NuScale, a leader in the increasingly competitive field of advanced nuclear reactor design, has announced that the U.S. Nuclear Regulatory Commission (NRC) reviewers issued a document that formally agrees that their design does not require any electrical power to achieve safe shutdown.
It’s difficult to explain the importance of that regulatory position. People with experience in the costly hurdles associated with designing, procuring and maintaining Class 1E electrical power systems have a better chance of understanding.
Borrowing an overused, but appropriate descriptor, this step in the licensing process for NuScale is “yuuuge.”
It means that if a NuScale power station had been sitting on the coast of Japan and was inundated with a 15 meter high tsunami, it would not have mattered where its emergency diesel generators were installed. It would not have mattered that emergency connections for backup generators were also underwater or that the batteries were flooded.
If a NuScale power station was on the coast of Massachusetts and one or both of its grid connections failed, it wouldn’t have required a shutdown. The plant could have kept operating at low power in an island mode, ready to return to full power as soon as the grid connection had been repaired.
It means that NuScale power stations do not need to have a building full of storage batteries on site and in a seismically safe building. It means that the plant owners will not have to go through contortions to ensure that the Class 1E systems are always available with suitable redundancy even during repair periods.
The plants will still operationally benefit from reliable electrical power. There will still be codes and standards that apply to the electrical power systems to ensure conventional safety and uninterrupted ability to function and produce a valuable product. There is, however, a major cost differential between identical parts that carry a Class 1E classification with its associated pedigree and those that do not.
The specific action that the NRC took was that it issued a Safety Evaluation Report (SER) that concurred with NuScale’s Licensing Topical Report titled “Safety Classification of Passive Nuclear Power Plant Electrical Systems.”
That document describes NuScale’s approach and analysis ensuring that their reactors will be safe without reliance on any safety-related electrical power.
The NRC’s approval of a safety classification topical report that does not contain any Class 1E electrical systems is limited to the NuScale design.
The decision, however, establishes that the NRC is open to well-justified design choices that follow a path that deviates from the traditional prescriptive assumptions.
The NRC’s review of NuScale’s Design Certification Application remains on track to be completed by September 2020.
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