• Nuclear Engineering and Technology
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• 제53권1호
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• pp.351-356
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• 2021

Korean nuclear power plants (NPPs) have various radiation protection programs to attain radiation exposure as low as reasonably achievable (ALARA). In terms of ALARA, this paper provides a comprehensive overview of administrative dose control for occupationally-exposed workers in Korean NPPs. In addition to dose limits, administrative dose constraints are implemented to resolve an inequity of radiation exposure in which some individuals in NPPs receive relatively higher doses than others. Occupational dose constraints in Korean NPPs are presented in this paper with the background of how those values were determined. For pressurized water reactors, 80% and 90% of the annual average limit for an effective dose, 20 mSv/y, are set as the primary and secondary dose constraints, respectively. Pressurized heavy water reactors (PHWRs) have also established the primary and secondary dose constraints corresponding to 70% and 80% of the effective dose limit, and additional constraints for tritium concentration are provided to control internal exposure in PHWRs. Follow-up measures for exceeding these administrative dose constraints are also introduced compared to exceeding the dose limits. Finally, analysis results of dose distributions show how the implementation of administrative dose constraints impacted the occupational dose distributions in Korean NPPs during the years 2009-2018.

• 방사선산업학회지
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• 제17권1호
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• pp.61-67
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• 2023

A Study on the Introduction of Dose Constraints for Occupational Exposures: Focusing on Experts' Opinions by Field of Radiation Industry. The International Commission on Radiological Protection suggests Justification, Optimization, and Dose Limits as the three principles of radiological protection, among which, as a means of protection optimization, ICRP 103 recommends to set dose constraints. In this study, opinions are collected from experts in each category of radiation industries for stakeholder participation to qualify dose constraints. A guidance and questionnaire for analyzing the dose constraints have been developed for their collection, and opinions were collected from radiation protection experts in selected categories. 20 out of 22 experts, consisted with 91%, have assessed the dose constraints setting is necessary, and 2 experts, consisted with 9%, assessed it is unnecessary. The average of dose constraint presented by experts for RI production institutions is to be the highest level of 15.3 mSv, and light-water reactors (14.6 mSv), non-destructive inspection (14.4 mSv), heavy-water reactor and medical institutes (13.9mSv) is to be above the overall average dose constraint. In case of public institutions, the average dose constraint is to be 8.6mSv, and research institutions (8.8mSv), educational institutions (9.6 mSv), waste disposal sites (9.7 mSv), and general industries (10.6 mSv) are resulted to below the overall average dose constraint. As for the means of setting dose constraints, 8 experts out of 22 suggested setting dose constraints for each specific industry or task. And, 5 experts especially suggest setting dose constraints for the specific groups with relatively high exposure, such as workers with above the record levels. As a countermeasure for workers who exceed the dose constraints, 15 experts out of 22 expressed that the cause analyses for them and preparation for a plan of reducing them are necessary.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3660-3671
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• 2022

A new methodology to derive a dose constraint for radioactive effluent from a unit of nuclear power plant (NPP) through retrospective assessment was developed to reflect operational flexibility in line with international standards. The new dose constraint can retain the safety margin between the offsite dose and the past dose constraints. As case studies, the new approach was applied to 24 Korean NPPs to address the limitations of the existing seven dose constraints that do not fully comply with current international radiation protection standards. Therefore, an effective dose constraint for Korean NPPs was proposed as no less than 0.15 mSv/y, which is comparable to the international practices and previous studies (0.05-0.3 mSv/y). Although the lower bound of the equivalent dose constraint was calculated as 0.17 mSv/y, it is not proposed in this study since the compliance with the derived effective dose constraint can prevent accompanied equivalent doses to any organs from exceeding equivalent dose limits. The new framework and the case studies are expected to contribute toward and support the revision of existing dose constraints for radioactive effluent from NPPs, ensuring better compliance with the current international safety standards as well as reflect the operational flexibility in practice.

• Journal of Radiation Protection and Research
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• 제37권3호
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• pp.129-137
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• 2012

국제방사선방호위원회(ICRP)는 2007년 발행된 ICRP 103 권고를 통해, 행위와 개입으로 대변되는 방사선방호 지침을 각 피폭상황 별로 적용하도록 변경하여 권고하였다. 이 지침에는 계획피폭상황에서 방사선방호 최적화의 수단으로 방사선작업종사자와 일반인에 대해 선원중심의 선량제약치(dose constraint)를 설정하여 운영하도록 권고하고 있다. 이 논문에서는 계획피폭상황에서 일반인 선량제약치를 설정하는데 필요한 국내 원전의 방사성물질의 배출량과 이에 따른 주변주민의 피폭방사선량 평가 결과를 분석하였다. 이를 바탕으로 국내 원전의 동일부지 내 복수호기 원전의 운영을 고려한 선량제약치 설정 방안을 제시하였다.

• Journal of Radiation Protection and Research
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• 제36권3호
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• pp.127-133
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• 2011

국제방사선방호위원회에서는 2007년에 방사선방호에 관한 권고(ICRP 103)를 개정하였다. 이에 따라 국제원자력기구에서도 전리방사선 방호에 관한 국제기본안전기준을 개정하고 있으며 국내에서도 신권고의 내용을 국내요건에 반영하기 위한 연구가 진행 중이다. 신권고가 기존 권고에서 크게 변화되지 않았지만 방사선산업의 성장으로 인해 작은 변화에도 큰 영향을 가져올 수 있기 때문에 신권고의 내용을 국내 반영하기 위한 준비가 필요하다. ICRP 103의 주요 특징중 하나는 기존 권고에 비해 방호최적화를 한 단계 더 강조한 것이다. 이를 위해 계획피폭상황에서 선량제약치를, 기존 및 비상피폭상황에서 참조준위를 사용할 것을 권고하였다. 선량제약치는 전망적이고 선원중심적 제한값으로서 개인에 대한 방호의 기본 수준을 제공하며, 그 선원에 대한 방사선방호 최적화에 상한 선량 역할을 하게 된다. 이에 따라 국내에서도 원자력 및 방사선이용시설에 대해 선량제약치 운영이 요구될 것이다. 규제기관과의 협력과 더불어 직무피폭에 관한 선량제약치를 사업자가 설정하고 운영함으로써 최적화가 더 강조될 수 있을 것으로 예상된다. 선량제약치가 규제도구가 아닌 방사선방호최적화를 위한 절차로 국내 적용되기 위한 방안을 도출하였다.

• 한국의학물리학회지:의학물리
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• 제21권3호
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• pp.298-303
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• 2010

전립선암에서 세기조절방사선치료와 입체조형방사선치료의 선량분포 특성을 비교하였다. 세기조절방사선치료에서는 치료계획표적용적에 200 cGy를 33회 조사하여 6,600 cGy가 조사되도록 하였다. 세기조절방사선치료에서는 PTV의 최대선량이 104.4%이었으며, 최소선량이 89.5%였으며, 삼차원입체조형치료에서는 PTV의 최대선량이 105.3%이었으며, 최소선량이 85.5%을 나타내었다. 100%에 대한 CI는 세기조절방사선치료에서 1.02였으며, 삼차원입체조형치료에서는 0.97을 나타내었다. 중요장기 직장에 대해서 세기조절방사선치료에서는 5,000 cGy 이상이 34.0%였으며, 삼차원입체조형치료에서는 63.3%였고, 방광에 대해서 세기조절방사선치료에서는 4,000 cGy 이상이 30.1%였으며, 삼차원입체조형치료에서는 30.6%였고, 오른쪽 대퇴골두부에 대해서 세기조절방사선치료에서는 2,000 cGy 이상이 9.5%였으며, 삼차원입체조형치료에서는 17.5%였고, 왼쪽 대퇴골두부에 대해서 세기조절방사선치료에서는 2,000 cGy 이상이 10.6%였으며, 삼차원입체조형치료에서는 18.3%을 나타내었다. 삼차원입체조형치료와 세기조절방사선치료의 비교에서 세기조절방사선치료가 삼차원입체조형치료에 비해 PTV의 선량분포에서는 5%의 정도 선량분포의 이득이 있었으며, 직장 선량에 대해서는 5,000 cGy 이상 선량에서 29.3%의 감소가 있었고, 방광 선량에 대해서는 거의 비슷한 분포를 나타내었고, 오른쪽 대퇴골두부의 선량에서는 8.0%, 왼쪽 대퇴골두부의 선량에서는 7.7%의 선량 이득을 나타내었다.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1874-1879
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• 2024

Owing to strict radiation safety management in Korean nuclear power plants (NPPs), most radiation workers receive very low radiation doses, even lower than the annual dose limit for the general public. However, the occupational dose distribution indicates that some Korean NPP workers receive a relatively higher dose than the average dose. This inequity in radiation exposure could be reduced by providing customized radiation protection measures, such as dose constraints, to workers receiving relatively higher doses. In this study, dose normalization was performed to identify the highest radiation exposure work in Korean pressurized water reactors (PWRs). The results show that most of the occupational exposure in Korean PWRs occurs during the planned maintenance period. Finally, the three highest radiation exposure tasks in Korean PWRs were identified: nozzle dam installation and removal, eddy current testing, and man-way opening and closing.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.577-582
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• 1998

In nuclear power plant, it has been the important object to reduce the occupational radiation exposure (ORE). Recently, the optimization concept of management science has been studied to reduce the ORE in nuclear power plant. In optimization of the worker allocation, the collective dose, working time, individual dose, an total number of worker must be considered and their priority orders must be thought because the main constraint is necessary for determining the constraints variable of the radiological worker allocation problem. The ultimate object of this study s to look into the change of the optimal allocation of the radiological worker as priority order changes. In this study, the priority order is the characteristic of goal programming that is a kind of multi-objective linear programming. From a result of study using goal programming, the total number of worker and collective dose of worker have changed as the priority order has changed and the collective dose limit have played an important role in reducing the ORE.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1108-1115
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• 2024

Assuring physical security for Micro Modular Reactors (MMRs) will be key to their licensing. Economic constraints however require changes in how the security objectives are achieved for MMRs. A promising new approach is the so-called performance based (PB) approach wherein the regulator formally sets general security objectives and leaves it to the licensee to set their own specific acceptance criteria to meet those objectives. To implement the PB approach for MMRs, one performs a consequence-based analysis (CBA) whose objective is to study hypothetical malicious attacks on the facility, assuming that intruders take control of the facility and perform any technically possible action within a limited time before an offsite security force can respond. The scenario leading to the most severe radiological consequences is selected and studied to estimate the limiting impact on public health. The CBA estimates the total amount of radionuclides that would be released to the atmosphere in this hypothetical scenario to determine the total radiation dose to which the public would be exposed. The predicted radiation exposure dose is then compared to the regulatory dose limit for the site. This paper describes application of the CBA to four different MMRs technologies.

• Radiation Oncology Journal
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• 제30권1호
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• pp.27-35
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• 2012

Purpose: To evaluate the effect of common three photon energies (6-MV, 10-MV, and 15-MV) on intensity-modulated radiation therapy (IMRT) plans to treat prostate cancer patients. Materials and Methods: Twenty patients with prostate cancer treated locally to 81.0 Gy were retrospectively studied. 6-MV, 10-MV, and 15-MV IMRT plans for each patient were generated using suitable planning objectives, dose constraints, and 8-field setting. The plans were analyzed in terms of dose-volume histogram for the target coverage, dose conformity, organs at risk (OAR) sparing, and normal tissue integral dose. Results: Regardless of the energies chosen at the plans, the target coverage, conformity, and homogeneity of the plans were similar. However, there was a significant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV. The $V_{20Gy}$ of rectal wall with 6-MV, 10-MV, and 15-MV were 95.6%, 88.4%, and 89.4% while the mean dose to femoral heads were 31.7, 25.9, and 26.3 Gy, respectively. Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%. Overall, integral doses in mid and low dose regions in 6-MV plans were increased by up to 13%. Conclusion: In this study, 10-MV prostate IMRT plans showed better OAR sparing and less integral doses than the 6-MV. The biological and clinical significance of this finding remains to be determined afterward, considering neutron dose contribution.