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J A Lawrence - One of the best experts on this subject based on the ideXlab platform.

  • a sensitivity study of the factors affecting the risks associated with the Disposal of spent nuclear fuel in a geological Disposal Facility in a clay environment
    Progress in Nuclear Energy, 2021
    Co-Authors: Ashley I Marsh, Freng Laurence Williams G Obe, J A Lawrence
    Abstract:

    Abstract The Disposal route for the UK's inventory of spent nuclear fuel has yet to be decided upon, however if the UK follows the approach taken by many nations, its spent nuclear fuel will be destined for geological Disposal. This paper provides a simplified, approach to the calculation of radiological risk posed to members of the public, associated with the Disposal of spent advanced gas-cooled reactor (AGR) nuclear fuel in a geological Disposal Facility (GDF) located in a hypothetical clay geological setting. Simulating the release of radionuclides at differing levels of complexity shall aid in the development of aspects of the design, construction, operation, decommissioning and post-closure phases of geological Disposal and the development of a safety case for geological Disposal. This paper presents a high-level, 1-D model built in GoldSim, to provide an initial indication of the radiological risks to the public, the nature of which would require further development into a complex total system model in order to facilitate risk evaluation supplementary to a safety case. The model was validated against benchmark calculations provided by Radioactive Waste Management Ltd. The base case calculations suggest that the predicted risks to the potential exposed groups are well below, approximately 2 orders, the recommended risk guidance level of 1 × 10−6 per year. A number of sensitivity studies were carried out to identify the importance of various factors that could influence the predicted risks. Sensitivity analysis indicated that the most influential sensitivities on the annual risk posed by geological Disposal were the depth and rate at which spent nuclear fuel dissolved in contact with groundwater. The pathways available for groundwater flow to the biosphere were also noted to significantly alter the peak risk observed; crucially almost all sensitivities did not increase the peak risk to within 1 order of magnitude below the recommended risk guidance level. Validation for a second hypothetical high strength rock geological setting resulted in higher projected predicted risks to the potential exposed groups although risk levels remained below the recommended risk guidance level. This suggests a clay environment may have favourable characteristics for the final Disposal of spent nuclear fuel compared to a high strength rock alternative.

  • the important role and performance of engineered barriers in a uk geological Disposal Facility for higher activity radioactive waste
    Progress in Nuclear Energy, 2021
    Co-Authors: Ashley I Marsh, Laurence G Williams, J A Lawrence
    Abstract:

    Abstract The effective management of radioactive waste is a necessary prerequisite to the use of nuclear energy. The UK's policy for the long-term management of higher activity radioactive waste (HAW), and potentially spent nuclear fuel (SNF), is Disposal in a deep underground geological Disposal Facility (GDF). A GDF will isolate HAW from mankind until the radioactivity has decayed to levels where any risk to future generations is acceptably low. It is likely, therefore, that a GDF will need to safely contain radioactive materials for hundreds of thousands of years. The necessary isolation will be provided by a combination of natural (geological) and engineered barriers. A multi-layered engineered barrier system will provide the defence-in-depth that is required to give the public confidence in the long-term performance of the GDF. This paper identifies the significant role each engineered barrier or “layer” plays in ensuring that long-lived radionuclides remain isolated from the biosphere and receptors within the vicinity of a GDF. Receptors include human and animal populations, and the natural environment. The paper also explores the characteristics and performance of a number of suitable candidate materials for use in the UK GDF engineered barriers. An indication of the lifetime of potential barriers under conditions pertinent to each of the UKs proposed geological settings is given. As the performance of the engineered barriers will be vital to the GDF post-closure safety case, several areas for further work are proposed.

W E Lee - One of the best experts on this subject based on the ideXlab platform.

  • thermal footprint of a geological Disposal Facility containing euro ganex wasteforms
    Progress in Nuclear Energy, 2020
    Co-Authors: Yunhao Hsieh, M J D Rushton, Paul C M Fossati, W E Lee
    Abstract:

    Abstract Synroc-Z is a new wasteform being developed to be specifically suited to waste from the advanced EURO-GANEX reprocessing route. This type of waste contains nuclides that release significant amounts of heat during their decay. Here, predictions for radiogenic heat generation from EURO-GANEX wasteforms based on Synroc-Z ceramic and R7T7 glass materials are presented. During reprocessing, any actinides present in the waste-stream are removed to leave only fission products. Simulation results are given demonstrating that, although initially classified as high level waste, the effects of decay mean the wasteforms effectively become intermediate level after 140 years of storage. Furthermore, many of the issues arising from alpha decay will be avoided. During the first 600 years, it is shown that the main source of self heating comes from the decay of Cs-137 and Sr-90. Our calculations show how the significant radiogenic heating by these wasteforms must be considered when defining package sizes and waste loadings. These effects are discussed for both ceramic and glass wasteforms and demonstrate that Synroc-Z provides more flexibility allowing larger packages even at higher waste loadings than R7T7.

  • chapter 19 nuclear waste Disposal
    An Introduction to Nuclear Waste Immobilisation, 2005
    Co-Authors: M I Ojovan, W E Lee
    Abstract:

    Publisher Summary Waste Disposal is the final step of waste management and ideally comprises placing radioactive waste in a dedicated Disposal Facility although discharging of effluents into the environment within permitted limits is also a Disposal option. Concepts for radioactive waste Disposal have developed considerably with time and great consideration is given to the necessary retention times and retention capacities for different types of waste resulting in much improved repositories and planned Disposal facilities. Disposal of radioactive wastes in a Disposal Facility is intended to isolate the waste both from human activity and from natural dynamic processes. Repositories for the storage/Disposal of radioactive waste generally rely on a multibarrier system to isolate the waste from the biosphere. This multibarrier system typically comprises the natural geological barrier provided by the host rock and an engineered barrier system (EBS). Furthermore, features and limitations of some Disposal/storage options are being discussed, followed by the transport of radionuclides. The flow rate/throughput of water through/around the repository is one of the most important parameters, which must be as low as possible.

Jin Beak Park - One of the best experts on this subject based on the ideXlab platform.

  • prediction of radionuclide inventory for the low and intermediate level radioactive waste Disposal Facility by the radioactive waste classification
    Journal of the Nuclear Fuel Cycle and Waste Technology, 2016
    Co-Authors: Kang Il Jung, Noh Gyeom Jeong, Young Pyo Moon, Mi Seon Jeong, Jin Beak Park
    Abstract:

    To meet nuclear regulatory requirements, more than 95% individual radionuclides in the low- and intermediate-level radioactive waste inventory have to be identified. In this study, the radionuclide inventory has been estimated by taking the long-term radioactive waste generation, the development plan of Disposal Facility, and the new radioactive waste classification into account. The state of radioactive waste cumulated from 2014 was analyzed for various radioactive sources and future prospects for predicting the long-term radioactive waste generation. The predicted radionuclide inventory results are expected to contribute to secure the development of waste Disposal Facility and to deploy the safety case for its long-term safety assessment.

  • safety assessment on the human intrusion scenarios of near surface Disposal Facility for low and very low level radioactive waste
    Journal of the Nuclear Fuel Cycle and Waste Technology, 2016
    Co-Authors: Sungwook Hong, Sangho Park, Jin Beak Park
    Abstract:

    The second-stage near surface Disposal Facility for low and very low level radioactive waste`s permanent Disposal is to be built. During the institutional control period, the inadvertent intrusion of the general public is limited. But after the institutional control period, the access to the general public is not restricted. Therefore human who has purpose of residence and resource exploration can intrude the Disposal Facility. In this case, radioactive effects to the intruder should be limited within regulatory dose limits. This study conducted the safety assessment of human intrusion on the second-stage surface Disposal Facility through drilling and post drilling scenario. Results of drilling and post drilling scenario were satisfied with regulatory dose limits. The result showed that post-drilling scenario was more significant than drilling scenario. According to the human intrusion time and behavior after the closure of the Facility, dominant radionuclide contributing to the intruder was different. Sensitivity analyses on the parameters about the human behavior were also satisfied with regulatory dose limits. Especially, manual redistribution factor was the most sensitive parameter on exposure dose. A loading plan of spent filter waste and dry active waste was more effective than a loading plan of spent filter waste and other wastes for the radiological point of view. These results can be expected to provide both robustness and defense in depth for the development of safety case further.

  • performance assessment of low and intermediate level radioactive waste Disposal Facility in korea by using complementary indicator case study with radionuclide flux
    Journal of the Nuclear Fuel Cycle and Waste Technology, 2015
    Co-Authors: Kang Il Jung, Mi Seon Jeong, Jin Beak Park
    Abstract:

    The use of complimentary indicators, other than radiation dose and risk, to assess the safety of radioactive waste Disposal has been discussed in a number of publications for providing the reasonable assurance of Disposal safety and convincing the public audience. In this study, the radionuclide flux was selected as performance indicator to appraise the performance of engineered barriers and natural barrier in the Wolsong low- and intermediate-level waste Disposal Facility. Radionuclide flux showing the retention capability by each compartment of the Disposal system is independent of assumptions in biosphere model and exposure pathways. The scenario considered as the normal scenario of Disposal Facility has been divided into intact or degraded silo concrete conditions. In the intact silo concrete, the radionuclide flux has been assessed with respect to the radionuclide retardation performance of each engineered barrier. In the degraded silo concrete, the radionuclide flux has been explored based on the performance degradation of engineered barriers and the relative significance of natural barrier quantitatively. The results can be used to optimally design the near-surface Disposal Facility being planned as the second project phase. In the future, additional complimentary indicators will be employed for strengthening the safety case for improving the public acceptance of low- and intermediate-level waste Disposal Facility.

  • preparation and management of the input data for the safety assessment of low and intermediate level radioactive waste Disposal Facility in korea
    Journal of the Nuclear Fuel Cycle and Waste Technology, 2014
    Co-Authors: Jin Beak Park, Hyunjoo Kim, Donghee Lee
    Abstract:

    (Received November 26, 2014 / Revised December 19, 2014 / Approved December 22, 2014)The systematic quality assurance activities on documents of the safety assessment are required for the safety case of the low- and intermediate-level radioactive waste Disposal Facility. In this paper, quality assurance system focused on the input data including the site characterization, groundwater flow, system design and monitoring are prepared and discussed. Rule for the input data selection is suggested and applied for the safety assessment which is based on the in-situ/experiment observations, final Facility design and waste pileup plan, engineered barrier, field monitoring, recent biosphere, and radio-nuclide inventory. The reduction of data uncertainty will be expected to contribute to the safety of Disposal Facility further.

  • statistical approach for derivation of quantitative acceptance criteria for radioactive wastes to near surface Disposal Facility
    Nuclear Engineering and Technology, 2003
    Co-Authors: Jin Beak Park, Joo-wan Park, Eun Yong Lee, Chang Lak Kim
    Abstract:

    For reference human intrusion scenarios constructed in previous study, a probabilistic safety assessment to derive the radionuclide concentration limits for the low- and intermediate- level radioactive waste Disposal Facility is conducted. Statistical approach by the Latin Hypercube Sampling method is introduced and new assumptions about the Disposal Facility system are examined and discussed. In our previous study of deterministic approach, the post construction scenarios appeared as most limiting scenario to derive the radionuclide concentration limits. Whereas, in this statistical approach, the post drilling and the post construction scenarios are mutually competing for the scenario selection according to which radionuclides are more important in safety assessment context. Introduction of new assumption shows that the post drilling scenario can play an important role as the limiting scenario instead of the post-construction scenario. When we compare the concentration limits between the previous and this study, concentrations of radionuclides such as Nb-94, Cs-137 and alpha-emitting radionuclides show elevated values than the case of the previous study. Remaining radionuclides such as Sr-90, Tc-99 I-129, Ni-59 and Ni-63 show lower values than the case of the previous study.

John C Whitehead - One of the best experts on this subject based on the ideXlab platform.

Peter A Groothuis - One of the best experts on this subject based on the ideXlab platform.

  • using contingent valuation to measure the compensation required to gain community acceptance of a lulu the case of a hazardous waste Disposal Facility
    Public Finance Review, 1998
    Co-Authors: Peter A Groothuis, George Van Houtven, John C Whitehead
    Abstract:

    The contingent valuation (CV) method was used to measure the compensation required for the siting of a hazardous waste Disposal Facility. Previous studies using the CV method were examined to determine the importance of subjective risk assessment. A CV survey was conducted to measure willingness to accept (WTA) for siting a hazardous waste Disposal Facility. Results suggested that CV can be used to estimate a reasonable measure of WTA and has great potential for assessing the compensation required to site a hazardous waste Disposal Facility.

  • using contingent valuation to measure the compensation required to gain community acceptance of a lulu the case of a hazardous waste Disposal Facility
    Public Finance Review, 1998
    Co-Authors: Peter A Groothuis, George Van Houtven, John C Whitehead
    Abstract:

    This article examines an application of the contingent valuation (CV) method to Abstract measure the compensation required for the siting of a hazardous waste Disposal Facility. First, the risk valuation literature on the siting of a hazardous waste Facility is discussed. In this section, the authors discuss past studies using contingent valuation techniques and the importance of subjective risk assessment. Second, a contingent valuation survey is performed to measure willingness to accept (WTA) using a dichotomous choice referendum framework. Using these data, the authors test for the internal consistency of the responses and calculate the WTA for siting a hazardous waste Disposal Facility. The authors conclude that CV can be used to estimate reasonable measures of WTA and is a potentially useful tool for assessing the compensation required to site a hazardous waste Disposal Facility.

  • the role of social distrust in risk benefit analysis a study of the siting of a hazardous waste Disposal Facility
    Journal of Risk and Uncertainty, 1997
    Co-Authors: Peter A Groothuis, Gail Miller
    Abstract:

    Distrust of social institutions is becoming an important component of risk communication and policy analysis. To assess the impact of social distrust on decision making, we examine the role of distrust of information sources on the willingness to accept a hazardous waste Disposal Facility in one's neighborhood. Using a prospective-reference utility model, distrust of information sources is analyzed a possible influence on individual choice in a risk-benefit tradeoff. Using contingent valuation survey data on the siting of a hazardous waste Disposal Facility, we find that respondents are particularly distrustful of both governmental officials and waste Disposal businesses. We find that social distrust increases the perceived risk of a Facility and influences the likelihood of accepting a referendum to site a hazardous waste Disposal Facility. The level of compensation offered in the contingent valuation scenario also is found to influence a respondent's risk perception.