3 years of experience with tvel fuel at npp temelínftp.vver2013.com/vver 2013 - day ii., parallel...

3 years of experience with TVEL fuel at NPP Temelín

VVER 2013

Prague, November 2013

Daniel Ernst & Lukáš Milisdörfer

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Content

History

Operational Experience - Fuel

Fresh Fuel Assembly Damage

Post Irradiation Inspection Program

Experience with TVSA-T

Operational Experience - Core

Conclusion

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History

Contract with TVEL was signed in 2006

First fuel assembly (FA) – TVSA-T - was loaded into the reactor of Unit 1 in July, 2010 and into the reactor of Unit 2 in May 2011, respectively

All Westinghouse FAs were completely unloaded from both cores – no mix cores!

3 cycles at Unit 1 and 2 cycles at Unit 2

3 leaking FAs (1st Cycle at Unit 1) from more than 530 FAs

Both cores are operated at 104% Nnom (~1060 MWe)

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Operational Experience – Fuel (1)


Fresh fuel loading to the pool storage racks

End fitting of the loading machine mast struck the storage pool rack

End fitting shell got distorted inward

Sudden loss of load during assembly insertion

TV examination revealed bottom nozzle and spacer grids scars and distortion at 2 assemblies

Damaged assemblies brought back to fresh fuel storage, mast replaced

1 assembly reconstituted at fresh fuel building (nearest fuel rod replaced)

1 assembly rejected, new core design using spare (but different) assembly

Evident SPTR (azimuthal) power non-uniformity during cycle

Mid-term burn-up non-uniformity in the core inflicted

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RFM Main Mast End-Piece Damage

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Bottom Nozzle Damage

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Mid Grid Damage

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FA Repair

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Post Irradiation Inspection Program (1)

Post Irradiation Inspection Program (PIIP)

With WEC fuel – it substituted the Lead Test Assembly program

With TVEL fuel – we continue with the measurements based on the SUJB requirement (both Units)

11 selected FAs (these 11 FAs were „pre-characterized“)

Measurements are performed by OAO TVEL (Russia) with technical support from ČEZ

Independent measurements are performed by CVŘ (Czech company)

The TVSA-T inspection program includes (among others):

FA measurements

• Visual Examination – condition of all connections, FR cladding surfaces…..

• FA Bow

• FA Twist

• Overall FA Length Measurement

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Unit 1 EOC11 PIIP Results (end of 3rd Cycle with TVSA-T)

13 FAs was measured:

• 9 FAs after three cycles

• 2 FAs after two cycles

• 2 FAs after one cycle

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Unit 1 EOC11 PIIP Results (end of 3rd Cycle with TVSA-T) – Results

No mechanical damages of all FA component, no debris found

All connections are in good condition

No extensive corrosion of cladding and grids

All measured parameters are in agreement with the prediction and there are sufficient

margins to design criteria:

FA Bow - < 5mm (15mm) FA Twist – max. 1° (5°)

FA Growth – max. 3,5mm (4mm) FR Growth - < 13mm (~30mm*)

* - there in no design criterion, the FR growth is limited to ~ 30 mm which is distance between the FR end-plug and top

nozzle (for fresh fuel).

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Experience with TVSA-T – Core Design

(1) The updated safety analysis were implemented with TVSA-T

Developed by TVEL (+ its subcontractors)

Independently elaborate by domestic supplier – ÚJV (co-op with Skoda JS)

Updated SA for operation on up-rated power (104 %) prepared by domestic suppliers

Conformable with new SA: the reviewed RSE methodology is used

Original I&C and other systems is used

Basic principles (construction of TechSpec, etc.) remain valid

the surveillance criteria was updated, etc.

System of crucial watched parameters respects the original Westinghouse-based I&C

e.g. peaking factors FQ, FΔH instead of „Russian“ KQ, Kr, etc.

Combination of above-mentioned results in Temelin-specific methodology approach

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(2) Used Core Design Codes

For the first cores

Conventional Russian NF codes system BIPR/PERMAK used by TVEL (KI)

Formerly used Westinghouse NF hex codes system ANC-H/PHOENIX-H

Modified to be able to handle with Gd fuel

Used for independent calculation, verification and supplemental calculations

Used for CMS – BEACON model preparation

Domestic code ANDREA with HELIOS intended to be used as main NF codes system

Independent verification, etc. – MOBYDICK 1000 – SJS

Core Monitoring System – BEACON, ver. 6

Modified to correspond to specific requirements caused by revised SA

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(3) Core Prediction vs. Measurement

Observed at first cycles with TVSA-t (full-load of TVSA-T)

Some of differences was code-independent – A/O

Other higher or lower depending on used NF code

the radial power distribution

boron concentration

Axial offset – real A/O was less negative than model

Boron concentration

BOC and EOC was correct

Some differences in the middle of the cycle

All safety criteria of M/P differences was met

All these parameters are in excellent correspondence from the second cycles

On both units

Confirmed that higher M/P discrepancies related just to first cycles

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Operational Experience – A/O Instability

Observed at first cycles with TVSA-t (full-load of TVSA-T)

Divergent oscillation

Needs more frequent intervention from operators (compared to previous cycles)

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Operational Experience – Core

Asymmetry

Observed after 1st cycle on unit 1

Asymmetric core design – due to fuel leakage and absence of suitable spare FA

3 leakers initial enrichment: 2x 3,99 % and 1x 3,9 % replaced by

3 spare assemblies enriched: 2x 3,53 % 1x 2,0 % 235U

After one cycle the FA causing the asymmetry replaced by delivered suitable spare FA

Small Impact on following cycles

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Asymmetry

CB08 CH06 CI06 CI07 CH07 CB26

CB33 CD07 CC17 CC13 DB43 CB35

CH08 CC27 CC21 CH09

CI08 CC15 CB28 CD03 CD09 CB11 CC31 CI09

CI12 CD06 CB18 CB31 CD01 CI03

CH12 CC26 CB21 CG07 CG09 CB34 CC14 CH03

CB32 CD11 CB15 CC28 CC19 CB06 CD08 CB12

CF07 CC23 CB25 CG13 CC03 CC06 CG14 CB22 CC29 CF09

CB09 CD02 CB13 CC09 CC35 CB05 CD05 CB27

CH11 CC25 CB23 CG17 CG02 CB04 CC18 CH01

CI11 CD10 CB40 CB16 CD04 CI01

CI05 CC02 CB14 CD12 CD13 CB03 CC34 CI10

CH05 CC20 CC22 CH10

CB07 CF08 CC08 CC01 DI01 CB19

CB20 CH02 CI02 CI04 CH04 CB02

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02

03

04

05

06

07

08

09

10

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13

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16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

IIII

IV

II

CG06 CE10 CG05

CG01 CC32 CB39 CB01 CC11 CG15

CC04 CF06 CC36

CE04 CB37 CF10 CF11 CB41 CE11

CB30 CE02 CA42 CE01 CB42

CG11 CC07 CA07 CA08 CC33 CG12

CF04 CC16 CF03

CG18 CC30 CA45 CA35 CC24 CG04

CB10 CE08 CA10 CE06 CB24

CE12 CB29 CF12 CF05 CB43 CE03

CC05 CE09 CC37

CG10 CC12 CB17 CB36 CC10 CG16

CG03 CE05 CG08

Region 13A

Region 14A

Region 15A

Region 16C

Region 16B

Region 16A

Region 17A

Region 17B

Region 17C

Spare P36E9

Spare A200

U1C10 after Redesign_2

ČEZ ETE - oddělení reaktorové fyziky

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Asymmetry

Re

lative

po

we

r

Core Burn-up [EFPD]

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Operational Experience – Tritium

Production It was realized that Temelin 3H is significantly higher compared to similar power plants

Strange behavior at the end of cycle (0 boron concentration, „closed“ primary circuit)

Increasing tritium activity

The secondary neutron sources was thus identified as additional tritium source

Sb-Be neutron sources

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Operational Experience – Tritium

Production Current neutron sources are near the end of their lifetime

New one will be delivered by TVEL

Currently the characteristics (amount of Sb-Be) of the sources are under

discussion

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Core Operation Summary

All observed issues was explained

Did not attack safety criteria

Almost all of them was observed in first cycles with TVSA-T – specific cycles

Full-load of TVSA-T,

→ high neutron leakage,

Specific power distribution compared to second, and equlibrium cycles,

etc.

Up-rated power (104 %) of course decrease some limited core parameters margins

Did not attack safety criteria

No anomalies connected with up-rated power

In conclusion: the core operation with TVSA-T is in terms of expectation and no

serious issues was encountered

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Conclusion

Existing operational experience shows good fuel performance and mechanical stability. The

TVSA-T cores operation does not indicate any serious issues and the cores behavior

corresponds with predictions. Several differences (in contrary with VVANTAGE-6 cores) were

observed – like a different axial power oscillation stability, etc; mainly at fist cycle.

3 years of experience with tvel fuel at npp temelínftp.vver2013.com/vver 2013 - day ii., parallel...

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