The US Department of Energy is planning to build a microreactor

The US Department of Energy (DOE) is planning to build a microreactor. Its RD&D activities should help researchers and end-users understand how microreactors can be integrated with other technologies. Microreactor Applications Research Validation and EvaLuation (MARVEL) liquid-metal cooled microreactor could be operational within three years.

What is Microreactor

Small modular reactors (SMRs) have been and have been in development for decades. Recently, due to their characteristics, they have come to the forefront of interest of many organizations and states.

There is no clear agreement on what else is and what is no longer a small modular reactor. Generally, two different divisions are used. One is according to the International Atomic Energy Agency (IAEA) and the other according to the US Department of Energy (DOE).

The IAEA defines small, medium and large reactors according to the output electrical power. Reactors up to 300 MWe are classified as small reactors.

The US DOE, on the other hand, classifies reactors according to thermal output. DOE defines small reactors as units up to 1000 MWt (which corresponds in size to about 300 MWe) and mini reactors up to 50 MWe or 250 MWt. In addition, some manufacturers come up with new classes and classifications for marketing (microreactor – Westinghouse Electric Company) or rank their medium-sized reactors among SMRs (Rolls Royce), which further complicates the definition of SMRs.

Classes and classifications of SMR according to manufacturers

 Reactor IAEA US DOE
 Micro Undefined up to 50 MWe or 250 MWt
Small up to 300 MWe up to 1000 MWt
Medium 300 – 700 MWe 1000 – 2000 MWt
Big more than 700 MWe more than 2000 MWt

Microreactors are very small, factory fabricated devices. There are transportable reactors. The Microreactors could provide power and heat for decentralised generation in civilian, industrial and defence energy sectors. The DOE Microreactor Program, led by Idaho National Laboratory (INL), is carrying out fundamental and applied R&D. Main objective is to reduce the risks associated with new technology performance and manufacturing readiness of microreactors.

Microreactor prototype MARVEL

The MARVEL design is primarily based on existing technology and will be built using off-the-shelf components allowing for faster construction. It will encompass a 100 kW thermal fission reactor, based on the SNAP-10A design. It was developed in the 1960s  for use in space missions. The sodium-cooled reactor, with natural circulation cooling, will have an operating temperature of 500-550°C. It will use Stirling engines to transfer energy from the core to make electricity.

DOE said the reactor, which will be built inside the Transient Reactor Test facility (TREAT) at INL, could be installed in less than a year.

Research and Development objectives

“By providing prompt, small-scale demonstrations, MARVEL will offer experimental capabilities that are not currently available at DOE’s national laboratories,” the department said. The test bed will help also help companies demonstrate their designs. Industry partners will be able to connect their microreactor end-user applications to the system to test and demonstrate technology readiness. MARVEL will also test and demonstrate the reactor system’s capability to manage grid demand and reactor power supply. Therefore this could support a range of applications such as integrated renewable energy systems, water purification, hydrogen production, and heat for industrial processes.

The MARVEL test platform is a collaborative effort between the DOE Microreactor Program and the National Reactor Innovation Center. DOE in January opened to public comment a draft environmental assessment for its proposal to construct the reactor. The US Department of Defense is also working to develop a mobile microreactor through its Project Pele initiative.

INL has released a video describing the MARVEL project.