Nuclear Issues 5. Decline of Nuclear Power? Three Mile Island Chernobyl Waste Disposal

Transcription

1 Nuclear Issues 5 Decline of Nuclear Power? Three Mile Island Chernobyl Waste Disposal

2 Decline of Nuclear Power? Nuclear has been on the wane worldwide Ditto the US Many countries are now reconsidering

3 World Capacity GigaWatts

4 Construction Starts # of starts

5 Number of Reactors in the US

6 Cancellations and Shutdowns in the US

7 Why have construction starts declined? Safety concerns related to actual accidents Effect of public opinion Cost of nuclear energy Safety concerns : Can a reactor explode like a bomb? Loss of coolant accident (LOCA) today s major safety concern scenario : catastrophic plumbing failure loss of water = coolant reactor core melts explosive gases are generated containment is breached radioactivity released in large amounts

8 New concern today Terrorist action targeting nuclear reactors Recent study from Nuclear Energy Institute (= main lobbying group for nuclear industry in US) concludes : U.S. nuclear power plant structures that house radioactive materials, such as reactor containment buildings and spent-fuel storage sites, could withstand a terrorist attack involving a hijacked commercial airliner However, critics of the industry say: A simple attack upon the cooling system or the external electricity supply of a nuclear reactor, be it a small research reactor, or a large power reactor, would have devastating health consequences, producing a nuclear meltdown within minutes to hours.

9 Nuclear Power Worldwide

10 Nuclear Power by Country

11 Three Mile Island: March 28, 1979 TMI 2: a 3-month old PWR LOCA: Loss of Cooling Accident Partial core meltdown Tense 5-day emergency

12 Three Mile Island Schematic Diagram

13 Three Mile Island: What Happened Secondary system pump fails Heat builds up in primary system; relief valve at top of pressurizer opens Relief valve fails to close after excess pressure bleeds off; operators cannot detect this; LOCA Top of the core is exposed, and begins to melt

14 Consequences of TMI TMI-2 is permanently decommissioned Clean-up cost around $1 billion (so far) Significant changes in operating procedures No serious health consequences Last public safety assessment, NUREG-1150 (1991), says the probability of another core damage accident is about 30% over 20 years. The chance of a major radiation release is under 8% over 20 years

15 Consequences of TMI Kemeny commission report new recommendations (better training e.g.) NRC requires emergency (evacuation) plans since TMI heated public controversy Shoreham Brookhaven, N.Y. Boiling Water Reactor (BWR) Net Output: 809 MWe Permanently shutdown. Date closed : 05/ It was closed before commercial operation began! Local & State permits for evacuation plan never issued

16 Cost of nuclear power More regulations increase the time of building reactors with attendant increases in costs No new reactors built recently so costs are going down Not including construction costs decommissioning & cleanup costs radioactive waste disposal federal support other indirect cost on plants that were cancelled security improvements? According to critics in 1990 add 10.2 c/kwh

17 Chernobyl 110 km N of Kiev 130,000 people in 130 km radius Chernobyl site: 4 RBMK reactors graphite moderated large boiling water reactor

18 R(reactore)B(bolchoe)M(molchnastie)K(kipiachie). big power boiling

19 Chernobyl... Special features: - on-line refueling used for 239 Pu extraction - no pressure vessel! - core: 30m * 40m * 7m (huge) Design problems : - power increases when water is removed Why? water absorbs some n no water: some n not absorbed but moderated (by graphite) so they contribute to fission! so with extra heat more fission - design does not involve delayed neutrons

20 Accident Test to deal with power out emergency. Power from energy in turbines. Test was to run at MW. power down with local controls off; Xe gas builds captures n power at 30 MW (way too low) control rods out but no stable water flow test started anyway; all safety systems disconnected 1:23 water supply disappearing then at 1:30 reactor tripped to start test no water flow so increase in T and at 1:40 power surge; control rods in explosion!

21 Destruction

22 Afterwards... Explosion ripped off roof and released enormous amounts of radioactivity 35 people killed from radiation exposure 135,000 people evacuated and scattered all over FSU Studies suggest 100,000 excess cancer deaths will result in Europe Special case : thyroid cancer Ukraine was spending ~5% of its budget on the consequences of this catastrophe Thyroid cancers 131 I

23 The Liquidators Between 1986 and 1992, between 600,000 and 1,000,000 clean-up workers were exposed Cancer rate may be 4x the rate of the general population

24 Ghost Town

25 Nuclear Waste Disposal Some considerations: High level vs. low level Military vs. non-military On-site vs. off-site Short-term vs. long-term

26 Radioactive Waste Source:civil & military programs According to NRC Types: HLW high-level waste: spent-reactor fuel reprocessing waste hot & highly radioactive TRU transuranic waste isotopes beyond uranium LLW low-level waste : everything else Neither the NRC or DOE define activity of HLW!

27 Processes that generate nuclear waste Example: PWR 1GW e for a year generates - few m 3 HLW m 3 LLW kilotons of uranium mill tailings

28 Some numbers MTHM metric tons of heavy metal Commercial spent reactor fuel (US) Year Mass (MTHM) Radioactivity(MCi) ,200 30, ,300 32, ,800 39, ,100 34,700 Assumes no new reactors built and all plants run until their licenses expire.

29 Military HLW Site Volume (10 3 m 3 ) Radioactivity (MCi) Hanford Savannah River Idaho NEL West Valley Total

30 Weapons sites cleanup has been largest item in DOE budget for many years Savannah River SC 50 tanks (as large as capitol dome) of reprocessing waste Hanford, WA 177 tanks of HLW (leaking, burping, explosive?) 1.3x10 9 m 3 liquid waste in the soil dozen tons of Pu 2,100 tons of irradiated fuel DIRTIEST PLACE ON EARTH? Former SU? Much much worse... Potential problem: cleanup by companies who made the mess

31 Waste from Plutonium Example: waste from generating 1 kg of Pu 340 gallons of HLW gallons of LLW 2.5x10 6 gallons of cooling water Worse yet... What about Pu from the dismantling of nuclear weapons? Russia & US warheads US ~50 tons of Pu Russia ~100 tons

32 Disposal No burden of care / significant hazard for later generations Certainty for time scale of 10,000 years due to long-lived waste Radioactive waste from 1 ton spent reactor fuel Curies remaining Element Half-life 10yr 100yr 500yr 90 Sr/ 90 Y 28.1yr 1.2x x Cs/ 137 Ba 30 yr 1.6x x Tc 2.1x10 5 yr Total 3x ,000 53

33 Accumulation of spent fuel

34 Yucca Mountain To date no permanent disposal of HLW (anywhere in the world) Temporary storage in water tanks on-site at nuclear reactors Study of possible US sites began in amended : Yucca Mountain site chosen for further study Yucca Mountain plans call for storage of 70,000 metric tons of spent fuel 2002: Secretary Abrahams (Energy) recommends site development $9 billion spent so far on a $58 billion project May never open; now in hands of Congress Nevada doesn t want it... Some experts have serious doubts (Sci Am,March 2003, 48)

35 Aerial View of Yucca Mountain

36 Location of Yucca Mountain

37 Touring Yucca Mountain

38 Waste Storage at Yucca Mountain

39 Yucca Mountain Issues Expense Transportation Security Hydrology Seismology NIMB Long, long-term

40 The monumental task of warning future generations

41 What does transport look like?

42 Routes to Yucca Mountain

43 Status of Yucca Mountain according to DoE The Yucca Mountain Project is currently preparing a license application for the nation's first-ever repository for spent nuclear fuel and high-level radioactive waste. Plans called for submitting an application to obtain a license from the U.S. Nuclear Regulatory Commission no later than June 30, NRC has four years for decision