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Minimizing the Risk of Hydrogen Explosion from a Reactor Meltdown at Indian Point: Entergy and NRC Counter Substantive Citizen Safety Petition with Spin

Christopher Paine

Posted November 28, 2012

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Citing the risk that hydrogen produced in a severe nuclear accident could accumulate and explode with sufficient force to breach Indian Point’s Unit 2 and 3 containment buildings and expose the public to a large radiological release, the New York clean water advocacy group Riverkeeper recently filed a 10 C.F.R. § 2.206 enforcement action petition urging that the Nuclear Regulatory Commission (NRC) permanently shut down these reactors.

If a meltdown were to occur at either of Indian Point’s two reactors, a large quantity of potentially explosive hydrogen would be produced when reactor core materials, principally the zirconium alloy tubes that contain the nuclear fuel, chemically react with steam produced by overheating of the core.  There is no assurance today that Indian Point’s owner, Entergy, could control the total quantity of hydrogen generated in a meltdown and prevent a hydrogen detonation that would breach the containment and spew radioactive contamination into the regional environment.  

Despite the devastating occurrence of such hydrogen explosions at Fukushima, both Entergy and the NRC refuse to acknowledge this continuing vulnerability in Indian Point’s defenses against a severe accident, and instead they offer the public false assurances that its reactors are properly equipped to minimize this risk. The author of the Riverkeeper petition, Mark Leyse, is also a technical consultant to NRDC’s Nuclear Program, and together we have prepared a detailed and copiously referenced refutation of this Entergy-NRC effort at spin control.  

According to the Nov. 15 Poughkeepsie Journal, Entergy spokesman Jerry Nappi “disagreed with the petition’s premise,” and then stated, “Indian Point is designed with back-up safety equipment to protect the plant, including equipment inside containment that automatically turns hydrogen gas into harmless water in the unlikely event of damage to the nuclear fuel.”  Nappi was clearly referring to the hydrogen “recombiners” that the plant has in each of its containments.  These safety devices spontaneously recombine hydrogen and oxygen molecules, yielding steam and heat, when the local hydrogen concentration in the air exceeds about 1 percent by volume. Indian Point Unit 2’s containment has “passive” (i.e., self-actuating or “autocatalytic”) recombiners (“PARs”), which do not require electricity, and Indian Point Unit 3’s containment has electrically-powered units.     

Hydrogen recombiners are intended to maintain the hydrogen concentration in the containment below levels that can support a hydrogen explosion (i.e., at about 4 % by volume and above).  But contrary to Entergy’s assurance of safety, there are only two recombiners in each of Indian Point’s containments, and they have a very limited capacity. In fact, the NRC has itself stated that this capability would be “ineffective at mitigating hydrogen releases from risk-significant beyond design-basis accidents”—i.e., partial or complete core melts.  In European countries that seek to minimize the hydrogen explosion risk from these types of accidents, a fleet of typically 40 units are installed inside a light water reactor (LWR) containment. So it appears that Indian Point has only 5 percent of what European nuclear regulators regard as a prudent complement of hydrogen recombiners. 

To make matters worse, the two Passive Autocatalytic Recombiners (PARs) in Unit 2 could actually compound the consequences of a severe accident. This is because PARs can produce unintended ignitions when exposed to elevated hydrogen concentrations. In April 2012, NRDC petitioned the NRC for a safety enforcement action at Indian Point that would either: remove the unintended ignition hazard represented by the token PARs at Unit 2; or, if Entergy continues to assert this small capability is useful for hydrogen control in a less severe design basis accident, replace them with electrically-powered thermal recombiners that can be switched off in a severe accident, like those in Unit 3.

The NRC, on the other hand, responded to Riverkeeper’s petition by highlighting a different, but equally illusory safety capability at Indian Point. According to the Poughkeepsie Journal article, “NRC spokesman Neil Sheehan said plant operators could use controlled burns…to manage a significant buildup of hydrogen inside a [containment] dome.”  This is a reference to hydrogen “igniters,” which are safety devices designed to implement controlled burns in a meltdown scenario to help control a significant buildup of hydrogen inside certain types of reactor containments. Unfortunately for the NRC spokesman, Indian Point has two large dry containments—a design that does not have hydrogen igniters.  Hence, plant operators would not be able to implement controlled burns to manage a significant buildup of hydrogen inside of Indian Point’s containments.  It is disturbing that a spokesman for the NRC would respond to a media inquiry about a nuclear safety concern at Indian Point by pointing to a safety capability that does not exist at the plant.

To date, the Nuclear Regulatory Commission has not required owners of pressurized water reactors with large dry containments to control the hydrogen that would be generated in a meltdown. A July 2011 NRC task force report on insights from the Fukushima Dai-ichi accident claims that the pressure spike of potential hydrogen explosions would remain within the design pressure of large dry containments. However, according to the NRC’s own safety analyses, conducted a decade ago, hydrogen explosions inside large dry containments could cause pressure spikes exceeding 110 pounds per square inch, which is about twice the design pressure of Indian Point’s containments.

Indian Point is located in Buchanan, New York on the Hudson River, 34 miles north of Central Park. According to a recent NRDC report, if winds were blowing south, a release of radiation from Indian Point on the scale of the Fukushima Dai-ichi accident could contaminate a swath of land between Buchanan and the George Washington Bridge, rendering it uninhabitable for generations. An accident releasing radiation on the scale of the Chernobyl accident could render Manhattan uninhabitable.

In sum, the two PWRs at Entergy’s Indian Point Energy Center remain poorly equipped to minimize the risks of explosive hydrogen that would be produced in a severe nuclear accident involving one or both of these units. If past is prologue, it seems likely the NRC will respond that this safety enforcement issue is not unique to Indian Point, and therefore constitutes a “generic issue” that must be pursued in a separate “rulemaking” proceeding, one that may take many years to reach fruition, or indeed may never be taken up by the Commission. 

However, there is an alternative path to force consideration of this important safety issue. Both Indian Point units are currently involved in a hotly contested relicensing proceeding, in which both the State of New York and various citizen interveners are opposing a 20-year license extension, on the grounds that continued operation of these 40 year old and technologically obsolescent units presents an unacceptable hazard to the 17.6 million people who live within a 50 mile radius of the plant.  NRDC shares this fundamental risk perspective on Indian Point, and opposes continued operation of the reactors beyond their current license terms. Nonetheless, if these units are not slated for retirement when their current operating licenses expire, in September 2013 (Unit 2) and December 2015 (Unit 3), then major new capital investments for environmental protection will be required, not only to reduce coolant-intake fish kills and harmful thermal discharges to the Hudson River, but also to drastically upgrade the plant’s defenses against severe accidents. 

Responsible regulatory authorities have the duty to ensure that all these essential new investments are made part of Entergy’s forward-looking calculus of whether it makes economic sense to continue operating Indian Point for another 20 years. Judging by their initial fumbled response to the Riverkeeper petition, Entergy continues to count on a pliable federal regulator to discount the true economic cost risk of a severe accident at Indian Point, while the NRC appears reluctant to step-up and perform its essential regulatory function, which is vital not only to preserving public health and safety, but also to the rational allocation of resources for energy investment in New York State. Concerned citizens must continue to demand that both these organizations perform in a more responsive and responsible manner when the safety and economic well-being of the greater New York City area is at issue.

For an in-depth discussion of the severe accident hydrogen explosion risk at Indian Point, please follow this link to the full report.

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