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-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of ludwik kowalski
Sent: Saturday, March 12, 2011 6:43 PM
To: Forum for Physics Educators
Subject: [Phys-l] Eartquaque in Japan
Below is a message from a nuclear physicist friend in Japan
Ludwik
==========================================
Serious rescue efforts for isolated people in destroyed towns by
tsunamis and quake are under way.
Another serious concern is of the stopped nuclear power plants,
Fukushima-I $II with 8 reactors total.
The Fukushima-I#1, 40 years old, has got the first trouble after its
automatic shut-down by the quake, which was caused by no electricity
(an emergent Diesel generator did not work
either) for driving circulation pumps of cooling water.
Consequently, decay heat of U-fuel pins could not be cooled enough and
temperature and steam pressure inside the reactor vessel elevated
continuously. Finally the melt-down of reactor-core fuel started to
happen, as detected by Cs and I activities outside as the emergency
value of reactor vessel gas was opened to decrease the elevated steam
pressure. It happened an explosion, by mixing hydrogen-gas (generated
by H2O + high-temperature-metal interaction inside reactor) and oxygen
gas at the outside of the reactor steel-container, which destroyed the
concrete walls of the #1 plant building.
The reactor container vessel and reactor vessel were looked not
damaged.
TEPCO (Tokyo Electric Power Corp.) and NISA (Nuclear and Industrial
Safety Agency) decided to fill the inside and out-side of reactor
vessel with sea-water adding borated acid to cool the reactor. The work
was done. Radioactivity monitors outside showed decrease of radiation
level to about ten times of natural BG, which was about several 100
times just after the emergency gas-valve opening. Now the reactor is
confined stable. Citizens inside 20 km radius were evacuated for
safety.
(I think, the usage of sea water, emergent use, was chosen by two
reasons: 1) not enough pure-water was not available at the site, 2)
NaCl contained in sea water, as well as added borated acid (B-10) has
significant thermal-neutron absorption effect which may help avoiding a
worst criticality accident of fallen debris of melt U-fuels into water
pool of container vessel, if happened.)
Probably the Fukushima-I#1 reactor will be closed
(disassembled) in near future. But we still need careful watching what
will be going on.
Now it is aired that Fukushima-I#3 reactor has got a similar trouble.
They might do similar treatment, not decided yet.
Ludwik
http://csam.montclair.edu/~kowalski/life/intro.html