U.S. Army Nuclear Reactors

References Consulted:
Quarterly Progress Report to the Joint Committee on Atomic Energy, April-June 1958. U.S. Atomic Energy Commission
Highly Enriched Uranium: Striking A Balance; Appendix D; Military Reactors
EM 1110-345-950 – Engineering and Design Utilization of Nuclear Power Plants in Underground Installations (15 April 1963)
AEC Annual Report to Congress, 1961.
Towards Longer-Life Army Reactor Cores by J.G. Gallagher in the March 1964 Nucleonics Journal

Background

The Army Nuclear Power Program (ANPP) was a joint venture of the Department of Defense and the Atomic Energy Commission. It was the sole agency for all three military services (Army, Navy, Air Force); for developing nuclear power systems that were not for vehicle propulsion. The objectives of the ANPP were:

a. To develop a family of nuclear power plants in the power range of about 100 KWE up to 40,000 KWE for all three military services.
b. To increase power and core lifetime.
c. To develop simpler and more rugged components.
d. To make plant operation as nearly automatic as possible and reduce crew size.
e. To reduce on-site construction time and costs.
f. To improve mobility.

During it's 23 years of life from 1954 to 1977 it achieved many “firsts” in the nuclear industry:

Reactor Core Types

Type 1 Core

Assembly Method: Brazed
Cladding Material:
304 Stainless Steel
Fuel Material:
Geneva Type UO2 Pellets
U235 Per Plate: 28.6 grams
U235 in Core: 22.5 kg
Burnable Poison: B4C
Core Life: 16.1 Megawatt/Years

Type 2 Core

Assembly Method: Brazed
Cladding Material:
347 Stainless Steel
Fuel Material:
Spherical UO2 Pellets
U235 Per Plate: 28.6 grams
U235 in Core: 22.5 kg
Burnable Poison: B4C
Core Life: 16.1 Megawatt/Years

Type 3 Core

Assembly Method: Welding
Cladding Material:
347 Stainless Steel
Fuel Material:
Spherical UO2 Pellets
U235 Per Plate: 46.3 grams
U235 in Core: 36.3 kg
Burnable Poison: ZrB2
Core Life: 32 Megawatt/Years

Type 5 Core

Assembly Method: Welding
Cladding Material:
347 Stainless Steel
Fuel Material:
Spherical UO2 Pellets
U235 Per Plate: 137.9 grams
U235 in Core: 108 kg
Burnable Poison: ZrB2
Core Life: 108 Megawatt/Years

Reactor Designations

First Digit (Mobility)

P: Portable; can be broken down and moved away from it's location as necessary.

S: Stationary; cannot be moved from it's installation location.

M: Mobile; can be moved with little or no preparation necessary other than connecting hoses or cables between trailers.

Second Digit (Power Output)

L: Low Power

M: Medium Power

H: High Power

Third Digit (Number Built)

A reactor having the designation PL-50 would mean it was the 50th Portable Low Power Reactor built under ANPP. Numbers are assigned sequentially.

Fourth Digit (Prototype/Field)

This digit, the letter “A” designates whether this was the prototype or field reactor for that sequence. E.g. SL-1 would be a prototype reactor constructed to prove the design; while SL-1A would be the first reactor built for general use by the services.

Reactors Designed/Constructed under ANPP

APPR-1B

Notes: In response to a Department of Defense requirement, the AEC is developing an improved APPR-type core system, designated as the APPR-1B, capable of producing about 2.5 times the reactor heat of the present APPR-1 core and having a minimum core life of one year at full power. The Intended application is to provide electric power for the Nike-Zeus air defense system.

APPR-2

Notes: The AEC agreed to participate in a 2-year joint development project with the Air Force to develop, procure, and test a second generation APPR-type plant, designated as APPR-2. The design will emphasize the optimum packaging of components in order to reduce construction time and effort at remote sites.

Portable Low Power Plant 1 (PL-1)

Reactor Type: Boiling Water
Cooling Type: Steam to Air
Power Output (Thermal): 3.6 megawatts
Power Output (Electrical): 252 kilowatts at 4,160/2,400 volts; 3 phase, 60 Hz.
Steam Heat: 1.7 million BTU/hr
Plant Volume: 15,980 ft3
Plant Weight: 280 tons (without buildings)
Number of Packages: 10
Plant Cost:
$2.07 million (FY63)
Erection Time:
60 Days

Notes: The design for this plant was completed 30 June 1961, and it would have been built around a low-enriched tubular core with pelletized fuel.

Portable Low Power Plant 2 (PL-2)

Reactor Type: Boiling Water
Cooling Type: Steam to Air
Power Output (Thermal): 7.48 megawatts
Power Output (Electrical): 1 megawatt at 4,160/2,400 volts; 3 phase, 60 Hz.
Steam Heat: 1.365 million BTU/hr
Plant Volume: 18,410 ft3
Plant Weight: 329 tons (without buildings)
Number of Packages: 14
Plant Cost:
$3.18 million (FY63)
Erection Time:
50 Days

Notes: The design for this plant was completed 30 June 1961, and it would have been built around a low-enriched tubular core with pelletized fuel.

Portable Low Power Plant 3 (PL-3)

Reactor Type: Pressurized Water
Power Output (Thermal): 9.3 Megawatts
Power Output (Electrical): 1 Megawatt
Steam Heat: 1.5 million BTU/hr
Core Life (Type 1 or 2 Core): 1.7 years at full power.
Core Life (Type 3 Core): 3.4 years at full power.
Core Life (Type 5 Core): 11.6 years at full power.

Portable Medium Power Plant 1 (PM-1)

Reactor Type: Pressurized Water
Cooling Type:
Steam to Air
Designer
: Martin Marietta
Power Output (Thermal): 9.37 megawatts
Power Output (Electrical): 1 Megawatt at 4,160/2,400 volts; 3 phase, 60 Hz.
Steam Heat: 7 million BTU/hr
Plant Volume: 33,000 ft3
Plant Weight: 240 tons (without buildings)
Number of Packages: 16
Plant Cost:
$3 million (FY63)
Erection Time:
75 Days
Criticality: 25 February 1962
Shutdown: 1968
Cores Expended: 2
Uranium-235 Enrichment: 93%
Uranium-235 Supplied: 60.8 kg

Notes: Provided power to the 731st Radar Squadron of NORAD, based in Sundance, Wyoming. Partially funded by USAF.

Portable Medium Power Plant 2A (PM-2A)

Reactor Type: Pressurized Water
Cooling Type:
Steam to Ethylene Glycol to Air
Designer
: American Locomotive Company (ALCO)
Power Output (Thermal): 10 megawatts
Power Output (Electrical): 1,560 kilowatts at 4,160/480 volts; 3 phase, 60 Hz.
Steam Heat: 1 million BTU/hr
Plant Volume: 60,819 ft3
Plant Weight: 300 tons (without buildings)
Number of Packages: 27
Plant Cost:
$4.5 million (FY63)
Erection Time:
78 Days
Criticality: 3 October 1960
Shutdown: 1963-64
Cores Expended: 1
Uranium-235 Enrichment: 93%
Uranium-235 Supplied: 18.2 kg
Core Life (Type 1 or 2 Core): 1.6 years at full power
Core Life (Type 3 Core): 3.2 years at full power.
Core Life (Type 5 Core): 10.8 years at full power.

Notes: Provided power to Camp Century in Greenland, and proved the ability to assemble a pre-fabricated nuclear plant in a remote location, and then remove it.

Portable Medium Power Plant 3A (PM-3A)

Reactor Type: Pressurized Water
Cooling Type:
Steam to Air
Designer
: The Martin Company
Power Output (Thermal): 9.36 megawatts
Power Output (Electrical): 1,500 kilowatts at 4,160/2,400 volts; 3 phase, 60 Hz.
Plant Volume: 42,700 ft3
Plant Weight: 450 tons (without buildings)
Number of Packages: 18
Plant Cost:
$5.25 million (FY63)
Erection Time:
77 Days
Criticality: 3 March 1962
Shutdown: September 1972
Cores Expended: 5
Uranium-235 Enrichment: 93%
Uranium-235 Supplied: 121.6 kg

Notes: Was sized to fit within C-130s. Modules were no bigger than 30 ft long, 8'8” wide, 8'8” high, or heavier than 30,000 lbs.

Provided steam heating and electric power to the Naval Air Facility at McMurdo Sound, Antarctica. Containerized version of PM-1. Operated by the U.S. Naval Nuclear Power Unit Detachment (PM-3A).

Mobile Low Power Plant 1 (ML-1)

Reactor Type: Gas Cooled
Cooling Type:
Nitrogen to Air
Designer
: Aerojet General Corporation
Power Output (Thermal): 3.4 megawatts
Power Output (Electrical): 330 kilowatts at 4,160/2,400 volts; 3 phase, 60 Hz.
Plant Volume: 2,978 ft3
Plant Weight: 38.5 tons
Number of Packages: 3
Plant Cost:
$5.5 million (FY63)
Erection Time:
12 Hours
Criticality: 30 March 1961
Shutdown: 1965

Notes: To test a reactor package that was transportable by semitrailers, railroad flatcars, and barges.

Mobile Low Power Plant 1A (ML-1A)

Notes: Field-Deployable version of ML-1.

Mobile High Power Plant 1A (MH-1A)

Reactor Type: Pressurized Water
Cooling Type:
Steam to Water
Designer:
Martin Marietta Corporation
Power Output (Thermal):
44.6 megawatts
Power Output (Electrical):
10 megawatts at 60 Hz. (66/44/33/22.9 Kilovots at 3 phase 60/50 Hz.)
Plant Volume:
374,900 ft3
Plant Cost:
$11.5 million (FY63)
Erection Time:
30 months
Criticality
: 24 January 1967
Shutdown: 1977
Cores Expended: 5
Uranium-235 Enrichment: 4 to 7%
Uranium-235 Supplied: 541.4 kg

Notes:: Installed in a converted Liberty ship, the Sturgis, which remained moored at Gatun Lake in the Panama Canal from 1978 to 1977.

Stationary Low Power Plant 1 (SL-1)

Reactor Type: Boiling Water
Designer
: Argonne National Laboratory
Criticality: 11 August 1958
Shutdown: 3 January 1961 (Destroyed)
Cores Expended: 1

Notes: Destroyed in an accident on 3 January 1961 which killed the three-man operating crew.

Stationary Medium Power Plant 1 (SM-1 or APPR-1)

Reactor Type: Pressurized Water
Designer
: American Locomotive Company (ALCO)
Power Output (Thermal): 10 Megawatts
Power Output (Electrical): 1,855 kilowatts at 4,160 volts 3 phase, 60 Hz.
Plant Volume: 177,900 ft3
Plant Weight: 288 tons (without buildings); 2,500 tons (with buildings)
Plant Cost: $4.6 million (FY63)
Erection Time: 18 months
Criticality: 8 April 1957
Shutdown: 1973-1975
Cores Expended: 3
Uranium-235 Enrichment: 93%
Uranium-235 Supplied: 72.7 kg
Core Life (Type 1 or 2 Core): 1.6 years at full power.
Core Life (Type 3 Core): 3.2 years at full power.
Core Life (Type 5 Core): 10.8 years at full power.

Notes: Located at Fort Belvoir, Virginia. Prototype for SM-1 family. Was the first reactor developed for ANPP; and was used to train operators.

Stationary Medium Power Plant 1A (SM-1A or APPR-1A)

Reactor Type: Pressurized Water
Designer
: American Locomotive Company (ALCO)
Power Output (Thermal): 20.2 megawatts
Power Output (Electrical): 1,640 kilowatts at 2,400 volts, 3 phase, 60 Hz.
Steam Heat: 46 million BTU/hr
Plant Volume: 243,100 ft3
Plant Weight: 3,000 tons (with buildings)
Plant Cost: $6.67 million (FY63)
Erection Time: 18 months
Criticality: 13 March 1962
Shutdown: 1972
Cores Expended: 4
Uranium-235 Enrichment: 93%
Uranium-235 Supplied: 117.1 kg
Core Life (Type 1 or 2 Core): 291 days at full power
Core Life (Type 3 Core): 1.6 years at full power.
Core Life (Type 5 Core): 5.3 years at full power.

Notes: Located at Fort Greely, Alaska. Was the first field facility under the ANPP. Was used to develop construction methods in a remote location.

Stationary Medium Power Plant 2 (SM-2)

Reactor Type: Pressurized Water
Power Output (Thermal): 28 Megawatts
Power Output (Electrical): 6 Megawatts at 4,160 volts, 3 phase, 60 Hz.
Plant Volume: 211,680 ft3
Plant Cost: $4.26 million (FY63)
Erection Time: 18 months
Core Life (Type 3 Core):
1.1 years at full power.
Core Life (Type 5 Core):
3.9 years at full power.

Notes: Prototype of the SM-2 Series. Originally a 6 MW(e) plant for reliable power at missile sites for Nike Zeus. Design requirements changed from 6 MW(e) to 12 MW(e); and this was accomplished by combining two SM-2 plants into a single complex.

Stationary Medium Power Plant 2A (SM-2A)

Reactor Type: Pressurized Water
Power Output (Thermal): 28 Megawatts
Power Output (Electrical): 6 Megawatts
Core Life (Type 3 Core): 1.1 years at full power.
Core Life (Type 5 Core):
3.9 years at full power.

Notes: This plant would have run off highly enriched plate-type fuel. First field unit of the SM-2 series.

Military Compact Reactor (MCR)

Reactor Type: Liquid Metal
Development: December 1955 to December 1965

Notes: The initial concept was for this reactor in a heavy overland cargo hauler. Later, it was transferred to the Nuclear Power Energy Depot program, which investigated ways to produce synthetic fuels in combat zones.