fuel performance: integrating cms with nnls enigma · fission product e.g. iodine makes crack tip...

Fuel Performance:Integrating CMS with NNLs ENIGMAA.S. DiGiovine, S. Tarves

A. Worrall, R. Gregg, (National Nuclear Laboratory, UK)

2010 Studsvik Light Water Reactor Seminar

Fukuoka, Japan June 9-11, 2010

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Outline

• Fuel Performance Issues

• CMS Capabilities

• ENIGMA (National Nuclear Lab, UK)

• ONUS - ENIGMA/CMS Integration

• Summary

June 2010 Studsvik Light Water Reactor Seminar

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What is the PCI Phenomenon?

• When power in a rod increases, becomes prone to PCI (pellet clad

interaction)– Induces “stress corrosion cracking” (SCC)

1. Power increase causes a differential thermal expansion in the clad

tensile stress in the cladding (“hoop stress”)

2. A certain power level is also necessary for fuel to fail indication

that high fuel temp. required and release of aggressive, volatile

fission product e.g. iodine makes crack tip brittle

3. Failure is not immediate suggests crack has to develop and

propagate have to be held at power for a period of time

• Power increases alone are insufficient– This has been proven by experimental results with very high increases in rod powers

Requires fuel performance code PLUS power history – look at

“concentrated hoop stress” and “crack length”


Stress

Corrosion

Cracking

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Fuel Performance Issues:

INPO PCI Initiative (SOER 07/004)

• Impose local power monitoring to avoid PCI

• Implement operational guidelines to avoid

operating practices that increase PCI

vulnerabilities


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Fuel Performance Basics


Fuel/Clad

Mechanics

PCMI

Determine

Power

Distribution

Fuel/Clad

Temperature

Distribution

Fission Gas

Release

ModelRadioactive Gap

Inventory

Failure

Probability Rod

Internal

Pressure

Input Data Define Geometry

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Fuel Performance Parameters of Interest

• Calculation against design and licensing criteria:

–fuel centreline temperature

–rod internal pressure

–clad stress

–clad strain

–rod growth

–clad fatigue and ratchetting


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Fuel Performance

Capabilities of NNL’s ENIGMA

• Thermo-mechanical fuel performance code

– stress and strain evolution in fuel and clad

– temperature evolution in fuel and clad

– stable and short-lived fission product release

• Applications

– fuel: UO2, MOX, Gd, IMF, Thorium, wafer fuel, ...

– clad: Zircaloy-2, Zircaloy-4, advanced alloys

– PWR, BWR and some test reactor conditions

• Validation– temperature, pressure, FGR, dimensional changes, corrosion, etc


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NNL’s Fuel Performance Capabilities:

ENIGMA• 527 rod irradiations currently included

• Test reactor irradiations

– Halden: 18 separate IFAs

– Risø: 1st, 2nd & 3rd fission gas projects

– Studsvik: Various ramp projects (e.g. Trans, Inter)

– BR3/BR2: Tribulation, GAIN, GAP, PRIMO

Callisto projects

– High Burnup Effects Program

– NFIR program

• Commercial reactor irradiations

– Various American and European PWR datasets


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ENIGMA Benchmarking – Number of

Irradiated Rods Modeled vs. Exposure


Exposure (GWd/t)

No. of

Rods

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Studsvik Capabilities :

Assessing Fuel Performance

• SIMULATE – PCI Extension Module– Account for fuel conditioning and deconditioning on a pin by pin basis

(not node, not “hot pin”)

• CMSOps – Reactivity Management and Operational

Support– Guidance to preclude PCI failures during power maneuvers

– Project planned power maneuvers (before actual maneuver occurs)

• GARDEL – Online Monitoring– Ensure compliance within PCI limits during operations

– Preclude PCI failures during power maneuvers


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ONUS – Computational Configuration


CMS Model

SIMULATE Pinfile

NEXUS: automated

ENIGMA input generation

NEXUS: executes/collates

ENIGMA results

Presentation of Pin-by-pin

ENIGMA results provided in

format governed by customer

•The “ONUS Cloud” features/benefits

• Hosted solution

• Controlled environment for QA

• Results presented via GUI

• No computational burden on end-user

• Entire analysis of all pins in the entire core takes

less than 10 minutes

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Benefits of a Hosted Solution

“Cloud Computing”

• Quick-Fix or Just-In-Time Services– Since Studsvik has access to the environment and model files, support

and services can be done quickly, meaning less down time for engineers

• User Flexibility– The software installations reside outside of your private network,

allowing users to access the system even when out of the office, without

having to go through your network

• High Availability– Hosted servers use the latest technology for built-in redundancy and

automatic failover to backup hardware, ensuring the system is highly

available


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ONUS Example – Clad Hoop Stress


• Indicates pins more

“susceptible” to PCI

• Shows bi-modal nature of clad

stress

• Coolant to clad pressure

• Pellet to clad pressure

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PWR PCI Operations Example

Near EOC Load Swing


PCI Allowed

Power

Actual Power

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ONUS Example – Rod Internal Pressure


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ONUS- Benefits of combining CMS with ENIGMA

• Eliminate uncertainties of approximate modelling, some examples:

– global ramp rates

– limiting pin (“hot-pin”)

– delta kW/ft

• Explicit pin-by-pin thermo-mechanical fuel performance analyses (detailed pin power history from CMS, fuel performance assessment from ENIGMA)

– evaluate fuel loading pattern prior to finalizing core design

– explicitly evaluate and monitor reactor operations and power maneuvers(before they actually occur)


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Summary

• Detailed (pin by pin) thermo-mechanical fuel performance

via ENIGMA analysis using CMS pin histories now

available– Hosted solution

• We are in the prototype stage, if you have interest to

have a trial evaluation of your fuel or core design please

let us know

Thank you for your attention!

References:1. “ONUS”: ON-line fUel performance Surveillance – Linking Studsvik’s CMS with UK NNL’s ENIGMA-B,” A. Worral (NNL) A.

DiGiovine (Studsvik), Advances in Nuclear Fuel Management IV (ANFM 2009) Hilton Head Island, South Carolina, USA, April

12-15, 2009, American Nuclear Society

2. “Highly Detailed PCI Evaluations of Actual Operating Power Maneuvers at Southern Nuclear,” A. DiGiovine, et. Al., 2010 LWR

Fuel Performance Meeting/TopFuel/WRFPM (TOPFUEL) Orlando, Florida, USA September 26-29, 2010 – to be published


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June 2010Studsvik Light Water Reactor

Seminar

fuel performance: integrating cms with nnls enigma · fission product e.g. iodine makes crack tip...

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