ML20148E127
| ML20148E127 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 10/27/1978 |
| From: | Turbak M COMMONWEALTH EDISON CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7811060120 | |
| Download: ML20148E127 (8) | |
Text
.
f *l % Ccmm:nw:dth Edis:n t
j.-
- 7 One First National Plaza. Chicago, Illinois 1
'v' g Address Reply to: Post Office Box 767 g f/ Chicago, ll!inois 60690 October 27, 1978 Mr. T. A.
Ippolito, Chief Operating Reactors - Branch 3 Division of Operating Reactors U.S. Nuclear Regulatory Commission l
Washington, DC 20555
Subject:
Quad-Cities Station Unit 1 Feedwater Nozzle /Sparger and Control Rod Drive (CRD) Nozzle Inspection Programs NRC Docket No. 50-254 References (a) :
G. A. Abrell letter to D. L.
Ziemann dated September 22, 1976 (b):
G. A. Abrell letter to D.
L.
Ziemann dated October 18, 1976 (c) :
General Electric Report, NEDC-21189 dated February 1976, " Quad-Cities 1 Feedwater Nozzle Cladding Crack Repair Report" (d) :
General Electric Report, NEDE-21821 dated March 1978, " Boiling Water Reactor Feedwater Nozzle /Sparger Final Report" (e) :
M.
S. Turbak letter to D. K. Davis dated June 23, 1977 (f) :
M.
S. Turbak letter to G. Lear dated November 8, 1977 (g):
M.
S. Turbak letter to G. Lear dated April 25, 1978 (h):
M.
S. Turbak letter to D.
L. Ziemann dated May 15, 1978
Dear Mr. Ippolito:
The purpose of this submittal is to provide the control rod drive (CRD) return nozzle and the feedwater nozzle inspection k
programs to be implemented on Quad-Citics Unit 1 during the next h
^
761LCG Ol3
\\
L
Commonwealth Edison NRC Docket No. 50-254 Mr. T. A. Ippolito: October 27, 1978 refueling outage which is presently scheduled for January 1979.
Justification for these programs is provided below, along with the long-term plan for the modification of the feedwater nozzles on this unit.
Feedwater Nozzle Program I.
Feedwater Nozzle /Sparger Inspections The feedwater nozzle /sparger inspection program for Quad-Cities Unit 1 will consist of the following:
1.
Examination of the visible portions of the four (4) spargers using underwater television equipment.
2.
Ultrasonic examination of the inner blend radius and bore of the four (4) nozzles using procedures NDT-C-24 and NDT-C-25.
3.
Ultrasonic examination of the four (4) feedwater nozzle safe ends and safe end welds.
4.
Acceptance criteria for the ultrasonic examination shall be identical to that defined in Reference (a),
i.e.:
a.
The calibration piece shall be a duplicate (same material and geometry) of the actual feedwater nozzle and the adjoining section of the vessel wall and associated weld.
b.
Instrument calibration shall be performed by setting the response of an 8 mm deep notch in the blend radius and bore of the duplicate nozzlo to 80% of full screen height (FSH).
c.
The examination shall be conducted at a sensitivity equal to the calibration sensitivity plus an additional 6 db in accordance with ASME Code, Article I-5112 of Section XI.
Commonwealth Edis2n NRC Docket No. 50-254 Mr. T. A.
Ippolito: October 27, 1978 d.
All relevant indications with an amplitude greater than or equal to either 50% of the reference reflector (8 mm notch) or 10% FSH above the clad roll noise level shall be recorded and evaluated.
This evaluation shall be in accordance with the methods defined in Reference (b).
All evaluations will be made at calibration sensitivity.
e.
If a relevant indication is evaluated as 80%
FSH or more at calibration sensitivity, a dye penetrant examination will be made of the area containing the indication.
II.
Justification for the Proposed Feedwater Nozzle /
Sparger Inspection Program Quad-Cities Unit 1 is scheduled to begin, in January 1979, its second refueling outage following the installation of the interference fit forged-T feedwater spargers.
These spargers were installed during the January 1976 refueling outage.
A complete dye penetrant examination of the four feedwater nozzles was performed prior to the installation of the new spargers.
All indications found were removed by grinding as reported in Reference (c), leaving no linear indications.
A re-examination of these nozzles was performed during the 1977 winter refueling outage after 18 accumulated startup/ shutdown (SU/SD) cycles.
The examination consisted of an external ultrasonic inspection of the nozzle using CECO. procedures UDT-C-24 and NDT-C-25 which have previously been transmitted to the NRC.
An underwater TV camera inspection was also performed.
No reportable indications were found.
The CECO. ultrasonic testing procedures used for examination of the feedwater nozzles have been demonstrated to be capable of detecting flaws.2L4 mm in depth.
However, for the purpose of the vessel examination, the procedure requires that an 8 mm notch be used as a calibration reference which ensures the detection of flaws 2 8 mm in depth.
General Electric has similar experienca with their UT techniques as reported in Reference (d).
Crack growth curves, developed by General Electric, were formulated assuming leakage flow past the thermal sleeve on the sparger as is postulated with the loose fit sparger.
Considering the experience accumulated with the interference fit sparger, this assumption makes the CECO. plant unique cycle analysis discussed in References (e) and (f) a very conservative method
Ccmmonwaalth Edison NRC Docket No. 50-254 Mr. T. A. Ippolito: October 27, 1978 of determining crack growth rate.
Figure 1 contains data accumulated by General Electric on crack depth for up to 75 SU/SD cycles with the interference sparger in use.
A curve established using the G.E.
assumed thermal cycle is compared to the actual interference fit data.
It can be seen that the worst case of the 10 units with the interference fit sparger has a maximum crack depth of 0.2", with only one other unit having a maximum crack depth of 0.1".
The remaining eight units, however, had maximum crack depths that were much smaller or non-existent.
The above facts point out the effectiveness of the interference fit sparaer in eliminating the leakage flow which is the mechanism causing the cracking.
Inspections on Dresden Unit 2 and Quad-Cities Unit 2 confirmed the above trend for plants with interference fit spargers.
During the Fall 1977 outage on Dresden Unit 2, a dye penetrant examination was performed on the accessible areas of three of the feedwater nozzle and a complete dye penetrant exam was performed on the remaining nozzle with the sparger removed.
Nine linear indications were found, eight of which were removed by flapper wheel grinding.
The ninth indication was removed by grinding less than 1/16" in depth.
The unit had 33 accumulated SU/SD cycles since the original repair and installation of the interference fit spargers.
During the Spring 1978 outage on Quad-Cities Unit 2, a dye penetrant examination of the accessible areas of three nozzles and of all the areas of the remaining nozzle with the sparger removed was also performed.
No linear indications were found.
The unit had 44 SU/SD cycles since the initial repair and interference fit sparger installation.
Up to the present time, Quad-Cities Unit 1 has accumulated 47 1/2 SU/SD cycles since the original repair and will have approximately 51 1/2 at the start of the outage.
Based on the dye penetrant examination data provided by General Electric for the 10 units and CECO. data for Quad-Cities Unit 2 and Dresden Unit 2, it is our contention that no defects deeper than 0.2" exist in the Quad-Cities Unit 1 nozzles.
Finally, as part of the ongoing program to provide a
" final fix" solution to the feedwater nozzle cracking problem, Commonwealth Edison will install the new General Electric double seal / triple thermal sleeve sparger and will remove the clad from w
l Commonwealth Edison NRC Docket No. 50-254 Mr.
T.
A.
Ippolito: October 27, 1978 l
the feedwater nozzles on Quad-cities Unit 1.
At the present time, this work is planned to occur during the long outage associated with the Mark 1 containment work scheduled for the Fall of 1980.
In summary, our technical evaluation of the Quad-Cities Unit 1 feedwater nozzles indicate that:
1.
All indications on the feedwater nozzle inner radius were removed during the original clad repair and interference fit sparger installation.
2.
The ultrasonic examination procedures used will insure that any cracks Z_8 mm in depth will be detected.
3.
Feedwater nozzle inspection data from General Electric and CECO. has proven the effectiveness of the inter-ference fit sparger for providing an end to the effects of the thermal cycling on the feedwater nozzles in that after 75 SU/SD cycles, the deepest crack found to date has been 0.2" (approximately 25 percent of the critical flaw size).
4.
Quad-cities 1 will have approximately 51 1/2 SU/SD cycles by the beginning of the upcoming refueling j
outage, which is well below the threshold for which cracking has been observed on units with interference fit spargers.
On the basis of these facts, it is judged that the inspection program defined above is adequate.
Furthermore, as stated, plans are being made to install the new G.E. double seal / triple thermal sleeve sparger and to remove the nozzle cladding on Quad-Cities Unit 1 during the Fall 1980 Mark 1 outage.
Considering the above, plus the fact that a dye penetrant examination of the feedwater nozzle would expend approximately 200 man-rem and 10 critical path days of outage time, we believe that a dye penetrant exam is not warrantad.
An estimated 29 SU/SD cycles, determined from QC-1 cycle history will occur prior to the start of the Mark 1 refueling outage, resulting in a total number of cycles which is still within the limits of experience with the interference fit sparger.
It is our position that the proposed inspection program provides a safe and reliable incpection which will not compromise unit availability.
Ccmmonwsalth Edison NRC Docket No. 50-254 Mr. T. A.
Ippolito: October 27, 1978 CRD Return Line Nozzle Program I.
CRD Nozzle Inspections The CRD return line nozzle inspection program for Quad-Cities Unit 1 will consist of the following:
1.
Examination of the visible portion of the thermal sleeve using underwater television equipment.
2.
Ultrasonic examination of the inner blend radius using CECO. procedure NDT-C-26.
3.
Ultrasonic examination of the vessel wall below the CRD return line nozzle extending 8" below the centerline of the nozzle where physically practicable.
4.
Ultrasonic examination of the safe end and safe end welds.
II.
Justification for the Proposed CRD Return Line Nozzle Inspection Program An inspection of the Quad-Cities Unit 1 CRD return line nozzle was performed during the Spring 1977 refueling outage.
The inspection consisted of an underwater television camera examination of the nozzle and thermal sleeve.
The thermal sleeve was found intact during this visual examination.
Quad-Cities Unit 1 has a welded thermal sleeve, identical to that of Quad-Cities Unit 2, which was removed from Unit 2 during the Spring 1978 refueling outage.
A dye penetrant examination of that unit was performed at the inner blend radius and the area l
below the nozzle, with no linear indications being found.
Both Dresden Unit 2 and Unit 3 had welded thermal sleeves which were found cracked during an underwater TV camera inspection.
Minor base metal cracks were observed on the Dresden units as reported in references (g) and (h) during the ensuing dye penetrant examination.
Following the nozzle inspection on QC-1, the CRD return line was valved out, terminating the 50 -100 F condensate flow 0
through the return line.
Eliminating this cold flow puts 2.n end to the source of the thermal cycling which has been determined to be the mechanism of crec';ing.
Commonwealth Edison NRC Docket No. 50-254 l
Mr. T. A. Ippolito: October 27, 1978 Considering the above, the inspection is judged to be sufficient to provide information on the state of the nozzle.
On the Dresden units, the underwater TV camera inspection was clearly sufficient to discover the cracking problem.
On QC-2, the thermal sleeve was found intact and the dye penetrant examination proved the nozzle to be crack-free.
Finally, with the ultrasonic examination detecting cracks that penetrate base metal, along with the fact that the crack propagation rate is expected
)
to be negligible with the thermal cycling being eliminated, a dye penetrant examination of the nozzle is not judged to be warranted.
A crack will be detected before it becomes large enough to create a safety or availability problem.
It is our position that the proposed inspection is satisfactory and unit availability will not be compromised.
One (1) signed original and thirty-nine (39) copies of this letter are provided for your use.
Very truly yours, y
r.
/
1Q
,b% ~
Q N
M.
S. Turbak Nuclear Licensing Administrator Boiling Water Reactors
OBSERVED CRACK OE PTHS:
A BORE REGION 1.6 O BLEND RADIUS h PLANTS Wif H PARTIAL FlxCS (WE LDEO SPARGE R, INTE R-O 15 FE RE NCE FIT SPARGE RS. OR NINE MILE HIGH FERRITE CLADOlNG)
POINT BEST ESTIM A~E 14 ANALYTICAL CURVE 180RE REGIO 66 1.3 UPPER BOUNO ANALYTICAL CURVE (BORE REGION) 11 OVE RSC AS BWR 7
10 2
.i.
3 09 -
n.
2 y
08
=
PILGRIM O
7 j
BEST ESTIMATE HUMBOLOT BAYO 0.7 ANALYTICAL CURVE j
(BLEND R AOlUS)
OYSTE R CHEEK O l
MILLSTONE 0.5 MONTICE LLO U O DRESDE N-2 I ES 2 O OUAO CITIES-1 0.4 PE ACH BOTTOM 2 O o
OORESCEN 3 O
VERMONT 0.3 Y AN KE E 02 A
COOPFA y OVE RSE AS BROWNS FERRY 1 0.1 BWRS PEACH h
OVE RSE AS BOTTOM 4 BWRS BROWNS FE RRY 2 H A T Cr1 1 i
la j
x 1 I
I ^ or - A I
I f
0
[ 80 v
v v
vv 100 120 0
20 40 60 NUMBE R OF STARTUP/ SHUTDOWN CYCLES Figure 1 g--
h--
<.e.ev+i w
rw-
--w ye~ye-w -,- r m w es:ans 1
-r-,
er w ea:
w -,
,e--s
=
r e-o-
.