Stricken Japan nuclear reactor past due date

TOKYO Sun Mar 13, 2011 8:31am EDT

TOKYO (Reuters) - A 40-year-old nuclear reactor facing a possible meltdown in northeastern Japan was originally scheduled to go out of commission in February but had its operating license extended another 10 years.

The earthquake-stricken No. 1 reactor operated by Tokyo Electric Power Co's Fukushima Daiichi power plant is the utility's oldest atomic core.

It was originally scheduled to operate only 40 years.

But the Japanese government's Nuclear and Industrial Safety Agency approved TEPCO's application to keep it hot after inspecting the facility, according to a statement on the Ministry of Trade Economy Industry's website.

Officials worked desperately to stop fuel rods in two damaged reactors from overheating after some controlled radiation leaks into the air to relieve pressure.

The fear is that if the fuel rods do not cool, they could melt the container that houses the core, or even explode, releasing radioactive material into the wind.

The government said there might have been a partial meltdown of the fuel rods at the No. 1 reactor. Engineers were pumping in seawater, trying to prevent the same happening at the No. 3 reactor.

Of Japan's 55 operational reactors, the No. 1 reactor is the nation's third oldest and one of the first built under a policy honed through oil shocks and burgeoning economic growth to give Japan more energy independence.

(Reporting by Tim Kelly. Editing by Jason Szep)

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Comments (2)
ahmedinho wrote:
The tsunami deaths will far out number any reactor melt down casualties.

Mar 13, 2011 9:56am EDT  --  Report as abuse
KarlQuick wrote:
From: Karl Quick
Date: Mar 12, 2011 6:57 PM
Subject: Nuclear disaster in Japan

What do you do when you find out that the World’s Experts a nuclear power have problems?

   …speaking as one once considered an expert, I’ve often said there are no REAL experts, just ex-sperts.  But that is another story.

The problem today is not with “nuclear power”… it is with a generation of power plants that are based upon 50 year old technology.  Water cooled uranium reactors are just one step beyond the carbon moderated designs used at Chernobyl.  For water cooled designs to be secure, massive backup systems are required:  containment, cooling, power, control, security, regulatory, etc.

Massive backups mean massive costs (massive containment structure, multiply redundant cooling system, multiply redundant emergency power to drive the redundant cooling system, redundant control systems, complex automation plus backups and overrides, large geographical area, major security fences/forces to protect all of the above, etc.)

Massive backup costs mean even more massive plant capacity is required in order to cover the costs of those backups, resulting in smaller risk, EXCEPT in the extreme where the risk now becomes truly massive!

There are a family of designs for “micro nuclear reactors” that use Thorium and other materials for fuel.  These reactors are SELF LIMITING.  Remove all cooling, they get hot… to a point, and the reaction self-limits, preventing any further heating.  And that limit point is sufficiently low to ensure the (small) containment vessel does not melt, fracture, or otherwise fail.

The “limit” is based on fundamental physical or chemical properties.  In one class of reactor, “doppler shift” (due to heat vibrating the atoms) shifts the radiation that would sustain the reaction to a energy level that reacts poorly with the remaining fuel, thus slowing and limiting the reaction.  In another class, a chemical reaction required to release the radioactive fuel slows down and stops as temps rise too high.

In these self limiting reactors, the “idle state” essentially is as hot as it ever gets.  When you cool the reactor to extract energy, the reaction speeds up due to the cooling, consuming fuel and generating energy in proportion to the amount of energy extracted, attempting to maintain the stable “hottest” temp the reactor can reach.

No pumps required to maintain the “idle state”; no energy required to “idle”.  It just sits there.  No operators, no switches to throw, no worries because it is inherently stable.  You pump a fluid into them only when you wish to extract the energy.  If you pump fails, the system returns to the idle state.

The idea is to build these things, bury them under 10 feet of soil, put a parking lot above them, run them for 20 years and dig them up to haul back to the factory for recycling.  The target is a reactor vessel that fits on a single 18 wheeler flatbed.

Prototypes have been built, but our mind set is on BIG, not small, so the investments needed to perfect and mass produce these things has not been done.  (Oh… should point out that these designs do not contain or produce material suitable for nuclear bombs as a by product of the reaction.  They are inherently non-proliferating as well as being self-limiting.)

They require a totally different operational model:  each major building or factory or subdivision or small town would have 1 or 10 or 100 of these sealed units located where power is needed.  Long power transmission lines would be a thing of the past.  Redundancy would be local based on using multiple local micro reactors rather than counting of massive plants, far away and redundant transmission lines to reliably service your local needs.

Unfortunately, this disaster may well delay, rather than accelerate the development of these new micro-reactor, self-limiting designs.  Our society continues to believe that “big is better”.  I prefer the other view:  ”The bigger they are, the harder they fall.” (…or should I say “fail”???)

Google or Bing “thorium reactors” to find multiple links supporting above.
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Mar 13, 2011 10:09am EDT  --  Report as abuse
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