A method for continuously measuring the concentration of thoron progeny

Abstract

The invention relates to a monitoring technology for radioactive aerosol in an environment and discloses a method for continuously measuring concentrations of thoron daughters in the environment for limited times without replacing filter membranes. The method includes: measuring concentrations and of 220Rn daughters in a to-be-measured environment by primary sampling, and then, using an alpha-particle detector for measuring integral counting Nj(alpha)[Tj1, Tj2] and Nj(alpha)[Tj2, Tj3] of 8,78MeV alpha-particles emitted by a sample obtained by jth sampling within the time periods of [Tj1, Tj2] and [Tj2, Tj3] after continuing sampling for t0min without replacing the filter membranes; computing to obtain Nj''(alpha)[Tj1, Tj2] and Nj''(alpha)[Tj2, Tj3] according to the formulas (19a) and (19b); computing concentrations and of the 220Rn daughters in the to-be-measured environment according to the formula (20).

Description

technical field [0001] The invention relates to a monitoring technology of radioactive aerosol in the environment, which is a method for continuously measuring the concentration of thoron progeny in the environment for a limited number of times without changing the filter membrane. Background technique [0002] Thoron (i.e. 220 Rn) and radon (ie 222 Rn) is also a radioactive inert gas, and is one of the main sources of natural radiation exposure. 222 Rn places almost have 220 Rn. But people in the environment 220 Much less attention has been paid to the hazards of Rn and its daughters, because on the one hand, in most cases, 220 The dose caused by Rn and its progeny and 222 The comparison between Rn and its daughters is almost negligible ( 222 Rn, 220 Rn's decay stand chain see figure 1 ),on the other hand 220 Rn half-life is very short (55.6s), the environment 220 Rn is unevenly distributed, 220 The balance relationship between Rn and its daughters is more compl...

AI Technical Summary

Problems solved by technology

in existing 220 Among the Rn daughter level measurement methods, the solid nuclear track method has a simple structure and does not require a power source, and can achieve long-term measurement, but it can only calculate 220 The average concentration of the Rn progeny, the exposure time usually needs more than 3 months, and is also affected by the deposition rate of the measurement environment; the measurement period of the total α method is too long (more than 8 hours), when 222 When the level of Rn progeny is high, the residual 222 The interference of Rn daughters, the method error is relatively large, and only the instantaneous concentration can be measured, and its response time is too long, so it is not suitable 220 On-site continuous monitoring of the environment where the Rn daughter level changes; although the liquid scintillation method has the advantages of high sensitivity, strong anti-interference ability, and good stability, the measurement process is complicated, it is not easy to achieve continuous measurement, and it can only be carried out in the laboratory.

Currently commonly used 220 Rn daughter body level continuous measurement devices mainly include Canada’s WLx, Germany’s LCD-BWLM and other working level monitors, and Germany’s SARAD company’s 222 Rn / 220 Rn and its daughter continuous measuring instrument EQF3120, although the first two have the advantages of convenient operation, energy differentiation and continuous measurement, but it takes more than 8 hours to get a more reliable 222 Rn progeny concentration and 222 Rn daughter body, 220 Rn daughter potential, cannot be given 220 Rn daughter body concentration, while EQF3120 can only give 222 Equilibrium Equivalent Concentration (EEC) of Rn daughters; there is also the CAM-2 series radioactive aerosol monitor developed by the China Radiation Research Institute, which uses a mechanical device to pull a long roll of filter membrane at the end of each measurement Automatic replacement of the filter membrane to achieve 220 Rn, 222 Continuous measurement of Rn daughters, such instruments require high-quality filter membranes and transmission devices as well as high airtight performance

Their disadvantages are complex structure, cumbersome use and maintenance, and not easy to carry

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