#Danger of Losing Control of the Reactor Is Greater with MOX

Conventional LWRs are designed to decrease the reactivity when
the temperature rises. But when using Pu-239 as fuel, heating of
the core from an increase in reaction rate tends to increase the
reaction rate still further. This is called the positive
temperature coefficient of reactivity, meaning there is a danger
of losing control of the reactor by accelerated chain reaction of
fissioning.(10)

MOX spent fuel contains more fission products than uranium spent
fuel. The important factor in managing spent fuel is the heat
generation caused by the highly radioactive fission products.
Since spent MOX fuel contains much more fission products, the
heat generation from MOX spent fuel is twice as high as that of
spent uranium fuel after 10 years and three times as high after
100 years.(14)
Plutonium does not exist in the natural environment, and is only
produced in nuclear reactors. It is known as one of the most
toxic elements. It emits high energy alpha radiation, and has
harmful biological effects.

Alpha radiation has a very short range but very intense
ionization power. If exposed on the surface of the skin, the
skin works as a shield and will prevent its penetration into the
body, but all of its ionizing power will be focused on the small
spot, causing burns and killing the skin tissue. If inhaled
into the body, the alpha particle will go in through the
respiratory tract, and enter the lung. Due to its long
half-life, it will stay in the body permanently, emitting alpha
radiation, and killing the surrounding tissues by strong
ionization. If plutonium is taken into the body in soluble form
(e.g. plutonium nitrate) through food chain, it will enter the
blood stream, and into the bones, liver and genital organs where
it will be enriched. Alpha radiation leads to reactions in the
cells of living things. It can cause damage to the nucleus and
DNA of the cell, in effect causing genetic damage in descendants,
particularly if germ cells are affected.(15)
#Dangers of Resuspension in the Environment

In the event of a contamination of the environment with
plutonium, the whirling up and inhalation of plutonium particles,
known as resuspension, plays an important role. If there is a
road traffic, building work or cleaning work at the plutonium
contaminated site, plutonium can enter the body through the
respiratory tract. Generally, the more whirled up, the greater
the dose intake per quantity of plutonium on the ground. If
there is fire, and plutonium becomes airborne into fine aerosol
particles, plutonium contamination of the environment will extend
to a far larger scale, landing on ground, contaminating a vast
wider area. Plutonium remains effective over very long periods
affecting the health of the people and the environment.(16)
#Accident Scenario When Burning MOX

Accidents involving overheating and meltdown are possible in any
nuclear reactors. In such accidents, not only would readily
volatile noble gases, like iodine and caesium be released
to the environment, but a small portion of the actinides,
including plutonium and neptunium would be released. As the
activity of the actinides is substantially higher in the case of
MOX, the consequences of such severe accidents become more
serious.

When MOX fuels are used, the probability of having such serious
accidents or trouble would increase due to the high content of
plutonium in the fuel. Even if an accident is not a serious one,
it could become serious since even a small portion of the
inventory of actinides released to the environment could cause
significant radiological consequences.
#Accidents at Fabrication Plants

Accidents at MOX fuel fabrication plants have occurred. In June,
1991, the storage bunker of the MOX fuel fabrication plant in
Hanau, Germany was contaminated with MOX. It occurred after the
rupture of a foil for container packaging in the course of an
in-plant transportation process. Five workers were exposed to
plutonium. This accident was the main reason the fabrication
plant at Hanau was shut down.(19)

In November, 1992, a rod was broken through a handling error and
MOX dust released during the mounting of MOX fuel rods to fuel
assemblies in the fuel fabrication facility adjoining the MOX
facility in Dessel, Belgium.(20)

In event of such accidents, if the International Commission on
Radiological Protection (ICRP) recommendations for general public
exposure were adhered to, only about 1 mg of plutonium may be
released from a MOX facility to the environment. As a
comparison, in uranium fabrication facility, 2kg (2,000,000mg)of
uranium could be released in the same radiation exposure. A 1 mg
release of plutonium from a processing process can easily happen
from various smaller incidents.(21)
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Situaţia la centrala nucleară Fukushima continuă să fie gravă. Compania TEPCO a anunţat că presiunea la reactorul numarul 3 a crescut din nou