Atucha II plant description

Atucha II is the third reactor built and operated in Argentina, following Atucha I and Embalse, and, notwithstanding Atucha I, the first of its kind in the world owing to its design, power, and other conditions as outlined hereafter. Therefore, one may start the story by outlining four main facts related to Atucha II: This is a natural uraniumfueled nuclear reactor [like a CANDU (CANadian Deuterium Uranium) reactor], vessel-equipped [like a PWR, that is (Pressurized Water Reactor)], and with safety features (namely, basic philosophy and protection and control systems) like those of the latest German PWRs. It has a positive coolant void reactivity coefficient (fission power tends to increase if coolant is removed from the core): except for one (standard) CANDU reactor built in China and CANDUtype reactors in India, this is currently the only reactor with such a feature after Chernobyl. Construction of the reactor, started at the end of the 1980s, was interrupted and finally restarted in 2006: all main components were stored at the site, but no industry Pressurized Heavy Water Reactors. DOI: https://doi.org/10.1016/B978-0-323-85382-8.00004-6 © 2022 Elsevier Inc. All rights reserved. representative (notably the designer who supplied the components) was available for planning or supervising the construction. The owner and operator of the plant, Nucleole´ctrica Argentina SA (NASA), created a single-purpose multidisciplinary team headed by Jose´ Luis Antu´nez (JLA) to undertake the completion of construction and the startup of Atucha II, and admirably the team completed the commissioning in due time. A system of the complexity of CANDU and PWR had to be built (in 2006) in a country with a long-standing history in nuclear technology and in which a competent regulator was ready to act based on the latest findings by the international community concerning nuclear safety technology. From the side of the utility, the intuition of JLA was that, above and beyond the need to install the various components, a deep understanding of the design principles of the reactor was needed. Accordingly, two international teams were created, the utility and the regulators, to consult with each other in relation to the critical issues of the system. To achieve this unprecedented and unrepeatable mission envisioned by JLA, the current authors directed a few dozen scientists (see acknowledgments) over a period of almost 10 years. Three chapters in this book form a suitable documentation of this unique nuclear power plant (NPP). Only a limited number of technical papers have appeared on topics related to Atucha II design and safety evaluation, namely: [A] Adorni M, Del Nevo A, D’Auria F, Mazzantini O, A procedure to address the fuel rod failures during LB-LOCA transient in Atucha-2 NPP. J Sci Technol Nucl Ins 2011;17; Article ID 929358. [B] Araneo D, Ferrara P, Moretti F, Rossi A, Latini A, D’Auria F, Mazzantini O, Integrated software environment for pressurized thermal shock analysis. J Sci Technol Nucl Ins 2011;17; Article ID 840734. [C] D’Auria F, Camargo C, Muellner N, Lanfredini M, Mazzantini O, The simulation of I & C in accident analyses of nuclear power plants. J Nucl Eng Design 2012;250;656663. [D] D’Auria F, Camargo C, Mazzantini O, The Best Estimate Plus Uncertainty (BEPU) approach in licensing of current nuclear reactors. J Nucl Eng Design 2012;248;317328. [E] Pecchia M, Parisi C, D’Auria F, Mazzantini O, Application of MCNP for predicting power excursion during LOCA in Atucha-2 PHWR. J Ann Nucl Energy 2015;85;271278. [F] Moretti F, Terzuoli F, D’Auria F, Mazzantini O, Instrumentation for full-scale boron injection test facility to support Atucha-2 NPP licensing. J Nucl Eng Design 2018;336;154162. [G] Mazzantini O, Galassi G, D’Auria F, The role of nuclear thermal hydraulics in the licensing of Atucha-II: the LBLOCA. In: Special issue trends and perspectives in nuclear thermal-hydraulics—to the memory of B. R. Sehgal, G. Yadigaroglu, and G. F. Hewitt [F. D’Auria (Ed.)], J Nucl Eng Design 354;127;paper 110292. [H] D’Auria F, Best Estimate Plus Uncertainty (BEPU): status and perspective. J. Nucl Eng Design 2019;352;paper 110190. [I] D’Auria F, Debrecin N, Glaeser H, The technological challenge for current generation nuclear reactors. J. Nucl Energy Technol (NUCET) 2019;5(3);183199. Papers [A], [B], [C], and [E] deal with nuclear fuel, pressurized thermal shock (PTS), instrumentation and control (I & C), and neutron physics modeling, respectively, which are integrated into the BEPU approach of Atucha II. Paper [F] deals with a scale-1 experiment performed to confirm the quality of the fast boron injection system of Atucha II: 2 Pressurized Heavy Water Reactors this is essential to mitigate the fission power excursion consequent to a loss of coolant accident. Paper [G] discusses a number of issues connected with the large break LOCA analysis for Atucha II. Finally, papers [D] and [H] provide a summary of the Atucha II Best Estimate Plus Uncertainty (BEPU) analysis, its key findings, and perspectives on BEPU (a topic covered in more detail in Chapter 2, The Atucha-2 BEPU). The purpose of the book is not to replicate the contents of those publications. The Best Estimate Plus Uncertainty constituted the key element in creating a connection between safety of existing reactors and advancements in nuclear science and technology, as emphasized in paper [I]. The three chapters in this volume devoted to the Atucha II cover: 1. A description of the Atucha II system and its technological complexity, with particular attention to the configuration of the moderator coolant loops and the fast boron injection system; 2. The BEPU approach pursued in licensing, particularly if we keep in mind that there was no original vendor-supported safety evaluation for the plant operation; 3. Selected results from Section 15 of the Final Safety Analysis Report (FSAR). In many respects it was a pioneering effort to calculate all transients required in FSAR by adopting the BEPU approach. Previous and current applications of BEPU in the licensing processes of various reactors use BEPU only for LBLOCA analysis; the importance of using BEPU for non-LOCA transients is discussed in detail here. 1