Japan to vent 'slightly' radioactive 'vapor' from troubled nuclear power plant

[George Dowell]

Their words not mine.
http://content.usatoday.com/communities ... -reactor/1

George Dowell

[Wilfried Heil]

The German radioactivity monitoring network is the so-called "ODL-Netz":
http://odlinfo.bfs.de/

This opens a map with about 1800 stations. The stations are clickable too
and show the measurements of the last 7 days.

Looks like the network in northern Japan is at present either damaged or disabled.

[Richard Hull]

Shades of the venting at TMI, also a coolant accident that was human error created due to stuck instruments, a U tube in the cooling system and humans overiding the computer control.

Here we are probably dealing with real earthquake damage to the core cooling system or its scram mechanism. We just might hear the truth in a year or two.

Let's hope for a good net outcome.

Richard Hull

[George Dowell]

Thanks for explaining.

George Dowell

[David Geer]

Luckily the control rod system wasn't damaged in the quake and the affected plants are shut down. A runaway critical reactor would have been a lot worse than what is going on right now.

My father does work during brown outs/down time on US power plants and the cooling system is always a bear to work with due to the temps on some of the outbound piping and limited exposure time on maint. workers in those areas. Checking every connection and joint for structural damage and performing on-the-spot repairs while swapping out workers every few hours, these folks are working like hell to keep the plants safe.

Well, that's just my two cents and hopefully we won't see anything too drastic in the damages and aftermath from this event. Just wish I was back home in California for the surfing though.

David Geer

[Frank Sanns]

David Geer wrote:
> Luckily the control rod system wasn't damaged in the quake and the affected plants are shut down. A runaway critical reactor would have been a lot worse than what is going on right now.

Agreed, but even with a scramed reactor, cooling water is necessary. The decay products are the culprits as their energy has to go somewhere and that is into heat and will continue to do so. It is not a question of if one of these reactors will release radiation, but how much will they release. Big problems there and TMI here we come again. Cooling water is probably too late now to stop the core damage that is underway.

Frank Sanns

[jcs78227]

Frank S. wrote:
> Agreed, but even with a scramed reactor, cooling water is necessary. The decay products are the culprits as their energy has to go somewhere and that is into heat and will continue to do so. It is not a question of if one of these reactors will release radiation, but how much will they release. Big problems there and TMI here we come again. Cooling water is probably too late now to stop the core damage that is underway.

Frank- that was my thought exactly. TMI initially thought the situation was never going to be as serious as a partial meltdown because the reactor had undergone a successful SCRAM. As you pointed out, a SCRAM simply stops the fissioning by bringing the reactor to a subcritical configuration, but the short-lived fission products and other chemical species (radioactive or not) are still HOT and their decay will release more thermal energy (not to mention the large amount of fuel that will take days to cool), enough for the water to react with the cladding and decompose. From some reports, this was a LOCA(confirmed?), and there may have been damage to the cooling infrastructure severe enough to impede both the LPCI, HPCI and the ECIS. Even TMI had it better than that. They didn't mention, at least from what I've seen, any use of neutron poison quenches/injections or doping of the coolant, though I suppose it would be unnecessary if the core was successfully SCRAMed.

It's still early, but one has to wonder how far above the core the water level is, and what the recirc. rate they are able to achieve is. The high pressure readings, enough to warrant a venting to the atmosphere of radioactive gases could lead one to believe that the core *might* have been uncovered or that the recirc. rate is not what they need. Either way, there is a pressure buildup and in a PWR that isn't a concern unless you don't know from where the "P" is originating. Bottom line- they are venting gases and that is both a good thing to know, but a bit ambiguous as to the many potential sources of this excess pressure.

Just a note: I am reading several different technical reports on the unfolding events, and some appear to be confusing which reactors are having problems, and which reactor site is actually experiencing a general emergency. In addition, TMI was a BWR and the reactor I am speaking of is a PWR, so the comparison is meant to be roughly analogous.

The local Japanese news coverage seems a lot like that of the TMI coverage, probably more out of necessity than deliberate bad journalism. These events take time to unfold and the public wants answers to questions the professionals may not yet have answers to.

My prayers are with the engineers as they work to stabilize and safe all of the reactors in Japan.

-Jonathan

[Chris Bradley]

Explosion heard at plant. reported 5 mins ago.

http://uk.news.yahoo.com/5/20110312/twl ... d0ae9.html

..Looks like it is turning out problematically....

Good luck, guys.

Is just a simple flooding of the reactor to achieve evaporative cooling the least worst option, in such a disaster?

[Carl Willis]

Ordinarily this would be an off-topic digression, but as information trickles out about the Fukushima-1 accident, it's becoming evident to me at least that it is a very unfortunate accident, the severity of which has probably gone unparalleled in decades. It will be a redefining event for the nuclear energy industry, and a touchstone in technical discussions both among senior engineers / scientists and laypersons / amateur nukeheads. Hopefully it will not be associated with any deaths.

The afflicted reactor is a General Electric boiling water reactor, similar to numerous plants in the US, having a second-generation ("BWR/3") layout and "Mark 1" containment. The containment structure is a drywell that is linked to a doughnut-shaped steam suppression pool filled with water. An example is shown in p. 3-16 of this NRC document:

http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

According to reports from the BBC right now:

>Japan's nuclear agency said on Saturday that radioactive caesium and iodine had been detected near the number one reactor of the Fukushima 1 plant.
(http://www.bbc.co.uk/news/world-asia-pacific-12720219)

If accurate, that points to only one conclusion--fuel cladding damage (and possibly further damage like a meltdown). These radioelements are fission products and as such are expected to remain contained within the fuel unless the fuel is damaged. So the news reports are consistent right now with fuel damage. That is a terrible, terrible consequence in this business, and quite likely the end of this reactor's career.

I don't think it's clear to anyone right now (outside of the TEPCO utility and Japanese government, anyway) what the accident sequence was or continues to be. It sounds like a loss-of-heatsink accident caused by extended station blackout. I won't speculate further, I am not in this business professionally, but I will put up a few photos from my grad student days relating to some of the relevant safety systems in a GE BWR, just for stimulative and educational purposes. Photo credits go to Brian Hajek, Ohio State University, and to Perry Nuclear Power Plant (a BWR/6, Mark 3 containment, so more modern than Fukushima-1, but still similar in many respects).

1. The low-pressure core spray (LPCS) pump. This is a large electric pump, capable of being powered by the Division I or 2 Diesel generators or offsite power, takes suction on a source of water such as the suppression pool and injects it into the reactor. This system will only be used in the event of a severe depressurization, such as a loss-of-coolant accident.

2-3. Emergency Diesel generators and cooling system benchboard in the control room. From these photos, much of the logic and layout of the cooling systems is evident. Even in a station blackout, the RCIC pump can be operated because it uses the reactor's own steam supply to drive the pump (via a small turbine about the size of a doghouse). Divs. 1-2 Diesels are redundant. The Division 3 Diesel powers its own load, the HPCS (high-pressure core spray) pump. Water can come from either the suppression pool or the condensate storage tank (CST).

4. Residual heat removal (RHR) systems are responsible for removing decay heat from the core during shutdown and rejecting it to the service water (lake, ocean, etc. water).

5. Service water pumps. Electrically powered, of course.

6. An emergency Diesel generator at Perry NPP.

7. In the event of an accident, the operators consult these prepared flowcharts to guide their response.

-Carl

[Frank Sanns]

Thanks for the nice summary Carl. When I wrote another TMI, I resisted writing "or worse" after it even to it seemed eminent. Well it happened.

In the video that you posted, the explosion had a shock wave associated with it so this is not just a simple venting or a low velocity explosion. It was a catastrophic failure of something big with a pressure on the order of a couple hundred MPa or 30,000+ psi. This can only come from a rupture of the containment building itself or from an adjacent structure that cooling systems are attached. It seems that they would have been venting pressures before reaching the limits so some kind of bumping of the cooling water might have done it but much more likely was a hydrogen oxygen explosion that destroyed the containment building.

Get out your detectors as depending on the wind patterns, many of us will be detecting these products coming to an area near you in the next few days.

Frank Sanns

[hjerald1]

Not sure what radioactivity you work with James, but of course, KI is only protective in the event of radioiodine exposure.

Since Iodine-131 is a major fission product, KI administration is useful as a radioprotectant for the thyroid gland for exposure to this element in the event of fission reactor radiation releases.

Anyway a serious situation in Japan. One can only hope that the many safety systems present in these reactors function properly!

Jerry

[George Dowell]

Thanks for explaining.

George Dowell

[David Geer]

Not really off-topic as folks could take a trip out there, if allowed and perform scientific detection studies/readings. Albeit a disaster, this would make a great learning experience for the nuclear physics portion of a fusioneer's knowledge base.

[jcs78227]

Carl,

Thanks for expanding on the problem and providing photos to boot.

I took a press release and understood that the reactor in question, at least the worst reactor, was a PWR; apparently they were mistaken and I perpetuated that mistake.

You mentioned what I had alluded to, damage to the core (fuel assembly's cladding), though at the time only the iodine had been verified. Obviously this can happen very quickly with a LOCA if the the coolant level falls too low and the fuel is uncovered, but with your knowledge of reactors is there any other modality by which the fuel assemblys could suffer similar damage? I'm talking physical changes that are not secondary to some chemical reaction like corrosion due to neglected reactor chemistry or unchecked cavitation reactions between the cladding and water. The cladding reaction with water is well known and an area I am familiar with as a metallurgist, but when it comes to reactors I just wondered if the kind of damage you speak of can be brought about by some more insidious or latent process.

This is certainly a tragedy the scale of which can not yet begin to be assesed.

-Jonathan

[Carl Willis]

Hi Jonathan,

The media reports have suggested a loss-of-heatsink (LOHS) accident after shutdown, caused by station blackout.

In a protected LOHS, the heat source is reactor decay heat. This typically has an initial value of about 7.5%, but depends on the core's history. This heat source P(t) decays over time approximately according to the following equation, where t is the time after shutdown (in seconds), and t0 is the duration of steady-state operation prior to shutdown at thermal power P(0):

P(t)/P(0) = 6.6E-2 * [t^-0.2 - (t + t0)^-0.2] (Source: R. A. Knief, Nuclear Engineering: Theory and Technology of Commercial Nuclear Power, Taylor and Francis, 1992)

In this kind of accident, heat cannot be removed from the core because the thermal pathway to the ultimate heatsink, e.g. ocean water, is interrupted. The first part of the accident is heat-up of the core and coolant inventory, leading to overpressurization. Fuel can dry out in the later course of the accident when the decay heat flux exceeds the critical heat flux, resulting in "film boiling" and probable dryout at the top of the core. Dryout leads to excess temperatures in the fuel, followed by cladding damage, followed by displacement of hydrogen from steam by the cladding and other metals, followed by partial meltdown.

All the media reports I have read are consistent with this general interpretation. I don't think much more can be said with the state of knowledge as incomplete as it is...like just about everyone else, I watch the news and try to comprehend this situation from a position of very limited specifics.

-Carl

[Frank Sanns]

The course of events have been set into place since the night of the quake. All efforts to contain have been suspended at time of this post. It appears that water levels are falling below the reactor and the stored spent fuel rods and a fire is spreading to more and more of the fuel and at least one is completely open to the air at this point. This has the potential to be on scale with Chernobyl or worse because of the multiplicity of core materials involved. It is possible with unfavorable winds that Tokyo itself may even have to be evacuated. The next 24 hours will be extremely critical for an estimation of the enormity of this calamity. This has clearly been shaping up to have a less than good outcome.

Frank Sanns

[Andrew Seltzman]

Some reports indicate that the increased radiation was caused by a crack in the suppression chamber, allowing steam from the core to vent directly into the atmosphere.

http://www.bbc.co.uk/news/science-environment-12745186

Andrew Seltzman

[Frank Sanns]

Andrew,

The information is SO sketchy. It is hard to know any of the truth but when the last man is running away he must know something. The pool with the multiple spent reactor cores that is open to the air is a ticking bomb as much as any one of the reactors. Boiling off all of the water while spattering the fuel into the air would not be a good scenario. Let's hope your report is correct lest this catastrophe grow.

Frank Sanns

[Carl Willis]

I received a document from a friend in Tokyo that tabulates doserates in major cities in Japan over the past few days, and time-dependent data for Tokai, Ibaraki Prefecture (where doserates swung to some 100-200 times background on March 15). One of the higher readings, 1.318 μGy / hr (0.1318 mrad / hr, about 20-40 times local background), was measured in Utsonomiya, Tochigi Prefecture on March 15.

Upload is here:
http://carlwillis.files.wordpress.com/2 ... er02_1.pdf

-Carl

[Richard Hull]

I have a small GM counter biz here and a local rock shop and I have worked on and off, whereby, they have some rock hound stop by and ask about a counter and I respond. This results in a pitiful 2 or 3 counters per year sales.

I am headed over with 3 counters this weekend for the shop who told me they are pre-committed for 3 different, unhinged, nervous nellies and not rock hounds. So, I took the honing stone to my fleecing sheers last night. Ignorance and mindless fear pays top dollar, always.

Richard Hull

[lutzhoffman]

On a related note: Here in Hawaii Potassium Iodide tablets are flying off the shelves, with huge profits being made off the stupidity of many people here, in spite of the fact that there has been "zero" increase from background per the state air monitoring system: Which is actually a pretty neat setup with several massive scintillation detectors.

The humor came later in several news broadcasts, where several reporters said that:

"Pottasium Iodide tablets are being bought by folks to protect themselves from radioactive "Potassium".

Hey that's a new one??? I had no idea that U fissions into 4+ fragments forming a new magical form of radioactive Potassium, which is a gas! Maybe we need to worry about "Red mercury" as well : )

[JohnCuthbert]

I wonder how much of a panic you could cause by showing that "The government stockpile of potassium iodide tablets are all radioactive!"?

A decent Geiger should show the radiation from the 40K in a big polythene bag of them with no problem.

Now that's what I call a conspiracy theory.