Spent fuel pools may be compromised, built on top of reactor #3

[flamingdem]

http://www.japanfocus.org/events/view/51

* This includes MOX fuels

Japan's Nuclear Crisis: Status of Spent Fuel at Exploded Reactor Buildings Unclear Back
Mar. 14, 2011:

By John McGlynn -- The Institute for Energy and Environmental Research (IEER) is asking an important question about Japan's nuclear crisis that seems to have been ignored by the media and in announcements from the Japanese government and Japan's nuclear power industry: What is happening with the spent fuel pools located at the top of the buildings housing the Unit 1 and Unit 3 reactors at the Fukushima Daiichi nuclear power plant facility? Both reactor buildings have lost their upper structures due to explosions possibly caused by a hydrogen gas build-up (Unit 1 on March 12, Unit 3 on March 14).


IEER writes in its analysis of the situation at the Daiichi nuclear facility: "While Japanese authorities have stated that the reactor vessel is still intact , there has been no word regarding the status of the spent fuel pool structure, except indirectly. Is it still intact? This is a critical question as to the range of potential consequences of the reactor accident."


The New York Times has a visual that indicates the location of the spent fuel pool near the top of the reactor vessel (here; see frame #3 of The Crippled Japanese Nuclear Reactors)



This excerpt from the analysis highlights the dangerous implications of any disruption of the spent fuel pools by the two reactor building explosions:



"Both reactors are of the Mark 1 Boiling Water Design. They do not have the sturdy secondary containment buildings of concrete that is several feet thick typical of later reactor designs.



A special feature of the Mark 1 design is that the used fuel, also called spent fuel, is stored within the reactor building in a swimming pool like concrete structure near the top of the reactor vessel. When the reactor is refueled, the spent fuel is taken from the reactor by a large crane, transferred to the pool, and kept underwater for a few years. This spent fuel must be kept underwater to prevent severe releases of radioactivity, among other reasons. A meltdown or even a fire could occur if there is a loss of coolant from the spent fuel pool. The water in the spent fuel pool and the roof of the reactor building are the main barriers to release of radioactivity from the spent fuel pool."

[meow mix]

1. thats what i was sayin, the "pool area" looks completely wrecked from the bad photos we have

fuck

thread from earlier http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=439&topic_id=641546&mesg_id=641601

[flamingdem]

3. Dr. Robert Alvarez says that he sees steam coming off of them meaning boiling

‎
foe_us‎ #JapanNuclearQs Dr. Robert Alvarez: Spent fuel pools on top of reactor buildings, not contained. Explosion could compromise water storage
Twitter -
9435
2 hours ago

[aquart]

4. Does it seem silly to keep spent fuel in that configuration?

[Statistical]

7. It is a 1960s design.

More modern designs look like this...



Separate containment around fuel handling building and a tunnel (which seals in an emergency connecting the two).

When fuel comes out of a reactor it is hot. It can't be handled by humans. That heat (both physical heat and radioactivity) will decay massively over the course of year. Radioactive output decays by about 99% 1 year after removal from a reactor.

So for the first couple years the fuel needs to be stored in cooling ponds. First inside containment and then later outside containment. Finally after about 20 years it is cool enough for dry storage.

So fuel handling machine attached to a crane removes fuel from reactor and it is HOT. Can't allow it to access open atmosphere so you put it in a cooling pond. In these old designs the pond is right next to the reactor. In more modern designs the fuel handling machine can turn the fuel rods sideways (90 degrees) and a conveyer belt moves it to the fuel handling building next door.

[Ghost Dog]

11. Hard to see through the melted steel:

[meow mix]

13. ouch

much bigger blast in there

[Ghost Dog]

14. 'Fraid so. See some discussion here:

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=439x642514

(and see the Reuters live blog: http://live.reuters.com/Event/Japan_earthquake2 )

[bluecoat_fan]

2. You have to be kidding!

[snagglepuss]

6. 600 tons of spent fuel are stored in pools inside the individual reactor buildings

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=439&topic_id=639439&mesg_id=639439

[flamingdem]

9. I don't think they factored a tsunami into the equation, yikes nt

[bluecoat_fan]

15. TEPO presentation says they are(were) inside the building

http://www.nirs.org/reactorwatch/accidents/6-1_powerpoint.pdf

[snagglepuss]

16. Yes they are inside the building basically above the reactors.

[flamingdem]

5. Dr. Alvarez calls seawater a "hail Mary pass"

http://www.nbc29.com/story/14240218/in-japan-plant-frantic-efforts-to-avoid-meltdown

-snip
Robert Alvarez, senior scholar at the Institute for Policy Studies and former senior policy adviser to the U.S. secretary of energy, said in a briefing for reporters that the seawater was a desperate measure.

"It's a Hail Mary pass," he said.

He said that the success of using seawater and boron to cool the reactor will depend on the volume and rate of their distribution. He said the dousing would need to continue nonstop for days.

Another key, he said, was the restoration of electrical power, so that normal cooling systems can be restored.

Officials placed Dai-ichi Unit 1, and four other reactors, under states of emergency Friday because operators had lost the ability to cool the reactors using usual procedures.

An additional reactor was added to the list early Sunday, for a total of six - three at the Dai-ichi complex and three at another nearby complex. Local evacuations have been ordered at each location. Japan has a total of 55 reactors spread across 17 complexes nationwide.

Officials began venting radioactive steam at Fukushima Dai-ichi's Unit 1 to relieve pressure inside the reactor vessel, which houses the overheated uranium fuel.

Concerns escalated dramatically Saturday when that unit's containment building exploded.

It turned out that officials were aware that the steam contained hydrogen, acknowledged Shinji Kinjo, spokesman for the government Nuclear and Industrial Safety Agency. More importantly, they also were aware they were risking an explosion by deciding to vent the steam.

The significance of the hydrogen began to come clear late Saturday:

-Officials decided to reduce rising pressure inside the reactor vessel, so they vented some of the steam buildup. They needed to do that to prevent the entire structure from exploding, and thus starting down the road to a meltdown.

-At the same time, in order to keep the reactor fuel cool, and also prevent a meltdown, operators needed to keep circulating more and more cool water on the fuel rods.

-Temperature in the reactor vessel apparently kept rising, heating the zirconium cladding that makes up the fuel rod casings. Once the zirconium reached 2,200 degrees Fahrenheit (1,200 Celsius), it reacted with the water, becoming zirconium oxide and hydrogen.

-When the hydrogen-filled steam was vented from the reactor vessel, the hydrogen reacted with oxygen, either in the air or water outside the vessel, and exploded.

A similar "hydrogen bubble" had concerned officials at the 1979 Three Mile Island nuclear disaster in Pennsylvania until it dissipated.

If the temperature inside the Fukushima reactor vessel continued to rise even more - to roughly 4,000 degrees Fahrenheit (2,200 Celsius) - then the uranium fuel pellets would start to melt.

According to experts interviewed by The Associated Press, any melted fuel would eat through the bottom of the reactor vessel. Next, it would eat through the floor of the already-damaged containment building. At that point, the uranium and dangerous byproducts would start escaping into the environment.

At some point in the process, the walls of the reactor vessel - 6 inches (15 centimeters) of stainless steel - would melt into a lava-like pile, slump into any remaining water on the floor, and potentially cause an explosion much bigger than the one caused by the hydrogen. Such an explosion would enhance the spread of radioactive contaminants.

If the reactor core became exposed to the external environment, officials would likely began pouring cement and sand over the entire facility, as was done at the 1986 Chernobyl nuclear accident in the Ukraine, Peter Bradford, a former commissioner of the U.S. Nuclear Regulatory Commission, said in a briefing for reporters.

Another expert on the call, Ken Bergeron, a physicist and former Sandia scientist, added that as a result of such a meltdown the surrounding land would be off-limits for a considerable period of time, and "a lot of first responders would die."

___

AP National Writer Jeff Donn reported from Boston.

[flamingdem]

8. Fuel ponds hold 5-10 x more than reactor core, more from Alvarez

https://alethonews.wordpress.com/2011/03/14/meltdown-at-fukushima/

--snip
On average, spent fuel ponds hold five-to-ten times more long-lived radioactivity than a reactor core. Particularly worrisome is the large amount of cesium-137 in fuel ponds, which contain anywhere from 20 to 50 million curies of this dangerous radioactive isotope. With a half-life of 30 years, cesium-137 gives off highly penetrating radiation and is absorbed in the food chain as if it were potassium.

In comparison, the 1986 Chernobyl accident released about 40 percent of the reactor core’s 6 million curies. A 1997 report for the Nuclear Regulatory Commission (NRC) by Brookhaven National Laboratory also found that a severe pool fire could render about 188 square miles uninhabitable, cause as many as 28,000 cancer fatalities, and cost $59 billion in damage. A single spent fuel pond holds more cesium-137 than was deposited by all atmospheric nuclear weapons tests in the Northern Hemisphere combined. Earthquakes and acts of malice are considered to be the primary events that can cause a major loss of pool water.

In 2003, my colleagues and I published a study that indicated if a spent fuel pool were drained in the United States, a major release of cesium-137 from a pool fire could render an area uninhabitable greater than created by the Chernobyl accident. We recommended that spent fuel older than five years, about 75 percent of what’s in U.S. spent fuel pools, be placed in dry hardened casks — something Germany did 25 years ago. The NRC challenged our recommendation, which prompted Congress to request a review of this controversy by the National Academy of Sciences. In 2004, the Academy reported that a “partially or completely drained spent fuel pool could lead to a propagating zirconium cladding fire and release large quantities of radioactive materials to the environment.”

Given what’s happening at the Fukushima Daiichi nuclear complex, it’s time for a serious review of what our nuclear safety authorities consider to be improbable, especially when it comes to reactors operating in earthquake zones.

[snagglepuss]

10. Authorities including Congress know about this but authorites have dismissed

saftey concerns.

A 2006 report requested by Congress covered questions about the safety of spent nuclear storage pools.

snip

The study provided a probabilistic risk assessment that identified severe accident scenarios and estimated their
consequences. The analysis determined, for a given set of fuel characteristics, how much time would be required to boil off enough water to allow the fuel rods to reach temperatures sufficient to initiate a zirconium cladding fire.

The analysis suggested that large earthquakes and drops of fuel casks from an overhead crane during transfer operations were the two event initiators that could lead to a loss-of-pool-coolant accident. For cases where active cooling (but not the coolant) has been lost, the thermal-hydraulic analyses suggested that operators would have about 100 hours (more than four days) to act before the fuel was uncovered sufficiently through boiling of cooling water in the pool to allow the fuel rods to ignite. This time was characterized as an “underestimate” given the simplifications assumed for the loss-of-pool-coolant scenario.

The overall conclusion of the study was that the risk of a spent fuel pool accident leading to a zirconium cladding fire was low despite the large consequences because the predicted frequency of such accidents was very low. The study also concluded, however, that the consequences of a zirconium cladding fire in a spent fuel pool could be serious and, that once the fuel was uncovered, it might take only a few hours for the most recently discharged spent fuel rods to ignite.



http://www.nap.edu/openbook.php?record_id=11263&page=44

[suffragette]

12. I was wondering about this myself on Saturday

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=439x628859#629373