Safety of Spent Fuel Casks

Dry storage cask
Behältermodell CASTOR V/19. Source: GNS Gesellschaft für Nuklear-Service mbH

Dry storage casks or canisters are widely used for dry interim storage and for transportation of spent nuclear fuel. They can be oriented and stored vertically or horizontally. The casks provide both shielding and containment.  The casks are typically steel cylinders that are either welded or bolted closed. The steel cylinder provides leak-tight containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and the public. This additional material serves as a barrier preventing physical damage that might result in a release of radiation.

Safety of Spent Fuel Casks

Safety of spent fuel casks stands on various criteria. These criteria may be grouped according to following aspects:

  • Subcriticality. Fulfillment of this criterion is based on:
    • the design of the spent fuel cask,
    • requirements on materials of the spent fuel casks ( e.g. adding neutron absorbing materials (typically boron) in storage racks baskets),
    • limiting of stored fuel (e.g. fuel enrichment, assembly burnup)
  • Cooling.  Fulfillment of this criterion is based on:
    • the design of the spent fuel cask (e.g. shape and orientation of cooling fins),
    • requirements on inert gas pressure,
  • Radiation Shielding.  Fulfillment of this criterion is based on:
    • the design of the spent fuel cask (e.g. wall thichness),
    • neutron shielding (polyethylene moderator rods)
  • Integrity. Fulfillment of this criterion is based on:
    • the design of the spent fuel cask,
    • the design of shock absorbers,
    • ensuring periodic inspections

These goals are not difficult to achieve. In dry cask storage there are very few scenarios that can be imagined that could provide the energy needed to break the cask and spread the radioactive material into the surrounding environment. Because of their inherent flexibility, cask systems have proved popular with reactor operators.

References:
Nuclear and Reactor Physics:
  1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
  2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
  3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
  4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
  5. W.S.C. Williams. Nuclear and Particle Physics. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467
  6. G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965
  7. Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.
  8. U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.

Advanced Reactor Physics:

  1. K. O. Ott, W. A. Bezella, Introductory Nuclear Reactor Statics, American Nuclear Society, Revised edition (1989), 1989, ISBN: 0-894-48033-2.
  2. K. O. Ott, R. J. Neuhold, Introductory Nuclear Reactor Dynamics, American Nuclear Society, 1985, ISBN: 0-894-48029-4.
  3. D. L. Hetrick, Dynamics of Nuclear Reactors, American Nuclear Society, 1993, ISBN: 0-894-48453-2. 
  4. E. E. Lewis, W. F. Miller, Computational Methods of Neutron Transport, American Nuclear Society, 1993, ISBN: 0-894-48452-4.

See above:

Spent Nuclear Fuel