• Journal of Radiation Protection and Research
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• v.34 no.2
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• pp.87-94
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• 2009

Tritium is the one of the dominant contributors to the internal radiation exposure of workers at pressurized heavy water reactors (PHWRs). This nuclide is likely to release to work places as tritiated water vapor (HTO) from a nuclear reactor and gets relatively easily into the body of workers by inhalation. Inhaled tritium usually reaches the equilibrium of concentration after approximately 2 hours inside the body and then is excreted from the body with a half-life of 10 days. Because tritium inside the body transports with body fluids, a whole body receives radiation exposure. Internal radiation exposure at PHWRs accounts for approximately 20-40% of total radiation exposure; most internal radiation exposure is attributed to tritium. Thus, tritium is an important nuclide to be necessarily monitored for the radiation management safety. In this paper, metabolism for tritium is established using its excretion rate results in urine samples of workers at PHWRs and an effective half-life, a key parameter to estimate the radiation exposure, was derived from these results. As a result, it was found that the effective half-life for workers at Korean nuclear power plants is shorter than that of International Commission on Radiological Protection guides, a half-life of 10 days.

• Nuclear industry
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• v.36 no.3
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• pp.6-15
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• 2016

우리나라가 급속한 성장을 이루는 과정에서 원자력은 이를 뒷받침하며 함께 성장해 왔다. 그러나 그 과정에서 안전보다 성과를 강조하다보니 안전을 경시하는 비정상적 환경이 조성되었다. 그 결과 숨겨져 있던 과거의 원전 비리가 수면 위에 드러났고, 같은 시기에 후쿠시마 사고로 인한 오염수 유출과 전력난까지 발생하면서 국민의 불안과 불신을 가중시켰다. 국민들은 정부가 불안감을 해소해 주고 원칙을 지키는 안전규제, 신뢰할 수 있는 안전규제를 마련할 것을 요구하고 있다. 원자력 안전규제의 독립성을 확보하기 위해 지난 2011년 설립된 원자력안전위원회는 출범 이후 새로운 안전규제 제도 시스템을 마련하는 데 총력을 기울여 왔다. 원전 비리 같은 비정상 관행을 근절하기 위해 공급자 검사 제도, 성능검증기관 관리 제도 등 새로운 규제 시스템이 마련되었고, 방사선 작업 종사자 보호 강화와 생활 주변 방사선 감시 효율성 제고를 위한 다양한 제도적 장치들도 구비되었다. 이외에도 원자력안전규제기금 설치, 원전 부지별로 설치된 원자력안전협의회 실효성 제고 등 소통과 협업을 위한 시스템을 정착시켰다. 그러나 단순히 제도와 시스템이 만들어졌다고 해서 원자력 안전이 저절로 확보되는 것은 아니다. 차고 다닐 옥의 종류가 바뀌면 걸음걸이도 바꾸어야 한다는 개옥개행(改玉改行)의 고사성어에서처럼 제도가 바뀌면 그에 따른 일하는 방식 문화가 달라져야만 변경된 제도 시스템이 완전히 정착될 수 있을 것이다. 이를 위해서는 규제기관의 노력도 중요하지만 무엇보다 필요한 것은 원전 및 방사선 관련 사업자, 이해 관계자 나아가 일반 국민들이 이러한 달라진 제도 시스템을 이해하고 이에 적극 협조해 나가는 것이다. 본 기획 기사는 그러한 취지에서 그간 원자력안전위원회가 안전규제를 공고히 하기 위해 추진해 왔던 주요 규제 정책, 제도들을 소개하는 데 주안점을 두었으며, 이를 통해 원전 및 방사선 관련 사업자와 일반 국민들의 이해를 바탕으로 새로운 제도 시스템이 조기에 성공적으로 정착될 수 있기를 희망한다.

• Korean System Dynamics Review
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• v.15 no.2
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• pp.5-25
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• 2014

The purpose of this study is to analyze the effects of nuclear power plant workers and organizational characteristics on accidents, and seek the combination of policies for reducing accidents. For this purpose, it grasped, by using System Dynamics and Causal Loop Diagram, how various factors that cause accidents in nuclear plants are interrelated, and performed simulations after building simulation models. As a result of the analysis, first, the fundamental cause of safety accidents in nuclear power plants turned out to be the time constraint on the workload. Second, it turned out that as the workload of workers increases, physical and mental stresses increase, thereby increasing accidents due to errors and violations. Third, it turned out that as the levels of educational training and compliance with regulations and procedures are enhanced, accidents are reduced. Lastly, it turned out that as the combination of policies (reliance level + working environment + educational training + compliance with regulations and procedures) is increased, accidents are reduced. Especially, it turned out that if the combination of policies is increased by 30%, more than 10 cases of accidents are reduced.

• Journal of Radiation Protection and Research
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• v.36 no.3
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• pp.154-159
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• 2011

To evaluate the radiation exposure of workers participating in task where high radiation exposure is expected, two-dosimeter is typically provided radiation workers, one on the chest and the other on the back, at Korean nuclear power plants (NPPs). In a previous study, the NCRP (55:50) algorithm was selected as the optimal two-dosimeter algorithm (TDA) with various field tests and this TDA has been applied to all Korean NPPs since 2006. In 2007, the International Commission on Radiological Protection (ICRP) published the new ICRP recommendation, ICRP 103, which provides the revised weighting factors for both radiation and tissues and the new reference phantom. In this study, the applicability of current NCRP (55:50) algorithm at Korean NPPs for ICRP 103 was analyzed. As a result, it was found that the NCRP (55:50) algorithm is still effective to estimate the effective dose of workers under ICRP 103.

• Journal of Radiation Protection and Research
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• v.39 no.1
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• pp.14-20
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• 2014

A lot of radiation exposure for radiation workers who are engaged in Nuclear Power Plants, especially PWRs, have been caused during the outage by CRUD, such as $^{58}Co$, $^{60}Co$, in Reactor Coolant System. And therefore we need to know source terms to achieve optimization of protection for the radiation workers from radiation exposure at Nuclear Power Plants efficiently. This study analyzed source terms at domestic NPPs (PWRs) nearby Steam Generator with CZT semiconductor detector using by IN-VIVO method during the outage for the first time in the country. We checked difference for the detected source terms between old and new NPP. It was performed especially to see a change of source terms by water chemistry process as well. There was not any difference by water chemistry process both NPPs. The main source terms are $^{58}Co$ and $^{60}Co$ at all NPPs. $^{59}Fe$ only appears in the new NPP. $^{137}Cs$ and $^{95}Zr$ are shown in the old NPP. The fraction of $^{58}Co/^{60}Co$ in the new NPP is higher than the old NPP for increasing the specific activity of $^{60}Co$.

• Journal of Radiation Protection and Research
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• v.34 no.3
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• pp.121-128
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• 2009

During the maintenance period at Korean nuclear power plants, internal exposure of radiation workers occurred by the inhalation of $^{131}I$ released to the reactor building when primary system was opened. The internal radioactivity of radiation workers contaminated by $^{131}I$ was immediately measured using a whole body counter and the whole body counting was performed again after a few days. In this study, the intake estimated from the record history of entrance to radiation control areas and the measurement results of air sampling for $^{131}I$ in those areas, were compared with that from the results of whole body counting. As a result, it was concluded that the intake estimation using whole body counting and air sampling showed similar results.

• Journal of Radiation Protection and Research
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• v.37 no.3
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• pp.129-137
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• 2012

In the 2007 recommendation, the ICRP evolves from the previous process-based system of practices and intervention to the system based on the characteristics of radiation exposure situation. In addition, ICRP recommends the application of source-related dose constraints under the planned exposure situation as a tool for the optimization of protection to workers and the member of public. In this study, the analysis of radioactive effluents from Korean nuclear power plants and the public dose assessment were conducted in reference with the use of dose constraints. Finally, the measure to implement the dose constraints for the member of public was suggested taking into account multi-unit reactors operating at a single site in Korea.

• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.57-62
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• 2010

Maintenance on the water chamber of steam generator, the change of pressurizer heater, the removal of pressure tube feeder, and so on during outage in nuclear power plants (NPPs) has a likelihood of high radiation exposure to whole body of workers even short time period due to the high radiation exposure rates. In particular, it is expected that hands would receive the highest radiation exposure because of its contact with radiation materials. In this study, field tests on extremity dose assessment of radiation workers for contact works with high radiation exposure were conducted during the maintenance periods in Korean pressurized water reactors (PWRs) and pressurized heavy water reactors (PHWRs). In this field test, radiation workers were required to wear additional TLDs on the back and wrist, and an extremity dosimeter on fingers including a main TLD on the chest, while performing maintenance. As a result, it was found that the equivalent dose for fingers was distributed in the fixed range of deep dose and the equivalent dose for wrists.

• Journal of Radiation Protection and Research
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• v.28 no.3
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• pp.207-213
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• 2003

Carbon-14 is one of the major radionuclides released by CANDU Nuclear Power Plants(NPPs). It is almost always emitted as gas through the stack. From CANDU NPPs about 95% of all carbon-14 is released as carbon dioxide. Carbon-14 is a low energy beta emitter which, therefore, gives only a small skin dose from external radiation. As carbon dioxide Is physiologically rather inert gases for man's metabolism, the inhalation dose is probably less than 1 % of the ingestion dose. But this source of carbon-14, formed in a closed, nor-oxidative environment, was subsequently released into the workplace as an insoluble particulate when these systems were opened lip for re-tubing at CANDU NPPs. As a part of the improvement of dosimetry program at Wolsong Nuclear Power Plants, the carbon-14 metabolism based on references was investigated and studied to setup the internal dosimetry program due to inhalation of carbon-14.

• Journal of Radiation Protection and Research
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• v.33 no.4
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• pp.151-160
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• 2008

In Korean nuclear power plants (NPPs), two thermoluminescent dosimeters (TLD) were provided to workers who work in an inhomogeneous radiation field; one on the chest and the other on the head. In this way, the effective dose for radiation workers at NPPs was determined by the high deep dose between two radiation dose from these TLDs. This represented a conservative method of evaluating the degree of exposure to radiation. In this study, to prevent the overestimation of the effective dose, field application experiments were implemented using two-dosimeter algorithms developed by several international institutes for the selection of an optimal algorithm. The algorithms used by the Canadian Ontario Power Generation (OPG) and American ANSI HPS N13.41, NCRP (55/50), NCRP (70/30), EPRI (NRC), Lakslumanan, and Kim (Texas A&M University) were extensively analyzed as two-dosimeter algorithms. In particular, three additional TLDs were provided to radiation workers who wore them on the head, chest, and back during maintenance periods, and the measured value were analyzed. The results found no significant differences among the calculated effective doses, apart from Lakshmanan's algorithm. Thus, this paper recommends the NCRP(55/50) algorithm as an optimal two-dosimeter algorithm in consideration of the solid technical background of NCRP and the convenience of radiation works. In addition, it was determined that a two-dosimeter is provided to a single task which is expected to produce a dose rate of more than 1 mSv/hr, a difference of dose rates depending on specific parts of the body of more than 30%, and an exposure dose of more than 2 mSv.