• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.3
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• pp.191-198
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• 2014

Using results of groundwater flow system modeling for a hypothetical deep geological repository site, a distribution of groundwater flow rates at the disposal depth was analyzed and a method of applying this distribution to a safety assessment for a disposal of radioactive wastes was suggested. The distribution of groundwater flow rates was produced by hydraulic heads simulated from regional and local scale groundwater flow models for the hypothetical disposal site. The flow rates at the locations where deposition holes would be located were estimated. These rates were normalized by the maximum of the flow rates in order to probabilistically illustrate a possibility of canister failures at the deposition holes. From the normalized distribution, probabilistic expectations for mass discharges of radionuclides released from the canisters assumed to be failed were calculated and compared with those deterministically estimated under the assumption that the canisters at the same deposition holes were definitely failed. The suggested method can be contributed to constructing a methodology for safety assessment of a geological repository by reflecting natural conditions of a disposal site in more detail.

• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.285-293
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• 1994

The transport of radionuclides in a compacted bentonite is dominated by diffusion. Through-diffusion tests for iodide were performed to investigate the diffusion characteristics of anionic radionuclides in a domestic bentonite. The bentonite used was sampled from the southeastern area of Korea and the solution was synthetic groundwater spiked with a tracer of I -125(as Na$^{125}$ I). The dry densities of compacted bentonite were 1.2, 1.4, and 1.7 Mg/㎥. The apparent diffusion coefficients and the effective diffusion coefficients of the iodide decrease with increasing dry density. The values were from 3.80 to 7.12$\times$10$^{-11}$ $m^2$/s for the apparent diffusion coefficients and from 1.25 to 7.97$\times$10$^{-12}$ $m^2$/s for the effective diffusion coefficient, respectively. The experimental results also showed that the apparent diffusion coefficients depended on the pore structure of compacted bentonite and the effective diffusion coefficients were attributed to the pore structure and the effective porosity that represents the available pathway for the diffusional transport of iodide. The results obtained will be used as basic data for the safety assessment of a repository.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.1
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• pp.33-40
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• 2006

The characteristics of the aluminum waste melting and the distribution of the radioactive nuclides have been investigated for the estimation on the volume reduction and the decontamination of the aluminum wastes from the decommissioning of the TRIGA MARK it and III research reactors at the Korea Atomic Energy Research Institute(KAERI). The aluminum wastes were melted with the use of the fluxes such as flux $A:NaCl-KCl-Na_3AlF_6$, flux B:NaCl-NaF-KF, flux $C:CaF_2$, and flux $D:LiF-KCl-BaCl_2$ in the DC graphite arc furnace. For the assessment of the distribution of the radioactive nuclides during the melting of the aluminum, the aluminum materials were contaminated by the surrogate nuclides such as cobalt(Co), cesium(Cs) and strontium(Sr). The fluidity of aluminum melt was increased with the addition of the fluxes, which has slight difference according to the type of fluxes. The formation of the slag during the aluminum melting added the flux type C and D was larger than that with the flux A and B. The rate of the slag formation linearly increased with increasing the flux concentration. The results of the XRD analysis showed that the surrogate nuclide was transferred to the slag, which can be easily separated from the melt and then they combined with aluminum oxide to form a more stable compound. The distribution ratio of cobalt in ingot to that in slag was more than 40% at all types of fluxes. Since vapor pressures of cesium and strontium were higher than those that of the host metals at the melting temperature, their removal efficiency from the ingot phase to the slag and the dust phase was by up to 98%.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.1
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• pp.31-39
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• 2013

Nuclear fuel can be damaged under unexpected circumstances in a nuclear reactor. Fuel rod failure can be occurred due to debris fretting or excessive hydriding or PCI (Pellet-to-clad Interaction) etc. It is important to identify the causes of such failed fuel rods for the safe operation of nuclear power plants. If a fuel rod failure occurs during the operation of a nuclear power plant, the coolant water is contaminated by leaked fission products, and in some case the power level of the plant may be lowered or the operation stopped. In addition, all spent fuels must be transferred to a dry storage. But failed fuel can not be transferred to a dry storage. Therefore, the purpose of this study is to develop a system which is capable of inspecting whether the spent fuel in the storage pool is failed or not. The sipping technology is to analyze the leakage of fission products in state of gas and liquid. The failed fuel inspection system with gamma analyzer has successfully demonstrated that the system is enough to find the failed fuel at Wolsong plant.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.2
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• pp.115-122
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• 2010

In this study, the removal of Cs and Tc from a simulated fission products (FP) solution which were co-dissolved with U during the oxidative-dissolution of spent fuel in a mixed carbonate solution of $(Na_2CO_3-NaHCO_3)-H_2O_2$ was investigated by using a selective precipitation method. As Cs and Tc might cause an unstable behavior due to the high decay heat emission of Cs as well as the fast migration of Tc when disposed of underground, it is one of the important issues to removal them in views of the increase of disposal safety. The precipitation of Cs and Re (as a surrogate for Tc) was examined by introducing sodium tetraphenylborate (NaTPB) and tetraphenylphosponium chloride (TPPCl), respectively. Precipitation of Cs by NaTPB and that of Re by TPPCl were completed within 5 minutes. Their precipitation rates were not influenced so much by the temperature and stirring speed even if they were increased by up to $50^{\circ}C$ and 1,000 rpm. However, the pH of the solution was found to have a great influence on the precipitation with NaTPB and TPPCl. Since Mo tends to co-precipitate with Re at a lower pH, especially, it was effective that a selective precipitation of Re by TPPCl was carried out at pH of above 9 without co-precipitation of Mo and Re. Over 99% of Cs was precipitated when the ratio of [NaTPB]/[Cs]>1 and more than 99% of Re, likewise, was precipitated when the ratio of [TPPCl]/[Re]>1.

• 한국공간정보시스템학회:학술대회논문집
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• 2001.11a
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• pp.143-160
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• 2001

최근 들어 무선인터넷 및 모바일 컴퓨팅 기술의 급속한 발전과 함께 향후 그 수요가 폭발적으로 증대될 것으로 예상되는 분야가 위치기반서비스(LBS, Location Based Service) 기술이다. 이동통시산업이 발달한 미국 및 유럽의 선진국에서는 지난 수년에 걸쳐 지속적으로 축적되어 온 정보기술을 통하여 현재 수많은 LBS 관련 기술개발이 활발히 진행되고 있다. 1999년 미국의 FCC(미연방통신위원회)는 무선 E119 규칙을 제정하였는데, 이 규칙은 LBS를 주목하게 한 결정적인 계기가 되었다. FCC는 미국내의 망 사업자들이 2001년 10월까지 이동전화 사용자가 응급 호출(911)을 하였을 때 67%는 100M 이내의 위치오차로, 95%는 300M 이내의 위치오차로 응급호출자의 위치정보를 제공해야 한다는 규정을 제정했다. 이때부터 각종 관련 회사들이 생겨나기 시작했으며, 사람들이 LBS에 관심을 가지기 시작하였다. 국내에서도 이동통신사업자 및 IMT-2000 사업자를 중심으로 LBS 도입을 적극 준비하고 있는 상황이다. 그러나 위치정보라는 것은 오래 전부터 사람들이 알고있던 사항이다. 이미 GPS라는 것을 이용하여 국방분야, 환경분야, 교통 및 물류 분야에서 많이 활용되고 있었기 때문이다. 그런데 왜 같은 위치정보를 활용하는 분야인데 LBS는 이토록 많은 관심을 불러일으키는가? 그것에 대한 답변은 바로 위치정보가 이동통신망과 연결되면서 대중적이고 일반적인 서비스가 가능해졌기 때문이다. 특히, LBS는 GIS가 정보통신 기술과 융합되면서 앞으로 추구해야 할 차세대 정보기술 분야라는 점에서 그 의미는 더 크다고 할 수 있다. 평균(平均) 0.322였다. 그리고 RaA를 모핵종(母核種)으로 가정(假定)했을 때 각핵종간(各核種間)의 방사평형비(放射平衡比)는 대개 $C_1>C_2>C_3$인 것으로 나타났다. 여기서 $C_1,\;C_2$ 및 $C_3$는 각각 RaA, RaB 및 RaC의 농도(濃度)를 나타낸다.0cm 깊이에서는 Pythium균(菌)과 Fusarium균(菌)을 제외(除外)하고 모두 14일간(日間)에 사멸(死滅)하였다. 6. 최고(最高)에 달(達)했다가 최저(最低)에 이르는 온도(溫度)의 반복적(反復的)인 파동(波動)이 있는 것에서 없는 것보다 단시간(短時間)에 사멸(死滅)하였다. 이상(以上)의 결과(結果)에서 볼 때 하기고온기(夏期高溫期)의 재배(栽培) 휴한기(休閑期)에 PVC film을 사용(使用)하여 하우스를 밀폐(密閉)하거나 턴널을 만들어서 태양열(太陽熱)을 이용(利用)한 토양소독(土壤消毒)의 가능성(可能性)이 충분(充分)히 있는 것으로 생각된다.종합적(綜合的)으로 볼 때, diazinon 과 decamethrin의 처리(處理)는 포장(圃場)에서 벼멸구의 산란력(産卵力)과 성충수명을 증대(增大)시키고, 식이활동(食餌活動)을 촉진(促進)함으로서 벼멸구의 resurgence를 유발(誘發)하고 아울러 수도체(水稻體)의 hopperbun을 가속화시킬 가능성(可能性)이 있음을 알 수 있었다.는 점차 약하여 졌으나 catalase, invertase는 그 활성도가 일단 숙성중기에 높아졌다가 낮아졌다.n 이 pH 4.2이고 temperature는 $60^{\circ}C$이었다. 그리고

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.758-765
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• 2016

This study analyzed for the radioactive shielding wall, which shields the medical linear accelerator. This allows to evaluate the level of waste with respect to the shield wall, which accounts for more than half of the cost of dismantling later linac facility. In addition, by analyzing the waste processing method according we discuss the way to obtain the benefits in terms of dismantling cost. Results of the simulate, the amount sufficient to screen the amount of neutron radiation occurring in the shielding wall linac was measured. And neutron activation analysis results were analyzed nuclides more than about 20. This analysis was in excess of that, $^{24}Na$, $^{45}Ca$, $^{59}Fe$ nucleus paper deregulation concentration. The value is reduced is greater the deeper the depth of the shielding wall concentration. Based on this, three specific areas (E, F, G) was estimated to be impossible to landfill or recycling. The rest area was estimated to be buried or recycled if possible more than a predetermined depth.

• The Journal of the Korea Contents Association
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• v.17 no.9
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• pp.69-76
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• 2017

This study evaluated the activation of the shielding wall and the components around the accelerator by using the medical linear accelerator. We performed simulations for energy values of 20 MV with the operating time ranging from day 1 to 30 years, and linear accelerator head and shielding wall concrete were also evaluated. The results showed that neutrons in large quantities were analyzed using high energy around thetarget point where photons were formed. Based on the activation analysis with these results, radioactivity increased with an increase in operation time and activated nuclides usually start saturating in10 years. Furthermore, the general types of nuclides formed owingto the activation were Co-60, W-181, 185, 187, Na-24, Ca-45, Mn-54, 56, and Fe-55, 59.

• Journal of Radiation Protection and Research
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• v.18 no.1
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• pp.9-24
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• 1993

The time-dependent radioecological model applicable to Korean environment has been developed in order to assess the radiological consequences following the short-term deposition of radionuclides in an accident of nuclear power plant. Time-dependent radioactivity concentrations in foodstuffs can be estimated by the model called 'KORFOOD' as well as time-dependent and time-integrated ingestion doses. Three kinds of critical radionuclides and thirteen kinds of foodstuffs were considered in this model. Dynamic variation of radioactivities were simulated by considering several effects such as deposition, weathering and washout, resuspension, root uptake, translocation, leaching, senescence, intake and excretion of soil by animals, intake and excretion of feedstuffs by animals, etc. The input data to the KORFOOD are the time of the year when the deposition occurs, the kinds of radionuclides and foodstuffs for estimation. The time-dependent specific activities in rice and the ingestion doses due to the consumption of all considered foodstuffs were calculated with deposition time using agricultural data-base in Kori region. In order to validate results of KORFOOD, the calculated results were compared with those by a leading German model, ECOSYS-87. The comparison of results shows good agreements within a factor of ten.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.335-341
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• 2017

Cyclotron is a device that accelerates positrons or neutrons, and is used as a facility for making radioactive drugs having short half-lives. Such radioactive drugs are used for positron emission tomography (PET), which is a medical apparatus. In order to make radioactive drugs from a cyclotron, a nuclear reaction must occur between accelerated positrons and a target. After the reaction, unncessary neutrons are produced. In the present study, radioactivation generated from the collisions between the concrete shielding wall and the positrons and neutrons produced from the cyclotron is investigated. We tracked radioactivated radioactive isotopes by conducting experiments using FLUKA, a type of Monte Carlo simulation. The properties of the concrete shielding wall were comparatively analyzed using materials containing impurities at ppm level and materials that do not contain impurities. The generated radioactivated nuclear species were comparatively analyzed based on the exposure dose affecting human body as a criterion, through RESRAD-Build. The results of experiments showed that the material containing impurities produced a total of 14 radioactive isotopes, and $^{60}Co$(72.50%), $^{134}Cs$(16.75%), $^{54}Mn$(5.60%), $^{152}Eu$(4.08%), $^{154}Eu$(1.07%) accounted for 99.9% of the total dose according to the analysis having the exposure dose affecting human body as criterion. The $^{60}Co$ nuclear species showed the greatest risk of radiation exposure. The material that did not contain impurities produced a total of five nuclear species. Among the five nuclear species, 54Mn accounted for 99.9% of the exposure dose. There is a possibility that Cobalt can be generated by inducive nuclear reaction of positrons through the radioactivation process of $^{56}Fe$ instead of impurities. However, there was no radioactivation because only few positrons reached the concrete wall. The results of comparative analysis on exposure dose with respect to the presence of impurities indicated that the presence of impurities caused approximately 98% higher exposure dose. From this result, the main cause of radioactivation was identified as the small ppm-level amount of impurities.