A Look Back

One of the luckiest and best choices I ever made in my career was to come to work at Argonne National Laboratory in 1984. I had been managing plant systems and safety design in Tennessee at the U.S. Department of Energy’s Clinch River Breeder Reactor Demonstration Project, but when the project was canceled, I couldn’t help feeling disappointed and ready to move on. The change offered a new challenge, and at ANL, in Idaho and Chicago, I found myself managing the most exciting project of my life, the Shutdown Heat Removal Tests (SHRT) at Experimental Breeder Reactor-II.

The purpose of the tests was to demonstrate EBR-II’s impressive passive safety features—specifically the reactor’s ability to shut down on its own in response to an accidental loss of cooling—without powered equipment or operator intervention. I led a small group of experimenters who planned and ran the testing. Nearly everyone at EBR-II—Engineering, Operations, Fuels, and Analysis—owned part of the action. It involved long hours, but it was fun.

These important experiments we conducted at EBR-II decades ago have a direct bearing on a new generation of advanced reactors, including the Versatile Test Reactor (VTR) now under development. 

The tests started in June 1984 and were completed much faster than anyone might have expected. In the initial series of eight tests, we showed that the EBR-II reactor, a truly unique machine, could passively remove heat from the reactor core after being shut down by operators. (In nuclear language, this is called a scram—which is manual or automatic insertion of control rods to shut down a reactor.)

The most challenging test involved a station blackout—a total loss of electrical power. In other tests, we measured EBR-II’s power response to small reductions in cooling. The cooling was reduced by lowering reactor flow or by reducing heat removal to the heat sink—the steam plant that took heat from the reactor to generate electricity for the Idaho National Laboratory grid.

In every test, measurements of power, flow and temperature were close to predictions. This gave us confidence in our ability to test at higher levels of power and in more demanding accident-like conditions.

Over two more test periods—May 1985 and March 1986—we proved EBR-II’s ability to passively shut down in two of the most severe accident scenarios a reactor can face. The first involved loss of pumped coolant flow without inserting the reactivity control rods and the second involved a complete loss of heat removal to the heat sink, also without scram. Both were extremely unlikely and far beyond the safety design basis the U.S. Nuclear Regulatory Commission requires for power reactors, but the point of testing is to know for sure.

On the whole, it took almost two years and 50 tests for the EBR-II program to safely progress our way from test to test, confirming computer models at each step for increasingly extreme conditions. The tests also identified important reactor design features for passive safety. This was important not only for EBR-II but also for the design of future reactors, including the VTR that may be built in the United States in the next few years.

By the second year of the SHRT program, there seemed to be a renewed interest in advanced reactor technology. There were stories in the Wall Street Journal and on CNN on the experiments conducted. 

The results of this testing showed how impressive and compelling this was for reactor safety. These positive results led to other positive developments as well. Separate EBR-II tests on new advanced metal fuels were being developed by Argonne’s Integral Fast Reactor program. These tests showed fuel lifetime and uranium utilization could be extended significantly—maybe by a factor of two.

EBR-II continued to reliably generate electricity for ANL-West and the larger INL Site during the entire two-year SHRT program. DOE began envisioning a new generation of commercial reactors that could include passive safety features like those demonstrated in EBR-ll. These programs led to several new reactor concepts—some cooled with sodium, some with water, some with molten salt and some with gas. All the concepts had passive safety capabilities inherent in their design. Beyond that, these concepts were simpler, smaller and more modular, offering potential for lower construction and operation costs. 

One of these concepts, General Electric’s PRISM reactor, which incorporates many of the inherent safety features validated through the SHRT program, has been favorably reviewed by the U.S. Nuclear Regulatory Commission, but for a long time there was little movement toward commercialization. With the VTR, things have taken a turn. DOE has decided it is in the national interest to have a low-power test reactor that can supply a fast spectrum high neutron flux for materials testing. The PRISM reactor module has been selected as the starting point for the VTR design, which means the data collected from EBR-II, which has been shut down since 1994, can also be used to support the design and safe operations of this critical nuclear energy infrastructure test reactor.

Early in 2020, VTR’s conceptual design was completed and received DOE’s technical approval. I had the privilege of reviewing the VTR Conceptual Design. I was impressed with how passive safety features like those demonstrated in EBR-II have been modernized, extended and adapted to a 21st century test reactor design. VTR is being designed to have impressive safety features enclosed in a simple, reliable and safe test reactor. I know it can work because I saw it work, a long time ago, at EBR-II.

Pete Planchon is a senior technical adviser to Idaho National Laboratory, most recently involved in the conceptual design review of the Versatile Test Reactor. A veteran of the U.S. Navy, he was a senior engineer and manager of Westinghouse’s Clinch River Breeder Reactor Plant Systems from 1974 to 1984, then manager of reactor analysis for Argonne’s Experimental Breeder Reactor Division. When he retired in 2005, he was director of Argonne’s nuclear technology division. In 1996 he received the Seaborg Medal from the American Nuclear Society. His interests include hiking, skiing, photography, woodworking and reading. 

Click here to read more of the November issue of Idaho Falls Magazine.