ML20202C734
| ML20202C734 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/17/1997 |
| From: | Craig C NRC (Affiliation Not Assigned) |
| To: | Essig T NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9712040040 | |
| Download: ML20202C734 (50) | |
Text
{{#Wiki_filter:_ _ __ _- l $'
- MEMORANDUM TO: Thom:s H. Essig, Chief Novcmber 17, 1997 [ -
Generic Issues and Environmental MJMMd Projects Branch Division of Reactor Program Management Office of Nuclear Reactor' Regulation FROM: C!audia M. Craig, Senix Sroject Manager Original Signed By: Generic Issues and En A:nmental Projects Branch Division of Reactor Program Management gn Office of Nuclear Reactor Regulation p$ g 8 5 m SUBJECT. SUNIMARY OF MEETING WITH WESTINGHOUSE TO a < O D'SCUSS AXIAL OFFSET ANOMALY (AOA) AND SEABROC@ $ m FUEL FAI'.URES gg Q q The subject meetir.g was held at the Nuclear Regulatory Commission (NRC) offices (H' s a Rockvi!!e, Maryland on October 23,1997, betwean representatives of Westinghouseppd the NRC staff The meeting was held to provide additionalinformation regarding the AOA'ancTihe Seabrook fuel failures. By letter dated November 6,1997, Westinghouse provided both proprietary and non-proprietary versions of the presentation material. Attachment 1 is a copy of the non-proprietary presentation material. Attachment 2 is a list of meeting participants. Westinghouse provided a summary of the Calloway AOA event and described the various actions taken in response to the event, including the plant being held at 70% power for the remainder of the fuel cycle. Westinghouse described a meeting that was held to solicit input from utilities, Westinghouse, and EPRI on possible solutions to the AOA issue. Westinghouse provided details on what actions they have taken to determine how to maintain shutdown margin. Westinghouse concluded that higher boiling rates increase AOA susceptability, however, other contributors may include ciud source, coolant chemistry, and boron and lithium concentration. Westinghouse described several EPRI and Westinghouse programs that are evaluating the AOA issue. Westinghouse also provided additionalinformation about the fuel failures at Seabrook and the results of the evaluation to date Westinghouse performed fuelinspections, a power hisMry evaluation, visual and eddy current examinations on the fuel, oxide measurement, profilon:etry, and crud scraping. Wes'unghouse described the mechanisms that have been ruled out and discussed the two possible causes: intemal contamination possibly exacerbated by high sustained rod power and crud-induced corrosion. Westinghouse cautioned the root cause may be a combination of the two. Westinghouse described what other actions are being considered and described the corrective actions being taken for Seabrook. Westinghouse expects a decision on whether further examinations are needed by thc fm quarter of 1998. Attachments: As stated " cc wlatts: See next page ~ - Distribution: See next page i DOCUMENT NAME: 10_23_97. MIN DISTRIBUTION: See next page OFFICE PGEB ,
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/*, UNITED STATES g } NUCLEAR REGULATORY COMMISSION 2 WASHINGTON, D.C. 30666-0001 y..... November 17, 1997 MEMORANDUM TO: Thomas H. Essig, Chief Generic lasues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation
( , FROM: Claudia M. Craig, Senior Project Manag Generic issues and Environmental b ~(, QQ - Projects Branch i Division of Reactor Program Management Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF MEETING WITH WESTINGHOUSE TO DISCUSS AXIAL OFFSET ANOMALY (AOA) AND SEABROOK FUEL FAILURES The subject meeting was held at the Nuclear Regulatory Commission (NRC) offices in Rockville, Maryland on October 23,1997, between representatives of Westinghouse and the NRC staff. The meeting was held to provide additionalinformation regarding the AOA and the Seabrook fuel failures. By letter dated November 6,1997, Westinghouse provided boih proprietary and non-proprietary versions of the presentation material. Attachment 1 is a copy of the non-proprietary presentation material. Attachment 2 is a list of meeting participants. Westinghouse provided a summary of the Calloway AOA event and described the various actions taken in response to the event, including the plant being held at 70% power for the remainder of the fuel cycle. Westinghouse described a meeting that was held to solicit input from utilities, Westinghouse, and EPRI on possible solutions to the ACA issue. Westinghouse provided details on what actions they have taken to determine how to maintain shutdown margin. Westinghouse concluded that higher boiling rates increase AOA susceptability, however, other contributors may include crud source, coolant chemistry, and boron and lithium concentration. Westinghouse described several EPRI and Westinghouse programs that are evaluating the AOA issue. Westinghouse also provided additionalinformation about the fuel failures at Seabrook and the results of the evaluation to date. Westinghouse performed fuel;nspections, a power history evaluation, visual and eddy current examinations on the fuel, oxide measurement, profilometry, and crud scraping. Westinghouse described the mechanisms that have been ruled og and . discussed the two possible causes: internal contamination possibly exacerbated by high sustained rod power and crud-induced corrosioti. Westinghouse cautioned the root cause may be a combination of the two. Westinghouse described what other actions are being considered and described the corrective actions being taken for Seabrook. Westinghouse expects a decision on whether further examinations are needed by the first quarter of 1998. Attachments: As stated cc w/atts: See next page ___ _- ___- _ __ _ - _ _-_- _-- - ~
- y .
i WESTINGHOUSE NON-PROPRIETARY CLASS 3 Axial Offset Anomaly and .
- Seabrook Update .
s ! i i l October 23,1997 Westinghouse CXFD , i i l l
- i Attachemnt 1
. . ~.
Axial Offset Anomaly . . Nuclear Regulatory Commission 1 .i
- 10/23/97 ,
l Rockville, Md. t Sumit Ray Westinghouse CNFD e
.3 Purpose of AOA Customer Meeting
+ Issue: ;
- Due to loss of shutdown margin from extended operation with large AOA, Callaway Cycle 9 is currently forced to operate at 70% power to maintain sufficient SDM :
- Assuming no net LiBO2 removal, plant will likely remain at 70% for remainder of cycle
+ Meeting Objective:
- Develop additonal options that will results in a more rapid return to full power for Callaway Cycle 9 9
V i i
,I AC)A Meeting Attendees
+ Westinghouse Fuel + Westinghouse
+ L~nion Electric + Non-Westinghouse .;
. + Southern Nuclear Fuel and Others '
+ Northeast Utilities + TU Electric o
+ North Atlantic _ + Duke Power .!
Seabrook + Yankee Atomic
+ Wolf Creek + EPRI .
2 AOA Meeting Agenda
~
+ Callaway Cycle 9 ADA summary - UE
+ Cycle 9 recovery options - Westinghouse l - Core Design / Safety Analysis
- Chemistry
+ Cycle 9 power reduction to 30% - Westinghouse 1
l + EPRI AOA susceptibility investigations - Duke / NU l + Discussion - All 1
. .. . n Conclusions .
~
+ Various utilities with AOA as well as EPRI attended the Westinghouse AOA meeting
+ No additional ideas for shutdown margin improvement
+ General agreement on how to assess core design contribution to AOA susceptibility
+ Various suscepti'oility approaches provide similar guidance
Ongoing industry AOA efforts
+ Westinghouse Owners Group (WOG)
! + EPRI TCP - AOA susceptibility :
+ EPRI robust fuel assembly program :
+ Westinghouse internal programs ;
I b
i . 3 e e Axial Offset Anomaly Nuclear Regulatory Commission 10/23/97 Rockville, Md. Jeffrey R. Secker Westinghouse CNFD e
._~l
* ~
I i L Topic-s of Discussion . l l + Callaway update since 10/8/97 j + AOA 10/09/97 Westinghouse / Utility .
- meeting summary - core models and .
- l -i shutdown margin i
i l ! i i 4
.- tj l Callaway Update -l l
Axial Offset and Shutdown Margin l I + pH reduction from 7.05 to 6.9 on 10/14/97 l resulted in positive AO shift
+ Flux map on 10/16/97 indicated 2.2%
l positive AO shift compared to 10/7/97 map l
- _ +(a,c)
+ Results in about _' pcm increase in l _
available shutdown margin t P I
Callaway Cycles 9 ' Measured and Predicted Axial Offset 20.0 _ _a .
- t .
u _. _. 18.0 ; ; O O Cy 9 Measured ACZ "~ _-== C O Cy 9 Predicted AO -" 16.0 : . 1 , ,
=
; ~
~
~
14.0 5f"
-- '- ~~ I - -
I 12.0 .
! =I=
10.0 . e _. _ = i l 8.0 ~T - ~ " . ~ _ ~ _ ~ '. i 6.0 _ l # 4.0 -_ ! 15 2.0 y m c 0.0 ____m.
-_,-qum=w--cw := -- -----;; :: :w , . : _ -
- :n o -2.0 g -,
- 3 ,
i
-4.0 ' --
i !
-6.0 .
t ; l -8.0 A 1 -10.0 _:h, i
- 1 -
-12.0 - -
m
=
'=-
4 '
-14.0 _
=- .
-16.0 ---
-18.0 __
0.0 10000 15000 20000 0 5000 Cycle Burnup (MWD /MTU)
l .-
.;-l i Rod insertion limit modification .
l for shutdown margin increase
+ Callaway had previously made RIL more restrictive to increase shutdown margin at all l
! Dower levels l l
+ RIL at 70% raised to 201 steps to increase i reduced power shutdown margin .+ (*,c)
. j l
- + Results in shutdown margin increase > _ _
pcm i 4
4 g Callaw sy Cycle 9 R'" 7 225 :
~
, 1 1 1 11 1 1 i ii (4. 6 3, 225)I /
/ '! ' ! iil i
(57.87,225)I 3
.T- "
-{ BANK B l; /,
j
~
(0, 215) =ji / (100, 201)f-200 , /
/
/
/
/{i
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,)
,!r m
l 175 ' 7
/; /
/ BANK C _I /
/ '
/
H f }
> 150 / y ;
m / : / !
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/ /
~ 125 j' ,/
5 / / BANK D l p / / 6 m / / m j r 2 100 - (0, 100)l
/ i
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h / 3 / g 75 , j u /
, s'
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50 j , , ;
/ i ! !
i f i i s' _ l 25 , f
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!! l
!! A - 1 Ii i iii /i (6.94, 0)I i i ! ii 0 !iI ! lil!!Ili ! I i i !! '!
0 10 20 30 40 50 60 70 80 90 100 PERCENT OF RATED THERMAL POWER Figure 2 Callaway Cycle 9 Rod Bank Insertion Limits Versus Rated Thermal Power - Four Loop Operation e O 7 .
. . _ . . - . _ - . . _ _ . . _ _ _ . _ _ _ _ . . _ _ _ , _ _ _ _ . . - _ . . . . . . . . . _ . . _ . . . - - . . - . . , , . _ . . . , , _. .. __,_...--_m.. , _ _ _
_ ..., $7
- _ _ _ _ . - _ _ _ _ _ - . . . . . - . _ . . _ , _ - _ . . _=. . .- - _ . _ _ . . - _ . - ._. ._
Cal;nsy cycle 9 Rev.8 l/ 3 ! l I ! iiI I 22$i f I ! I iiil l I l_ (81.02,225)I
/ ~
(27.78,225)[ / y f
/ I /
200
' j
/ /
/ BANK C I /
/ /
-~ /
g 175 f
/r. f g (I0, 165)j /
/
/
E 150 j , m / A /
/ BANK D I h
~
125 j/ , E / . y / > m / m e g 100 /
)
/
/
95
/
/
/
50
~
(0, 50)[ 25 , I l i i i i li 0 1 ! ) i 0 10 20 30 40 50 60 70 80 90 100 PERCENT OF RATED THERMAL POWER Figure 2 Callaway Cycle 9 Rod Bank Insertion Limits Versus Rated Thermal Power Four Loop Operation 4 _ , _ y - - . - - . _ _
i
- l Shutdown Margin Results 1
l l + Current Cycle 9 Shutdown Margin at 70% Power
- B u rn u p SDM SDM M W D /M TU (p c m ) (p c m )
S a fe ty O p e ra tin g
~
A n a ly s is (S tu e k to d
+ AOA)
~
13707 <* ') <a, c) 14200 ) I4700 . . l I
~
Shutdown Margin Conservatism Callaway Cycle 913707 MWD /MTU 70% Power AOA Shutdown Mart,in Calculations at 70% Power Shutdown SDM Margin (pcm) Change (pcm) NDR Model Nominal AOA Model Nominal AOA Fully Removed 0% Power
+ Temperature Uncertainty + 70% P Rod Insertion (201 Steps Withdrawn; + Axial Flux Difference to Pos Limit (D-201) + Worst Stuck Rod + Void Collapse + 7% N-1 Worth Uncertainty Sources of Additional SDM Reduced Rodworth Uncertainty - 3% N Relaxation of Instantaneous AOA Boron Loss Assumption af ter trip Aual ofhet Anomaly . AoA core models and shutdowt margin analysis ',
I . Purpose of AOA Customer Meeting 1 ! i
~
+ Issue: ,
b
- Due to loss of shutdown margin from extended operation with large AOA, Callaway Cycle 9 is currently forced to operate at 70% power to maintain sufficient SDM
- Assuming no net LiBO2 removal, plant will likely remain at 4
70% for remainder of cycle
+ Meeting Objective:
- Develop additional options that will results in a more rapid j return to full power for Callaway Cycle 9 ;
l 1 ! l ! f I
~
4
i AOA Meeting Agenda ,
+ Callaway Cycle 9 AOA summary - UE O
+ Cycle 9 recovery options - Westinghouse .:
.i
- Core Design / Safety Analysis
- Chemistry -l
+ Cycle 9 power reduction to 30% - Westinghouse 0
; + EPRI AOA susceptibility investigations - Duke /
NU l + Discussion - All l 1 l
e . I Callaway Cycle 9 Plant Status I
+ UE presented Callaway AOA overview for meeting participants
+ Same information as 7/31/97 NRC meeting
- + Updated with COLR modifications (Rod insertion limit changes) that have occurred since 7/31
~
^
l i i
l . Cycle 9 Recovery Option - Core Design
+ AOA core modeling and shutdown margin
- same material presented as was provided to NRC during 10/7/97 and 10/8/97 meetings in Pittsburgh
- No concerns raised on modeling or SDM
+ Items discussed included reduced rodworth uncertainty and credit for time dependent
.. dissolution of boron compound after trip i ! - general agreement by meeting participants that conservatisms in these areas could be reduced
^
l
i
- AOA susceptibility l + EPRI and Westinghouse have been I mdependently evaluating inethods to l determine AOA susceptibility
- + Various Thermal / Hydraulic analyses have s
l been performed to examine sub-cooled boiling rates l
+ More detailed than previous peak rod l!
boiling rate comparisons t i
O e i l AOA susceptibility methods i l + EPRI using VIPRE-01 code with 3-D core model power i distributions to determine detailed burnup dependent boiling rates ,
+ Westinghouse has performed boiling rate calculations for :
4 top 10%/20%/30% of rods in the core as a function of : cycle burnup ;
.+ Westinghouse ANC code also has subcooled boiling
! model which has been used to predict void fraction as a function of burnup
- comparisons to EPRI VIPRE boiling rate predictions show good agreement i -
i i
~
AOA susceptibility conclusions
! + In general, higher boiling rates increase AOA susceptibility
+ Boiling rate alone does not always explain plant-to-plant or cycle-to-cycle AOA differences. Other ?
i possible contributors:
- crud source l
- coolant chemistry l
- boron and lithium RCS concentrations
. _m-- . _,
i
. .l AOA susceptibility conclusions
+ Intermediate flow mixing (IFM) grids allow higher boiling rates before AOA susceptibility ,
occurs
+ Westinghouse and EPRI independent results and -
conclusions are in agreement
+ Westinghouse has added AOA susceptibility i ~
evaluation to LP risk assessment procedures
+ Westinghouse continues to work on improving methods for predicting AOA susceptibility
AOA meeting summary - core design
+ Utility interest in AOA high
+ Utilities present support reduced conservatism in rodworth uncertainty and treatment of boron in crud after trip
+ No additional ideas on shutdown margin or core design for Callaway Cycle 9
~ ~
Conclusions
+ Various utilities with AOA as well as EPRI attended the Westinghouse AOA meeting i l + No additional ideas for shutdown margin improvement .j
+ General agreement on how to assess core design contribution to AOA susceptibility t
+ Various susceptibility approaches provide similar guidance 1
i
.I Seabrook Cycle 5 l Actions from Last Meeting
\
. 3M Hl Meeting held on June 24,1997 4
Actions i .
. Complete data evaluation 1
. . Conc uct Phase 2 On-site Exammation
. Checx for similarities with other rods with similar characteristics
. Review Power History 1
. . _- .N
.l Seabrook Cycle 5 FuelInspection Results 1
. MGMI M N> Hll l . Core inspected 3y in-mast sipping l . Leaking assemblies inspected by UT
! . Results
- 4 once-burned assemblies identified as leaking
- 3 assemblies had 1 leaking rod
- 1 assembly had 2 leaking rods
- All leaking rods were IFBA, next to t:aimble tubes .
- Leaking assem alies were in high power
_OCat10nS - i 4
i l = !
~
l Seabrook Cycle 5 . l Initial FuelInspection Results
. .1 Dr I- *
.. - .. .'t E ' ' :, --
t i Non-leaking rods l . :.0 non-lea cing rods removed for inspection ! 8 IFBA and 2 non-IFBA rods !, . No inc1pient defects ; 4 i ! . No evic ence of fretting i i .
. Crud /oxic e level similar to leaking rods i
t l I ,
e o e Power History Evaluation , GIFsM M . Hil l Steacy-State Power Histories
. W met:aods gave similar results
. Duty nigh, but within range of experience
. Leaking rods were higher power rods in core
. Some non-leadng roc s aad comparab'e duty 6
No signi:icant power transient was identi:lec. Core tilt and AOA present, but relatively low in magnituc e
~' Lower p_enum flow anomaly present
Seabrook: Cycle 5 . Phase 2 Examination , [EM
~
l Ell ' Ac c.itional fuel examinations completed on non-l leaking rods .
. Visualinspection
- . Encircling ec.dy current
. Oxic e measurement i
- - Pre and post crud removal
. Profilometry t
-. . Crud scraping (peripheral rods) i i
. *j Failure Mechanisms Xot Eliminated i
~
5 j~ e n 4 . n M M u a y m 1 x - lll' l l
. Internal containination possibly exacerbated by
! . aigh sustained rod power
. Crud-inducec corrosion
^
i i i i t e
. o l -
.l l
i Team Recommendations FE._rsh. v ar eggt m e.+.y u . 3lll'
- . Complete Cruc analysis
. Additional examinations being considered
- Hot cell
- On-Site
!. - Leaking Rods l
. Data : Prom otaer sites will be used as avaiLable/
appropriate l . f l i m
o Corrective Actions h.ffhjkII: (d 3 M [ . 1.k Wi M 1L O ' ' ~
=
- l Fuel Duty Reduced i
Assemblies with simi: ar duty moved to baffle in ! Cycle 6
- . Cycle length will be reduced in Cycle 7 l . FaH will be recuced in Cycle 7
. W will review Cycle 7 design to address susceptibility to anomalies
s . Future Actions
~
. @ S f R $i e J W e i n : i-
~
EHil Finish reports of Phase 2 examinations 1/98 Complete Crud Exams 1Q98 Decision on need for further examinations Q98
. Leaking rods
. On-Site
. Hot Cell e
2 . ;- NRC Uadate Meeting on AOA October 23,1997 .
- 1. Comparison of cycles-6 and 9 downpower to 30%
- 11. Crud and chemistry options George P. Sabol I
Westinghouse Electric Corporation
4 .- Callaway Cycles 6 and 9 Measured and Predicted Axial Offset 20.0 .
. i ,
18.0 O O Cy 9 Measured AC~ - 16.0 C O Cy 9 Predicted AO _ _ _ . 14.0 ? ? Cy 6 Measured AC - 4 12.0 A ACy 6 Predicted AO _ 10.0 A 8.0 b 6.0
@ 4.0 2 r
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lis 2.0 m. . - ' T^ % _'_%.x.=_ ' s 4 :
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=
-14.0
-16.0
-18.0
-20.0 0 5000 10000 . 15000 20000 Cycle Burnup (MWD /MTU)
O : Callaway Cycle 6 100 : '
$ c :>- 8.00 90 - - - - -
- ^ ^ ~ "
sa ; ; w ca- .' "" -
~
7.00 - t 80 - - - - - - - - - - - - - - - --- :- -- --- :1- -- ----- ----------------------------------- -
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-* pH@
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+Rcs u -
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$ 50 4.00 m D- $
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- m D. 40 ----------------h ---------------- ----------------- ---------------.......
E2 l F - 3.00 n. e r
- n. E 30 ............__ .
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.. x x x- 2.00 ,
20 - . . . .e......... _ ................... ......-- ........ . --......,.. - 4. .- 10 - - - - - - - - - - - - - -
---- ------------------------------------------------------------- - 1.00
.. J t 0 . --.
0.00 l N7/93 4/7,93 4/8/93 4/8/93 4/9/93 4/9/93 4/10/93 410/93 41183 4/11/93 4/12/93 4/12/93 t 0:00 12:00 0:00 12:00 0:00 12:00 0.M 12.00 0-00 12:00 0:00 12:00 i
. Date / Time e
O-m 1 Rationale for CY9 Downpower , 1} Got significant release of LiBO2 on downpower to 30% in CY6 :
- 2} Return to only 70% power would result in minimal hideout
- 3) Anticipate significant net benefit in AOA
- for CY9, with some differences in CY6,9 noted i
i t
Callaway Cycle 9 100 8.00 9G ------=-------=--=-=-----.=-=-=-=-=--.=-=-_=-=-.;.=-=-------^-=---a---
- ==
7.00 [,Q ................................................................................- r 6.00 VN 70 ------c -----------------------------------------------
- - - o-a - .- C o
- W v. -
5.00 m x 60 - - - - - - - - - - - - - - - - ------ ---------------------------------- --------------- -- y
. m cn s_ - RX PWR -
y , 50 - - - - - - - - - - - - - - - - - - - - - --------------------------------- ---
+pHm --
4.00 O- $ l $ --o-RCS U - G3 0 - ES O. 40 - - - - - - - - - - - - - - - - - - - - - - - - - - -------------------------- - ------
-++-u. g x iG-2 .
3.00 n. e
- n. E 30 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -------------------
. ~ -
_.a J c - 2.00 20 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -------------------------
~
10 - - - - - - - - - ---------------.--------------------------------- --------------- 0 :- "
- - " ^ ^ ^ " - ' - " ^
0.00 9/5/97 0:00 9/5/97 12:00 9/6/97 0:00 9/6/97 12:00 9m97 0:00 9/7/97 12:00 we/97 0-00 9/8/97 12:00
.. Date / Time. .
I e i I
CALLAWAY CY6 - CY9 PARAMETER COMPARISON OF DOWNPOWERS TO 30% AND RETURN CY6 CY9 - PARAMETER BURNUP, MWD /MTU 13600 12500 POWER, % 100 70 BORON, PPM 574 869 LITHlUM, PPM 1.7 1.97 7.20 7.0S pH(T) DELTA POWER, % 70 40 TIME OF DOWNPOWER, HR 9.5 15 RATE OF DOWNPOWER, %/HR 7.37 2.67 l HOLDTIME AT 30%, HR 25.75 22.00
. e+(%c TOTAL LI RELEASED, G LI RELEASE ON DOWNPOWER, G TOTTAL Li RELEASES 3HR INTO HOLD, G Li RELEASE ON HOLD, G LI ON DOWNPOWER/ TOTAL Li LI RELEASE AFTER 3 HR HOLD / TOTAL LI TOTAL BORON RELEASED, G ,
TOT Li HIDEOUT, G Li HIDEOUT /LITHlUM RETURN
- 6
Methods for Crud Release Discussed
- Highest probability included attempts at destabilization at power, during cooldown and at
<200 F
- Remove Li at power, operate acid-reducing a few days to initiate release of particulates
- Trip plant to initiate release of particu!ates
- Boration and cooldown to remove dissolving constituents
- - Cool to 200 F, peroxide addition to convert to sa oxidizing conditions for further dissolution of Ni, Co m-
l . 1 . L L . l Coolant Chemistry Practices Discussed
- Shutdown chemistry
- Dose reduction, but also to maximize removal of soluble species from crud l - Startup chemistry ;
- - EPRI Guidelines with increased vigilance for oxygen control and soluble and insoluble Fe, Ni, TSS i
- During operation ;
- Increase coolant alkalinity early in cycle
- Minimize the transition period of increasing pH
- Complete cycle of pH m 7 .2 or higher :
~ ^
l . Performance of ZIRLO Under 1 Boiling o Conditions . i . North Anna Demos which experienced l subcooled boiling showed superior ZIRLO l performance compared to Zr-4 ZIRLO in VC Summer, one of the highest l boiling duty plant, shows better corrosion resistance than Zr-4
. ZIRLO in Millstone 3 cycles 5&6, boiling duty similar to Seabrook performed well
o e i Performance of ZIRLO Under Boiling . Conditions . ZIRLO demo rods in Goesgen (Swiss Plant) with boiling duty higher than Callaway i showed satisfactory performance 37 Regions of ZIRLO-clad fuel operating 3 successfully
- I
ill- :I l! : l:I!! ' .! I
- 1! - ' !>"
l l e t a d . p . g U i t n e n e i o M99 7 t a C 1 i n ~ R N 3
/ 2 _
e _ m s e r . ub - x o t o _ E g c nO k i _ a.mh t o s e o r W b - a e E S I M -
~
a Seabrook Cycle 5 ; j Actions from Last Meeting 35'M . lll t Meeting held on June 24,1997 . Actions .
.1
! . Complete C ata evaluation ,
- . Conduct Phase 2 On-site Examination .!
. Check for similarities with other rods with similar !
- . characteristics ,
.i
. Review Power History .!
~
i _ _ _ - - _ - _ - _ _ __ _ _}}