RADIATION PROTECTION

Criticality safety analysis on transport package offresh CEFR-MOX fuel assembly

CAO Pan, ZHOU Keyuan, ZHANG Qiang, LIU Zhaoyang

RADIATION PROTECTION. 2019, 39(2): 89-94.

Abstract ( 165 )

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Criticality safety analysis was carried out for the container loaded with fresh CEFR-MOX fuel assemblies using MCNP code and ENDF/B-V nuclear data. Several factors including package arrays, container damages under hypothetical accident condition and water moderation conditions were taken into account in criticality safety analysis of the transport of fissile material. The results show that the subcritical limit in this case is 0.924 6; the maximum k_eff of infinite packages array under normal situation is 0.574 4 and the maximum k_eff of infinite packages array under accident situation is 0.659 7. The criticality safety index (CSI) of fresh CEFR-MOX fuel assembly transport package is 0.

Study on selection of safety assessment software Ecolego solver

LIU Xingwei, WANG Xuhong, LV Tao, LI Xingyu

RADIATION PROTECTION. 2019, 39(2): 95-104.

Abstract ( 156 )

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Ecolego software has been widely used in safety assessment of radioactive waste disposal sites. The software provides lots of solvers, while the performance of different solvers varies greatly. How to select a suitable solver has caused troubles to users. On the basis of discussing the characteristics of each solver, the classical Swedish safety assessment model was tested with different solvers of Ecolego version 6.5. The results show that the NDF solver requires least calculating time in geosphere and whole models. BDF and RADAU5 solvers require the least time in near-field and biosphere models respectively. The Rosenbrock and TR-BDF2 solvers are accurate and stable. Considering the time-consumption and precision of calculation, the TR-BDF2 solver is recommended for safety assessment of high-level radioactive waste disposal sites which are similar to Sweden’s site.

Analysis on current situation of planning restricted zone of NPP in China

ZHANG Lu, XIONG Xiaowei, WANG Ping, WEI Guoliang

RADIATION PROTECTION. 2019, 39(2): 105-110.

Abstract ( 177 )

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Situations of legislative and regulatory documents about planning restricted zones of nuclear power plant (NPP) and existing planning restricted zones of NPP in China were briefly summarized and analyzed. Recommendations on addressing the double attributes of planning restricted zones, establishment of regulations on the planning restricted zone, interaction with NPP emergency response, environmental assessment under accident condition and regional planning for the planning restricted zone are provided.

Measurement of released tritium from nuclear facilities bydirect liquid scintillation counting

LI Xiaoyun, PAN Jingshun, LOU Hailin, XU Xutao, ZHAO Yang, WEN Fuping

RADIATION PROTECTION. 2019, 39(2): 111-117.

Abstract ( 194 )

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The release of tritium into environment from some nuclear facilities will cause tritium activity concentration variation in adjacent areas. The activity concentrations of tritium samples of air, ground water, rains and sea water around nuclear facilities were measured by a liquid scintillation counting (LSC) apparatus based on an external γ-standard method and an internal standard method. The relative deviations of these measurement data using the above two standard methods were -4.0% to 4.0%. The quenching calibration curves for four kinds of environmental water samples were made out according to internal standard efficiencies and the values of spectral quench parameter of the external standard (SQP(E)). The maximum difference between the efficiencies of two standard methods was 1.6%. The interference effects of carbon-14 and other β nuclides were generally negligible. For samples of efficiency value in the range of 21.5% to 24.5% without serious quench, their tritium activity concentrations were calculated using the external γ-standard quenching calibration curve with direct LSC measurement and relative deviations of results were between -6.35% to 4.41%, satisfying the requirements of routine monitoring of nuclear facilities.

Environmental monitoring of radiation level around NPP bases in China

WANG Lei, WANG Xiaofen, ZHAO Shunping

RADIATION PROTECTION. 2019, 39(2): 118-123.

Abstract ( 344 )

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In this paper, the summary of environmental supervisory monitoring around operating NPP bases in national environmental radiation monitoring network during 2011—2015 period was introduced. The monitoring results showed that in NPP bases surroundings, no abnormality of real-time gamma dose rates caused by NPP bases operation was monitored; Artificial radionuclide activity concentration was normal in ambient environmental medium of Fuqing NPP base; The tritium concentration in part of the environmental medium around Qinshan NPP base, Dayawan NPP base, Yangjiang NPP base, Tianwan NPP base and Ningde NPP base was increased compared with the background level before the operation of NPP base; The carbon-14 concentration in few air samples around Hongyanhe NPP base was above the background level; Traces of gaseous radioactive iodine-131 in few air samples around Dayabay NPP base were detected; There were traces of Ag-110m in few oyster samples around Qinshan NPP base, Dayabay NPP base and Ningde NPP base. However,the evaluation results showed that the public individual annual effective dose caused by the operation of NPP bases was far below the dose constraints value stipulated by government.

Feasibility study on application of iodine isotope exchange reaction inperformance evaluation of iodine adsorbers

GAO Linfeng, YAO Yanyan, WANG Lei, ZHANG Yuan, ZHAO Gaoxin

RADIATION PROTECTION. 2019, 39(2): 124-129.

Abstract ( 151 )

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An experimental scheme of iodine isotope exchange reaction for preparing radioactive methyl iodide is designed on the basis of characteristics of nucleophilic substitution reaction of halogenated hydrocarbon. According to safety management requirements of nuclear power plants, physical property analysis and toxicology analysis of experimental reagents are carried out. Tracer verification, iodine isotope exchange verification, experimental efficiency analysis, experimental safety analysis, reagent management method, and radioactive residue treatment were also studied for feasibility study of iodine isotope exchange reaction of radioactive methyl iodide preparation in performance evaluation of iodine adsorbers.

Application of TTA on the calculation of released source term

LI Lu, WEI Guoqiang, WANG Xiaoliang, BAI Xiaoping, ZHENG Wei

RADIATION PROTECTION. 2019, 39(2): 130-136.

Abstract ( 168 )

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According to the theory of Transmutation Trajectory Analysis (TTA ) and the characteristic of effluent released source term model, the paper developed a method of overall automatic searching linear decay chain, which covering all of the involving nuclear decay chain, and then deduced the analysis result of released source term equation. Through TTA method, the complicated network of decay chains are split into several linear decay chains and then each linear decay chain is analytically calculated to get the concentration of each nuclide. The TTA method was applied on the activity calculation of nuclear power plant released source term, and the calculated results of TTA method were compared by those of ORIGEN, and then the final released source term of TTA method was compared by the released source term in a nuclear power plant in China. The comparison results showed that most of the nuclides calculated by TTA are coincided with those of ORIGEN, and the short half-life nuclides calculated by ORIGEN were more conservative because of the simplified procession of decay chains and the approximation of secular equilibrium, and the released source term calculated by TTA method were in good agreement with those of Chinese NPP. The application of overall automatic searching TTA method on the calculation of released source term makes the results more comprehensive and more accurate.

Key issues and research progress of excavation damagezone in surrounding rocks of high-levelradioactive waste disposal repositories

CHEN Shiwan, WANG Guibin, YANG Chunhe, WANG Yong, SHI Wenbing

RADIATION PROTECTION. 2019, 39(2): 137-149.

Abstract ( 117 )

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Geological disposal of high-level radioactive waste (HLW) is to dispose HLW in a zone of 500 to 1 000 m beneath ground surface and isolate HLW from biosphere for a long period. The key issue of safety assessment is the long term capability of a geological disposal repository for isolating nuclides. It is inevitable to induce Excavation Damage Zone (EDZ) for surrounding rocks during underground engineering construction process, and the induced damage in EDZ will change physical and mechanical properties of surrounding rocks and potentially affect long term safety of the repository. Underground Research Laboratories (URLs) have been built in many countries such as Sweden (ASPO), Canada (URL), Finland (ONKALO), etc. Systematic field tests have been conducted to study the EDZ. In this paper, researches about EDZ built in crystalline rock in URLs are summarized, some key issues in EDZ study are discussed, and the prospect of EDZ studies in our URL is proposed. Overall researches in URL regarding EDZ are comprehensive and may be of great reference value for other underground engineering construction projects such as diversion tunnels and highway tunnels.

Dose effect of high-energy neutron radiation on Caenorhabditis elegans

XU Zhao, CHEN Ni, WANG Zhigang, LI Taosheng

RADIATION PROTECTION. 2019, 39(2): 150-156.

Abstract ( 190 )

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This paper studies the dose effect of high-energy neutron radiation on Caenorhabditis elegans and discusses the relative biological effects of high-energy neutron radiation. Hermaphrodite C.elegans were randomly divided into control group and 10 irradiation dose groups of 1 047, 476, 199, 89, 18.2, 8.4, 1.83, 0.351, 0.171 and 0.087 Gy, respectively. C.elegans in each group are placed in different distance from neutron source accordingly with same irradiation time. After a single high-energy neutron whole-body irradiation, part of C.elegans were transferred into the new dish immediately for follow-up detection of spawning rate and lifespan. The other part were transferred 24 hours later for germ cell death detection. The results showed that the spawning rate presented a general decline trend with the increase of dose, especially the damage of 1.83 Gy irradiation on the number of C.elegans progeny. C.elegans with more than 89 Gy radiation stopped spawning. The lifespan of C.elegans showed a trend of decreasing with the increase of radiation dose, particularly the shortening effect of 1.83 Gy was obvious. When irradiated C.elegans with greater than 8.4 Gy, the germ cell death rised significantly with the increase of dose. The above results show that high-energy neutron radiation has a dose effect on C.elegans. There might be a stronger damage effect at low dose, which provides scientific basis for neutron low-dose radiation protection. In this paper, it is also discussed that the relative biological effect of HINEG high-energy neutron radiation is 1.25, which is calculated by comparing the neutron irradiated data with the previous γ experimental results. It showed the biological effect difference between γ and neutron irradiation. The quality factor(Q)we suggested is different from that of ICRP report. It still needs more effort to improve the reference animal database.

Protective effect of curcumin on radiation-inducedpancreatic exocrine cell damage

LIU Xianrong, HE Liyan, LU Xianzhou

RADIATION PROTECTION. 2019, 39(2): 157-167.

Abstract ( 119 )

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In order to elucidate the stress response and energy metabolism of pancreatic exocrine cells induced by ionizing radiation, and to explore the role of curcumin in pancreatic exocrine cell radiation injury and its mechanism,the experiment of Rat pancreatic exocrine cells (AR42J) were established. The rats were divided into experimental group and control group. The two groups were divided into five subgroups of A/B/C/D/E, which were treated with 0, 2, 4, 8 and 16 μM curcumin, repectively. The experimental group was given a one-time high-dose X-ray irradiation (6 Gy), simulating acute radiation damage events. The expression of PARP, BCL-2, stress and energy metabolism related factors HIF-1ɑ, LDHA and PDH were detected by Wensten-blot. The cell viability was detected by MTT assay, Fluorescence detection of cell ATP and ROS production. The experimental results were further validated by in vivo experiments. 24 clean-grade rats were randomly divided into control group, simple drug-added group, simple irradiation group, irradiation + dosing group. Rats in each group were exposed to 12 Gy X-ray or simulated irradiation. The rats were killed 24 hours after irradiation, and the pancreatic tissue was dissected. The expression of energy metabolism related proteins was examined by Wensten-blot method. The results demonstrate: 1) Compared with the control group, the expression of PARP was increased and the BCL-2 protein was slightly down-regulated after 24 hours of irradiation. Meanwhile, the decrease of mitochondrial membrane potential (ΔΨm) was observed which indicated mitochondria damage. 2) The expression of HIF-1α was significantly increased by irradiation, and LDHA, the key factor of glycolysis was significantly increased and PDH expression was down-regulated. 3) MTT assay showed a decrease in cell proliferation and the production of ROS was increased by microplate reader. 4) Silence HIF-1α by RNA technology had eliminated irradiation-induced energy metabolism transformation partly. In the experimental group, the increased expression of HIF-1α and LDHA was reversed by curcumin treatment, PDH was partially restored, the free radical scavenging was effectively removed, and the proliferation of cells and the ATP production were increased. 5) The animal experiments have got the same results. The expression of HIF-1α is up-regulated by ionizing radiation stress in pancreatic exocrine cells, which leads to the change of energy metabolism as the enhancement of glycolysis pathway and the inhibition of aerobic oxidation of mitochondria. Curcumin reduces the energy metabolism disorder induced by radiation by down-regulating HIF-1α, and effectively scavenges oxygen free radicals and protects mitochondria, thus exerting its protective effect on pancreatic exocrine cells.

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