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 or 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 blackout 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, said the technology eliminates all of the DC batteries usually needed to align valves and to power systems needed to provide cooling of the nuclear core.
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 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 (NRC) at a meeting on December 4, 2012 and the non-provisional patent was filed in March 2013.