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ATR Achieves Criticality

The 250-megawatt (thermal) Advanced Test Reactor, the world’s highest neutron flux reactor for materials testing, achieved criticality (sustained a controlled chain reaction) July 2.

“The ATR can now proceed toward eventual operation at full power to provide valuable design data for atomic power plants of the future,” AEC-Idaho Manager W.L. Ginkel said.

ATR Achieves Criticality July 2

This article is reprinted from the lab publication Idaho Nuclear News of July 1967.

The 250-megawatt (thermal) Advanced Test Reactor, the world’s highest neutron flux reactor for materials testing, achieved criticality (sustained a controlled chain reaction) July 2. The ATR is operated for the U.S. Atomic Energy Commission by Idaho Nuclear Corporation.

“The ATR can now proceed toward eventual operation at full power to provide valuable design data for atomic power plants of the future,” AEC-Idaho Manager W.L. Ginkel said.

Regarded as the largest reactor of its kind in the world, the ATR is the forty-first reactor to achieve criticality at the NRTS since its establishment in 1949.

The new reactor will further internationally renowned work being done at NRTS in the 40-megawatt Materials Testing Reactor (MTR) and the 175-megawatt Engineering Test Reactor (ETR). From these test reactors the AEC obtains performance data for designing future reactor cores by studying the interaction of neutrons with sample materials such as new reactor fuels and structural materials proposed for use in future civilian or military reactors.

Phillips Petroleum Company’s Atomic Energy Division developed the conceptual design for the new test reactor, and the detailed design was performed by Ebasco Services, New York City. Babcock and Wilcox, Lynchburg, Va., provided the design for the ATR internals and control and safety systems. The construction contractor was Fluor Corporation Inc., Los Angeles. Howard S. Wright and Associates, Seattle, is constructing a gas experiment loop, scheduled for completion late next year. Meanwhile, the ATR will be operated without the gas cooled loop.

Total estimated cost of the ATR including the gas cooled loop, is about $58,000,000.

The ATR’s core design will permit multiple, yet simultaneous materials irradiations under a wide choice of conditions. Extending through the four-foot-deep core are nine tubes for accommodating test samples in the core region. Each tube can be made into a completely closed test loop with its own pumps, heaters, and other special equipment outside the reactor containment.

Unique in the ATR is the arrangement of its fuel elements, as viewed from above the core. In most present-day reactors, the fuel is arranged in one of several conventional forms – circular, rectangular, or polygonal. In the ATR core, the fuel elements are arranged side-by-side in a serpentine four-leaf-clover shape, leaving nine experiment loop spaces in the core. Four of these spaces are in the centers of the “leaves” and one space is at the junction of the leaves. The other four spaces are situated between the four leaves.

Idaho National Laboratory Research Programs

Department of energy

DOE Office of Nuclear Energy
DOE-Idaho Office
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