Subject: Fukushima Update 4-27 - Slow Arduous clean
up
From: Chris in Delaware
Date: Tue, 26 Apr 2011 21:11:09 -0400
1.
CORE
DAMAGE Estimate - Unit 1 70%, Unit 2 30%, Unit 3 25% Unit 4 *(Total Core
Off-Load into its Spent Fuel Pool), Unit 5 and Unit 6 No damage. It is Believed that U1, 2, and 3 Reactor
Vessels have Damage, however it is unknown exactly where and what the extent of
the Damage is.
2.
Containment
Integrity - Unit 1 Estimated to be intact Damaged, U2 Damaged, U3 Estimated to
be Not Damage, U4,5 No Damage. Due
to Unit 1 Reactor Vessel Level and Pressure oddities, we now believe that Unit
1 Containment is breached.
3.
Reactor
Pressure/Temperature - Unit 1 RISING (over 850F - Instrumentation is Suspect),
U2 and U3 UNKNOWN. NOTE: [We discussed that the Reactor Vessel
Instrumentation is Not Available or very unreliable]
4. Spent Fuel Pool Status -
U1,2,3,4 - Cooling with Fresh Water Spray [not very effective according to a
Sandia Report],
I
believe ALL Damaged Fuel. Further, U4 had Hydrogen Explosion (this Unit had
total Core Offloaded into its Spent Fuel Pool).
Unit 4 Spent Fuel Pool continues to lose water
RAPIDLY (See Article Below in RED) - Because this Unit was in Refueling Mode,
the seals around the Reactor Head are leaking. Conjecture on my part, but the
Fuel Pool concrete may be leaking. It was damaged by the hydrogen explosion.
●Radioactive water level unchanged at No.2
reactor. The operator of the troubled
Fukushima Daiichi nuclear power plant says the level of radioactive water in a
tunnel at the No.2 reactor is unchanged.
Comment
- Unit 2 containment is still damaged, however. The leakage still entering the
Turbine Building from the Containment Building.
●TEPCO prepares to fill No.1 reactor with
water. Remote-controlled robots are
being used to look inside one of the disabled reactor buildings at the
Fukushima Daiichi nuclear plant, before workers begin pumping more water into
the reactor. Tokyo Electric Power
Company is planning to fill the No.1 reactor and then its container with water
by mid July, to submerge the fuel rods and cool them down stably. To prepare for the operation, TEPCO sent
robots inside the reactor building on Tuesday morning to check for leakage and
other damage. If no problems are found,
the utility plans to increase the amount of water being fed into the reactor on
Wednesday, on an experimental basis.
The water feed is due to be increased from the
current 6 tons per hour to a maximum of 14 tons. Workers will monitor changes in temperature and pressure, to see
whether the reactor container can safely hold the water.
Robots will then enter the building again, to check
for signs of seepage.
The government's nuclear safety agency says TEPCO
also needs to determine whether a water-filled reactor container can withstand
strong aftershocks.
TEPCO hopes to fill up the No.1 and No.3 reactor
containers by mid-July, as part of its recently announced schedule for
containing the nuclear accident.
Comment
- Unit 1 reactor is damaged. With all the water already pumped in it, it should
be full. Leaks ALWAYS show up sooner or later though.
●Government was unaware of hydrogen explosion
risk
An advisor to Prime Minister Naoto Kan says no one
in the government knew of the risk of a hydrogen explosion in the initial
stages of the emergency at the Fukushima Daiichi nuclear plant.
The disclosure was made on Monday by Goshi Hosono,
who is a governing party lawmaker and senior member of the government's nuclear
taskforce.
Hosono referred to a hydrogen blast that shattered
the No.1 reactor building one day after the March 11th earthquake and tsunami. The
blast occurred after workers began venting air from the reactor containment
vessel to reduce pressure inside.
Hosono said he was not aware of a single nuclear
expert who warned of the risk of a hydrogen blast following the venting
operation. He said nitrogen inside the reactor container was supposed to
prevent such explosions.
Plant operator Tokyo Electric Power Company also
told reporters that hydrogen is supposed to be processed within the containment
vessel, and that such an explosion is not assumed in a reactor building.
Large amounts of radioactive substances were
released into the environment as a result of the hydrogen blast.
Comment
- This one surprised me too. I should have known. The bottom line is that the
government doesn't know - much.
●Radioactive water in No.3 and 4
reactors rises
The operator of the disaster-hit
Fukushima Daiichi nuclear power plant says the level of radioactive water has
risen in the Number 3 and Number 4 reactors.
The levels of radioactive water in the
power plant are hampering efforts to restore its functions. Tokyo Electric
Power Company, or TEPCO, is moving highly radioactive water from the tunnel of
the No. 2 reactor to a temporary storage facility.
The utility company says the water
level in the tunnel of the No. 3 reactor rose to 99 centimeters below the
surface as of 6 PM on Monday. That passes the level at which TEPCO plans to
remove the water, but it has yet to secure storage space.
The water level in the basement of the
No.3 reactor's turbine building also rose by 10 centimeters over 3 days.
TEPCO says a survey last Thursday found
an increase in the density of radioactive substances in the water in the
basement of the No. 4 reactor's turbine building.
The company says the levels of cesium-134
and 137 increased about 250-fold and iodine-131 increased about 12 times
compared with one month ago.
TEPCO says contamination of this level
requires them to prioritize the transfer or disposal of the water.
The water level in the No. 4 reactor's
turbine building rose by 20 centimeters in 10 days.
TEPCO says water used to cool the No. 3
reactor could be leaking into No. 4 as their turbine buildings are connected.
●Monitoring rising temperatures Unit
4 Spent Fuel Pool
The operator of the troubled Fukushima Daiichi nuclear power plant
is carefully monitoring the situation at the Number 4 spent fuel pool, where
the water temperature is rising despite increased injections of cooling water.
Tokyo Electric Power Company, or TEPCO,
says it will inject 210 tons of water into the pool on Monday, after finding on
Sunday evening that the temperature in the pool had risen to 81 degrees
Celsius.
The utility firm had earlier limited the
amount of water being injected into the pool to 70 tons a day, saying the
weight of the water could weaken the reactor building, which was already
damaged in last month's hydrogen explosion.
On
Friday, TEPCO found that the pool's temperature had reached 91 degrees, so it
began injecting 2 to 3 times the amount of water.
TEPCO says the pool's water temperature
dropped to 66 degrees on Saturday after water was injected, but started to rise
again, to 81 degrees.
The operator says the water level in the
pool was 2.5 meters lower than normal after 165 tons of water were injected on
Sunday. It is carefully monitoring the water level and temperature to avoid
further troubles.
The Number 4 spent fuel pool stores 1,535
fuel rods, the most at the nuclear complex.
●Heat exchanger for No1 reactor considered
The Tokyo Electric Power Company is thinking about
setting up a heat exchanger to hasten the full-scale recovery of the cooling
system at the Number 1 reactor of the Fukushima Daiichi nuclear power plant.
TEPCO says 70 percent of the fuel is apparently
damaged and
6 tons of water per hour is being injected into the reactor.
In order to cool it under more stable conditions,
TEPCO wants the water level in the containment vessel to reach the height of
the fuel rods. At present, the water
level is estimated to be about 6 meters from the bottom of the containment
vessel.
Two plans have been considered to cool the vessel,
one uses sea water, the other air. To
avoid the risk of further damage from possible aftershocks TEPCO is favoring
the water system. It says the pipes
which connect the containment vessel and the heat exchanger must be quake
protected. In addition, radioactive substances must be removed before pouring
contaminated water into the heat exchanger.
These tasks should be done inside the nuclear reactor building but as
the level of radioactivity is too high for human entry, many problems remain
before the heat exchanger can be set up.
●TEPCO discloses radiation map
Tokyo Electric Power Company has disclosed a map of
radiation levels at the damaged Fukushima Daiichi nuclear plant.
The utility plans to urgently remove radioactive
rubble, and the map will help to protect workers from unnecessary exposure to
radiation.
TEPCO began making the map in late March, and has
posted copies in the plant's buildings.
The map shows radiation levels that controllers
measured around the first 4 reactors before the start of the working day.
Radiation levels around the Number 3 reactor
building, which was damaged by a powerful hydrogen explosion, are higher than
in other locations, and 300 millisieverts per hour of radiation was detected in
debris on a nearby mountainside.
Work started on April 6th to remove contaminated
rubble, which had been obstructing the restoration process. TEPCO says much of the debris around the
former office building has been removed, and it has started clearing the rubble
around the Number 3 and Number 4 reactors.
Enough debris has been removed to fill 50 containers, and it is being
kept in a field on the mountainside.
The radiation levels one meter away are 1 to 2
millisieverts per hour.
●Quake protection considered for
No.4 reactor
The operator of the Fukushima Daiichi
nuclear power plant is studying ways to increase earthquake resistance of the
spent fuel pool at the No. 4 reactor.
The walls of the reactor building supporting the pool were severely
damaged by an explosion on March 15th.
TEPCO is examining footage taken by an
unmanned helicopter. The company plans to install several concrete pillars on
the floor below that will support the bottom of the pool.
The company says the radiation level
on the floor is not immediately dangerous to human health, but that it needs to
determine whether long hours of work are possible there.
The pool has the most fuel rods at the
plant and a large amount of water has been evaporating. The company has been
injecting water into the pool to prevent the rods from being exposed and
further damaged.
But there is concern that the weight
of the water might cause further damage to the reactor building. From Saturday,
the utility has been assessing more carefully the appropriate amount of water
to be poured by using a device to monitor temperature and the level of cooling
water in the pool.
TEPCO says it will try to start the
reinforcement construction as soon as possible because further strong
aftershocks may occur.