Problems at Fukushima Continue to Mount
by Nelle Maxey
Water leaks have proliferated around the site for the last couple of weeks.
Water lines (which are lying on the ground all over the site) and exposed pumps
for the water decontamination and reactor cooling systems have been freezing.
See here
for pictures and here
for layout with 14 leaks in layout map on Jan 29. See here
for layouts with latest leaks noted and pictures of leak "mitigation" (like a
tarp over the pump truck and light bulbs to heat the equipment. Just like my
neighbours do for their chickens.) ( http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120201_03-e.pdf)
This freezing was inevitable, but TEPCO has been scrambling to insulate
pipes and pumps and to stop the leaks. As further mitigation, TEPCO replaced the
flex pipe lines which were supplying decontaminated, recirculated cooling water
to Units 1, 2, and 3 with solid plastic pipe over the last couple of weeks.
In
the process, they have been changing the flow amounts into the reactors as I
showed in a chart for Unit 2 in a previous post. Lower flow amounts were
stabilized last week, but now Unit 2 is heating up, so water volumes have been
increased.
TEMPERATURE AT BOTTOM OF UNIT 2 RPV
The temperature at the bottom of the reactor pressure vessel (RPV) in Unit
2 has been rising for the last week. The latest published reading today says it
is at 71 degrees C.
The green line in today's plant parameter report
graph shows this temperature rise at the bottom of the RPV. The partly obscured
yellow line shows another RPV temperature measurement of the supporting skirt
which you can see is also rising.
The second page of this report shows the temperature reading chart. The 2
readings of interest are the ones labelled RPV Bottom Part (Wall Above
Bottom Head), RPV Supporting Skirt Upper Part. Both show rising temperature
readings.
For comparison, here are the temp readings on Jan 31 at 11:00 am and Feb 6
at 11:00 am as recorded on this chart over a 6 day period. The chart only
records two readings a day.
Bottom of RPV (green line)
Jan 31 shows 50.4C and Feb 6 shows 71.0C, a rise of 20.6 degrees.
RPV Supporting Skirt (yellow line)
Jan 31 shows 42.8C and Feb 6 shows 49.3C, a rise of 6.5 degrees.
SKF carried this story yesterday on the temperature rise at Unit 2:
“The data is not entered yet in TEPCO's plant
parameter page. The last measurement of the location - RPV Bottom Part - is at
11AM on February 5, at 68.6 degrees Celsius (as reported in the
previous post).
So it went up 3.1 degrees Celsius in 5
hours, the sharpest rise yet since February 1.
From Jiji Tsushin
(8:16PM 2/5/2012): [Japanese text removed, emphasis mine]
Reactor 2 RPV temperature at Fukushima I Nuke Plant risen above 70
degrees Celsius, TEPCO increases water injection
TEPCO
announced on February 5 that one of the thermometers on the bottom of the
Reactor Pressure Vessel of Reactor 2 at Fukushima I Nuclear Power Plant
registered 71.7 degrees Celsius at 4PM. The location is one
of several temperatures that [the company uses] to gauge the situation. The
temperature there has risen sharply since it registered 52.0 degrees Celsius
at 11PM on February 1. However, at two other locations at the same height, the
temperatures remain steady around 45 degrees Celsius. TEPCO is considering the
possibility of instrument failure, but in the meantime has increased the
amount of water injected into the reactor by 1 tonnes, to 9.6 tonnes/hour and
see if it makes difference.
The new safety regulation approved by the
Nuclear and Industrial Safety Agency after the March 11, 2011 accident
specifies that it is considered "deviation from operational limit"
when the temperature taken at the standard locations reaches 80 degrees
Celsius or the amount of injection water is increased by 1 tonnes per
day, and the local municipalities have to be notified. TEPCO is
planning the analysis of the gas inside the reactor in order to maintain the
"cold shutdown state" where the temperature remains 100 degrees Celsius and
lower and to prevent "recriticality" where the melted fuel starts nuclear
chain reaction.â€
Source: http://ex-skf.blogspot.com/2012/02/fukushima-i-nuke-plant-reactor-2-rpv.html
Today the government media, NHK, is carrying the story as well. Here is the
latest one with updated temperature data. There is a good short video at the
link showing a temperature data graph with the 73.3 degree high temperature
recording. Note the temperature is falling off at the time of this report, which
is the only good news about this development. Although the increased amounts of
cooling water being used to lower the temperature only adds to TEPCO's problems.
Currently they are injecting and spraying 10.4
cubic meters per hour into the reactor core. This is the highest volume I
have seen to date.
Attempts to cool the temperature in the No. 2
reactor of the disabled Fukushima Daiichi nuclear power plant have only
partially succeeded despite the injection of more cooling water.
The
temperature in the reactor has gradually risen from about 45 degrees Celsius
registered on January 27th.
In the past 4 days, the temperature has climbed
more than 20 degrees to above 70 degrees.
The plant operator, Tokyo
Electric Power Company began pumping more water into the reactor at around
1:30 AM on Monday. But at 7 AM, the temperature stood at 73.3 degrees and at 5
PM, 69.2 degrees.
The utility firm says 2 other thermometers elsewhere
in the reactor gave readings of about 44 degrees.
TEPCO says the rise
in temperatures indicate that the flow of water in the reactor may have
changed direction after plumbing work, and is no longer able to properly cool
down the melted down nuclear fuel.
However, the utility says
radioactive xenon has not been detected in gases around the reactor, and that
nuclear criticality is not taking place.
The government and TEPCO
announced in December that the 3 troubled reactors at the Fukushima plant had
reached a state of cold shutdown with their temperatures below 100 degrees.
But the situation inside the reactors remains unclear.
New regulations
established after the state of cold shutdown was achieved require the utility
to keep temperatures inside the reactors below 80 degrees.
TEPCO says it
will increase the amount of water being injecting into the reactor to see if
the temperature in the reactor drops.
The government's Nuclear and
Industrial Safety Agency says there is a need for a comprehensive study to
determine whether the reactor is actually in a state of cold shutdown. It says
a brief reading of over 80 degrees on one of the thermometers does not
necessarily mean there is trouble in the cooling system.
Meanwhile, the
Chairman of the Nuclear Safety Commission, Haruki Madarame, says that a
recurrence of nuclear criticality is unlikely.
But he criticized TEPCO
and the nuclear safety agency for their handling of the matter. He says they
are failing to properly explain the state of the reactors to the
people.
Monday, February 06, 2012 20:48 +0900
(JST)
You can see puffs of steam being emitted from Unit 2 in this
footage from the on-site video camera here.
DEVIATION FROM OPERATIONAL LIMIT
The deviation of the operational limit as described in the
press above is in terms of temperature increase above 80 degrees C OR an increase in amount of water injection by 1
tonne per day.
Under these conditions there is a deviation from operational
limit due to water injection increases in Unit 2.
Here are the calculations: 1 liter of water weighs (under
most conditions) one kilogram. 1 cubic meter equals 1000 liters. So 1 cubic
meter of water weighs 1000 kilograms = 1 metric ton (tonne)
There are other on-going problems at the
plant as well.
Unstable temperature at Unit 3
SFP
The spent fuel pool (SFP) at Unit 3 is increasing in
temperature according to the latest press
handout:
“Cooling of Spent Fuel Pools (As of 11:00 am on February 6)
Unit 3 28 degrees C
Unit 3 Note: Because the pool temperature began to
increase, at 9:55 am on February 6, we initiated the secondary
cooling tower.â€
Checking previous handouts
I see this temperature rise has been going on since Jan 31st.
The cumulative rise in temperature from Jan 30 to today, Feb 6, is 14.9
degrees.
I have noted theday over day temperature rise below.
The largest daily rises were actually between Jan 30 and Feb
1st. However, TEPCO is just noting this in today’s handout as they are
initiating the secondary cooling tower. Hopefully the temperature will continue
to decrease. But this means yet more water to deal with.
Feb 6 28C, +1.5 degrees
Feb 5 26.5C, + 1.8 degrees
Feb 4 24.7C, + 1.8 degrees
Feb 3 22.9C, + 2 degrees
Feb 2 20.9C, +1.9 degrees
Feb 1 19C, +2.9 degrees
Jan 31 16.1C, +3 degrees
Prior to this date the temperatures of the Unit 3 SFP where
between realtively stable in the 12 to 13 degrees C temperature range:
Jan 30 12.9C
Jan 29 11.9C
Jan 28 12.1C
Jan 27 12.3C
Jan 26 12.6C
One week earlier on Jan 19 13C
One week earlier on Jan 12 13C
Storage tanks leaks
Most of the water in the leaks discovered so far was not highly
radioactive as it was decontaminated for cooling. However, the leaks from
the storage tanks are a different matter. While the volume of water is very low,
the high radioactivity is the problem, especially for the workers.
There are 100 tanks for storing the highly radioactive water
from the reactor water desalination system and 3 of them have leaked recently.
The tanks unfortunately are bolted together rather than welded (due to the need
for haste in installing them on-site in the summer and fall). Picture of tanks
and leakage here
and here.
These leaks have both gamma and beta contamination at high levels (as stated in the press
handout on Feb 3)
22mSv/h of γ-ray [gamma] and 2000mSv/h of β-ray
[beta]
Why I said this is a problem for the workers is shown in this
information from wiki"
[emphasis mine]:
“Shielding from gamma rays requires large amounts of mass, in contrast to
alpha particles which can be blocked by paper or skin, and beta particles
which can be shielded by foil. They are better absorbed by materials with high atomic numbers and
high density, although neither effect is important compared to the total mass
per area in the path of the gamma ray. For this reason, a lead shield is only
modestly better (20–30% better) as a gamma shield, than an equal mass of
another shielding material such as aluminium, concrete, water or soil; lead's
major advantage is not in lower weight, but rather its compactness due to
higher density. Protective clothing, goggles and respirators can
protect from internal contact with or ingestion of alpha or beta particles,
but provide no protection from gamma radiation. Source: https://en.wikipedia.org/wiki/Gamma_ray
The gamma ray contamination
is to be expected in water pouring over the melted nuclear cores and then
concentrated in the desalination process. The leaks were fixed by tightening the
bolts on the tanks. Workers walking among the tanks and tightening the bolts are
exposed to this gamma radiation. Do workers have adequate protection? This is a
very serious problem especially considering the number of tanks storing this
highly radioactive nuclear waste water and the now needed constant inspection to
stay on top of the leaks. Short-term decision making when dealing with the
nuclear disaster are certainly not paying off.
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