RADIATION PROTECTION

Research on framework system of source term in primary circuit and emission source term at nuclear power plants

FANG Lan, LIU Xinhua, ZHU Zhaowen, XU Chunyan

RADIATION PROTECTION. 2020, 40(2): 89-98.

Abstract ( 190 )

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There are still some problems in the application of original source terms in operating nuclear power plants imported from different countries, including France, USA and Russia, because of their different regulatory requirements and safety considerations. Some unreasonable design of source terms will directly affect the accuracy of emission source terms and rationality of source terms for environmental impact assessment. In order to solve these problems, frameworks for primary circuit source terms and emission source terms are studied, established and described, to which could provide a technical basis for the calculation of source terms in Hualong-1 and CAP1400 reactors.

Preliminary study on source term model for advanced SMR siting based on RG 1.183

HU Yu, FANG Dong, ZHU Xuenong

RADIATION PROTECTION. 2020, 40(2): 99-103.

Abstract ( 185 )

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Based on the scenarios of hypothetical accidents described in RG 1.183 “Alternative radiological source terms for evaluating design basis accidents at nuclear power reactors”, considering the design features of most of the current advanced small modular reactor (SMR) on &|under ground layouts, the calculation model of the source term of large pressurized water reactor was improved: based on the radioactive conservation equation in the containment, considering the obstacles and retention of the auxiliary building, the radioactive conservation equation in the auxiliary building was established. Taking an advanced small modular reactor nuclear power plant as an example, the radioactive release of the representative nuclides was calculated using the new model and compared with the existing model.

Radiation safety analysis on tritium exposure of He-3 loop

LI Binglin

RADIATION PROTECTION. 2020, 40(2): 104-109.

Abstract ( 200 )

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The use of He-3 loop for power transient test of LWR fuel element raises tritium safety issues due to occupational exposure. This paper proposed some protection programs of tritium and the tritium decontamination in He-3 loop, and analysed the tritium source term and the hazard of the tritiated water vapor. Then, the normal and accidental release rates of tritium from He-3 loop into the glove-box and working area are discussed. The released tritium can be treated safely. Finally, the intake doses for internal exposure of tritium are calculated through each pathway based on the failures of He-3 system safety measures. The results show the maximum individual doses to the operator are 1.27 μSv/d in normal operation and less than 10 mSv if not all the protective precautions fail or loss simultaneously in an extreme accident case.

Experimental research on radiation protection shielding performance of autoclaved aerated concrete blocks

LU Yang, ZHANG Yonggui, DU Zhong , CHEN Zhi, TAO Zongshuo

RADIATION PROTECTION. 2020, 40(2): 110-114.

Abstract ( 151 )

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In this paper, using X-rays generated at different tube voltages (70 kV to 120 kV) with the same tube current (25 mA), four commonly used autoclaved aerated concrete block samples in China were irradiated and the air absorption dose rate was measured at the fixed point after the X-rays passed through each sample. The results show that: (1) the equivalent lead equivalent thickness of autoclaved aerated concrete block under the condition of 70 kV to 120 kV increases first and then decreases with the increase of tube voltage, reaching the maximum at 90 kV (2) the equivalent lead equivalent thickness of four kinds of autoclaved aerated concrete blocks is more than 1.0 mm, and autoclaved aerated concrete can be used as radiation protection material in some machine rooms (3) the equivalent lead equivalent thickness of autoclaved aerated concrete block is related to the dry density and thickness of the material, which is independent of compressive strength.

A shielding practice with silica sands for an intermediate level radioactive waste pit in order to enlarge the opening

LIU Dengkui, ZHANG Jinsong, LI Zhenchen, XU Jiang

RADIATION PROTECTION. 2020, 40(2): 115-119.

Abstract ( 173 )

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In order to retrieve the waste from a waste pit with small opening, the silica sands packaged in a canvas bag was used to shield the intermediate level waste (ILW). The shielding depth was calculated with QAD-CG, and the filling and retrieve of silica sands was well prepared and practiced. The dose rate at the opening was reduced from 4.28 Gy/h to 4.49 μGy/h. The waste retrieve work went on smoothly. The personnel collective dose to set and dismantle the silica sands shielding facility is 0.45 men·mSv in total.

Discussion on potential surface contamination risk management of a nuclear power plant

REN Xueming, LI Xiaoning, MA Boyang

RADIATION PROTECTION. 2020, 40(2): 120-125.

Abstract ( 168 )

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A nuclear power plant adopts the international advanced “EVEREST” access controlled area mode, which allows personnel enter and leave the radiation controlled area in ordinary labor protection clothing. In order to avoid or reduce contamination spread and human contamination caused by accidental leakage of equipment in the radiation controlled area, the potential contamination risk management method were adopt in the controlled area of the nuclear power plant, which includes analyzing the reliability of the radioactive media inclusion of the main equipment in the nuclear loops and the causes of the contamination events that have occurred, identifying the potential contamination area, dividing the controlled area and setting boundaries for potential contamination area and the actual contamination area, and providing the personal protection accordingly.

Study on axial thermal conductivity of bentonite-sand mixed buffer layers

LIU Ping, ZHAO Liang, JIAO Dading, WAN Jiajie, YANG Hongrui

RADIATION PROTECTION. 2020, 40(2): 126-136.

Abstract ( 108 )

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Physical and mechanical properties of bentonite-sand mixtures have important influence on the stability and safety of a high level radioactive waste repository when they are used as buffer materials for high level radioactive waste repository, which may be affected by the decay heat released from high level radioactive wastes. Some heat conduction simulation tests for small samples with different dry density, water content, and sand content were carried out using a designed device in our study. The thermal-mechanical coupling process of buffer layer was simulated and analyzed, and variation and distribution of temperature, stress and strain of buffer layers were obtained with a focus on the influence of temperature. The results show that the increasing of dry density, water content and sand content can increase thermal conductivity and strain, stress is affected by temperature and reaches equilibrium earlier, and the temperature, stress and strain of buffer layer near heat source are the largest and decrease along the axial direction, with obvious change at the initial period.

Design and verification of a descaling scheme for radioactive waste liquid evaporator

SHAO Yanjiang, LI Li, MU Jianbo, ZHAO Dapeng, LONG Bokang, CHE Jianye

RADIATION PROTECTION. 2020, 40(2): 137-143.

Abstract ( 134 )

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In view of an obvious decline in processing capacity of radioactive liquid waste evaporator in a short period of time, the method of Langelier Saturation Index (LSI) was used to judge the scaling and corrosion tendency in the evaporator. Effects of pH, evaporation temperature, Ca²⁺ concentration and stock solution flow rate on evaporation scaling rate were analyzed. The results show that the evaporation liquid has the tendency of scaling and corrosion. Variations of pH and other factors increase the scaling rate of the evaporator. After scaling, the evaporation intensity of the evaporator decreases by 75%. An immersion acid descaling scheme for radioactive waste liquid evaporator was designed, based on commonly used descaling methods for civil evaporators and combining with safety requirements of nuclear industry evaporators. It has been verified by experiments that this scheme is safe and feasible. The descaling effect is obvious, and the processing capacity of the evaporator has restored to its original design value of 0.6 m³/h after descaling.

Performance research on an engineering scale prototype activated carbon delay bed for radioactive waste gas system

LI Yongguo, LIU Yu, QIU Dangui, LIU Qun, YU Weiyue, CHANG Shen, HU Bo, YU Jie, HAN Lihong, HOU Jianrong

RADIATION PROTECTION. 2020, 40(2): 144-149.

Abstract ( 197 )

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A prototype delay unit of radioactive noble gas with process flow was established and some experiments simulating different airflow parameters of nuclear power plants were carried out. Experimental results of performance testing show that the gas cooler meets dehumidification requirements. The silica gel bed can dry gas flow to the required level of relative humidity. And the activated carbon delay bed has good retention capability for noble gas. Therefore the designed prototype delay unit for radioactive noble gas is applicable for nuclear power plants.

Combined application of two testing methods for performance evaluation of nuclear air cleaning systems

ZHANG Jirong, ZHANG Deshan, WU Tao, LI Yongguo, WANG Kunjun, LI Yanzhang, LI Shijun, HAN Ming, QIU Dangui, KONG Haixia

RADIATION PROTECTION. 2020, 40(2): 150-155.

Abstract ( 149 )

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At present, the domestic standards for performance evaluation of nuclear air cleaning systems are established on the basis of combining American and French systematic standards with practical engineering experiences in China. Generally, performance tests of some nuclear air cleaning systems are carried out only using the American systematic methods or the French systematic methods. We hereby suggest the utilization of combination of both American and French systematic standards to implement performance tests of nuclear air cleaning systems to completely evaluate their characteristics for satisfying requirements of safety, radiation protection and management.

Application of adaptive statistical iterative reconstruction-V and 70 kVp in adult paranasal sinus CT scan

YU Zeyang, JIA Yingchun, WANG Haoyu, HU Zhijun

RADIATION PROTECTION. 2020, 40(2): 156-161.

Abstract ( 174 )

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To investigate the weight of the Adaptive Statistical Reconstruction-V (Asir-V) algorithm to obtain the best image quality while reducing the effective radiation dose in adult paranasal sinus Revolution CT examination of 70 kVp. Revolution CT was applied to perform paranasal sinus scans in 20 cases of adults. The scanning conditions were 70 kVp, 230 mA. The original projection data, a total of 120 images were obtained, were reconstructed by using different weights (0, 20%, 40%, 60%, 80%, 100%) of the Pos-Asir-V technique. Six groups of each case of pictures were subjective rated and objective evaluated. The objective evaluation included the evaluation of noise (standard deviations, SD) and contrast noise ratio (CNR). The subjective rating was evaluated by two evaluation physicians for image quality scores and for their subjective consistency. After each patient had completed the scan, its dose-length product (dose-length product, DLP) and CT volumetric dose index (CT dose indexvolume, CTDI_vol) were recorded and their average effective radiation dose (effective dose, ED) was calculated. The objective evaluation results showed that the Asir-V image noise with different weights decreased with the Asir-V weight, the CNR increased with the Asir-V weight, and the effective radiation dose(ED) significantly decreased compared with the average radiation dose of the regular head and neck CT examination. The subjective evaluation results showed that the Asir-V image scores with different weights were different, with a high score of 60% at Asir-V, and the subjective evaluation of two doctors was good. Combined with the subjective and objective evaluation results, it is concluded that the image of Asir-V 60% in 70 kVp, 230 mA adult paranasal sinus Revolution CT examination could meet the needs of clinical diagnosis and significantly reduce the effective radiation dose.

Practice on a new mode of nuclear accident emergency exercise in nuclear power plant

ZHU He, LIU Bin, JIN Li, WANG Maojie, HAO Limin, LI Langxin, WANG Min, YUE Huiguo, FENG Jianping

RADIATION PROTECTION. 2020, 40(2): 162-167.

Abstract ( 222 )

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The current situation and existing problems of nuclear accident emergency exercises were studied. A new nuclear emergency exercise mode of “no notice before exercise, no exercise script, no specified preparation as well as superimposition of multiple emergencies” were explored. The advantage of this new mode of exercise was analyzed and the ways to carry out further related work in depth were discussed.

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