Decommissioning Of Nuclear Plants Research Articles

First quantitative constraints on chlorine 36 dry deposition velocities on grassland: Comparing measurements and modelling results

Once released into the atmosphere, radionuclide dry deposition represents a major transfer process. It can be accurately characterized by its deposition velocity. However, this parameter is poorly constrained for most radionuclides, including chlorine 36. Chlorine 36 is a radionuclide of cosmogenic and anthropogenic origin. It may be discharged into the environment as gases and/or particles during the decommissioning of nuclear plants and the recycling of nuclear fuels. In this study, chlorine 36 deposition velocities are, for the first time, experimentally determined on grass downwind from the Orano La-Hague plant. The atmospheric chlorine 36 measurements were on average 50 nBq.m−3 for the gaseous fraction and 19 nBq.m3 for the particulate fraction. To measure the chlorine 36 transferred from the atmosphere to the grass, a method was devised for extracting the chlorides contained in solid matrices. With this method, chlorides were extracted with a mean efficiency of 83%. Chlorine 36 concentrations in the grass were on average 4 μBq.g−1, suggesting fast uptake of atmospheric chlorine 36. The yielded 36Cl dry deposition velocities varied with the season and were between 1 × 10−3 and 6 × 10−3 m s−1. The chlorine 36 depositions were modelled by adapting the existing deposition models and based on meteorological and micro-meteorological data. The dry deposition velocities calculated by the model showed less than one order of magnitude of difference with those determined experimentally. The deposition fluxes calculated by the model showed that the atmospheric depositions were predominantly gaseous chlorine 36 (>97%). However, on remote sites, the particulate fraction could be larger and have a greater influence on dry deposition. As chlorine 36 is a highly soluble and bioavailable element, these results will enable a better study of its behaviour in the environment and a more accurate evaluation of its dosimetric impact.

A BIM-driven framework for integrating rules and regulations in the decommissioning of nuclear power plants

PurposeThe relatively low capital cost and contributions to mitigating global warming have favoured the continuous construction and operation of nuclear power plants (NPPs) across the world. One critical phase in the operation of nuclear plants for ensuring the safety and security of radioactive products and by-products is decommissioning. With the advent of digital twinning in the building information modelling (BIM) methodology, efficiency and safety can be improved from context-focus access to regulations pertaining to demolition of structures and the cleaning-up of radioactivity inherent in nuclear stations. The purpose of this study, therefore, is to propose a BIM-driven framework to achieve a more regulation-aware and safer decommissioning of nuclear power plants.Design/methodology/approachThe framework considers task requirements, and landscape and environmental factors in modelling demolition scenarios that characterise decommissioning processes. The framework integrates decommissioning rules/regulations in a BIM linked non-structured query system to model items and decommissioning tasks, which are implemented based on context-focussed retrieval of decommissioning rules and regulations. The concept’s efficacy is demonstrated using example cases of digitalised NPPs.FindingsThis approach contributes to enhancing improvements in nuclear plant decommissioning with potential for appropriate activity sequencing, risk reduction and ensuring safety.Originality/valueA BIM-driven framework hinged on querying non-structured databases to provide context-focussed access to nuclear rules and regulations and to aiding decommissioning is new.

Negative price spikes at power markets: the role of energy policy

In Germany, substantial drops in wholesale power prices have become a regular phenomenon. While such price drops have far-reaching implications for the functioning of the power market, their underlying determinants remain poorly understood. To fill this gap, we propose a Markov regime-switching model to investigate low-price events at the European Power Exchange. Our analysis focuses on the role of energy policies that promote renewable energies and have led to significant reductions of nuclear capacities after the Fukushima accident. We find that high electricity infeed from renewable sources increases negative price spike probabilities, while the decommissioning of nuclear plants under the Nuclear Moratorium had an opposing effect. Simulations of market outcomes under different energy policies indicate that reaching ambitious renewable energy targets increases the frequency of low-price events and compromises the financial viability of conventional generation units, while a nuclear phase-out or an increase in storage capacities mitigates these effects.

Negative Price Spikes at Power Markets: The Role of Energy Policy

In Germany, substantial drops in wholesale power prices have become a regular phenomenon. While such price drops have far-reaching implications for the functioning of the power market, their underlying determinants remain poorly understood. To fill this gap, we propose a Markov regime-switching model to investigate low-price events at the European Power Exchange. Our analysis focuses on the role of energy policies that promote renewable energies and have led to significant reductions of nuclear capacities after the Fukushima accident. We find that high electricity infeed from renewable sources increases negative price spike probabilities, while the decommissioning of nuclear plants under the Nuclear Moratorium had an opposing effect. Simulations of market outcomes under different energy policies indicate that reaching ambitious renewable energy targets increases the frequency of low-price events and compromises the financial viability of conventional generation units, while a nuclear phase-out or an increase in storage capacities mitigates these effects.

Negative Price Spikes at Power Markets: The Role of Energy Policy

In Germany, substantial drops in wholesale power prices have become a regular phenomenon. While such price drops have far-reaching implications for the functioning of the power market, their underlying determinants remain poorly understood. To fill this gap, we propose a Markov regime-switching model to investigate low-price events at the European Power Exchange. Our analysis focuses on the role of energy policies that promote renewable energies and have led to significant reductions of nuclear capacities after the Fukushima accident. We find that high electricity infeed from renewable sources increases negative price spike probabilities, while the decommissioning of nuclear plants under the Nuclear Moratorium had an opposing effect. Simulations of market outcomes under different energy policies indicate that reaching ambitious renewable energy targets increases the frequency of low-price events and compromises the financial viability of conventional generation units, while a nuclear phase-out or an increase in storage capacities mitigates these effects.

해체 콘크리트 폐기물 최종처분을 위한 시멘트 고화체 특성 평가

원자력 발전소와 연구시설의 해체 시 다량의 오염된 방사성 콘크리트 폐기물이 발생한다. 현재 국내에는 연구로 1, 2호기의 해체와 제염사업이 진행 중이며, 약 800여 드럼 (200 L)의 콘크리트 폐기물이 발생하였다. 이들 방사성 콘크리트 폐기물은 최종처분을 위해 200 L 드럼에 덩어리 크기의 콘크리트를 채우고, 시멘트 모르타르 형태로 제조한 입자상 폐기물로 빈 공간을 채우며 혼용 고정화 및 안정화하는 일련의 과정이 필요하다. 이에 본 연구에서는 콘크리트 폐기물, 물, 시멘트의 최적의 혼합비율을 찾고, 처분장 폐기물 인수기준에 준하기 위한 고화체의 특성을 평가하였다. 모르타르 유동도, 고화체 압축강도, 침출에 대한 안정성, 열 저항성 등의 인자에 따라 평가한 결과, 콘크리트 폐기물, 물, 시멘트의 배합비 75:15:10wt%에서평가인자 기준에 도달하였으며, 콘크리트 폐기물 75%에 미분말 콘크리트 폐기물을 최대 40wt%까지 포함시켜 시멘트 고화체를 제조한 경우에도 압축강도를 만족하였다. 입자의 충진 밀도의 증가로 scale-up실험에서는 75:10:15wt%의 배합비에서작업도 및 압축강도 범위를 만족하였다.