You are here

Resumption of Transient Testing

April 15, 2013 - 11:11am


Resumption of Transient Testing Capability

The Department of Energy (DOE) is proposing to re-establish the capability to conduct transient testing of nuclear fuels. Transient testing involves placing fuel or material into the core of a nuclear reactor and subjecting it to short bursts of intense, high-power radiation. After the experiment is completed, the fuel or material is analyzed to determine the effects of the radiation. The resulting information is then used to guide the development and improvement of advanced nuclear fuel designs, and to validate computer models of fuel and core behavior required for U.S. Nuclear Regulatory Commission (NRC) evaluation of nuclear power reactor design and safety evaluations.

Transient testing of nuclear fuels is needed to improve current nuclear power plant performance and sustainability, to make new generation reactors more affordable, to develop nuclear fuels that are easier to recycle, safer and more efficient, and fuels that can’t be as easily diverted for use in making nuclear weapons.


  1. DOE believes the resumption of transient testing would aid in the development of new, advanced, safer and more efficient fuels that will generate additional quantities of clean, reliable, economical electricity with nuclear power reactors.
  2. The Transient Reactor Test Facility (TREAT) reactor at Idaho National Laboratory (INL) and the Annular Core Research Reactor (ACRR) at Sandia National Laboratories (SNL) are candidates for this activity. The INL has a long history of using TREAT and other nuclear reactors for safe and successful performance of transient testing of nuclear power reactor fuels. The SNL reactor also has a long history of safe and successful performance of a wide variety of experiments in nuclear science.
  3. During its decades of operation, TREAT provided “stress testing” of nuclear fuels – quick, high-energy neutron pulses that mimic accident conditions – to help the industry design even more durable fuels, establish performance limits, validate design codes, and help regulators (like the NRC) define safety limits.
  4. TREAT was designed and built specifically to support transient testing of nuclear fuels and materials. Resumption of transient testing at TREAT would require facility refurbishments. Modifications would be required to perform all required transient testing at ACRR.
  5. DOE has not made a decision about whether to conduct transient testing at either TREAT or ACRR. Completion of the National Environmental Policy Act (NEPA) analysis will enable DOE to examine the environmental impacts, if any, at both facilities and make a decision on a path forward.   
  6. Before a decision is made on whether to resume transient testing at TREAT, or to perform transient testing at ACRR – or anywhere in the United States – we will conduct the appropriate NEPA analysis to determine the potential environmental impacts of the proposed action. This will include an opportunity for the public to review the draft NEPA analysis document we will produce, for the public to comment on that study, and for DOE to respond to public comments.


Q: What is the justification for resuming transient testing of nuclear fuel?

A: Transient testing of nuclear fuels is needed to develop and prove the safety basis for advanced reactors and fuels. The safety basis for a reactor system requires a complete understanding of what could happen to the reactor fuel if it were subjected to accident conditions such as large power increases and loss-of-cooling events. Demonstrating understanding of the safety basis means you can predict the behavior of the reactor and the fuel and thus limit operation to safe conditions.

Advanced reactor designs will require new fuel types. These fuels could be quite different from the ones that were tested in the past: different geometries to enhance their cooling, different compositions to help significantly reduce the amount of waste generated during the production of nuclear energy, and different materials to improve their thermal and safety performance. These new fuels need to be proof tested in a controlled environment and researched extensively in order to learn how they respond to accident conditions. This understanding will help guide the design of fuels with much better performance.

When the nuclear power industry started, engineers needed a way to determine the safety limits of nuclear reactor operations, such as the temperatures, pressures and power at which the reactors could be safely operated. One issue that had to be addressed was “under what conditions would the fuel in the reactor fail?” or “what happens when cooling is suddenly lost?” Similarly, engineers needed to develop computer models that could be used to predict what would happen when accidents occurred.  In order to determine this, they used transient testing to expose full-sized reactor fuel rods to intense, very short duration power bursts or under-cooled conditions that simulated high power and loss-of-coolant accidents.  These experiments told fuel designers, reactor operators and reactor regulators the safe limits for fuel design and operations.

Transient testing of nuclear fuels is also needed to improve current nuclear power plant performance and sustainability, to make new generation reactors more affordable, to develop nuclear fuels that are easier to recycle, and fuels that can’t be as easily diverted for use in making nuclear weapons.

Q: Are there specific, identified customers who are willing to pay to use transient testing capability? If so, who?

A: While the DOE is responsible for several programs related to advanced nuclear fuel development, Accident Tolerant Fuel development is the most near term program that would benefit from the resumption of a transient testing capability. This program aims to design, develop and deploy new nuclear fuel designs for current generation nuclear power plants with the ability to mitigate the consequences of severe accidents through improved fuel performance. The development effort for these fuels will require a wide range of testing capabilities. The capability to conduct safety testing in a transient test reactor is a key component of the testing capability that must be added to meet this objective.


Q: When does DOE plan to resume transient testing?

A:  In December 2010, the DOE determined that there is a mission-need for a domestic transient testing capability for developing nuclear fuels. If DOE decides to resume transient testing, it could resume as early as 2018. Over the past two years, the Department has conducted an alternatives analysis that examines multiple options for resuming transient testing to aid in determining the suite of reasonable alternatives. DOE is currently in the National Environmental Policy Act (NEPA) phase of planning. During this phase, DOE will evaluate the potential environmental impacts, if any, of resuming transient testing capabilities for two alternatives, TREAT or ACRR, as well as a no action alternative. After the NEPA analysis is completed, DOE will have a better understanding of the environmental impacts of resuming transient testing and will make a decision on the path forward.

Q: How will the decision be made on whether to resume transient testing?

A:  DOE has initiated the NEPA review process that will help DOE decide whether or not to resume transient fuel testing by restarting TREAT or adapting ACRR. The decision to restart TREAT or adapt ACRR will be made only after the NEPA analysis and determination is completed. If the decision is made to resume transient testing capabilities, DOE will not resume actual testing until the requisite equipment replacements and refurbishments are completed and an extensive readiness preparation and review confirms safety and operational readiness.
Q: Will DOE perform an Environmental Impact Statement (EIS) prior to resuming transient testing? If not, why not?

A: DOE issued an Environmental Assessment Determination (EAD) in accordance with DOE Order 451.1B Change 2 “National Environmental Policy Act Compliance Program” in September 2011. The EAD concluded that an Environmental Assessment is the appropriate level of NEPA review in accordance with DOE and Council on Environmental Quality regulations. If we knew that the proposal would have significant environmental impacts the EIS would be the appropriate initial level of NEPA analysis. If the Environmental Assessment concludes with a Finding of No Significant Impact, an Environmental Impact Statement will not be required. If the analysis documents the potential for significant environmental impact, an EIS will be prepared.

Q: Which office will fund the refurbishment, restart and operation of TREAT, if the DOE decides to restart it, or the use of ACRR for transient testing?

A: The DOE Office of Nuclear Energy.


Q: What is TREAT and what was it used for?

A: The TREAT (Transient Reactor Test Facility) reactor at Idaho National Laboratory was used to conduct experiments investigating the effects of nuclear reactor transients, which are rapid and very short duration changes in power, on both water and sodium-cooled nuclear fuel systems. Much of the safety basis for fast reactors such as INL's Experimental Breeder Reactors I and II, the Pacific Northwest National Laboratory’s Fast Flux Test Facility, the Japanese Joyo and Monju reactors, and the Westinghouse AP-600 light-water reactor is based on tests conducted at TREAT.

Q:What is ACRR and what is it used for?

A: The ACRR (Annular Core Research Reactor) is a water-moderated, pool-type research nuclear reactor (CAT-II) capable of steady-state, pulsed and tailored transient operations. It is currently used to support defense and nuclear testing of electronic equipment for the National Nuclear Security Administration (NNSA).

Q: When was ACRR built and how long has it been operating?

A: ACRR started operations in 1979 and has been in operation for more than 33 years.

Q: When was TREAT built and when was it last operated?

A: TREAT began operation on Feb. 23, 1959 and has been upgraded several times since then. It has not operated since early 1994 because there were no customers for the facility at that time. The Integral Fast Reactor Program (EBR-II) was canceled that same year and the commercial industry had well-established fuel performance that did not require an active transient testing capability.


Q: Were there any reactor accidents associated with TREAT during its operation?

A:  No. TREAT is a steady state low-power reactor that can generate very short, high-power transients. During its 35-year operation, the TREAT reactor was used for 2,855 high-power transient experiments using a short burst of power lasting, often, mere milliseconds. The reactor rapidly shuts itself down because of the inherent self-limiting design of its core. Unlike most commercial power reactors that are cooled with water, TREAT is cooled using air at or slightly below atmospheric pressure.

Q: Were there any reactor accidents associated with ACRR during its operation?

A: No. In its more than 33 years of operation, ACRR has safely conducted more than 10,000 critical operations including irradiation of explosive components for defense programs and development, radioactive materials (e.g., fission products, tritium), nuclear and nuclear fuel materials (e.g., fissionable material as commercial, experimental, and space reactor fuel types), and nuclear fuel safety studies.

Q: Overall, what are the comparative costs of the two options (ACRR compared with TREAT)?

A: The NEPA process is designed to determine whether there are any significant environmental impacts associated with proposed actions. DOE is going through the EA process to determine the potential for environmental impacts of the two action alternatives. At the same time, DOE is compiling and will be examining the cost estimates for both alternatives. DOE will factor cost information into its decision on the best path forward.