Spent Fuel Dissolution: An Examination of the Impacts of Alpha-Radiolysis

Abstract

When spent fuel eventually comes into contact with groundwater, fuel matrix dissolution will be strongly influenced by redox conditions in the near field. The most significant factors influencing redox conditions at the fuel surface in a reducing environment are alpha-radiolysis of water and the presence of reductants such as Fe(II) and H2 arising principally from canister corrosion. The radiolytic yield (G) of molecular oxidants, generally considered to be ~1 molecule of hydrogen peroxide per 100 eV for alpha-radiolysis, is expected to be considerably lower in the presence of reductants but the overall effect on the rate of matrix dissolution cannot yet be reliably quantified. We have attempted to estimate the effective yield of oxidants by examining the results from various studies of spent fuel and UO2 dissolution, including alpharadiolysis experiments. The analysis suggests that the effective yield (G eff) is likely to be no greater than 0.01 in the repository environment. The implications of low Geff values are discussed in relation to fuel dissolution rates. Some other aspects of radiolysis relevant to nearfield redox chemistry are also examined, including the potential significance of alpha emitters sorbed in the repository near field in producing radiolytic oxidants.

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References

  1. 1.

    H. Christensen and S. Sunder, Current state of knowledge in radiolysis effects on spent fuel corrosion. Studsvik Report STUDSVIK/M-98/71 (1998).

    Google Scholar 

  2. 2.

    R. Forsyth and L.O. Werme, Spent fuel corrosion and dissolution, J. Nucl. Mat. 190, p. 3–19 (1992).

    CAS  Article  Google Scholar 

  3. 3.

    L.H. Johnson, The dissolution of irradiated UO2 fuel in groundwater, Atomic Energy of Canada Limited Report, AECL-6837 (1982).

    Google Scholar 

  4. 4.

    H. Christensen, Calculations simulating spent-fuel experiments, Nucl. Tech. 124 (1998), p. 165

    CAS  Article  Google Scholar 

  5. 5.

    J.C. Tait and J.L. Luht, Dissolution Rates of Uranium from Unirradiated UO2 and Uranium and Radionuclides from Used CANDU Fuel Using the Single-pass Flow-through Apparatus. Ontario Hydro Used Fuel Disposal Program Report 06819-REP-01200-0006 ROO (1997).

    Google Scholar 

  6. 6.

    T.E Eriksen, U-B. Eklund, L.O. Werme and J. Bruno, Dissolution of irradiated fuel: A radiolytic mass balance study, J. Nucl. Mat. 227, p. 76–82 (1995).

    CAS  Article  Google Scholar 

  7. 7.

    S. Sunder, D.W. Shoesmith and N. H. Miller: Oxidation and dissolution of nuclear fuel (UO2) by the products of alpha radiolysis of water, J. Nucl. Mater. 244, p. 66–74 (1997).

    CAS  Article  Google Scholar 

  8. 8.

    D.W. Shoesmith and S. Sunder: The prediction of nuclear fuel (UO2) dissolution rates under waste disposal conditions. J. Nucl. Mat. 190, p. 20–35 (1992).

    CAS  Article  Google Scholar 

  9. 9.

    S.T. Horseman, J.F. Harrington and P. Sellin, Gas migration in MX-80 buffer bentonite, in Scientific Basis for Nuclear Waste Management XX, edited by W.J. Gray and I.R. Triay Mat.Res. Soc. Proc. 465, Pittsburgh, PA 1997). p. 1003–1010.

    CAS  Google Scholar 

  10. 10.

    J.C. Tait and L.H. Johnson: Computer modelling of alpha radiolysis of aqueous solutions in contact with used UO2 fuel in Proceedings of the 2nd Int. Conf. on Radioactive Waste Management, Winnipeg, MB, Sept., 1986, Canadian Nuclear Society, Toronto, p. 611–615.

    Google Scholar 

  11. 11.

    H. Christensen and E. Bjergbakke, Alpha-radiolysis of aqueous solutions, in Scientific Basis for Nuclear Waste Management IX, edited by L.O. Werme, Mat. Res. Soc. Proc. 50, Pittsburgh, PA 1985) p. 401–408.

    Google Scholar 

  12. 12.

    J.J. Cramer and J. Smellie: Final report of the AECL/SKB Cigar Lake analog study. Atomic Energy of Canada Limited Report, AECL- 10851, COG-93-147. (1994).

    Google Scholar 

  13. 13.

    J. Liu and I. Neretnieks: Some evidence of radiolysis in a uranium ore body - quantification and interpretation, in Scientific Basis for Nuclear Waste Management XVIII, edited by T. Murakami and R.C. Ewing Mat. Res. Soc. Proc. 353, Pittsburgh, PA 1995). p. 1179–1186.

    CAS  Google Scholar 

  14. 14.

    S. Stroes-Gascoyne, L.H. Johnson, P.A. Beeley and D.M. Sellinger, Dissolution of used CANDU fuel at various temperatures and redox conditions, in Scientific Basis for Nuclear Waste Management IX, edited by L.O. Werme, Mat. Res. Soc. Proc. 50, Pittsburgh, PA 1985), p. 317–326.

    Google Scholar 

  15. 15.

    D. Wronkewiecz, J.K. Bates, S.F. Wolf and E.C. Buck, Ten-year results from unsaturated drip tests with UO2 at 90°C: implications for the corrosion of spent nuclear fuel, J. Nucl. Mat. 238, p. 78–95 (1996).

    Article  Google Scholar 

  16. 16.

    L.H. Johnson and P. Taylor, Alteration of spent Candu fuel in aerated steam at 150°C, Report prepared for the US DOE/YMSCO under the terms of Contract #DE-AC08-95NV 11784, AECL-12003, COG-98-364 (1999).

    Google Scholar 

  17. 17.

    F. King and J.S. Betteridge, Ex situ measurements of the porosity of precipitated corrosion products on oxidized UO2, Ontario Hydro Report No 06819-REP_01200-0059 ROO (1998).

    Google Scholar 

  18. 18.

    J. Bruno, E. Cera, J. De Pablo, L. Duro, S. Jordana and D. Savage. Determination of radionuclide solubility limits to be used in SR-97. Uncertainties associated to calculated solubilities. SKB Technical Report 97–33. (1997).

    Google Scholar 

  19. 19.

    Nagra: Kristallin-I Safety Assessment Report, Nagra Technical Report 93-22, Nagra, Wettingen, Switzerland (1994).

    Google Scholar 

  20. 20.

    T.E. Eriksen and P. Ndalamba. On the formation of a moving redox-front by oa-radiolysis of compacted water saturated bentonite. SKB Technical Report 88-27 (1988).

    Google Scholar 

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Correspondence to P. A. Smith.

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Smith, P.A., Johnson, L.H. Spent Fuel Dissolution: An Examination of the Impacts of Alpha-Radiolysis. MRS Online Proceedings Library 608, 29 (1999). https://doi.org/10.1557/PROC-608-29

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