Boiling Nuclear Superheater Reactor Facility

Coordinates: 18°21′59″N 67°16′7″W / 18.36639°N 67.26861°W / 18.36639; -67.26861
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Boiling Nuclear Superheater (BONUS) Reactor Facility
BONUS Reactor
CountryPuerto Rico
LocationPunta Higuero Sector, PR 413, Rincón
Coordinates18°21′59″N 67°16′7″W / 18.36639°N 67.26861°W / 18.36639; -67.26861
Construction beganAugust 13, 1960[1]
Commission dateDecember 19, 1965[1]
Decommission date
  • June 1968
Construction cost$23,737,062[1]
Owner(s)US Atomic Energy Commission and Puerto Rico Water Resources Authority
Operator(s)Puerto Rico Water Resources Authority
Nuclear power station
Reactor typeBWR
Thermal capacity50 MW
Power generation
Nameplate capacity16.5 MW
External links
CommonsRelated media on Commons

Boiling Nuclear Superheater Reactor Facility
Built byChicago Bridge Co.; Gen Nuclear Engineering
ArchitectAtomic Energy Commission; Maxon Co.
NRHP reference No.07001194[2]
Added to NRHPNovember 14, 2007

The Boiling Nuclear Superheater (BONUS) Reactor Facility, also known to the locals as "Domes", or formally as Museo Tecnologico BONUS Dr. Modesto Iriarte, is a decommissioned nuclear power plant in Rincón, Puerto Rico. It was listed on the U.S. National Register of Historic Places in 2007.[2]


BONUS was a prototype whose objective was to assess the economic and technical feasibility of the integral boiling superheating advanced reactor concept.[3] At the time, it was expected that developing higher-temperature reactors that could superheat steam was the next major step toward the achievement of a competitive status for nuclear power plants relative to fossil-fueled power plants.[3] Incremental energy added to steam in the form of superheat can be converted to electricity with an efficiency of 50-60%, compared to ~30% for energy added to saturated steam in traditional reactors.[3] The disadvantage of superheating is that higher temperatures can lead to more corrosion and fuel element failures, making the reactor more complex. BONUS was intended to identify whether or not the benefit was worth the challenge.[3]

The construction of BONUS started in 1960, and the reactor had its first controlled nuclear chain reaction on April 13, 1964. In September 1965 full power operation was achieved with 50 MW thermal power, and steam temperatures of 900°F (482°C).[4]

Operation of the BONUS reactor was terminated in June 1968 because of technical difficulties and the ensuing need for high-cost modifications. The Puerto Rico Water Resources Authority decommissioned the reactor between 1969 and 1970. During decommissioning, all special nuclear materials (fuel) and certain highly activated components (e.g., control rods and shims) were removed from the island to the US mainland, all piping systems were flushed, the reactor vessel and associated internal components within the biological shield were entombed in concrete and grout, and systems external to the entombment were decontaminated. Many contaminated and activated materials were placed in the main circulation pump room beneath the pressure vessel and entombed in concrete.[4]

General decontamination of the reactor was performed with the goal of meeting unrestricted use criteria in all accessible areas of the building. Residual radioactive materials remaining in the structure were isolated or shielded to protect site visitors and workers. During subsequent years, more radioactive contamination was identified in portions of the building, and additional clean-up and shielding activities were conducted in the 1990s and early 2000s.[4]


Perspective of the BONUS containment building in Puerto Rico [3]

The principle of operation is boiling water in the center of the reactor, (BWR), and passing the steam through the rest of the reactor, superheating; this steam drives a turbine generator.[5]

See also[edit]


  1. ^ a b c Author, Not Given (June 1966). Boiling Nuclear Superheater (BONUS) Power Station Project Completion Report (ORO-649). United States Atomic Energy Commission. doi:10.2172/4512116. Retrieved 23 September 2023. {{cite book}}: |last1= has generic name (help)
  2. ^ a b "National Register Information System – Boiling Nuclear Superheater (BONUS) Reactor Facility (#07001194)". National Register of Historic Places. National Park Service. November 2, 2013. Retrieved 2023-09-16.
  3. ^ a b c d e US Atomic Energy Commission (1962-05-01). "Boiling Nuclear Superheater (BONUS) Power Station : final summary design report". Division of Technical Information (PRWRA-GNEC-6).
  4. ^ a b c "BONUS, Puerto Rico, Decommissioned Reactor Fact Sheet" (PDF). Legacy Management. Department of Energy. 2023-07-01. Retrieved 2023-09-16.
  5. ^ "Boiling Nuclear Superheater – Rincón, Puerto Rico". National Toxic Land / Labor Conservation Service. Retrieved 28 June 2019.

External links[edit]

BONUS for Puerto Rico — A 1967 film about the reactor