fuel performance: integrating cms with nnls enigma · • hosted solution available references: 1....

Fuel Performance:Integrating CMS with NNLs ENIGMAA.S. DiGiovine, S. TarvesA. Worrall, R. Gregg, (National Nuclear Laboratory, UK)

2010 US Users Group MeetingOmaha, NE May 24-26, 2010

Outline

• Fuel Performance Issues

• CMS Capabilities

• ENIGMA (National Nuclear Lab, UK)

• ONUS - ENIGMA/CMS Integration

• Summary

May 2010 US Users Group Meeting - OPPD

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


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


Fuel Performance Basics


Fuel/Clad Mechanics

PCMI

Determine Power

Distribution

Fuel/Clad Temperature Distribution

Fission Gas Release Model

Radioactive Gap Inventory

Failure Probability Rod

Internal Pressure

Input Data Define Geometry

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


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


Fuel PerformanceCapabilities 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


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


ENIGMA Benchmarking – Number of Irradiated Rods Modeled vs. Exposure


Exposure (GWd/t)

No.

of R

ods

Whole Core Fuel Performance Applications

• Used by core designer to perform preliminary fuel performance assessment quickly

• Example: assess fuel performance of MOX fuel in an AP1000 and Sizewell B

• High rod internal pressures alleviated through various design and operational changes

• annular fuel, longer plenum volume


Rod Internal Pressure:MOX zoning surrounding guide

tubes

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

ONUS Example – Rod Internal Pressure


PWR PCI Operations ExampleNear EOC Load Swing


PCI Allowed Power

Actual Power

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

ONUS- Benefits of combining CMS with ENIGMA

• Eliminate uncertainties associated with approximation models

– E.g., limiting pin, bounding history– E.g., LHGR ramp rates– E.g. ,“snap-shot” of ∆kW/ft

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

– Explicitly evaluate and monitor power operations/maneuvers (and projections before they actually occur)

– Taking account of history of the fuel e.g. closure of pellet-clad gap, reduction in thermal conductivity, etc.


Summary

• Detailed (pin by pin) thermo-mechanical fuel performance via ENIGMA analysis using CMS pin histories now available

• Applicable in core design phase, and during plant operation

• Hosted solution available

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


May 2010US Users Group Meeting -OPPD

fuel performance: integrating cms with nnls enigma · • hosted solution available references: 1....

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