US regulator approves methodology for SMR emergency planning

28 October 2022

The US Nuclear Regulatory Commission's acceptance of NuScale's methodology for determining the appropriate size of the Emergency Planning Zone (EPZ) around small modular reactor (SMR) plant sites is a "tremendous 'first'", the company's CEO said. The methodology can now be used to determine an EPZ for the NuScale SMR that provides the same level of protection to the public as the 10-mile radius used for existing US nuclear power plants.

A rendering of the proposed UAMPS plant: the new methodology could see the EPZ limited to the site boundary (Image: UAMPS)

NuScale CEO John Hopkins' comments followed the US Nuclear Regulatory Commission's Advisory Committee on Reactor Safeguards' (ACRS) decision, published on 19 October.

The EPZ is the area surrounding a nuclear power plant where special considerations and management practices are pre-planned and exercised in case of an emergency. The requirements for US emergency planning (and sizing of EPZs, which are based on a generic plume exposure pathway with a radius of 10 miles) are set out in regulation NUREG-0396, which was issued in 1978 - and based on large reactors.

"Since then, the knowledge base and analytical tools have advanced considerably, allowing for a more mechanistic, systematic approach to sizing the plume exposure pathway EPZ rather than using a bounding generic EPZ radius," the ACRS said in its decision.

The "source terms" - the types and amounts of radioactive or hazardous materials that could potentially be released following an accident - are much less for SMRs than for large reactors. SMR designs also incorporate emergency planning considerations as part of the design, with enhanced safety margins and passive or inherent safety systems built in. Such reactors are therefore envisaged as requiring a much smaller EPZ than larger plants - an important consideration for siting.

NuScale's integrated pressurised water reactor is the first SMR design to receive approval from the US Nuclear Regulatory Commission. The methodology the company has developed for assessing plume exposure pathway EPZ sizing for a NuScale SMR plant is risk-informed, provides a technically consistent approach (with NUREG-0396) for EPZ sizing, and adequately considers seismic and multi-module impacts, the ACRS said.

Using the newly approved method means an EPZ that is limited to the site boundary of the power plant is achievable for a "wide range of potential plant sites" where a NuScale VOYGR SMR power plant could be located, the company said. Limiting an EPZ limited to the site boundary means that users of the plant's output, such as off-takers of process heat, can be located nearer to the plant, and significantly reduces emergency planning costs for plant owners.

"Safety is NuScale's priority, and on top of our design approval in 2020, this endorsement from a world-class regulator - the US NRC - and the ACRS shows the global community our unmatched, innovative technology is first and foremost safe," Hopkins said. "This also means NuScale's game-changing technology can be sited where it's needed most - powering our economy, communities, and lives."

Portland, Oregon-based NuScale plans to build its first SMR power plant for Utah Associated Municipal Power Systems' (UAMPS) Carbon Free Power Project at a site at Idaho National Laboratory, with the first unit expected to begin generating power in 2029.

Researched and written by World Nuclear News