Simulation of detection efficiency of a portable NaI(Tl) γ spectrometer for monitoring 131I in the thyroid / 中华放射医学与防护杂志

Objective:To simulate the effects of different thyroid-neck phantoms and monitoring positions on the detection efficiency of portable γ spectrometer, and to provide guidance for more accurate on-site measurement of 131I activity in the human thyroid. Methods:Based on the models of 4 typical thyroid-neck phantoms and a 3-inch NaI (TI) γ spectrometer used for the measurement of 131I in the thyroid and combined with the possible field monitoring scenarios, the Monte Carlo method was used to simulate and calculate the detection efficiency of the spectrometer under different conditions of monitoring distance, thyroid depth and thyroid volume. Results:The detection efficiency decreased significantly with the increase in the distance between the detector and the neck surface. The efficiency close to the neck surface was about 15 times that at 15 cm away from the neck surface. The detection efficiency decreased significantly with the increase in thyroid depth. When it was measured at the surface of the neck, the detection efficiency of thyroid at depth of 2 mm was about 3.6 times that of 30 mm. The detection efficiency decreases with the increase in thyroid volume. When it was measured at the neck surface, the detection efficiency of thyroid with 1 ml volume was 1.71 times that with 30 ml. The detection efficiency decreased with the center-point offset of the detector, especially at the neck surface, an offset of 2 cm would reduce the detection efficiency by about 15%.Conclusions:Not only the measurement distance used in calibration, but also the information of the depth and volume of thyroid in the neck-thyroid phantom, is important to know in advance for an accurate measurement of 131I activity in thyroid by using a portable gamma spectrometer.

Analysis of radionuclide content in the surface soil of Panjin, China / 中国辐射卫生

@#<b>Objective</b> To measure the specificactivity of natural and synthetic radionuclides in the environmental soil of Panjin, China and determine the content of radionuclides in the surface soil, and to conduct a scientific assessment of the radiation health risks of residents in this area. <b>Methods</b> Thirty-one surface soil samples were collected within the jurisdiction of Panjin, and a high-purity germanium detector was used for γ spectrum analysis to obtain the content of radionuclides and the current environmental radioactivity level. The two independent samples mean <i>t</i>-test was used to compare the specific activity data of radionuclides in soil samples between Panjin and Liaoning Province or China. <b>Results</b> The meanspecific activities of natural radionuclides ²³⁸U, ²²⁶Ra, ²³²Th, ⁴⁰K, and synthetic radionuclide ¹³⁷Cs in the surface soil samples of Panjin were 18.7 Bq/kg, 19.6 Bq/kg, 23.5 Bq/kg, 604.6 Bq/kg, and 0.9 Bq/kg, respectively. <b>Conclusion</b> The specific activities of natural and synthetic radionuclides in the surface soil samples of Panjin Area at the background level, causing a very low health risk to the people in this area.

The measurement method of gamma ray air absorbed dose rate based on LaBr3(Ce) detector / 中国辐射卫生

Objective Based on the lanthanum bromide scintillator detector, the calculation method of G(E) function was developed to measure the air absorbed dose rate. Methods Firstly, the gamma energy spectrumof the lanthanum bromide detector were simulated and the response functions with different energies were determined with Monte Carlo simulation method. Then, the G(E) function was calculated by the least square method. Finally, the air absorbed dose rate measured by the lanthanum bromide detector using G(E) function conversion method was compared with the theoretical calculation value based on the point source experiments. Results The experimental verification results showed that the relative deviation between thecalculated value with G(E) function and the theoretical calculation value wasmostly controlled within ± 6%, which verified the accuracy of G(E) function. Conclusion The results showed that the method of G(E) function could be applied to calculate the gamma radiation dose rate based on the in-situ the gamma spectrum with LaBr3 detector.

Assessment of committed effective dose from ingestion of 137Cs in seafood from coastal areas of Zhejiang province / 中华放射医学与防护杂志

Objective@#To investigate the contents of radionuclide 137Cs in seafood from coastal areas of Zhejiang province, and to estimate the annual committed effective dose to population in different regions from ingestion of 137Cs in seafood.@*Methods@#Three representative monitoring areas were set on the coastaline of Zhejiang province, and the locally popular seafoods were selected as monitoring objectives. The contents of radionuclide 137Cs were detected using HPGe γ spectrometry. The committed effective doses were estimated based on monitoring results and consumption data on seafoods in Zhejiang.@*Results@#The detection ratio of 137Cs in seafood produced on coastal areas of Zhejiang province was estimated to be 35.3% (36/102). Specific activity detected ranged from 0.004 to 0.140 Bq/(kg, Wet). Committed effective doses from ingestion of 137Cs in one year to the population in island region, coastal region and inland region were 3.03×10-5, 1.63×10-5, 3.38×10-6 mSv, respectively, far lower than the world committed effective dose resulting from internal exposure.@*Conclusions@#At present, the content level of 137Cs in seafood produced on the coastal areas of Zhejiang province is much lower than the national standard limit, and the dose burden to the population is very minor with no health impact to the population.

Assessment of committed effective dose from ingestion of 137 Cs in seafood from coastal areas of Zhejiang province / 中华放射医学与防护杂志

Objective To investigate the contents of radionuclide 137 Cs in seafood from coastal areas of Zhejiang province, and to estimate the annual committed effective dose to population in different regions from ingestion of 137 Cs in seafood. Methods Three representative monitoring areas were set on the coastaline of Zhejiang province, and the locally popular seafoods were selected as monitoring objectives. The contents of radionuclide 137 Cs were detected using HPGeγspectrometry. The committed effective doses were estimated based on monitoring results and consumption data on seafoods in Zhejiang. Results The detection ratio of 137 Cs in seafood produced on coastal areas of Zhejiang province was estimated to be 35.3％ ( 36/102 ) . Specific activity detected ranged from 0. 004 to 0. 140 Bq/( kg, Wet ) . Committed effective doses from ingestion of 137 Cs in one year to the population in island region, coastal region and inland region were 3. 03 × 10-5 , 1. 63 × 10-5 , 3. 38 × 10-6 mSv, respectively, far lower than the world committed effective dose resulting from internal exposure. Conclusions At present, the content level of 137 Cs in seafood produced on the coastal areas of Zhejiang province is much lower than the national standard limit, and the dose burden to the population is very minor with no health impact to the population.

Application of LabSoCS efficiency calibration method in rapid analysis at lab under emergency monitoring of the nuclear incidents / 中华放射医学与防护杂志

Objective To explore the effeetiviness of the method of LabSOCS(Laboratory sourceless calibration software)efficiency calibration in laboratory rapid analysis for emergency monitoring of nuclear incidents.Methods The detection efficiency of three kinds of environmental samples in emergency monitoring Wag calculated bY using the LabSOCS efficiency calibration method,and compared with the values that were obtained by way of radioactive source calibration method.Results The maximum relative deviation of the detection efficiency between the two methods was less than 15%,and the values with relative deviation less than 5%accounted for 70%.Conclusions The LabSOCS efficiency calibration method might take the place of radioactive source efficiency calibration method,and meet the requirement of rapid analysis in emergency monitoring of the nuclear incidents.