NuScale Power, a company backed by Fluor Corp. (NYSE: FLR) working on a small modular reactor, announced this week that the company has developed the technology to achieve safe cooldown in the reactor core with no electrical power. According to NuScale, the technology does not require any on-going operator action nor additional water to achieve safe cooldown.
The events of Fukushima highlighted the importance that traditional reactors have of needing back-up sources of electricity to power the essential valves and pumps needed for long-term cooling to their nuclear power plants. The complete station black-out caused by the earthquake and subsequent tsunami eventually led to extensive damage to the Daiichi nuclear units because of their inability to power their safety systems. Their final lines of defense were banks of DC batteries with a limited life.
Dr. Jose Reyes, NuScale's Co-Founder and Chief Technology Officer, announced in Columbia, S.C. this week that, "Two years after the Fukushima event, NuScale is introducing a safety system for our nuclear reactor that does not require DC batteries to place the plant in a safe cool-down condition following an extreme event. This is a revolutionary solution to one of the biggest technical challenges for the current fleet of nuclear energy facilities. Because of our unique design, it allows the NuScale plant to achieve a 'Triple Crown' for nuclear plant safety--to safely shut down and self-cool, indefinitely, with no operator action, no AC or DC Power and no additional water." The patent pending breakthrough eliminates all of the DC batteries usually needed to align valves and to power systems needed to provide cooling of the nuclear core.
How it works: All commercial nuclear power plants currently use large banks of DC batteries as backup power for their Engineered Safety Feature Actuation Systems (ESFAS). Because these batteries serve a safety function, they are classified as a "1E system." One of the key functions of the ESFAS is to start the emergency core cooling system (ECCS). Because of the simplicity of the NuScale design, only a handful of safety valves need to be opened in the event of an accident to ensure actuation of the ECCS. These safety valves have been mechanically pre-set to align to their safe condition without the use of batteries following a loss of all station power. No AC or DC power is required for this valve alignment. Similarly, no pumps or additional water are required to provide an indefinite period of core cooling. The only safety related DC batteries that will be needed for a NuScale plant would be for the purpose of post-accident monitoring of system conditions. The complete 1E alternate power system concept, eliminating the need for safety grade DC power to accomplish ESFAS functions for shutdown and core cooling, was presented to the U.S. Nuclear Regulatory Commission at a meeting on December 4, 2012 and the non-provisional patent was filed in March 2013.
Reyes also noted, "This innovation required taking a look at the station blackout problem in reverse. Rather than requiring power to put the plant in a safe configuration following a station blackout, our engineers found it much simpler and safer to design the ECCS and supporting systems for failsafe operation. That is, the safety valves align in their safest configuration on loss of all plant power. This only works because of the few number of components involved and the fact that the safety systems themselves do not require electrical power to work."
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