Jet streams could carry radioactivity from Japan to the US

The control rods slow down the neutrons; to make the reactor work, they're pulled out - to slow it down, they're dropped (or pushed) in:

Cheers! Rich

Or, you're the type to confuse up/down, in/out, hi/lo and so on?

They push all the control rods in and the reactor output goes from 100% to 7%/.

It's that 7% of full output which is causing the trouble, from my recent reading. The other source of trouble is the storage pond for used rods, adjacent to the reactor. The water level goes down exposes fuel rods to air, they heat up and crack the water to produce hydrogen, which explodes, blowing the buildings roof off. But not hurting the reactor containment.

Thus the radioactive materials coming out of the damaged plants is from the spent rods, not the reactor core.

Grant.

Perhaps. But that isn't much of a decent threshold of acceptance, either. And the story provides an interesting series of failures, which gives one pause:

"The accident began about 4:00 a.m. on March 28, 1979, when the plant experienced a failure in the secondary, non-nuclear section of the plant. The main feedwater pumps stopped running, caused by either a mechanical or electrical failure, which prevented the steam generators from removing heat. First the turbine, then the reactor automatically shut down. Immediately, the pressure in the primary system (the nuclear portion of the plant) began to increase. In order to prevent that pressure from becoming excessive, the pilot- operated relief valve (a valve located at the top of the pressurizer) opened. The valve should have closed when the pressure decreased by a certain amount, but it did not. Signals available to the operator failed to show that the valve was still open. As a result, cooling water poured out of the stuck-open valve and caused the core of the reactor to overheat.

"As coolant flowed from the core through the pressurizer, the instruments available to reactor operators provided confusing information. There was no instrument that showed the level of coolant in the core. Instead, the operators judged the level of water in the core by the level in the pressurizer, and since it was high, they assumed that the core was properly covered with coolant. In addition, there was no clear signal that the pilot- operated relief valve was open. As a result, as alarms rang and warning lights flashed, the operators did not realize that the plant was experiencing a loss-of-coolant accident. They took a series of actions that made conditions worse by simply reducing the flow of coolant through the core."

So, * man feedwater pump __fails__ * turbine and reactor shuts down and pressures increase * pilot valve opens but __fails__ to close * signals to the operator __failed__ to show this fact * so cooling water vented out of the open pilot valve * no instrument existed to show the level of coolant!!

Worth noting. Design failures (no instrumentation for more directly measuring coolant level, for example) combined with ad-hoc failures of a pump system, pilot valve, and pilot valve condition readout, at the very least. Makes you wonder what other design lacks, instrumentation failures, or component or system failures were present and unaccounted for because they were not tested by the event.

By the way, I support nuclear power in the US and the people who, I believe, do work very hard and at-risk to provide a resource we use with far too little appreciation. But that doesn't mean I do so with eyes closed.

There is a cozy relationship between the NRC and plant operators (MOA between INPO and NRC, for example) an NRC licensing process for early site approval and certification of plant designs by rule (avoiding public hearings for each plant) that provides for simultaneous issuances of both a construction permit and an operating license as a one-stop licensing called "combined licenses," the Price-Anderson Act capping to ridiculously low numbers their liability and completely hides the costing out of risk (and would be better handled via the usual private business insurance mechanisms), to name a few things. I'd also like a mechanism for adversarial, informed disputes to take place. There is none, right now.

We can do better, and should.

Jon

Use that stuff called "concrete" where appropriate. That's what we do in SF.

John

towards the US.

But then you have to pump the water uphill, which might fail in a tsunami. Wouldn't it be better to have the plant at sea level, so the water can flow easily without a lot of pumping? Gravity cooling system or somesuch?

-Bill

ds

um?

Slow them down to a stop, actually.

Salt domes do not move. Salt domes do not 'flow'. They are about as static and stable as it gets, and that even through earthquakes.

It isn't a layer, it is a giant monolith. Think Mt. Everest upside down.

Get a clue after that.

You're an idiot.

t as

Deaf Smith county Texas was the ideal site for nuclear storage if based on science.

You have.

Control rods (boron) absorb neutrons, which decreases the energy output.

The moderator (typically water or graphite; water at Fukushima, graphite at Chernobyl) slows down neutrons, which increases the probability of collision and thus increases the energy output.

An advantage of a water-cooled, water-moderated reactor is that the coolant is the moderator, so a loss of coolant naturally decreases the energy output. Unfortunately, the decrease in energy output takes some time to take effect, while the decrease in cooling doesn't.

The 400mSv/hr event (on the 13th) was real (at least, not retracted) but localised and transient; that triggered the evacuation of non-essential staff.

The[1] prefix mix-up was more recent, and related to "ongoing" levels.

[1] The one where the government official actually said mSv then corrected. Cases where the media have confused the two (or confused per-hour and per-year) are too numerous to count.

+1

It's a bit like measuring the risk of being in the middle of a gunfight in terms of atmospheric lead concentration.

Measuring radiation levels with a Geiger counter is reasonable enough for determining the risk from direct exposure to plant workers. To measure the risk to the public from pollution, you need to move a known amount of air through a filter and see what it catches.

It also seems to be an oxymoron.

It's difficult to manage a very small risk with very serious consequences. If you start with adequate safety margins, you can screw up quite a lot and you'll probably get away with it most of the time. Probably.

This results in pressure to tolerate corner-cutting.

I suspect that Japan is more susceptible to this issue than the west. Their emphasis on agreement and compromise may make for a orderly society, but it doesn't necessarily make for sound nuclear safety policy. The Confucianist notion that important people (e.g. CEOs) are owed deference from the little people (which includes the bureaucrats who are supposed to be regulating them) probably doesn't help.

But those accidents aren't a danger to people who don't actually work in those industries (i.e. most of the population). And people seem to think that radiation from coal is just something the tree-huggers made up to try to scare people away from coal.

I don't know about the height issue. But putting 4 reactors next to each other seems to have been an issue. A hydrogen explosion at #2 damaged the pumps used to cool #3, operation of #3 was temporarily abandoned due to radiation from the spent fuel pool at #4.

OTOH, I suppose that one exclusion zone is better than four.

I fear that journalism schools don't teach the difference between an amount and a rate, nor do they teach that a million is somehow different from a billion.

They do teach that distances are always measured in football fields.

John

The worst thing that can happen to a GE-type boiling-water reactor isn't all that bad. Chernobyl was a graphite pile that never should have been used as a power plant.

Used fuel-rod storage inside the containment building was really stupid. The fix is to not do that.

The biggest mistake was to put the backup diesels in the basement, where they were submerged by the tsunami.

John

And, I imagine, in conditions which are at least halfway normal, having the reactors in close proximity probably adds to the safety of the operation. As long as at least one reactor is operating, it would be producing far more power than is needed to keep the cooling pumps in the other reactors functioning correctly.

The emergency diesel generators would be needed for this purpose only if (1) all of the reactors are shut down at the same time and (2) the power grid is sufficiently damaged that power cannot be brought in from other power plants.

In effect, having multiple reactors on-site allows you to maintain an extra level of backup for the cooling-pump power: your other reactor(s), grid feed, and on-site generators.

Unfortunately, that's just what happened last week... the massive damage from the quake and tsunami was enough to knock out all of these power sources within a few minutes.

I wonder whether, paradoxically, it might even have been safer in this case to leave one or more of the reactors running at reduced power rather than hitting the SCRAM button on all of them... darned hard to make a decision about that "in the moment", though.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
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Of course, I ain't there, but to me, I wonder...

Don't they have mobile diesel generators, like in their military?

Have they heard of fireships?

Can't they put a ship off shore, and run power lines from it to the plant? Most ships have plenty of spare electrical power, esp. military vessels.

How long to rehab those wet diesels?

At San Onefre (sp?) they have a 30 foot tsunami wall around the plant, just in case!

Charlie

They don't teach them geography. A local newscaster stated that the radioactive particles would pass over Alaska, not the United States.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

towards the US.

The US Army had several portable nuclear reactors as part of their research in the '50s through the '70s. The SM-1A was built at Ft. Greely Alaska in the '60s and decommissioned in the '70s.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.