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.
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.
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
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.