Nuclear Decommissioning Research Articles

Nuclear Decommissioning and Sustainable Environment: Insights on Decontamination Processes

Nuclear energy accounts for ≈10% of global energy production, positioning it as a promising solution for achieving carbon neutrality amid escalating concerns over climate change. Nonetheless, the effective management of radioactive waste, which can remain hazardous for up to one hundred thousand years, presents considerable challenges that must be addressed to uphold public trust and safeguard environmental safety. This review outlines the fundamental stages of nuclear decommissioning including strategic planning, decontamination, dismantling, remediation, encapsulation, deregulation, and site reuse as a critical component of sustainable environmental practices. The review also highlights the significance of efficient decontamination processes in reducing waste generation. Various decontamination techniques, including mechanical, electromechanical, chemical, and advanced methods such as laser and plasma decontamination, are evaluated for their effectiveness and limitations. Moreover, the review emphasizes the need to enhance the recovery and recycling of ion exchange resin and potential radionuclides during decontamination processes to minimize waste and to address the depletion of potential radionuclide resources. Future research should prioritize the development of innovative techniques for decontamination and radioactive waste management, fostering sustainable decommissioning and supporting the ongoing development of nuclear energy in an environmentally responsible manner.

Organizational models for the decommissioning of nuclear power plants: Lessons from the United Kingdom and the United States

With nuclear reactor fleets continuously aging, the decommissioning of closed reactors is gaining increasing attention. In nuclear decommissioning, technical, organizational, and regulatory challenges lead to long project durations and cost escalations. This paper attempts to examine the organizational efficiencies in nuclear decommissioning by applying the framework of the "system good" analysis and assessments based on new institutional economics. It compares the former parent-body-organization model practiced in the United Kingdom with current approaches observed in the United States, highlighting potential gains and policy recommendations for private sector involvement in nuclear decommissioning. Inefficiencies experienced in the United Kingdom include regulatory issues, private actors' opportunism, and information asymmetries. Comparatively, the models observed in the United States show fewer such issues, but regulators should address potential profit-driven shortcuts and funding adequacy.

Characteristics of radioactive aerosols during the pre-decommission phase of the experimental shielding reactor

The decommissioning of nuclear reactors is a global concern, in part because of the generation of radioactive aerosols that can lead to internal radiation exposure. At present, radioactive aerosols generated during nuclear decommissioning have not been actively studied, and data collected from the actual decommissioning are limited. This paper presents a study of radioactive aerosols generated during the pre-decommission phase of an experimental shielding reactor. Among all the on-site operations, cutting resulted in the highest levels of radioactivity. Plasma arc cutting, in particular, had a maximum gross α and β radioactivity over 0.10 and 0.14 Bq/m3, respectively. Assumed AMAD (activity median aerodynamic diameter) values are employed to assess the impact of particle size on the internal exposure dose resulting from the inhalation of 137Cs aerosols. This assessment is based on the Human Respiratory Tract Model of International Commission on Radiological Protection. When cutting stainless steel by plasma arc, the internal exposure dose caused by 137Cs aerosols with an AMAD of 0.1 µm is estimated to be nearly four times as that of aerosols with an AMAD of 10 µm. Results show that the internal exposure dose is highly dependent on the AMAD, implying the importance of measuring size-related parameters of radioactive aerosols in the future nuclear decommissioning. This study has revealed some characteristics of radioactive aerosols released in decommissioning operations, which can serve as a valuable reference for controlling and removing aerosols during the decommissioning of nuclear facilities.

Uptake and coordination behaviour of uranyl on functionalised silica

The safe decommissioning of nuclear reactors is a complex process, requiring a range of technological options for it to be done effectively. It has become more important in recent years, with the substantial number of reactors entering the decommissioning phase. This paper details the use of functionalised silica for the recovery of uranium from aqueous hydrochloric acid solutions, a potential agent for the treatment of steel reactor components during nuclear reactor decommissioning. Silica functionalised with either phosphonic acid, bistriazine, or bistriazinylbipyridine ligands was shown to extract uranium, with the commercially available phosphonic acid functionality being the most effective. Extractions of 100 % were observed at [H+] ≤ 0.24 M, further the phosphonic acid functionality also had the highest loading capacity. Increasing [H+] has a suppressive effect on uranyl recovery, which was more pronounced for the in-house synthesized silica, and was attributed to protonation of the extracting moiety. Extended x-ray absorption fine structure spectroscopy was also used to determine the uranium coordination environments on the functionalised silica, and gain insights into the extraction mechanism. The uranyl cation was bound by two phosphonic acid groups, two bis-triazine groups, and one bistriazinylbipyridine group, respectively on each respective extractant. Uranyl was found to be penta-coordinate in the equatorial plane for all systems, with oxygen and/or chloride always present in the first coordination sphere. Evaluation of the mechanism indicated that uranyl must be loading onto the phosphonic acid functionality via multiple mechanisms, to both the phosphonic acid and silica related surface groups, although preferential binding of uranyl to the phosphonic acid groups was observed.

Ergonomic analysis in nuclear decommissioning: A comprehensive path planning strategy for workers well-being

Recent studies on path planning in nuclear decommissioning focus on efficient algorithms, often overlooking workers’ physical and cognitive well-being. However, there is a need to consider the effect of the paths recommended by algorithms on workers’ health to prevent work-related musculoskeletal disorders. This study introduces a computational dynamic body map tool designed to assess and monitor musculoskeletal disorders (MSDs) among workers in high-risk decommissioning environments. Utilizing color-coded body maps, the study identifies key ergonomic risk factors and their impact on different body parts. The strategy begins by identifying job tasks requiring ergonomic assessment, distilling the tasks into different activities and the time spent on each activity, and using the result to dynamically compute the average pain severity experienced by workers across different body parts. Subsequent body mapping, hazard surveys, and structured interviews are used to rank workplace risks and worker-specific risk factors. The major contribution of this work is the development of a computational dynamic tool to regularly track worker body maps regularly, ensuring optimal performance. To evaluate the proposed strategy, the study utilized data from a 35-response online MSD questionnaire for safety professionals. To demonstrate the methodology across diverse roles, 10 worker examples were analyzed, aligning with 5 key IAEA nuclear decommissioning categories. Analysis of the computational dynamic body map data reveals specific pain distributions among workers. The most severe pain occurs in the lower back (13.08 %), followed by the right wrist/hand (10 %), the right shoulder, the left elbow (8.46 % each), the left shoulder, the upper back (7.69 % each), the neck and the left wrist/hand (6.92 % each). The findings further reveal that the 36–45 years age category experiences the most pain. In addition, awkward posture was found in the study to be the most likely ergonomic risk factor affecting workers. The results show that incorporating ergonomics into path planning aids risk-informed decision-making for ergonomic interventions and continuous monitoring to maintain a safe and healthier workplace. Integrating the tool presented in this work with a conventional path-planning algorithm provides a comprehensive path-planning strategy for nuclear decommissioning.

Advancements in Remote Alpha Radiation Detection: Alpha-Induced Radio-Luminescence Imaging with Enhanced Ambient Light Suppression.

Heavy nuclides like uranium and their decay products are commonly found in nuclear industries and can pose a significant health risk to humans due to their alpha-emitting properties. Traditional alpha detectors require close contact with the contaminated surface, which can be time-consuming, labour-intensive, and put personnel at risk. Remote detection is urgently needed but very challenging. To this end, a candidate detection mechanism is alpha-induced radio-luminescence. This approach uses the emission of photons from radio-ionised excited nitrogen molecules to imply the presence of alpha emitters from a distance. Herein, the use of this phenomenon to remotely image various alpha emitters with unparalleled levels of sensitivity and spatial accuracy is demonstrated. Notably, the system detected a 29 kBq Am-241 source at a distance of 3 m within 10 min. Furthermore, it demonstrated the capability to discern a 29 kBq source positioned 7 cm away from a 3 MBq source at a 2 m distance. Additionally, a 'sandwich' filter structure is described that incorporates an absorptive filter between two interference filters to enhance the ambient light rejection. The testing of the system is described in different lighting environments, including room light and inside a glovebox. This method promises safer and more efficient alpha monitoring, with applications in nuclear forensics, waste management and decommissioning.

Toward Robotic Nuclear Decommissioning: Deep Learning-Based Object Classification and Pose Estimation from Partial-View Scans

This study introduces a novel framework for the robotic decommissioning of nuclear facilities, that focuses on object classification and six degrees of freedom pose estimation from partial-view three-dimensional (3-D) scan data. Addressing the challenge of precise robotic manipulation in environments where acquiring full-scan data is impractical, this framework leverages a deep neural network for initial pose estimation, subsequently refined by a modified iterative closest point algorithm. Our method demonstrates high accuracy in identifying scanned objects and estimating their poses from partial-view scans, validated through experiments with 3-D printed mock-ups. This advancement highlights the potential for significantly enhancing robotic automation in nuclear decommissioning and related fields.

Development of a Decommissioning Robot with a Simple Structure Capable of Traversing Steps Using Two Different Drive Systems

In response to the imperative need for robotic involvement in the decommissioning of the Fukushima Daiichi Nuclear Power Plant, a proactive initiative was undertaken. This initiative led to the organization of the “7th Decommissioning Creative Robot Contest,” in which pivotal challenges related to nuclear plant decommissioning were addressed. Recognizing inaccessible areas within a decommissioned plant, the primary objective of this study was to develop a remotely operated robot capable of executing decontamination tasks in such environments. Two distinct locomotion systems were designed: mecanum wheels and crawlers. The mecanum wheels, characterized by their ability to execute approximately 100 mm vertical movements, facilitated the robot to surmount obstacles, particularly by negotiating 100 mm steps by engaging the tracks. Simultaneously, to address decontamination tasks at elevated locations, a threefold expandable ladder truck system was integrated, augmenting the operational range of the robot. Participation in the contest provided a platform for showcasing the developed technologies and validating their practicality. Despite encountering challenges during competition, such as damage to one locomotion system, the other locomotion system can be used to reach the destination. Experience serves as a crucial means of verifying technological advancements. Issues such as malfunctions in the range of motion control due to faulty limit switch contacts and unexpected loads on the tire elevation motors were noted, which hindered the achievement of the anticipated results. Despite these drawbacks, the adopted structural design demonstrates notable advantages, particularly in terms of maneuverability. The combination of mecanum wheels and crawlers along with a ladder truck system demonstrated adaptability to various scenarios. This adaptability holds significant promise for future nuclear power plant decontamination applications. While the competition may not have yielded the desired outcome, the lessons learned and the verified practicality of the developed technologies reinforce their potential utility in addressing the future challenges of nuclear plant decommissioning.

Development and Application of Robotics for Decommissioning of Fukushima Daiichi NPS by IRID

The most challenging task in the decommissioning of the Fukushima Daiichi Nuclear Power Station is to retrieve molten and solidified fuel debris, including in reactor internals. The International Research Institute for Nuclear Decommissioning (IRID) has developed various robots that can investigate the interior of a primary containment vessel (PCV) to clarify where fuel debris has accumulated and how it has formed. The scenarios of each unit caused by the accident are different; therefore, IRID has developed robots to satisfy the requirements of each unit. The robots can be categorized into three types: non-submersible robots driving through air, submersible robots swimming underwater, and investigation robots with arms that can extend to enter the PCV. This review focuses on the technological development of robots based on their functionality. Most of the robotic technology is acquired and utilized based on the results of subsidy projects for countermeasures for decommissioning and contaminated water granted by the Japanese government.

Digital Mock-Ups for Nuclear Decommissioning: A Survey on Existing Simulation Tools for Industry Applications

The maturation of Virtual Reality software introduces new avenues of nuclear decommissioning research. Digital Mockups are an emerging technology which provide a virtual representation of the environment, objects or processes, supporting the whole lifecycle of product development and operations. This paper provides a survey on currently available simulation tools to design digital mock-ups required for safe remote decommissioning activities in the nuclear industry. The survey looks at eleven simulation tools; CoppeliaSim, Gazebo Classic, Gazebo (Ignition), Nvidia Omniverse Isaac Sim, WeBots, Choreonoid, AGX Dynamics, MORSE, VR4Robots, RoboDK, and Toia. Using the available documentation, the different capabilities of these software packages were assessed for their suitability to nuclear decommissioning, such as environment simulation, haptic interfaces, and general usability.

Laser cutting studies on 10–60 mm thick stainless steels with a short focus head for nuclear decommissioning

The cutting studies conducted on stainless steel plates with thicknesses of 10–60 mm using a short focus head and a high power fiber laser to evaluate application to nuclear decommissioning. The cutting performance was evaluated by determining the maximum cutting speed for each plate thickness and laser power. Both constant speed cutting and two-step speed cutting were experimentally performed. For a thickness of 10 mm, constant speed cutting had the better performance. On the other hand, two-step speed cutting achieved faster cutting for thicknesses greater than 10 mm. Even with a short focus head, cuts up to a thickness of 60 mm were achieved with a laser power of 6 kW, which corresponds to a cutting capability of ∼10 mm/kW. Kerf widths, which indicate the amount of secondary waste, were also measured in addition to maximum cutting speeds. Although there were some differences according to cutting conditions, all the kerf widths were narrow, within 2 mm.

Multiple scatter correction for single plane Compton camera imaging in nuclear decommissioning

AbstractThis paper focuses on the application of Compton cameras in nuclear decommissioning, aiming to develop efficient and affordable radiological characterization methods. Compton cameras offer advantages over traditional Anger cameras, including increased sensitivity and a larger field of view. We showcase the use of monolithic scintillation detectors in a Compton camera setup to compute two‐dimensional reconstructions of the source location of incident gamma rays. The presence of multiple scattering effects in the large, spatially non‐resolved detectors can lead to spatial artifacts in the reconstructed source activity. To address this, the paper proposes an extended forward model that accounts for double scattering interactions within a single detector element. Experimental and simulation results demonstrate the effectiveness of the proposed approach.

Cross-country survey on the decommissioning of commercial nuclear reactors: status, insights, and knowledge gaps

Abstract. In the past, nuclear decommissioning has often been overlooked in the literature but will gain increasing relevance amongst researchers and industry alike as more and more nuclear power plants reach the end of their respective operational lifetimes (Laraia, 2018; Schneider et al., 2022). Existing research has up until recently focused mostly on technical challenges and liability issues of nuclear decommissioning, while analyses of the organization, regulation, and financing across various countries remain limited. In this cross-country survey paper, we compare the differing approaches for nuclear decommissioning organization in France, Germany, Sweden, Switzerland, the United Kingdom (UK), and the United States based on detailed country reports (Wimmers et al., 2023). We find that while, in theory, the countries follow the same standards, the implementation of responsibilities for nuclear decommissioning, financial liability, and oversight can differ quite significantly. For example, France is the only country in our survey to have implemented a centralized ownership of its nuclear reactor fleet, while all other countries have multiple operators that necessitate a different regulatory approach. In terms of financing, we observe that most countries follow a single approach, while Germany and the UK have different financing schemes depending on the nuclear reactors to be decommissioned (e.g., the former GDR reactors in East Germany and the UK's non-PWR (pressurized water reactor) legacy fleet). Based on our analysis, we derive several insights that merit further research on the topic of nuclear decommissioning. For example, the interlinkage between ownership and nuclear decommissioning production should be of particular interest, as we determine potential organizational models (following the system approach coined by Beckers et al., 2012) emerging through corporate actors aiming at the monetization of swift decommissioning – a trend that cannot be observed where the state is in full control. We further find that only limited information on decommissioning costs exists. Reducing knowledge gaps in this regard would help further understand and potentially identify potential challenges in nuclear decommissioning in advance before more nuclear reactors are shut down. Further insight into nuclear decommissioning fund adequacy and liability issues might be required to avoid the transfer of financial liabilities from private operators to taxpayers. Other research gaps include an analysis of market-based decommissioning approaches and possible supply chain bottlenecks and the subsequent investigation of efficiency through economies of scale, the limitation of nuclear decommissioning production from limited access to nuclear waste management facilities, and the influence of regulation, e.g., the number of overseeing regulators, on the production. The paper is based on a joint DFG project between TU Berlin and the University of Basel, entitled “Best practices for decommissioning nuclear power plants”.

Nuclear decommissioning: project management and leadership

Abstract. Management and leadership for safety relate to managerial competencies necessary to develop, promote and sustain a safety culture and to set goals, lead others and manage knowledge and projects to enhance safety performance. The development of these competencies is needed to enrich and complement the predominant technical background and skills of engineers and/or managers involved in the nuclear sector and particularly in decommissioning and dismantling (D&D) projects. The recent recognition of the importance of managing for safety led the International Atomic Energy Agency (IAEA) to develop formal safety requirements that are now implemented by its member states. This includes the need to develop training and education for beginning- and mid-career managers with nuclear safety responsibilities and, considering the time frame of D&D projects, for future generations of managers. Training and education challenges are acute in all Instrument for Nuclear Safety Cooperation (INSC) and European countries, where managers need to develop knowledge and comprehensive safety-related competencies to run the D&D projects of nuclear facilities in a context where the generational change of managers in the nuclear field is happening fast. In 2016/2017 the IAEA and the European Commission (EC) developed a cooperative framework to jointly address a similar challenge related to operation and regulatory oversight of nuclear installations. The development of these projects was possible by funding from the European Union (EU) through its INSC instrument. The first project, led by the IAEA in 2017, was the development of a pilot school for safety leadership at the University Côte d'Azur (UCA), France. Encouraged by this success, the agency has since then developed the syllabus into a 2-week programme, still based on experiential learning, which is offered to IAEA member states who wish to organise sessions for their managers (regulatory bodies or industry). The second project, named ELSE, was operated by UCA and aimed to develop training to help managers acquire leadership for safety capabilities, which are key professional requirements in complex, high-risk and highly regulated sectors such as the nuclear sector. The originality of the ELSE project stemmed from its science-based approach, integrating the most recent findings of management and other social sciences. The dedicated ELSE training programme is composed of a massive online open course (MOOC), a 10 d of face-to-face training and an individually tutored project. Based on the success of these experiences, the EU decided to prolong these actions in the field of nuclear D&D, leading to the start-up, in 2023, of the Decommissioning Management and Leadership for Safety Education (DMaLSE) project. This project has also been entrusted to UCA, in partnership with SKEMA Business School, the Karlsruhe Institute of Technology (KIT) and Jacques Repussard Conseil. DMaLSE has two main objectives, namely to develop a science-based training programme for future D&D project managers and to extend the impact of the project through bachelor-degree-level on-site training for operators involved in D&D projects.

Deep borehole disposal as a potential solution for high-level waste (HLW) and spent nuclear fuel (SNF) in Norway – current status and a first generic safety assessment

Abstract. Deep borehole disposal (DBD) is currently being investigated as a potential solution for the disposal of the existing spent nuclear fuel (SNF) in Norway. Over the past years, BGE TECHNOLOGY GmbH (BGE TEC), together with the Finnish companies A-Insinöörit Oy (AINS Group), Mitta Oy and VTT Technical Research, has supported the Norwegian agency Norwegian Nuclear Decommissioning (NND) in the development of a deep borehole concept, including work on different technical details. At the end of 2022, the consortium was able to win a follow-up contract to further deepen and advance the work. For this second framework agreement, additional companies were added to further strengthen the expertise. The Geological Survey of Finland (GTK), Posiva Solutions Oy (PSOY) and Rambøll are now part of the new consortium group, which works under the acronym GeoReN (Geological Repositories for Norway). This paper provides an overview of the work carried out in the past for the deep borehole concept in Norway. In detail, this includes a basic description of the concept developed for the waste that originates from different institutions. Initial calculations indicate that a 69 BSK-R canister may be sufficient for the waste inventory to be considered. As the current conceptual borehole design provides the basis for most of the other work carried out, it will be presented and discussed within the paper. Furthermore, as part of the concept development, a first generic post-closure safety assessment was also performed for the DBD concept. The main results of the long-term calculations are discussed and presented in this paper as well. The main objectives of the generic safety assessment were the identification of critical parameters and assumptions for the model of the DBD repository and the performance of a first assessment of possible consequences of the potential post-closure release of radionuclides from the borehole. To be able to give a prediction at the present stage of the project, the assessment used conservative assumptions, models and data. The preliminary results for the normal evolution of the deep borehole repository indicate that highly mobile radionuclides, such as I-129, Cl-36, Ni-59 and Se-79, are the major dose contributors and that the expected potential radiological impact on future generations associated with these releases is extremely small. In addition, alternative scenarios have been assessed, which assume a hydraulic gradient leading to advective flow either upward through the borehole and surrounding excavation damaged zone (EDZ) or between certain parts of the borehole and the surface via a transmissive fracture system. Despite the pessimistic assumptions chosen for these scenarios, the maximum dose rates are significantly lower than the expected regulatory limit. However, it needs to be pointed that the present generic safety assessment is still on a conceptual level. With more detailed planning and updated information regarding the inventory, the geological environment, and the integrity and performance of the engineered barriers, repeated safety assessments will need to be performed to derive more substantiated results.

Prospects for growth and prosperity in West Cumbria: Nuclear decommissioning and regional economic adjustment

The objective of the paper is to trace out the effects of decommissioning of the Sellafield nuclear complex on the economy of West Cumbria. I seek to show how decommissioning expenditures are stimulating the formation of an agglomeration of advanced nuclear processing and engineering firms in the region and how this process is reinforced by a diverse array of emerging private and public institutions. With the aid of patent data, I indicate some possible pathways of industrial development in the region. I then proceed to examine how policy makers might enhance the developmental impacts of decommissioning especially in regard to measures focused on inter-firm network activities, training, and institutional infrastructures.

Методические подходы к обследованию хранилищ радиоактивных отходов уран-графитовых реакторов

The article presents methods and a general survey procedure for storage facilities with radioactive waste generated during the operation of uranium-graphite reactors. It presents the experience from the application of different survey methods and relevant findings. The paper describes the key areas for further improvement of the survey methods, including the results from the mock-up tests based on various methods applied for arranging penetrations in the radioactive waste volume providing access to the bottom waste layers. The approaches presented in the article can be adapted to explore other storage facility types arranged during nuclear decommissioning.

CLEANDEM, a Cyber physicaL Equipment for unmAnned Nuclear DEcommissioning Measurements

Human intervention is still required nowadays for most operations conducted during the Dismantling & Decommissioning (D&D) steps, which cover a wide range of radiological conditions: from the harsh initial conditions, nearly identical to when operating, to the final decommissioning steps where radioactivity has been removed. The goal of the three years EU-funded CLEANDEM project, led by CEA List, is to deliver a unique platform which will support the end-users’ operations, from the initial radiological assessment to the final characterization of the facility, while enabling their continuous monitoring during the D&D operations. Ten leading actors from four European countries’ nuclear industry and research, have joined their expertise and efforts in the CLEANDEM consortium to develop a mobile unmanned ground platform (UGV), equipped with upgraded highly-mature detection technologies for 3D-localized radiological measurements. These will complete the facilities’ available data into a 3D and fully detailed Digital Twin of the surveyed area, thus improving the planning and traceability of the D&D operations.

Development of a single method for direct measurement of multiple radionuclides using ICP-MS/MS

Simultaneous radionuclide measurement in a single procedure using tandem mass spectrometry contributing to rapid, cost-effective nuclear decommissioning and environmental monitoring.

The impact of uncertainty communication on emotional arousal and participation intention: the psychophysiological effects of uncertainties on experts

Research related to uncertainty communication remains contradictory, with some authors providing arguments of why it should be communicated, whereas others arguing that we should not do so. Practically, though, the decision on whether or not to openly communicate uncertainties remains on the level of experts of a certain field. That is why, in this article we analyze the psychophysiological reaction of experts when exposed to uncertainty as well as their willingness to participate in decision-making procedures about nuclear decommissioning (a salient issue, in which many uncertainties prevail) and using a sample of N = 134 participants which are employees of nuclear-related institutions in Belgium (divided in 2 groups: familiar and unfamiliar with decommissioning). By using the Uncertainty Reduction Theory (URT) and Uncertainty Management Theory (UMT), we study for the first time (1) whether communicating uncertainty influences participation intention directly and (2) whether this impact is mediated by emotional arousal. The method consists of an experimental design, combining a survey with psychophysiological measurement of emotional arousal. Results show that participation intention is directly influenced by attitudes toward participation, moral norm and time constraints, whereas familiarity with the topic of decommissioning influences participation intention indirectly, through attitude toward participation. Uncertainty communication, our main variable of interest, does not influence participation intention. It does influence, though, emotional arousal (concerning the public acceptance of the remaining radioactivity resulting from decommissioning), but it does not generate negative feelings such as anger or fear. Given that in the literature there is a debate on whether or not uncertainties should be communicated, the findings of this study imply that the concern that uncertainty communication leads to negative feelings should not be used as a reason not to communicate uncertainty anymore. Further implications and limitations are discussed in the article.