1. 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

2. 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 MW in critical mode
in the FASTEF design: 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)

3. 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)

4. 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

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

6. The new MAXSIMA model

7. 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

8. 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

9. 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

10. 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