# US 9,435,899 B1 · Radioactive gas monitoring device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,435,899 B1 - Document ID: US9435899B1 - Status: Granted - Kind: B1 - Application number: 14/864,021 - Filed: 2015-09-24 - Granted: 2016-09-06 - Earliest claimed: 2015-05-21 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Toshihide Aiba; Kenichi Moteki - Web page: https://patentgrep.com/patent/US9435899B1 ## CPC - G01T 1/208: Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section - G01T 1/178: for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water - G01T 1/2008: {using a combination of different types of scintillation detectors, e.g. phoswich} - G01T 1/203: the detector being made of plastics - G01T 1/2992: {Radioisotope data or image processing not related to a particular imaging system; Off-line processing of pictures, e.g. rescanners (for measuring radiation intensity G01T1/1663; digital computing or data processing equipment or methods specially adapted for nuclear physics or nuclear engineering G06F15/00; general purpose image data processing G06T1/00; computerized tomography G06T12/00)} - G21C 17/00: Monitoring; Testing (measuring in general G01); {Maintaining} - Y02E 30/30: Nuclear fission reactors - G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00) - G21C: NUCLEAR REACTORS (fusion reactors, hybrid fission-fusion reactors G21B; nuclear explosives G21J) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A radioactive gas monitoring device includes a sample chamber into which a sampled gas is introduced; a plastic scintillation detector outputting first detection signal pulses; an inorganic crystal scintillation detector outputting second detection signal pulses; a first measurement unit calculating a first count rate from the first detection signal pulses to output the first count rate, and issuing a first alert when the first count rate becomes higher than a first preset level and issuing a second alert when the first count rate becomes higher than a second preset level higher than the first preset level; and a second measurement unit calculating a second count rate from the second detection signal pulses to output the second count rate, and issuing a third alert when the second count rate becomes higher than a third preset level. ## Claims ### Claim 1 A radioactive gas monitoring device comprising: a sample chamber into which a sampled gas is introduced; a plastic scintillation detector detecting radiation emitted from the sampled gas introduced into the sample chamber to output first detection signal pulses; an inorganic crystal scintillation detector detecting radiation emitted from the sampled gas introduced into the sample chamber to output second detection signal pulses; a first measurement unit calculating a first count rate from the first detection signal pulses to output the count rate, and issuing a first alert when the first count rate becomes higher than a first preset level and issuing a second alert when the first count rate becomes higher than a second preset level higher than the first preset level; and a second measurement unit calculating a second count rate from the second detection signal pulses to output the count rate, and issuing a third alert when the second count rate becomes higher than a third preset level. ### Claim 2 (depends on 1) The radioactive gas monitoring device of claim 1, wherein the second measurement unit has a window whose center is set at 0.511 MeV. ### Claim 3 (depends on 2) The radioactive gas monitoring device of claim 2, wherein the first measurement unit calculates the first count rate under a condition of a constant standard deviation, and the second measurement unit calculates the second count rate under a condition of a constant standard deviation. ### Claim 4 (depends on 3) The radioactive gas monitoring device of claim 3, wherein the first count rate is inverse-proportional to a time constant of the first measurement unit, and the second count rate is inverse-proportional to a time constant of the second measurement unit. ### Claim 5 (depends on 2) The radioactive gas monitoring device of claim 2, wherein a fourth level is set to be half of a summation of the third level and a background count rate, and the second measurement unit calculates the second count rate under a condition of a constant measurement time until the second count rate reaches the fourth level and calculates the second count rate under a condition of a constant standard deviation when the count rate exceeds the fourth level. ### Claim 6 (depends on 1) The radioactive gas monitoring device of claim 1, wherein the second measurement unit calculates the second count rate from the second detection signal pulses so that the 1.461 MeV peak is located at a fixed position in a spectrum. ### Claim 7 (depends on 2) The radioactive gas monitoring device of claim 2, wherein the second measurement unit calculates the second count rate from the second detection signal pulses so that the 1.461 MeV peak is located at a fixed position in a spectrum. ### Claim 8 (depends on 3) The radioactive gas monitoring device of claim 3, wherein the second measurement unit calculates the second count rate from the second detection signal pulses so that the 1.461 MeV peak is located at a fixed position in a spectrum. ### Claim 9 (depends on 4) The radioactive gas monitoring device of claim 4, wherein the second measurement unit calculates the second count rate from the second detection signal pulses so that the 1.461 MeV peak is located at a fixed position in a spectrum. ### Claim 10 (depends on 5) The radioactive gas monitoring device of claim 5, wherein the second measurement unit calculates the second count rate from the second detection signal pulses so that the 1.461 MeV peak is located at a fixed position in a spectrum.