Study of Fast Transient Pressure Drop in VVER-1000 Nuclear ...
3 years of experience with TVEL fuel at NPP Temelínftp.vver2013.com/VVER 2013 - Day II., Parallel...
Transcript of 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 Assembly Damage
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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Operational Experience – Fuel (2)
Fresh Fuel Assembly Damage
RFM Main Mast End-Piece Damage
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Operational Experience – Fuel (3)
Fresh Fuel Assembly Damage
Bottom Nozzle Damage
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Operational Experience – Fuel (4)
Fresh Fuel Assembly Damage
Mid Grid Damage
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Operational Experience – Fuel (5)
Fresh Fuel Assembly Damage
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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Post Irradiation Inspection Program (2)
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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Post Irradiation Inspection Program (3)
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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Experience with TVSA-T – Core Design
(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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Experience with TVSA-T – Core Design
(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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Operational Experience – Core
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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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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Operational Experience – Core
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.