Filtered Vents and Boiling Water Reactors: It’s Not About the Costs

Recently, we've seen a spate of media reports that have accused the nuclear industry of opposing the installation of filtered vents on Mark I and II boiling water reactors (BWRs) simply because of cost considerations.

Needless to say, a number of us here at NEI are troubled by that accusation given the extensive research industry has produced buttressing our position that demanding that filtered vents be installed on every Mark I and II BWR is a "one-size fits all" solution.

Instead, the industry advocates what we call a "performance-based" approach where each of the 31 BWRs in the U.S. would make an individual determination of what course constitutes the best way forward -- an approach that would neither rule out nor mandate the installation of filtered vents.

To shed some additional light on this alternate way forward, Jason Zorn, NEI's assistant general counsel and Steven Kraft, NEI's senior technical advisor, have co-authored an article called, "Filtered Vents and Boiling Water Reactors: It’s Not About the Costs." We've posted the article in full at our Safety First microsite, but here is the relevant excerpt:

Is there a better solution? Yes.

One approach marries the need to cool the uranium fuel debris by injecting water into the containment building with filtering radioactive material from the vent gases with that water.

A September 2012 report by the Electric Power Research Institute (EPRI) evaluated several potential radiation filtering strategies and assessed their abilities to avoid radiation releases. The report emphasized the need to cool the fuel debris during a severe accident. Otherwise, the melted fuel will rupture containment and releasing radioactive materials into the environment bypassing the vent and any filter that might be installed.

Ensuring core cooling this way has the added benefit of “filtering” radioactive material inside the containment building. The water in containment would work the same way that it would in an external filter. Thus, keeping damaged fuel cool through the injection of water, with its inherent filtering capability, challenges the basis for compelling external filters at 31 reactors.

Details on filtering options. Click to enlarge.

This is not a new concept. In the late 1980s, when the NRC wanted the BWR Mark I plants to add containment vents to prevent over-pressurization during an accident, the vents were piped through the internal suppression pools (water already in containment as part of the existing design to cool and reduce the pressure of the containment atmosphere during accidents). NRC staff reviews dating back to 1993 stated that an “external filter would not significantly increase the removal of radioactive material….”

In light of the significant body of research on this issue, the industry has recommended that the NRC consider less-prescriptive filtering strategies. Consistent with the EPRI research, filtering strategies focus primarily on providing additional ways to get water to the fuel during a severe accident and to control pressure in containment. Rather than a prescriptive solution like external filters that has limited benefit and may not provide for additional water to cool the core, the industry envisions that each company would assess the issue on a site-by-site basis and develop an approach that best suits each site.

As pointed out numerous times industry testimony and letters to the NRC, 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.

Even the NRC’s Advisory Committee on Reactor Safeguards -- an independent body that reviews NRC staff activities and provides independent recommendations to the Commission – supports the proposal to look at performance-based solutions at each reactor.

In 2012, NEI published this infographic with details on exactly how these filtering strategies can work. Click here to read it right now.