Status of Attila for the Advanced Test Reactor (ATR) D. Scott Lucas INL

Discussion ATR Present ATR Neutronics Analysis Why Change? LDRD Status Results Plans Funding

Acknowledgements & Contributors Transpire, Inc., Allen Barnett, Todd Wareing, John McGee, Jim Morel Hans Gougar, Alan Schilk, Bruce Schnitzler Josh Peterson, Derek Hounshel Cristian Rabiti Jim Parry, George Griffiths ATR Staff Peter Cebull, HPC, S. Lucas Jr., HPC

ATR Largest materials test reactor (<250MWt) HEU in al matrix, plate fuel, water cooled, Be reflector Loaded with a mixture of new and recycled elements Not very symmetric, highly heterogeneous 9 flux traps, some with independent coolant loops Variable operating cycles (2-60 days) Positive void coefficient in loops

Description

Present ATR Analysis PDQ 2D XY R-Theta Neutron Diffusion 4 Energy Groups Fixed Mesh 1960’s Advanced Weighted Residual Collocation Method PDQ Approaching 40 Years of Age

National User Facility Use ATR for Tests, NGNP, GNEP, Westinghouse, AREVA, GE More up to date codes than PDQ, Monte Carlo, Deterministic Advanced Tests – Highly Enriched Fuels, More Complicated Geometries Both MCNP & Attila use SolidWorks Will be able to Exchange Models and Verify between MCNP & Attila

Solves the discrete ordinates (S n ) transport equation on a 3D unstructured finite element mesh Discontinuous Galerkin method for higher order flux and current solution (3 rd order accurate) Source Iteration with Diffusion Synthetic Acceleration For the Reactor Physicist…Attila FE mesh generated on a CAD model (Solidworks) Output amenable to visualization techniques (VisIt) Demonstrated on many platforms (~Opteron) Depletion module For the Core Safety Analyst…

Zeus Critical Assembly The Zeus critical assembly is located at Los Alamos National Laboratory Experiments have been performed to measure the reactivity worth of small samples of 233 U, high enriched U (HEU), Pu, and 237 Np The MCNP Monte Carlo code has been used to predict the reactivity of these samples, but was too time consuming to obtain statistically adequate results Attila has been used to predict the reactivity worth of these samples

ZEUS

0.08 ± ± 0.01Pu 0.02 ± ± Np 0.06 ± ± 0.01HEU 0.16 ± ± U Monte CarloAttilaExperimentSample

Attila Model – LDRD Status

INL LDRD Accomplishments 2D/3D CIC 94 Benchmarks Comparisons to Criticality Experiments MCNP, MCNPX Fresh Core Takeda Fast Reactor 1-4 Depletion Serial Parallel 5 Students Trained this summer on SW &Attila (Never Again)

Parallel (DMP) Test INL 623,000 Tet 3D Model 8 hours on locally parallel version – 2 cpus 16 hours on 1 cpu 1 hour 23 minutes on 16 Distributed Memory cpus at Transpire 15 Minutes on 64 CPU’s - ICESTORM Theoretically Linear up to 100 cpus

HPC procs walltime (min) walltime - slow

HPC

Yet Another Pretty Picture

XS Libraries Main Library = SCALE 27 Group, 22 Neutron Energy Groups, 5 Photon Groups AMPX Format, Attila conversion Tool SCALE 44 & 238 Group Library XS BakeOff NEWT Code – INL - Jim Parry to generate region specific XS Libs HELIOS – Studsvik – INL George Griffiths

Shim Sections – Five Degrees

Model for Heat Loads

XS Library Comparisons – CIC94

AFIF

Other Tasks Performed Script for changing material properties in input file done Placed angular sections in Be of Shim for reference points Run 2D/3D CIC 94 Comparisons with 19 plate fuel Use 2D/3D Models with 19 plate fuel for Core Wide Flux Maps Comparing to earlier CIC configurations Comparing to Flux Map reports Updating Neutronics Reqt’s per PDQ & CSAP CRADA Proposal

CIC Data Comparisons

19 Plate Fuel for 2D/3D Being placed in Rx Model and meshed

Attila Work Four Year Project 0.5 Million for Balance of Fiscal Year Possible Attila Calculations Excessive reactivity at startup with everything inserted Excessive reactivity at end of cycle 50/50 60/40 70/30 for 0 3, 17 and 38 days Relative axial power peak for three different scenarios Relative fuel peak power for the three scenarios Shim rod reactivates Regulating rod reactivity Safety rod reactivity OSCC reactivates 80/20 power

Amount of Boron burned through cycle Change in reactivity from the burn of boron Take into consideration reflector poisoning Fuel temperature coefficient Moderator temperature coefficient (BOC) (EOC) Power coefficient Delayed neutron fraction Safety rod worth Stuck safety rod worth Neck shim worth Burnable poison (BOC)

Change in reactivity associated with flooding of different loops for the 50/50 60/40 and 70/30 cases Thermal and Fast neutron flux (>1MeV) in multiple locations including OS I holes and drop tube Consumption and buildup of U and Pu isotopes Boron worth as a function of burnup Power in the 40 fuel elements for the 50/50 60/40 70/30 at (BOC) and (EOC) Reactivity for a depleted and new regulating rod

Summary Sectional Hf in Shims done, gives good results 19 Plate Fuel has been meshed, runs in process Beta - Parallel Attila Tested and running 2D/3D Models Parallel Burnup in progress Need to eventually define reqt’s for T/H and Fluids to interface with Attila for Heat Loads Harvesting LDRD Funds Generate XS Comparison between NEWT/HELIOS Burn Library CIC 94 Complete Cycle with Burn