• Nuclear Engineering and Technology
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• 제51권1호
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• pp.198-206
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• 2019

A new methodology to analyze the nuclear material accountability for pyroprocessing system is developed. The $Pu-to-^{244}Cm$ ratio quantification is one of the methods for Pu accountancy in pyroprocessing. However, an uncertainty in the $Pu-to-^{244}Cm$ ratio due to the non-uniform composition in used fuel assemblies can affect the accountancy of Pu. A random variable, LOPu, is developed to analyze the probability of detection for Pu diversion of hypothetical scenarios at a pyroprocessing facility considering the uncertainty in $Pu-to-^{244}Cm$ ratio estimation. The analysis is carried out by the hypothesis testing and the event tree method. The probability of detection for diversion of 8 kg Pu is found to be less than 95% if a large size granule consisting of small size particles gets sampled for measurements. To increase the probability of detection more than 95%, first, a new Material Balance Area (MBA) structure consisting of more number of Key Measurement Points (KMPs) is designed. This multiple KMP-measurement for the MBA shows the probability of detection for 8 kg Pu diversion is greater than 96%. Increasing the granule sample number from one to ten also shows the probability of detection is greater than 95% in the most ranges for granule and powder sizes.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2483-2488
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• 2023

Differential die-away analysis (DDAA) technology is a special nuclear material (SNM) active detection analysis technology. Be a nuclear material shielded or not, the technology can reveal the existence of nuclear materials by inducing fission from an external pulsed neutron source. In this paper, a detection model based on DDAA analysis technology was established by geant4 Monte Carlo simulation software, and the optimal sensitivity of the detection system is achieved by optimizing different configurations. After the geant4 simulation and optimization, a prototype was established, and experimental research was carried out. The result shows that the prototype can detect 200 g of ²³⁵U in a steel cylinder shield that's of 1.5 cm in inner diameter, 10 cm in thickness and 280 kg in weight.

• 대한방사선기술학회지:방사선기술과학
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• 제43권6호
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• pp.481-487
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• 2020

Radiation measurement technology has steadily improved and its usage is expanding in various industries such as nuclear medicine, security search, satellite, nondestructive testing, environmental industries and the domain of nuclear power plants (NPPs). Especially, the simultaneous measurements of gamma rays and neutrons can be even more critical for nuclear safety management of spent nuclear fuel and monitoring of the nuclear material. A semiconductor detector comprising cadmium, zinc, and tellurium (CZT) enables to detect gamma-rays due to the significant atomic weight of the elements via immediate neutron and gamma-ray detection. Semiconductor sensors might be used for nuclear safety management by monitoring nuclear materials and spent nuclear fuel with high spatial resolution as well as providing real-time measurements. We aim to introduce a portable nuclide-analysis device that enables the simultaneous measurements of neutrons and gamma rays using a CZT sensor. The detector has a high density and wide energy band gap, and thus exhibits highly sensitive physical characteristics and characteristics are required for performing neutron and gamma-ray detection. Portable nuclide-analysis device is used on NPP-decommissioning sites or the purpose of nuclear nonproliferation, it will rapidly detect the nuclear material and provide radioactive-material information. Eventually, portable nuclide-analysis device can reduce measurement time and economic costs by providing a basis for rational decision making.

• Journal of Radiation Protection and Research
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• 제35권4호
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• pp.167-171
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• 2010

Fixed radiation portal monitors (RPMs) deployed at border, seaport, airport and key traffic checkpoints have played an important role in preventing the illicit trafficking and transport of nuclear and radioactive materials. However, the RPM is usually large and heavy and can't easily be moved to different locations. These reasons motivate us to develop a mobile radiation detection system. The objective of this paper is to report our experience on developing the mobile radiation detection system for search and detection of nuclear and radioactive materials during road transport. Field tests to characterize the developed detection system were performed at various speeds and distances between the radioactive isotope (RI) transporting car and the measurement car. Results of measurements and detection limits of our system are described in this paper. The mobile radiation detection system developed should contribute to defending public's health and safety and the environment against nuclear and radiological terrorism by detecting nuclear or radioactive material hidden illegally in a vehicle.

• Journal of Radiation Protection and Research
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• 제34권3호
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• pp.115-120
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• 2009

1990년대 이후부터 현재까지 일련의 사건들은 - 1995년 러시아 국립공원에서 매설된 오염폭탄발견, 2001년 9/11 테러, 2003년 알카에다 오염폭탄 실험 증거 발견등 - 방사성물질 (본 논문에서 언급한 "방사성물질"은 "핵물질 사용후핵연료 방사성동위원소"를 말함)을 이용한 핵테러 및 방사능테러 (본 논문에서는 "핵테러 및 방사능테러"를 간단히 "핵테러/방사능테러"로 표시함)가 공상과학소설이 아닌 실제적으로 발생가능할 심각한 위협임을 보여준다. 이에 따라 세계는 새롭게 대두된 위협에 효과적으로 대응하기 위해 방사성물질에 대한 보안(security)과 물리적방호(physical protection)를 강화하고 방사성물질 불법거래 예방 및 대응체제를 구축하도록 요구하고 있다. 우리나라는 이러한 국제적 추세에 부응하기 위해, 관련 법 체제를 제 개정하고 국제협약 혹은 기구에 합의하거나 가입하였다. 본 논문에서는 핵테러/방사능테러 예방의 일환으로 방사성동위원소에 비해 상대적으로 복잡한 붕괴 과정을 가진 핵물질의 물리적 특성을 살펴보고, 현재 운영되고 있는 핵테러/방사능테러 탐지 장비들의 특성을 파악한다. 검토된 장비들의 특성과 함께 국외에서 국내로 불법 유입된 방사성물질이 목표 지점까지 도달되는 과정, 국내 지형적 특정 그리고 다중 방어적 개념을 고려하여 핵테러/방사능테러 탐지체계 구축 방안을 제안한다. 본 논문은 핵테러/방사능테러로부터 국민의 건강, 안전 그리고 환경을 보호하는데 중요한 기여를 할 것으로 판단된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.362.2-362
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• 2001

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.923-928
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• 2018

We developed a compact gamma camera based on a modified uniformly redundant array coded aperture to investigate the position of a $UO_2$ pellet emitting characteristic X-rays (98.4 keV) and ${\gamma}-rays$ (185.7 keV). Experiments using an only-mask method and an antimask subtractive method were conducted, and the maximum-likelihood expectation maximization algorithm was used for image reconstruction. The images obtained via the antimask subtractive method were compared with those obtained using the only-mask method with regard to the signal-to-noise ratio. The reconstructed images of the antimask subtractive method were superior. The reconstructed images of the characteristic X-rays and the ${\gamma}-rays$ were combined with the obtained image using the optical camera. The combined images showed the precise position of the $UO_2$ pellet. According to the self-absorption ratios of the nuclear material and the minimum number of effective events for image reconstruction, we estimated the minimum detection time depending on the amount of nuclear material.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2151-2161
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• 2020

The study presents a review of research advancements in the field of gamma radiation detection systems for emergency radiation monitoring, particularly two major sub-systems namely (i) the radiation detector and (ii) the detection platform - air-borne and ground-based. The dynamics and functional characteristics of modern radiation detector active materials are summarized and discussed. The capabilities of both ground-based and aerial vehicle platforms employed in gamma radiation monitoring are deliberated in depth.

• 비파괴검사학회지
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• 제29권3호
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• pp.256-263
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• 2009

After several PWSCCs were found in Bugey(France), Ringhals(Sweden), Tihange(Belgium), Oconee, Arkansas, Crystal Fever, Davis-Basse, VC Summer(U.S.A.), Thuruga(Japan), USNRC and PNNL started the research on PWSCC, that is, the PINC project. USNRC required KINS to participate in the PINC project in May 2005. KINS organized the Korean consortium at March 2006 and Pre-RRT for RVHP were performed for the preparation of PINC RRT. Through these preliminary RRT, Korea NDE teams can learn and develop the detection and sizing technique for RVHP dissimilar metal weld. These techniques are now being prepared in Korea and need to be utilized for the In-service inspection of the RVHP and BMI of Korea Nuclear Power Plants. PINC RRT mock-ups will be helpful to training.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1689-1696
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• 2020

In this study, we developed a fiber-optic humidity sensor (FOHS) system for the monitoring and detection of coolant leakage in nuclear power plants. The FOHS system includes an FOHS, a spectrometer, a halogen white-light source, and a Y-coupler. The FOHS is composed of a humidity-sensing material, a metal tube, a multi-mode plastic optical fiber, and a subminiature version A (SMA) fiber-optic connector. The humidity-sensing material is synthesized from a mixture of polyvinylidene fluoride (PVDF) in dimethyl sulfoxide (DMSO) and hydroxyethyl cellulose (HEC) in distilled water. We measured the optical intensity of the light signals reflected from the FOHS placed inside the humidity chamber with relative humidity (RH) variation from 40 to 95%. We found that the optical intensity of the sensing probe increased linearly with the RH. The reversibility and reproducibility of the FOHS were also evaluated.