Dose Rate Detector for NPP’s Accidents
Photon Dose Rate Detector for Accidents of NPPs
Tech Area / Field
- FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors
- ENV-MIN/Monitoring and Instrumentation/Environment
3 Approved without Funding
NIKIMT (Institute of Assembly Technology), Russia, Moscow
- AO Kompozit, Russia, Moscow reg., Korolev\nScientific Engineering Center SNIIP, Russia, Moscow
- Institute for Advanced Studies, Japan, Tokyo
Project summaryAvailable experience in reactor operation, as well as in emergency works during Chernobyl and other accidents, showed that maximum operation temperature inside a containment can reach 250 °C during 1 hour and 207 °C during 5 hours by pressure to 0,7 MPa. By emergency systems operation during first day temperature decreased to 110 °C, pressure to 0,15 MPa. After two days temperature decreased to 20 – 60 °C, pressure to 0,09 – 0,12 MPa. According to IAEA requirements, by NPP accidents it is necessary to perform current monitoring of photon doze rate inside a containment. In this case there is a problem of high photon doze rate measurement, which maximum value can reach 105 Gr/h, minimum value – to 10-2 Gr/h. Operational conditions for such detectors are hard enough. According to radiation safety rules, for proper evaluation of radiation situation it is necessary to perform the doze rate measurements starting from photon energy 5 – 10 KeV. The upper level of energy range can be 3 – 8 KeV, according to different data sources.
By such operational conditions of detectors it is necessary to have their housings to be strength enough. Available at present engineering materials restrict capabilities of known detectors with energy level approximately to 60 KeV. The Table gives the characteristics of ionization chambers for photon doze rate inspection, produced by several firms.
The Table data shows, that ionization chambers for 250 °C and 0,7 MPa are not available at present time, that it does not meet modern requirements to safe operation of NPPs. Moreover, according to international safety rules, for protection from ionization sources, it is necessary to decrease photon raying energy to minimum possible level by providing of mechanical fastness of chamber’s structure and suitable rigid range for doze rate measurement.
The Project offer to develop a new photon dose rate detector for NPP accidental situations on base of choice and development of vacuum-tight, radiation-stable composite materials, of optimization of design and physical decisions for the housing and chamber’s electrode system, its gas atmosphere, as well as engineering solutions for manufacture of the chamber (welding, brazing, gluing, coating etc.). Characteristics of the ionization chamber to be developed under this Project shall be comply to ones specified in the right column of the Table. It shall allow to reach fulfillment of modern international requirements to safety operation of NPPs and observing of safety rules for radiation protection.