Science and Technology of Nuclear Installations
Volume 2007 (2007), Article ID 41641, 9 pages
doi:10.1155/2007/41641
Research Article
Natural Circulation in the ATUCHA-I PHWR Nuclear Power Plant
1Nucleoeléctrica Argentina S.A., UG C.N. Atucha II, Lima 2806, Argentina
2Autoridad Regulatoria Nuclear, Av. del Libertador 8250, Buenos Aires 1429, Argentina
3DIMNP, University of Pisa, Via Diotisalvi 2, Pisa 56100, Italy
Received 9 January 2007; Accepted 17 May 2007
Recommended by Oleg Novoselsky
Abstract
A systematic study of natural circulation (NC) in a postulated, varying primary mass inventory
scenario at residual power fractions has been performed for a nuclear power plant operating in
Argentina. It is a pressurized heavy water reactor, cooled and moderated by heavy water. The analysis
seems particularly relevant at present, because a second nuclear power plant (NPP), of similar design
and nearly 745 MWe, is now under finalization. NRC-RELAP5/MOD3.3 was the code used to
perform the simulations. Results obtained are presented in the form of natural circulation flow maps.
The trends obtained fit in the expected limits for integral test facilities representative of PWRs. In
addition, the validity of a simplified analysis to scale single and two-phase core flow has been verified.
A set of constants has been obtained, which permits predicting NC core mass flow rate (CMFR) for
this NPP. Results are partially validated, for single-phase NC flow, using a documented plant transient,
showing reasonable agreement. Also, the effect of pressurizer size on the predicted evolution curve in
the NC flow map (NCFM) is discussed.