Going Underground: Safe Disposal of Nuclear Waste

Transcription

1 Going Underground: Safe Disposal of Nuclear Waste Burton Richter Pigott Professor in the Physical Sciences, Emeritus Stanford Energy Seminar January 23, 2012

2 Nuclear Energy Issues It is too expensive It is not safe We don t know what to do with very radioactive spent fuel

3 Lifecycle Emissions for Various Electricity Generation Technologies Comparison of Life Cycle Emissions in Metric Tonnes of CO 2 e per GW-hour for various modes of Electricity Production; P.J. Meier, Life-Cycle Assessment of electricity Generation Systems with Applications for Climate Change Policy Analysis, Ph.D. dissertation, University of Wisconsin (2002); S. White, Emissions form Helium-3, Fission and Wind Electrical Power plants, Ph.D. Dissertation, University of Wisconsin (1998); M. K. Mann and P. L. Spath, Life Cycle Assessment of a Biomass Gasification Combined-Cycle System, (1997), (ref 33). 3

4 Spent Fuel Love It or Hate It We Have It: What to Do With It Is the Issue We have about 60,000 tonnes now Current reactors will produce 60,000 tonnes more over their lifetimes Disposal costs are built into nuclear electricity costs at 0.1 cent/kw-hr ($20 B in fund now) 4

5 The Nuclear Fuel Cycle Today's LWRs Natural uranium has about 0.7% U-235 Enrichment increases U-235 to about 4.5% Fuel spends about 4 years in a reactor On removal used fuel spends about 4 years in a water pool Storage can then be in dry casks Long term isolation from the environment is the issue

6 Elements of Spent Fuel Component Uranium Fission Fragments Long-Lived Component Percent Of Total Radioactivity Negligible Intense Medium Untreated Required Isolation Time (years) ,000,000

7 Radioactivity of Used Fuel

8 Rules of the Game Spent reactor fuel must be safely isolated for as long as it is dangerous Must be retrievable for 50 years after emplacement Required time for untreated spent fuel is hundreds of thousands of years It is known to be possible The natural reactor at Oklo in Gabon, Africa started 1.7 billion years ago, burned for hundreds of thousands of years and its long lived radioactive elements have only moved a short distance

9 A Bit of History 1982 Congress says spent fuel disposal is a federal responsibility, sets an amount utilities have to pay, tells DOE to find a site 1987 DOE comes up with 3 (Texas, Washington state, and Nevada) Texas and Washington have lots of political muscle; Nevada (Yucca Mt.) gets it without any say in the matter Nevada has fought it ever since while DOE did 20 years of R&D at a cost of $10 billion and submitted an application for construction approval to the NRC in

10 Current Situation Yucca Mountain was supposed to open in 1998 Utilities have paid into the waste fund; have contacts with DOE; courts have said DOE is in default and has to pay for temporary storage at reactor sites No problem (except money) in storing spent fuel at reactors The Obama administration withdraws the application to license Yucca Mt. in 2009 and creates the blue ribbon commission in 2010 to recommend what to do and how to do it 10

11 The Future of Spent Fuel Disposal This is a big political component and a smaller technical one 1987 Congress forced repository on Nevada Other countries have used a consent-based system (Sweden, Finland, France) Blue ribbon commission recommends a consent-based system We have a working repository in New Mexico WIPP (Waste Isolation Pilot Project) 11

12 Relative CD Hazard Radiotoxicity of LWR Spent Fuel 1.E+04 1.E+03 1.E+02 1.E+01 1.E+00 1.E-01 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 Total Actinides Total FP Np-237 Pu-239 Pu-240 Am E-02 1.E-03 Time, years 12

13 Used Fuel Assembly From a PWR

14 Yucca Mountain

15 Yucca Mountain Repository Layout

16 Sweden s System

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19 Finland Follows Sweden

20 France Disposal in alkaline clay Site selected with local agreement Fission fragments an long lived actinides in glass logs

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22 BRC Recommendations Focus on granite clay or salt Negotiate an agreement with the state and locality Set up a semi-private company to develop and manage the project Give the state a large financial incentive Take Congress out of the loop on spending from the waste disposal fund

23 An Alternative for Disposition of Pu And Minor Actinides Nuclear Answer: Use nuclear reactors to burn or reduce inventories of plutonium and minor actinides in MOX or inert matrix fuels. Geologic Answer: Geologic disposal of spent nuclear fuel and/or immobilization of actinides in durable solids.

24 An Alternative Closing the Fuel Cycle Plutonium recycling MA + FP Spent Fuel Direct disposal Pu + MA + FP Uranium Ore (mine) FP P&T of MA Time (years) CISAC February 25th,

25 (a) Transmutation Schematics with LWR Recycle LWR Separation Plant Fast System (one for every 7-8 LWRs) Separation Plant Reprocessed Fuel Plutonium MOX fuel U&FF Actinides U&FF (b) Without LWR Recycle LWR Fast System Separation Plant Actinides U&FF 25

26 References BRC home page: BRC Disposal Subcommittee /draft_disposal_report_ pdf Sweden s Repository aspx

27 BACKUP

28 US commercial spent fuel quantities and storage locations in 2005 Material Approximate Quantity (metric tons) Number of sites Total commercial spent fuel storage 54, nuclear plant sites with 103 operating reactors 9 nuclear plant sites with no operating reactors 1 commercial interim storage site (Morris in Illinois) 2 DOE sites (Ft. St. Vrain in Colorado and Idaho National Laboratory) a Pool storage 47, operating sites 1 centralized site (Morris in Illinois) 9 nuclear plant sites with no operating reactors Cask storage 7, at nuclear plant sites 2 DOE sites (Ft. St. Vrain in Colorado and Idaho National Laboratory) a

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30 Nuclear Fuel Cycles: Geologic Perspective

31 1,000,000-yr Dose to Average Individual at 20 km Yucca Mountain Viability Assessment (1998)

32 Radiotoxicity Hedin (1997) SKB Report 97-13

33 Inventory of Decay Heat Wigeland et al. (2006) Nuclear Technology

34 Thermal Power of Used Nuclear Fuel 7% of full power at moment after shutdown

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