Fukushima I.ppt - Wikispaces by xiuliliaofz

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									  Fukushima I
The 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    Japan Ministry of Land, Infrastructure and Transport, 1975




BWR facts                                                                                     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:




                                     235U
                                     236
                                      141Ba
                                       92Kr




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 Oxide
                        Fuel
                       Pellet
                                      Ceramic (UO2)
                                      (Typical)



           Typically
approximately 1cm
     tall by 0.75cm
           diameter




                                DOE
Zirconium Alloy
       Cladding
 (Zirconium, Tin, and
           Niobium)
                        Fuel
                        Rod
                        (Sizes vary by design)
Fuel
Bundle
(Quantities
vary by
design)




              DOE
Fuel
Group
(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
                                                 VAPOR
                                               CONDENSATE




                                                COOLING
                            TURBINE
                                                 TOWER
                  CORE




                   PRIMARY LOOP       SECONDARY LOOP
Physical layout                                             19
1. Reactor pressure vessel
2. 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.)


Defense in depth                 20
                      CORE




Suppression Systems          21
Overview
  Multiple systems exist to help
  cool an overheating reactor.     ADS
  Collectively, they are called
  the ECCS – Emergency Core                Main Feed
  Cooling System.                  HPCI      LPCI

                                   HPCS      LPCS
  They consist of a series of




                                    SLCS
  water sprays and injection
  pipes.
        In order, they are:
              HPCI
              HPCS
               ADS
              LPCS
              LPCI
              SLCS
HPCI                                                   23
                                  ADS
  Essentially delivers
  pressurized water via pipe to           Main Feed
  the pressure vessel.            HPCI      LPCI

                                  HPCS
  Goal: Increase reactor water              LPCS




                                   SLCS
  level.




HPCS                                                  24
                                   ADS
  A pressurized spray of water
  above reactor vessel pressure            Main Feed
  used to directly cool the fuel   HPCI      LPCI
  elements.                        HPCS      LPCS




                                    SLCS
  Goal: Decrease fuel
  temperature.




ADS                                                    25
                                   ADS
  Pressure release valves and
  piping used to vent                      Main Feed
  pressurized steam and gas        HPCI      LPCI
  from the pressure vessel into    HPCS      LPCS
  the suppression pool.




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




LPCS                                                   26
                                    ADS
  Delivers direct spray of water
  at low pressure onto fuel rods.           Main Feed
  Capable of higher flow rate       HPCI      LPCI
  than HPCS.                        HPCS      LPCS




                                     SLCS
  Goal: Decrease fuel
  temperature.




LPCI                                                    27
                                     ADS
  Delivers massive amounts of
  water at low pressure into the             Main Feed
  pressure vessel.                   HPCI      LPCI

                                     HPCS
  Goal: Flood the reactor core.                LPCS




                                      SLCS
  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.


SLCS                                                     28
                                    ADS
  Injection of neutron absorbent
  solution, such as boron, into             Main Feed
  the reactor to douse fuel         HPCI      LPCI
  elements.                         HPCS      LPCS




                                     SLCS
  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.

SCRAM                                                   29
Defined
                  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.




Scram procedure                                                          31
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
                                                 TURBINE
3. Feedwater pumps to full
   Direct steam into heat exchanger for
   condensation and cooling               CORE
4. Continue cooling core
   Using external power, keep
   feedwater pumps running to cool
   the core.



Segue                                                      32
                  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.




What went wrong                                                         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     Lost during earthquake due to
          (Utility Power)                  damage.


        Diesel generators
                                     Destroyed by tsunami.
       (Backup generators)

                                Designed to last only eight hours.
        Lead-Acid Batteries
                                Exhausted. Unable to cool reactor
       (Emergency batteries)
                                    independently long-term.

       No additional supplies
                                     Cooling system failure.
             available




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. Shown
    here is a pellet of plutonium. It is glowing
    red-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
core
Contd                    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
                     NRC




                                         JRC image

Cooling a Meltdown         NRC graphic          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
   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
The seawater option                                           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
  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.

Fuel pools                                                    59
      DOE




TMI   60
      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.

                                                                DOE
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.
Trying anything                                                  61
Defined
         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.




Pressure venting                                                  63
                        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.
Seawater                                                              64
                        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.
Boric acid                                                            65
                        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.




Aerial water                                                          66
                  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.


Water cannons                                                      67
                          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.


Entombment                                                            68
                         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.



Segue                                                              69
         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.




Radiation releases                                                  70
Defined
Radioactive materials escaped containment at Fukushima I in
                        three ways:
                    •Deliberate venting
             •Containment failures/explosions
                           •Fire




Venting                                                  72
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.



Containment failure            73
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.
Fire                         74
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.
Segue                           75
   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.




Types of Radiation                                         76
             Ionizing radiation takes four forms.
            Alpha particles (2 protons, 2 neutrons)   Can be stopped by any
Alpha       emitted at high speed.                    rudimentary shielding, including

   α        Causes severe genetic damage.
            Particularly harmful when ingested.
                                                      human skin and plain paper.


            Electrons and positrons emitted at        Requires heavier shielding, but
Beta        high speed.                               aluminum foil is sufficient.

   β        Can cause moderate genetic damage
            and burns.
            Can create incidental gamma radiation
            (positron annihilation).
            Electromagnetic radiation. Very high      Very difficult to shield
Gamma       energy.                                   conventionally. Barium, lead,

  γ         Causes some genetic damage.               and depleted uranium most
                                                      effective, but thick shielding is
                                                      often necessary.
            Neutrons emitted at high speed.           Water-dense materials make
Neutron     Creates additional radiation emissions    most effective shielding, but
            upon striking matter.                     creation of incidental gamma
            Destroys hydrogen bonds.                  radiation requires additional
                                                      protection.
            Lethal at high levels.
Dosimetry
                                                                                      77
  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 rem
Dosage levels                                                   78
       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.


Rad sickness                                                          79
                      Acute Radiation Syndrome
                              Note: Effects are cumulative
                                                                        Best / Worst
       Dose        ARS                          Prominent
                                                                         Survival
     Threshold    Severity                       Effects                   Rates
           1 Sv                    Nausea, headache, some present          100%
                    Mild
    (1,000 mSv)                    “nuclear tan.”                           95%
                                   Bleeding (external and internal),
                                                                           100%
           2 Sv   Moderate         hair loss. At 3 Sv, skin loss
                                                                            50%
                                   begins.
                                   Moderate shock, blood pressure
                                                                           100%
           6 Sv    Severe          instability, vomiting, diarrhea,
                                                                            50%
                                   disorientation.
                                   Rapid incapacitation (less than
                                                                            0%
           8 Sv   Extreme          10-15 minutes). Fever. Severe
                                                                        Up to 48hrs
                                   shock.
                                   Convulsion. Seizure. Respiratory
         30 Sv    Off Scale        arrest. Above 40 Sv, immediately         0%
                                   fatal due to molecular disruption.
                                                                         NIH, DOE
Dose samples                                                                        80
                                   A banana (potassium) 0.1 μSv
                    Exposure
                     Single
                                           Dental X-Ray 5 μSv
                                               Chest CT Up to 18 mSv
                                     Nuclear power plant
                                                         ~1 μSv/year
                                              emissions
                                       Coal power plant
                    Exposure




                                                        ~3 μSv/year
                    Ongoing




                                             emissions
                                    Average background
                                                         ~2.5 mSv/year
                                               radiation
                                Maximum Chernobyl level
                                                        4 Sv/min
                                            (core area)
                                      March 15 IAEA site 400 mSv/hr
                                                 reading (0.4 Sv/hr)
                    Fukushima
                    Exposures




                                       Emissions during
                                                          10 mSv/hr
                                              Unit 4 fire
                                       Highest recorded 1 Sv/hr
                                          radiation level (1,000 mSv/hr)

Types of Exposure                                                          81
                         Radiative       Contact       Ingestion




                         α   β   γ   α     β       γ   α   β   γ
Principal Contaminants                                             82
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.




I-131                                                            83
                                                   Release
                                                  Confirmed
                            Beta emitter
                           Half-life: 8 days
                                 Effects
                Settles in thyroid, causing malignancy
         or necrosis (in high doses). Higher risk for children.
                             Found In
                Leafy vegetables (spinach), tap water
                        Preventive Measures
                       Iodine therapy (tablets)
CS-137                                                            84
                                              Release
                                             Confirmed
                        Beta emitter
                    Half-life: 30.17 years
                           Effects
Uniform body distribution, with slightly higher concentrations
in muscles. Can result in malignancy and radiation poisoning
          (radiation sickness) in significant doses.
                          Found In
              Water, Particulate contamination
                    Mitigation Measures
              Prussian blue chelation treatment
SR-90                                                       85
                                                   Release
                                                  Confirmed
                             Beta emitter
                          Half-life: 28.8 years
                                 Effects
         Deposits in bones, similar to calcium. Causes leukemia
                       and/or osteomalignancies.
                                Found In
                    Water, Particulate contamination
                          Mitigation Measures
                                  None.
PU-239                                                            86
                                                Release
                                             Very Possible
                                             New leaks discovered
                           Alpha emitter        on March 25th
                   Half-life: 24,000 years ±200
                              Effects
    Inhalation or ingestion causes extreme risk of malignancy.
                    Lung cancer most common.
                            Found In
                Water, Particulate contamination
                      Mitigation Measures
                              None.
Gases                                                               87
•Xenon: 133Xe and/or 135Xe, gaseous
•Nitrogen: Several possible isotopes, gaseous
•Argon: 37Ar and/or 39Ar, gaseous




Has affected                                    88
•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.

What will happen                                              89
Intro
 Even assuming that nothing else goes wrong from this point
  on, there are several likely outcomes from the accidents at
                           Fukushima I.




Reactors                                                   91
                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.


Turbines                                                             92
                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.
Generators                                                            93
                 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.




Units 5&6                                                            94
             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.


Site                                                        95
                 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.
Misconceptions                                                        96
                 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.
Misconceptions                                                           97
Defined
  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.




Reactor v bomb                                                99
                                               ≠
    British Nuclear Group Ltd.



      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.

Chernobyl
                                 Fuel doesn’t have enough “kick.”    100
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       Soviet Ministry of Electrical Power and Electrification

piece of Chernobyl within
them.

Ronald Reagan                                                                              101
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.




Can it happen                                                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
                        Containment Methodology
                     Fukushima I        US Standard
              1. Fuel rod cladding            1. Fuel rod cladding
                (Zircaloy shielding)            (Zircaloy shielding)
              2. Reactor pressure vessel      2. Reactor pressure vessel
               (15cm 316L stainless steel)       (15cm 316L stainless steel)
              3. Containment structure         3. Primary containment
               (Incomplete, 1m thick concrete)    (2.5cm steel plate)
                                              4. Containment structure
                                                 (1.2-2.4m thick concrete,
                                                               complete shell)
                                              5. Missile shield
                                                 (1m thick concrete)

Reactor map                                                                      105
                                               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.

TMI                                                          106
Ultimately, nuclear power has distinct advantages and
          disadvantages as a power source.




                                                        108
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.


                                                             109
Generally, nuclear power has the ability to be very beneficial.




                                                             110
      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.

                                                             111
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.




                                                           112

								
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