Patent Number: 047132132
Section: claims

1. A nuclear reactor plant comprising a gas cooled small high temperature reactor, housed in a steel pressure vessel, the reactor having a core containing a pile of spherical fuel elements and traversed from bottom to top by a flow of primary helium gas, a heat utilization system arranged in the flow of cooling gas and installed above the small high temperature reactor in the reactor pressure vessel and which is followed in line preferably by two circulating blowers connected in parallel;  the heat utilization system comprising a He/He heat exchanger in which the primary helium transfers its heat to secondary helium circulating in an intermediate circulation loop;  the He/He heat exchanger comprises an inner annular coil bundle, extending to a hot gas collector chamber located above the reactor core and exposed from below to hot primary helium cooling gas and an outer coil bundle arranged concentrically and connected successively where the inner coil bundle is of greater length than the outer coil bundle and only the inner coil bundle extends to the hot gas collector chamber;  at least one decay heat exchanger installed in the steel pressure vessel;  the decay heat exchanger is arranged immediately following the He/He heat exchanger in the direction of flow, and is constantly traversed by the entire flow of cooling gas. 2. A nuclear reactor plant according to claim 1 wherein the steel pressure vessel comprises a drawn-in center part and a re-expanding upper part, with the latter containing the outer coil bundle and the heat exchanger. 3. A nuclear reactor plant according to claim 1, wherein the direction of the flow of primary helium is reversed at an upper end of the inner coil bundle and that the outer coil bundle is exposed to the flow of cooling gas from above. 4. A nuclear reactor plant according to claim 1, wherein the decay heat exchanger has an annular configuration and surrounds the inner coil bundle concentrically below the outer coil bundle. 5. A nuclear plant according to claim 4, wherein the steel pressure vessel comprises a drawn-in center part and a re-expanding upper part with the latter containing the outer coil bundle and the heat exchanger. 6. A nuclear reactor plant according to claim 1, wherein circulating blowers are arranged under the steel pressure vessel. 7. A nuclear plant according to claim 1, wherein the steel pressure vessel has a drawn-in center part and the two circulating blowers are mounted laterally on the steel pressure vessel in an area of the drawn-in center part and shielded against the steel pressure vessel. 8. A nuclear reactor plant according to claim 5, further comprising on the upper part of the pressure vessel, between the decay heat exchanger and the outer coil bundle several connection fittings for inletting of the secondary helium mounted laterally, said fittings leading to a ring header which is connected by the lines with heater surface tubes of the outer coil bundle. 9. A nuclear reactor plant according to claim 8, further comprising a further ring header above the outer coil bundle provided for collecting the secondary helium, means for conducting the secondary helium connecting the ring header of the lines with heater surface tubes of the inner coil bundle. 10. A nuclear reactor plant according to claim 9, further comprising a tube arranged in the center of the inner coil bundle for return of the heated secondary helium, said tube being connected to the inner coil bundle by an outlet header under the inner coil bundle. 11. A nuclear reactor plant according to claim 4, further comprising on the upper part of the pressure vessel, between the decay heat exchanger and the outer coil bundle several connection fittings for inletting of the secondary helium mounted laterally, said fittings leading to a ring header which is connected by the lines with heater surface tubes of the outer coil bundle. 12. A nuclear reactor plant according to claim 11, further comprising a further ring header above the outer coil bundle provided for collecting the secondary helium, means for conducting the secondary helium the ring header connecting of the lines with heater surface tubes of the inner coil bundle. 13. A nuclear reactor plant according to claim 12, further comprising a tube is arranged in the center of the inner coil bundle for return of the heated secondary helium, said tube being connected to the inner coil bundle by an outlet header under the inner coil bundle. 14. A nuclear reactor plant according to claim 3, further comprising on the upper part of the pressure vessel, between the decay heat exchanger and the outer coil bundle connection fittings for inletting of the secondary helium mounted laterally, said fittings leading to a ring header which is connected by the lines with heater surface tubes of the outer coil bundle. 15. A nuclear reactor plant according to claim 14, further comprising a a further ring header above the outer coil bundle provided for collecting the secondary helium, means for conducting the secondary helium the ring header connecting with heater surface tubes of the inner coil bundle. 16. A nuclear reactor plant according to claim 15, further comprising a tube arranged in the center of the inner coil bundle for return of the heated secondary helium, said tube being connected to the inner coil bundle by an outlet header under the inner coil bundle. 17. A nuclear plant according to claim 2, wherein the two circulating blowers are mounted laterally on the steel pressure vessel in an area of the drawn-in center part and shielded against the steel pressure vessel. 18. A nuclear reactor plant according to claim 17, further comprising on the upper part of the pressure vessel, between the decay heat exchanger and the outer coil bundle several connection fittings for inletting of the secondary helium mounted laterally, said fittings leading to a ring header which is connected by the lines with heater surface tubes of the outer coil bundle. 19. A nuclear reactor plant according to claim 18, further comprising a tube arranged in the center of the inner coil bundle for return of the heated secondary helium, said tube being connected to the inner coil bundle by an outlet header under the inner coil bundle.