vhtr methods r&d plan: overall perspective richard r. schultz, program manager very high...

VHTR Methods R&D Plan:

Overall Perspective

Richard R. Schultz, Program Manager

Very High Temperature Reactor Design Methods Development & Validation

Workshop: VHTR R&D Plan

Hosted by: Academic Center of Excellence for Thermal Fluids and Reactor Safety, Oregon State University

September 19-20, 2005

2VHTR R&D Plan Workshop Corvallis, OR September 19-20, 2005

Outline

• Background• Goals for VHTR• Needs: CFD and systems analysis software

development & validation• The Role of CFD & systems analysis software• Approach for achieving goals• Summary of experimental R&D• Summary of PIRT


Energy Bill

• Was recently passed by Congress & signed by President

• Calls for locating a prototype Very High Temperature Reactor (VHTR) at the INL.

• Specifies that a consortium of appropriate industrial partners will be organized that will carry out cost-shared research, development, design, and construction activities, and operate research facilities on behalf of Project (see Energy Bill—Section 643—Subtitle C: Next Generation Nuclear Plant Project).


Why at the Idaho National Laboratory?

• 52 nuclear test reactors

• First nuclear electricity to power a town

• 890 sq miles

• Lead Lab for Nuclear R&D


Energy Act…

• I’m not going to interpret anything in the Energy Act.• It is important to remember that although millions of dollars are

mentioned in Energy Act—we won’t have dollars unless they are appropriated.

• For your reference regarding “…enabling research, development, and demonstration activities on technologies and components for reactor and balance-of-plant design, engineering, safety analysis, and qualification” see Sec 643 pages 622 through 627.

• R&D will be done for both pebble-bed and prismatic reference designs [Phase II, in which a design competition between concepts will be held, will not begin until NERAC determines that the objectives of Phase I have been achieved (see Sec 643 item (c)(3)(D), page 627)].

• Appropriations—see pages 902 through 915.


The High Temperature Gas Reactor is Reference Design

• Utilize inherent characteristics– Helium coolant - inert, single phase– Refractory coated fuel - high temp

capability, low fission product release

– Graphite moderator - high temp stability, long response times

• Simple modular design:–Small unit rating per module–Low power density–Silo installation

• Passively safe design:–Annular core –Large negative temperature

coefficient–Passive decay heat removal –No powered reactor safety

systems

Reactor

Core Barrel Conditioning

SystemMaintenance Isolation/Shutdown Valve

Generator

Power Turbine

Recuperator

High Pressure Compressor

Low Pressure Compressor

Gearbox

Inter-Cooler

Core Conditioning System

Pre-Cooler

ReactorReactor


System


SystemMaintenance Isolation/Shutdown ValveMaintenance Isolation/Shutdown Valve

GeneratorGenerator

Power TurbinePower Turbine

RecuperatorRecuperator





GearboxGearbox

Inter-CoolerInter-Cooler



Pre-Cooler

Prismatic

Pebble-bed


Strengths & Weaknesses of Prismatic DesignRelative to Pebble-Bed—INL Perception

Strengths:• Larger fabrication, operating, & licensing experience base in US.• Flow paths are well known and relatively controllable due to fixed core

design; peak fuel temperature may be more predictable.• Placement of control rods in fuel region is easier.Weaknesses:• Larger excess reactivity, higher control worth, and relatively high

packing fractions required to get desired operating cycle length.• Must be shut down periodically for refueling and refueling is relatively

complicated.• Fuel at hot spots remains at same location relatively long time.• Relatively strong reactivity increase upon significant water ingress.

_______________Items in red font require methods R&D to demonstrate capability of tools.


Strengths & Weaknesses of Pebble-bed DesignRelative to Prismatic Design—INL Perception

Strengths:• Very little excess reactivity is needed—thus (a) reactivity insertion accident essentially

eliminated from consideration, (b) proliferation attempts easy to detect, and (c) significant reduction in reactivity insertion due to water ingress.

• Very effective fuel utilization.• Few reactor shutdowns required (no refueling outages).• Fuel enrichment is lower, easier to fabricate fuel pebbles, thus probably lower fuel costs.• Peak fuel temperatures will probably be lower.• Pebbles pass through high power region relatively rapidly—so fuel duty is milder and shared

among many more elements.

Weaknesses:• Likely to be more difficult to calculate flow and temperature variations.• More pebble withdraw tubes are needed for annular core than for a solid core; bridging and

stuck pebbles are a possibility.• Larger pressure drops across core (for 10 m high core). However, cross-flow design may

eliminate this issue.• Production of dust. AVR generated approximately 3 kg/year from control rod insertions, rubbing

of fuel pebbles, and drag of fuel pebbles on vessel.• Potentially may be more difficult to license.

_______________Items in red font require methods R&D to demonstrate capability of tools.


Region of System Operational Conditions Depressurized Conduction Cooldown

Pressurized Conduction Cooldown

Inlet Plenum IP1: Validation of CFD mixing calculation during transient.

Core CO1: Nuclear data measurements to reduce calculational uncertainty.CO2: Modification of cross-section generation code to treat low-energy resonances with upscattering.CO3: Development of improved method for computing Dancoff factors.CO4: Characterization of hot channel temperatures and fluid behavior at operational conditions.CO5: Validation using integral experimental data.

CD1: Validation of systems analysis codes to demonstrate capability to predict thermal behavior.CD2: Validation of models that calculate fission product release from fuel.CD3: Validation and calculation of air ingress and potential water ingress behavior into reactor vessel and core region.

CP1: Validation of systems analysis codes to demonstrate capability to predict thermal and hydraulic behavior.

Outlet Plenum PO1: Validation of CFD mixing using mixed index refraction (MIR) facility data & data available in literature. Perform calculation of fluid behavior with validated code.

PD1: Validation of CFD mixing during operational transients and effect on turbine operational characteristics. Perform calculation of fluid behavior.

PP1: Validation of CFD mixing during operational transients and effect on turbine operational characteristics. Perform calculation of fluid behavior.

RCCS RO1: Validation of natural convection characteristics in cavity at operational conditions.RO2: Characterization of natural convection characteristics in cavity at operational conditions.

RD1: Validation of heat transfer & convection cooling phenomena present in reactor cavity and via RCCS.

RP1: Validation of heat transfer & convection cooling phenomena present in reactor cavity and via RCCS.

Portion of R&D Need Matrix…


VHTR Objectives

• Demonstrate a full-scale prototype VHTR that is commercially licensed by the U.S. Nuclear Regulatory Commission

• Demonstrate safe and economical nuclear production of hydrogen and electricity


Goal: Design Methods Development & Validation

• Ensure the software tools are available to enable the VHTR to be designed and licensed to achieve Generation IV Program standards & objectives.


Effect of Goals on VHTR Software…• Because VHTR design goals are ambitious:

– High efficiencies

– High operating temperatures

– Exceptional safety margins

• And licensing the VHTR will be a challenge,

• Software tools for VHTR must have demonstrated capability and low calculational uncertainty


VHTR Design Methods Development & Validation

• For each plant, the R&D Process is based on…– Identifying the most

demanding scenarios for candidate plant design

– Isolating key phenomena in scenarios

– Determining whether analysis tools can be used to confidently analyze plant behavior scenarios (Validation)

– Performing R&D to upgrade analysis tools where needed

Scenario Identification: Operational and accident scenarios that require analysis are identified

PIRT: Important phenomena are identified for each scenario (Phenomena Identification & Ranking Tables)

Validation: Analysis tools are evaluated to determine whether important phenomena can be calculated

Development: If important phenomena

cannot be calculated by analysis tools, then further development is undertaken

Analysis: The operational and accident scenarios that require study are analyzed

No Yes Yes


The Calculation Process…

• Requires the analysis tools to have reasonable† agreement with data for key phenomena.

† Reasonable agreement: calculated value sometimes lies within data uncertainty band and shows same trends as data.

• Consists of seven steps • It’s assumed to be equally likely that the VHTR will be either

pebble-bed or block-type reactor

a. Material Cross Section Compilation and Evaluation

b. Preparation of Homogenized Cross Sections

c. Whole-Core Analysis (Diffusion or Transport), Detailed Heating Calculation, and Safety Parameter Determination

d. Thermal-Hydraulic and Thermal-Mechanical Evaluation of System Behavior

f. Fuel Behavior: Fission Gas Release Evaluation

g. Fission Gas Transport

e. Models for Balance of Plant Electrical Generation System and Hydrogen Production Plant

a. Material Cross Section Compilation and Evaluation

b. Preparation of Homogenized Cross Sections

c. Whole-Core Analysis (Diffusion or Transport), Detailed Heating Calculation, and Safety Parameter Determination

d. Thermal-Hydraulic and Thermal-Mechanical Evaluation of System Behavior

f. Fuel Behavior: Fission Gas Release Evaluation

g. Fission Gas Transport

e. Models for Balance of Plant Electrical Generation System and Hydrogen Production Plant


Includes Software such as:

Thermal-Fluids Experim ental Validation

Benchm arks(Prismatic)

NewComputational Fluid Dynam ics

Models

Thermal-Fluids Experim ental Validation

Benchm arks(Pebble Bed)

RELAP5 / FLUENT

CombinedReactorKineticsModule

NESTLEReactorKinetics

PEBBED (t)ReactorKinetics

PrismaticAssembly Spectrum

Code:DRAGO N

MCNP / MOCUP

(M onte Carlo)ORIGEN

NJOYBasic Cross Section

Processing

ENDF/BDatabase

New Cross Section Measurem entsPu, Pu, Pu240 241 242

DIF-3D /REBUS

PEBBED

Physics V&VBenchm arks

Physics V&VBenchm arks

Direct data flow

Validation

Data consistency requirement

0 4-G A 5 00 8 9-0 5

Coupled Fluid Dynam ics and Reactor Physics

Reactor Physics

Existing capability

Improvements needed

New capability developm ent required

DiscreteOrdinatesTransport:DECART

DiscreteOrdinatesTransport:

ATTILA

PARFUME

Fission Product

Transport Fuel & M aterialsBehavior and Fission Product Transport

a.

a.

b.b. b.

c. c.

f.

c. c.

g.

d. d, f.

d.

GRSACVerification

Benchm arks

MELCORVerification

Benchm arks

Pebble BedAssembly Spectrum

Code:COMBINE

b.

a.

b, c.

d. d. d.

c.

RadiationEffects


What exists: Thermal-Fluid Analysis…

– Partially validated systems analysis codes that cannot predict localized hot spots.

– Unvalidated computational fluid dynamics codes that will calculate the presence of hot spots—but the results cannot be trusted.

– Identification of only some of the important phenomena.

– Large incomplete validation data base.


Many of the Phenomena that Must Be Quantified & Analyzed Require CFD

• Forced convection: turbulent behavior and mixing• Mixed convection & free convection• Analysis of flow behavior in plena and chambers• Isolation of local hot spots a special need• Coupled calculations required: that is, calculations

that require coupled CFD codes and systems analysis codes (such as RELAP5) are quite important.


Thermal-Hydraulic Phenomena: CFD

• Normal operation at full or partial loads– Coolant flow and temperature distributions through

reactor core channels (“hot channel”)– Mixing of hot jets in the reactor core lower plenum

(“hot streaking”)• Loss of Flow Accident (LOFA or “pressurized

cooldown”)– Mixing of hot plumes in the reactor core upper plenum– Coolant flow and temperature distributions through

reactor core channels (natural circulation)– Rejection of heat by natural convection and thermal

radiation at the vessel outer surface• Loss of Coolant Accident (LOCA or

“depressurized cooldown”)– Prediction of reactor core depressurized cooldown -

conduction and thermal radiation– Rejection of heat by natural convection and thermal

radiation at the vessel outer surface


Role of CFD & Systems Analysis Codes

Relevance:• Key phenomena will greatly influence the material temperatures

at operational conditions and accident conditions.• Some validation data are available and are being used to

validate CFD & one-dimensional systems analysis codes.• Present focus is on maximum channel coolant exit temperature

at operational conditions and turbulent mixing in lower plenum.

Importance: The software must be shown capable of calculating the maximum material temperatures to enable the VHTR to be licensed. The calculational uncertainty must be acceptably low to demonstrate the VHTR achieves its design claims and is licensable.


CFD: Commercial vs. Non-Commercial…

• There are ongoing studies to evaluate non-commercial CFD codes.

• Commercial CFD codes are user-friendly and have an extensive V&V matrix. They can be used to analyze a wide variety of problems.

• Quite often, the opposite is true for non-commercial CFD codes since their development is often aimed at specific problems.

• However, non-commercial CFD codes are frequently state-of-the art and unexcelled in selected areas.


Approach for Achieving CFD Validation Objectives…

• The process begins by using what is available in commercial CFD codes and by using RANS.

• As deficiencies are identified in commercial CFD codes, the R&D path is chosen based on magnitude of deficiency.

• Use LES and DES as necessary

• Define development, including need for non-commercial codes, as required.


Example*: To Quantify Capabilities of Selected Commercial CFD Codes…

Standard Problem Committee—Committee formed by VHTR Program Group, consultants, and GIF Methods Project Board Members. Standard problems defined in accordance with phenomena identified in PIRT for design of interest.

Standard Problem Oversight Committee: Defines process for performing standard problem by exercise participants, evaluates results, and publishes results. Committee consists of CFD industry experts (some non-nuclear). Practices followed stem from CFD Committees of ASME Fluids Engineering Division and Nuclear Engineering Division best practice guidelines and used in ASME Journal of Fluids Engineering.

Standard Problem Participants: Participants perform standard problems using practices and procedures defined by Standard Problem Oversight Committee. Once completed, the results of the exercise are submitted to the Oversight Committee for evaluation.

Publish results of standard problems in ASME Journal of Fluids Engineering

Completed Standard Problem submitted to Oversight Committee

Standard Problem submitted to participants.

Set of Standard Problems defined by Committee submitted to Oversight Committee for distribution.

__________* Similar approach

proposed for systems analysis software


CFD Tool Certification: for Use in Gen IV

• Industrial quality standards recommended, e.g., ISO 9001:2000 standards or equivalent (for software quality, construction, and certification)—particularly for design calculations

• CFD certification should be based on V&V matrix that contains dominant phenomena for key Gen IV system scenarios

• CFD software V&V required for key phenomena identified in matrix. Acceptance based on degree of agreement with qualified data

• Extent of commercial and non-commercial CFD capabilities & need for further development/R&D can be demonstrated by specifying a series of International Standard Problems—with results published in journals.


Proposal: To Quantify Capabilities of Selected Commercial CFD Codes & Systems Analysis Codes…

1. Form PMB-sponsored committees with charter to define CFD code V&V matrix and systems analysis code V&V matrix based on Gen IV needs (the Standard Problem Committee).

2. Sponsor forums, similar to those hosted by Coordinating Group for Computational Fluid Dynamics (1993-4) or the Stanford Olympics (1968), to define International Standard Problems for CFD.

3. Publish results in journals.4. Use validation results as basis for achieving validation

objectives.5. In summary, base approach on that used by US Nuclear

Regulatory Commission when certifying their software tools to be used for reviewing the AP600 design for LWRs.


Analysis Practices Should be Well-Defined

For CFD software:• Suggest following policy defined by Journal of Fluids

Engineering (Vol 115, 1993)

• Benchmark study requirements: suggest following lead of: C. J. Freitas, “Perspective: Selected Benchmarks from Commercial CFD Codes,” Journal of Fluid Mechanics, 117, 1995, pp. 208 to 218.

For systems analysis software—use directly practices and procedures implemented by USNRC.


Summary: CFD Code Certification

• The CFD V&V matrix must be defined. • Proposed that:

– a series of CFD International Standard Problems be specified,

– commercial and non-commercial CFD organizations be solicited to participate in an ISP Forum

– the analyses be performed using rigorous standards

– the analyses be published in the literature.


The Punch Line

• Current software and methods are not ready to perform design and analysis to the standard that will be required by the VHTR–considerable validation, and probably development, are required.

• The above conclusion also applies to present software capabilities to perform VHTR licensing calculations.

• Practices and procedures acceptable to community must be defined and implemented.

This effort is critical to mission success.


For Validation Purposes: Some Data Sets Already Exist & Others Are Already Planned

Examples:

1. IAEA benchmark problems.

2. Integral facilities: HTTR, HTR-10

3. Various other experimental data recorded in GIF member experimental facilities

4. US DOE sponsored data: matched-index-of-refraction (INL) and NSTF (ANL)


Summary of INL Experimental R&D

• Ongoing R&D

• Plans


Objectives: Provide benchmark data for assessment and improvement of codes proposed for NGNP designs and safety studies andObtain better understanding of related phenomena, behavior and needs

Two emphases: Spatial variations in local fission rate and material behavior will cause "hot channels" which may cause "hot streaking" in lower plenum – and possible structural problemsStarted in August 2004

Thermal hydraulic benchmark experiments

A n n u la r sh ap ed A c tiv e C o re

O u te r S id e R e flec to r G rap h ite

C o re E x it H o t G as P len u m

G rap h ite C o re S u p p o rt C o lu m n s

S h u td o w n C o o lin g S y s tem M o d u le H o t D u c t

In su la tio n M o d u le

C ro ss Vesse l N ip p le

H o t D u c t S tru c tu ra l E lem en t

M e ta llic C o re S u p p o rt S tru c tu re

C o re In le t F lo w

C o re O u tle t F lo w

In su la tio n L ay e r fo r M e ta ll ic C o re S u p p o rt P la te

A d eq u a te?

M o d ify ?

Tu rb in e In le t"P a tte rn F a c to r"

Plan view of lower plenum forprismatic NGNP concept

0 4-G A 5 00 0 7-0 8

CL


Overview of INL experimental tasksScaling

Needs

Heated experimentconcepts

Isothermal lower plenum flow experiment concepts

• Design• Fabrication• Measurements• Documentation

• Design• Fabrication• Measurements• Documentation

Coolant channels Lower plenum

Selection of first heated experiment

Pebble bed

exits?

Other important geometriesSecond heated experiment


inTm,

D50

D30 wq

CFD predictions of Richards, Spall and McEligot [2004]Experiment of Shehata

and McEligot [1998]

Twall (K)

Effect of turbulence model in CFD codes ("hot channel")

Shehata

v f

Selection of an adequate turbulence model is critical for CFD predictions

Turbulencemodels

Run 618, turbulent, moderate q

w


“Hot channel” experiment

Vacuum vessel

Multi-sensorhot-wire probe

Thermocouples

Gas circulator

Flow meter

Traversing table

Powersupply

Pressuretransducer

Heat exchanger

Upflow ordownflow

Potential concept to obtain benchmarkdata for turbulence modeling –

low pressure to reduce buoyancy effects

Example of operating conditions for which code predictions are needed: non-dimensional heat flux

Tabulated benchmark data are available for these conditions

For normal operation• Coolant channels have dominant forced convection with slight property variation• Parameters for buoyancy, streamwise acceleration and heat flux are low relative to thresholds for importance• Benchmark data are available to assess correlations in systems codes

0 .0001

0 .001

0 .01

102

103

104

105

Re

q+

Fu llpow er

R educed

pow er

S ign ifican t

N eglig ib le

0 .0001

0 .001

0 .01

102

103

104

105

Re

q+

Neg

ligib

le


20c

c

DL

4j

s

DL

10jD

s

4.1jr

r

7pD

H jV

One typical conceptDesired: T (or C), V, v as fns{x,y,z}, Nu for surfaces, f or L, StrParameters: Geometry, Rep, Rej, Vj/Vp, Ri or a buoyancy parameter and Tj/Tp for heated jetsConditions: Normal, reduced power, transients

Dp

Dj/Dp 0.7

p/Dp 1.7

Preliminary scaling studies -- lower plenum ("hot streaking")

pV


Parameter ranges in normal full power operationGeometry: Posts under active core – pitch/D 1.7, height/D 7Plenum Reynolds number, Replenum 24,000 (away from outlet) 3x106 (near outlet) "Mixed flow" TurbulentJet-to-crossflow velocity ratio, (Vj/Vp) 50 (away from outlet) 0.6 (near outlet)

"penetrating" "bent"Qualitative flow visualization with dye injection [McCreery, 2004]

Lower plenum experiments

Model configuration Example of flow away from outlet

F low inlet

F lowoutlet

Posts


Potential experiment concepts for lower plenum flows

Purpose: assessment of momentum equation solution, scalar mixing and turbulence models for typical plenum geometry in limiting case of negligible buoyancy and constant properties

Measurements

Flow visualization

Particle imaging velocimeter – flow patterns, mean velocities, mixing of passive scalars

Laser Doppler velocimeter – time-resolved mean velocity components and turbulence quantities in flows

Possible flow paths in NGNP lower plenum

Conceptual model designs (plan view)


How does refractive-index-matching help?• Optical techniques avoid disturbing the flow to be measured• Typical approaches are LDV, PIV, PTV, flow visualization, PLIF, etc.

Laser Doppler Velocimetry Particle Image Velocimetry Snell’s Law

• Unless the refractive indices are matched, the view may be distorted or impossible even with "transparent" materials and position measurements may be incorrect

(Rod is resting on the bottom of the beaker)

(Marking is on back of beaker)

Not matched

Matched

Example of application of refractive-index-matching

Refractive index not matched

Plexiglas model

Fluid

Laser beam

Laser beam

Lasertransmissionoptics

Signalcollectionoptics

Internalplexiglasrods

Optical techniques will be used with models in our large Matched-Index of Refraction (MIR) flow system


Advantages– Versatile - basic/applied research, internal / external / coupled flows

– Non-intrusive, undistorted measurements of flow and transport

– -scale to building scale experience

– Good spatial and temporal resolution

– Benchmark measurements

Apparatus to study fluid physics phenomena in idealized SNF canister for EM Science project

(Rod is resting on the bottom of the beaker)

(Marking is on back of beaker)

Not matched

Matched

Example of application of refractive-index-matching

Benefits of INL MIR flow system• Refractive index-matching and optical measuring techniques allow flow measurements when

flow geometries are complicated• Most previous MIR experiments have been cm-scale; INL test section is about 0.6 m x 0.6 m x

2.5 m


Initial INL MIR experiment on lower plenum flow for assessment of CFD toolsSome desired features

• Represent generic features of flows near LP outlet (crossflow) and away from outlet (no crossflow)

• Well-defined geometry; ratios as in NGNP point design

• Turbulent flow in jet entry ducts

• Crossflow in "mixed flow" or "turbulent" regime [Zukauskas, 1972]

• Jet velocity ratio: ½ < (Vjet/Vplenum) < "large"

• Limited domain to ease initial CFD modeling

• Measurements concentrating in important regions– U, V, W, u, v , w , uv, etc. as function of x, y, z

– Flow visualization

– Mixing of passive scalars

– Inlet flow quantities for boundary conditions


Fabrication sketch of model

Dimensions:Dpost = 31.8 mm (1.25 in.), p/Dp = 1.7

Djet/Dp = 0.7, Hplenum/Dp = 6.85

Milestones/deliverables• Fabrication sketches

(for code developers)• Initial measurements

Proposed for later years*• Measurements and comparisons• Documented databases• Technical papers and reports

*Depending on funding from FY-06-07 US Gen IV program

Jet inlet ducts

Support posts

Sep 2005

Sep 2005

H

Flow


Example of comparable PIV data from INL MIR flow system(idealized SCWR coolant channels in US/Korea I-NERI project [2005])

Flow

Streamwise velocity field


Supporting PIV measurements by Prof. B.L. Smith at Utah State U.

x

y

1 5432Dp

LasersheetProfile location

Seeded

air flow

9.6/ ,

7.1)/(

in. 0.2 cm 08.5

DHlengthPost

Dp

DPIVDandp 2

000,56240 max

DVReZu

Geometry Measurements

Purpose = determine the minimum flow rate (Reynolds number) to achieve "mixed flow" in the crossflow of the INL lower plenum modelExperimental configuration


PIV measurements

"Raw" photograph Deduced contours of stream function, steady laminar flow

Re 400

Results include instantaneous and mean velocity fields, mean stream functions, Reynolds stresses and 2-D "turbulence kinetic energy"


Preliminary classification

• Steady laminar flow• Unsteady laminar flow• Mixed partially-turbulent flow• Mixed turbulent flow• Turbulent flow

Visualizations and tabulations on web site(www.mae.usu.edu/faculty/bsmith/EFDL/array/Array.html)

Re < 400

400 < Re < 510

600 < Re < 1,900

1,900 < Re < 56,000

Re > 2 x 105 [Zukauskas, 1972]


Potential experiment concept for heated flows in lower plenumObjective: assessment of codes predicting thermal mixing under influence of buoyancy for typical plenum geometry

Fluid: heated air or water with salt solution for density variation

Measure temperature field with miniature multi-sensor probes of Vukoslavcevic and Wallace [U. Maryland, NERI project] and possibly velocity and turbulence fields

O u tle tf lo w

C o ldg a s

C o ldg a s

C o ldg a s

H o tg a s

H o llo wce ra m ic o rP yre x cylin d e rs

S a p p h ire o rca lc iu m flu o rid ew in d o wT ra ve rsin g

h o t-w irep ro b e(ve lo c ity ,te m p e ra tu re )

T h e rm a l im a g in g ca m e ra(e x is tin g F lir ca m e ra )

Z

X

Possiblemodel


INL thermal-hydraulic experiments - plansFY-05• Complete fabrication sketches for MIR LP experiment• Complete fabrication and installation for first MIR LP experiment = jet inflow

without imposed crossflow (i.e., away from LP outlet)• Continue evaluation of experiment concepts for heated flows• Submit deliverable (fabrication sketches)• Initiate measurements with MIR LP experiments (milestone)

FY-06• Complete measurements for MIR LP experiment without crossflow; document• Design and cost system to provide crossflow in MIR LP model• Fabricate and install system to provide crossflow in MIR LP experiment• Initiate measurements with imposed crossflows• Complete fabrication sketches for second MIR LP experiment• Continue design and selection of experiments for

– Turbulence and stability data for vertical cooling channels– Heated flows in lower plenums

• Initiate design of MIR experiments on exit flows in pebble beds (if funding permits)


Other recommended INL experiments for code validation

1. Core heat transfer experiments

a. Turbulence and stability data from vertical cooling channels

b. Bypass flow studies

c. Exit flows in pebble beds

2. Upper and lower plenum fluid behavior experiments

a. Fluid dynamics of lower plenums

b. Heated flows in lower plenums

c. Interactions between hot plumes in an upper plenum and parallel flow instabilities

3. Air ingress experiments: heat transfer and pressure drop of mixtures of air and helium

4. Larger scale vessel experiments: to examine the behavior in the core, in the plenums and the interactions between them


VHTR - Scalability of the ANL Natural Convection Shutdown Heat Removal Test Facility (NSTF)

• Constructed CFD models of available RCCS designs and NSTF and performed accident condition analyses which showed strong 3-D effects and heat transfer differences with

existing 1-D correlations

• Identified major scaling parameters & phenomena and constructed a semi-analytical scaling model for air cooled RCCS

• Evaluated available RCCS designs, reviewed archival NSTF data, and identified needs for additional sets


R&D Plans are Based on a Preliminary Phenomena Identification & Ranking (PIRT)

• Based on prioritization of scenarios and phenomena :– Identified by experienced gas-cooled system designers– Engineering judgment

• Aimed at requirements for performing reasonable calculations of plant behavior for:– Operational conditions (rated power): neutronics and

working fluid behavior– Pressurized conduction cooldown transient scenario (PCCS)– Depressurized conduction cooldown transient scenario

(DCCS) including possible air/water ingress• Focus is on maintaining integrity of fuel, core, and reactor vessel.


PIRT: Components

• PIRT based on following components:

System Component Inlet Plenum Riser Upper Plenum and Components (e.g., Control Rod Assembly Surface Inside Vessel) Reflectors (Includes Bypass External to Core) Core(Includes Core Bypass Component) Fuel (Fuel Integrity)

Reactor Vessel*

Outlet Plenum and Components Hot Duct Annular Outlet (Hot) & Inlet (Cold) Pipe

Turbine Recuperator Precooler Low & High Pressure Compressor Intercooler

Power Conversion System (Direct Cycle)

Intermediate Heat Exchanger (IHX) Reactor Cavity Downcomers, Piping and Headers Air Cooler Chimney

Reactor Cavity Cooling System

Air Duct Shutdown Cooling System** Coolers


Example: Depressurized Conduction Cooldown Scenario has 3 Phases

1. Blow down (depressurization),

2. Molecular diffusion: following blowdown, there is not sufficient helium left in reactor vessel to have natural circulation—however, air from confinement moves into reactor vessel via diffusion. Heat removal dominated by radiation and conduction heat transfer.

3. Natural convection: Sufficient air has moved into reactor vessel via diffusion that natural circulation is initiated and convective cooling becomes an important ingredient.


Blowdown—Sample of Phase Description…

– Event initiated by rupture of largest system pipes– System depressurizes

– Helium working fluid discharged into volume that surrounds reactor

– “Rapid” heat-up of core occurs by the loss of forced convection

– Graphite dust from reactor core is transported to volume (the reactor confinement building) that contains reactor

– The confinement relief valves lift and gas is discharged to environment. Filters minimize distribution of dust to environment. Relief valves close when pressure has been reduced sufficiently.


Phenomena are ranked…

• High if important.

• Medium if phenomena may have supporting role in system behavior or may be important and thus should be carefully evaluated.

• Low if can be neglected.


A Sample PIRT Table (for core)…Phenomena

HPCC LPCC LC

1 2 1 2 3 1 2

flow distribution H H M H H H

heat transfer (forced convection) M M H H

heat transfer (mixed and free convection) M M M

pressure drop (forced convection) M H H H

pressure drop (mixed and free convection) M M M

thermal mixing and stratification H H H

jet discharge H H

thermal striping H H

bulk CO reaction M M

molecular diffusion H

Fluid properties (gas mixture) H H

Graphite oxidation (PBR) H H


Region of System

Operational Conditions Depressurized Conduction Cooldown

Pressurized Conduction Cooldown

Inlet Plenum IP1: Validation of CFD mixing calculation during transient & action of plumes on pressure heat boundary..

Core CO4: Characterization of hot channel temp and fluid behavior at operational conditions.

CD3: Validation and calculation of air ingress and potential water ingress behavior into reactor vessel and core region.

CP1: Validation of systems analysis codes to demonstrate capability to predict thermal and hydraulic behavior.

Outlet Plenum PO1: Validation of CFD mixing using mixed index refraction (MIR) facility data & data available in literature. Perform calculation of fluid behavior with validated code.

PD1: Validation of CFD mixing during operational transients and effect on turbine operational characteristics. Perform calculation of fluid behavior.

PP1: Validation of CFD mixing during operational transients and effect on turbine operational characteristics. Perform calculation of fluid behavior.

Reactor Cavity Cooling System

RO1: Validation of natural convection characteristics in cavity at operational conditions.RO2: Characterization of natural convection characteristics in cavity at operational conditions.

RD1: Validation of heat transfer & convection cooling phenomena present in reactor cavity and via RCCS.

RP1: Validation of heat transfer & convection cooling phenomena present in reactor cavity and via RCCS.

CFD Validations Required Based on PIRT…


Preliminary PIRT Being Used to Define CFD Related NGNP R&D…

• Most applications are at low Mach numbers—thus CFD techniques used for incompressible flows will be most used.

• A few applications for compressible, high-velocity CFD software are foreseen:– Perhaps blowdown– Pressure pulse propagation during turbomachinery

transients, e.g. compressor surges.


Conclusions—Methods R&D• Passage of Energy Bill has authorized the project for siting the

VHTR at INL, execution requires appropriations.

• Candidate VHTRs are both prismatic & pebble-bed designs.

• The VHTR will:

– Make possible the efficient and cost effective production of either or both electricity and hydrogen

– Excel in safety and reliability

– Discharge waste that is suitable for long term disposal

– Provide a bridge to a low-emissions economy based on water as our primary transportation fuel

• The current Generation IV/VHTR methods R&D is centered on ensuring the software tools are available to enable the VHTR to be designed and licensed to achieve Generation IV Program standards & objectives.

vhtr methods r&d plan: overall perspective richard r. schultz, program manager very high...

Documents

vhtr methods rd plan

nuclear rd slide

high temperature reactor

plant design

vhtr needs

safe design

design competition

high temperature gas