Hot gas duct pressure vessel

The reactor core and the SG are housed in two steel pressure vessels that are connected by a connecting vessel. Inside of the connecting vessel, the hot gas duct is designed. All of the pressure retaining components, which comprise the primary pressure boundary, are in touch with the cold helium of the reactor inlet temperature. The primary pressure boundary consists of the reactor pressure vessel (RPV), the SG pressure vessel (SGPV), and the hot gas duct pressure vessel (HDPV), which all are housed in a concrete shielding cavity as shown in Fig. 14.8. 

The reactor and the steam generator are arranged side by side. The pressure boundary of the primary circuit is consisted by the reactor vessel, the steam generator vessel and the connected vessel (hot gas duct vessel)... 

Since the above-core calculations represented an infinite array of fuel channels, they did not include those parts of the pressure vessel in the vicinity of the hot gas duct penetration and therefore no account was taken in the above-core calculation of the neutrons wMch scatter around the top comer of the graphite stack and enter the hot gas duct penetration area. The neutron fluxes in the vicinity of the hot duct entrances were therefore takai to be equal to the fluxes calculated for the side shield model with a contribution added to account for the top-core leakage component. This component was scaled fi om the sub-core results and is considered to probably result in pessimistically high flux values for the hot gas duct pen ration since the neutron flux levels below the core are generally higher than those above. 

In designing closed helium cycles, a major cost driver is the volume of ducting required to transfer helium between equipment, because it affects the cost of the pressure boundary. It is doubtful that one will be able to identify a more compact configuration for the MCGC than this multiple-shaft design with annular rings of heaters around each turbine, because all flows enter at the optimal elevation in the vessels, and the hot gas flow path is extremely short. 

Argon gas from an auxiliary argon circuit covers the sodium surface to prevent any contact with air. The sodium contained in the primary vessel is operated at a pressure slightly higher than atmospheric. The hot and cold sodium pools are separated by an inner vessel. An upper core structure is suspended from the small rotating plug and contains control rod guide ducts and thermocouples. 

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