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The N-Reactor at the Hanford site along the Columbia River.

The N-Reactor was a water/graphite-moderated nuclear reactor constructed during the Cold War and operated by the U.S. government at the Hanford Site in Washington; it began production in 1963.

It was a one-of-a-kind design in the U.S., being both a plutonium production reactor for nuclear weapons and, from 1966, producing electricity to feed the civilian power grid via the Washington Public Power Supply System or WPPSS.[1]

In an improvement on the earlier Hanford reactors, N-Reactor was built with a confinement building (although not a containment building). In the event of an accidental release of steam, air and steam would vent through filters that confined any radioactive particles present.[2] It was partially moderated with graphite, but had a negative void coefficient due to also using moderation from the coolant water, meaning it was thermally stable.[3]

The reactor was shut down in 1987 and placed on cold standby in 1988, with "final disposition" beginning in 1994.

See also[edit]


  1. ^ HANFORD SITE: PROCESSES AND FACILITIES HISTORY, Section 2.2 N Reactor Operations Michele Gerber PhD, June 1996
  2. ^ US Department of State Bulletin, "Soviet nuclear reactor accident at Chernobyl"
  3. ^ David Bodansky, Nuclear Energy Principles, Practices, and Prospects, 2004

External links[edit]

Coordinates: 46°40′29″N 119°34′07″W / 46.674677°N 119.568672°W / 46.674677; -119.568672