The Nuclear Decommissioning Authority

  3rd Annual Workshop Proceedings of the Integrated Project Fundamental Processes of Radionuclide Migration (6th EC FP IP FUNMIG) 2007 (7.39mb)
These are the proceedings of the 3rd Annual Workshop of the Euratom FP6 Integrated Project Fundamental Processes of Radionuclide Migration(FUNMIG). The 3rd Annual Workshop of the project was hosted by NDA and held in Edinburgh 26 - 29 November 2007.

  A Guide to GoldSim Implementation of the Nirex Biosphere Model (1.15mb)
United Kingdom Nirex Limited (Nirex) has used a spreadsheet-based implementation of their biosphere model to calculate equilibrium biosphere effective dose factors for use in generic performance assessments. This implementation has proved satisfactory, but it has some limitations. The time dependence of the approach to equilibrium cannot be studied, the implementation is rather inflexible with respect to the inclusion of additional biosphere components and processes, and it is not straightforward to adapt the model to undertake calculations in which parameter uncertainty is incorporated. For these reasons, it was decided that the model should be re-implemented within the GoldSim general-purpose simulation package. This implementation immediately allows kinetic aspects of the model to be represented. Although additional biosphere components and processes, and the facility to undertake Monte Carlo calculations to explore the effects of parameter uncertainty are not included at this stage, the implementation structure adopted is such as to facilitate enhancements of the model in those two areas in the future.\r\nAs the underlying structure of the model and the reference data sets to be used with it have been described in detail elsewhere, this report addresses only the structure of the GoldSim implementation, the way in which the user can add or modify input data, and results obtained for a reference case also studied with the spreadsheet-based implementation.\r\n<br /><br />

  A Guide to the Spreadsheet Model used for Groundwater and Well Calculations for Generic Performance Assessments 554236 (1.04mb)
United Kingdom Nirex Limited (Nirex) has been undertaking a series of Generic Performance Assessments (GPAs) of a deep geological repository for intermediate- and some low-level radioactive wastes. In order to undertake such assessments, it requires a set of radionuclide-dependent biosphere factors that relate radionuclide fluxes to the near-surface environment to effective dose rates to representative members of potentially exposed groups (PEGs). A methodology and data for the calculation of such factors have been described previously, and a spreadsheet was developed to implement that methodology. This spreadsheet has been updated to include additional radionuclides and also to include a representation of spray irrigation. It is this updated spreadsheet that is described in this report.\r\nHerein, a brief account is given of the methodology used to estimate the radionuclide-dependent biosphere factors. This provides a basis for describing how that methodology has been implemented in the spreadsheet. The standard data sets compiled for use with the methodology are set out and the results of calculations undertaken using those standard data sets are presented. \r\nThe spreadsheet implementation of the methodology only allows results to be determined at equilibrium. However, the underlying methodology is formulated in kinetic terms. By implementing the methodology in the GoldSim simulation system, it has been possible to explore the timescales over which equilibrium is achieved for different radionuclides. Furthermore, comparison of results from the GoldSim implementation for long periods of continuous uniform input with equilibrium results from the spreadsheet implementation allows verification of both implementations to be demonstrated. In this report, an account is given of the verification calculations undertaken using the two implementations.\r\n<br /><br />

  A Summary of Input Data for use in Human Intrusion Calculations in Generic Performance Assessment (223kb)
United Kingdom Nirex Limited (Nirex) has previously used the computer code HINDSITE to assess the radiological risks of post-closure inadvertent human intrusion into a generic deep geological repository for intermediate and certain low level radioactive wastes. More recently, a new spreadsheet model, SHIM, has been developed for use by Nirex for a similar purpose. In 2003, a review of parameter values for use in HINDSITE was produced. However, since then, Nirex has identified a number of additional radionuclides for inclusion in post-closure assessments and has updated the data used in assessments of the groundwater-discharge and well-abstraction pathways. Therefore, this report has been produced to provide radionuclide-specific data for use in SHIM.\r\nExternal dose factors, effective dose per unit intake values for ingestion and inhalation, and mean gamma energy per transformation values were readily extracted from standard compilations of data. Distribution coefficients for soils and plant:soil concentration ratios were calculated taking into account the expected inverse correlation between these quantities. Reference values and ranges appropriate to a loam soil have been provided explicitly and recommendations made as to how those recommended values and ranges should be modified for application, in sensitivity studies, to sand and clay soils. Transfer factors for animal products and concentration ratios for freshwater fish have largely been extracted from data compiled for Nirex for use in the context of the groundwater and well-abstraction pathways.\r\n<br /><br />

  Advance allocation: Proposal on how to manage overseas spent nuclear fuel awaiting processing at Sellafield - 2007 consultation (DBERR Website)
This consultation (14 June 2007 - 26 July 2007) deals with the Nuclear Decommissioning Authority’s proposal on how to manage overseas customers spent nuclear fuel awaiting reprocessing at Sellafield – specifically to allocate nuclear materials from UK stocks in advance of the actual recovery of the customers material from reprocessing.

  An Evaluation of the Potential Toxicological Significance of Releases of Beryllium from a Deep Geological Repository 553963 (308kb)
In a recent study, a methodology developed previously for United Kingdom Nirex Limited (Nirex) for undertaking a screening assessment of the post-closure chemical toxicological impact of a deep geological repository for radioactive wastes has been applied to the groundwater transport pathway for the Nirex Phased Geological Repository Concept. This study failed to screen out beryllium as having the potential to give rise to a significant toxicological impact following release from the repository into a near-surface aquifer. Therefore, a more comprehensive evaluation of the potential toxicological implications of beryllium releases from a deep repository to the biosphere has been undertaken and is reported herein.\r\nThe methodology used herein to represent beryllium transport in the biosphere is identical to that used by Nirex to represent the transport of radionuclides. Through application of this methodology, beryllium concentrations in environmental media and intake rates by humans by inhalation and ingestion have been determined. These concentrations and intake rates have been evaluated relative to naturally occurring concentrations of beryllium, intake rates of naturally occurring beryllium and environmental standards used for evaluating the implications of exposures to beryllium.\r\n<br /><br />

  Analogue evidence relevant to the UK HLW glass waste forms (1.02mb)
This report evaluates the role of analogues relevant to the long-term performance of vitrified high level waste in the UK. Evidence from natural, archaeological and historic glass analogues shows that the mechanisms and rates of glass degradation depend both on the glass composition and the physical and chemical properties of the environment in which the glass has been held. Some of the industrial, historical and natural objects and materials are considered as good analogues to the vitrified waste and can provide supportive information about long-term behaviour of glasses. Areas where no satisfactory analogues can be found are identified.<br /><br />

  Annual Plan 2007/8 (2.54mb)
NDA's Annual Plan to set out what we intend to achieve in 2007/8.

  Annual Report and Accounts 2006/7 (5.05mb)
The year's accounts and report on performance for 2006/7.

  Audit of Prioritisation Process 2007 - Overview Report Rev 0 (172kb)
This document summarises findings of the audit of Site License Companies draft Lifetime Plan 08 submissions against the application of the prioritisation process as detailed in NDA procedure EGPR02. The document covers: · scope of the audit carried out against draft LTP 08 · approach to implementation of the audit · findings from the audit · recommended actions to improve effectiveness of the process.