Helicopter pictures show devastation inside Fukushima reactor towers

[Octafish]

Japan nuclear plant crisis: Helicopter pictures show devastation inside Fukushima reactor towers

These pictures show the devastation at Fukushima No.1 power plant as teams battle to keep radiation levels under control.

The nuclear power station is badly damaged in the aftermath of Friday's devastating earthquake and tsunami, which cut power supplies to the systems which keep reactors cool.

An explosion hit Reactor 4 on Tuesday after spent fuel caught fire. Reactor 3 has been the top priority for the team of 180 technicians, working in shifts of 50. The building suffered an explosion on Monday and has had the highest radiation levels.

Read more: http://www.mirror.co.uk/news/top-stories/2011/03/17/japan-nuclear-plant-crisis-helicopter-pictures-show-devastation-inside-fukushima-reactor-towers-see-the-photos-115875-22996869/#ixzz1Gt470Fw0
Go Camping for 95p! Vouchers collectable in the Daily and Sunday Mirror until 11th August . Click here for more information

-- The Mirror (UK) March 17, 2011

[The Straight Story]

1. K&R(nt)

[Octafish]

3. What engineers are saying...

Fukushima disaster: filling spent fuel ponds

The focus at the stricken Fukushima Daiichi nuclear power plant has turned to refilling with water spent fuel ponds in a bid to prevent dangerous radioactive releases, says IHS Energy Asia Pacific analyst Tom Grieder

EXCERPT...

There are a number of hurdles workers will face in filling up the spent fuel ponds. Given that fire and fuel rod exposure have already occurred, and given the lack of containment vessels, radiation levels will probably be among the highest in Fukushima Daiichi in the spent fuel area of Unit 4. These radiation levels will impede cooling efforts, as workers will be unable to stay near the ponds without suffering high and health damaging radiation doses. The strategy of using a helicopter to spray the spent fuel pond at Unit 4 is perhaps an acknowledgement of this radiation risk. However, the idea of spraying water onto a spent fuel pond would not be feasible if the zirconium cladding around the spent fuel rods was to ignite. Instead of helping to fill the pool, the water would then feed a reaction which would generate flammable hydrogen.

Furthermore, as in most nuclear power plants (NPPs) with boiling water reactors (BWRs), the spent fuel ponds are located high up in the reactor building—which raises accessibility issues. According to the latest JAIF status report, Unit 4 has sustained severe damage to reactor building integrity. This appears to be confirmed by recent images taken by satellites. World Nuclear News reports the damage appears to have been the result of a build-up of hydrogen in the spent fuel pond, which suggests the area around the pool itself would be most badly affected. However, the blast at Unit 3 on 13 March may also have contributed to the damage at Unit 4, suggesting other parts of the building may also be affected. Damage to Unit 4 could potentially cause debris to fall into the spent fuel pond, distorting rack structures, which would block air flows and potentially lead to temperature increases and ignition. There is also a more remote danger that the fuel ponds themselves might crack, which would severely undermine refilling efforts. However, cracking the spent fuel ponds would probably take a large hydrogen explosion, as they are usually made from reinforced concrete walls four to five feet thick and sometimes have stainless steel liners.

CONTINUED...

http://www.engineerlive.com/Power-Engineer/Nuclear_Power/Fukushima_disaster%3A_filling_spent_fuel_ponds/23355/"]

[onehandle]

2. Wow. That is fully exposed. Chernobyl indeed. nt

[Octafish]

4. A most difficult situation that could have been avoided -- with foresight and/or luck...

British scientist 'predicted nuclear power station problem'

EngineerLive.com
March 17, 2011

Back in 1967, a young UK nuclear scientist, Peter Harrop laboured to complete his PhD thesis under the sponsorship of the United Kingdom Atomic Energy Authority. It showed that well used water-cooled nuclear reactors had a vulnerability. The zirconium alloy used to clad the nuclear fuel becomes more chemically reactive after a prolonged and massive dose of neutrons caused by very extensive use. The thesis and the scientific papers resulting were quietly ignored.

After all, at the time, the UK generated electricity using gas-cooled nuclear reactors considered to be far safer. It only deployed water cooled nuclear reactors where their small size was essential - in nuclear submarines - and these were unlikely to be operated for many decades or pushed to their limits.

Indeed, massive over design was the order of the day for nuclear reactors in Europe and any Westerner suggesting siting a nuclear power station in an area subject to violent earthquakes would have been subject to a dry laugh.

Dr Peter Harrop, still a practicing scientist, explains: "When the outer building of the Japanese Fukushima No 1 reactor massively exploded, it was speculated that this was caused by hydrogen emitted from the overheated zirconium fuel cladding being in contact with cooling water. It is possible that, if this is true, just one of the contributory factors was that the zirconium alloy and its protective oxide film had built up neutron damage over nearly 40 years. Indeed the plant was about to be decommissioned in one month, having been commissioned in 1971."

CONTINUED...

http://www.engineerlive.com/Power-Engineer/Nuclear_Power/British_scientist_%26%23039%3Bpredicted_nuclear_power_station_problem%26%23039%3B/23354/

[thereismore]

5. Not yet. Not fully. Chernobyl did not have inner containment, which these reactors do

but you can't see it because it's smaller, shaped like a Russian doll.

[BeFree]

6. Yep

Problem is... if they can't get and keep water flowing into those 'cores' the cores might melt.

If the explosions damaged the piping to the cores the cores may not be getting the coolant needed.

If the cores melt, it is a whole new story.

[Chris_Texas]

7. Not really.

You are looking at the outer shell. While it has some minimal containment properties it's really there to protect things inside from the elements and make things look nicer. It's kinda like the hood on your car -- scratching the hood, hail damage, or even taking it off altogether has no effect on the engine.

Inside this, hidden from view, is the reactor itself. The nuclear fuel there is protected by multiple containments, at least two of which are designed to hold the fuel in the event of a total failure. The belief now, as I understand it, is that at least some fuel damage has occured. However, again, even if the fuel were to completely melt into a glowing pool of radioactive goo, the containment vessels are designed to hold it -- and there are TWO of them.

The battle has not been to prevent some kind of "China Syndrome" nonesense in which the core tunnels it's way to china, the battle for the reactor core has been to try and minimize internal damage -- initially so that the plant might go back into operation, and now that this is likely going to be prohibitively costly, to make shutting it down permanently easier to accomplish.

So far there is no indication that the main containments have failed or even been damaged, nor (to my knowlege) has anything occurred at the plant that could even conceivably do so.

[BeFree]

9. Heh

How did they form the steel to make the containment structure?
They melted it.

So, if there is no coolant for the core, the heat of the reactions in the core will remelt the metal container.

Of course, the heat inside may become so great that the container simply blows up.

3 options here: One it cools down and stays contained, two it melts the container, or three the container blows up.

Heard several days ago it would take 6 days of non-cooling before the container would give way.
Since they are not able so far to pump coolant........

[Octafish]

10. World Nuclear News

An excellent resource, FWICT:

http://www.world-nuclear-news.org/default.aspx

[joshcryer]

11. The main thing that they're worried about now is the spent fuel that is exposed to the air.

That stuff burns all by itself when exposed to air given enough time to get going.

[Octafish]

8. First aerial footage of damage to Fukushima plant

From The Telegraph.

New footage taken from above Fukushima's Daiichi nuclear power station shows the extent of the devastation caused by multiple explosions and fires.