Binswangled or Coatesified on Nuclear Safety?


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The new anti-nuclear epithet of the ecology freaks will be Dai-Ichi Fukushima. So far Chernobyl was much worse, but it was an exemplar of Soviet planning and technology. It was an abomination from the time it was planned to the time it blew up.

Move over TMI and and Chernobyl and make room for Fukushima.

The unfortunate thing is that Japanese engineers and planners subscribe to the same canons of engineering excellence and safety as do their counterparts in the advanced Western industrial economies. If grade-A nuclear plants cannot be run and managed safely, what then are the prospects for further development and deployment of nuclear fission generators?

The Japanese have not only turned their lights out, they have, in effect, darkened our future as well.

Ba'al Chatzaf

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There is a new basic reactor design good for slightly smaller nuclear plants than today's which doesn't require emergency cooling via water and complicated pumps, but I haven't heard about it for quite a while now. It doesn't matter, however, people are too scared.

--Brant

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There is a new basic reactor design good for slightly smaller nuclear plants than today's which doesn't require emergency cooling via water and complicated pumps, but I haven't heard about it for quite a while now. It doesn't matter, however, people are too scared.

--Brant

There have been several so-called inherently safe designs. These reactors will cool down without an infusion of water, which as we have found out does not happen if the cooling pumps do not get power. There is an inherent instability in the current generation of light water reactors.

See http://en.wikipedia.org/wiki/Pebble_bed_reactor

and

http://www.annualreviews.org/doi/abs/10.1146/annurev.eg.10.110185.002243?journalCode=energy.1

Ba'al Chatzaf

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NYT tonight:

"the unnamed operators [are pumping] seawater on dangerously exposed nuclear fuel, already thought to be partly melting and spewing radioactive material, to prevent full meltdowns that could throw thousands of tons of radioactive dust high into the air and imperil millions of their compatriots. "

Read "Nerves" by Lester DelRey.

BTW, the one thing the stories I've read recently have not filled me in on is what about the damn control rods? Why can't they be inserted by those 'unnamed operators' currently working at the nuclear plants?

Has anyone read why that wouldn't dampen the reaction, cut off the heat production, solve the meltdown issues?

Edited by Philip Coates
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Phil,

Upon the seismic event, all control rods inserted fine, within 10 seconds, as designed. That stopped the fission reactions that were producing heat for steam. But the core continues to produce heat from radioactive decay of fission products, and this heat must be removed by circulating cooling water, which requires pumps that must be powered by electricity from the emergency diesel generators (if offsite power is unavailable, as in this case). Boric acid is being added to the seawater flooding of these reactors because boric acid absorbs neutrons, which are freed in the natural radioactive decays (of the decay products from the earlier controlled nuclear reactions), neutrons that can increase decay rates and heat.

See the link I gave in #17 for "BWR Safety Systems." Of special interest would be the last couple of paragraphs.

The link I gave for "Competent Updates"* continues to be a reliable prompt report of developments in this nuclear incident.

It is my understanding that the total loss of emergency backup power for these BWR units was due to the diesel generators being located underground, where they were incapacitated by the tsunami. The fundamental human failures appear to have been design, not maintenance or operations. Conditions have struck this plant that were beyond its "Design Basis Accident."

"Nerves"---I had forgotten all about that. A good short story my college roommate showed to me back when the earth was cooling.

Edited by Stephen Boydstun
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> control rods...stopped the fission reactions that were producing heat for steam. But the core continues to produce heat from radioactive decay of fission products, and this heat must be removed by circulating cooling water, which requires pumps that must be powered by electricity

Thanks, Stephen. Makes sense.

> It is my understanding that the total loss of emergency backup power for these BWR units was due to the diesel generators being located underground, where they were incapacitated by the tsunami.

But where can you locate electrical generators so they are unlikely to be knocked out by massive earthquake and/or tsunami (if you site a nuclear plant and its backup power sources in a fault/coastal zone)?

Edited by Philip Coates
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> control rods...stopped the fission reactions that were producing heat for steam. But the core continues to produce heat from radioactive decay of fission products, and this heat must be removed by circulating cooling water, which requires pumps that must be powered by electricity

Thanks, Stephen. Makes sense.

> It is my understanding that the total loss of emergency backup power for these BWR units was due to the diesel generators being located underground, where they were incapacitated by the tsunami.

But where can you locate electrical generators so they are unlikely to be knocked out by massive earthquake and/or tsunami (if you site a nuclear plant and its backup power sources in a fault/coastal zone)?

Please have a look at this:

http://www.voximate.com/blog/article/1058/failover-backup-systems-redundant/

Ba'al Chatzaf

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. . .

But where can you locate electrical generators so they are unlikely to be knocked out by massive earthquake and/or tsunami (if you site a nuclear plant and its backup power sources in a fault/coastal zone)?

See design at San Onofre

The real solution is the so-called inherently safe design, the pebble bed reactor.

From the wiki article:

This type of reactor is claimed to be unique because its passive safety removes the need for redundant, active safety systems. Because the reactor is designed to handle high temperatures, it can cool by natural circulation and still survive in accident scenarios, which may raise the temperature of the reactor to 1600°C. Because of its design, its high temperatures allow higher thermal efficiencies than possible in traditional nuclear power plants (up to 50%) and has the additional feature that the gases do not dissolve contaminants or absorb neutrons as water does, so the core has less in the way of radioactive fluids. A number of prototypes have been built. Active development continued in South Africa until 2010 as thePBMR design, and in China whose HTR-10 is the only prototype currently operating.

(end quote)

------------------------------------------------------------------------------------------------------

The conventional boiling water reactor has a built in lack of stability. After the reactor is "scrammed" the the fuel rods are withdrawn into their moderator sheaves (usually done by gravity dropping) there is a period of time when heat must be exhausted from the inner containment vessel (where the fuel rods are). When enough heat is removed and the temperature brought down sufficiently (a matter of hours or days) then the vessel and its shielded contents will sit there nice and quiet. HOWEVER , if the cooling phase cannot be completed the water in the reactor will be boiled away exposing the rods and the reactor will begin to heat up in an uncontrolled fashion. Eventually the fuel matrix will melt and burn through the bottom of the containment and at that point the nuclear shit has hit the fan. T

Between the "scramming" of the fuel load and being made sufficiently cool there is a period on instability and if the cooling fails in that period of instability a positive feedback produces increasing temperature leading to the breech of the containment vessel.

What the engineers at Fukushim Dai-Ichi did was flood the containment with borated sea water. This is the last act of despair to prevent melt-down. Most likely it will work, with some danger of explosion. The sea water is set a-boiling and the steam must be vented periodically to prevent the pressure in the containment vessel from exceeding its design limits. Letting out the steam also releases some radioactivity and also free hydrogen gas (at this point very hot) which when mixed with the oxygen of the atmosphere go Boom. You will note that the outer buildings surrounding the inner reactor vessels have been set afire or blown to smithereens.

The sea-water gambit will probably prevent melt down but the reactor ishe reactors at Fukushim Dai-Ichi are a forty year old design (I think they are General Electric reactors). The plant is ten years beyond its decommissioning date. When a boiling water reactor works, it works just fine, but it has the previously indicated inherent instability. forever ruined. It will never generate another kilowatt of electrical power.

The URL for the Wiki article is http://en.wikipedia.org/wiki/Pebble_bed_reactor

Ba'al Chatzaf

Edited by BaalChatzaf
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  • 5 years later...
28 minutes ago, Guyau said:

.

Update on Potentials of US Nuclear Power

Sorry to see the closings, such as San Onofre. 

As am I.  We should be paving the nation from Atlantic to Pacific with breeder reactors and thorium reactors.  We will be able to generate all the hydrogen we need for nice clean hydrogen powered  cars  and handy dandy fuel cells.    

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