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Research Papers: Nuclear Power

Dry-Cooled Supercritical CO2 Power for Advanced Nuclear Reactors

[+] Author and Article Information
T. M. Conboy

Advanced Nuclear Concepts,
Sandia National Laboratories,
P.O. Box 5800, MS1136,
Albuquerque, NM 87185
e-mail: tmc@creare.com

M. D. Carlson, G. E. Rochau

Advanced Nuclear Concepts,
Sandia National Laboratories,
P.O. Box 5800, MS1136,
Albuquerque, NM 87185

Contributed by the Nuclear Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 9, 2014; final manuscript received July 12, 2014; published online August 18, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(1), 012901 (Aug 18, 2014) (10 pages) Paper No: GTP-14-1355; doi: 10.1115/1.4028080 History: Received July 09, 2014; Revised July 12, 2014

Currently, waste heat rejection from electrical power systems accounts for the largest fraction of water withdrawals from the U.S. fresh water table. Siting of nuclear power plants is limited to areas with access to a large natural supply of fresh or sea water. Due to a rise in energy needs and increased concern over environmental impact, dry air cooling systems are poised to play a large role in the future energy economy. In practice, the implementation of dry air-cooled condensing systems at steam plants has proven to be capital-intensive and requires the power cycle to take a significant efficiency penalty. These shortcomings are fundamental to dry-air steam condensation, which must occur at a fixed temperature. Closed-cycle gas turbines are an alternative to the conventional steam Rankine plant that allows for much improved dry heat rejection compatibility. Recent research into advanced nuclear energy systems has identified the supercritical CO2 (s-CO2) Brayton cycle in particular as a viable candidate for many proposed reactor types. The s-CO2 Brayton cycle can maintain superior thermal efficiency over a wide range of ambient temperatures, making these power systems ideally suited for dry air cooling, even in warm climates. For a sodium fast reactor (SFR) operating at 550 °C, thermal efficiency is calculated to be 43% with a 50 °C compressor inlet temperature. This is achieved by raising CO2 compressor inlet pressure in response to rising ambient temperatures. Preliminary design studies have shown that s-CO2 power cycle hardware will be compact and therefore well-matched to near-term and advanced integral small modular reactor (SMR) designs. These advantages also extend to the cooling plant, where it is estimated that dry cooling towers for an SFR-coupled s-CO2 power cycle will be similar in cost and scale to the evaporative cooling tower for a light-water reactor (LWR). The projected benefits of the s-CO2 power cycle coupled to dry air heat rejection may enable the long-awaited rise of next-generation nuclear energy systems, while redrawing the map for siting of small and large nuclear energy systems.

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References

Figures

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Fig. 1

Selected results from ORNL study on power plant siting [16]

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Fig. 2

Coal plant in desert using natural draft dry cooling [18]

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Fig. 3

Comparison of S-CO2 power cycle to steam Rankine

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Fig. 4

S-CO2 power cycle efficiency at 550 °C with increasing compressor inlet conditions

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Fig. 5

CO2 equation of state, with lines of constant density

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Fig. 6

Cycle efficiency compared to maximum pressure, for various low-side pressures at 30 °C

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Fig. 7

Cycle efficiency compared to maximum pressure, for various low-side pressures at 50 °C

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Fig. 8

Comparison of s-CO2 power cycle operating conditions

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Fig. 9

Heat transfer profiles of the CO2 (red) and air (blue) streams in a CO2-to-air dry cooler; Tmin = 50 °C

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Fig. 10

Heat transfer profiles of the steam (red) and air (blue) streams in a steam-to-air dry cooler; Tmin = 50 °C

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Fig. 11

Heat transfer profiles of the steam (red) and air (blue) streams in a steam-to-air dry cooler; Tmin = 55 °C

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Fig. 12

Comparison of heat rejection plants for various nuclear systems for a fixed thermal load

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