Japan Earthquake: nuclear plants

jensjakob

Official report:
"There is immediate threat of
radioactive nuclides release from the spent fuel pools of Unit 3 and
4, because of incapability of cooling these pools."
http://www.jaif.or.jp/english/news_i...300590001P.pdf

AtomicWombat

Angry Citizen, do you have any evidence to support your assertions? At Chernobyl, photographs were taken of corium at close range.




Note the steel steam pipe has not melted in the last image.

The radiation measurements we have seen so far are not inconsistent with exposed corium:
http://www.physicsforums.com/showpos...&postcount=491
http://www.physicsforums.com/showpos...&postcount=495
http://www.physicsforums.com/showpos...&postcount=526

Workers were exposed to corium at Chernobyl for brief periods - most survived. I have heard some reports of emergency workers at the Fukushima falling ill with symptoms suggestive of radiation poisoning, but the condition is insidious, with death after lethal levels of exposure taking up to three months:
http://www.nytimes.com/2011/03/16/wo...pagewanted=all
"Among plant employees and firefighters at Chernobyl, many volunteered to try to tame, and then entomb, the burning reactor — although it is not clear that all were told the truth about the risks. Within three months, 28 of them died from radiation exposure. At least 19 of them were killed by infections that resulted from having large areas of their skin burned off by radiation, according to a recent report by a United Nations scientific committee. And 106 others developed radiation sickness, with nausea, vomiting, diarrhea and dropping blood counts that left them highly vulnerable to infections. "

I don't have confidence that we would be told the full details about cases of radiation sickness in this incident. Do you?

AtomicWombat

Hi TCups,
I've examined the reactor building frames and made some measurements on Google Earth. Reactors 2, 3 and 4 have roof dimensions about 35 by 45 metres (120 by 150 feet). I believe they are about 55-60 metres tall although this is harder to estimate. The short dimension (35 m) is spanned by 4 spans - held up by 5 rows of vertical beams. The longer dimension (45m) is spanned by 6 spans - held up by 7 rows of vertical beams.

This is consistent with this diagram:


The mouth of the primary containment - the concrete flask that holds the reactor is about 10-12 metres across. I believe I am in agreement with you in that the evidence suggests that the "concrete shield plug" has been blasted out of the building by an explosion originating deep in the containment. In my view stated earlier:

"The explosion last Monday was directed strongly vertically suggesting to me it originated from deep within the containment structure. It clearly carried substantial solid material to a height of 400-500 metres. Whilst I can't be sure this may have been due to a melt-down of the fuel rods in reactor 3. They melted through the reactor floor (1500 Celsius) and fell into the flooded "dry-well" below. This triggered a large steam- zirconium-water-hydrogen explosion. I suspected this not only blew the concrete top off the containment, it also blew most of the reactor contents out of the reactor."

This explosion was clearly different in nature from the explosion of building 1 which was directed horizontally, with the debris cloud not exceed the height of the stack (120-150 metres). The explosion of building 3 can be likened to the popping of a champaign cork - the shape of the flask directs the energy vertically.

I suspect the hole you have identified is too large to be just the reactor mouth. My impression from the available drawings and the video is the RHS of the hole is the open reactor mouth and the LHS is some form of deep storage pool, perhaps for spent fuel (SFP), equipment etc.

As to the fuel rods and yellow material, they are suggestive, but I'm unsure. Where are the other components of the fuel assemblies - the spacers and channels (external box)?



And I keep seeing image artefacts suggestive of hot spots, even on satellite images.. I'm still looking for corroborative evidence (or otherwise).


Note, this is a useful page.

TCups

Jens:

I agree with your analysis. One of the two trucks seems to still have its casket. The second truck is partially covered with debris -- I can't tell if it is an empty cradle where the casket used to be or if the casket is just covered with debris and harder to see. Also, it appears that the smoke/steam is coming from a point source and spreading out, perhaps as if leaking from a pipe or crack, not rising from the entire surface of the area of the pool. I believe that point might be near the gate connecting the SFP with the containment wall outside the reactor vessel -- do you agree?



Also, it seems to me that the fly-over footage spent a lot of time looking at the debris field on the ground. Leads me to wonder if they were looking for something in particular. Don't know.

AtomicWombat

I agree with jensjakob, the square hole appears to be a lift well for fuel elements.

AntonL

I think you are referring to the white dots with red or green around them - overexposure from reflected sunlight from a metal sheet. You can see lots of them in the harbor when sun reflects of the water.

AtomicWombat

Interesting article on the UCS site on the operations & dimensions of the spent fuel pool.

Possible Source of Leaks at Spent Fuel Pools at Fukushima

minerva

The same fission products as any other reactor, really. The fact that it's MOX fuel is not really significantly different; the fission products are pretty much the same as any other reactor and the plutonium itself is not significant.

swimmer

Update: No gases to be released from No. 3 reactor
http://www3.nhk.or.jp/daily/english/20_23.html

minerva

Personally, I don't take UCS very seriously. I always remember the fact that, despite working with them closely on disarmament and arms control issues, Hans Bethe refused to join UCS because they were fundamentally opposed to all nuclear power, a position that Bethe refused to endorse.

Of the thousands of nuclear physicists and nuclear engineers across the United States, they found themselves with a couple who became anti-nuclear activists - like Lochbaum.

Lochbaum's claims about a Zircaloy fuel cladding fire have been debunked... simply by actually doing a simple experiment.

AntonL

What caused the welds on these pipes to break and unfurl?

Reno Deano

MOX fuel is different, I beg to differ. Higher gap fission product migration/releases, etc. Burns different. If melted will release 100 times mores plutonium than standard LEU fuel rods. See NRC Safety Analysis for putting MOX in US reactor:

http://adamswebsearch2.nrc.gov/idmws...4&id=040970215

Excerpt: Table 1: Nominal Unirradiated Fuel Isotopics, %
U.S. European Proposed
Isotope LEU MOX MOX LTA
wt% 234U / U 0.03 ---- ----
wt% 235U / U 3.2 0.24 - 0.72 0.35
wt% 236U / U 0.02 ---- ----
wt% 238U / U 96.75 92.77 95.28
wt% 238Pu / Pu ---- 0.88 - 2.40 0.05
wt% 239Pu / Pu ---- 53.8 - 68.2 90.0 - 95.0
wt% 240Pu / Pu ---- 22.3 - 27.3 5.0 - 9.0
wt% 241Pu / Pu ---- 5.38 - 9.66 1.0
wt% 242Pu / u ---- 2.85 - 7.59 0.1
wt% Pu / HM ---- 4.0 - 9.0 4.37
wt%Fissile / HM 3.2 3.65 - 5.25 #4.15
HM = Pu + U. May not sum to 100% due to rounding and ranges. Derived
from data in licensee submittal, ORNL/TM-2003/2 [Ref.1], NUREG/CR-0200 V1 [Ref.2]
The two MOX fuel types differ in that the relative concentrations of plutonium and uranium and
the distributions of their isotopes differ. Table 1 above compares the distribution of fissile and
non-fissile isotopes in typical LEU fuel, typical commercial reactor-grade MOX fuel, and the
proposed MOX LTAs. The differences in the initial fuel isotopics are potentially significant to
accident radiological consequence analyses since the distribution of fission products created
depends on the particular fissile material. If the fissile material is different, it follows that the
distribution of fission products may be different. For example, one atom of I-131 is created in
2.86 percent of all U-235 fissions, whereas one atom of I-131 is created in 3.86 percent of all
Pu-239 fissions. This is an illustrative example only in that the radionuclide inventory in the fuel
at the end of core life depends on more than fission yield. Nonetheless, this shift in the fission
product distribution needs to be evaluated for its impact on the previously calculated
radiological consequences of DBAs.
The LEU fuel is enriched in the U-235 isotope, an operation that occurs on a molecular scale
while the UO2 fuel is in the gaseous phase. This processing results in fuel pellets with a high
degree of homogeneity and uniform grain sizes. The proposed MOX LTA fuel will be
manufactured in a process that involves blending of UO2 and PuO2 powders to achieve the
desired Pu content. The MOX fuel pellets, therefore, are not as homogeneous as an LEU fuel
pellet. This difference in pellet structure has the potential to affect the diffusion of fission gases
through the fuel pellet and may impact the fraction of the pellet fission product inventory that is
in the fuel rod gap between the pellet outer surface and fuel clad inner surface (i.e., gap
fraction). It is generally understood that the fission gas release (FGR) rate for MOX fuel is
greater than that for LEU fuel, given comparable enrichments and burnups. This behavior is
primarily explained by the lower thermal conductivity of MOX fuel pellets that results in higher
fuel temperatures than in LEU rods. Since the gap fractions are an input to the analyses of
calculated doses from non-core melt DBAs, changes to the gap fractions associated with MOX
fuel need to be considered

AntonL

I would be more interested to know how it came to a hydrogen explosion in reactor 4.
That all the water boiled away to expose the fuel just does not seem possible to me,
as then by now all the fuel rods would have been exposed and a huge fire would be witnessed
TEPCO always stressed that there is enough water in SFP so hydrogen generation could not have
been from the SFP. So from where was H2 generated?

We recap the source of the hydrogen is: The claddings of the fuel rods which keep the fuel together
are made from alloys of zirconium. When the rods are no longer covered by water during an accident they
reach temperatures much higher than they designed for, and the metal starts to oxidize at about 1000 °C.
Since there is no free oxygen around the reactor core the metal reacts with the water vapour and takes
the oxygen from there. When oxygen is removed from the water molecule hydrogen is left.

Now I must be careful in italics below is just my imagination and speculation and not reality:
Various cross sections Of the reactors show a smaller pool or equipment pool. Lets suppose some of the
equipment pools water was "borrowed" to make up lost water in the neighbouring reactors, this would save
the reactors (once sea water injection started the reactors are scrapped), Also remember Hilary Clinton
at the beginning of the catastrophe announced that USA is urgently sending special coolant to the site,
thus "borrowing" water from the equipment pool does not seem to be a bad and dangerous decision;
unless supposedly some fuel was stored in the equipment pool of unit 4 as the SFP is completely full
because of maintenance. This could explain the hydrogen development and the two short lived fires
that self extinguished in reactor 4, and lay weight to the speculation in this thread regarding the molten mass.

Time Line:
Unit 1: 11th 16:36 Event falling under Article 15* occurred (Incapability of water injection by core cooling function)
Unit 2: 11th 16:36 Event falling under Article 15* occurred (Incapability of water injection by core cooling function)
Unit 3: 13th 05:10 Event falling under Article15* occurred (Loss of reactor cooling functions) (Two days later)
Unit 4: 15th 09:38 Fire occurred on extinguished spontaneously
Unit 4: 16th 05:45 Fire occurred on extinguished spontaneously

Reno Deano

NEI has release a White Paper on BWR Mk-1 Containment Status and History.

http://www.nei.org/resourcesandstats...i-containment/

Interesting information on Mark 1 containment analyses and required upgrades.

Reno Deano

IAEA officials will hold a briefing today Sunday for journalists to discuss the nuclear emergency in Japan.

The briefing will begin at 16:30 CET on Sunday, 20 March 2011, in the Press Room of the M-Building, in the Vienna International Centre (VIC).

http://www.iaea.org/press/

NRC to hold public meeting on Japanese Reactor crises March 2st, 2011

http://www.nrc.gov/public-involve/pu...cast-live.html

rogerl

Just wondering.. how come nuclear plants don't install cameras inside the reactor core itself so they can see it live? Even a $10 video camera module at Radio Shack would be effective. Cost cutting in Japan?

Astronuc

Camera's are used at some distance. Normal camers would get fried by the radiation. Cameras are not suited for 285C (555 F) operating temperatures or pressures ~72 atm (~1055 psia). Even rad-resistant cameras can only take so much before the glass turns brown due to radiation.

GE's comments on the Fukushima matter
http://www.gereports.com/facts-on-th...tion-in-japan/
http://www.gereports.com/setting-the...nment-history/

http://files.gereports.com/wp-conten...dvanBWR_LR.pdf