Uncover the secrets of the emergency detection pro

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On April 8, the National Nuclear Accident Emergency Coordination Committee announced to the press conference that radioactive iodine-131, with a content of 0.57bq/kg, was detected in spinach samples collected at the sampling point of Wohu mountain in our province, which would not affect the human body. The release of this information also brought the Institute of Radiology, Shandong Academy of Medical Sciences, which has been the behind the scenes detection department, into everyone's vision for a time. On April 12, the public walked into the Institute to reveal how the mysterious radionuclide emergency detection was carried out

Xu jiaang is going to put the water sample into a cylindrical Marin cup

researchers are going to put the tested spinach into high-purity germanium γ EDS

the sampling and testing point in Jinan has a history of more than 20 years

on the afternoon of April 12, in the laboratory of the Institute of radiology of the Provincial Academy of Medical Sciences, I saw spinach and water quality samples just taken at random from the vicinity of Wohushan reservoir in Jinan this morning. Xu jiaang was responsible for testing these samples

Xu jiaang is an associate researcher in the protection monitoring room of the Institute of Radiology, Shandong Academy of Medical Sciences. Since the leakage of Fukushima nuclear power plant in Japan on March 27, almost all nuclear radiation emergency detection data in Shandong Province have been calculated from this laboratory and reported to the relevant departments by Xu jiaang

Xu jiaang said that the surroundings of Wohu mountain, dajinzhuang and Zhangqiu have been the environmental radiation detection points in Jinan for more than 20 years. In the past, the conventional detection was mostly once a quarter. Now, due to the impact of the Japanese nuclear leak, the emergency detection is once a day

Xu jiaang picked up a bucket marked with date and Wohushan and said that what was in this bucket was the sample taken from Wohushan reservoir this morning. Due to the different requirements between the emergency detection and routine detection of radionuclides in food and drinking water since March 27, the drinking water does not need to be evaporated, but directly detects the samples, and the water volume of each sample is guaranteed to be more than 1 kg. In the routine radionuclide detection of drinking water at ordinary times, the sample water volume is 20 kg. During the routine detection, the sample water should be evaporated and concentrated, and the detection time needs more than a week

as for why spinach was selected as the sample for testing, Xu jiaang explained that spinach is a leafy and large leafy vegetable with fluff on the surface of the leaves. It not only has a large contact surface with the air, but also is easy to absorb radioactive substances in the air, so he chose spinach as the sample for testing

after these water and vegetable samples collected from the southern mountainous area are brought back to the laboratory, the staff will also number them, and then register them in a register called the original inspection records of the Institute of Radiology, Shandong Academy of Medical Sciences. Sample registration items include "sampling point", "sample type", "sampling time", "inspection item" and other information. According to the contents of the register, the "entrusting unit" of this test is the "China CDC Institute of nuclear and safety medicine" (China CDC Institute of radiation protection and nuclear safety medicine - note), "test items" mainly include the "radioactive activity concentration" of iodine-131, cesium-134 and cesium-137

emergency detection: from 20 days to 20 hours

there is a big guy in the southeast corner of Xu jiaang's laboratory, "this is called high purity germanium γ Energy spectrometer, we rely on it for all our testing. " Xu jiaang said that such a professional instrument, worth more than 1 million yuan, can not only detect iodine-131, but also timely adjust the body to detect whether the sample contains cesium 137 and other nuclear fission products γ Radionuclides

high purity germanium γ The energy spectrometer is nearly 2 meters high and consists of upper and lower parts. The upper part is a lead chamber, which is mainly used to isolate the external environmental radiation interference during the detection process, and the lower part is used to place the Marin cup with samples γ Spectrometer probe and two liquid nitrogen tanks. The main function of the liquid nitrogen tank is to ensure γ The probe of the energy spectrometer works normally at a low temperature of -200 ℃. The minimum limit for the detection of radioactive substances by such a precise instrument is 0.3 Baker/kg. "It is extremely small that 0.3 Baker is combined with an extensive plastic granulator and an intelligent plastic granulator."

"Spinach samples need to be simply rooted and chopped before they can be filled with a special cylindrical Marin cup. Water is directly filled with this cup, and then open high-purity germanium γ The side door of the spectrometer can be directly put into it for continuous detection. "

when Xu jiaang was talking, he was paying close attention to high-purity germanium γ Data displayed on the computer connected to the energy spectrometer. And high purity germanium γ The energy spectrometer is connected with a digital spectrometer and a computer equipped with spectrum resolution software. Xu jiaang said that through the computer software, the γ The change of energy spectrum, and then analyze whether the sample contains radionuclides according to the change of energy peak

"in the past, we used to carry out routine tests on samples, which usually took 20 days." Xu jiaang told. In order to deal with the nuclear leakage crisis in Japan and monitor the radiation level of drinking water and food in Shandong in time, they launched emergency detection, reducing the time to about 20 hours

from 20 days to 20 hours, will the shortening of time affect the test results? Xu jiaang explained that if the radioactive substances in drinking water and food exceed the standard, a small number of samples can be simply pretreated to make them reach the detection configuration of the instrument. In fact, there is no lower limit of use for him. If we don't pursue the accuracy of data, complicated sample pretreatment procedures are no longer necessary. "Samples come every day and data are required every day. Routine testing is impossible." Xu jiaang said

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