Unusual Concepts. Figure 1. The Operating Principles of the PIUS Pimary System

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1 European Nuclear Society e-news Issue 17 Summer Unusual Concepts Concepts of Nuclear Power Reactors NPS/KTH Seminar by Frigyes Reisch, SECURE and PIUS Innovative Power Reactor Designs with Passive Safety Features In Sweden an innovative reactor design was developed during the past decades. A reactor for district heating SECURE and a reactor for production of electricity PIUS (Process Inherent Ultimate Safety) SECURE and PIUS are innovative light water cooled reactors with passive safety systems in a large pool of borated water in a concrete pressure vessel, located underground. The irradiated fuel can be stored inside the reactor cavity for thirty years. These features make the concept actual for today s requirements. An electrically heated test loop was built where the basic design characteristics were successfully verified. The concept was analyzed through detailed calculations with different computer codes. Advances in Nuclear Science and Technology 1987 Figure 1. The Operating Principles of the PIUS Pimary System A. A heat source (nulcear core) placed in a vertical pipe in a water pool will cause an

2 upward flow in the pipe. B. If the heated water is returned to the lower end of the pipe there is no net flow from and to the pool. C. The heat generated can be extracted for a useful purpose. Mixing between hot circulated and cold pool water is prevented by stable stratification in tube bundles (density locks) D. By placing the pool in a closed vessel and pressuring with a steam bubble above the circulation system the latter can be operated at high pressure and temperature. Figure. 2 The operating principles of the SECURE primary system. Advances in Nuclear Science and Technology 1987

3 Figure 3. Heated Reactor Secure-H and Prestessed Concrete Vessel. Main Features of Nuclear Island. 400 MWth, 2 MPa, exit temperature 190 0C The ATLE test rig The Secure Heating Reactor

4 Figure 5. The ATLE test rig. National Heat Conference Portland, Oregon August 5-9, 1995 Fig 6. Schematic of the PLUS Reactor. Same as Nuclear Safety article, Fig. 1, LA-UR

5 PIUS Oak Ridge National Laboratory, September September

6 European Nuclear Society e-news Issue 17 Summer Underground reactors SECURE Värtan, Stockholm Teller LLNL (Lawrence Livermore National Laboratory) Fig. 1: The SECURE-H main cooling system (48) MARS: Krister Wickman tillsatte närförläggningsutredningen. Bakgrunden var att Stockholms elverk i juli 1968 sökt tillstånd för ett kärnkraftvärmeverk vid Värtan. Utredningen skulle ta fram ett underlag som underlättade myndigheternas ställningstaganden till tillståndsärenden av detta slag. Utredningen var i princip positiv till närförläggning. När betänkandet (Ref. 56) kom i juni 1974 var emellertid det politiska läget för kärnenergin ett annat än då utredningen tillsattes drygt fyra år tidigare. SOU 1974:56 The need for an investigation of safety questions arising in connection with the siting of nuclear power plants in and close to major population centres was brought into focus in The occasion was the application by the Electricity Supply Authority of Stockholm for permission to erect a nuclear combined power and district heating plant at Värtan which is located only a few kilometres from the central part of Stockholm. At that time, certain other projects involving nuclear combined heat and power plants on urban or near-urban sites were also being discussed.

7 Närförläggning av kärnkraftverk, SOU 1974:56 Fig. 2: REAKTOR DJUPFÖRLAGD I BERGRUM, TURBIN OVAN MARK I NORMALNIVA reactor in deep rock contaiment, turbine in above ground building at normal level in relation to water recipient Fig. 3: REAKTOR OCH TURBIN I DJUPFÖRLAGDA BERGRUM UNDER NORMAL NIVA reactor and turbine in deep rock containmemt and below normal level in relation to weater recipient Värtan, Stockholm

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10 European Nuclear Society, 2007