Direct cycle reactor system

Fig. ]. Contemporary direct-cycle reactor system used in boiling water reactor. (General Electric.1...

In direct cycle reactors, the design of the steam drying system should be such as to ensure that the levels of radiation and surface contamination in the turbine building are low. 

In addition, in direct cycle reactors, provision should be made for monitoring of the condenser air removal system. In PWRs this is also useful for the detection of ruptures of steam generator tubes. In gas cooled reactors, provision should be made to sample and monitor all operational discharges of the reactor coolant. 

The CCR is a direct cycle reactor, with its primary coolant system being also the main heat ransport system (MHT), The function of the MHT is to remove nuclear heat from the reactor core through natural circulation in both operating and shut down conditions. The design objectives are to achieve a Minimum Critical Heat Flux Ratio (MCHFR) of at least 1.5 at 120% full power and to ensure thermal-hydraulic stability during all operating conditions. 

For all water cooled reactor types, the pressure retaining boundary of the RCS extends up to and includes the first passive barrier or first active isolation device (as viewed from the core). For indirect cycle reactors, such as pressurized water reactors (PWRs), the pressure retaining boundary of the RCS includes the primary side of the steam generators (see Annex II). For direct cycle reactors, such as boiling water reactors (BWRs), the pressure retaining boundary of the RCS also includes the primary coolant recirculation system and the steam and feedwater lines up to and including the outermost isolation valve. 

In direct cycle reactors (BWRs) that have a suppression pool within the containment, an adequate capability for isolation of the main steam line, the release of steam through safety relief valves to the suppression pool and a corresponding feedwater system should be ensured (see Ref. [3]). 

Research and development of direct cycle helium turbine technologies including coupling a helium turbine system to the current HTR-10 reactor configuration. 

There is some continuing interest in gas-cooled reactors in South Afi ica, China, and Russia. ESKOM, the South African state-operated utility, is interested in a hi -temperature, gas-cooled reactor combined with a direct cycle gas turbine for powering rural areas that are currently without electricity. They have developed a preliminary design for a system based on the pebble bed reactors developed in Germany. General Atomic and Russia, in cooperation with others, have also completed a study on design of a gas-cooled gas turbine plant for use in Russia. China has operated a 5 MWt gas-cooled reactor and has plans for construction of a 200 MWt which is intended for process heat applications. 

Intermediate periodic operation lies between both extremes and covers systems in which the response time is of the same order as the imposed function cycle time so that resonance is possible. Here the state of the mechanism changes dynamically and is not directly related to the environmental conditions at the moment considered. Intermediate periodic operations encompass semibatch periodic operations, selectivity in periodically forced CSTRs, cycled reactors with heterogeneous catalysts, and non-steady-state biofilm reactors (e.g., Rittmann and McCarty, 1981). Lag, overshoot phenomena, and oscillations can typically occur. Biological reactor operation will basically fall into this latter class of operation, and balanced growth must be distinguished from steady-state growth (Barford et al., 1982). 

Power conversion system cost. The costs of the power conversion system were estimated from Ref. 49. Costs are reported only at the two-digit code of account level. In addition, the turbine plant equipment, account 23, was combined with the reactor plant equipment, account 22, as GA contended that all this equipment was part of the reactor system. In order to estimate the portion of these combined costs that applied to power conversion, cost partition factors were estimated by utilizing an earlier direct cycle MHTGR document. ... 

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