Berkeley, United Kingdom
Berkeley, United Kingdom

Magnox Ltd is a nuclear decommissioning Site Licence Company controlled by Cavendish Fluor Partnership, its designated Parent Body Organisation . It operates under contract for the Nuclear Decommissioning Authority, a government body set up specifically to deal with the nuclear legacy under the Energy Act 2004.Magnox Ltd is responsible for the operation and decommissioning of ten Magnox nuclear power stations in the United Kingdom. The ten sites are Berkeley, Bradwell, Chapelcross, Dungeness A, Hinkley Point A, Hunterston A, Oldbury, Sizewell A, Trawsfynydd and Wylfa. All the sites have ceased production with the exception of Wylfa. On the 30th September 2014, the Office for Nuclear Regulation approved to extend the lifetime of Wylfa to December 2015.In addition, as part of the Trawsfynydd unit, Magnox Ltd operates a hydro-electric power station at Maentwrog.The only Magnox power station in the UK not managed by Magnox Ltd is Calder Hall, which is part of the Sellafield site and is controlled by another SLC, Sellafield Ltd. Wikipedia.

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Turner S.,Magnox Electric Plc | Wilmott S.,Magnox Electric Plc
Lecture Notes in Business Information Processing | Year: 2013

This paper outlines the legislative requirements for optimisation of radioactive wastes and provides a brief background to the history of the use of Multi-Attribute Decision Analysis (MADA) optioneering tools in Magnox Limited for the purposes of waste management decision-making and stakeholder engagement. The paper then outlines the challenges that traditional optioneering approaches presented Magnox as the Company moved towards decommissioning its fleet of nuclear power stations, and then describes the new assessment techniques that the authors developed in response to this challenge providing an open, transparent and proportionate approach to decision-making and periodic review of the decisions taken. © Springer-Verlag Berlin Heidelberg 2013.

Nobes T.S.,Sellafield Ltd | Murphy C.,Magnox Electric Plc
Proceedings of the International Instrumentation Symposium | Year: 2014

Magnox Ltd® and Sellafield Ltd® have both installed modern, commercial off the shelf, wireless instruments. This paper discusses the challenges and benefits.

Buckley D.,Magnox Electric Plc
Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation, ICEM | Year: 2011

Early in 2011 Oldbury Nuclear Power station in South West England applied to the Office of Nuclear Regulation (ONR) to de-license an area of over 30 hectares of licensed land. This is the largest area of licensed land in the UK to undergo this procedure. As part of the process the site prepared a safety case to support the submission to the ONR. Also there has been a requirement to do sampling and analysis to characterise the land and show that any radioactive contamination is below the criterion for de-licensing. This has been achieved through the successful application of the Data Quality Objective (DQO) process which enabled both site and regulators to agree on the quantity of samples and the degree of analysis. The ONR has now issued the variation to Oldbury in July 2011 de-licensing approximately 32 hectares of land from regulatory control. This Paper outlines the process including the decisions and criteria that have been applied to the Sampling and Analysis at Oldbury and the Treatment and Interpretation of the data. Copyright © 2011 by ASME.

Moskovic R.,Magnox Electric Plc
Nuclear Engineering and Design | Year: 2014

Magnox reactors employ pile grade A (PGA) graphite as a moderator. Reactor cores are constructed typically of twelve to thirteen layers of graphite bricks. Fuel channels (FC) are in the centre of all bricks and interstitial channels (IC) at the centre of the corners of every second set of four bricks. The reactor core is cooled by carbon dioxide, the temperature of graphite core increases from 250 C at the bottom to 360 C at the top of the core. The neutron dose increases progressively with the operating time of the reactor. The graphite core looses mass as a result of radiolytic oxidation. The process is dependent on both total energy deposition and temperature which correlates with core height. Fast neutron dose accumulates at the same rate as the total energy deposited and is readily available. The reduction of density of moderator graphite increases the porosity and in turn changes both the physical and mechanical properties of graphite. The mechanical properties and density of graphite are measured either on samples installed in the reactor prior to service or trepanned from graphite bricks. The data obtained on these samples are interrogated using probability modelling to establish trends with increasing service life. Results of the analyses are illustrated in the paper. PGA graphite is an aggregate of coarse needle coke filler particles within a matrix of fine coke flour particles mixed with pitch binder. The bricks are fabricated in the green condition by extrusion of dry calcinated coke impregnated with liquid pitch binder and then graphitized at 2800 C. This produces a polygranular aggregate with orthotropic properties. The strength properties of graphite are measured using different types of tests. The most commonly used tests involve bending, uniaxial and diametral compression. The initiation and propagation of cracks was investigated to improve understanding of strength behaviour. Cracking was examined on macro-scale using optical microscopy and on micro-scale using focused ion beam, FIB. In addition, digital image correlation was used to investigate the initiation of cracking. It was shown that highly localized strain regions are formed on the tensile surface of beams loaded in bending. One of the strained regions develops into a process zone which initiates cracking when reaching a length of 2-3 mm. Crack propagation then occurs rapidly along an irregular path. © 2013 Elsevier B.V.

Brook N.J.,Magnox Electric Plc
IET Conference Publications | Year: 2013

The article presents survey report covering all of the inspections and technical assessment report of the survey including other environmental monitoring and corrosion data .The reports will be used to support the long term reactor building safety cases and the future inspection regime.

Wilkinson J.,Keil Center | Rycraft H.,Magnox Electric Plc
Institution of Chemical Engineers Symposium Series | Year: 2014

Recent research carried out by the Keil Centre for Magnox Ltd focuses on organisational learning as part of an on-going nuclear research programme. While the research itself is not published outside the industry, Magnox is willing to share the main results as part of its commitment to sharing learning. This paper describes the main results of the literature review as applicable to the non-nuclear high hazard industries and discusses the main outcomes for organisational learning theory and practice. It is already widely recognised that organisations do not readily learn from incidents, particularly where organisational factors are involved as root or contributory causes. Although there are well-publicised repeat incidents such as the space shuttle disasters and BP's Texas City and Macondo incidents, the issue is widespread e.g. as seen through IChemE's own Loss Prevention case studies. This paper builds on the main outcomes of the Magnox research to show how organisations could start to learn more reliably from their own and others' incidents, and from a range of wider sources (beyond incidents). The nuclear industry has a range of learning practices through its mature Operational Experience Feedback (OEF) system but learning from wider sources has proved difficult, and even with the OEF arrangements, reliable learning to prevent repeat incidents can still be problematic. This paper aims to show what the main barriers to conventional incident learning are and how wider learning sources and methods may be developed. The paper includes a focus on organisational factors. These are particularly hard to identify reliably and tackle. They are often part of the 'organisational wallpaper' - 'The way things are round here' as opposed to 'The way we do things round here' the accepted strapline for safety culture. Recommendations for identifying and addressing these factors are also made. © IChemE.

Heard P.J.,University of Bristol | Wootton M.R.,Magnox Electric Plc | Moskovic R.,Magnox Electric Plc | Flewitt P.E.J.,University of Bristol
Journal of Nuclear Materials | Year: 2011

Pile grade A (PGA) graphite is used as a moderator in UK gas cooled nuclear reactors. This is a polygranular, aggregate material with quasi-brittle behaviour. When exposed to the service environment the material is subject to radiolytic oxidation that results in mass loss and an attendant increase in porosity. In the present work both unirradiated and irradiated small specimens of PGA graphite have been subjected to diametral compression. A novel trench-probe loading method is also described that allows micro-scale specimens prepared by focused ion beam milling to be fractured in a focused ion beam work station. This allows the fracture characteristics of selected regions of the graphite microstructure to be interrogated. The load-displacement and fracture characteristics of both the unirradiated and irradiated PGA graphite are compared and shown to be consistent with quasi-brittle behaviour. In addition, surface features consistent with elastically induced twins are observed associated with filler particles of the graphite. The results are discussed with respect to the quasi-brittle behaviour of this polygranular graphite. © 2011 Elsevier B.V. All rights reserved.

Moskovic R.,Magnox Electric Plc
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2012

Magnox reactors employ pile grade A (PGA) graphite as moderator. Reactor cores are typically constructed of twelve to thirteen layers of interlocking graphite bricks. Their temperature varies from 250°C at the bottom to 360°C at the top of the core. It serves a dual role as both the moderator and encasing the fuel in the channels. These are through the middle of the bricks and continuous through the core. The bricks are either octagonal or square in shape. A unit of eight brick of equal numbers of each shape has a single interstitial channel at the point where the corners of two octagonal and two square bricks meet. The interstitial channels are used for control rods, absorbers and canisters of graphite samples installed to replicate the service exposure of reactor bricks and to be used for measurements. The graphite loses mass during service due to radiolytic oxidation, by CO2 caused by energy deposition, mainly γ radiation. Neutron irradiation brings about hardening and dimensional change which decrease with the increasing distance from the bore to the outer surface of the brick. The gradient in the dimensional changes as well as thermal transients generate internal strains and in turn stresses. This paper reviews changes of some physical and mechanical properties of graphite during service and describes the cracking and fracture behavior of graphite. Statistical analysis of density showed that it decreases during the service with increasing neutron dose and decreasing reactor core height/temperature. Crack initiation involves a prior formation of a process zone. Copyright © 2012 by ASME.

Bertoncini C.,Magnox Electric Plc
Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation, ICEM | Year: 2013

Magnox reactors were the first generation of nuclear power stations built in the UK; ten sites in total, of which, nine had wet fuel routes with cooling ponds. Five ponds are currently in a decommissioning phase; this paper will focus primarily on Hunterston-A (HNA) Site and the central programme of work which governs its management. During its operation, the Cartridge Cooling Pond at HNA was used to receive the spent fuel discharged from the Site's two reactors, it was then stored for cooling purposes prior to dispatch off site. The current decommissioning phase focusses on draining the 6500m3 pond. Due to the Site's limited caesium removal facilities, a stand-alone effluent treatment plant was constructed to improve abatement and reduce the pond activity from 200 to 0.7 Bq/ml (β). This was necessary due to increased environmental standards introduced since the site had ceased generation ten years previously. Early characterisation and experience from other sites concluded that if the pond were to be drained without any treatment to the walls, doses to the Operators, during subsequent decommissioning works, would routinely be in excess ofγ). An opportunity was realised within the Ponds Programme that if the surface layer of the pond walls were to be removed during drain-down, ambient dose rates would be reduced by a factor of 10; this would allow for more cost-effective decommissioning options in the future. Ultrahigh pressure water jetting was tested and proved to yield a ∼95% total-activity reduction on treated surfaces. Challenges were overcome in providing safe and secure access to Decommissioning Operators to perform this operation by means of floating platforms on the surface of the pond. As strategies to clear facilities to exemption levels are becoming both cost prohibitive and not reasonably practicable, work is now underway in the Programme to determine the optimum condition for entry into long-term quiescent storage, prior to final demolition. This paper will discuss the strategy and techniques which led to Magnox Ltd ponds to be of national and international interest to the nuclear community. Copyright © 2013 by ASME.

Brown N.W.,Arvia Technology | Campen A.K.,Arvia Technology | Wickenden D.A.,Magnox Electric Plc | Roberts E.P.L.,University of Manchester
Chemical Engineering Research and Design | Year: 2013

Intermediate level waste (ILW) organic liquids and high alpha oils are difficult to dispose of via existing routes and are typically stored on site, classified as orphan wastes. Taking these sites to care and maintenance requires these wastes to be retrieved and treated to assure either passive storage as an immobilised waste or destruction of the waste. In this study adsorption coupled with electrochemical regeneration has been investigated as a method of treatment of contaminated oils. The process results in the complete destruction of the organic phase where the radioactivity is transferred to liquid and solid secondary wastes that can then be processed using existing authorised on-site waste-treatment facilities. Following successful laboratory and pilot scale trials, a demonstrator unit was commissioned at the Magnox Trawsfynydd decommissioning site to destroy 10. L of radioactive oils, comprising high alpha/ILW oils. Over 99% of the emulsified oil was removed and destroyed with the majority of activity (80-90%) being transferred to the aqueous phase. Secondary wastes were disposed of via existing routes with the majority being disposed of via the sites active effluent treatment plant. The regeneration energy required to destroy a litre of oil was 42.5. kWh. This on-site treatment approach eliminates the risks and cost associated with transporting the active waste oils off site for incineration or other treatment. © 2012 The Institution of Chemical Engineers.

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