Scientists warn of risks from spent-fuel cooling pools and plutonium-rich, mixed-oxide fuel inside o

[Shallah Kali]

Scientists warn of risks from spent-fuel cooling pools and plutonium-rich, mixed-oxide fuel inside one nuclear reactor, even as the No. 1 and No. 3 reactors appear to be coming under control.
http://www.csmonitor.com/USA/2011/0314/Japanese-nuclear-reactor-update-Amid-signs-of-progress-new-problems

We are currently coordinating with the relevant authorities and departments as to how to secure the cooling water to cool down the water in the spent nuclear fuel pool," the release said. Just how serious the cooling problem is remains publicly unknown, but raises concerns for some US nuclear experts.

A particular feature of the 40-year old General Electric Mark 1 Boiling Water Reactor model – such as the six reactors at the Fukushima site – is that each reactor has a separate spent-fuel pool. These sit near the top of each reactor and adjacent to it, so that cranes can remove spent fuel from the reactor and deposit it in a swimming-pool-like concrete structure near the top of the reactor vessel, inside each reactor building.

If the hydrogen explosions damaged those pools – or systems needed to keep them cool – they could become a big problem. Keeping spent-fuel pools cool is critical and could potentially be an even more severe problem than a reactor meltdown, some experts say. If water drains out, the spent fuel could produce a fire that would release vast amounts of radioactivity, nuclear experts and anti-nuclear activists warn.

"There should be much more attention paid to the spent-fuel pools," says Arjun Makhijani, a nuclear engineer and president of the anti-nuclear power Institute for Energy and Environmental Research. "If there's a complete loss of containment , it can catch fire. There's a huge amount of radioactivity inside – far more than is inside the reactors. The damaged reactors are less likely to spread the same vast amounts of radiation that Chernobyl did, but a spent-fuel pool fire could very well produce damage similar to or even greater than Chernobyl."

[Statistical]

1. The reason why less attention is paid to it is because it is a simpler problem.

If there is water in the cooling pond then you are good.
If there is no water in cooling pond then add water.

I doubt onsite nobody is monitoring the cooling pond but the pond holds a lot of water and heat output of spent fuel is much much lower than fuel inside the reactor thus the situation is much simpler and much slower.

Without active cooling the fuel in the pond will slowly evaporate the water. It will take multiple hours for that to happen and at any time you can add more water and "reset the clock".

The reactor is a far more complex problem. You are dealing with a damaged system under pressure, with far more heat output that needs constant water flow. It is also complicated earlier pumping stopped because vents failed (in closed position) since steam couldn't get out they couldn't pump water in. That kind of situation could also damage the pumps or pipes. So it requires near constant attention.

The cooling pond on the other hand is more like a swimming pool.
Is water low? - then add water.
Is water not low? - then check again in 15 minutes.


So as one can imagine regulators, and plant operators are going to spend more time talking about the immediate threat. Without any cooling at all (no pumps, no water in core) the fuel would melt the core in about an hour. Much more pressing problem.

[whosinpower]

3. If the pool itself is damaged from the explosion

there is a possibility that the "pools" will no longer hold water.....what if the pools themselves are cracked, split, broken, etc etc after the explosion?

[Statistical]

4. Then you would have a massive massive radiation release right now.

Something that would make every detector within 200 miles shoot off the chart.
Given that hasn't happened yet it isn't something to retroactively worry about what could have happened.
To avoid it happening in the future the best thing is to get the reactor core cooled and under control so once again the focus is on the core.

Even if the pond is cracked as long as water can be added faster than it leaks "solving" the problem temporarily easily.

Back to:
Is water low? - If so add water
If not check in 15 minutes.

It isn't a "complicated" problem. This doesn't mean it isn't potentially serious just that there isn't a lot of complexicity invovled. Either the pond has water or it doesn't.

If the pond has water - good
If the pond water is low but you can add water - then add water.
If the pond is out of water and you can't add water - you are out of solutions.

[kristopher]

12. Really?

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=439x643966

[Shallah Kali]

5. satellite pictures of the Fukushima plant showed evidence of damage to the spent fuel pool.

Japan's nuclear crisis: regulators warned of reactor risks

In 1972, the first warning was issued about the vulnerability of the sort of General Electric reactors used in Fukushima in Japan

http://www.guardian.co.uk/environment/2011/mar/14/nuclearpower-energy

Robert Alvarez, a senior policy expert at the institute of Policy Studies, said satellite pictures of the Fukushima plant showed evidence of damage to the spent fuel pool. "There is clear evidence that the fuel cask cranes that haul spent fuels to and from the reactor to the pool both fell. They are gone," he said. "There appears to be copious amounts of steam pouring of the area where the pools is located."

He said there was no evidence of fire but described the situation as "worrisome".

"What we don't know is whether or not explosions or the quake or the tsuanmi or a combination of things might have damaged support structures or compromised the pool," Alvarez said.

He warned that it could take years to repair the damage to the upper decks of the reactor and to move the discharged fuel into a safer area of storage.

[Statistical]

7. I said it is simple not that it isn't potentially dangerous.

There are no moving parts to the cooling pond, no pressure issues to deal with, no danger of criticality, no risk of damaging containment.

Is there water in the pond?
No, then add water.
Yes, then check again in 15 minutes.

As long as there is water in the pond and an ability to replace water lost (either through cracks, or everporation) then the issue is stable.

Think of it as a patient.

Cooling pond - stable but critical.
Reactor #2 - critical and unstable.

[flamingdem]

8. Problem: Water hits rods and turns to steam (fail)

The seawater idea is not tested, it's improvisation

[Statistical]

10. Why is it fail?

1) the goal would be to add water to the pond before it is out of water.
In essence if the pond is outputting say 1 million BTU it will evaporate 4,000 gallons per hour. If you add 4,000 gallons per hour the water level in the pond will remain constant.

2) Even if water flashes to steam it will cool the rods. The action of turning water to steam requires energy and thus pulls energy from the rods lower the temperature.

3) While using seawater isn't optimal the same issue relates also to the core. The core is far more pressing than the spent fuel. It has much higher thermal output, it is far more complicated, and you need to ensure you maintain pressure (to raise boiling point of water) without having pressure get too high (so it either bursts the RPV or prevents water from entering).

[flamingdem]

11. Let's hope it is not fail, but it is improvised and untested as a method nt

[Peace Patriot]

13. I just read that they're piping ALL sea water to THREE plants through ONE pipe

and pumping system (don't know how big a pipe) and have had problems with malfunctioning gauges, valves and vents. Their efforts to pour sea water into the spent fuel pools could be hampered by these conditions.

Also, the damage of today's explosion (at Fukushima 3, I believe, the one with plutonium) seems much more severe than Saturday's explosion (in F-1). The top of the outer containment housing looks melted and very damaged down about a third to half of the structure. The diagram I saw of these nuke plants places the spent fuel pools at the top of the facility near the roof. Have you seen the pix of F-3? How could the spent fuel pool have survived that explosion? You say we would know from radiation levels. I think it's quite likely that Japanese authorities are lying about radiation levels to prevent panic. Also, there were reports that one of these plants was leaking water (and I think it was F-3). What would impacts be if that pool in fact got blown out in the explosion? What consequences for the core (which is likely in partial meltdown already)?

I'm not clear on any plant designation except F-1. So maybe I meant F-2. (Explosion today, plutonium in the fuel.) I understand that there are three plants in critical condition (partial meltdowns) and seven total with cooling problems. I also understand that a "worst case scenario" (big release of nuclear material into the atmosphere) depends a lot on fire. What is your prognosis on "worst case scenario" if even one spent fuel pool catches fire in these close quarters (nuke plants packed together in one place), with one or more plants suffering complete meltdown? Will the underground barriers (under the core) disperse the core material so that it doesn't get incinerated and sent into the atmosphere?

One other question: If a spent fuel pool is cracked and failing, and the spent fuel gets spread around, can fire be suppressed by turning the sea water hose onto it? (--presuming they can direct the flow) --or by flooding the entire remaining chamber--if it can hold water--with sea water?)

[snagglepuss]

2. "spent-fuel pool fire could very well produce damage similar to or even greater than Chernobyl'

It's troubling that authorities aren't giving more information about the status of these pools. If there is no problem why not set minds at rest?

[FLPanhandle]

6. People forget about the Kyshtym disaster

http://en.wikipedia.org/wiki/Kyshtym_disaster

Still the second biggest nuclear accident ever.

All about spent fuel not being properly cooled.

[Uncle Joe]

9. My heart goes out to the people of Japan.

I hope they can get this under control and that we're aggressively helping them in any way that we can.

Thanks for the thread, Shallah Kali.

[Shallah Kali]

14. Propublica: Status of Spent Nuclear Fuel in Question at Crippled Japanese Power Plant

http://www.propublica.org/article/status-of-spent-nuclear-fuel-in-question-at-crippled-japanese-power-plant

Concerns about a radiation release from the Fukushima Daiichi <1> power facility have focused on its stricken nuclear reactors, but the plants of that design also store highly radioactive spent fuel in pools outside the protective containment structure that surrounds the reactor itself.

Opponents of nuclear power have warned for years that if these pools drain, either by accident or terrorist attack, it could lead to a fire and a catastrophic release of radiation. Now, there have been hydrogen explosions <2> at two of the reactor buildings housing spent fuel pools at Fukushima

snip

At Fukushima, these tanks are attached to the outside of the reactor’s containment structure. The pools are deep – typically the fuel lies under 25 feet of water. Although the concrete-and-steel containment is designed to trap radiation leaks, there is no such protection for pools outside.

snip

The concern is that if the water in the pools ever drops too low, the zirconium cladding that holds the radioactive fuel pellets would begin to heat up and eventually burn. And if it did, the smoke from the fire could carry radiation away from the plant because the pool is outside the containment.

[Shallah Kali]

15. according to nytimes Fukushima #2 cooling pool was damaged in the big quake

In Stricken Fuel-Cooling Pools, a Danger for the Longer Term
By WILLIAM J. BROAD and HIROKO TABUCHI
Published: March 14, 2011
http://www.nytimes.com/2011/03/15/world/asia/15fuel.html?_r=2&partner=rss&emc=rssThe

The threat is considered so severe that at the start of the crisis Friday, immediately after the shattering earthquake, Fukushima plant officials focused their attention on a damaged storage pool for spent nuclear fuel at the No. 2 reactor at Daiichi, said a nuclear executive who requested anonymity because his company is not involved in the emergency response at the reactors and is wary of antagonizing other companies in the industry.

¶ The damage prompted the plant’s management to divert much of the attention and pumping capacity to that pool, the executive added. The shutdown of the other reactors then proceeded badly, and problems began to cascade.

snip

Depending on the freshness of the spent fuel, Mr. Lochbaum said, the water in an uncooled pool would start to boil in anywhere from days to a week. The water would boil off to a dangerous level in another week or two.

¶ Once most of the fuel is exposed, he said, it can catch fire.