Nuclear Safety in Light of Fukushima. Andrew C. Kadak, Ph.D. Council of State Governments June 19, 2012

Transcription

1 Nuclear Safety in Light of Fukushima Andrew C. Kadak, Ph.D. Council of State Governments June 19, 2012

2 Background Former Professor of the Practice in the MIT Nuclear Science and Engineering Department now Research Affiliate Former President and CEO of Yankee Atomic Electric Company Past President of the American Nuclear Society Commissioner of the Rhode Island Atomic Energy Commission Member of the US Nuclear Waste Technology Review Board Past Member of the Nuclear Energy Institute Executive Committee Past Member of the Electric Power Research Institute Research Advisory Committee Ph.D. and Master s degree in Nuclear Engineering from the Massachusetts Institute of Technology kadak@mit.edu

3 Outline The event What happened to the nuclear plants Preliminary Lessons Learned Industry Readiness Nuclear Regulatory Commission Response Industry Response Conclusions

4 Event Initiation The Fukushima nuclear facilities were damaged in a magnitude 8.9 earthquake on March 11 (Japan time), centered offshore of the Sendai region, which contains the capital Tokyo. Plant designed for magnitude 8.2 earthquake. An 8.9 magnitude quake is 7 times in greater in magnitude. Serious secondary effects followed including a significant tsunami, significant aftershocks and a major fire at a fossil fuel installation. 4

5 Fukushima Daiichi Nuclear Station Six BWR units at the Fukushima Nuclear Station: Unit 1: 439 MWe BWR, 1971 (unit was in operation prior to event) Unit 2: 760 MWe BWR, 1974 (unit was in operation prior to event) Unit 3: 760 MWe BWR, 1976 (unit was in operation prior to event) Unit 4: 760 MWe BWR, 1978 (unit was in outage prior to event) Unit 5: 760 MWe BWR, 1978 (unit was in outage prior to event) Unit 6: 1067 MWe BWR, 1979 (unit was in outage prior to event) Unit 1 5

6 Background Friday March 11, 2011; 9.0 magnitude earthquake off the northeastern coast of Japan 230 miles northeast of Tokyo A massive Tsunami swamped backup generators supplying coolant Reactors began to heat up Loss of coolant to spent fuel March 12 current Continuing efforts to cool the reactors, install covers on the reactors, cool the spent fuel and restore normal functions.

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8 The Wave Coming on to the Site

9 Over topping the Seawall

10 Flooding the Site

11 Flooding and taking out cars and tanks

12 Wave hits reactor building

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15 After

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17 17 Fukushima Daiichi Unit 1

18 Fukushima Daiichi Unit 1 Typical BWR 3 and 4 Reactor Design 18

19 Initial Response Nuclear reactors were shutdown automatically. Within seconds the control rods were inserted into core and nuclear chain reaction stopped. Cooling systems were placed in operation to remove the residual heat. The residual heat load is about 3% of the heat load under normal operating conditions. Earthquake resulted in the loss of offsite power which is the normal supply to plant. Emergency Diesel Generators started and powered station emergency cooling systems. One hour later, the station was struck by the tsunami. The tsunami was larger than what the plant was designed for. The tsunami took out all multiple sets of the backup Emergency Diesel generators. Reactor operators were able to utilize emergency battery power to provide power for cooling the core for 8 hours. Operators followed abnormal operating procedures and emergency operating procedures. 19

20 20 Loss of Makeup Offsite power could not be restored and delays occurred obtaining and connecting portable generators. After the batteries ran out, residual heat could not be carried away any more. Reactor temperatures increased and water levels in the reactor decreased, eventually uncovering and overheating the core. Hydrogen was produced from metal water reactions in the reactor. Operators vented the reactor to relieve steam pressure energy (and hydrogen) was released into the primary containment (drywell) causing primary containment temperatures and pressures to increase. Operators took actions to vent the primary containment to control containment pressure and hydrogen levels. Required to protect the primary containment from failure. Primary Containment Venting is through a filtered path that travels through duct work in the secondary containment to an elevated release point on the refuel floor (on top of the reactor building). A hydrogen detonation subsequently occurred while venting the secondary containment. Occurred shortly after and aftershock at the station. Spark likely ignited hydrogen.

21 Hydrogen Detonation at Unit 1 Refuel Floor 21 Reactor Building

22 Beginning of Core Damage Times Unit 1 4 hours Unit 2 72 hours Unit 3 44 hours Reasons No electrical power Station blackout with batteries lasting for 8 hours Loss of ultimate heat sink Some design differences Operational decisions Difficulty in reaching manual valves

23 What was the Problem Earthquake knocked out off site power and damaged roads, communications, and site but did not affect the safety related systems Plant responded normally emergency diesels started and plant was shutdown and cooled Tsunami caused a flood that damaged cooling pumps, diesel generators, batteries, and electrical distribution systems. The tsunami did the major damage due to flooding not the earthquake

24 Entering 4 th Level of Safety Level 1 Design basis accidents major large break loss of coolant accident plus others loss of power including natural disasters earthquakes, hurricanes, tsunamis, flooding, fires, tornados, etc. Level 2 Post Three Mile Island Severe accident management core melt accidents Level 3 9/11 Terrorist Attack Emergency response to air craft crash into reactor Level 4 Post Fukushima Review

25 US Industry Design Upgrades Initial Design Basis Accidents Loss of coolant, loss of offsite power, etc. Post Three Mile Island Upgrades March 1979 Instrumentation qualified for harsh environments Training for severe core damage accidents Revision to plant emergency procedures Symptom based Installation of Safety Parameter Display Systems Identification of Critical Safety Functions Upgraded emergency plans onsite and offsite Key areas communications and decision making

26 Post 9/11 Upgrades Assumption is plant is hit by an aircraft or terrorist bombs Procured portable diesel driven pumps and developed procedures to use the portable pumps to inject water from external sources into the reactor, primary containment, spent fuel pool, hotwell, and condensate storage tanks. Made modifications to the plant to provide connections for using the portable diesel driven pump. Developed procedures and staged equipment needed to manually open reactor relief valves and containment vent valves under loss of power conditions

27 Nuclear Regulatory Commission Response Issued Lessons Learned Report (July 12, 2011) Inspected all plants for capabilities to respond to severe environmental impacts To issue orders for upgrades as necessary by plant Industry developed their own plans focused on improving mitigation.

28 Key NRC Lessons Improve overall regulatory framework to risk informed regulations with defense in depth Re evaluate and upgrade seismic and flood protection include fires caused by events Strengthen station blackout mitigation for beyond design basis events. Improved venting capability and hydrogen control Spent fuel water makeup capability upgrades Develop extensive damage mitigation guidelines and multi unit events. Improvements in offsite emergency preparedness, coordination and communication.

29 Browns Ferry Alabama Tornados Cause Loss of Offsite Power April 28, 2011

30 Fort Calhoun Nebraska Flooding June 20, 2011

31 North Anna (Virginia) Earthquake Twice Design Basis August 23, 2011

32 U.S. Industry Response to Fukushima to Enhance Nuclear Safety More than 300 major pieces of equipment acquired or ordered, ahead of regulatory requirements to be developed Diesel driven pumps Large portable generators Small load diesel generators Fire trucks Portable ventilation units Pro actively invested several million dollars and extensive manpower resources to deploy the equipment and strategies discussed Taken many steps towards setting up regional response centers for rapid response, with equipment and resources beyond individual site capabilities.

33 U.S. Industry Response to Fukushima to Enhance Nuclear Safety Verified that equipment, procedures and staffing are in place to respond to threats Verified capability to cope even during a complete loss of power Verified each plant s capabilities to protect against floods and fires after earthquakes Enhanced capability to protect spent fuel pools against extreme natural events Started work to institute FLEX, an industry developed strategy that leveraged the post 09/11.experience Provided for coping for extended loss of power Maintains reactor and used fuel pool cooling capabilities when challenged beyond design basis Protects against extreme external events Performance based all hazards safety approach Flexible response to a variety of challenges

34 US Dependency on Nuclear Energy 104 Operating Plants Producing 20% of the US power 101,000 Mwe Supplying over 63% of emission free energy 35 Boiling Water Reactors 69 Pressurized Water Reactors

35 How about New England? Circa 1980 New England Nuclear Plants Operating: Yankee Rowe Connecticut Yankee Millstone Units 1, 2 Vermont Yankee Maine Yankee Pilgrim Planned or Under Construction Seabrook 1,2 Millstone 3 Charlestown 1, 2 Montague 1, 2 Sears Island (Maine) Pilgrim 2

36 Yankee Rowe First Commercial Nuclear Plant in New England

37 Yankee Rowe Today

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39 Connecticut Yankee Today

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41 Maine Yankee Today The message is that the nuclear industry restores their sites back to natural conditions after years of operation What other industry does this?

42 Maine Yankee Spent Fuel All the high level waste for 25 years of operation! Message not a lot of waste to be disposed of in the repository

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44 Millstone 1, 2 and 3 Unit 1 - was shutdown

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46 Statistics Past Nuclear Generating Capacity 6,600 Mwe Today s Nuclear Capacity 4,448 Mwe Shutdown Capacity 2,260 Mwe Cancelled Capacity 8,050 Mwe Total NE generating capacity 30,600 Mwe Base Load Generation about 25,000 Mwe

47 Present Generation Mix Nuclear 14.9 % Hydro 11.1 % Coal 9.1 % Oil 9.1 % Alternatives 3.1 % (mostly refuse/bio) Natural Gas 52.6 % If all nuclear plants were built and not closed Nuclear 48 % Gas 20 %

48 Who Operates NE Nuclear Plants? Entergy From Louisiana Florida Power and Light Dominion Virginia No New England utilities operate nuclear plants unlike the past New England Power Central Maine Power Boston Edison Central Vermont Northeast Utilities PS of New Hampshire

49 Summary Fukushima was a natural disaster for which the plants were not designed. Operators did remarkably well given the conditions. US plants generally better prepared for such events due to 9/11 preparedness. Plant upgrades to deal with extreme external environmental events now underway avoiding Maginot Line solutions but built in flexibility

50 Questions Discussion

51 Nuclear Safety in the Northeast David Lochbaum Director, Nuclear Safety Project

52 UCS s and Nuclear Power Safety UCS has worked on nuclear power safety issues for nearly 40 years UCS s role is that of a safety advocate; neither for nor against nuclear power With very few exceptions, UCS views compliance with federal safety regulations to make nuclear power safe enough

53 Fukushima vs. Northeast Reactors All vulnerable to extended loss of power Northeast reactors implemented measures after 9/11 to make them less vulnerable to extended loss of power Every two years, Northeast reactors test onsite and offsite emergency plans designed to protect the public in event of an accident

54 Fukushima Lessons NRC has identified nearly 3 dozen lessons from its Fukushima In March 2012, NRC ordered plant owners to implement the first of those lessons NRC s plan is to implement lessons within about 5 to 10 years Safety IOUs protect no one

55 24 U.S. operating reactors in the Northeast

56 9 U.S. shut down reactors in the Northeast

57 21 U.S. operating reactors in the Northeast reported leaks of radioactively contaminated water

58 NRC regulations do not permit a single drop of radioactively contaminated water to be released, except via monitored and controlled pathways. If you ve ever paid a nickel for an overdue library book, you ve paid 5 more than NRC fined the U.S. nuclear industry for over 100 violations involving millions of gallons of unlawful leakage.

59 UCS s recommendation: The NRC s regulations on discharges from nuclear power plants set the safety bar. NRC must ensure ALL reactors hurdle this safety bar, not continue to limbo beneath it.

60 5 U.S. operating reactors in the Northeast do not meet NRC s fire protection regulations

61 Approximately one-half of the core damage risk at operating reactors results from accident sequences that initiate with fire events. Jack Grobe, Assistant Director for Engineering and Safety Systems, NRC in presentation to the Commission on July 17, 2008

62 In other words, the fire hazard is rough equal to ALL OTHER HAZARDS COMBINED. And that high hazard assumes compliance with all fire protection regulations. The situation only gets worse when reactors operate outside of the fire protection regulations.

63 UCS s recommendation: The NRC s fire protection regulations set the safety bar. NRC must ensure ALL reactors hurdle this safety bar, not continue to limbo beneath it.

64 13 U.S. operating reactors in the Northeast store too much spent fuel in elevated pools

65 BWR Spent Fuel The fuel for boiling water reactors (BWRs) is in the form of uranium dioxide pellets stacked inside hollows tubes made of zirconium metal. Dozens of fuel rods are used to make a fuel assembly, also called a fuel bundle. Fuel bundles reside in the reactor core for three operating cycles (6 years).

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67 The spent fuel pool at most BWRs is inside the reactor building several floors above the ground.

68 Brookhaven National Laboratory examined spent fuel pool risk for the NRC in this 1997 study

69 Brookhaven considered four scenarios Case 1 Case 2 Case 3 Case 4 With 3,300 bundles in spent fuel pool, complete draindown 12 days after reactor shutdown causes fire that propagates across the entire pool inventory With 3,300 bundles in spent fuel pool, complete draindown 12 days after reactor shutdown causes fire limited to only last full reactor core (764 bundles) With 3,300 bundles in spent fuel pool, complete draindown 1 year after reactor shutdown causes 50 percent of the fuel rods to fail due to overheating With 3,300 bundles in spent fuel pool, partial draindown 12 days after reactor shutdown causes all fuel rods in last full reactor core (764 bundles) to fail due to overheating

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71 PWRs don t have this situation

72 New BWRs don t have this situation

73 Moving the spent fuel pools outside BWR reactor buildings is not practical. BUT moving spent fuel assemblies from the spent fuel pool to dry storage is practical. Very practical.

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76 Fukushima s Unlearned Lesson Dry Cask Storage Facility

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79 UCS s recommendation: Except for spent fuel discharged from the reactor core within the past 5 to 6 years, all spent fuel should be placed in dry storage where it is safer and more secure.

80 Summary Chernobyl and Fukushima are costly reminders that one bad day at a nuclear plant can offset years of good days. NRC s aggressive enforcement of safety regulations being a nuclear Robocop is the public s best protection against nuclear bad days.

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