Nuclear Engineering and Design 230 (2004) 151–167 The design and safety features of the IRIS reactor Mario D. Carelli a,∗ , L.E. Conway a , L. Oriani a , B. Petrovi´ c a , C.V. Lombardi b , M.E. Ricotti b , A.C.O. Barroso c , J.M. Collado d , L. Cinotti e , N.E. Todreas f , D. Grgi´ c g , M.M. Moraes h , R.D. Boroughs i , H. Ninokata j , D.T. Ingersoll k , F. Oriolo l a Science and Technology Department, Westinghouse Electric Company, 1344 Beulah Road, Pittsburgh, PA 15235, USA b Politecnico di Milano, Italy c Comissão Nacional de Energia Nuclear (CNEN), Brazil d Equipos Nucleares S.A. (ENSA), Spain e Ansaldo Energia, Italy f Massachusetts Institute of Technology (MIT), USA g University of Zagreb, Croatia h Nuclebras Equipamentos Pesados S/A (NUCLEP), Brazil i Tennessee Valley Authority (TVA), USA j Tokyo Institute of Technology, Japan k Oak Ridge National Laboratory (ORNL), USA l Università di Pisa, Italy Received 8 May 2003; received in revised form 2 October 2003; accepted 13 November 2003 Abstract Salient features of the International Reactor Innovative and Secure (IRIS) are presented here. IRIS, an integral, modular, medium size (335 MWe) PWR, has been under development since the turn of the century by an international consortium led by Westinghouse and including over 20 organizations from nine countries. Described here are the features of the integral design which includes steam generators, pumps and pressurizer inside the vessel, together with the core, control rods, and neutron reflector/shield. A brief summary is provided of the IRIS approach to extended maintenance over a 48-month schedule. The unique IRIS safety-by-design approach is discussed, which, by eliminating accidents, at the design stage, or decreasing their consequences/probabilities when outright elimination is not possible, provides a very powerful first level of defense in depth. The safety-by-design allows a significant reduction and simplification of the passive safety systems, which are presented here, together with an assessment of the IRIS response to transients and postulated accidents. © 2004 Elsevier B.V. All rights reserved. 1. Introduction The IRIS plant conceptual design was completed in 2001 and the preliminary design is currently under- ∗ Corresponding author. Tel.: +1-412-256-1042; fax: +1-412-256-2444. E-mail address: carellmd@westinghouse.com (M.D. Carelli). way. The pre-application licensing process with NRC started in October 2002 and IRIS is one of the de- signs considered by US utilities as part of the Early Site Permit (ESP) process. Details of the IRIS design and supporting analyses have been previously reported and the reader is direc- ted to the listed references. Purpose of this article is to provide an overall review of the IRIS characteristics. 0029-5493/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nucengdes.2003.11.022