Col·legues,<br>Passo informació de François Diaz-Maurin, de l'ICTA-UAB, ex-enginyer nuclear, que està fent una interpretació interessant, informativa i traductora del que va passant a Fukushima.<br>Us passo la informació des de la més recent a la més "antiga"... el boom d'informació a vegades fa antic allò que acaba de passar fa unes hores!!!<br>
Crec que pot ser d'interés per entendre detalls tècnics.<br>
Records i abraçades,<br>Pere<br><br><div class="gmail_quote">3) IMPORTANT: Situation at Fukushima 1 NPP worsens + Uncertainty on the radioactivity level<br> <br>Dear everybody,<br><br>I am very sad and sorry to have to send you again
another update about the nuclear crisis in Japan but the most recent
events at the Fukushima I NPP are very worrisome. To make things even
worse, it is really hard to get information about the current state of
the plant reactors. So my analysis is relying on what TEPCO is eager to
release.<br><br>
<br>
<b>Situation at Fukushima 1 NPP worsens:<br>
<br>
</b>There is now a cascade of problems ongoing at the plant site:<br>- a new hydrogen explosion at unit 3 this occurred morning, as it has already been the case at unit 1 on Saturday.<br>-
apparently unit 2 is also experiencing injection of sea water and boric
acid (BBC information, not confirmed by TEPCO to my knowledge), which
was only the case of unit 1.<br>
sources:
<a href="http://www.tepco.co.jp/en/press/corp-com/release/11031312-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031312-e.html</a> ;
<a href="http://www.tepco.co.jp/en/press/corp-com/release/11031402-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031402-e.html</a> ;
<a href="http://www.bbc.co.uk/news/science-environment-12726628" target="_blank">http://www.bbc.co.uk/news/science-environment-12726628</a><br><br>I want to
highlight again the difference between "shutdown" and "cold shutdown". A
rector is "cold shutdown" (completely off) only when the nuclear
fission reaction in the core is completely stopped. However, although
all 6 units of Fukushima I are "shutdown", units 1 to 3 are still not
"cold shutdown" meaning that a significant amount of heat is still being
produced in the core as the chain reaction is not completely stopped.
The time difference between "shutdown" and "cold shutdown" can take
several days, weeks or even months if no sufficient cooling is supplied
(and so does the number of partial discharges of radioactive materials
in the air). Note that the nuclear fission chain reaction is a
self-sustained reaction that would last a long period of time unless it
is stopped by external intervention (cooling). If the cooling fails, the
reaction does not stop by itself and the related problems remain (or
worsen).<br><br>The explosion at unit 3 is technically the same as
Saturday's one at unit 1 (hydrogen explosion). However, its effects will
not be the same as the fuel used in the reactor is different. Indeed,
(unfortunately) unit 3 has been the first reactor from TEPCO to use
reprocessed fuel, the so-called MOX (mixed oxyde) fuel, since August
2010.<br>
sources: <a href="http://search.japantimes.co.jp/cgi-bin/nn20100823a7.html" target="_blank">http://search.japantimes.co.jp/cgi-bin/nn20100823a7.html</a> ;
<a href="http://www.japantoday.com/category/technology/view/mox-fuel-loaded-into-tokyo-electrics-old-fukushima-reactor" target="_blank">http://www.japantoday.com/category/technology/view/mox-fuel-loaded-into-tokyo-electrics-old-fukushima-reactor</a><br>
<br>
MOX fuel is used in nuclear thermal reactors for two main reasons : (1)
it allows using the weapon-grade plutonium in an attempt to reduce the
nuclear weapon arsenals; and (2) it allows reprocessing (not
"recycling"!) the spent nuclear fuel of other reactors to avoid having
to store the waste (which is today one of the main unsolved issue of the
nuclear industry). Reprocessing used fuel corresponds to switch from
the once-through nuclear fuel-cycle (or opened cycle) to the closed
fuel-cycle. However, it is well known that the closed-fuel cycle is not a
preferred solution as it increases the risk of nuclear proliferation
while saving only up to 25% of uranium mining (see the 2010 MIT report
on the nuclear fuel cycle).<br>
source: <a href="http://web.mit.edu/mitei/news/spotlights/nuclear-cycle.html" target="_blank">http://web.mit.edu/mitei/news/spotlights/nuclear-cycle.html</a><br>
<br>
Nevertheless, Japan was apparently planning to have one third of its
reactors using MOX by the end of 2010 in an objective to switch towards a
close-fuel cycle solution (information not sourced). Also, note that
MOX is not reprocessed today, so that we definitely cannot speak of
"recycling" when dealing with the closed-fuel cycle (even if the
industry is using that word).<br><br>
<br><b>Uncertainty on the radioactivity level:</b><br>
<br>
I did not found much information and knowledge about the toxicity of MOX
fuel compared to regular spent nuclear fuel. In general terms, the
shorter the "half-life period" is (the time necessary for the
radioactivity to be reduced by 50%), the more hazardous the product is.
This is due to the fact that short half-life products are more active
than long half-life
products, such as depleted uranium (U-238) with an half-life of 4.5
billion years (practically stable, i.e. not active). In MOX fuel,
Curium-242 may be produced as a by-product of the fission reaction with
potential harm as it has a short half-life of 150 days or so. Another
indicator of the potential toxicity of MOX is that, in France, operating
licenses do not yet allow MOX fuel to remain on site, contrary to
uranium fuel.<br><br>For now, TEPCO is reporting an equivalent radiation
dose rate of 0.02 mSv/h in the surroundings of the plant. This means
that if one stays 1 hour exposed to this radiation level, it receives
about 0.02 mSv to its entire body. For instance, a Paris-New York flight
corresponds to a dose of about 0.06 mSv. So if the dose rate remains
stable during one week, the people around the plant would receive a dose
of 7*24*20μSv/h = 3.36 mSv, so about 56 Paris-New York flights! For
now, there is no reason to say that the radiation level will drop.
Indeed, it would be good news if it would remain stable.<br>
source: <a href="http://www.tepco.co.jp/en/press/corp-com/release/11031402-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031402-e.html</a><br>
<br>Another source of information tells me that 2km from the Fukushima 1
plant, a radiation dose rate of 0.1 mSv/h has been measured by
journalists. Other measures talk about dose rate between <font color="#000000">0.02 and 1 mSv/h!</font>
FYI, in February 2011, the radioactivity dose rate measured by the same
journalist was about 0.04 mSv/h in Chernobyl. Also FYI, the annual dose
of an individual living in France is 2.4mSv (average rate of 0.0002
mSv/h).<br>
So, if this information is true, the situation in Japan is dramatic.<br>
source: Information from <a href="http://www.sortirdunucleaire.org/" target="_blank">http://www.sortirdunucleaire.org/</a> in personal communication (website unaccessible)<br>
<br>
<br>
To conclude, the situation has now become critical as a cascade of
adverse events is currently happening at Fukushima 1 NPP, worsened by
the high uncertainty we face in respect to the radioactivity that is
actually released there.<br><br><br clear="all">François Diaz Maurin<br>Ph.D. Candidate<br>
<span>Research group on Integrated Assessment</span><br>Autonomous University of Barcelona (Spain)<br><br><font size="1">Institut de Ciència i Tecnologia Ambientals (<span>ICTA</span>)<br>
Economía Ecológica Despatx QC 3091 – Escola Tècnica Superior d'Enginyeria (ETSE)<br>
Universitat Autònoma de Barcelona (UAB)<br>08193 Bellaterra (Cerdanyola del Vallès) – Barcelona<br>Tel. (+34) 93 586 81 02<br>Fax. (+34) 93 586 80 08<br><a href="http://www.eco2bcn.es/" target="_blank">http://www.eco2bcn.es/</a></font><br>
</div><br>2)<font size="2"> <span>UPDATE and CONCLUSION: Fukushima Nuclear Power Plant Events</span></font><br><br>Dear all,<br>This is will certainly be my last email covering the
current events at Fukushima nuclear power plants in Japan as the
situation seems now to be stable. Nevertheless, note that the only
"reliable" source of information is coming from TEPCO, the operating
company of Fukushima nuclear power plants, as they are the only one to
have access to the plants, and thus to know what really is going on. All
information depends on what they share with the outside world.<br><br><b>Table of contents:</b><br><b>1. Quick summary of the current situation at Fukushima 2 (or Fukushima Daini) (4 units)<br></b><b>2. Quick summary of the current situation at Fukushima 1 (or Fukushima Daiichi) (6 units)</b><br>
<b>3. Specific summary of the current situation at Fukushima 1 - Unit 1</b><br><b>4. Risks and prospects of the future situation at Fukushima 1 - Unit 1</b><br><b>5. Conclusion and potential effects on the civilian nuclear industry<br>
<br></b><br><b>1. Quick summary of the current situation at Fukushima 2 (or Fukushima Daini) (4 units)</b><br>- According to TEPCO, all 4 units have been shut down and their reactor water levels are stable.<br>-
However, only unit 3 is "cold shutdown" (under full control). The
others still being cooling the reactor core one way or the other.<br>-
All 4 units are releasing partial discharges of air containing
radioactive materials in order to maintain the pressure in the
containment building down (to avoid meltdown of the core due to high
pressure & temperature).<br>- Those releases have been the decision of TEPCO operators.<br>- The evacuation zone is 10 km from the nuclear power plant.<br>-
The situation can be considered under control as TEPCO operators "do
not believe there is leakage of reactor coolant in the containment
vessel" for all 3 remaining units that are still not cold shutdown.<br><br>source: <a href="http://www.tepco.co.jp/en/press/corp-com/release/11031233-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031233-e.html</a><br>
<br><br><b>2. Quick summary of the current situation at Fukushima 1 (or Fukushima Daiichi) (6 units)</b><br>- According to TEPCO, all 6 units have been shut down.<br>-
Units 4, 5 and 6 were on outage (shut down) at the time of the
earthquake and TEPCO operators "do not believe there is leakage of
reactor coolant in the containment vessel".<br>- On unit 2, the water
level is stable (although low). On unit 3, there is still injection of
water inside the containment building to lower the pressure.<br>- Both units 2 and 3 are releasing partial discharges of air containing radioactive
materials (for the same reasons as on Fukushima 2 NPP). Those releases
have been done <u>under the instruction of the national government</u>.<br>- The evacuation zone is 20 km from the nuclear power plant.<br>- The
situation can be considered under control as TEPCO operators "do not
believe there is leakage of reactor coolant in the containment vessel"
for units 3 to 6 although they are not cold shutdown.<br>- No more information for unit 2, but it sounds like an explosion like the one which occurred at unit 1 could happen at unit 2. <br>- For unit 1: see below.<br><br>
sources:
<a href="http://www.tepco.co.jp/en/press/corp-com/release/11031301-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031301-e.html</a> ;
<a href="http://lci.tf1.fr/science/environnement/2011-03/accident-nucleaire-au-japon-un-autre-reacteur-en-difficulte-6308683.html" target="_blank">http://lci.tf1.fr/science/environnement/2011-03/accident-nucleaire-au-japon-un-autre-reacteur-en-difficulte-6308683.html</a><br>
<br><br><b>3. Specific summary of the current situation at Fukushima 1 - Unit 1</b><br>- Unit 1 is shutdown but the core is still hot with a risk of meltdown.<br>-
Sea water and boric acid which absorbs neutron (responsible for the
fission chain reaction) are thus injected into the reactor core to lower
its temperature.<br>- The explosion which happened in the containment building has been damaging <u>only the roof of the building</u> (made of concrete I think)<u>, the steel containment layer remaining intact.</u><br>-
The successive layers of protection from inside to outside are the
following: 1) Reactor core (probably partially meltdown); 2) Reactor
vessel (state unknown but should be OK if core not fully meltdown); 3)
Containment steel layer (intact); and 4) Containment building (broken).<br>-
The explosion is due to a contact between hydrogen from the containment
building and the oxygen from the outside. The hydrogen has been formed
between the steel layer and the building as a result of a lack of water
in the reactor building.<br>- Unfortunately, TEPCO on-site webcam is
really not of help to visually understand the situation as the power
plant is hidden by trees...
<a href="http://www.tepco.co.jp/nu/f1-np/camera/index-j.html" target="_blank">http://www.tepco.co.jp/nu/f1-np/camera/index-j.html</a><br><br>sources: <a href="http://www.tepco.co.jp/en/press/corp-com/release/11031301-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031301-e.html</a> ; <a href="http://www.reuters.com/article/2011/03/12/japan-quake-reactor-idUSTKZ00680620110312" target="_blank">http://www.reuters.com/article/2011/03/12/japan-quake-reactor-idUSTKZ00680620110312</a><br>
<br><br><b>4. Risks and prospects of the future situation at Fukushima 1 - Unit 1</b><br>-
Current situation at Fukushima 1 - Unit 1 is already the second worst
civilian nuclear accident after Chernobyl in the relatively short
history of the nuclear industry.<br>- Consequences of a meltdown at unit
1 would "only" be local (although being dramatic for the immediate
environment) as no explosion of the reactor vessel or of the steel
containment layer is expected (design different from Chernobyl, so this
scenario is to be excluded).<br>- However, in the case of full meltdown,
the core in "fusion" would probably go through the containment building
floor and release radioactivity into the ground. This scenario cannot
be fully excluded for now.<br>
- But chances are that the operators will manage to cold shutdown the reactor.<br><br><br><b>5. Conclusion and potential effects on the civilian nuclear industry</b><br>-
The Nukushima accident would certainly have immediate effects on the
discussion about nuclear energy and its potential role as an alternative
energy source. All this will depend on how the public opinion reacts
after the accident.<br>
- We can be expected that the nuclear industry will soon focus on the
natural disaster cause of the Fukushima accident, saying that new plants
(such as Areva's EPR) are designed to sustain such seismic events. This
is true. However, given the fact that upmarket designs (1300MW and
more) are uneconomical, the trend is to build cheaper new plants (1000MW
and less). But such plants do not necessarily benefit from the same
design features (as being a trade-off between economy and safety).<br>-
As far as having small modular reactors (300MW and less), the
consequences of an accident would be less than in a bigger plant but the
overall risk of accident (= consequence of one accident * likelihood)
would be the same or even higher depending on the number of those SMRs
that are deployed...<br>
- Nuclear fusion for commercial use is not to be considered as a
significant alternative energy source (if it is to be the case) before
the end of the century (according to my study) so that the current
nuclear fission technology is likely to remain the only available
solution we can realistically account for in the discussion about
imminent energy supply issues.<br>
<br>
Sincerely,<br><br clear="all">François Diaz Maurin<br><br>1) <font size="2"><span>UPDATE: IMPORTANT: About the Effect of the Earthquake on Nuclear Power Plant in Japan</span></font><br><br>
The situation at Fukushima-Daiichi
nuclear power plant is becoming serious (but not "critical" in technical terms).<br><br><b>Explosion:</b><br>
It sounds like the explosion that occurred at the plant is an hydrogen
explosion outside the reactor building. So neither the
reactor vessel (second layer of protection), nor the containment building
(third layer) have been damaged due to this explosion.
<br>
<a href="http://www.nytimes.com/2011/03/13/world/asia/13nuclear.html" target="_blank">http://www.nytimes.com/2011/03/13/world/asia/13nuclear.html</a><br><br><b>Radioactive leaks:</b><br>
For units 1, 2 and 4, the TEPCO press release says that "partial
discharge of air containing radioactive materials" have been released.<br>
<a href="http://www.tepco.co.jp/en/press/corp-com/release/11031221-e.html" target="_blank">http://www.tepco.co.jp/en/press/corp-com/release/11031221-e.html</a><br>
<br>The evacuation zone has been extended from region #1 to region #2
(10 km
around the plant) due to the release of radioactive materials in the
air. If no more release is performed, people could come back home as
soon as the concentration of those materials is diluted in the
air.<br>
<br>
This information is confirmed by media (I follow mostly Matthiew Wald from NYTimes and Reuters)<br>
<a href="http://www.nytimes.com/2011/03/12/world/asia/12nuclear.html" target="_blank">http://www.nytimes.com/2011/03/12/world/asia/12nuclear.html</a><br>
<a href="http://in.reuters.com/article/2011/03/12/japan-quake-leakage-idUSTKB00729820110312" target="_blank">http://in.reuters.com/article/2011/03/12/japan-quake-leakage-idUSTKB00729820110312</a><br>
<br>
According to Reuters, the evacuation zone has been now extended to 20 km.<br><br><b>Reactor cores:</b><br>In
the last press release from TEPCO, they indicate that all units have
been correctly shut down. However, having the control rods down (which
stop the chain reaction) does not necessarily mean that the core
temperature is not rising. Among all 4 units, only unit 3 is cold shut
down (= under full control).<br>
As far as the others reactor cores, their high temperature is damaging
the core so we can expect (at least) a partial meltdown if this
situation continues. If a meltdown occurs, it will damage the reactor
vessel and only the containment building will remain between the core
and the environment. A meltdown core can potentially damage the
containment building (due to a specific reaction between the core and
the concrete) with severe consequences on the environment.<br>
<br>This is the most important risk of Fukushima nuclear power plant.
And the probabilities are multiplied by a factor of 3, as 3 units out of
4 are concerned.<br><br>Regards,<br clear="all"><br><u>0) Primer mail enviat:</u><br><br>Dear colleagues and friends,<br><br>As a former
engineer in the US and French nuclear industry, I can tell you that
what is currently happening at the Fukushima-Daiichi
nuclear power plant is really important.<br><br>The safety reactor
coolant
systems are mal-functioning (normally activated by safeguard diesels
that are now out of order), so that the reactor core cannot be cooled
normally.
As a result, the temperature of the core is rising (with an increased
risk of melting) and so does the pressure inside the containment
building. If this pressure is becoming too high, there is a risk of
explosion of the containment. Although the design of the plant is not
the same as the one in Chernobyl, there are still "chances" that such a
worst case scenario happen at Fukushima plant if the pressure inside the
containment is not lowered. The only way to keep the pressure down to a
certain level is to
release some gases into the atmosphere, but those gases are most
probably with a high level of radioactivity.<br> <br>Last news here: <a href="http://live.reuters.com/Event/Japan_earthquake2" target="_blank">http://live.reuters.com/Event/Japan_earthquake2</a><br><blockquote style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;" class="gmail_quote">
<i>
Power company TEPCO says it has lost the ability to control reactor
pressure at Fukushima No. 1 and No.2 reactors. A spokesman said
pressure is stable inside the reactors but is rising in the containment
vessels. He said it is not known if there will be a need to release
pressure at the plant at this point. That would involve a release of
radiation.</i><br></blockquote><br>At the present time, only the engineers on-site know exactly what is
going on (and what to do). Unless the operators can one way or the
other have the safety reactor coolant system working again, they most
probably chose the option of successive gas releases until they can cool
the core and shut down the reactor.<br> <br>It sounds like the US Air Force is shipping in emergency some generators to help restart the coolant systems (pumps).<br><br>Be
sure that all countries will do everything possible to prevent a worst
case scenario from happening. A severe accident at the Fukushima-Daiichi
nuclear plant, and it will be the cause of a new human and environmental disaster which will
certainly marks the end of the nuclear industry.<br><br>All this depends on the current decisions made by the crew of the Fukushima power plant.<br><br>Hopefully they stay clever.<br>Sincerely,<br><br clear="all">François Diaz Maurin<br>
-- <br>"En la plenitud de este acto de amar, en su existenciación, en su praxis, se constituye la solidaridad verdadera." Paulo Freire<br><br>Pere Ariza-Montobbio<br>
931825776<br>
ICTA-UAB 93 586 81 02 //93 581 29 74. <a href="mailto:pere.ariza@uab.cat" target="_blank">pere.ariza@uab.cat</a><br>