A Preliminary Feasibility Study for Small Modular Reactors and Microreactors for Puerto Rico was published on 20 May by the Nuclear Alternative Project (NAP).

It was prepared for the US Department of Energy (DOE) under Contract No 226818. The study began in October 2019 after it received a "notice to proceed" from DOE's Idaho National Laboratory.

NAP, a non-profit organisation comprised of Puerto Rican engineers, set up in 2015 to inform the people of Puerto Rico about advanced nuclear reactors, received further incentive as a result of the 2017 hurricane.

“In the aftermath of Hurricane Maria, where more than 3000 deaths were attributed to the lack of electricity and basic services, our educational effort evolved into one of need – to evaluate the feasibility of advanced nuclear reactors for Puerto Rico,” said NAP.

Currently, Puerto Rico generates 98% of its electricity from imported fossil fuels, and its ageing power plants, built in the late 1960s, suffer frequent blackouts. Within ten years, Puerto Rico proposes a transition from a fossil fuel-dependent centralised system to a distributed system based on clean energy. In 2018 the country's legislature passed a bill calling for an investigation into the possibility of building nuclear power plants.

The Integrated Resource Plan (IRP) proposed by the Puerto Rico Electric Power Authority (PREPA) calls for Puerto Rico to have new solar, storage and natural gas capacity totalling 3000MWe by 2025. The Puerto Rico Renewable Portfolio Standard mandates 40% renewable energy generation by 2025, 60% renewables by 2040 and 100% renewables by 2050.

The challenges identified by the study for deployment of advanced reactors in Puerto Rico are policy, engineering and public engagement related.

A site suitability analysis indicated that development of advanced nuclear reactors in Puerto Rico is feasible. NAP said a follow-up second phase study would evaluate the general site suitability for SMRs and microreactors for specific regions. The results of the study will be formally submitted to the Puerto Rico Energy Bureau (PREB) as part of the public comment for the ongoing IRP revision process.

Key findings of the study were:

Puerto Rico’s daily electricity demand (or load profile) peaks at approximately 10% from average and utilisation rates (load factors) in the range of 75%. Thus, power demands require steady baseload plants such as fossil or nuclear plants rather than intermittent renewable sources like solar and wind.PREPA’s plants are 28 years older and experience outage rates 12 times higher than the US average due to old equipment and high daily and seasonal power demands aggravated by damage from recent hurricanes and earthquakes. PREPA expects to retire 74% of its generation fleet in the next decade.The IRP indicates that by 2025, Puerto Rico should have new solar, storage and natural gas capacity in the order of 3000MW.Due to its tropical climate and isolated grid structure, Puerto Rico’s daily power demand and utilisation rates are not expected to change appreciably. Therefore, the proposed high reliance on renewables necessitates sufficient baseload capacity to support the power demand. However, only nuclear reactors can complement the intermittency of renewable power sources with zero-emission baseload power generation.A survey of more than 3000 residents of all ages and educational backgrounds found 94% of residents are interested in a nuclear option.There is an urgent need to provide the population and industrial sector with lower electricity costs. The overall net costs of electricity could increase by 50% by FY2024 through a Transition Charge levied to pay PREPA’s outstanding legacy debt, making Puerto Rico’s electricity prices among the highest in all USA jurisdictions.Puerto Rico’s fossil fuelled power plants produce more emissions than other mainland US states with a similar population.Advanced nuclear reactors combine reduced electricity costs, zero-emission baseload electricity and minimal dependency on fuel imports that can lead to a strong degree of energy security.SMRs and microreactors can support the required retirement of 74% of the ageing generation fleet and installation of new capacity.Given the recent hurricane and earthquake events in Puerto Rico, the need for enhancing the overall resiliency of the energy generating system is urgent.In 2017, oil and gas imports to Puerto Rico were disrupted after Hurricane Maria’s landfall. The need to maintain a high frequency of fuel imports to the Island would leave Puerto Rico vulnerable to future supply disruptions in case of natural events. However, the shipment for nuclear fuel for each SMR would be only every two years and 10-15 years for microreactors.Advanced nuclear reactors can promote smaller and more distributed future generation plants, which makes them suitable for Puerto Rico’s decentralised grid vision, particularly minigrids.Fuelled by job creation during construction and operation of the reactor and research funding for local universities, a local nuclear project could develop a nuclear workforce that could secure a global leadership positionThe delivery of electricity from SMRs and microreactors can be cost competitive compared with the natural gas generation from mobile gas units and CCGT units proposed by PREPA.There is a public misconception that nuclear power is prohibited in Puerto Rico. A 1990 Executive Order stated nuclear power was not a viable alternate energy source at taht time, but not that nuclear power plants were prohibited.It is expected that the Puerto Rico nuclear plant’s low-level waste will be shipped to a US licensed low-level waste disposal facility and used fuel would be stored on site and later shipped to a long-term high-level waste storage facility in the mainland US.Among the mandates in Act 120-2018, new energy generation producers would be contracting with a T&D concessionaire instead of PREPA.The suitability of sites for advanced nuclear reactors in Puerto Rico will be in accordance with US Nuclear Regulatory Commission (NRC).  regulations and addressed in Phase 2 of this project.

The study considered five SMR technologies:

the NuScale SMRX-energy’s Xe-100 SMRGE-Hitachi’s BWRX-300 SMRWestinghouse’s eVinciX-energy’s Remote Resilient Module (RRM).

The study says: The SMR technologies discussed in this report are capable of addressing issues of baseload capacity, load-following and grid stability. BWRX-300 and NuScale SMRs have nameplate ratings of 300MWe and 50MWe (per module) respectively. Baseload capacity requirements can be provided by a combination of BWRX-300 sites and/or NuScale multimodule sites.

Photo: Crashing surf on the beach at El Morro Fortress, San Juan, Puerto Rico