MA and LLFP Transmutation Performance Assessment in

the MYRRHA eXperimental ADS

P&T: 8th IEM, Las Vegas, Nevada, USA

November 9-11, 2004

E. Malambu, W. Haeck, V. Sobolev and H. Aït Abderrahim

SCK·CEN, Boeretang 200, Mol, Belgium

Contents

1. Introduction: MYRRHA-XADS

2. Typical core configuration for MA and LLFP transmutation studies

3. MA and LLFP targets loading

4. Computational tools

5. Geometrical model features

6. Target irradiation conditions

7. Preliminary results

8. Conclusions

1. Introduction

Since 1998, the Belgian nuclear research Centre, SCK·CEN, is developing the MYRRHA ADS project.

In 2004, SCK•CEN is finalizing the pre-design phase of MYRRHA.

In the framework of the EC FP6 IP-EUROTRANS project, SCK•CEN is willing to adapt the design options of MYRRHA to fit out the objectives of the ETD/XT-ADS project (experimental demonstration of the technological feasibility of Transmutation in an ADS).

2.Typical core configuration for MA and LLFP transmutation

studies

3. MA and LLFP targets composition

4. Computational tools

MCNPX 2.5.e code used to: Define the sub-critical core configuration such as:

Keff-value close to 0.95

Total power close 50 MWth

Calculate neutron fluxes and spectra at each burn-up step through the ALEPH code flowchart

Libraries: JEF2.2 (MCB) combined to LA150n for Pb, Bi and steel elements); LA150h for protons.

ALEPH code (coupling MCNPX and ORIGEN2.2) to carry out the MA evolution calculation

4. Computational tools (cont’d) ALEPH

MCNPX calculates the spectrum in cells to be burned in an arbitrary group structure

The spectra are used to calculate reaction rates outside MCNPX using data read directly from ENDF files

The updated library is used to calculate new material compositions and densities

This entire process is repeated until the entire burn up history is calculated

MCNPX

calculate multigroup spectra

ORIGEN 2.2

burn up calculation

ORIGEN LIBRARY

use data directly from ENDF files preprocessed by NJOY

99.90

NEW MCNP(X) INPUT

update densities and composition

5. Geometrical model features:MYRRHA MODEL for MCNPX

calculations

5. Geometrical model features (cont’d):Modelled details of various

assemblies

6. Irradiation conditions

Irradiation history: One-year operational period 3 cyclesCycle time-span 90 (EFP) daysShutdown between cycles 30 days

Neutron flux :Constant level assumed over 30 days sub-

cycles Cycle-and-volume averaged neutron flux

MA targets in channel A: 3.17·1015 n/cm²sMA targets in channel D: 2.78·1015 n/cm²s99Tc targets : 1.08·1015 n/cm²s

7. Preliminary results:Core physics static parameters

7. Preliminary results (cont’d)

Neutron spectra in MOX fuel and MA assemblies

7. Preliminary results (cont’d)Neutron spectrum in 99Tc target

7. Preliminary results (cont’d)99Tc incineration

Mass incinerated: 431 grams (1.75% of initial mass)

Burnout half-life (T1/2=Ln(2)/a ): 13.9 yrs vs T1/2 = 2.11 x 105 yrs for natural decay

99Tc

Irradiation history

7. Preliminary results (cont’d)

Mass evolution of Am, Pu and Cm in MA targets

7. Preliminary results (cont’d) Time-evolution of Am mass

7. Preliminary results (cont’d) Time-evolution of Pu mass

7. Preliminary results (cont’d) Time-evolution of Cm mass

8. CONCLUSIONS

The fast spectrum available in the MYRRHA sub-critical core is very efficient for the transmutation of (Pu, Am) targets due to a better fission-to-absorption ratio than in fast reactors

The incineration of Cm pre-requires a Partitioning step to separate Cm and Am

The incineration of long-lived fission products, such as the 99Tc, in a resonance capture region is demonstrated.

Further studies are underway to enhance the epithermal tail of the neutron spectrum by optimizing the target design and choosing more appropriate spectrum softening materials.