Technical Summary ofPHYSOR2014
IAkio Yamamoto
Technical Program Chair1

We still have many open problems
in reactor physics
 Many excellent advances in the reactor

physics field have been presented inPHYSOR2014.
 Also, many unresolved issues arerecognized throughout the conference.
 These “issues to be addressed by thereactor physics community” aresummarized.
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Reactor Analysis Methods
 Good reference solutions particularly for coupledphysics problems.
 Good, plant-level, non-proprietary measured
data for validation.
 Efficiency of full-core pin-by-pin methods forbroader use of this type of method.
 Accurate prediction of pin powers for challenging
situations (e.g. MOX/UO2 core) with industry
level production codes3

Reactor Analysis Methods
 Homogenization method in various types ofreactors – non LWR reactors, especially for
HTGR.
 Efficient treatment method for geometricaldeformation or distortion of core/fuel Application of the reduced order modelling tomore practical problems, e.g., issues related tocommercial reactors.
 Cross section uncertainties of iron for pressure
vessel fluence calculations
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Reactor Analysis Methods
 Efficient computing methods for the current andnext generation computers consideringarchitecture of CPU, e.g., memory bandwidth,
cache structure Generation of optimized energy structure forpractical core analysis codes
 Fidelity of discontinuity factor in highly
heterogeneous cores and its
correction/adjustment methods
5Deterministic Transport Theory
 Direct 3D MOC calculation is still impractical forcommercial reactor analysis
 Treatment of axial angular flux distribution in
1D/2D or 2D/3D coupling transport methods
 Higher parallel efficiency with CMFDacceleration
 Unified interpretation/discussion ofadvantages/disadvantages of CMFD based
acceleration methods for various applications.
6Monte Carlo Methods
 Convergence and the correlation of local tally Efficient (high efficiency, reduced memory)

sensitivity/uncertainty evaluation methods basedon continuous energy MC
 Treatment of random distribution of particles withvarious shapes/sizes
 Instability of MC based multi-physics
calculations due to statistical deviation
 Multi-group cross sections generation andimpact of their uncertainties on core7characteristics

Verification, Validation andUncertainty Analysis
 Full 3-D high fidelity deterministic simulations of"unconventional" systems (research reactors,prototypes, etc.) considering strong axial
heterogeneities
 Development of sensitivity analysis tools forvarious types of core as practical design tools.
 Inconsistency of predicted and measured
uncertainties of pin-power distribution in criticalexperiments.
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Verification, Validation andUncertainty Analysis
 UQ not only for XSs, but also for otherparameters – geometry, FP yields, TH conditionsin actual reactors Fidelity of UQ results obtained by the random
sampling method
 Quantification of uncertainties in calculation
modeling, adequacy of XS adjustment including
modeling errors.

9Verification, Validation andUncertainty Analysis
 Reduction of Pu238 cross section uncertainty for

ADS analysis – some experiments would benecessary.
 New data covariance for branching ratio ofAm241 and Pu238(n,fission) Uncertainties on individual fission yield andcumulative fission yield need to be improved andexpanded to include more isotopes
 Covariance data for many reactions need to beavailable on a more "refined" energy mesh10

Nuclear Criticality Safety Reasonable criticality calculation model of fueldebris (in Fukushima Daiichi damaged core) Full core Monte Carlo calculation with pin/pelletlevel burnup Uncertainty Quantification due to input
parameters and analytical modeling to enhance
the reliability for spent fuel criticality accident
analysis V&V for gamma transport calculations during
criticality accident
11Reactor Physics Experiments
 Large discrepancy between the measured andpredicted isotopic inventories in PIE analysis
 Critical experiments for accident tolerant fuel,such as U3Si2 with new cladding Incorporation of resonance scattering model for
ultra-fine group calculation methods
 Further compilation of experimental data forintermediate spectrum systems
 Measurement of sub-criticality is still achallenging and rich topic of ongoing.
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Reactor Concepts and Designs
 Accurate modeling of systems
 Benefits of flexible design (in terms ofbreeding ratio or other characteristics),
achieving long life core
 Overarching approach to guarantee safe
behavior through appropriate feedback
design and other approaches.

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Reactor Operation, Transientand Safety Analysis
 Actual plant measurement data for theverification of transient calculations
 Uncertainty estimation considering materialproperties and thermal-hydraulics
 Extensive validation framework considering
multi-physics effect, numerical comparison
among various codes14

Nuclear Data
 Adequacy of delayed neutron fraction andS(,) data Wider communications and feedbacks
between reactor physics and nuclear data
 Significant difference still exists amongmajor nuclear data files, JENDL, JEFF,ENDF/B

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Research Reactors andSpallation Sources Accurate estimation of kinetic parameters with

fixed source of ADS.
 Deeper analysis/understanding for spatial
dependence of detector position on themeasurement of subcritical kinetic parameters(e.g. neutron generation time, sub-criticality
level, delayed neutron fraction)

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Fuel Cycle and ActinideManagement
 Mechanistic multi-physics modeling of fuelperformance (including reactor physics) for
novel fuels include Th oxide fuel
 Discussion on the potential role (burner orbreeder) of ADS depending on the objectives ofthe fuel cycle strategy
 Integral experimental validation for crosssections of Th-232, U-233, Pa.

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Radiation Applications andNuclear Safeguards
 Use of exotic particle (e.g., anti-neutrino)

detection for non-proliferation purpose
 Efficient simulation of cross correlation
measurements using Monte-Carlo method18

Education in Reactor Physics
 Gap between up-to-date industrial

methods and reactor physics theory
learned during university lectures
 Modular, web-based, up-to-date
educational materials
 Incorporation of real radiation measuring
techniques and nuclear reactor
experiments
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Research related to Fukushima
Accident
 Criticality calculation for damaged fuel assembly

due to accident – geometrical deformation,
treatment volatile fission products, etc.
 Criticality calculations under extremely low
moderation condition in fuel racks
 Measurement of actual fuel debris composition
for intermediate fuel storage – use gamma
spectroscopy.

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Molten Salt Reactors
 Deeper understanding of why the traditional

derivation of reactor kinetic approximations,notable that of the point kinetic approximations,does not work in MSR.
 A benchmark for MSR including depletion.
 Flux monitoring and establishing of safety
criteria should be provided

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Reactor Physics and Criticality Safety
Activities in OECD/NEA Working Party The uncertainty due to nuclear data issignificantly larger than the measurement
uncertainty.
 Some noticeable discrepancies between the keffective were observed in sodium cooled fast
reactor neutronic benchmark

22Hybrid Particle Transport Methods for
Solving Complex Problems in Real-time
 A new benchmark suite for 3D,

heterogeneous whole reactor core ofvarious types

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Advanced Geometry Processing in
Deterministic and Monte Carlo Methods
 Efficient determination of regions duringtransport calculation on a neutron pathline, especially in large and complicatedgeometry
 Efficient access to cross section data fornumerous number of flat flux/materialregions
 Default standard geometry processing
system24

Multiscale, Multiphysics Approaches in
Nuclear Science and Engineering
Applications
 “True” multi-physics calculation with tightand nonlinear coupling of difference
physics calculations is still on-going UQ method for multi-physics calculation

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Reactor Physics of NonTraditional LWR Fuel Design Attract young students through experience ofadvanced fuel design, which significantly
increases tolerance for severe accident
 Significant uncertainty related to novel fuelperformance under irradiation, incomplete
knowledge of all relevant properties.
 Economics of novel fuels The licensing process and path to deployment ofnovel fuel forms
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Technical summary Many problems still need to beaddressed…
 Progresses will be presented in the next
PHYSOR2016 meeting!

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