Papers in this volume: 5
1. Recurring events: a nuclear safety concern
Author(s): Pyy P. and Ross D.F.
Page: 23
Keywords: Boiling water reactors (BWRs), Disturbances, Event analysis, Light water reactors (LWRs), Nuclear incidents, Nuclear operations and safety, Operating experience, Pressurised water reactors (PWRs), Recurrence
Abstract: Within the nuclear industry, the phenomenon of recurrence�that is, the complete or partial repetition of nuclear incidents�has come under renewed scrutiny. Following a brief explanation of recurrence, the paper gives some relevant examples and highlights the acknowledged need for a more effective international reporting system. Finally, the paper offers some possible avenues for the future.
2. Validation of RELAP5-3D RBMK-1500 reactor model
Author(s): Uspuras E., Kaliatka A. and Bubelis E.
Page: 27
Keywords: Baltic States, Boiling water reactors (BWRs), Light water reactors (LWRs), Mathematical modelling, Model validation, Nuclear operations and safety, Reactor shutdown
Abstract: This paper deals with RELAP5-3D code validation through the modelling of RBMK-1500 specific transients at Ignalina nuclear power plant (INPP), where the neutronic response of the core is important. A best-estimate RELAP5-3D model of the INPP RBMK-1500 reactor has been developed and validated against real plant data. The resulting calculations demonstrate reasonable agreement with INPP measured data. Predictions of the separate main circulating circuit thermal-hydraulic parameters as well as physical processes correlate well with actual processes, occurring in the primary circuit of the RBMK-1500 reactor. The calculated reactivity and the total transient reactor core power are also in reasonable agreement with the measured plant data, which demonstrates the correct modelling of the neutronic processes taking place in the reactor core. Validation of the RELAP5-3D model suggests that it could be used successfully in the future to substantiate RBMK-1500 safety calculations.
3. Ospar - an operator's perspective
Author(s): Coates R.
Page: 35
Keywords: Radioactive waste management - transport and disposal, Radiological discharges
Abstract: The Ospar Convention was established in 1992 with the express aim of protecting the maritime area against the adverse effects of human activity. The 15 member countries, together with interest from various non-government organisations, strive to further this aim via their annual and ministerial meetings. This paper takes a brief look at Ospar, particularly from the nuclear operator's viewpoint, and highlights the 1998 Sintra Statement and its aspirations, to which the nuclear industry must adhere.
4. Development and otpimisation of generic decommissioning strategies for civil Magnox reactors
Author(s): Carpenter G., Hebditch D., Meek N., Patel A. and Reeve P.
Page: 39
Keywords: Magnox reactors, Radioactive waste management - transport and disposal, Regulatory issues, Regulatory system, Waste management & disposal
Abstract: BNFL Environmental Services has formulated updated proposals for the use of decision analysis in the development of decommissioning strategy. The proposals are based on the Department of Transport, Local Government and the Regions manual for practitioners on multi-criteria analysis, specifically multi-criteria decision analysis, as suited to complex problems with a mixture of monetary and non-monetary objectives. They take account of up-to-date academic methodology, the newly issued BNFL decision analysis framework for environmental decisions and a wide variety of other engineering, optioneering and optimisation processes. The paper also summarises legislative and company policy areas of importance to decommissioning strategy development. Higher-level generic reactor and site remediation strategies already exist. At the lower level, various generic decommissioning reference processes and project options need development. For the past year, Environmental Services has held responsibility to respond to the Nuclear Installations Inspectorates' quinquennial review, develop and maintain up-to-date strategies, institute the review of a selected number of key strategies, and respond to changing circumstances including stakeholder views. Environmental Services is performing a range of generic studies for selection of strategies and end-points as used for a variety of waste management and site care and maintenance preparations.
5. Effects of chronic radiation exposure on small mammals in the Chernobyl exclusion zone
Author(s): Jackson D., Copplestone D. and Stone D.M.
Page: 51
Keywords: Radiological discharges, Radiological health and safety
Abstract: The Chernobyl reactor accident in April 1986 caused the release to atmosphere of some 2 � 10 6 TBq, or more, of total fission/activation products. Estimates of deposition vary, although it is probable that about half the activity was deposited within 20 km of the release point, predominantly following two plume trajectories to the north and west. This resulted in the death of pine trees over 400 ha, the abandonment of up to 150 000 ha of agricultural land and the establishment of an exclusion zone extending to 30 km from the site. High levels of radionuclide contamination continue to prevail within the exclusion zone. Nonetheless, recolonisation has been widespread. Mixed deciduous woodlands, with a high proportion of birch (Betula spp.) and willow (Salix spp.), have become established in the forest areas, while agricultural land has succeeded to tall grassland and scrub. Field sites investigated in this study, during 2001�2003, exhibited external gamma dose rates varying from 0.1 �Sv h -1 to 140 �Sv h -1 . Corresponding mean concentrations of 137 Cs in the top 20 cm of soil varied from about 6 � 10 2 to 3 � 10 6 Bq kg -1 dw (dry weight). Little impact is evident on populations of small mammals in these areas, either for species diversity or overall abundance, although there is a slight (not statistically significant) trend for increasing spleen weight in the bank vole with increasing levels of contamination. Previous suggestions that populations contain a preponderance of juveniles and sub-adults at the highest contaminated sites are not supported.