• Nuclear Engineering and Technology
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• v.28 no.6
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• pp.594-601
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• 1996

To assure quality of safety critical software, software should be developed in accordance with software development procedures and rigorous software verification and validation should be performed. Software verification is the formal act of reviewing, testing or checking, and documenting whether software components comply with the specified requirements for a particular stage of the development phase [1]. New software verification methodology was developed and was applied to the Shutdown System No. 1 and 2(SDS1,2) for Wolsong 2, 3 and 4 nuclear power plants by Korea Atomic Energy Research Institute(KAERI) and Atomic Energy of Canada Limited(AECL) in order to satisfy new regulation requirements of Atomic Energy Control Board(AECB). Software verification methodology applied to SDS1 for Wolsong 2, 3 and 4 project will be described in this paper. Some errors were found by this methodology during the software development for SDS1 and were corrected by software designer. Output from Wolsong 2, 3 and 4 project have demonstrated that the use of this methodology results in a high quality, cost-effective product.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.1
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• pp.48-57
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• 2018

Configuration management (CM) is the process of identifying and documenting characteristics of plant structures, systems and components (SSCs), and of ensuring that changes to these characteristics are properly assessed, approved, implemented, verified and recorded. The purpose of this study is to examine regulation and technical standards developed under different concepts and level of depth for classification of nuclear SSCs as an essential prerequisite of the CM. In this context, main contents of currently adopted NSSC Notice 2016-10 are reviewed and compared with those in recently published ANSI/ANS 58.14 and IAEA SSG-30. The technical standards were prototypically used for classification of O-rings in two nuclear systems. It is found that ANSI/ANS 58.14 results in different categories taking into account specific features while IAEA SSG-30 leads to same categorization of the O-rings. Key findings will be summarized for Korean regulatory amendment in the future.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1099-1105
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• 2018

How to choose defaults in risk-informed regulations depends on the conservatism implicated in regulatory defaults. Without a universal agreement on the approaches dealing with the conservatism of defaults, however, the desirability of conservatism in regulatory risk analyses has long been controversial. The opponent views it as needlessly costly and irrational, and the proponent as a form of protection against possible omissions or underestimation of risks. Moreover, the inherent ambiguity of risk makes it difficult to set suitable defaults in terms of risk. This paper, the extension of the previous work [1], focuses on the effects of different levels of conservatism implicated in regulatory defaults on the estimates of risk. According to the postulated behaviors of regulated parties and the diversity of interests of regulators, in particular, various measures for evaluating the effect of conservatism in defaults are developed and their properties are explored. In addition, a simple decision model for setting regulatory defaults is formulated, based on the understanding of the effect of conservatism implicated in them. It can help decision makers evaluate the levels of safety likely to result from their regulatory policies.

• Journal of Soil and Groundwater Environment
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• v.23 no.4
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• pp.1-15
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• 2018

Despite of safety issues related to radiological hazards, 31 countries around the world are operating more than 450 nuclear power plants (NPPs). To operate NPPs safely, safety regulations from radiation protection organizations were developed and adopted in many countries. However, many cases of radionuclide releases at foreign NPPs have been reported. Almost all commercial NPPs routinely release radioactive materials to the surrounding environments as liquid and gas phases under control. These releases are called 'planned releases' which are planned, regularly monitored, and well documented. Meanwhile, the releases focused in this review, called 'unplanned releases', are neither planned nor monitored by regulatory and/or protection organizations. NPPs are generally composed of various structures, systems and components (SSCs) for safety. Among them, the SSCs near reactors are closely related to safety of NPPs, and typically fabricated to comply with stringent requirements. However, some non-safety related SSCs such as underground pipes may be constructed only according to commercial standards, causing the leakage of radioactive fluids usually containing tritium ($^3H$). This paper discusses SSCs of NPPs and introduces several cases of unplanned releases at foreign NPPs. The current regulation on the environmental radiological surveillance and assessment around the NPPs in South Korea are also examined.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.89-94
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• 2019

This study will examine the awareness of students in radiology who have applied the reorganization of the safety management system of frequent visitors according to the amendment of the Nuclear Safety Act. A survey was conducted on 175 students from the Department of Radiology at K University. 98.1% of the students in the second grade, 90.3% in the third grade, and 97.7% in the fourth grade were recognized as need to be classified as person with frequent access by the Nuclear Safety Act. Limiting the operation of radiation equipment in radiography practice is a regulation that violates students' right to learn, and it is necessary to enact an exception rule for learning so that the right to study is not violated.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.64-72
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• 2004

The dryer (ten per unit) are operating to remove tritium in PHWR(Pressurized Heavy Water Reactor). There are coming out heavy water adsorbent from operating the dryer (95 drums for ten year per unit) The amount of radioactivity of heavy water adsorbent almost exceed ninety times more than disposal limit-in-itself showed by The Ministry of Science and Technology. It has to be disposed whole radioactive waste products, however there are problems of increase at the expense of their permanent disposal. In this research, We have studied how to remove kinds of nuclear materials and amount of tritium with in heavy water adsorbent. As the result we could develop disposal equipment and apply it. D20 adsorbent have to contain below Gamma nuclide O.3Bq/g and tritium 100Bq/g "The Regulation for disposal of the radioactivity wastes" showed by The Ministry of Science and Technology. There fore. So as to remove amount of tritium and kinds of nuclear materials (DTO) we needed a equipment. Also we have studied how to remove effectively radioactivity with in Adsorbent. As cleaning heavy water adsorbent and drying on each condition (temperature for drying and hours for cleaning). Because there is something to return heavy water adsorbent by removing impurities within adsorbent when it is dried o high temperature. After operating, we have been applying this research to the way to dispose heavy water adsorbent. Through this we could reduce solid waste products and the expense of permanent disposal of radioactive waste products and also we could contribute nuclear power plant run safely. According to the result we could keep the best condition of radiation safety super vision and we could help people believe in safety with Radioactivity wastes control for harmony with Environment.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.581-583
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• 2005

The paper is final report for speed control upgrade and analysis report which recently performed on PWR NPP safety related EDG KHNP Ulchin NPP No.2 Unit. The upgraded system includes more beneficial function like as 'Slow start with starting ramp', 'Generator load sensing & control capability' and 'Emergency ramp during slow start'. This paper shows functional operation of slow start regime according to NRC regulatory guide which guide regulation to NPP safety related environment.

• Journal of radiological science and technology
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• v.41 no.5
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• pp.479-485
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• 2018

Radiologic technologists working at the second and third medical institutions are classified as radiation-related workers and radiation workers according to their working departments, and are subject to double regulation by the Ministry of Health and Welfare and the Nuclear Safety Commission. We will try to understand the system of dualization and to understand the investigation of recognition. The dualized system of radiation-related workers and radiation workers includes the difference in name and terminology, the effective dose limit, the maintenance education and training of radiologic technologists, the period of medical examination, the radiation zone, dose of the woman whose pregnancy is confirmed in radiologic technologists, the qualification criteria of the safety officer, and the period of the regular inspection of the radiological equipment. In the questionnaire survey on the dualization system, there were various items showing significant differences between the radiation-related workers and radiation workers Overall, the radiation workers were more aware of the radiation workers' education and related terms than the radiation-related workers.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.2
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• pp.49-54
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• 2017

Purpose The high-dose administration of I-131 has been standing for the basic therapy method of thyroid cancer. In korea, it is not necessary for patients to be hospitalized if the administration dose are under 1.2 GBq. However, if the dose are over 1.2 GBq, the patients should be stay in special ward with radiation shield. In such cases, the radioactivity level upon release should be under a dose of $70{\mu}Sv/hr$ at a distance of approx. 1m. This regulation bring the patients to stay for about 2 to 3 days in ward before the release. Materials and Methods Using the inpatients' release data of severance hospital, an inpatient-days were retrospectively calculated and compared with practical data and estimate the inpatient-days with the conditions of korea ($70{\mu}Sv/hr$), Japan ($30{\mu}Sv/hr$), germany ($3.5{\mu}Sv/hr$ at a distance of approx. 2 m), and other european countries. Results When a effective half-life of 15.4 was used, the expected inpatient-days were calculated as 2.15 days in the condition of Japanese regulation and 1.37 days in the condition of korean regulation. The practical inpatient-days of patients in Severance hospital were 1.32 days. Conclusion As ICRP 94 has been mentioned that the release of patients administrated with I-131 for the therapy should be carefully considered because each patients has different thyroid uptake rate and their conditions with family members after the release from the ward. Nonetheless, efforts to bring more aquate data which is for getting closer to the practical data should be continuously studied.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.657-658
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• 2004

The reactor protection system (RPS) of HANARO is a safety class system. The reactor is tripped by dropping four shut off rods (SOR). The SOR system consists of a SOR, hydraulic pump, hydraulic cylinder, solenoid valves and a power supply unit which has the AC coil contactor as a switching component. The hydraulic pump lifts up the SOR. The SOR drops by loss of the hydraulic pressure in the hydraulic circuit at the occurrence of voltage sags or interruptions. From this experiment, we knew that the magnitude of the voltage sag which impacts on this system is 70V, 500msec. The reactor regulation system (RRS) of HANARO has four CARs which are connected to the driver through a magnetic clutch. The CAR drops by loss of electromagnetic force of the magnetic clutch when the deeper voltage sags to lower than 10V, 500msec.