Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors

The Fukushima nuclear disaster was “predicted” or foreseen in type by the Ergen report of 1967. As a result of the fundamental flaw of reactor design – an insurmountable one to this day – nuclear authorities in the USA imposed design rules for Emergency Core Cooling systems for all US designed (including the design sold by the USA to Tepco, Japan). These design rules in full are here:

http://nuclearhistory.wordpress.com/2012/09/22/acceptance-criteria-for-emergency-core-cooling-systems-for-light-water-nuclear-power-reactors/

At the time of the 1970s Public Hearings in the US, nuclear industry lied and stated that the rules would prevent reactor core meltdown and resultant containment failure.

One salient rule is the following:

http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0046.html

UNITED STATES NUCLEAR REGULATORY COMMISSION

“50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors….

“(b)(1) Peak cladding temperature. The calculated maximum fuel element cladding temperature shall not exceed 2200° F.
(2) Maximum cladding oxidation. The calculated total oxidation of the cladding shall nowhere exceed 0.17 times the total cladding thickness before oxidation. As used in this subparagraph total oxidation means the total thickness of cladding metal that would be locally converted to oxide if all the oxygen absorbed by and reacted with the cladding locally were converted to stoichiometric zirconium dioxide. If cladding rupture is calculated to occur, the inside surfaces of the cladding shall be included in the oxidation, beginning at the calculated time of rupture…..

“(3) Maximum hydrogen generation. The calculated total amount of hydrogen generated from the chemical reaction of the cladding with water or steam shall not exceed 0.01 times the hypothetical amount that would be generated if all of the metal in the cladding cylinders surrounding the fuel, excluding the cladding surrounding the plenum volume, were to react.
(4) Coolable geometry. Calculated changes in core geometry shall be such that the core remains amenable to cooling.
(5) Long-term cooling. After any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.
end quote.

As the Fukushima nuclear disaster unfolded, reactor after reactor exploded. “Nuclear experts” providing narrative to Australian media outlets described these explosions as being “perfectly normal”, “consisting of merely Hydrogen gas/”

No such expert fully explained that the mass produced reactor explosions were vivid demonstrations of the fact that ECCS as designed and regulated by the USA, being imposed upon the design of the US originated Fukushima reactors, were patently inadequate. That the rules merely stated a criteria which was known to be impossible to achieve in the real world in the event of the ECCS actually be called upon to work.

Criteria sub paragraph (5) is most troubling. It calls for the ECCS to contiue to work for months: “Long-term cooling. After any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.

Yet we learn from the American Nuclear Society that the US designed (incorporating a claimed conforming with the US Design Criteria above) to operate not for the length of time the longest lived radioctivity remaining in the core demanded, (months) but EIGHT HOURS.

I refer to :

American Nuclear Society Committee Report on Fukushima Diiachi

http://fukushima.ans.org/report/accident-analysis

In relation to the designed life of that part of the Emergency Core Cooling System known as the RCIC, the ANS report states: ” In general, one should not expect the RCIC system to run much beyond 8 hours in a station blackout (SBO)“.

The ANS points out that in the case of Reactor Fukushima Diiachi reactor 2, the RCIC ran for about 70 hours before failing.

Criteria sub paragraph however demands that ECCS componentry continue to function as follows:

“Long-term cooling. ….the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.

At the end of of 2011, the Prime Minister of Japan declared that the Fukushima Reactors were in “Cold Shut Down”. (the fuel temperature not having been measured actually – the location of much of the fuel remains unknown).

Under the Design Criteria for ECCS given above, the ECCS MUST HAVE a working life of MONTHS.

Yet the American Nuclear Society plainly state that at least one part of the ECCS has a designed life of a mere EIGHT HOURS.

The ANS in report clearly explain that other parts of the ECCS in each of the afflicted and failed reactors did not work in part or at all due to one factor or another. There are no excuses. Relicensing of reactors commenced in the USA only after nuclear authorities promised the public that in all cases the nuclear reactor industry WOULD KEEP ITS NUCLEAR SOURCES SEALED. They lied or were and are insufficiently skilled to keep the promise, a promise, I submit, made to be broken.

The declaration of a claimed successful Cold Shutdown by the Japanese government at the end of 2011 covers up the fact that no part of the ECCS of each reactor at Fukushima was able to do its mandated job for the months required. They all clagged out in March of that year.

And so the ECCS, even at the design stage, broke the rules, as opponents had pointed out decades prior, at the same time as Ergen wrote his reports, at the same time the nuclear authorities wrote the rules and at the same time as the US Congress approved the export of the reactors to Japan. And Japan spent the decades imposing strict censorhip upon those of its society who knew the promises of safety were flawed and dishonest.

The Nuclear Dispossession caused by the inevitable failure of the Fukushima Diiachi ECCS was foreseen in type as early as 1967.

Lessons Learnt? After being forgotten for the purposes of PR for four decades? Pull the other one.

One may claim that the design of the Fukushima nuclear reactors is old. And that modern reactors do not suffer the same rule breaking actual performance flaws.

However, despite the same old industry advertising of its products, how improved is, for example the current flagship of the Westinghouse reactor familty?

It is my understanding that the ECCS systems of the Westinghouse AP1000 have a designed life of FIFTEEN HOURS.

How well does 15 hours comply with the requirement of the ECCS to cool the core for as long as it takes: “Long-term cooling. ….the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core”.

It took about 70 for each of the three failed Fukushima Diiachi reactors to fail explosively. 15 hours is not enough.

The modern reactors therefore break the promise as did earlier generations of this failed and old fashioned technology.

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