HTGR Knowledge Base

Conference Article: Passive heat removal experiments for an advanced HTR-module reactor pressure vessel and cavity design

Abstract

In the search for further reducing the residual risks of possible major reactor pressure vessel failure during and in the aftermath of severe accident of modular HTR's, an alternative RPV has been designed and a sample vessel already fabricated by the firm Siempelkamp, Krefeld, FRG. This alternative RPV design is made of high quality, ductile sphero cast iron with axial and circumferential wire prestressing or more recently also with circumferentially flat band prestressing. This specific Siempelkamp design has been tested and qualified in a series of experiments with the sample test vessel. This design was also used for the control gas vessel in the THTR under operational service conditions. In order to demonstrate reliable decay heat removal under most severe conditions, and 1:1 scale, 20 deg. sector of the vessel/cavity, termed INWA-facility (Inactive decay heat removal) was fabricated and tested at Siempelkamp. The cavity was cooled by natural circulation of water flowing in tubes embedded in the cast iron structure of the cavity. A total of 5 experiments were performed with this setup examining a variety of changes in constructive details, surface and cooling conditions. Each experiments was performed both for operational conditions and depressurization transients, typical for a 200 MW_th HTR-module. Experimental test durations ranged up to 1000 hours. Pre- and post-test predictions with the FEM-code TOPAZ accompanied the INWA test series.

This paper describes the INWA-facility and the experimental results as well as the predictive capability of the TOPAZ-code by comparing the data with computational results. The INWA-results qualify the pre-stressed cast iron vessel together with the natural circulation cooled cavity even for the worst of severe accident conditions. Even in the case of a total failure of all cooling capabilities in or at the cavity structure the vessel surface temperature remains below critical values.

view the full text of this article (8 pages, format: PDF, size= 952kB)

Reference:

Specialists meeting on decay heat removal and heat transfer under normal and accident conditions in gas cooled reactors. Juelich (Germany). 6-8 Jul 1992

International Atomic Energy Agency, Vienna (Austria)

IAEA-TECDOC--757, pp:139-146