The Debate Over Nuclear Reactor Venting


nuclear_reactors_carouselForum on Energy is kicking off a series of discussions on nuclear safety regulations, following the recent launch of the Japanese version of the site. Both the United States and Japan are responding to emerging nuclear safety concerns with enhanced regulation. Their shared goal is to design the safest possible energy systems without an overbearing regulatory system, and while maintaining affordable energy prices. This series aims to inform the ongoing discussion and public understanding of the issues confronting Japan’s Nuclear Regulation Authority (NRA) and America’s Nuclear Regulatory Commission (NRC).

In the wake of the March 2011 accident at Fukushima Daiichi, governments and regulatory bodies across the globe considered multiple ways to reinforce and better secure their fleets of nuclear reactors. One potential safeguard being considered by the United States is upgrading the venting system, however debates continue on whether this is a cost-efficient solution as part of the overall plans to improve safety.

The compendium below lays out some of the recent developments in this debate including:

  • News on perspectives and input from Congress about the proposed rule
  • Media coverage surrounding the debate
  • Industry response to the debate

 Congress Weighs in on the Proposed NRC Rule

Lobbying Flurry Precedes U.S. Vote on Fukushima Rules
“A proposed requirement that U.S. nuclear-power plants add $20 million devices to prevent radiation leaks, one of the costliest recommendations stemming from meltdowns in Japan two years ago, has attracted a flurry of last-minute lobbying.”

U.S. NRC Members Feel Heat From Congress Over Safety Mandate
“The NRC’s five members are expected to decide within weeks whether to require safety upgrades to the emergency venting systems at 31 U.S. reactors, some of which could be in danger of closing prematurely if the mandate goes forward. Members of Congress from Illinois, home to nuclear giant Exelon Corp. (EXC), and other states with nuclear power plants pushed the agency to make the rule cost-effective at a hearing held by the House Energy and Commerce Committee.”

5 Top Dems to NRC: Fukushima-style Reactors in U.S. Need Upgrades to Prevent Hydrogen Explosions and Radiation Exposure
“Five House Democrats who lead their respective committees today pressed the Nuclear Regulatory Commission (NRC) to require that all U.S. nuclear reactors of the same design as the ones that melted down at the Fukushima nuclear facility in Japan install vents to help prevent hydrogen explosions in the event of a severe accident and reduce exposure to radiation when they are used.”

Joe Barton, NRC’s Allison Macfarlane Lock Horns
“Nuclear Regulatory Commission Chairwoman Allison Macfarlane and Rep. Joe Barton had a tense exchange Thursday morning after he pressed her on the agency’s response to the 2011 nuclear disaster in Fukushima, Japan. It happened after the Texas Republican asked Macfarlane whether she would commit to having the agency conduct a ‘full regulatory review between the Japanese system and the U.S. system.’”

House Republicans Question Pace of NRC’s Post-Fukushima Safety Push
“House members today clashed over how quickly the Nuclear Regulatory Commission should impose new safety rules in reaction to the 2011 Japanese nuclear disaster, with Republicans calling on the agency to be more careful and some Democrats urging the commission to reject outside political influence. Republicans on two House Energy and Commerce subcommittees criticized the NRC for not fully comparing Japanese and American regulatory structures before imposing new safety changes after the March 11, 2011, earthquake and tsunami.”

The Debate Over Vents

Post-Fukushima, Arguments for Nuclear Safety Bog Down
“Alarms sounded and lights flashed as control panel dials at a nuclear power plant in upstate New York warned that the power for safety equipment was failing. The room went dark until the emergency lights kicked in. But there was no reason to worry on this frozen winter morning. This was a simulation by Constellation Energy, the owner of the Nine Mile Point plant on Lake Ontario, for the benefit of two of the five members of the Nuclear Regulatory Commission. It was part of an intense lobbying campaign against a proposed rule that would require utilities to spend millions of dollars on safety equipment that could reduce the effects of an accident like the Fukushima Daiichi meltdown in Japan two years ago. Ever since the nuclear accident in Japan released radiation into the atmosphere, regulators in the United States have been studying whether to require filters, costing as much as $45 million, on the vents of each of the country’s 31 boiling water reactors.”

After Fukushima, Tasks Remain for the American Nuclear Industry
“In response to the nuclear accident at Fukushima, the NRC ordered installation of ‘reliable hardened vents’ on older G.E.-designed boiling water reactors. Of 31 reactors, 23 already have ‘hardened vents’ and eight have no vents at all; even reactors with vents will need work on the valves to assure they are operable without electricity, which was a problem at Fukushima. The NRC is considering an order to add filters to the end of the hardened vents, outside the containment, which would trap more than 99 percent of the radioactive particles if the vent had to be used.”

The Nuclear Industry and Venting, Round 2
“The debate over making post-Fukushima Daiichi improvements to American reactors is getting down into the details, and one focus is pressure relief vents. The idea behind venting a nuclear plant is that if a reactor overheats, chemical reactions will produce steam and gases that could overpressurize the containment building. The containment is a major line of defense against the release of radioactive materials, and rather than let it burst like an overfilled balloon, the idea goes, it would be more sensible to let the reactor dump a little bit of slightly radioactive gas into the environment.”

U.S. nuclear plants similar to Fukushima spark concerns
“As the United States prepares to build its first new nuclear power reactors in three decades, concerns about an early generation of plants have resurfaced since last year’s disaster in Japan.

The Vermont Yankee nuclear power plant — the subject of a battle between state authorities and the Nuclear Regulatory Commission over its continued operation — uses one of 23 U.S. reactors built with a General Electric-designed containment housing known as the Mark I. It’s the same design that was used at Japan’s Fukushima Daiichi nuclear power plant, where three reactors melted down after the station was struck by the tsunami that followed Japan’s historic earthquake in March 2011.”

Japan Atomic Safety Rules May Keep Reactors Closed for Years
“Japan’s Nuclear Regulation Authority approved safety standards for atomic power plants that may require years of reinforcement work for some reactors idled after the Fukushima disaster. Nuclear power plants will need to build secondary control centers at least 100 meters from reactor buildings to manage emergency cooling systems and radiation filter vents, according to the rules. They also stipulate tougher tsunami defenses.” 

Industry Response

Vents and Filtering Strategies Come to Forefront in Fukushima Response
“In recent months, experts from the nuclear industry and the NRC have turned their attention to two less obvious aspects of plant operations: vents and filters. The importance of venting became clear during the early days of the Fukushima Daiichi accident last year. If containment vents at the Japanese facility had been opened in a timely manner, the worst consequences of the accident might have been avoided.”

NRC: Consideration of Additional Requirements for Containment Venting Systems for Boiling Water Reactors with Mark I and Mark II Containments
“The staff conducted sensitivity studies to evaluate the implications of possible changes to assumptions used in the cost-benefit analysis and major uncertainties in factors, such as event frequencies and consequences. The best-estimate quantitative evaluations, excluding any qualitative factors and sensitivity analysis, indicate that the costs of the proposed actions outweigh the benefits.”

GE Reports: Venting Systems in Mark I Reactors
“Recent news reports have focused on how the emergency venting system at the Fukushima Daiichi nuclear plant in Japan responded to the massive earthquake and tsunami in March. The reports also pose questions about the performance of U.S. plants with a similar venting system. Here is an update from GE on these two issues.”

Westinghouse: Passive Hardened Vents for BWRs
Westinghouse recommends a design philosophy that:

  • Entails fail-safe containment pressure relief with no operator action or power supplies (AC or DC) required
  • Is capable of venting both wetwell and drywell pathways, with priority given to wetwell venting
  • Uses the vent at low containment pressure to aid in the ability of reactor core isolation cooling to operate for a longer time
  • Dedicates vent piping to the venting function, with no shared safety functions

NRDC: Post-Fukushima Hardened Vents with High-Capacity Filters for BWR Mark Is and Mark IIs
Given the vulnerabilities of BWR Mark I and Mark II primary containments—their relatively small volumes and dependence on suppression pools, which do not mitigate hydrogen—it is essential that a hardened containment vent be designed so that it would be reliable in a wide range of different severe accident scenarios. If such a vent cannot be developed, the NRC should perhaps consider either shutting down or not relicensing BWR Mark I and Mark IIs.