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Conference Article: Development and fabrication of a helium-heated steam reformer

Panknin, W.; Nowak, W. (L and C Steinmueller GmbH, Gummersbach (Germany))

Abstract

The development of a helium-heated steam reformer for the Prototype Plant Nuclear Process Heat (PNP) or for a High Temperature Reactor Module Plant must satisfy the specific requirements connected with nuclear components. Some of the main aspects will be mentioned: Because the steam reformer is part of the barrier between primary helium and secondary process gas, all parts of the primary closure must be accessible without opening the primary circuit, and in-service inspection should be possible. Leakage of the primary gas into the secondary circuit, due to the failure of component parts, must be impossible. This is accomplished by maintaining a slight pressure difference of 2 bar between the two circuits. Gas streaks in the primary helium with a temperature difference of about +- 20 K in comparison to the average gas temperature are expected to occur. The resultant effects must be considered and kept under control. The layout of the steam reformer must be designed against the impacts of external events such as seismic loads. The loss of the secondary heat sink ought not result in any major damage. The whole tube bundle must be replaceable. Replacement of the catalyst must be simple and fast. The design lifetime of the component is 140.000 hours. All these requirements are more stringent than those for conventional steam reformers or other comparable heat exchangers. Therefore, a new concept had to be worked out first, before beginning with the layout and design of the component. Here our main objective was, to separate those assemblies which are exposed to high in-service strains or high temperatures into structures of a simple geometry and to assign only one function to each element. A concept and a design were found with such a low stress level in all its relevant parts that the licensing procedure of the stress analysis is expected to be feasible. The steam reformer for PNP will have a heat transfer capacity of about 96 MW. The bundle will consist of roughly 300 tubes. In order to test the new concept and design experimentally, a steam reformer of smaller capacity (5 MW) with only 18 tubes was designed and is being fabricated at the moment. This bundle will be tested in the EVA II pilot plant at KFA Juelich. Because this bundle is comparable in almost all important details to the large steam reformer, the flow path and the design, as well as some interesting manufacturing steps will be explained with respect to this test steam reformer.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Specialists' meeting on heat exchanging components of gas-cooled reactors Duesseldorf (Germany) 16-19 Apr 1984
International Atomic Energy Agency, International Working Group on Gas-Cooled Reactors, Vienna (Austria)
IWGGCR--9, pp:288-301