Fukushima IFukushima IThe World’s First Triple MeltdownThe World’s First Triple Meltdown

We will be covering a large amount of content in varying degrees of complexity. Some information is indeed highly complex and detailed.

The volume and type of information may be overwhelming at times.

Unfortunately, nuclear operations are themselves extremely complicated, and understanding what has happened and is happening at Fukushima necessitates covering “foundation

information” to provide context and reference.

While every effort has been made to keep to a reasonable level of detail, please understand that the decision to include information was made based on its necessity to understand the “macro view”

whilst avoiding unnecessary detail. There are many levels of “micro view” beyond what we will cover today.

Questions are very welcome.

Overview 2 2

In the interests of focus, this presentation’s primary interest is in what happens within a nuclear power generation facility. Thus, we do

not address what happens downstream to the electricity that is produced. The processes of distribution and consumption are

themselves highly detailed, and there was concern that this would inject unnecessary confusion. Truly, the concepts behind the power

grid are a lesson all their own.

I will be happy to explain those concepts either individually or as a standalone presentation.

Overview 3 3

Today, we will explore:

•How nuclear fission works, fuel is assembled, and a typical nuclear power plant like Fukushima I is configured.

•The emergency systems used to stop a reactor in trouble

•What sequence of events led to the accidents at Fukushima I

•What has happened within the reactors

•The definition and implications of a nuclear meltdown

•What measures have been taken at Fukushima I and their efficacy

•What radioactive materials have been released, how much radiation “is around,” and what it can mean to persons exposed

•The various misconceptions about Fukushima and nuclear accidents in general

•The likelihood of a similar accident occurring here

Fukushima Facts 4

Construction started: 1967-1973

Commissioned (online): 1971-1976

Reactors: 6

Reactor type(s): Boiling water

Reactor manufacturer(s): GE, Toshiba, Hitachi

Owner/Operator: Tokyo Electric Power Co. (TEPCO)

Containment version: Mark I

Previous incidents (1971-2010): 3

BWR facts

Japan Ministry of Land, Infrastructure and Transport, 1975

5

•Typically abbreviated BWR

•Simplest design – “Tea kettle” principle

•Two coolant loops: one primary (core) one secondary (cooldown)

•Uses light water as coolant

•Like any thermal power plant, including coal and oil, water is heated to produce steam. That steam is used to drive (spin) a turbine, which is connected to a generator. The generator converts that rotating mechanical energy into electrical energy.

Fission primer 6

•Reactors generate heat, and thus energy, through nuclear fission – the splitting of atoms.

•A nuclear chain reaction is made possible by the fissile properties of nuclear fuel:

235U236U92Kr141Ba

Nuclear fuel primer 7

•U235 is the fission fuel of the reactor, but only about 3%-4% of the fuel is fissionable (3-4% purity)

•U238 outnumbers U235 significantly and does not fission. Instead, it captures neutrons, slowing the reaction to a manageable level.

•Neutrons must also be slowed to be useful; many neutrons coming off of a fission reaction are generally moving too fast to “stick” to another U235. Thus, something to slow the neutrons, called a moderator, is required. In many reactors, this is a combination of zirconium alloy (which is neutron-transparent) and water.

Fuels 8

•Most nuclear power plants rely on uranium oxide fuel

•Uranium oxide powder is pressed with a binding agent then fired in a kiln to produce a non-porous ceramic with a high melting point

•Fukushima I Unit 3 was converted to use MOX fuel.

•Short for Mixed OXide, MOX is a combination of uranium and plutonium – usually from dismantled nuclear weapons. The usual ratio is 7% plutonium to 93% uranium. MOX is very toxic and highly dangerous in the event of an accident.

Fueling 9

Uranium OxideCeramic (UO2)(Typical)

Fuel Pellet

DOE

Typically approximately 1cm

tall by 0.75cm diameter

FuelRod

(Sizes vary by design)

Zirconium Alloy Cladding

(Zirconium, Tin, and Niobium)

FuelBundle

(Quantities vary by design)

DOE

FuelGroup

(Quantity and configuration vary by design)

Neutron-Absorbent Control Rod(typ. Boron Carbide)Placement, configuration, quantity and composition vary by design.

Control rods

Core dynamics 17

Plant overview 18

VAPORCONDENSATE

CORE

TURBINECOOLINGTOWER

PRIMARY LOOP SECONDARY LOOPPhysical layout 19

Defense in depth

1. Reactor pressure vessel2. Drywell

3. Suppression Pool

4. Containment Building

5. Spent Fuel Pool

(Supporting equipment such as pumps, steam and water lines, steam turbines, and generators not shown.)

20

CORE

Suppression Systems 21

Overview

HPCI

Multiple systems exist to help cool an overheating reactor. Collectively, they are called the ECCS – Emergency Core Cooling System.

They consist of a series of water sprays and injection pipes.

In order, they are:HPCIHPCSADS

LPCSLPCISLCS

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

23

HPCS

Essentially delivers pressurized water via pipe to the pressure vessel.

Goal: Increase reactor water level.

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

24

ADS

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

A pressurized spray of water above reactor vessel pressure used to directly cool the fuel elements.

Goal: Decrease fuel temperature.

25

LPCS

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

Pressure release valves and piping used to vent pressurized steam and gas from the pressure vessel into the suppression pool.

Goal: Decrease reactor pressure to enable functioning of low-pressure systems.

26

LPCI

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

Delivers direct spray of water at low pressure onto fuel rods. Capable of higher flow rate than HPCS.

Goal: Decrease fuel temperature.

27

SLCS

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

Delivers massive amounts of water at low pressure into the pressure vessel.

Goal: Flood the reactor core.

This is the biggest response possible. LPCI is designed to literally flood the core and can deliver at least 40,000 gallons per minute of water to the core…provided there is power to the pumps.

28

SCRAM

Main FeedMain Feed

LPCILPCI

SL

CS

SL

CS

LPCSLPCSHPCSHPCS

ADSADS

HPCIHPCI

Injection of neutron absorbent solution, such as boron, into the reactor to douse fuel elements.

Goal: Absorb free neutrons and “poison” the reactor.

If the SLCS is activated, the reactor is ruined and will require replacement. However, by this point, it’s assumed that a critical failure has already occurred.

29

Defined

Scram procedure

In an emergency, reactors are designed to be able to shut down quickly.

This procedure is called a scram.

Its purpose is to stop the nuclear chain reaction as much as possible, isolate sections of the system,

and place the reactor into a safe configuration.

In the event of a scram, several things happen quickly under automatic control.

31

Segue

CORE

TURBINE

1. Main Steam Isolation Valve (MSIV) closes Prevent exit of radioactive materials from core. Turbines slow, generators stop.

2. Bypass line opens Direct steam into heat exchanger for condensation and cooling

3. Feedwater pumps to full Direct steam into heat exchanger for condensation and cooling

4. Continue cooling core Using external power, keep feedwater pumps running to cool the core.

32

What went wrong

As with all reactor systems, there are backups and safeties even for the scram procedure. Safe reactor

design requires that, above all else, the reactor should be able to reach a safe condition.

33

The two accidents

The Fukushima I incident actually involved two separate, but linked, accidents:

1. Loss Of Outside Power (LOOP)

2. Loss Of Coolant Accident (LOCA)

Of these, it is the LOOP accident that is at the root of the problem. From the LOOP, all other problems

followed.

LOOP steps 35

CORE

Scram

CORE

LOOP

CORE

Gen

CORE

Sequence overview

Electrical Grid Power (Utility Power)

Lost during earthquake due to damage.

Diesel generators (Backup generators)

Destroyed by tsunami.

Lead-Acid Batteries (Emergency batteries)

Designed to last only eight hours. Exhausted. Unable to cool reactor

independently long-term.

No additional supplies available

Cooling system failure.

LOCA 40

Decay heat 41

Many people do not understand how, if the control rods are inserted and the reactor turned “off,” the reactor continues to generate heat.

All fissile materials are radioactive, meaning they are constantly undergoing decay and giving off particles. Some of these particles are neutrons, which stimulate decay in other atoms, and so on until all atoms decay down to lead.

Radioisotope thermoelectric generators (RTGs) use this heat to produce power on space probes. Shownhere is a pellet of plutonium. It is glowingred-hot from the heat of its own decay.

Reactor fuel is no different.

Decay heat problems DOE 42

Decay heat contributed to damage in two locations:

The reactor cores

The spent fuel ponds

Reactors like Fukushima 1-4 can require up to 72,000 gallons of water per day for 3-4 days to cool decay heat.

Results 43

LOCA results

With core cooling systems offline, several things began to happen:

1. Core fuel began to overheat

2. Zirconium-alloy fuel rod cladding began overheating

3. Excess steam was generated as remaining coolant boiled off, driving up core pressure

4. Hydrogen gas began to evolve and accumulate

Thus, each failure created additional problems (a “cascade scenario”).

Hydrogen evolution 45

1. Fuel begins overheating due to failure to remove decay heat by inadequate or completely missing coolant.

2. What coolant is left is rapidly converted to steam. Pressure within the vessel rises.

3. The overheated zirconium fuel cladding reacts with the steam:

Zr + 2 H2O → ZrO2 + 2 H2 + Heat

Hydrogen gas is produced and begins to accumulate.

Hydrogen sequence 46

Thus, hydrogen gas was generated in the core.

This caused the pressure inside the reactor’s pressure vessel to rise to dangerous levels, beyond capacity of the safety systems.

To avert a pressure vessel rupture, the decision was made to vent steam from the coreContd 47

Hydrogen was vented into the drywell, but began to disperse through the building when flare systems failed. As a buoyant gas, it collected in the space above the reactor, within the building shell but outside containment.

This is where the first hydrogen explosion occurred, blowing the top off of the building shell.Segue 48

This same sequence occurred at reactors 1, 2, and 3 at Fukushima I.

Officially, hydrogen is the cause of all of the explosions at the reactors. If this is true, it means that the Zircaloy fuel rod cladding has been at extremely high temperature for days as

it continues to produce large amounts of hydrogen.

Consequently, this means that all three reactors have almost certainly suffered meltdown.

Meltdown 49

Defined

The word “meltdown” is frequently misused by the public.

A meltdown does not mean a loss of containment, nor does it mean an explosion. A meltdown can result in either or both of

these, but does not necessarily involve either.

In technical terms, a “meltdown” occurs when enough thermal energy builds up in the core to cause the fuel

assembles to pass their melting point and begin to melt down.

That’s all.

Of course, that is bad by itself, and is indicative of a severe breakdown, but is not a catastrophe for the wider

environment.

TMI 51

Cooling a Meltdown NRC graphic

JRC image

NRC

52

Cooling a reactor that is undergoing meltdown is difficult. It’s the mashed potato problem: since the fuel is now in a lump, the outsides will cool while the inside remains very hot. This

can cause fuel to form globular lumps within the core.

Ideally, melted core components will be contained by the reactor pressure vessel. Should pressure vessel integrity be lost while the reactor is still under pressure, the molten core

material will be blown out with force through the breach.

There is no evidence that this has happened at Fukushima I, but the possibility exists.

ECCS failures 53

The seawater option

With all of the combined ECCS components, it is difficult to see how Fukushima I went out of control. However, a series

of failures each contributed to the accident.

HPCI Power failure, Torus overheat

HPCS Power failure, Suppression pool burst at Unit 3

ADS Operated manually

LPCS Insufficient water, Power failure

LPCI Insufficient water, Pump failures

SLCS Questionably effective

54

The choice, therefore, to use seawater to cool the reactors showed just how serious the accident already was.

Using seawater in a nuclear reactor means that the reactor will never again be useable; it must be decommissioned and

scrapped.

By injecting seawater into the cores from the start, TEPCO effectively implied that there was no way to save the plant from the start, and that preventing a much larger disaster was the only possible course of action; keeping the plant

operational was impossible regardless of any other outcome.

Reactor 3 55

Much has been made over the status of the Unit 3 reactor, especially in light of the recently discovered evidence of

serious, uncontrolled leaks. But little has been said as to why this is such a concern.

Reactor 3 is nearly identical in design to the other three affected units. Recall, however, that it uses an unusual fuel

called MOX.

MOX, which contains plutonium, is significantly more toxic and radioactive that standard uranium oxide fuel. Therefore, even a small leak from a MOX-fueled reactor can have more dire consequences than larger leaks from normal reactors.

Segue 56

Unsurprisingly, most public attention focuses on the state of the reactors. We are conditioned by news, movies, and

games to look at a reactor’s core as the most dangerous component, and the source of all potential trouble.

Unfortunately, this isn’t the case.

Spent fuel 57

Defined

Fuel pools

As previously mentioned, even when a reactor is shut down, the fuel continues to produce heat due to normal radioactive

decay.

Fuel is typically removed from a reactor when it reaches an established level of “burn,” meaning that only a given

percentage of its starting reactivity remains.

This fuel, called “spent fuel,” must be stored underwater for a period of 1-5 years as decay heat continues to be produced. This storage location is called a spent fuel pool, or SFP. The

amount of fuel, its storage conditions, and even the geometry of the fuel bundles must all be carefully considered and

maintained to avoid criticality, or the resumption of a fission chain reaction.

59

TMI

DOE

60

Trying anything

The fuel stored in an FSP must remain immersed in water, and that water requires constant cooling.

If the water is not cooled, it is heated to the boiling point and begins to boil off. The steam will be radioactive.

Should the water boil down or leak out to the point where the fuel rods become exposed, the rods will begin to overheat, just as they would in the reactor. However, the SFP is not sealed like the reactor pressure vessel, meaning that radiation can escape far more easily.

DOE

61

Defined

Pressure venting

The failure of the ECCS created a nearly unprecedented problem.

Operators and engineers have tried numerous procedures to bring the problems at Fukushima to a close. Each procedure

targeted a specific problem and had varying degrees of success.

63

Seawater

Pressure Venting Target: Reactor Cores, Units 1-3

Purpose: Relieve reactor core pressure, enable use of low-pressure cooling systems

Success: Successful, but released radiation.

This was a classic Catch-22. On the one hand, high and climbing core pressure not only prevented injection of low-pressure water, but also threatened to burst containment systems. But venting steam and gas released radioactive materials. In the end, there really was no other option, though; the pressure had to be released or the risk of a far greater catastrophe increased.

64

Boric acid

Seawater Injection Target: Reactor Cores, Units 1-3

Purpose: Adding water for cooling

Success: Not bad, better than doing nothing.

While the addition of seawater into the reactor cores did drive temperatures down somewhat, it created new problems. First, the reactors are now hopelessly contaminated and cannot be reused. Seawater has also increased corrosion problems and has destroyed several cooling pumps. Additionally, accumulation of salt left behind when the water evaporated has created a new thermal blanket around the fuel, making cooling more difficult.

65

Aerial water

Boric Acid Injection Target: Reactor Cores, Units 1-3

Purpose: Introduce neutron absorber to “poison” fuel

Success: Unknown.

Boric acid solution has been part of the critical response menu for decades, but has never really been applied in a situation like this. There is currently no hard data one way or the other for its effectiveness, but it can’t hurt to add borax to the cooling water.

66

Water cannons

Helicopter Water Bombing Target: Spent Fuel Pools, Units 3 and 4

Purpose: Cool unshielded, unwatered spent fuel

Success: Failure.

News reports implied that helicopters were dumping water “into the reactors,” but the targets were the spent fuel pools, which had gone dry in some cases, and nearly so in others. Due to high radiation levels, helicopters had to do their drops at high altitude, and very little water actually hit the pools, not nearly enough to do any good.

67

Entombment

Water Cannons Target: Spent Fuel Pools, Units 2-4

Purpose: Cool unshielded, unwatered spent fuel

Success: Somewhat, better than nothing.

Hitting the spent fuel pools with ground-based riot police and fire-department water cannons is difficult at best, but some water has gone into the cooling pools.

The problem now facing responders is that the SFP on Unit 4 is not holding water, leading to the belief that the pool has cracked or otherwise developed a leak.

68

Segue

Entombment Target: Reactor Buildings, Units 1-4 definite, Units 5 and 6 possible

Purpose: Seal contaminated site

Success: Planned.

Ultimately, it is likely safest to construct a permanent “sarcophagus” similar to the one shielding Chernobyl-4 around, at minimum, Fukushima I 1-4. Units 5 and 6 also sustained damage, but not nearly as much. Their fate is open to question.

69

Radiation releases

In the meantime, there have been significant releases of radiation from the site.

These releases have come from various sources and have been of varying compositions and levels of intensity.

70

Defined

Venting

Radioactive materials escaped containment at Fukushima I in three ways:

•Deliberate venting

•Containment failures/explosions

•Fire

72

Containment failure

When reactor pressure climbed to dangerous levels, the decision was made to vent pressurized steam and gas from the reactor to avoid rupturing containment.

This is similar to what was done at TMI. But, while TMI only vented once, all of the Fukushima reactors have vented many times each.

73

Fire

It is probable that the series of explosions (hydrogen or otherwise) have damaged the containment. Specifically, the containment plugs may be dislodged or damaged.

Additionally, Unit 3’s suppression pool pressure readings have been at atmospheric for days, indicating the suppression torus has ruptured and vented.

74

Segue

In almost all nuclear accidents to date, the worst contamination is caused by fire. This includes Chernobyl.

A fire in the reactor core is unlikely unless the damage is far more severe than reported. Instead, fires in the spent fuel are far more likely, and have the potential to be a far bigger disaster by releasing huge amounts of radioactive material.

75

Types of Radiation

While this explains how radioactive materials may have escaped, understanding what radiation is and what it does is

equally important to understanding the impact of these events.

76

Dosimetry

Ionizing radiation takes four forms.

Alpha

α

Alpha particles (2 protons, 2 neutrons) emitted at high speed.

Causes severe genetic damage.

Particularly harmful when ingested.

Can be stopped by any rudimentary shielding, including human skin and plain paper.

Beta

β

Electrons and positrons emitted at high speed.

Can cause moderate genetic damage and burns.

Can create incidental gamma radiation (positron annihilation).

Requires heavier shielding, but aluminum foil is sufficient.

Gamma

γ

Electromagnetic radiation. Very high energy.

Causes some genetic damage.

Very difficult to shield conventionally. Barium, lead, and depleted uranium most effective, but thick shielding is often necessary.

Neutron Neutrons emitted at high speed.

Creates additional radiation emissions upon striking matter.

Destroys hydrogen bonds.

Lethal at high levels.

Water-dense materials make most effective shielding, but creation of incidental gamma radiation requires additional protection.

77

Dosage levels

The SI unit for human radiation dosage is the Sievert (Sv). Rather than reflecting just the sheer level of radioactivity, like the Rad scale, the Sievert scale is concerned with radiation’s

effects on human bodies.

Sievert is also expressed using the metric equivalencies of milli- (mSv, 10−3 Sv) and micro- (μSv, 10−6 Sv).

Thus:

1 Sv = 1,000 mSv = 100,000 μSv

In the United States, the rem is more commonly used though it is not SI.

1 Sv = 100 rem78

Rad sickness

The effects of radiation exposure increase with dose and time:

•A short, low-level dose is often relatively non-harmful.

•A long, low-level dose can be mildly harmful.

•A short, medium-level dose can be mildly harmful.

•A long, medium-level dose can be hazardous.

•A short, high level dose is dangerous.

•A long, high level dose is deadly.

•A short, very high level dose is deadly.

79

Dose samples

Dose Threshold

ARSSeverity

ProminentEffects

Best / WorstSurvival

Rates

1 Sv(1,000 mSv)

MildNausea, headache, some present “nuclear tan.”

100%95%

2 Sv ModerateBleeding (external and internal), hair loss. At 3 Sv, skin loss begins.

100%50%

6 Sv SevereModerate shock, blood pressure instability, vomiting, diarrhea, disorientation.

100%50%

8 Sv ExtremeRapid incapacitation (less than 10-15 minutes). Fever. Severe shock.

0%Up to 48hrs

30 Sv Off ScaleConvulsion. Seizure. Respiratory arrest. Above 40 Sv, immediately fatal due to molecular disruption.

0%

Acute Radiation SyndromeNote: Effects are cumulative

NIH, DOE 80

Types of Exposure

A banana (potassium) 0.1 μSv

Dental X-Ray 5 μSv

Chest CT Up to 18 mSv

Nuclear power plant emissions

~1 μSv/year

Coal power plant emissions

~3 μSv/year

Average background radiation

~2.5 mSv/year

Maximum Chernobyl level (core area)

4 Sv/min

Sin

gle

Exp

osu

reO

ng

oin

gE

xpo

sure

March 15 IAEA site reading

400 mSv/hr (0.4 Sv/hr)

Emissions during Unit 4 fire

10 mSv/hr

Highest recorded radiation level

1 Sv/hr(1,000 mSv/hr)

Fu

kush

ima

Exp

osu

res

81

α β γ α β γ α β γPrincipal Contaminants

Radiative Contact Ingestion

82

I-131

In addition to simple particulates and chemical contaminants, three radioactive particulates are confirmed to have escaped,

with the possibility of a fourth. Additionally, radioactive gases have been vented.

The particulates are Iodine-131, Cesium-137, Strontium-90, and potentially Plutonium-239.

83

CS-137

Beta emitterHalf-life: 8 days

EffectsSettles in thyroid, causing malignancy

or necrosis (in high doses). Higher risk for children.

Found InLeafy vegetables (spinach), tap water

Preventive MeasuresIodine therapy (tablets)

ReleaseConfirmed

84

SR-90

Beta emitterHalf-life: 30.17 years

EffectsUniform body distribution, with slightly higher

concentrations in muscles. Can result in malignancy and radiation poisoning (radiation sickness) in significant doses.

Found InWater, Particulate contamination

Mitigation MeasuresPrussian blue chelation treatment

ReleaseConfirmed

85

PU-239

Beta emitterHalf-life: 28.8 years

EffectsDeposits in bones, similar to calcium. Causes leukemia

and/or osteomalignancies.

Found InWater, Particulate contamination

Mitigation MeasuresNone.

ReleaseConfirmed

86

Gases

Alpha emitterHalf-life: 24,000 years ±200

EffectsInhalation or ingestion causes extreme risk of malignancy.

Lung cancer most common.

Found InWater, Particulate contamination

Mitigation MeasuresNone.

ReleaseVery Possible

New leaks discovered on March 25th

87

Has affected

•Xenon: 133Xe and/or 135Xe, gaseous

•Nitrogen: Several possible isotopes, gaseous

•Argon: 37Ar and/or 39Ar, gaseous

88

What will happen

•Vegetables (spinach, broccoli, cauliflower, turnips)

•Milk

•Tap water

•Seawater

•Surrounding land (evacuation zone increased to 30km, “stay

indoors” zone changed to required evacuation on March 25th.)

•Ships at sea – USCG inspections have found elevated radiation levels on ships that were up to 400km away from the site…to the east.

89

Intro

Reactors

Even assuming that nothing else goes wrong from this point on, there are several likely outcomes from the accidents at

Fukushima I.

91

Turbines

Condition: Contain core materials that have at least partly if not completely melted down. Badly contaminated by seawater. Highly radioactive. Possibly ruptured by repeated explosions.

Probable Fate: Defueled as much as possible (if possible at all), then abandoned.

The reactor pressure vessels are both full of highly radioactive debris and are most likely damaged by explosions. Even if they were not, seawater contamination would prevent reuse.

92

Generators

Condition: Almost certainly warped. Radioactive contamination from normal operation.

Probable Fate: Abandonment.

Steam turbines operate at high speed. Consequently, even the slightest warp (a thousandth of a millimeter) can cause dangerous vibrations that can destroy the turbine and injure workers.

To prevent this, hot turbines are kept on a “turning gear” until they cool. Like a rotisserie, the turbines are spun at low speed to prevent gravity-induced warpage. Since there was no power to turn the turbines, they simply stopped while hot, and have almost definitely warped very badly.

93

Units 5&6

Condition: Unknown. Possibly contaminated by radioactive debris.

Probable Fate: Salvage.

The generators, housed in buildings separate from the reactor cores, may have escaped significant damage from the accident. Provided that they haven’t been contaminated, they could be broken down for transport elsewhere.

This assumes, however, that no earthquake, structural, fire, or water damage has already affected them.

94

Site

Condition: Reportedly stable.

Probable Fate: Uncertain.

Units 5 and 6 were not in operation at the time of the quake and tsunami, and have, according to reports, remained stable since. Units 5 and 6 are housed in a separate building from Units 1 through 4. Barring the discovery of damage during inspection, and provided that the buildings are not heavily contaminated, the reactors may be put back into service.

On March 20th, the announcement was made that the plant would be closed, but it was not made clear if Units 5 and 6 were included in that statement.

95

Misconceptions

Condition: Known to be heavily contaminated in some places. Severe structural damage to many buildings.

Probable Fate: Entombment.

Defueling of the TMI-2 reactor was possible due to the nature and degree of damage. In all likelihood, it will be prohibitively dangerous to try to defuel Fukushima I Units 1-4.

Once the cores are cooled, they will probably be sealed in concrete, then the buildings themselves sealed inside steel and concrete containment structures.

This plan has had vocal approval from several scientists, such as Michio Kaku.

96

Misconceptions

Condition: Emergency pumps, vehicles, and other equipment have definitely been contaminated.

Probable Fate: Decontamination where possible, entombment where not.

Objects near high radiation become radioactive themselves due to neutron absorption. From the SL-1 explosion in Idaho in 1963 to Chernobyl in 1986, the fact that objects can be unsalvageably contaminated has been encountered repeatedly.

If decontamination is economically not viable, any contaminated equipment will likely be sealed in with the reactors.

97

Defined

Reactor v bomb

Few things seem to scare the public as much as the specter of radiation and nuclear power. Largely this is because it is

not well understood.

This breeds many misconceptions.

99

Chernobyl

≠A reactor cannot go “mushroom cloud” even in the worst

accident.

Reactor fuel-grade uranium is 3-4% pure.Weapons-grade uranium is 90+% pure.

Fuel doesn’t have enough “kick.”

British Nuclear Group Ltd.

100

Ronald Reagan

The Chernobyl disaster was caused by a massive steam/hydrogen explosion within the reactor itself that blew apart the core. This started a massive graphite fire that caused much of the radioactive release from the plant and worldwide contamination.

Everybody carries a little piece of Chernobyl within them.

Soviet Ministry of Electrical Power and Electrification

101

Can it happen

It is true that the USS Ronald Reagan was forced to move by higher-than-normal radiation levels detected aboard ship. It is also true that the radiation was caused by fallout from Fukushima I. However, while the average dose equaled the dose expected over a course of a full month, the ship is not hopelessly contaminated and the crew is not considered at risk.

102

Defined

The short answer is yes.

We have a number of nuclear power plants in seismic and tsunami hazard zones. Thus, the potential exists for an

incident at one of these plants.

However, most American nuclear facilities adhere to higher safety standards for construction and containment.

Furthermore, all facilities are required to have evacuation plans and alert systems online, understood, and regularly

tested.

Most significantly, though, nuclear power plants in this country use much more durable construction, adding several

layers to the Defense In Depth model.

US defense in depth 104

Reactor map

Containment Methodology

Fukushima I US Standard1. Fuel rod cladding

(Zircaloy shielding)

1. Fuel rod cladding

(Zircaloy shielding)

2. Reactor pressure vessel

(15cm 316L stainless steel)

2. Reactor pressure vessel

(15cm 316L stainless steel)

3. Containment structure

(Incomplete, 1m thick concrete)

3. Primary containment

(2.5cm steel plate)

4. Containment structure

(1.2-2.4m thick concrete, complete shell)

5. Missile shield

(1m thick concrete)105

TMI

DOE

In the United States, the Department of Energy has licensed 104 reactors for operation.

35 are boiling water reactors similar to those at Fukushima I.

The rest, 69, are pressurized water reactors, or PWRs, which employ still greater levels of safety redundancy.

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Ultimately, nuclear power has distinct advantages and disadvantages as a power source.

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The only carbon emissions are from transport of ore and fuel, as well as some processing steps.

Nuclear power plants do not affect air quality, contribute to smog, or induce respiratory problems.

The total footprint of nuclear power is small: uranium mines are not strip mines like coal; uranium ore is not hazardous

when spilled like oil; and nuclear fuel refineries are compact.

Nuclear power plants typically need refueling infrequently, and even then only a third of the fuel is replaced.

By using MOX fuel, the nuclear proliferation risk of dismantled weapons can be reduced by redirecting weapon

materials into power generation.

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Generally, nuclear power has the ability to be very beneficial.

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However, accidents at nuclear power plants are disproportionately serious when compared to other thermal plants. While oil and coal plants can suffer fires, the risk of

long-term harm is slight.

Only rare accidents like the TVA coal fly-ash slurry spill in 2008 cause “lump sum” releases. Combustion at these plants does release harmful materials, but not in continuously high

levels.

Additionally, waste products from thermal plants are more easily handled and remediated than waste from nuclear

power. A typical reactor produces up to 30 tons of high-level radioactive waste per year, mostly as spent fuel. Even with the best, as-yet un-fielded technology, waste will require

isolation from the environment for up to 300 years.

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With currently approved handling procedures, nuclear waste must be isolated for up to ten million years as it progresses

through the various stages of nuclear decay.

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