised by photoneutrons generated from the gamma ray hitting the moderator 5, is also provided. A space 8 to absorb a setting error of the guide tube 4 is formed between the shielding body 6 and the moderator 5. The space 8 is formed, for example, by providing a penetration pit of which diameter is larger than an outer diameter of the moderator 5, on the shielding body 6. With this procedure, a deviation with an extent of a setting error generated from a positioning relationship among pipings 1, the guide tube 4 and each other guide tubes, can be absorbed, and the detector 2 can be installed.