Tuesday, April 2, 2013

US NRC Will Delay Filtered Vent Plan and Study Options, Final Rulemaking by March 2017

Let's kick the can...

It looks the cost-benefit ("performance-based") analysis argument by the Congressional Republicans in the House Energy and Commerce Committee won.

To recap the Committee's letter to the NRC chairwoman:

"With respect to these [safety] enhancements, we have particular concern about the potential requirement to install "filtered vents" for certain boiling water reactors which we understand to be significant, capital-intensive structures. As instructed by the Commission, the NRC staff has proposed four potential options but urged the Commission to choose "Option 3." Under this option, the Commission would issue an order requiring the installation of fintered vents rather than pursuing a performance-based process."

Now, the Nuclear Regulatory Commission will "study options" and won't make the final rule till March 2017. The Commission's thinking as you can read in the article below take the House Energy and Commerce Committee's thinking extremely seriously.

From Power News (3/21/2013; links are in the original, emphasis is mine):

NRC Delays Action on Vent Plan, Directs Staff to Study Options

The Nuclear Regulatory Commission (NRC) on Tuesday delayed approving a recommendation made by technical staff that calls for upgrades or replacements of "hardened" venting systems at the nation's 31 Mark I and Mark II boiling water reactors (BWRs), giving staff a year instead to assess other options and produce a "technical evaluation" on the proposal.

The NRC commissioners directed staff to follow a two-track approach for further improvements to systems for safely venting pressure during potential accidents at the reactors, in response to the Fukushima accident in March 2011. It gave the staff 60 days to finalize a March 2012 order, which will require vents to handle elevated pressures, temperatures, and radiation from a damaged reactor. The order will also ensure plant personnel can operate vents safely under these accident conditions.

It also gave the staff a year to produce a technical evaluation to support rulemaking on filtering, gathering more public input as it completes its analysis. Directing the staff to consider both the use of a filter to be placed on the vent, as well as a more performance-based approach using existing systems to achieve a similar reduction in radioactive release during an accident, the commission said the draft rule and final rule must be ready by March 2017.

A vent generally refers to a pipe connected to the primary containment of a nuclear power plant and leading to the plant’s exhaust stack. It is designed to allow gases inside the containment to be removed. “The major problem at Fukushima was getting the containment vents open,” said Doug True, president of ERIN Engineering and Research told Nuclear Insight last fall. “Significant delays in the decision to open the vents, combined with the Japanese decision-making process and difficulties in opening the vent valves, delayed the venting action, which in turn led to hydrogen explosions.”

The NRC's decision was widely viewed as a victory for the nuclear industry. The NRC has estimated that filtered vents could cost up to $15 million, but other estimates put costs of equipment at $30 million or more.

But media reports accusing the nuclear energy industry of opposing the installation of filtered vents on Mark I and II BWRs are incorrect, say Jason Zorn, assistant general counsel, and Steven Kraft, senior technical advisor at the Nuclear Energy Institute (NEI ). The issue is a technical one. "In the extremely unlikely event that an accident progresses to the point of the fuel melting through the reactor vessel onto the containment floor, it is imperative that water be injected into containment to cool the fuel debris on the floor," they say. "If not, radiation releases will occur from numerous locations in the containment building and bypass the vent. If the vent is bypassed, it doesn’t help if there is a filter on the vent, because it, too, will be bypassed."

Filtering strategies based on the individual plant evaluations could result in the installation of a vent filter, "if that’s what makes sense for a given plant," they said.

Sources: POWERnews, NRC, Nuclear Insight, NEI

“Significant delays in the decision to open the vents, combined with the Japanese decision-making process and difficulties in opening the vent valves, delayed the venting action, which in turn led to hydrogen explosions"?

The vents couldn't be opened for a long time because there was no power. There are experts and engineers who have proposed that instead of delay in venting leading to hydrogen explosion, venting may actually have caused hydrogen explosions in Reactors 1 and 3 because of the peculiar structure of the exhausts stacks and power loss. Instead of leaving via the exhaust stack, vented hydrogen gas came back inside the reactor building, they say.

Water under the bridge at this point, except that inaccurate understanding of the Fukushima I Nuclear Power Plant accident is being used as excuse.

"Performance-based" cost saving instead of "Defense in Depth", without properly defining "cost".


Defense in depth, in NRC's own words:

An approach to designing and operating nuclear facilities that prevents and mitigates accidents that release radiation or hazardous materials. The key is creating multiple independent and redundant layers of defense to compensate for potential human and mechanical failures so that no single layer, no matter how robust, is exclusively relied upon. Defense-in-depth includes the use of access controls, physical barriers, redundant and diverse key safety functions, and emergency response measures. For further information, see Speech No. S-04-009 (PDF), "The Very Best-Laid Plans (the NRC's Defense-in Depth Philosophy)."

I thought venting is an emergency response measure...


Anonymous said...

J. Zorn's explanation doesn't really make sense: to be able to easily inject water in the case of a very severe core melt in order to avoid melt-through, you need a means to safely decrease the inner pressure by removing the accumulated hydrogen.
For all practical purposes, this means venting through a filtered system, so that exposure of the operators and emergency crew is low. One can see the impediment the on-site radioactivity was in Fukushima after the explosions and the unfiltered venting! Filters also come with rupture disks, avoiding overpressure and thus uncontrolled releases on the confinement even if you are not able to activate the venting valves for some reason.
So filters are great for accident management. Of course, they're also great for the surrounding land…

Anonymous said...

OT: Kansai Electric will buy 800,000 tons of LNG yearly from the US for 20 yrs via Sumitomo Corp. (Jiji news Apr 1st 19:17).
Why is Kepco paying a commission to Sumitomo on this purchase? Can't Kepco buy gas directly? Isn'it enough that Japan is paying LNG twice the price piad in Europe?
If Toyota can think of producing and supplying electricity (Jiji news Apr 2nd 13:45) bypassing Chubu Electric why can't Kepco bypass Sumitomo?


Anonymous said...

15 million for a filtered vent seems cheap when compared to 5,000 million for a new plant or 250,000 million in damages in case of a severe accident.


Anonymous said...

2017? That soon, eh?

Anonymous said...

For a better understanding of the pros and cons of filtered vents, I suggest reading Sherrell Greene's excellent post on the subject.


Sherrell Greene was a member of the BWR Severe Accident Analysis group at Oak Ridge and a list of his publications can be found here.


Anonymous said...

@Anon 3:53PM. The main argument made by Sherrell Greene against filters is that once activated, they cannot be closed. This is mixing thing up, and concerns the rupture disk, NOT the filter.
Modern European designs will have valves in parallel with the rupture disk:
1) You CAN vent and close the filtered vent manually, with the valves, as long as you have control of the plant.
2) Uncontrolled venting via the rupture disk will only happen if pressure rises to a point where containment integrity is threatened, i.e. if somehow the operators completely lose control of the plant and cannot operate the valves. Note this is an extreme case, because the valves are designed to be manually operated from special shielded spots.
The philosophy is that passive venting will always be better than having the containment fail in an unpredictable way (see Fuku I-1, apparently H2 in the building…).

In any case, be it active (valves) or passive venting (rupture disk), you're obviously better off with a filter! The whole thing is basically a no-brainer, as all this evaluation and the detailed design stuff (valve + rupture disk layout, explosion shields, radionucleide absorption, thermal requirements, etc.), was carried out in Europe 20-30 years ago…

Anonymous said...

Exactly, at Fukushima they did not have "not to vent" as a choice.
However, even better than filters, you are better off with a non-nuclear powerplant; anything that does not require a caveat like "as long as you have control of the plant".

Anonymous said...

"as long as you have control of the plant"


Anonymous said...

@Above: "better off with a non-nuclear powerplant"?
Maybe not:
"Prevented mortality and greenhouse gas emissions from historical and projected nuclear power"
Pushker A. Kharecha and James E Hansen
Environ. Sci. Technol., 2013
"Using historical production data, we calculate that global nuclear power has prevented about 1.84 million air pollution-related deaths and 64 gigatonnes (Gt) CO2-equivalent greenhouse gas (GHG) emissions that would have resulted from fossil fuel burning."
"…nuclear power could prevent an additional 420,000 to 7.04 million deaths and 80 to 240 GtCO2-eq emissions due to fossil fuels, depending on which fuel it replaces."

Anonymous said...

@5:07 Nuclear energy is less than 5% of the total energy usage so I guess the police should chase the management of the oil/coal industry for killing 1.84 * 100 / 5 = 56.6 million people.
Also, are the researchers sure that among those 1.84 million people there was not a single smoker? Smokers are not accounted among the Chrernobyl victims so they can't be counted as fossil electricity generation victims either. Same goes for people living in large cities where air pollution is caused by cars. Same goes for people living in Hawaii, where air quality is affected by volcanic gas emissions.

Atomfritz said...

These 15-30 millions needed for the filters equal the profits made by no more than 2 to 4 weeks of reactor operation...

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