APPLICATION OF PACTITER V3.3 CODE TO THE ACPS ASSESSMENT OF ITER NEUTRAL BEAM INJECTORS PRIMARY HEAT TRANSFER SYSTEM Luigi Di Pace 1 , Dario Carloni 2 , Lorenzo Perna 3 , Sandro Paci 2 1 EURATOM/ENEA Fusion Association, via Enrico Fermi 45, Frascati, 00044 Italy, luigi.dipace@enea.it 2 Università di Pisa - Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, via Diotisalvi 2, Pisa, 56126 Italy, dario.carloni@iter.org; sandro.paci@unipi.it 3 Fusion for Energy, ITER Department, Safety Group, Josep Pla, 2 Torres Diagonal Litoral B3, Barcelona, 08019 Spain lorenzo.perna@f4e.europa.eu Activated Corrosion Products (ACPs) will be present in the various coolant loops of ITER: in-vessel and vacuum vessel, test blanket modules, auxiliary heating or diagnostic equipments. ACPs impact occupational exposure, routine effluents to the environment, and potential releases during accidents. Hence, the ACP inventory evaluation is an important task for ITER public and occupational safety. PACTITER v3.3 code is a computational tool derived from PACTOLE series of codes, modified in some modeling and computing capabilities. ITER Organization has included it as reference computer code for the ACP assessment. In the framework of its verification and validation activity, PACTITER v3.3 was used to assess the ACP inventory of the ITER Neutral Beam Injectors (NBIs) Primary Heat Transfer System (PHTS). This paper will document the preliminary results of this assessment, focusing on the impact of operation scenarios parameters (i.e. water chemistry, materials corrosion properties, etc.) and piping architecture. I. INTRODUCTION Neutron activation reactions will generate Activated Corrosion Products (ACPs) in ITER divertor, first wall/blanket (FW/BLK) and vacuum vessel (VV) cooling loops, as well as in any other auxiliary cooling systems, dedicated, as for example, to Test Blanket Modules (TBMs), Neutral Beam Injector or diagnostic equipments. Taking into account the experience gained in operating the fission nuclear power plants, where ACPs are responsible for about 90% of the Occupational Radiation Exposure (ORE) of personnel during inspections and maintenances 1 , the prediction and minimization of ACPs inventory has been recognized as an important factor in both the ITER safety approach and the licensing process. Computer code calculation of the ACPs inventory deposited onto the inner walls of the Primary Heat Transfer System (PHTS) cooling loops can provide an estimation of the resulting doses to personnel during the inspection and maintenance activities for both ORE assessment and ALARA processes (Refs. 2-3). Moreover, the ACPs inventory prediction in the PHTS cooling loops is needed for accidental analyses. For accidents not involving the in-vessel source terms, ACP may be the significant source term; e.g. for ex-vessel loss of coolant from first wall, divertor and Vacuum Vessel (Ref. 1). As documented in the Generic Site Safety Report (GSSR), (Ref. 4), and in the ITER Preliminary Safety Report (RPrS), (Ref. 5), the ITER Organization has included PACTITER as reference computer code for the prediction of the formation, activation, migration, deposition and removal of ACPs in the primary cooling loops. In the past the European fusion programs have defined safety related R&D for ITER and for future fusion plants. In this frame, EFDA and later on F4E, has co-financed Grant Agreements for the development of PACTITER computer code. The overall objective of the last Task Agreement launched in this field was the verification and validation of the PACTITER v3.3 code. As a side activity, it was foreseen an independent testing of the code, to be applied to an ITER PHTS cooling loop (Ref. 2). II. BRIEF DESCRIPTION OF PACTITER V3.3 PACTITER code derived from the PACTOLE series of codes developed by the CEA (Commissariat à l’Energie Atomique) for predicting ACPs in Pressurized Water Reactor (PWR) primary circuits. The main modifications done to PACTOLE for PACTITER are: - Addition of Cu element with the corresponding solubility data and nuclear reactions, as Cu alloys are used for ITER divertor plasma facing components (PFCs) and in some NBI components; - Extension of the property database to the lower coolant temperatures and different water chemistry of ITER compared to PWRs. FUSION SCIENCE AND TECHNOLOGY VOL. 60 AUG. 2011 835