BRATTLEBORO, Vt. -- In response to the nuclear disaster at Fukushima, Japan, the U.S. Nuclear Regulatory Commission has ordered the owners of certain types of commercial nuclear reactors, including Vermont Yankee, to make improvements to their emergency venting systems.
In an order issued late last week, the NRC instructed the owners of GE Mark I and Mark II Boiling Water Reactors that they have until 2019 to make the necessary improvements, but should begin the work "promptly."
Vermont Yankee nuclear power plant in Vernon is a GE Mark I Boiling Water Reactor.
"Safety is always job one and we are using the lessons learned from Fukushima to further strengthen our operations," said Jim Sinclair, spokesman for Yankee, which is owned and operated by Entergy.
In its order, the NRC noted that the events at the Fukushima Dai-ichi nuclear power plant following the March 2011 earthquake and tsunami exposed weaknesses in boiling water reactors, and that "rare natural phenomena" could overwhelm traditional built-in safety systems. The disaster at Fukushima resulted in a release of radioactive materials, which forced an evacuation of the area surrounding the plant.
"[T]he operators were unable to successfully operate the containment venting system," noted the NRC. "These problems, with venting the containments under the challenging conditions following the tsunami, contributed to the progression of the accident from inadequate cooling of the core leading to core damage, to compromising containment functions from overpressure and over-temperature conditions, and to the hydrogen explosions that destroyed the reactor buildings (secondary containments) of three of the Fukushima Dai-ichi units."
"The NRC staff performed a detailed regulatory analysis of possible improvements to Mark I and Mark II reliable hardened containment vents, including the option of installing severe accident capable vents," stated Neil Sheehan, spokesman for the NRC, in an email to the Brattleboro Reformer.
The order requires the vents be modified to handle the pressures, temperatures, hydrogen concentrations and radiation levels from a damaged reactor. The enhancements also ensure plant personnel can operate the vents safely if the reactor core is damaged.
However, the NRC is not at this time requiring plant operators to install filtration systems. NRC staff has been ordered to develop a rule for the 31 plants affected by the order "to implement strategies to enhance filtering of radioactive material from any vented gases, as well as improve procedures for preserving containment integrity."
The staff expects to hold public meetings later this month to discuss both the technical basis for the rule and the preparation of guidance for complying with the order.