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NRC Proposes Orders to Enhance Protection Against Beyond-Design-Basis Events

The following story originally appeared in NEI’s Nuclear Energy Overview.

The Nuclear Regulatory Commission is reviewing three proposed orders and three requests for additional information on post-Fukushima actions to enhance nuclear plant operators’ emergency response actions to protect against beyond-design-basis external events.

While reaffirming its conclusion that reactor operations and licensing pose no “imminent threat” to safety, the NRC staff said the accident in Japan highlighted the need for reliable containment vents for some nuclear energy facilities, better instrumentation for used fuel pool monitoring, and strategies for mitigating damage from external events that may affect multiple reactors simultaneously.

“Now that we have the orders and requests for information in hand, we will work with the NRC to reach a common understanding on the implementation guidance that is being developed,” said Tony Pietrangelo, NEI’s senior vice president and chief nuclear officer. “We have been generally aligned with the NRC thus far on near-term priority actions.”

He added that the industry’s strategy is to take actions that will enhance safety as quickly as possible using a diverse and flexible coping capability—the FLEX approach—to address extreme natural events that could cause loss of power or cooling capability.

One draft NRC order will require nuclear energy facilities to establish a “mitigation strategy for beyond-design-basis external events.” The industry intends to develop a three-phase approach. The first phase involves the use of installed equipment and resources to maintain or restore reactor cooling, maintain containment integrity, and used fuel cooling capability. Subsequent phases will use pre-staged on-site and off-site resources.

In its Feb. 17 report to the commission, the staff said elements of FLEX “may satisfy the requirements of the order to mitigate challenges to key safety functions resulting from beyond-design-basis natural phenomena hazards. … The staff’s regulatory conclusions on the acceptability of FLEX will be based on licensee responses to this order.”

A second order will require “reliable hardened containment vents” for boiling water reactors with Mark I and Mark II containments. The extended loss of power at Fukushima Daiichi prevented operators from opening the vents from the control room to assist in maintaining cooling and relieving pressure, the staff said. The delay in venting the containment ultimately led to hydrogen explosions and the release of radioactive material to the environment.

The NRC order would require companies with boiling water reactors to assess and if necessary enhance hardened venting systems at facilities with Mark I containments to improve valve access and reliability. In addition, this order will require facilities with Mark II containments to install reliable and hardened vents for containment. The schedule calls for companies to submit their integrated implementation plans to the NRC by next February. The staff will address the potential need for filters in the vents in a paper to be submitted to the commission in July.

The third order requires operators to install instruments to remotely monitor water levels and temperatures in used fuel storage pools. The lack of information about the condition of the pools at Fukushima caused the control room operators to have concerns about the status of the fuel pool during the event.

“Fukushima demonstrated the confusion and misapplication of resources that can result from beyond-design-basis external events when adequate instrumentation is not available,” the draft order states. It concludes that reliable remote used pool instrumentation should be required for the “adequate protection of public health and safety.”

The agency also issued a draft letter requesting information from reactor operators on seismic and flooding re-evaluations, seismic and flooding inspections, communications equipment, and emergency response staffing for events affecting multiple reactors at a site.

The orders and information requests will go to all operating power reactor facilities as well as the holders of construction permits under the NRC’s original licensing process (that is, Tennessee Valley Authority’s Watts Bar and Bellefonte projects) and combined construction and operating licenses issued under the new licensing rule.

For design certifications and licenses under active review, the staff said it will ensure that post-Fukushima actions approved by the commission are addressed prior to certification or licensing. “[Any] applicable … Fukushima actions not already addressed as part of the licensing process will be addressed in the same manner as operating reactor licensees,” the staff said. The staff added that some post-Fukushima actions are not applicable to the new Vogtle and V.C. Summer reactor projects because they are based on the Westinghouse AP1000 reactor design, which has additional safety features not reflected in existing reactors.

While orders typically do not require commission approval, the commission has told the staff it will vote on any orders that would lead to a change in the design basis for nuclear energy facilities. Once issued, the orders will be effective immediately. Implementation is required by Dec. 31, 2016.

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