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All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Verifying Safeguards Declarations with INDEPTH: A Sensitivity Study

A series of ORIGEN calculations were used to simulate the irradiation and decay of a number of spent fuel assemblies. These simulations focused on variations in the irradiation history that achieved the same terminal burnup through a different set of cycle histories. Simulated NDA measurements were generated for each test case from the ORIGEN data. These simulated measurement types included relative gammas, absolute gammas, absolute gammas plus neutrons, and concentrations of a set of six isotopes commonly measured by NDA. The INDEPTH code was used to reconstruct the initial enrichment, cooling time, and burnup for each irradiation using each simulated measurement type. The results were then compared to the initial ORIGEN inputs to quantify the size of the errors induced by the variations in cycle histories. Errors were compared based on the underlying changes to the cycle history, as well as the data types used for the reconstructions.

Grogan, Brandon R↗
DOE OSTI2017

Viability of an Unattended Verification Station for UF6 Cylinders: Phase I Findings

In recent years, the International Atomic Energy Agency (IAEA) has pursued innovative techniques and an integrated suite of safeguards measures to address the verification challenges posed by the front end of the nuclear fuel cycle. Among the unattended instruments currently being explored by the IAEA is an Unattended Cylinder Verification Station (UCVS), which could provide automated, independent verification of the declared relative enrichment, 235U mass, total uranium mass, and identification for all declared uranium hexafluoride (UF6) cylinders in a facility (e.g., uranium enrichment plants and fuel fabrication plants). Under the auspices of the United States and European Commission Support Programs to the IAEA, a project was undertaken to assess the technical and practical viability of the UCVS concept. Phase I of the UCVS viability study was centered on a long-term field trial of a prototype UCVS system at the Westinghouse Fuel Fabrication Facility in South Carolina, USA. A key outcome of the study was a quantitative performance evaluation of two nondestructive assay (NDA) methods being considered for inclusion in a UCVS: Hybrid Enrichment Verification Array (HEVA), and Passive Neutron Enrichment Meter (PNEM). This paper will provide context for the UCVS and potential implementation concepts, a description of the UCVS prototype design, and an overview of the long-term field trial at a fuel fabrication facility. Selected field-trial results and interpretation are presented, including the performance of PNEM and HEVA for the verification of declared enrichment and 235U mass in over 200 “typical” Type 30B cylinders. Example results from a modeling study provide a preliminary assessment of sensitivity to material-substitution scenarios, for the as-fielded NDA methods.

Smith, Leon E.↗
DOE OSTI2015

EURATOM safeguards efforts in the development of spent fuel verification methods by non-destructive assay

The back end of the nuclear fuel cycle continues to develop. The European Commission, particularly the Nuclear Safeguards Directorate of the Directorate General for Energy, implements Euratom safeguards and needs to adapt to this situation. The verification methods for spent nuclear fuel, which EURATOM inspectors can use, require continuous improvement. Whereas the Euratom on-site laboratories provide accurate verification results for fuel undergoing reprocessing, the situation is different for spent fuel which is destined for final storage. In particular, new needs arise from the increasing number of cask loadings for interim dry storage and the advanced plans for the construction of encapsulation plants and geological repositories. Various scenarios present verification challenges. In this context, EURATOM Safeguards, often in cooperation with other stakeholders, is committed to further improvement of NDA methods for spent fuel verification. In this effort EURATOM plays various roles, ranging from definition of inspection needs to direct participation in development of measurement systems, including support of research in the framework of international agreements and via the EC Support Program to the IAEA. This paper presents recent progress in selected NDA methods. These methods have been conceived to satisfy different spent fuel verification needs, ranging from attribute testing to pin-level partial defect verification. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Self-Absorption Corrections for Plutonium Measurements With the Tomographic Gamma Scanner - 17325

The Tomographic Gamma Scanner (TGS) is a Non-Destructive Assay (NDA) instrument that combines high-resolution gamma spectroscopy with low spatial resolution three-dimensional image reconstruction in order to reduce bias and improve precision for measurements of drummed waste. The TGS technique is especially suited to measure containers with non-uniform source distributions and low-to me-dium-density heterogeneous matrices, compared with traditional NDA methods. Canberra recently built, installed, and commissioned a TGS system, intended primarily for the measurement of plutonium (Pu) bearing waste, at a European nu-clear fuel reprocessing facility. Pu assays using the TGS technique present technical challenges distinct from those typically encountered in traditional LLW applications. Among these is the need to apply corrections for self-absorption effects that occur on scales smaller than the TGS spatial resolution, and can compromise the assay result if not included in the TGS imaging methodology. We present a brief review of the Self Absorption Correction (SAC) technique, and discuss the complications involved with its application to the TGS methodology with examples from our recent experience. This work continues a Canberra history of further developing and refining a technique to solve emerging problems, having commercialized the original methodology by partnering with the research institution that pioneered it. The TGS and the SAC methodologies were originally developed by Los Alamos National Laboratory (LANL) and John Fleissner respectively, and this work illustrates how Canberra has implemented an advancement of these techniques in a new TGS system. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Use of Nuclear Divers in Decommissioning of Spent Fuel Pools/Ponds in the United Kingdom - 17431

Magnox Ltd. (Operated by the Cavendish Fluor Partnership) has initiated decommissioning of spent fuel pools/ponds utilizing divers. This decommissioning technique is being employed to disassemble and size reduce underwater equipment and furniture, as well as the collection of sludge and debris prior to draining of the pool. This technique has proven to be highly effective at reducing the radiological exposure to the workforce over previously implemented methods and is expected to significantly reduce overall decommissioning durations and costs. The decommissioning of the UK Nuclear Decommissioning Authority's (NDA) Dungeness A power station spent fuel ponds was initiated in 2015 to eliminate the mobile hazards and prepare the facilities for entry into a Care and Maintenance period. This dual reactor site has two spent fuel ponds each containing 1000 m{sup 3} of water, with the fuel removed since April 2012, which will utilize divers to remove solid wastes from the ponds prior to drain down. This technique has overcome many challenges to implementation including regulatory approval and high airborne contamination. The use of divers for decommissioning was a new technique for the Magnox Sites and required early engagement with the UK Office for Nuclear Regulation (ONR) and the Health and Safety Executive (HSE). The use of plasma arc cutting underwater required the pond area to be classified as an airborne contamination area. The implementation of local ventilation has controlled this hazard. The initial demonstration dives at Dungeness A were completed in April 2016 and the decommissioning dives are expected to be completed in March 2017. This is a substantial improvement to the project schedule and will allow the project completion 5 1/2 years ahead of the Licence Condition milestone. This technique is planned to be implemented at two further NDA Magnox power stations over the next three years. This paper provides the accomplishments and lessons learned to date. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

In Situ Disposal to Optimize Decommissioning Waste Management - 17455

Cavendish Fluor Partnership (CFP) is teaming with the UK government's Nuclear Decommissioning Authority (NDA) to explore opportunities for onsite disposal of structures and wastes from decommissioning of twelve Magnox nuclear sites. CFP is piloting implementation of draft guidance issued by the Environmental Agency (EA), Scottish Environmental Protection Agency (SEPA) and Natural Resources Wales (NRW) designed to optimise management of wastes generated in closing nuclear sites positioned across Scotland, Wales and England. Where it can be demonstrated to be the best overall solution for people and the environment, on-site / in situ disposal as an option for optimising waste management could save millions of pounds sterling in the overall costs for site closure as opposed to previous plans that required retrieval, packaging, transportation and offsite disposal of all radioactive wastes generated during site decommissioning. The UK government's Department for Business, Energy and Industrial Strategy (BEIS), NDA, and UK regulators are consulting with stakeholders on a proposal to amend legislation and enable better, more proportionate regulation of nuclear sites in the final stages of decommissioning and clean-up. Practical application of existing UK legislation typically means removing most, if not all, radioactive waste and residual contamination from the nuclear licensed site for disposal or management elsewhere, irrespective of any wider health and safety, social, environmental or economic considerations. Proposed changes to legislation would give greater weight to the environment agencies' guidance and provide for a more sustainable approach where optimization could include on-site/in situ disposal solutions and early opportunities to reuse land with appropriate regulatory oversight. Recent characterization activities at two reactor sites have identified areas of sub-grade low level contamination in structures and soil around used fuel ponds. CFP, a partnership of UK-based Cavendish Nuclear Limited and US-based Fluor Corporation, has initiated preliminary site modelling that indicates much of this material, including significant volumes of sub-grade structures would be conducive for in situ disposal under the new proposed guidance. Based on Fluor experience with similar decommissioning projects at US Department of Energy sites, CFP will look to leverage in situ disposal to optimise decommissioning waste management and consequently optimise overall facility decommissioning strategies. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Improvements to the operational efficiency of the Portsmouth 'Blue Box' Assay system - 15162

The 'Blue Box' in Building 326 at Portsmouth comprises a dual cargo container lined with high density polyethylene with 5% (elemental) boron that acts as a neutron shield. This construction provides a low environmental neutron background to support the capability to attain low values of minimal detectable activity (MDA). A Non-destructive Assay (NDA) measurement platform known as the Fluor B and W Portsmouth Slab Counter (FBPSC) is housed inside the Blue Box. This comprises four neutron slab detectors supported with an electronic system supplying power and associated signal processing. The system is operated by a laptop computer which has data acquisition and analysis capabilities. Each slab contains five {sup 3}He proportional counters embedded in polyethylene. The system is designed to measure the mass of U-235 in coolers from the Portsmouth site using passive neutron counting. The system was calibrated by taking measurements with {sup 252}Cf sources attached to various positions on the outside surfaces of a surrogate cooler. In addition, Monte-Carlo N-Particle (MCNP) simulations were performed to extend the baseline calibration for coolers of various sizes used in the gaseous-diffusion process. The basic principle of operation is to measure the total neutron emission from the item and determine the mass of {sup 235}U using the system efficiency (determined from MCNP calculations combined with the calibration measurements) combined with known isotopic information ({sup 235}U enrichment and U-235/U-234 ratio), assumed chemical composition, and gross cooler mass. The FBPSC analysis program calculates the mass of U-235 within the cooler being assayed, together with the associated Total Measurement Uncertainty (TMU). A background correction is performed that accounts for the measured environmental background with a cosmic-ray spallation correction (based on the cooler's gross weight). The software suite developed for the system also includes the capability to track and trend measurement control data in order to quickly identify conditions where the system has drifted outside of its quality control envelope. The MDA of the system has been determined to be less the 15 g of U-235 for count times that are typically less than 5 minutes (depending on the uranium isotopics). This is primarily the result of the low neutron background rate inside the Blue Box (approximately 3 times lower than at nearby locations outside the box). Additionally, various software features have been designed to yield optimum counting performance for the system including count time adjustment and interval filtering to reject statistical outliers that are usually associated with cosmic spallation events. The operation of the system has proven to be very efficient, with the short measurement time providing a high throughput rate of coolers through the Blue Box NDA system. Significant operational benefits and improved data traceability have been yielded compared to the previous measurement process, which involved operators taking measurement with counter/scalers and manually entering data into spreadsheets. As of August 2014, this system successfully measured all coolers required to support completion of a contractually-required Performance Milestone. There are approximately 1900 coolers available for measurement. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Minimum detectable activity for tomographic gamma scanning system - 15648

For any radiation measurement system, it is useful to explore and establish the detection limits and a minimum detectable activity (MDA) for the radionuclides of interest, even if the system is to be used at far higher values. The MDA serves as an important figure of merit, and often a system is optimized and configured so that it can meet the MDA requirements of a measurement campaign. The non-destructive assay (NDA) systems based on gamma ray analysis are no exception and well established conventions, such the Currie method, exist for estimating the detection limits and the MDA. However, the Tomographic Gamma Scanning (TGS) technique poses some challenges for the estimation of detection limits and MDAs. The TGS combines high resolution gamma ray spectrometry (HRGS) with low spatial resolution image reconstruction techniques. In non-imaging gamma ray based NDA techniques measured counts in a full energy peak can be used to estimate the activity of a radionuclide, independently of other counting trials. However, in the case of the TGS each 'view' is a full spectral grab (each a counting trial), and each scan consists of 150 spectral grabs in the transmission and emission scans per vertical layer of the item. The set of views in a complete scan are then used to solve for the radionuclide activities on a voxel by voxel basis, over 16 layers of a 10x10 voxel grid. Thus, the raw count data are not independent trials any more, but rather constitute input to a matrix solution for the emission image values at the various locations inside the item volume used in the reconstruction. So, the validity of the methods used to estimate MDA for an imaging technique such as TGS warrant a close scrutiny, because the pair-counting concept of Currie is not directly applicable. One can also raise questions as to whether the TGS, along with other image reconstruction techniques which heavily intertwine data, is a suitable method if one expects to measure samples whose activities are at or just above MDA levels. The paper examines methods used to estimate MDAs for a TGS system, and explores possible solutions that can be rigorously defended. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Characterization of Sr-90 Drums at the Hanford 618-10 Burial Ground - 16132

The 618-10 Burial Ground on the Hanford Reservation was an early trench waste site used for the disposal of waste from the 300 Area at Hanford. Much of this waste consisted of residues from evaluations of failed fuel as well as various process and separations studies associated with the Department of Energy (DOE) mission which were performed in the 300 Area between March 1954 and September 1963. Historical records indicated that there were also several drums which contained significant quantities of separated Sr-90. Cleanup of the 618-10 burial ground is covered under the Washington Closure Hanford (WCH) contract. Due to the proximity of the 618-10 site to the Columbia River, waste is being removed from the 618-10 site, stabilized, and disposed of into either the Environmental Restoration Disposal Facility (ERDF) if the containers are determined to be LLW or transferred to the Hanford Central Waste Complex (CWC) if the containers are suspected to be TRU waste. In order to determine the correct disposal path, Non Destructive Assay (NDA) must be performed on all of the containers excavated from the trenches. The NDA of these containers is performed using germanium gamma spectroscopy with an In Situ Object Counting System (ISOCS) and with a neutron slab counter. Occasional ISOCS spectra exhibited a characteristic Sr-90/Y-90 Bremsstrahlung continuum. In some cases there were measurable gammas present, however in other cases only the Bremsstrahlung continuum was present. Typically Sr-90 is correlated to Cs-137 as they are normally produced in approximately a 1:1 ratio during the fission process. For some of these drums there was no Cs-137 detectable and therefore no way to quantify the Sr-90. Due to concerns about providing a reasonable and conservative nuclide inventory it was decided to evaluate a technique to utilize data from the Bremsstrahlung continuum to quantify the Sr-90 activity in these drums. The development of the technique combined MCNP modeling and comparison of measured gammas to the continuum for a well-defined waste stream. The final result showed reasonable correlation to the expected scaling factors for many drums, while also providing a reasonable measured value for drums with significantly enhanced Sr-90 concentrations. Ultimately all drums were demonstrated to be within the ERDF waste acceptance criteria. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Managing Low-Level Waste at Dounreay - 16269

Dounreay Site Restoration Limited (DSRL) is the site licence company responsible for the clean-up and demolition of Britain's former centre of fast reactor research and development. The Dounreay site requires facilities to dispose of up to 175,000 cubic metres of low level waste (LLW) that has been and will continue to be generated during the decommissioning and restoration of the site. In May 2014, construction of two new vaults for the disposal of LLW at Dounreay was completed, including the necessary roads, infrastructures and services, followed by an encapsulation plant in September 2014. The vaults are located immediately to the northeast of the Dounreay licensed site, on NDA-owned land. The facilities are for disposal of the solid LLW generated at Dounreay and the adjacent Vulcan site only. In 2004, following consultation with stakeholders and members of the public, Dounreay issued the 'Best Practicable Environmental Option (BPEO) Report' on the management of Dounreay LLW. This report assessed potential management options for LLW against a range of criteria, including technical, environmental, cost, health and safety issues. The study was conducted in line with best practice and involved consultation with a range of people, including the local community and organisations with an interest in radioactive waste management. The recommendations and conclusions from the study provided the basis for the 'Dounreay Solid LLW Overall Strategy', which was published in March 2005. A fundamental component of this strategy was the development of new below-ground disposal vaults for LLW at Dounreay. Siting the vaults on land at Dounreay avoids any need to transport the LLW away from Dounreay on public roads. Disposal at Dounreay therefore satisfies the proximity principle of managing the waste at source. Disposal at Dounreay is also consistent with UK Government Policy on LLW management, the Scottish Government's Radioactive Waste Management Policy and the Nuclear Decommissioning Authority's (NDA's) strategy on management of LLW from the UK nuclear industry. A planning application was initially lodged with the Highland Council in June 2006. The period for the determination of this application was extended to allow the Scottish Environment Protection Agency (SEPA) sufficient time to assess fully the supporting Environmental Safety Case (ESC). The planning application was re-activated in May 2008, and planning permission was granted by Highland Council in April 2009. The planning permission included 26 conditions on DSRL, covering a wide range of environmental issues such as construction noise/dust, traffic, visual impact and also a condition to develop a community fund aimed at socio-economic development of the area around the Dounreay site. After undertaking the necessary detailed design work, construction of the phase one vaults commenced in November 2011 by principal contractor, Graham Construction. Work was undertaken on both vaults simultaneously, excavating around 243,000 m{sup 3} of rock. When excavation was complete, steel reinforcement was placed and concrete poured to construct the floor slabs. This was followed by the construction of the reinforced walls and then the installation of the steel support structure and materials that form the roof. Mechanical and electrical installation then followed, in parallel with the construction of the vault apron, ramps and access roads. A pumping system and control building was also constructed to remove groundwater from around the vaults to allow the vaults to be kept dry while they are being filled with waste. A layer of excavated material, approximately 3 m thick, was placed across the existing ground surface between the vaults and the coast, to ensure the water table lies well below the new ground surface after closure of the vaults, and that any future trace contaminated groundwater flows out to the sea rather than to the soil zone. This layer is referred to in project documents as the 'enhanced geosphere'. After disposals are completed and the vaults are closed, this layer will be joined to the capping over the vaults so that the ensemble merges visually with the surrounding landscape. The original vegetation and soil mix will be returned as far as is practicable. An encapsulation plant has been constructed to fill the LLW containers with grout prior to disposal in the vault, similar to the process used at the national Low-Level Waste Repository facility (LLWR), near Drigg in Cumbria. The plant has the capacity to grout up to four containers per day. The grout fills voids in the container and helps provide chemical conditions in the vault that limit the release of radionuclides in the far future, after the vault has been penetrated by groundwater. On April 24 2015, active commissioning began at the Encapsulation Plant and LLW Vaults. Half-height ISO containers packed with low level waste are currently being filled with grout and disposed of in the LLW Vault. Also packaged Demolition Low Level Waste (DLLW) is being processed and disposed of in the Demolition Low Level Waste Vault. To date over 2500 packages of DLLW and 70 containers LLW have been disposed of. Completion of construction and the start of operating the Phase One vaults and encapsulation plant are fundamental to the successful and efficient decommissioning of the Dounreay site, upon which many millions of pounds of investment and hundreds of jobs rely.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Regulation of the Shutdown Defueling and Decommissioning Reactors in the United Kingdom - 16576

Nuclear policy, including for decommissioning, in the United Kingdom is set by the UK Government. The Nuclear Decommissioning Authority, NDA, is responsible for managing the clean-up of the UK's nuclear legacy which includes the first generation of Magnox power stations. Magnox Ltd (MXL), owned by Cavendish Fluor Partnership, is the licensee and the management and operations contractor responsible for ten Magnox reactor sites and two restoration sites in the UK, working for the sites' owner, NDA. The work of the company is diverse covering electricity generation at Wylfa (until December 2015), defueling, and preparation for an interim end state, known as Care and Maintenance (C and M) which will precede the final site clearance. The C and M phase is expected to last over 75 years during which the sites are maintained in a passively safe and secure state while radiation levels are left to decay naturally. Preparations for this phase include removing fuel from the reactors and storage ponds; retrieving intermediate level waste from current stores and treating it or converting it to forms suitable for long-term storage or disposal and making sure of the integrity of critical safety systems of the de-fuelled reactors. The Decommissioning, Fuel and Waste programme within the Office for Nuclear Regulation, ONR, regulates nuclear safety in the 12 Magnox nuclear licensed sites. ONR works with the environmental regulators who are responsible for environmental protection on nuclear sites. The focus of this paper is the regulation of nuclear safety by ONR across the Magnox sites and the interactions with nuclear security and the environmental aspects required to achieve effective, proportionate and efficient regulation of these sites in the UK. ONR's strategy for regulating the Magnox defueling and decommissioning sites is focused on enabling the licensee to complete the initial stages of decommissioning and reduce the nuclear and radioactive hazards on its sites. To this effect, ONR's revised inspection guidance is centred on inspecting the (remaining) important systems for safety identified in the safety cases. Other interventions focus on engaging with the licensee on safety significant decommissioning projects to gain evidence of the licensee's readiness prior to and during these activities rather than formal assessment of the associated safety cases. In light of reduced hazards and risks across the de-fueled and decommissioning Magnox reactors, ONR's revised regulatory expectation regarding evolution of emergency arrangements during decommissioning is based on key transition points that follow electricity generation. Implementation of these revised strategies as well as organisational restructuring within the team responsible for regulation of the Magnox fleet has resulted in improved efficiency and consistency in regulatory approach whilst securing the required safety standards in managing decommissioning activities. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

The Magnox Clean-Up Programme - Integrating and Making Best Use of the Supply Chain - 16603

In 2010, the UK Nuclear Decommissioning Authority (NDA) secured a funding settlement of British Pounds 2.5 Bn from the Government for the period to 2015 for the Magnox Care and Maintenance programme. This settlement was a reflection of the importance placed on discharging the decommissioning liability associated with the UK's first generation Magnox reactors. It also reflected the NDA's confidence in the Magnox Optimised Decommissioning Plan (MODP), which aimed to accelerate entry into Care and Maintenance and reduce the Magnox decommissioning liability by British Pounds 1.2 Bn. Despite the settlement, huge challenges remained if the MODP was to be delivered within the funding envelope. Essentially, the supply chain had to be able to participate in the delivery of the MODP and make the investment in skills and techniques required to minimise the threats and uncertainties remaining in the Programme. The Magnox Commercial and Supply Chain Strategy was, therefore, an integral part of the MODP. At the highest level, the Strategy involved: - Classifying and segregating procurements by risk and value - Moving the contracting philosophy from risk transfer to risk management - Focusing on relationships and results rather than activities and processes By aligning the supply chain to the MODP, Magnox was able to better organise itself to deliver against the MODP, to act on feedback from suppliers and enable a culture of 'Lead and Learn' to take root. Using feedback and learning from other organisations and applying these to contract management approaches improved project outcomes. In particular, learning from previous experience of dealing with Programme 'unknowns' increased the company's ability to control and improve on the overall Programme cost and schedule. The impact of the MODP was to reduce the Magnox baseline by over British Pounds 1.5 Bn and remove 34 reactor-years from the Care and Maintenance preparations period. This huge gain resulted from a range of technical, process and commercial improvements across the organisation. Perhaps the greatest achievement of the MODP and its supply chain strategy was to quantify and stabilise the Magnox Life-cycle scope and cost and enable the successful competition and transfer of the Management and Operating (M and O) contract in 2014 and lay the foundations for further cost-savings to the UK taxpayer. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Chute Silo ILW Project Berkeley - 16649

Magnox, a Tier 1 Site Licensed Company (SLC), is the management and operations contractor responsible for the decommissioning of twelve of the Nuclear Decommissioning Authority's (NDA) nuclear sites in the UK. Aquila Nuclear Engineering is a specialist Tier 3, turnkey engineering company based in the UK, delivering mission critical engineering solutions to Europe's nuclear and nuclear medicine industries. Berkeley Nuclear Power Station, Berkeley, England started generating electricity in 1962, ceasing operation 27 years later in 1989. The Chute Silo ILW Project at this Reactor Site had been set up to retrieve irradiated control rods and charge chutes disposed of within a subterranean vault (silo). The project involved in-silo size reduction of waste in to 30-35 waste baskets. The waste basket was then to be retrieved via a pintle grab and hoist mechanism in to a Transfer Flask (through a silo and a Transfer Flask gamma gate). The Transfer Flask was then to transit along existing crane rails, out of the silo building and over the top of an Import/Export Facility. A Ductile Cast Iron Container (DCIC) was to be imported into Import/Export Facility and inspected/prepared to receipt the waste basket from the Transfer Flask. Once filled, the DCIC was then to be sealed and exported to an on-site storage facility. Due to an issue with the Magnox Tier 2 Framework holder in delivering a cost effective and viable solution for their Chute Silo ILW Retrieval Project, Magnox took the ground breaking decision to 'self-perform'. This involved dividing the larger project into several smaller packages. Two of these packages - for the shielded Transfer Flask and the Import/Export facility - were put out for competitive tendering directly to the Tier 3 Supply Chain. The work completed by the Tier 2 Company was shared with the Tier 3's, but Magnox expressly requested the Tier 2 proposals were scrutinised and that far more cost effective, robust and simpler solutions were provided for within the Tier 3 Tenders. Aquila won both work packages and delivered them with significant and demonstrable cost savings, on time and under budget. This was achieved by the collaborative arrangements between Aquila and Magnox, the methodologies of both company's project teams and the innovation and 'fitness for purpose' of Aquila's design pragmatism. The original Tier 2 Framework holder's price to Magnox for the Chute Silo ILW Project was between UK Pounds 2-3 M. Aquila delivered the equivalent scope for under UK Pounds 1 M. Aquila's original programme was maintained despite the award of additional scope and (Magnox) delays on site. Aquila came under the original target price for each discrete phase of the project. The above was achieved because of: - the collaborative arrangements between Aquila and Magnox; - the methodologies of both company's project teams; - the design features put forward by Aquila (welcomed and adopted by Magnox). In 2014 Aquila Nuclear Engineering received formal recognition of its achievements on this project by winning an NDA Supply Chain Award for 'Best example of supplier 'going the extra mile''. Points highlighted in the award were: - improved customer focus, leading to stronger relationships - encouraging challenge and innovation - continuous suggestions for improvement - UK Pounds 1 million savings and three months programme reduction.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Regulation of the First British Power Reactor to Enter into an Extended Period of 'Care and Maintenance' - 18028

All eleven of the British first-generation Magnox nuclear power plants have now ceased operating and are in various stages of decommissioning. The Magnox reactors were graphite moderated, using carbon dioxide as the primary coolant. The reactor cores are contained in steel reactor pressure vessels, except for the last two stations which have pre-stressed concrete pressure vessels. All but two of the Magnox reactor stations have been completely de-fueled. The spent fuel removed has been despatched for reprocessing at Sellafield in the north-west of England. On behalf of the UK government the Nuclear Decommissioning Authority (NDA) is responsible for cleaning up the majority of the civil nuclear legacy. The current NDA decommissioning strategy is to prepare the Magnox reactor sites for an extended period of Care and Maintenance (C and M), during which quiescent safe storage will take place (also known as safe enclosure), whereby the cores and associated structures will accrue the benefits of radioactive decay over a period of decades. This will reduce the radiation doses to workers during final dismantling and site clearance. The two Magnox rector units at the Bradwell licensed nuclear site in the south-east of England are the first scheduled to enter this quiescent safe-storage period. This is planned to commence in the second-half of 2018, and is scheduled to last for around 70 years. The Office for Nuclear Regulation (ONR) is the independent regulatory body, responsible for enforcing safety and security requirements at nuclear installations in Great Britain (GB). This paper outlines the national strategic context and how ONR's regulatory regime is applied to nuclear power plant decommissioning. It addresses some of the specific challenges posed at Bradwell during the preparatory works for entry to C and M and how ONR has addressed these. It describes how this will culminate in a regulatory decision on the acceptability of the safety and security of the Bradwell site to enter this new stage of its life cycle. Over the last few years ONR has assessed and inspected various safety aspects of decommissioning, radioactive waste management and other preparations for Bradwell's entry into C and M. Some of the operator's proposals have provided challenges to ONR, particularly where there have been changes to established approaches taken at other sites, as the licensee seeks to minimise its costs. These have included how far to remove redundant structures, systems and components prior to C and M; how to define interim and end-states for fuel cooling ponds and other contaminated areas; and how to treat and store Intermediate Level Waste (ILW), for which there is no geological disposal facility yet available. ONR has begun its final assessment of safety and security justifications supplied by the site licensee, Magnox Ltd (ML). ONR is using its legal powers conferred to it under the site licence conditions to authorise this first-of-a-kind transition into a 70 year period of safe storage. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Combined Assay Systems for the Characterisation of Historical ILW at of the Dounreay Shaft and Silo-18140

In 1955 the Dounreay nuclear power development establishment was created on the northern coast of Scotland primarily to pursue the UK Government policy of developing Fast Breeder Reactor (FBR) technology. The site operated then by the United Kingdom Atomic Energy Authority (UKAEA) saw the development, test and operation of 3 nuclear reactors, two of them FBRs, alongside fabrication and reprocessing facilities for the FBR fuel elements. From the late 1950's until 1977 Intermediate Level radioactive Waste (ILW) generated on site was disposed of into a 65 m deep, 4.6 m diameter shaft. In January 1977, an explosion thought to be caused by hydrogen generated from sodium and potassium wastes reacting with water occurred in the upper part of the shaft, thus stopping any further waste disposal. A second ILW storage facility, the ILW-Silo, started operation in 1971 to deal with the increasing volume of intermediate level waste generated on site in the mid-1960's and continued receiving waste until 1998. The decommissioning of the Shaft and Silo facilities is a challenging engineering task due to the complexity and potential hazards linked with the retrieval and handling of historical waste. Following recovery it is intended to shred the majority of the waste and load it into 200-l assay drums. Sludges would be separated and solidified within a special annulus drum to make them suitable for assay. To support the decommissioning strategies put forward by Dounreay Site Restoration Limited (DSRL), Mirion Technologies Canberra UK Ltd have designed and completed the manufacture of a pair of combined non-destructive waste assay (NDA) systems. The two identical automated ILW counters are intended to provide a means to characterise the waste materials by performing active and passive neutron measurement as well as segmented high resolution gamma spectrometry (HRGS) of 200-l sacrificial waste drums. The active neutron technique is based on the Differential Die Away (DDA) technique using a pulsed Deuterium-Tritium neutron generator to interrogate fissile material present in the waste. The active neutron measurements support, as well as the passive neutron coincidence measurements, a matrix correction capability by use of an Add-a-Source mechanism. The publication will describe in broad lines the approach proposed by DSRL in the processing of the waste retrieved from both the Shaft and Silo facilities. It will also present a description of the overall design of the NDA counters, illustrating how the measurements to be performed will allow DSRL to safely characterise the retrieved waste materials. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

New Beginnings: Optimising Waste and End-state at UK Nuclear Sites to Enable Environmental Permit surrender (the GRR) - 20193

The decommissioning of nuclear sites involves the management of large volumes of radioactive waste, other conventional waste, and the clean-up of land and groundwater contamination. In the UK, the disposal of radioactive waste from nuclear sites is regulated by the Environment Agency (England), Natural Resources Wales (Wales) and the Scottish Environment Protection Agency (Scotland). All three environment agencies seek to make sure that the generation and disposal of radioactive waste is optimised: ensuring impacts to people are 'as low as reasonably achievable' (ALARA). With a large proportion of UK nuclear sites embarking on decommissioning, the environment agencies have collaboratively developed new guidance: the 'Management of radioactive waste from the decommissioning of nuclear sites: Guidance on the Requirements for Release from radioactive substances regulation' (referred to as the GRR)[1]. The environment agencies worked in liaison with the Office for Nuclear Regulation (ONR), the UK nuclear safety regulator, and the UK government body responsible, the Nuclear Decommissioning Authority (NDA). Prior to finalising the guidance, a 12 month trial was completed at three of the NDA's nuclear sites, enabling the environment agencies to test their draft GRR guidance against 'real world scenarios' and the challenge of incorporating its requirements into decommissioning plans. Experience gained during the trial was incorporated into the current version of the GRR, published in July 2018. The GRR represents the 'new beginning' of this paper's title because for the first time, the UK environmental regulators have expressed in detail their requirements for surrender of environmental permits for nuclear sites. The GRR provides a framework for a UK nuclear site to plan, assess and justify its management of radioactive waste and deliver through decommissioning, an optimal, environmentally safe and sustainable end-state. This paper will describe the requirements and technical standards within the GRR, the establishment of defensible clean-up criteria and the production of a Waste Management Plan (WMP), supported by a Site-Wide Environmental Safety Case (SWESC). It will describe the experience gleaned by operators and regulators during the trial and it will highlight current work by regulators to implement the new approach proportionately. Finally, this paper will look forward and outline planned amendments to legislation in the UK affecting nuclear sites that should enable the full benefits of the GRR to be realised in the future. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

A Dose Assessment Model for Radioactive Waste Exposed by Gully Erosion at West Valley - 20513

The Western New York Nuclear Service Center (WNYNSC), located approximately 48 km south of Buffalo, New York, is the site of a former nuclear fuel reprocessing and radioactive waste disposal facility. Spent nuclear fuel was processed there from 1966 to 1972, leaving behind radioactive and chemical wastes in two disposal areas and a waste tank farm. Site operations also resulted in releases of radioactivity to site soils, groundwater, and to surface waters draining the site. The New York State Energy Research and Development Authority (NYSERDA) and the U.S. Department of Energy (DOE) are collaborating in a process of decision making for decommissioning those facilities remaining at the WNYNSC following the completion of Phase 1 decommissioning. Neptune and Company, Inc. (Neptune) was contracted to develop a probabilistic performance assessment (PPA) computer model to assist the agencies in this process. The PPA Model includes a contaminant transport component focusing on the movement of contaminants within and among environmental media including groundwater and surface water transport, contaminant translocation by plants and animals, diffusion, and erosion. The model also includes evaluation of potential exposure and health effects for a Resident Farmer exposure scenario, where the Resident Farmer represents a critical group, described as that group of individuals reasonably expected to receive the greatest exposure to residual radioactivity for any applicable set of circumstances. The West Valley Site is located in the glaciated Allegheny Plateau region of western New York State. The waste reprocessing and disposal areas were constructed on a relatively fat area of plateau dissected by drainages of Buttermilk Creek, including Erdman Brook, Franks Creek, and Quarry Creek. An important aspect of the contaminant transport component of the PPA model is consideration of erosive processes such as slumping of the stream slopes and the advance of gullies from these streams. These erosion processes remove material from the plateau, growing the size of the creek valleys and making them wider and deeper. Of particular interest for the impact of erosion is radioactive waste contained in the Nuclear Regulatory Commission (NRC)-Licensed Disposal Area (NDA), the New York State-Licensed Disposal Area (SDA), and residual radiological inventory in the underground storage tanks at the Waste Tank Farm (WTF). The PPA Model is organized around geographically-defined facilities which were constructed upon the plateau, including the NDA, SDA, and WTF. Ongoing stream erosion processes will potentially transfer radioactive waste and residual inventory from these facilities to the ground surface on adjacent hillslope areas where erosion has breached the facility. Hence, it is important to evaluate the consequences of potential exposures to a Resident Farmer on the hillslopes below a breached facility. Two interrelated aspects of the dose assessment model related to hillslope exposure are discussed: 1) representation of the physical processes related to transport of radionuclides from facilities onto the hillslopes, and from the hillslopes into adjoining creeks where contaminated material migrates downstream with surface water and sediment, and; 2) adaptation of the activities associated with the Resident Farmer scenario to assess potential exposures to contamination in the hillslope areas. This discussion will cover the conceptual basis of the hillslope exposure and transport models, and also implementation in the PPA computer model. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

The Effect of Localized Pin Flux on Short-Term Gamma Intensities of Spent Fuel Assemblies

Nuclear reactor operation for electricity generation involves irradiation of a fuel assembly for an extended period of time until a certain burnup is achieved. To harness the full nuclear energy potential and flatten the flux around the core, fuel assemblies are shuffled to one or more different locations within the core. Post-irradiation practice typically involves storing the spent fuel assembly in a spent fuel pool. While in the spent fuel pool, aspects of the fuel assembly continue to evolve, particularly the isotopic concentration as nuclides decay. Numerous nondestructive assay (NDA) safeguards techniques exist and have been proposed for performing verification on spent fuel assemblies to ensure they have not been tampered with. Adigun et al. recently proposed measuring both the neutron and gamma signatures from spent fuel from discharge to final disposal, however, the research in only investigated the neutron part of this approach. In the conclusion, the authors caveated the need for the gamma results to make more certain conclusions about a spent fuel assembly, as a combination of the neutron and gamma NDA measurements will limit the range of possible initial enrichment and burnup combinations. This paper focuses on the production of the gamma source. It is important to understand the driving mechanisms behind the emissions signatures at shutdown and after long cooling time periods, to better determine the correlation between the measured passive gamma emission spectra and the gamma emissions per second of the assembly. The objective is to demonstrate how the effect of localized flux within a reactor affects the gamma emissions per second (or gamma intensity) present in an assembly at shutdown. This study examined the photons emitted from the nuclides present within the fuel assembly, and not the photons escaping from the fuel assembly. The latter point of transporting the photons present within the spent fuel assemblies to an appropriate detector will be addressed in a future paper. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗