Radioactive Iodine detected in Tokyo Water
Tokyo Metropolitan Gvt. told Tokyo citizens not to
give babies water containing iodine with radioactivity
of 210 Bq/kg-water. This was detected at 9:00, 23 March
at the water supply plant at Kanamachi.
Do not worry
It is not a fear, because half-life time of radioactive
iodine is as short as 8 days. Also detected radioactive
level is so low.
Radioactive iodine is produced in a N-power reactor
as a fission product. It decayed in to stable xenon-131,
emitting beta-line (electron beam).
Capability of emitting beta-line is degraded by half
in almost 8 days. It disappears immediately.
So, this is not a threat.
Relation between N-reactor accident
Where does iodine-131 come?
Iodine-131 was produced during atomic reaction
in the N-power station. While cooling capability
had been lost, fuel skin made of Zr-alloy was
reacted with water, and then hydrogen was produced
and leaked into the building. Also, iodine-131 was
estimated to be with hydrogen.
On explosion iodine-131 was emitted from the building
and transported to air. This iodine-dust was
solved into rain and fell down to the
water source area of Tokyo Metro. Gov., i.e.
along the Tonegawa-river and so on.
Let me remind you again. N-fuel is now contained
in a pressurized vessel, a container and a
container made of concrete and is cooled by water.
Fission will no more take place, as long as it is water cooled.
Radiation detected around the reactor shows stable level.
Also water was supplied into a container for
used fuel. Situation will not be worse.
What does radioactivity level of 210 Bq/kg mean?
Tokyo Metropolitan Gov. detected radioactivity level of
210 Bq/kg. Is it dangerous or safe?
People enjoy bathing at a radioactive hot spring,
such as Masutomi hot spring. According to data book
"Rikanenpyou" edited annually by the National Astronomical
Observatory of Japan radioactivity level is 11000 Bq/kg-water.
People enjoy bathing and even drink for his/her health.
This is as stronger as that detected in this morning
at the Kanamachi water supply plant.
For further learning radioactive iodine-131,
see the following site: http://en.wikipedia.org/wiki/Iodine-131.