The Mythology of the Back End of the Nuclear by efr19747

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									The Mythology of the Back End
  of the Nuclear Fuel Cycle


           Allison Macfarlane
  Program in Science, Technology & Society
                    MIT
              April 24, 2006
            Yucca Mountain Status
• Draft EPA standards:
   – 15 mrem/yr individual dose standard for up to 10,000 years
   – 350 mrem/yr individual dose standard for 10,000 - 1 million
     years
• Waiting for new YM schedule due summer 2006
   – At least, 5 years till construction begins
• Change to use “clean” loading facility on site
• Domenici Bill
   – Permanent land withdrawal (147,000 acres)
   – Repeal 70,000 MT capacity limit
   – Allow DOE to undertake rail line construction
                  The Numbers
• Capacity of Yucca Mountain
  – Legislated: 70,000 MT
     • 63,000 MT spent fuel
     • 7,000 MT high-level waste from nuclear complex
• DOE’s estimate of capacity of YM
  – 119,000 MT maximum
     • Assumes 105,000 MT spent fuel & 12,000 MT HLW
         Projected HLW Amounts

• DOE High Level               • Civilian Spent
  Waste                          Fuel
                                  – Current inventory
  – DOE estimate: 12,000              • ~52,000 MT by end of 2005
    MT                                • Grows by ~2,000 MT annually
  – Includes spent nuclear        – If no license extensions, total
    fuel and vitrified high-        ~80,000 MT
    level waste                   – If all ~100 reactors get license
                                    extensions, then would have
                                    ~120,000 MT
                                  – New reactors - ?
 Constraints on Yucca Repository Capacity
• Waste Itself
   – Volume
   – Heat (age, burn-up)
   – Radioactivity
• Geology of the Site
   – Distribution of faults/fractures
      • 2 effects: mining ease and fast water pathways
   – Volcanism
   – Water table
      • Increases in elevation to N/NW
   – Lithological variation
      • Repository unit thins to N/NE and WNW (must be >200m)
      • Presence of Lithophysae (need <15-20% lithophysae)
• Land ownership/Mineral rights
Global Nuclear Energy Partnership Proposal

• Phase 1
  – Treat Spent fuel with UREX+ to separate materials
    into different waste streams
• Phase 2
  – Use MOX fuel in LWRs (Pu+Np, Pu+Np+Am)
• Phase 3
  – Treat LWR spent fuel with UREX+
  – Transmute transuranics in fast reactors
  – Treat fast reactor fuel with pyroprocessing
       UREX+ waste streams
• Uranium
• Technetium
• Cesium + Strontium
• Transuranics (Plutonium, Neptunium,
  Americium, Curium)
• Fission Products
Waste streams for 2,000 MT spent fuel input

                     No        PUREX      UREX+      Pyroprocess
                  reprocess-
                     ing
   High-level     2,000 MT      490 MT    230 MT       490 MT
     waste                       glass     glass       ceramic
                               1,900 MT
                                 U+Tc
  Intermediate        0        175 MT        ?            ?
   -level waste

   Low-level          0        1,050 MT   2,560 MT    2,360 MT
    waste
  Waste Streams with successful GNEP
         (complete fuel cycle)
• High-level waste
   – Glass- and ceramic-containing fission products
   – Technetium-99 - go to a repository in a suitable waste
     form
   – Wastes in “storage” for 300 years [geologic storage?]
      • Cesium-137/Strontium-90
• Low-level waste: large quantities
• Other wastes?
   – Raffinates with trace amounts of radionuclides
   – Spent radioactive solvents
     Success with GNEP means
• UREX+ works at high efficiencies (not there yet)
• LWRs are adapted for MOX use
• Significant number of new LWRs built
• Pyroprocessing works at high efficiencies (not
  nearly there - not certain it will)
• Fleet of fast reactors is built and operate
  (unproven; these are paper reactors now)
• = High risk endeavor
  Impacts if fuel cycle is not completed

• It stops with Phase 1 (UREX+ only): Large
  Impact
  – Large increase in low-level waste (requires shallow
    burial - but where?)
  – High-level waste : Tc, Cs/Sr, Pu+Np, other actinides,
    fission products
     • Same heat and radioactivity as spent fuel
     • More waste - now have to find a waste form for each of
       these streams
 Impacts if fuel cycle is not completed

• It stops with Phase 2 (UREX+ MOX fuel)
  – Large increase in low-level waste
  – High-level waste streams
     • Tc, Cs/Sr, other actinides, fission products
     • MOX spent fuel to dispose of - hotter than LWR spent
       fuel - needs more repository space
     • Separated Pu to dispose of
        – Probably would not be able to use all separated Pu in MOX fuel
            » National Academy estimated it would take 70% of US
              reactors 30 years to irradiate 600 MT plutonium - that’s
              longer than the life of the reactors!
    Do we need more repositories?
• Part of GNEP justification is to reduce waste volume to
  maximize Yucca Mt space to accommodate waste from
  new fleet of reactors
   – Few (1+) repositories if GNEP works perfectly; otherwise,
     we’ll need more repositories
   – Will definitely need a number of low-level waste sites
• Part of justification is to accommodate new EPA
  standards which go out to 1 million years
   – >50,000 years, Tc-99 and Np-237 dominate dose
   – This is because Yucca provides an oxidizing environment
      • If it were reducing, the Tc-99 especially would not be an issue - under
        reducing conditions, Tc-99 is insoluble and won’t move
                  What to do?
• The best solution to the problem of nuclear waste
  is geologic repositories
   – They provide lowest risk option for most protection
     from radionuclides for longest time
   – Doesn’t depend on unproven technologies
   – Probably least costly
   – Multiple barrier concept: the waste form, the
     engineered canister, the surrounding geology provides
     defense in depth
                 What to do? (2)
• First, decide whether
  Yucca Mt is a good
  enough site
   – Complex geology
   – Very long standard
   – Limited ability of
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     performance assessment to
     evaluate the site
• Decide Yucca Mt by
  comparing to other
  investigated sites
            What to do? (3)
• Even if Yucca okay, capacity there is
  limited by the geology
• If the US experiences an expansion in
  nuclear power, there will likely be a need
  for additional repositories
              What to do? (4)
• There are plenty of good sites in the US -
  use IAEA criteria
     • Long-term (millions of years) geologic stability - no
       seismicity or volcanism
     • Low groundwater content and flow at repository
       depths - stable for tens of thousands of years
     • Stable geochemical or hydrochemical conditions at
       depth, mainly described by a reducing environment
     • Good engineering properties that readily allow
       construction of a repository
             What to do? (5)
• Many decent sites in US, including East
  – BUT - Nuclear Waste Policy Act Amendments
    of 1987 forbid study of crystalline rock - which
    underlies much of the eastern half of the US
• Process for selecting future repository sites
  must be perceived to be fair

								
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