SMR-160, developed by Holtec International (USA), is a small modular reactor designed to produce 160 megawatts of electricity using low enriched uranium fuel. SMR-160 is intended to serve as a distributed energy source that dispenses with the need for expensive high capacity transmission lines over long distances, making the electric grid more resistant to natural disasters or acts of sabotage.
The essential differentiator of the SMR-160 design is its absolute safety, essential to garnering public support and regulatory approval for diversified applications and distributed generation. The key safety concern for any nuclear reactor is radioactivity release, which could occur only if the reactor overheats due to a severe human performance error or equipment failure. Today’s plants have many safety features to prevent this from occurring, primarily by cooling water that is pumped to the reactor cooling system from nearby sources. Unlike today’s operating plants, the SMR-160 is designed such that all the cooling water needed for safe shutdown of the plant from even the most severe accident scenarios is part of the plant and in the location it is needed to prevent the reactor from overheating. The safety systems that access the SMR-160 cooling water reserve are passive, meaning they operate under the force of gravity to enable cooling of the heat generated from the reactor operations. Hence, in SMR-160 safety is passive and intrinsic to the design.
Due to its absolute safety and small size (less than 4.5 acres of land for a single unit and 6 acres for a two-unit site), SMR-160 can be placed close to cities and towns, reducing transmission losses and enabling the plant’s workers to live in the local community. True to its name, SMR-160 is truly modular: each reactor unit is entirely autonomous of others at a multi-unit site.
SMR-160 has completed the Vendor Design Review (VDR) Phase 1 process in Canada and the licensing process is underway with the USNRC in the United States. Holtec has received DOE Funding for development of a test program to benchmark the analysis codes against a physical mockup of the SMR-160 in support of the licensing process.
SMR-160 is designed to be cost-competitive with other sources of energy, utilizing Holtec’s experience as a nuclear manufacturer, constructor, and site service provider gained over our 30 years of project delivery.
Informed by over six decades of lessons learned from reactor operations, SMR-160 is designed to be an unconditionally safe reactor, which means it will not release radioactivity regardless of the severity of the natural or manmade disaster. Every conceivable catastrophic event – severe cyclones (hurricanes or typhoons), tsunamis, flood, fire and crashing aircraft – has been considered, with appropriate features incorporated in the design of SMR-160 to ensure that it will withstand these events without releasing radioactivity or pose any risk to public health and safety. In other words, SMR-160 is an industrial installation from which one will safely walk away in the wake of an unexpectedly severe natural disaster or act of sabotage, letting the plant’s innate defenses look after the reactor’s wellbeing.
Because SMR-160 is walk away safe, it can be sited next to population centers without any threat to the local environment or populace. It is as benign to its host locale as a cotton mill or a chocolate factory. Placing SMR-160 close to cities and towns will reduce transmission losses and enable the plant’s workers to live in the local community. A SMR-160 installation takes up less than 4.5 acres of land; this is a fraction of the land area required by other types of power plants.
A typical SMR-160 uses cooling water from a local natural source such as a lake, river or ocean to condense its exhaust steam. However, the SMR-160 can also be deployed in water-challenged regions by using air as the condensing medium. Note that a SMR-160 in an arid region will typically produce about 3% less power and require about one more acre of land.
SMR-160 achieves its supreme safety by eliminating vulnerabilities that have been the source of accidents in nuclear plants, namely pumps and motors to run the plant’s safety systems. Instead of motors and pumps, SMR-160 relies on Mother Nature’s gravity to run all safety significant systems in the plant. Because gravity can’t fail, a SMR-160 plant is assured to remain safe under every operating and accident scenario.
Replacing motors and pumps (that make a nuclear plant a menagerie of piping loops and networks) with gravity driven fluid flow systems not only hardens the plant against disasters like those that befell Fukushima, Chernobyl and TMI, but leads to huge reductions in the plant’s overnight, operating and maintenance costs.
In short, the commercial case for SMR-160 is as compelling as its safety case.
To summarize, the core strengths and innovation of SMR-160 are its inherent safety, security, constructability and simplicity of operation. The SMR-160 design is driven by the principal criterion that all safety significant systems must be powered by natural circulation (which is also called passive in the technical literature). Passive in every aspect of its operation, the paramount technical mission of SMR-160 is safety and security. This passive design feature is effective in all operational modes, including off-normal and accident conditions, and applies to all safety-related systems of SMR-160. The technical innovations that underlie the heretofore unattainable level of safety in SMR-160 are documented in an array of patent filings which provide intellectual property protection to the Company.
Innovative features of SMR-160 include:
- Core located deep underground
- A Passive Containment Cooling System integrates decay heat removal from the spent fuel pool and reactor core under off-normal conditions, including station blackout
- The plant can be started without off-site power (i.e., it is “Black start” capable)
- A large inventory of water available to the reactor core makes the scenario of an uncovered reactor core non-credible.
- Easy access to critical components for in-service inspection and testing in compliance with codes.
- No penetrations in the lower region of the Reactor Vessel; hence no pathway for inadvertent or accidental drainage of reactor water.
- Absence of boric acid in the plant helps increase the plant’s service life (longevity) which is estimated to be well over 100 years.
- On-site underground storage of used fuel in welded multi-purpose canisters.