The ART-GCR Methods Technical Program Plan

William F. SkerjancResearch Scientist/Engineer

Gas-Cooled Reactor Program Review MeetingMay 8-9, 2018, at Idaho National Laboratory

Hans Gougar

ART-GCR National Technical Director

Plans Developed Under NGNP

• PLN-2804, Next Generation Nuclear Plant Steam Generator and

Intermediate Heat Exchanger Materials Research and Development Plan

• PLN-2497, Graphite Technology Development Plan

• PLN-2498, Revision 4, “Advanced Reactor Technologies High

Temperature Reactor Methods Technical Program Plan”

Last updated in 2016 (Gougar and Schultz)

Goals revised

• PLN-3636, Technical Program Plan for the ART-TDO/AGR Fuel

Development and Qualification Plan

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Objectives of the Plan

• To develop and demonstrate tools that can perform prototypical design and

licensing calculations with sufficient fidelity that residual and inherent

uncertainties in calculated safety and performance figures of merit (FOM) are

bounded and acceptable for the purpose of the simulation, and

• To conduct (or guide the design and execution of) experiments that yield a data

set that covers the anticipated operating envelope and are of sufficient quality

to validate computational models used for design and licensing of High

Temperature Reactors (HTRs) operating with reactor coolant outlet

temperatures between 650°C and 850°C. (Methods can be used with higher

temperatures but may require additional experiments to validate)

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Thermal Fluids Validation & Verification (Jim Wolf, Lead)

Experiment Matrix developed from the NGNP PIRT

• (Ball, S., et al., “Next Generation Nuclear Plant

Phenomena Identification and Ranking Tables

(PIRTs),” NUREG/CR-6944, 2008.) and INL/EXT-11-

21397, Assessment of NGNP Moisture Ingress

Event

• Assumed very high temperatures (up to 1000°C)

• Designed to address Phenomena considered to be

of highest importance but with limited knowledge

Lower Plenum mixing, Bypass flow, core heat

transfer, plenum-to-plenum heat transfer and

circulation, Air ingress, and (later) moisture ingress.

• Integral and associated separate effects and

fundamental experiments for validation of CFD and

System models4

Boundary Conditions

• NQA-1 standards for

experimental validation

A challenge to flow down to

NEUP projects

• RG 1.203 for model validation

CFD and system analyses

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Recent Updates

• Recent modifications to the plan

Focus on the minimal set of experiments needed to validate models of important scenarios: Normal ops, (likely to be

selected) Design Basis Events, and some Design Extension Conditions

Reactor vessel (cavity) cooling system performance (NSTF integral facility at ANL)

Shift the load to universities (NEUP)

• Integral Facility at Oregon State University

• Numerous separate/mixed effects experiment

• Priorities are being re-evaluated based upon

Knowledge gained from 10 years of testing, focus on the steam cycle

Vendor input

INL/EXT-17-43218, Schultz, et al, Identification and Characterization of Thermal Fluid Phenomena Associated with

Selected Operating/Accident Scenarios in Modular High Temperature Gas cooled Reactors”, under review 6

Scenarios Covered in the Experimental Matrix

• Normal Ops

Coolant flow and temp distributions (hot channels)

Mixing of jets in outlet plenum

• Loss of Forced Cooling – pressurized

Core heat transfer (conduction and radiation)

Coolant distribution under natural circulation

Vessel (cavity) cooling

• Loss of forced cooling – depressurized

All of the above plus air ingress

Reactor cavity gas distribution

• Steam generator tube break7

High Priority

• Complete modifications to the OSU High Temperature

Test Facility and resume matrix testing

• Demonstrate operation of the ANL Natural Circulation

Shutdown Heat Removal System with water-cooled

configuration, for studying reactor cavity cooling system

performance

• NEUP projects on moisture ingress, jet plume behavior

(in-core and from primary breaks) • Vendors participated in the design and test

matrix planning for the HTTR and NSTF

experiments.

• AREVA and X-Energy facilitated the

conversion of NSTF to a water-cooled

configuration.

• The NRC sponsored the design and

construction of HTTF8

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Schedule – 2010 plan versus status

Core Simulation (Gerhard Strydom, Lead)

• Development and demonstration of methods for simulating operational and transient scenarios that can be used for design and licensing

• Technical Scope

Coupled core neutronics and thermal fluids

Pebble bed and prismatic

Cross section generation

Uncertainty analyses

• Some synergy with NEAMS – especially in core thermal fluid analysis (PRONGHORN)

10The main objective is to identify the important physics to be captured and capabilities to be constructed (rather than to develop a code system that can be marketed or apply the latest computational techniques)

Activities

• Development (in part) driven by international benchmark activities and

collaborations (HTTR)

OECD-NEA: MHTGR-350 and HTTR LOFC projects

IAEA CRP on HTR-UAM

• Demonstrate basic and reproducible burnup and transient capabilities in

ways that can be adopted or emulated by vendors to use in their own code

systems (and better capture phenomena than the 1st generation HTGR

codes)

• Exploit developments in uncertainty analysis (e.g. SUSA, RAVEN,

TSUNAMI) to quantify sensitivities and to focus additional attention

11You will see more on these today.

Challenges to be Addressed

• Pebble bed reactors

Moving fuel

Undefined ‘assemblies’ (spectral zones) and the neutronic coupling between them

Radiative heat transfer between pebbles (and reflector), bypass flow in reflector

Cylindrical geometry

• Prismatic Reactors

Neutronic coupling between assemblies (blocks)

Burnable poisons, multiple fuel types (HTTR)

Streaming in control rod channels

Fidelity in thermal fluid analyses – a Goldilocks problem

Bypass flow 12RELAP5 model

CFD: This is accurate but

slow

This is fast but low resolution

Schedule: 2016 plan versus status

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?

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International Collaborations WP Lead

Hans.gougar@inl.gov

(208) 526-1314

art.inl.gov

Hans Gougar

International Collaboration WP in a nutshell