aps power point anatomy of a meltdown final

8/6/2019 APS Power Point Anatomy of a Meltdown FINAL

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Title and abstract before Friday, March 11, 2011 at 2:46 p.m. Japan time:

Used Nuclear Fuel: From Liability to BenefitRaymond L. Orbach

Energy Institute, The University of Texas at [email protected]

www.energy.utexas.edu

Nuclear power has proven safe and reliable, with operating efficiencies in the U.S. exceeding 90%. Assuch, it ideally provides a carbon-free source of electricity (with about a 10% penalty arising from theCO2 released from construction and the fuel cycle). However, used fuel from nuclear reactors is highlytoxic and presents a challenge for permanent disposal -- both from a technical perspective and from a

policy perspective. The half-life of the bad actors is relatively short (of the order of decades) whilethe very long lived isotopes are relatively benign. At present, spent fuel is stored on-site, in coolingponds. Once the used fuel pools are full, the fuel is moved to dry cask storage on site. Though the localstorage is capable of handling used fuel safely and securely for several decades, the law requires theDOE to assume responsibility for the used fuel and remove it from reactor sites. Under this law, thenuclear industry pays a tithe that is to support sequestration of usedfuel (but not research). However,there is currently no national policy in place to deal with the permanent disposal of nuclear fuel. Thisadministration is opposed to underground storage at Yucca Mountain. There is no national policy forinterim storageremoval of spent fuel from reactor sites and storage at a central location. And there is

no national policy for liberating the energy contained in used fuel through recycling (separating out thefissionable components for subsequent use as a nuclear fuel). Therefore, a Blue Ribbon Commissionhas been formed to consider alternatives, but will not report until 2012. This paper will examinealternatives for used fuel disposition, their drawbacks (e.g. proliferation issues arising from recycling),and their benefits. For the recycle options emerge as viable technologies, the nuclear chemistryprogram in the U.S. needs to be revitalized; research is required to develop cost effective methods fortreating spent fuel, with attention to policy issues as well as technical issues.

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Title and abstract after Friday, March 11, 2011 at 2:46 p.m. Japan time:

Anatomy of a (partial) meltdown: Fukushima

Daiichi Nuclear Power PlantsRaymond L. OrbachEnergy Institute, The University of Texas at Austin

[email protected]

www.energy.utexas.edu

Chronology of Events (from CNN):

Friday, March 11, 2011: 2.46 p.m. (0.46 a.m. ET/5.46 a.m.GMT): A magnitude 9.0 earthquake strikes an area 370

kilometers (230 miles) northeast of Tokyo, Japan, at a depth of24.5 kilometers. The offshore quake, the fifth largestworldwide since records began, sparks a major tsunamiwarning across the Pacific. Within an hour a wall of water upto 9 meters (30 feet) high hits the Japanese coast, sweepingaway towns and villages in its path.

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Event Initiation (from NEXTera ENERGY, Duane Arnold)Event Initiation (from NEXTera ENERGY, Duane Arnold)

The Fukushima nuclear facilities were

damaged in a magnitude 8.9 earthquake onMarch 11 (Japan time), centered offshore ofthe Sendai region, which contains the capitalTokyo. Plant designed for magnitude 8.2 earthquake.

An 8.9 magnitude quake is 7 times in greater inmagnitude.

Serious secondary effects followed includinga significant tsunami, significant aftershocksand a major fire at a fossil fuel installation.

The Fukushima nuclear facilities were

damaged in a magnitude 8.9 earthquake onMarch 11 (Japan time), centered offshore ofthe Sendai region, which contains the capitalTokyo. Plant designed for magnitude 8.2 earthquake.

An 8.9 magnitude quake is 7 times in greater inmagnitude.

Serious secondary effects followed includinga significant tsunami, significant aftershocksand a major fire at a fossil fuel installation.


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Fukushima Daiichi Nuclear Station (from NEXTera ENERGY, Duane Arnold)Fukushima Daiichi Nuclear Station (from NEXTera ENERGY, Duane Arnold)

Six BWR Mark I units at the Fukushima Nuclear Station:

Unit 1: 439 MWe BWR, 1971 (unit was in operation prior to event)



Unit 4: 760 MWe BWR, 1978 (unit was in outage prior to event)



Six BWR Mark I units at the Fukushima Nuclear Station:

Unit 1: 439 MWe BWR, 1971 (unit was in op

eration prior to event)






Unit 1


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Timing of Reactor Events (D.V. Rao and Patrick McClure)

Earthquake Begins Fri. 2:46 PM JSTReactor shuts down Fri. 2:48 PM JST

Off-grid, diesels provide power Seconds later

Reactor cooled by emergency systems After diesels start

Tsunami fails diesel generators Fri. ~3:45 PM JST

Battery powers control of steam-driven Reactor CoreIsolation Cooling (RCIC) and automatic depressurization

After diesels fail

Battery power exhausted Sat. ~12:00 AM JST

Report of suppression pool (wet well) becoming saturated Sat. ~2:00 AM JST

Containment pressure 0.6 MPa (0.4 MPa normal) Sat. ~2:00 AM JST

Steam vented from reactor to Refueling Bay Sat. 5:30 AM JST

Water level drops to top of active fuel -

Core oxidation occurs, releasing hydrogen -

Hydrogen Explosion/Deflagration Sat. 3:36 PM JST

Seawater injection begins Sun 8:20 PM JST

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Chronology of Events (cont.):

Friday, March 11 8.15 p.m.: The Japanese government declares an emergency at Fukushima Daiichi power plant.

10.30 p.m.: Authorities reveal the cooling system at the plant is not working, and admit they are"bracing for the worst."

Saturday, March 12

2.06 a.m.: Radiation levels in the No.1 reactor at Fukushima are reported to be rising.

3.24 a.m.: Japanese trade minister Banri Kaieda warns that a small radiation leak could occur at theplant.

6.45 a.m.: TEPCO says radioactive substances may have leaked at Fukushima. Japan's Nuclear andIndustrial Safety Agency says radiation near the plant's main gate is more than eight times thenormal level.

4.19 p.m.: Japan's Nuclear and Industrial Agency reveals a small amount of radioactive cesium hasescaped from the power plant, possibly caused by a fuel rod melting.

EXPLOSION: 6.22 p.m.: A hydrogen explosion at Fukushima's reactor No.3 blows the roof off thecontainment structure around the No.1 reactor and injures four people -- two plant workers andtwo subcontractors.

8.18 p.m.: Residents living within 20 kilometers of the plant are told to evacuate the area. Some200,000 people leave.

8.54 p.m.: Authorities insist no harmful gases were emitted as a result of the explosion at theFukushima plant, blaming the blast on "water vapor that was part of the cooling process."

10.35 p.m.: Radiation levels around the plant fall as officials prepare to flood the containmentstructure around the reactor with sea water to cool it. Meanwhile, authorities prepare to distributeiodide tablets to residents near the damaged nuclear plant to prevent radiation poisoning.

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Chronology of Events (cont.): Sunday, March 13

3.20 a.m.: Three people randomly selected from a group of 90 test positive for radiation exposure inFukushima prefecture.

5.37 a.m.: Japanese authorities say Saturday's explosion at the Fukushima Daiichi plant occurred outsidethe primary containment vessel, adding that the vessel's integrity has not been compromised.

4.46 p.m.: Chief Cabinet Secretary Yukio Endo warns of the possibility that a second explosion couldhappen at the No.3 reactor.

Monday, March 14

EXPLOSION: 11 a.m.: Hydrogen explosion at the No.3 reactor damages the cooling system at the No.2reactor and injures 11 people, including employees, subcontractors and four civil defense workers. A wallat the plant collapses as a result of the blast, but officials say the containment vessel surrounding thereactor remains intact. Authorities begin pumping a mixture of sea water and boron into the No.2 reactorto cool its nuclear fuel rods. Those residents living within 20 kilometers of the plant who have so farignored evacuation orders are warned to stay indoors. Up to 2.7 meters of the No.2 reactor's control rodsare left uncovered because the pump which keeps them cool has run low on fuel after being leftunattended. It causes them to heat up generating radioactive steam.

Tuesday, March 15

EXPLOSION: 6 a.m.: An "explosive impact" rocks the No.2 reactor -- the third blast at the plant in four days-- and damages its suppression pool.

7 a.m.: The U.S. Navy begins repositioning ships and planes after detecting low-level "airborneradioactivity" in the region. Three people on the U.S.S. Ronald Regan earlier tested positive for low levelsof radiation.

8.30 a.m.: Chief Cabinet Secretary Yukio Edano says he cannot rule out the possibility of a meltdown at allthree of the plant's damaged reactors. He says radiation levels at the plant have increased to "levels thatcan impact human health", and warns anyone living within 20 and 30 kilometers of the plant to remainindoors. Almost all of the plant's staff, about 800 people, are evacuated from the site, with just 50remaining to carry out emergency operations.

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Chronology of Events (cont.): FIRE: 8.54 am: Fire breaks out in a cooling pond used for nuclear fuel at the No.4 reactor -- which had been shut down

before Friday's quake. Japanese Prime Minister Naoto Kan warns that "there is still a very high risk of further radioactive

material coming out," but urges the public to remain calm. The government imposes a no-fly zone within a 30-kilometer

radius of the plant.

11 a.m.: The fire in No.4 reactor is reported to have been extinguished. The International Atomic Energy Agency reveals that

radiation levels at the plant have been recorded at 167 times the average annual dose of radiation, but that level is expected

to drop quickly.

11.10 p.m.: The IAEA reports that Monday's blast at reactor No.2 "may have affected the integrity of its primary

containment vessel."

11.45 p.m.: TEPCO says it plans to use helicopters to pour water onto reactor No.4 in order to cool the nuclear fuel rods.

Wednesday, March 16

FIRE: 7 a.m.: The second fire in two days is discovered in the building of the No. 4 reactor at Fukushima Daiichi. This one is inthe northeastern corner of the building, an official with TEPCO says.

Thursday, March 17

4.35 a.m.: The U.S. Nuclear Regulatory Commission recommends that U.S. residents within 80 kilometers of the Fukushima

reactors evacuate the area.

5.00 a.m.: Gregory Jaczko, head of the NRC, tells U.S. Congress spent fuel rods in the No. 4 reactor have been exposed

because there "is no water in the spent fuel pool," resulting in the emission of "extremely high" levels of radiation. Japanese

Defense Minister Toshimi Kitazawa says a decision has been taken to address the crisis from the air and the ground -- despite

concerns about exposing workers to radiation -- with efforts to cool down the No.3 reactor the top priority. "We could not

delay the mission any further, therefore we decided to execute it," Kitazawa said.

9.48 a.m.: Helicopters operated by Japan's Self-Defense Forces begin dumping tonnes of seawater scooped from the Pacific

Ocean on to the No.3 and No.4 reactors to try to reduce overheating. But hours later, TEPCO tells Japan's Kyodo News the

operation does not appear to have lowered radiation levels in the area.

10.15 a.m.: The IAEA says two people are missing at Fukushima Daiichi, and another has suffered significant exposure to

radioactive material. Based on information supplied by Japanese authorities, it says two TEPCO workers have been injured,

along with two subcontractors, and that at least 20 people have fallen ill due to possible radiation contamination.

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Chronology of Events (cont.):

12.00 p.m.: TEPCO officials deny claims the spent fuel pool has run dry. "We have been able toconfirm that there is water in the spent nuclear fuel pool," a Tokyo Electric spokesman said. "Butwe do not know how much water."

3.00 p.m.: Australia urges its citizens living within 80 kilometers of the Fukushima plant toevacuate.

7.30 p.m.: Japanese Defense Ministry uses five water cannon trucks to shoot water into reactorNo.3 in another effort to prevent it overheating. The operation ends forty minutes later.Friday, March 189.30 a.m.: Japan's nuclear and industrial safety agency raises the crisis level from four to five,putting it on a par with the 1979 nuclear incident at Three Mile Island in Pennsylvania.The International Nuclear Events Scale says a level five incident means there is a likelihood of arelease of radioactive material, several deaths from radiation and severe damage to the reactorcore.

Saturday, March 19

9.00 a.m.: As searches for survivors continued, police in Japan said more than 7,100 people haddied since the monster earthquake and ensuing tsunami struck. On Saturday morning 7,197 peoplewere confirmed dead, according to Japan's National Police Agency. Another 10,905 people were

missing and 2,611 were injured, the agency said. 1.00 p.m.: Efforts accelerated Saturday to restore power to nuclear reactors' cooling systems at the

stricken Fukushima Daiichi plant. Officials said workers hope to fully restore power by day's endSaturday to plant's Nos. 1, 2, 5 and 6 reactors, and to get power up and running Sunday for the Nos.3 and 4 reactors.

7.27 p.m.: Japan's National Police Agency says 7,348 people are now confirmed dead and 10,947are missing. The agency said 2,603 people have been injured.

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BoilingWater Reactor


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Radiation LevelsRadiation LevelsHighest recorded radiation level at the Fukushima

Daiichi site was 155.7 millirem. Radiation levels weresubsequently reduced to 4.4 millirem after the after thecontainment was flooded. The NRCs radiation dose

limit for the public is 100 millirem per year.

How much is a millirem Eating one banana: 0.01 millirem Dental radiography: 0.5 millirem

Average dose to people living within 16 km ofThree MileIsland accident: 8.0 millirem; maximum dose: 100 millirem

Mammogram: 300 millirem Brain CT scan: 80500 millirem

Chest CT scan: 6001800 millirem

Gastrointestinal series X-ray investigation:1.4 rems

Threshold from DOE and French Academies studies:10 rems

Highest recorded radiation level at the Fukushima

Daiichi site was 155.7 millirem. Radiation levels weresubsequently reduced to 4.4 millirem after the after thecontainment was flooded. The NRCs radiation dose

limit for the public is 100 millirem per year.

How much is a millirem Eating one banana: 0.01 millirem Dental radiography: 0.5 millirem

Average dose to people living within 16 km ofThree MileIsland accident: 8.0 millirem; maximum dose: 100 millirem

Mammogram: 300 millirem Brain CT scan: 80500 millirem

Chest CT scan: 6001800 millirem

Gastrointestinal series X-ray investigation:1.4 rems

Threshold from DOE and French Academies studies:10 rems


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Summary Mark I Notes

Twenty-three reactors in the United States utilizing Mark Icontainments

Available data suggest similarities exist in the design andoperation of Japanese and U.S. Mark I containments

Immediate improvements:

Passive cooling system for spent fuel storage pools (air cooled heatexchangers)

Primary containment venting system that minimizes hydrogencombustion risk (design issues-distributive outlet, hardened vents;Hydrogen mitigation in the secondary containment building)

In-vessel retention of corium (lava-like molten mixture of portions of a

nuclear reactor, formed during a nuclear meltdown) Core catcher to mitigate ex-vessel core relocation, preventing corium-

concrete interactions (heat-absorbing, non-gas emitting, sacrificialmaterials, external natural circulation-cooled externally)

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What is next?

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Gen 3+ Systems:

GE Hitachi ESBWR (Economic Simplified Boiling Water Reactor)

Reduced core height, chimney above the core,tall, wide down corner (annulus for feed water toflow back down), promoting natural circulation,eliminating need for recirculation pumps

72 hours passive performance with no pumps andoutside intervention under accident scenario

corium (lava-like molten mixture of portions of anuclear reactor, formed during a nuclearmeltdown) retention/cooling system

25 percent of pumps, valves, and motors

eliminated from previous nuclear island designs Incorporation of features used in operationally

proven BWRs, including isolation condensers,natural circulation and debris-resistant fuel

Broad seismic design envelope

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Gen 3+ Systems:

Westinghouse AP1000

Passive core cooling system Safety injection and reactor coolant

Passive residual heat removal

Containment isolation Reduction of normally open

penetrations reduced by 50 percent Penetrations are normally closed

No recirculation of irradiated wateroutside of containment

Steel containment is high integrity steelpressure vessel, rather than a concretevessel

Passive containment cooling system

Control room habitability(pressurization, ventilation, andclimate control system) for 72 hourperiod

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General Atomics High Temperature

Gas Reactor

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Ceramic Fuel Particle and Graphite Block

are Basic Unit of Reactor

Fuel Kernel

Provides fission energy

Controls oxygen potential

Buffer layer (porous carbon layer)

Provides void volume forgaseous fission products and CO

Accommodates kernel swelling Attenuates fission recoils

Inner Pyrocarbon (IPyC)

Protects kernel from Cl attackduring SiC layer deposition

Reduces tensile stress in SiC

Retains gaseous fission products

Silicon Carbide (SiC) Primary load bearing member

Retains gaseous and metallicfission products

Outer Pyrocarbon (OPyC)

Reduces tensile stress in SiC

Retains gaseous fission products

Protects SiC from chemicalattack by coolant impurities

~1000 Qm855 Qm

Safety Feature: Containment

at the TRISO barrier


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HTGR: Required Safety Functions Not

Reliant on Long-Term Power

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Summary and Conclusions

There are lessons to be learned from the (partial) meltdown at theFukushima Daiichi Nuclear Power Plants for Mark I BWR (Boiling WaterReactors)

Passive cooling systems for spent fuel storage pools

Primary containment venting system that minimizes hydrogen

combustion risk In-vessel retention of corium (lava-like molten mixture of portions of a

nuclear reactor core, formed during a nuclear meltdown)

Moving spent fuel away from reactor sites (11,125 assemblies storedat Daiichi, ~ 4 times the in-core inventory)

Need for risk informed approach to response strategies

Quest for perfect outcome (saving the reactors, avoiding venting ofsteam with radioactive noble gases/entrained fission products ) mayhave created more negative consequences

Earlier start could have reduced fuel damage and/or prevented thehydrogen explosions initiated by high temperature cladding/steaminteraction

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aps power point anatomy of a meltdown final

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