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Fukushima: Public SafetyWill it be Like Chernobyl?

There are big differences. Chernobyl was a totally different reactor design without a containment vessel at all. The

reactor itself exploded and the graphite in the reactor then burned. The Fukushima reactors have not themselves

exploded, do not contain any flammable graphite, and have two layers of containment. Given the fundamental

differences between these reactors and Chernobyl, and also that several days have now passed since the start of the

accident, it is very difficult to see any way in which a Chernobyl-like explosion will occur.

Is it Harmful to Health?

The amounts of radioactivity dispersed off site so far are

really very small and will not add significantly to the

radiation exposure arising from natural sources. If things

get significantly worse, then that could change and this is get significantly worse, then that could change and this is

why the Government has ordered evacuation of the

population up to 20 km from the plant. This seems a wise

precaution, particularly as travel may well be difficult due

to earthquake/tsunami damage and it might be

impossible to evacuate in a hurry.

Radiation Doses and effects provided by the World Nuclear Association

Radiation Dose Effect

2 millisieverts per

year (mSv/yr)

Typical background radiation experienced by everyone

(average; e.g. 1.5 mSv in Australia 3 mSv in North America

[see Figure 1]).

Up to 5 mSv/yr Typical incremental dose for aircrew in middle latitudes.

9 mSv/yr Exposure by airline crew flying the New York – Tokyo polar

route.

15 mSv single

dose

Effective dose of a CT scan of the abdomen and pelvis.

20 mSv/yr Current limit (averaged) for nuclear industry employees.

50 mSv/yr Former routine limit for nuclear industry employees. It is

also the dose rate which arises from natural background

levels in several places in Iran, India and Europe.

100 mSv/yr Lowest level at which any increase in cancer is clearly

evident. Above this, the probability of cancer occurrence

(rather than the severity) increases with dose.

1000 mSv single

dose

Causes (temporary) acute symptoms, also known as

radiation sickness. These include nausea and decreased

white blood cell count, but not death. Above this, severity of

How are the Volatile Radioisotopes Being Managed?

The most effective way to protect people from radiation is to

move them away from it, this is why the area surrounding the

Fukushima plant has been evacuated to a radius of 20 km.

The Japanese Ministry of Education, Culture, Sports, Science

and Technology (MEXT) is responsible for monitoring the dose

outside of the exclusion zone in order to ensure evacuation to

this distance is sufficient.

As previously stated, iodine-131 is one of the first

radioisotopes to breach containment in a loss of coolant

incident due to its high volatility. The physiology of iodine is

such that it accumulates in the thyroid, a tissue prone to

cancers. This is a hazardous combination as the significant

increase in thyroid cancers in children following the

People and animals alike are monitored on leaving the exclusion zone to ensure

that they are free of contamination.

Figure 1: Graph of the

average annual doses

from natural radiation sources in a variety of

countries. Notice how the

total amount of radiation and the sources releasing

it vary dramatically

between countries due to changes in local geology

and global location.

Provided by World Nuclear Organisation.

white blood cell count, but not death. Above this, severity of

illness increases.

5000 mSv single

dose

Would kill about half those receiving it within a month.

References

• www.world-nuclear.org , Chernobyl Accident.

• World Nuclear News, Regulation and Safety.

On the Fukushima site itself, radiation doses are much

higher and, in some places at some times, they are too

high to allow workers to stay in the area. That is why, on

occasion, workers have been evacuated from the site, and

the workforce is being used in short shifts to limit their

exposure. Their exposure will also be monitored carefully.

Considering the persistent levels of radiation observed on

site (between planned venting events), acute symptoms

are unlikely (‘radiation sickness’) , but any radiation

exposure brings an increased risk of illness like cancer in

later life. The risk can be related directly to the radiation

dose, and this is why the workforce doses are monitored

so closely, to ensure that they do not incur an

unacceptably high risk. The doses away from the site carry

negligible risk of such illness, below one in a million.

increase in thyroid cancers in children following the

Chernobyl incident demonstrates1. On the 12 March, the

Japanese government began to distribute non-radioactive

potassium iodide supplements to citizens2. These

supplements prevent accumulation of iodine-131 in the

thyroid by ensuring the body contains all the iodine it needs,

so any iodine-131 inhaled/ingested is quickly excreted, rather

than accumulated.