Heat Transfer Deterioration in Application to HPLWR-Mechanisms Identification and Ranking Table

• One of the major objectives of HPLWR Phase 2 project is to assess the feasibility ofthe super-critical water-cooled and moderated reactor. To this end it is necessary toevaluate the thermal performance and the distribution of temperature in the reactorcore under target operation conditions (25 MPa pressure and 280÷500 °C temperature).The critical scientific issue in this subject is to evaluate the efficiency of heattransfer in the reactor core and in particular, to determine the conditions of the occurrenceof the Heat Transfer Deterioration (HTD) phenomenon. The objective of this paperis to investigate and rank the key parameters that are governing the onset of HTDin general and in the HPLWR in particular. The paper describes the major heat transferdeterioration mechanisms and criteria, and contains evaluation of the importance ofparticular mechanisms on the onset of HTD. The major mechanisms are listed in a tableand ranked according to their estimated relative importance. It is concluded thateven though HTD has been investigated by many researchers and the world-wide experimentaldatabase counts tens of thousands of experimental points; still prediction ofthe onset of HTD is difficult and is subject to essential uncertainties. As a result, thereare many expressions for the onset of HTD available; however, they give very oftennon-consistent predictions. Thus more work is needed to develop a reliable HTD criterionthat can be used in nuclear applications. Operational conditions and complex geometryof HPLWR introduce additional uncertainties into the prediction of the onset ofHTD. Limited experiments in rod bundles and in parallel channels indicate a significantdeparture of the HTD conditions as compared to the experiments in single channels.Such factors as the bundle effect and the flow oscillation effect (in case of parallelchannels) have been noted and discussed.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

SRA - Energy

SRA - Energi

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