status of fuel engineering activities on extended burnup …€¦ · · 2014-04-08status of fuel...

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CNEA - Fuel Engineering Department

Status of Fuel Engineering Activities on Extended Burnup

Fuel for the Argentine Fleet of PHWR’S

Technical Meeting on High Burnup Fuel Experience and Economics

Buenos Aires, Argentina; 26 - 29 November 2013

A. Bussolini, J. Valesi, L. Alvarez

CNEA - Fuel Engineering Department

[email protected]

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Technical Meeting on High Burnup Fuel Experience and Economics - Buenos Aires, Argentina; 26 - 29 November 2013 CNEA - Fuel Engineering Department

• Nuclear Power in Argentina

• Atucha-2 and Atucha-1 Fuels description

• Extended burnup in PHWR

• SEU Program in Atucha-1

Objectives and advantages

Fuel design criteria

Fuel design verifications

Fuel design modifications

In pile performance

• Other projects to increase fuel burnup

• Final remarks

Content

• Embalse (CNE) CANDU-6

• Atucha-1 (CNA-1) Siemens/KWU PHWR

• Atucha-2 (CNA-2) Siemens/KWU PHWR

• almost completed

• fuel assemblies have already been loaded

• commissioning phase is in an advanced stage

Nuclear Power in Argentina

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Embalse (CNE)

Atucha-1 (CNA-1)

Atucha-2 (CNA-2)

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General Operating Conditions CNA-2 CNA-1

(SEU) CNE Unit

Thermal reactor power 2160 1179 2109 MWth

Net electric power 692 335 600 MWe

Containment type pressure vessel pressure

tubes -

Average specific fuel rod power 232.8 232.0 246.0 W/cm

Fuel burn-up at equilibrium 7500 11400 7350 MWd/tU

Number of fuel assemblies in the core 451 253 4560 -

Number of fuel channels vertical horizontal

- 451 253 380

Refueling on power -

Primary system pressure 115.0 112.8 112 bar

Coolant and moderator D2O - 5



Atucha-2 Nuclear Power Plant

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Control rods

Fuel channels

Atucha-2 pressure vessel

Top view

Atucha-2 Nuclear Power Plant

Refueling machine

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Embalse Nuclear Power Plant

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Organizations in Nuclear Fuels Activities

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CNA-2 fuel assembly

Fuel assembly parameters

Number of fuel rods 37

Outside diameter 107.8 mm

Number of spacer grids 13

Coupling

Zircaloy-4 Spacer Grid (12)

Tie Plate

Linking Rods

and Tubes

Fuel Rods

Inconel 718 Spacer Grid (1)

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CNA-1 fuel assembly

Fuel assembly parameters

Length 6028.5 mm

Number of fuel rods 36 + 1 structural rod

Outside diameter 102.77 mm

Number of spacer grids 16 (15 rigid Zry-4 and 1 elastic Inconel 718) 11


CNA-1 spacer grids and structural components details

rigid spacer grid

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FA bottom view

structural tube

elastic shoes

Fuel rod parameters

Cladding material Zircaloy-4

Fuel column length 5300 mm

Fuel rod length 5566.4 mm

CNA-2 and CNA-1 fuel rod internals

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Fuel Rod Length = 5566.4

Active Length = 5300

CNA-2 and CNA-1 FA final assembling station

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Extended burnup in PHWR

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average burnup [MWd/tU]

target burnup

[MWd/tU]

15,000 - 25,000

50,000 7,000

60,000 - 80,000

PWR PHWR

+ 20% - 60% + 115% - 250%

increase fuel

burnup to

high or

ultrahigh

levels

SEU Program in Atucha-1

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Step by Step Approach

CNA-1 Start Operation 1974

SEU program starts,1993

Introduction of first SEU fuels,1995

Full core loaded with SEU fuels, 2001

Phase 1: not exceeding 12 SEU FA

Phase 2: from 12 to 99 SEU FA

Phase 3: from 100 to full SEU core

SEU: objectives and advantages

• Extension of fuel discharge burnup.

• Decrease of the fuel cost impact on the total electricity cost.

• Uranium resources savings.

• Spent fuel volume decreases.

Main benefits (SEU in comparison with NU)

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• Extension of fuel residence time.

• Reduction of FA consumption

• Reduction of frequency of refueling and on power fuel shuffling

Less utilization of the fuelling machine.

• Reduction of fresh fuel stock and fuel transports.

• Impact on spent fuel storage pool capacity.

Other beneficial consequences

SEU Fuel Design criteria

• Maintain the fuel ability to operate reliably to the proposed extended burnups.

• Avoid the introduction of new power operation restrictions.

• Maintain the margins of safe operation of the reactor.

Main design guidelines for SEU FA

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• Discharge Burnup.

• Residence time.

• Local burnup at the time of fuel reshuffling (power ramps).

• Maximum burnup at high power.

Main fuel operating parameters affected

Design verifications

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• Fission gas release internal gas pressure.

• Fuel cladding creep down and sheath strain.

• Relative length changes between the fuel stack and the cladding.

• Relative length changes between fuel rods

• Fuel cladding axial growing.

• FA structural integrity

• fuel rods and spacer grids interactions

• elastic sliding shoes and coolant channel interactions

• Power ramp behavior restrictions depending local burnup to prevent PCI

• Waterside corrosion and deuterium uptake.

• higher burnup

• increase in the residence time

Fuel design modifications

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• Plenum length was increased

more volume for gas release.

• Bearing pads with longer contact surfaces

interaction between spacers and fuel rods (whole irradiation).

• The ductility of the cladding material was increased

reduce the fuel rod susceptibility to PCI failure on power ramps.

• Inconel-718 replaced elastic sliding shoes material (SS A286)

compensate the higher stress relaxation.

Optimize to new SEU operating conditions

Design and in pile performance

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• The maximum local burnup, close to 15,000 MWd/tU.

• The dwelling time, from 300 to 500 fpd, almost doubling the original value for

natural uranium.

• The reduction of spent fuel volume, about 42 %.

The reduction on the cost of the fuel included in the cost of the electricity is

around 30% to 40 %.

Natural U SEU (0.85 w% U235)

Average discharge burnup [MWd/kgU] 5.9 11.3

Average refuelling frequency [FA/efpd] 1.31 0.7

Quantity of FA/year [FL • 85 %] 396 208

Design and in pile performance

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2010 2011 2012

Number of Fuels Discharged 248 213 219

Number of Fuel Assemblies with leaking Fuel Rods 4 0 0

Average Fuel Discharge Burnup [MWd/tU] 10563 10649 10696

• Poolside visual inspection

CNA-1 SEU fuel rod axial

growing (%) measurements

at different local burnups.

Other projects to increase fuel burnup

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• A feasibility study was performed by NASA, AECL and CNEA

• Proposed enrichment 0.9% U-235

14 MWd/kgU

Estimated fuel savings

around 20 %

CNE SEU Fuel Program

Other projects to increase fuel burnup

Utilization of SEU fuel in CNA-2

• CNA-1 and CNA-2 NPP and FA similarities

• results obtained with the SEU in CNA-1 since 1995

• extensive experience acquired in this process

preliminary fuel engineering feasibility of a similar

SEU program at CNA-2 has been evaluated

first stage target: 0.85% U-235

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FINAL REMARKS

• Burnup extension by using SEU Fuels has proved to be a useful way to

preserve the competitiveness of the Nuclear Generation of Electricity.

• Complete Fuel program was performed in Argentina to introduce SEU

0.85% U-235 in Atucha-1 reactor with excellent results.

• This program had negligible impact on Fuel Fabrication and on Reactor

Operation.

• Minor Fuel Design Changes were introduced to improve the performance

of the fuels.

• Atucha-1 experience is encouraging to continue with similar programs in

the other Argentinean NNP and for PHWRs in general.

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Acknowledgments

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• To CONUAR and NASA for providing information for

this paper

• To the National Library and IAEA for supporting this

meeting

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Thank you for your attention!!

Gracias por su atención!!

status of fuel engineering activities on extended burnup …€¦ · · 2014-04-08status of fuel...

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