United States United States · Lemont, IL · 43.533, -112.945 (approximate location)

ZPR-7 Argonne

ZPR-7 Argonne, a research reactor (critical assembly) in Lemont, IL, United States, with 10 W of thermal power, operated by US DOE. Decommissioned, first critical in 1957.

It was one of the 340 research reactors the United States has had; 48 remain in operation today. It went critical 15 years after the first research reactor in the United States, CP-1, Chicago Pile 1 (1942). 44 critical assemblies remain in operation today across 12 countries. Its declared uses include materials testing.

Country
United States
City
Lemont, IL
Type
Critical assembly
Thermal power
10 W
Operator
US DOE
Status
Decommissioned
First criticality
1957
Purpose
Materials testing

Data: IAEA RRDB · updated on Sep 3, 2026

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