Indirect cycle

Gas turbines can operate in open or closed cycles. In a simple cycle (also known as an open cycle), clean atmospheric air is continuously drawn into the compressor. Energy is added by the combustion of fuel with the air. Products of combustion are expanded through the turbine and exhausted to the atmosphere. In a closed cycle, the working fluid is continuously circulated through the compressor, turbine, and heat exchangers. The disadvantage of the closed cycle (also known as the indirect cycle), and the reason why there are only a few in operation, is the need for an external heating system. That is an expensive addition and lowers efficiency. 

New promising designs have been proposed such as the one under an extensive industrial study on plate IHX to develop fabrication, ISI methods and a design standard for gas reactors [51], and another plate-type design for the indirect cycle reactor plant [52]. These works demonstrate that a plate IHX would simplify integration in the primary system because of its drastically reduced size. 

The concept of a 900 MW(e) HTR (thermal power 2250 MW) has been developed to operate in an indirect cycle for electricity generation with the extraction of process steam to be used for coal gasification employing an improved Lurgi process. The plant is to provide 110 kg/s of process steam at 400 °C and 10 MPa. 

The major difficulty to limit the higher thermal efficiency of the indirect cycle is the lower core inlet temperature. For the direct cycle, the cold gas leaving the precooler can be extracted to cool the reactor pressure vessel (RPV) and the other steel structures. Therefore the core inlet temperature can be as higher as 500- 600°C. For the indirect cycles proposed before, such as MGR-GTI proposed by Yan and Lidskyl, the core inlet temperature is kept as lower as 310°C in order to cool RPV The plant busbar efficiency of MGR-GTI is about 42.1%. In order to achieve higher power plant efficiency, it seems special designs of RPV cooling should be provided for the indirect gas turbine cycle. 

Currendy it is shown that the fuel particle has a high reliability and that the plant safety can be assured even with the direct cycle system, and since the potential feasibility of the indirect cycle system could be high if die direct cyde system is realized, the conceptual design of the direct cycle system has been conducted in our present research. 

CAREM is an indirect cycle reactor (100 MWt, approximately 27 MW(e)) with some distinctive features that greatly simplify the reactor and also contribute to a high level of... 

S PRISM ICONE-9 two blocks 1000 MW(t) per reactor indirect cycle Block scaling exponents derived from ALMR" 1-3 blocks S-PRlSMone block two reactors 1000 MW(t) per reactor indirect cycle Estimated cost factors 2 to 1 reactors in same block S-PRISM 1/2 block one reactor 2400 MW(t) GT-910720/1 target costs 4 X 600 MW(t) [1145 MW(e)] direct cycle AHTR-IT 2400 MW(t) [1145 MW(e)] indirect cycle AHTR-VT 2400 MW(t) [1300 MW(e)] indirect cycle Cost basis... 

Another possibility is to develop a direct gas turbine system at high temperature and pressure to increase the efficiency. Since helium has small cross section for neutron capture and is also chemically inactive, no induced radioactivity and no corrosion products can be expected in the coolant. Furthermore, the oxidative microparticle fuel coated with layers such as pyrolytic carbon or silicon carbide is expected to prevent the release of the fission gas into the coolant. Eventually the HTGR is suited to adopt the direct cycle, i.e., the gas turbine cycle, which allows building a more compact electric-power facility than the indirect cycle with a steam turbine system. While the thermal efficiency of electricity generation by steam turbine is about 40%, the gas turbine cycle can increase the efficiency up to ca. 50%. 

Cycle type Indirect cycle with 23% efficiency ... 

The VBER-150 is an indirect cycle water cooled and water moderated reactor. Hot coolant from the core is cooled in a once-through steam generator on its secondary side a slightly superheated steam is produced and supplied to the turbine. 

The PSRD is an indirect cycle light water cooled tank-type small reactor with an integral design of the primary circuit. Steam generator is located inside the reactor vessel. The PSRD is designed to achieve system simplification, resulting in the reduction of costs for construction, operation and maintenance. The assessments of the plant economy are... 

The Package-Reactor is designed to operate in an indirect cycle it uses the backpressure steam turbine with a target of about 20% thermodynamic efficiency. 

A PWR type reactor operating at 160 bar with the selected inlet/outlet temperatures will have about 33% efficiency with an indirect cycle. 

Cycle type Cycle efficiency Indirect cycle with gas turbine Brayton cycle secondary side using supercritical carbon dioxide as the working fluid at 20 MPa. 44.0% ... 

The STAR-LM vertical cross-section and schematic diagram are given in Fig. XXM-l and XXin-2, respectively. The STAR-LM is an indirect cycle lead cooled reactor. The traditional Rankine steam cycle has been replaced with a gas turbine recompression Brayton cycle that utilizes S-CO2 as the working fluid. Its thermophysical properties immediately above the critical point result in a relatively low work requirement to compress the S-CO2 fluid. The S-CO2 gas turbine Brayton cycle power converter for electricity production provides a cycle efficiency of 44.9% at a core outlet Pb temperature of 588°C. 

Cycle type Indirect cycle intermediate loop of forced circulation molten salt. Ca-Br thermochemical water cracking cycle/ supercritical CO2 Bra54on cycle with a feed-forward multi-effect distillation bottoming cycle... 

The SPINNOR and VSPINNOR are designed to operate within an indirect cycle without intermediate heat exchanger. Rankine cycle with superheated steam at about 7MPa is used. The thermodynamic efficiency is 35-37.5%. 

Cycle type Indirect cycle Supercritical steam Rankine cycle steam conditions at turbine inlet p=24 MPa, T=810 K... 

HTR-PM (China) 380 160 2010 Conceptual design 1% Yes Indirect cycle with reheating steam turbine... 

The CAREM design is based on an integrated light water reactor with low enrichment uranium fuel. It is an indirect cycle reactor with some distinctive features that essentially simplify the design and also contribute to high level of safety. The basic design features are [4] ... 

MWt 1996k 2000 MWt 1996k 2000 MWt Indirect cycle 2400 MWt 1996k Direct cycle 2400 MWt 1994k Indirect cycle 2400 MWt 1996 k ... 

Fig. 6.19. Cooling circuit for a gas-cooled reactor (indirect cycle).

CAREM is an indirect cycle reactor with a standard steam cycle of simple design. A thermodynamic efficiency of 33% is estimated for CAREM-300. 

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