The Mythology of the Back End of the Nuclear Fuel Cycle Allison Macfarlane Program in Science, Technology & Society MIT April 24, 2006.

The Mythology of the Back End of the Nuclear Fuel Cycle

Allison MacfarlaneProgram 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 Waste– DOE estimate: 12,000

MT

– Includes spent nuclear fuel and vitrified high-level waste

• Civilian Spent Fuel– Current inventory

• ~52,000 MT by end of 2005

• Grows by ~2,000 MT annually

– If no license extensions, total ~80,000 MT

– 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

300 m

300 m

Tiva Canyon welded tuff

Paintbrush nonwelded tuff

Topopah Spring welded tuff

Calico Hills nonwelded tuff

Lower welded tuff units

Water Table

Repository Level

W E

Ghost Dance fault Bow Ridge fault zone

Solitario Canyon fault

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 reprocess-

ing

PUREX UREX+ Pyroprocess

High-level waste

2,000 MT 490 MT glass

1,900 MT U+Tc

230 MT glass

490 MT ceramic

Intermediate-level waste

0 175 MT ? ?

Low-level waste

0 1,050 MT 2,560 MT 2,360 MT

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 performance assessment to evaluate the site

• Decide Yucca Mt by comparing to other investigated sites

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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