HZDR FLUKA activities in support of the MYRRHA Project Short summary with a focus on activation problems Anna Ferrari, Stefan Müller, Jörg Konheiser Helmholtz-Zentrum Dresden-Rossendorf

A look at the MYRRHA project Framework of this work: CDT-FASTEF + MAXSIMA EU FP7 projects Goal: design a FAst Spectrum Transmutation Experimental Facility, able to demonstrate efficient transmutation of high level waste and associated technology Heart of the MYRRHA facility at SCK·CEN in Mol FASTEF + The MYRRHA construction could start in few (?) years MAXSIMA design (planned to be operational in 2023) In MYRRHA (Multi-purpose hybrid research reactor for high-tech applications): A LFR (Lead Fast Reactor) will operate both in critical and subcritical mode. Core power - 100 MW in critical mode in the FASTEF design: - 94 MW in subcritical mode An Accelerator Driven System with a 600 MeV proton beam will be provided by a LINAC A Compact Spallation Target will be provided, in LBE (Lead Bismuth Eutectic)

The general shielding problem 600 MeV Proton beam-line Target window zone Beam spot centre movement Reactor Spallation target LINAC tunnel Beam Dump Casemate The general shielding problem up to 4 mA current Analysis around the accelerator in: A. Ferrari, J.-L. Biarrotte et al., SATIF-11 Conf. Proc., OECD/NEA Nuclear Science 7157, 13-27 (2013)

Goal: Neutronics, shielding and activation analysis in support of the safety Key points: - Detailed characterization of the shielding and of the activation problems around the accelerator and around the core in both subcritical/critical modes - Definition of the shielding structures in the building areas not yet optimized (ex. Cover, Vertical containment beyond the 90 magnet) - Find activation problems that can have an impact on the design Method for the reactor analysis: combined use MCNPX and FLUKA. - MCNPX is the official tool used to characterize the MYRRHA cores FLUKA allows to evaluate the dose rates due to the activated materials and with the real geometry

The CDT model of the reactor containment system (ANSALDO) Hot LBE (350) Argon AISI 316L Concrete with SS content Nitrogen

The new MAXSIMA model

Components included in the model for MAXSIMA: Reactor vessel Reactor diaphragm Reactor cover Above core structures (ACSs) Primary pumps Primary heat exchangers In-vessel fuel handling machines Window target Silicium doping

A comparison Argon/Nitrogen as plenum gas: residual radiation Analyzed irradiation pattern: Medium term operation  1 cycle 90 d continuous irradiation, 1 week cooling Argon Nitrogen H*(10) rate (Sv/h) H*(10) rate (Sv/h) Production of Ar-37 (t1/2= 35 d) by neutron capture from Ar-36 Production of C-14 (t1/2 = 5700 y) by fast neutron activation from N-14 Residual activity in argon:  26 Bq/cm3 Residual activity in nitrogen:  0.3 Bq/cm3

Activation of the T91 window (FLUKA simulation) RN contribution to the total specific activity [Bq/cm3]- EOI 15 y Neutron fluence rate (n/cm2 per s) T91 samples Specific activity [Bq/cm3] EOI 90 days cooling 1 week 5 years 30 days 15 years cooling 1 year Exit window 4.50E+12 1.73E+12 6.95E12 3.28E+12 7.88E+12 2.34E+12 Hexagonal tube (central part) 2.91E+11 1.29E11 5.95E11 3.74E+11 6.70E+11 2.89E+11

In the frame of the European Projects CDT and MAXSIMA we widely used FLUKA to cope with activation problems. In the reactor analysis, a coupling MCNPX/FLUKA allowed us to perform calculations around the reactor core, which had an impact on the design ANSALDO is a fundamental partner in the MYRRHA Project. We had a fruitful collaboration in CDT and MAXSIMA ANSALDO is now in charge of the activation calculations for the MYRRHA Project (and not only!) and joined the community of the FLUKA users