Researchers at Idaho National Laboratory have a new experimental tool to study nuclear fuel under simulated loss of coolant accident (LOCA) conditions in INL’s Transient Reactor Test (TREAT) Facility. A specialized experiment holder called a TWIST capsule holds a fuel sample surrounded by water, which can rapidly drain away during testing, simulating loss of coolant in a light water reactor environment.

While initial operation of MARVEL, a tiny microreactor that will be installed and operated inside Idaho National Laboratory’s Transient Reactor Test (TREAT) Facility, might not occur until 2025, testing of a nonnuclear prototype is now under way at the New Freedom, Pa., manufacturing facility of Creative Engineers, Inc. (CEI). The Department of Energy announced the start of prototype testing on September 20.

Researchers at Idaho National Laboratory have completed initial testing on a newly developed fuel test capsule that is expected to provide crucial performance data for sodium-cooled fast reactors. The Department of Energy announced on January 12 that the series of fuel testing experiments being carried out now at INL’s Transient Reactor Test Facility (TREAT) was developed through a joint project between the United States and Japan.

A full-scale, electrically heated prototype for the Department of Energy’s Microreactor Applications Research Validation and Evaluation (MARVEL) project was fabricated in just nine months, according to an article published by Idaho National Laboratory on January 31. The article explains in part how a team from the lab’s machine shop created the prototype.

Idaho National Laboratory recently released footage of a new experiment at its Transient Reactor Test Facility (TREAT) that simulates what happens to a nuclear fuel pin when it starts to overheat. Go to Twitter for the original post, or cut to the chase and watch a 14-second clip on YouTube.

The Department of Energy’s Office of Nuclear Energy is spreading the word about plans to build a tiny microreactor called the Microreactor Applications Research Validation & EvaLuation (MARVEL) project inside Idaho National Laboratory’s Transient Reactor Test (TREAT) Facility and have it in operation within the next three years. INL recently released a video that describes how MARVEL could help researchers and industry partners test, develop, and demonstrate the integration of a microreactor’s heat and electricity output with other technologies.

The Department of Energy launched a 14-day public review and comment period on January 11 on a draft environmental assessment for a proposal to construct the Microreactor Applications Research Validation & EvaLuation (MARVEL) project microreactor inside Idaho National Laboratory’s Transient Reactor Test (TREAT) Facility.

The basics: The MARVEL design is a sodium-potassium–cooled thermal microreactor fueled by uranium zirconium hydride fuel pins using high-assay, low-enriched uranium (HALEU). It would be a 100-kWt reactor capable of generating about 20 kWe using Stirling engines over a core life of about two years.

The DOE proposes to install the MARVEL microreactor in a concrete storage pit in the north high bay of the TREAT reactor building. Modifications to the building to accommodate MARVEL are anticipated to take five to seven months. Constructing, assembling, and performing preoperational testing are expected to take another two to three months prior to fuel loading.

Idaho National Laboratory’s Transient Reactor Test Facility, also known as TREAT, returned to service in 2017 after a hiatus of more than two decades. To make full use of TREAT’s capabilities, researchers at INL created the Minimal Activation Retrievable Capsule Holder (MARCH) test vehicle system, which, according to an August 26 Department of Energy press release, can cut years off the development process for nuclear fuels and materials and allow new clients, like NASA, to take advantage of TREAT’s capabilities.

View of the top of the TREAT reactor.

The Transient Reactor Test (TREAT) Facility at Idaho National Laboratory was restarted in 2018 after being in safe standby mode since 1994. The June 2020 issue of the American Nuclear Society's Nuclear Technology (NT) journal features seven technical papers related to the benchmarking of the facility. Wade Marcum, a lead researcher on the project and guest editor of June’s NT issue, explained, “The goal of this effort was to understand, to the best of our ability, the expected response of the TREAT reactor upon its restart.”