Fukushima Nuclear Worker Accidentally Toggles Off Cooling Pumps

An anonymous reader writes "A Tepco employee carelessly pressed a button shutting off cooling pumps that serve the spent fuel pool in reactor #4 — thankfully a backup kicked in before any critical consequences resulted. The question remains just how vulnerable to simple mistakes (such as a single button push) are these spent fuel pools, filled nearly to capacity as they are with over 12,000 spent fuel rods? From the article: 'The latest incident is another reminder of the precarious state of the Fukushima plant, which has suffered a series of mishaps and accidents this year. Earlier this year, Tepco lost power to cool spent uranium fuel rods at the Fukushima Daiichi plant after a rat tripped an electrical wire.'"

Comments

Evidently not that vulnerable

[Anonymous Coward]

since a backup system kicked in to prevent any critical consequences.

Re:Evidently not that vulnerable

[Anonymous Coward]

I think the point is not that no disaster occurred, it is that a failure of the primary system happened for whatever reason. Remember that the backup generators failed during the tsunami. On a different day, this inadvertent power off might have been worse.

Ideally you have no unexpected failures, and at least one redundant backup.

The sad thing about all this is that at least one of the Fukushima reactors began to fail before the tsunami even hit the buildings (due to the original quake). Would a simple quake now bring the rest of the system to failure state? Japan is an earthquake haven.

Re:Evidently not that vulnerable

[Anonymous Coward]

While I AM of the opinion that Fukushima remains a challenge and threat to entire humankind, these kinds of articles are not helpful. The backup system in this case is kind of irrelevant, but more so than that, now over 3 years since the reactor core was offloaded into the cooling pool, all calculations and evidence (from intentional, several days long cooling outages) points to that the pools could remain without cooling for weeks with no "critical consequences". Moreover, in such a case that something is amiss would be detected long before critical consequences allowing the situation to be rectified.

General consensus is that even in case of sudden loss of water in the pool, 3 years old irradiated fuel bundles could easily be cooled by air convection from their own heat alone, although for somewhat obvious reasons that hasn't been tested out. In addition radiation would then make working on the site even harder than now. The critical failure mode for this particular setup is loss of coolant with air convection blocked (such as by rubble from the initial explosion, or the temporary cover they had installed in the early months) or structural failure of the building in case of another earthquake in particular, or simply from the prior damage and ground subsidence due to groundwater changes etc. Or prompt criticality incident due to unfavorable geometry of the nuclear material from damage or attempts to remove the fuel bundles.

The occurrence of human error is, "human", but extremely worrisome in that they have zero margin of error once the removal of the fuel bundles from the pool starts in the coming months. Due to the sheer number of the bundles in the pool (1535 give or take), any chance of mistake would spell almost certain disaster. Even if they somehow press the chance of serious human error to 0,01 percent (one percent of one percent) per bundle the chance of everything running smoothly is 0,9999 to the power or 1535 or 85,8%, leaving a 14.2% chance of disaster for the whole operation. A worker allegedly failing in this basic task under less stressful circumstances isn't necessarily relevant, but it's tempting to consider it not boding well for the future prospects.

Re:Evidently not that vulnerable

[Anonymous Coward]

Go hit the red button in your data center to see how vulnerable it is. it has a backup system I assume so it can't be that vulnerable.

Re:Evidently not that vulnerable

[IndustrialComplex]

I think the point is not that no disaster occurred, it is that a failure of the primary system happened for whatever reason. Remember that the backup generators failed during the tsunami. On a different day, this inadvertent power off might have been worse.

Ideally you have no unexpected failures, and at least one redundant backup.

I think the bigger point here is that even though someone pressed the wrong button, the system didn't go into a catastrophic failure mode. You can't expect that every failure possiblity be prevented, only that no single failure leads to a catastrophic failure.

Re:Evidently not that vulnerable

[ShanghaiBill]

Ideally you have no unexpected failures, and at least one redundant backup.

In this case, they did have redundant backups. The first backup plan was the one that automatically kicked in. The second backup plan, is that sometime over the next few minutes, hours, or days, but long before it was actually a problem, someone would have noticed that no water was being pumped, and would have turned the pumps back on. It would have only been a problem if left long enough for the cooling water to boil off, and that would have taken awhile. TEPCO has made a lot of big mistakes, but this isn't one of them. This is being blown out of proportion ... and I say that as a tree-hugging environmentalist who thinks that nukes are a bad idea.

Wow ...

[gstoddart]

Am I imagining things, or does it sound like a nuclear plant is being operated by a company without the barest idea of how to do that?

Accidentally flipping off the cooling pumps in a nuclear plant sounds like something which shouldn't even be physically possible.

Re:Wow ...

[SirGarlon]

It sounds like the company has a pretty good idea of how and where to use backup systems, actually.

Re:Wow ...

[TheResilientFarter]

This is my thinking, but it's the employees, thus management, that are the problem, not the equipment. I worked in the Naval Nuclear Power Program, where everything was essentially manual. One single operator could cause a meltdown, yet the U.S. Navy is one of the largest and one of the oldest operators of nuclear power plants (by hours critical) and has a spotless safety record. Keep in mind that the average age of the 'employees' is around 22 or 23, with a very low percentage of them over age 26.

Re:Wow ...

[bobbied]

Keep in mind too, that the Navy is not interested in making a profit. It's goal is to keep it's resources available (afloat, underway and mission capable) under the most difficult circumstances. They can afford to have many times the number of people operating a power plant and they utilize their people to keep their plants operating sans automation. The Navy is not interested in being efficient either. They routinely power cycle their plants and burn though more fuel than they other wise would. They also are not risk adverse. In time of war, they would have no problem pushing their reactors beyond the design limits if the mission demanded it.

Electric power generation is about efficiency and safety. It's more efficient to automate and not pay operators, so they automate their plants, and operate within very narrow operating parameters. They are risk adverse and would rather scram a reactor and go off line than risk operating outside of their design limits.

The navy does have an enviable safety record. But what you really are saying is that the safety of nuclear power is really something to be trumpeted. Except for some research accidents, the worst US event in history was Three Mile Island and that was pretty much nothing. When you put Japan into the mix, things get more interesting, but who can really complain about that? The earthquake was well beyond design limits and even then the damage, while significant, is going to be manageable. It's just going to take a few decades for things to radioactively cool.

Re:Wow ...

[NatasRevol]

Because they didn't know how to protect primary systems.

Huh?

[Antipater]

'The latest incident is another reminder of the precarious state of the Fukushima plant...'

So something unexpected occurred, but automatic backups stepped in and prevented any negative consequences. While the plant may or may not be in a precarious state, this is hardly the example to be using for a FUD article. Hell, change the spin around and it could be used in a TEPCO press release showing how far they've come in stabilizing the situation.

Re:Huh?

[AmiMoJo]

They failed to train the employees properly and allowed a critical function to be operated by someone who clearly didn't understand it. In this instance the backup saved them, but relying on backups is not a good policy. To put it another way, they can't ignore this incident and simply rely on the backups in future, they have to take steps to correct it.

Where's the problem?

[Anonymous Coward]

A human made a mistake which was caught and corrected by an engineered system. Seems like a non-story.

Working as intended

[DerekLyons]

"A Tepco employee carelessly pressed a button shutting off cooling pumps that serve the spent fuel pool in reactor #4 - thankfully a backup kicked in before any critical consequences resulted."

Um - that's what backups are for. Seriously, this is just another ignorant journalist generating controversy from thin air to get the site he works for some page views.

Re:Just another sign of TEPCO's incompetence...

[icebike]

That the Japanese government a) allows TEPCO to 'clean up' Fukushima and b) refuses any foreign help shows that the problem with Fukushima is and always has been a political one.

If the Japanese government is anything like our government, (or most governments), suddenly tossing them into a critical situation in a plant they are not familiar with (which is already fundamentally compromised), is just BEGGING for a far worse Chinese fire-drill than is currently going on.

If it is in fact a political problem as you suggest, then implying that the government should do anything differently is pointless, because governments are, by definition, political.