The nuclear power industry has met a deadline to order a variety of backup, readily-deployable safety equipment to handle “extreme events,” such as the tsunami-generated Fukushima nuclear disaster in Japan, according to the Nuclear Energy Institute.
Orders for the first tranche of portable equipment, comprising 300 pieces including injection pumps, air compressors, small generators for recharging batteries, and larger generators, were due to be placed by the end of March, for delivery into 2013.
A second order will follow later in 2012, after site calculations are completed, and the NRC requirements are clearer.
One of the new NRC orders will require NRC licensees to implement “mitigating strategies” for accidents that exceed the worst case accident scenarios considered at the time the plants were built.
Such “beyond design basis” events include the “station blackout” situation—the loss of all power at the plant, including that provided by emergency on-site generators—that faced the operators at Fukushima in the wake of the tsunami.
It took 10 years for the agency to fully implement security upgrades made necessary by the 9/11 terrorist attacks, and it will take at least five years to institute changes in response to Fukushima.
- Dave Lochbaum – The Union of Concerned Scientists
The FLEX program is to assume a loss of AC power, which drives standard reactor safety equipment, and a loss of ultimate heat sink, which is the essential removal of decay heat. FLEX aims to provide additional layers of protection in these circumstances.
FLEX is set to form part of the industry’s legally-binding response to the US regulator’s post-Fukushima orders to be able to mitigate beyond-design-basis accidents.
In a press conference, Charles Pardee, Exelon chief operating officer and chairman of the US industry Fukushima response steering group, said that it is still trying to come up with a way to provide cooling to the reactor core, spent fuel pond, to remove decay heat, and maintain the integrity of containment to contain fission product releases.
Simple observations of Fukushima reveal
A beyond design basis external event can disable multiple units and significantly complicate recovery efforts and increase the risk of severe accident escalation at other on-site units.
An extended loss of power event can quickly lead to core damage.
Specific Actions Taken at U.S. Reactors
More than 300 major pieces of equipment acquired or ordered
- 66 large portable generators
- 62 diesel-driven pumps
- 59 small load diesel generators
- 13 fire trucks
- 11 portable ventilation units
FLEX and Spent Fuel Pools
- Provide water for spent fuel pool injection during station blackout
- In conjunction with pool level information now in control rooms, enhanced spent fuel pool level instruments will signal when FLEX components should provide water injection if installed systems not operable.
- FLEX equipment will include portable level instruments and portable power supplies.
SFP Instrumentation Order
- Two independent channels of water level instruments: one installed/one portable or both installed.
- 3 level indication points: normal pool cooling; rad protection; fuel minimally covered (top of rack)
- Accessibility for installing portable and readout
- Missile protection provided by existing structures
- Non-safety-related, but with augmented quality requirements that can ensure reliability similar to fire protection.
- Installed channel(s) mounts seismically qualified consistent with the existing plant seismic class 1E.
- Environmental qualifications on both channels consistent with expected conditions of operation (e.g., temperature, humidity and radiation associated with the SFP evaporation/boiling.) (Reg. Guide 1.97 does not apply)
- Power supplies: Each channel powered by separate source; provide for back-up sources independent from plant systems
- Display: accessible location (Control Room or Aux Shutdown Panel not required) and available when needed.
- Trained personnel (not limited to operators).
- Industry guidance to NRC by May 30, 2012
- NRC Interim Staff Guidance issued by August 31, 2012
- The licensees submit plans to the NRC no later than 6 months following issuance of the ISG
- Full implementation to be completed no later than two refueling cycles after the issuance of the ISG or December 31, 2016, whichever comes first.
- Several public meetings to work on guidance.