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The status of criticality accident dosimetry in the UK

The status of criticality accident dosimetry in the UK. Chris Wilson Chris.Wilson@awe.co.uk www.awe.co.uk. Outline . Introduction Current status of criticality accident dosimetry in the UK An international perspective Conclusions. Introduction: A criticality excursion.

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The status of criticality accident dosimetry in the UK

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  1. The status of criticality accident dosimetry in the UK Chris Wilson Chris.Wilson@awe.co.uk www.awe.co.uk

  2. Outline • Introduction • Current status of criticality accident dosimetry in the UK • An international perspective • Conclusions

  3. Introduction: A criticality excursion • Mass of fissile material exceeds a critical value for a given matrix and geometry. • Initial burst of ~1015 fissions in ~1ms - 10s • Dose to workers close to an assembly can be lethal (>10 Gy) See McLaughlin, T. P. et al., “A Review of Criticality Accidents”, Los Alamos National Laboratory, Los Alamos, LA-13638 (2000) for a detailed history of criticality accidents

  4. UK requirements for dose assessment • Reporting of any individual likely to have received dose greater than 1 Gy within 8 hours of exposure • Dose assessment with less than 50 % uncertainty within 48 hours for any dose greater than 0.5 Gy • Dose assessment with less than 30 % uncertainty within 1 week for any dose greater than 0.25 Gy United Kingdom Parliament, “Ionising Radiations Regulations 1999”, HMSO, London (1999) Health and Safety Executive, “Requirements for the approval of dosimetry services under the Ionising Radiations Regulations 1999, Part 1: External radiations”, RADS 1/2008, HSE (2008)

  5. Absorbed dose as a function of neutron energy

  6. CADUG Mk-IV criticality locket H. J. Delafield, Radiation Protection Dosimetry, 10, pp. 237-249 (1985)

  7. Indium as orientation and quality indicator Phantom In In

  8. An international perspective • No two nations share a common system of CAD • US laboratories do not share a common design • Intercomparison exercises using Silene reactor • Limited data published on designs and methods

  9. Development of CAD • Monte Carlo techniques used to refine methodologies and calibrations • Biological methods of retrospective dosimetry • Intercomparisons highlighted relatively poor photon dose determination

  10. Conclusions • UK criticality accident dosimetry is subject to a programme of development to ensure the reliability of the service • International and intra-national diversity of CAD systems hinders cooperation between laboratories • International collaborations could enhance development and reduce costs

  11. Acknowledgements • Colleagues in Analytical Sciences, AWE • CADUG members - for their technical knowledge and support • IRPA13 organising committee

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