ML16340C945
| ML16340C945 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 11/03/1982 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Cranston A SENATE |
| Shared Package | |
| ML16340C946 | List: |
| References | |
| NUDOCS 8211160056 | |
| Download: ML16340C945 (8) | |
Text
0
'00 NOV 0
+8'he Honorable Alan Cranston United States Senate l<ashington, DC 20510 Dear Senator Cranston:
This letter responds to Nr. Carl F. Mansfield's letter of IIay 12, 1982 that has been referred to me for reply.
Your constituent expressed concern over the occurrence of multiple pipe breaks before the end of their design life, which could lead to a melting of the uranium fuel; the premature weakening of studs and bolts; the capability of the Diablo Canyon pipes, studs and bolts to withstand a seismic event; and finally your constituent stated "You wfjl also recall that at THI and Ginna valves on the same pipes malfunctfoneWihich is recognized as a problem connected with the two warned-against by the NRC".
In regard to. the first concern, we believe the pipe breaks referred to above to be the rupture of a steam generator tube at four U. S. pressurized water reactor (Pl/R) facilities.
No multiple steam generator tube ruptures have ever been reported.
The tube ruptures in two of the four facilities were attributed to stress corrosion and the third and fourth ruptures were due to a foreign object in the steam generator causing excessive wear or impacting and subsequent pressure rupture of the tube.
The stress corrosion cracking of the tubes is primarily the result of the use of phosphate treatment of the secondary water.
Free caustic can result fn the secondary water becoming corrosfve unless there is strict water chemfstry control when using phosphates.
Since most PNRs now fn operation began operation with, or have converted to, all-volatile treatment (AVT) secondary water chemistry control this should reduce the occurrence of such failures.
For the two plants that still use phosphate treatment, careful control of the phosphate treatment with periodic sludge lancing should substantially reduce tube failure.
To further minimize the occurrence of tube failures, stringent pre-service inspection of steam generator tubes are performed, as was done at Diablo Canyon, prior to the issuance of an operating license.
moreover, the plant 's Technical Specifications require that a percentage of the thousands of tubes of a steam generator be thoroughly inspected at prescribed intervals during the life of the plant.
If during inspection, tubes are found not to meet Technical Specifications acceptance criteria corrective action is required prior to returning the steam generator to service.
The radiological consequences of the tube failures to date have been insignif-icant.
While multiple tube failure could lead,to more serious radiological consequences, ft fs our view that the procedural and other actions being implemented by the industry significantly reduces the radiological consequences and occurrence of sin~1 and multiple tube failures.
82iiih0056 82ii,03
'=PDR ADOCK 05000275 H'.DR 4 ~
000 SURNAME) tto ~ ~ ~ ~ ~ otto ~ ~ ~ ~
0 ~ ~ ~ ~ ~
~ ~ oooot ~ 0 ~ otttooooooooo ~
PATEf
~ ~ ~ ~ ~ ~ 0 ~ 000 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~ ~ ~ ~ ~ 00 ~
~ 00000000000000 NRG FORM 818 (10-80) NRCM 0240
~ ~ ~\\ ~ 0 ~ ~ 0 ~ ~ 0 ~ 0 ~ ~ ~ ~ ~ 0 ~ 0 ~ ~
~ 0 ~ ~ ~ ~ 0 ~ ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ ~ ~ 00 ~
~ ~ ~ \\ ~ ~ 0 ~ 0 ~ 0 ~ ~ ~ ~ ~ 0 ~ ~ ~ 00
~ ~ ~ ~ ~ ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ ~ ~ ~ 0 OFFICIAL RECORD COPY
~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 0 ~ 00 ~ 00 USQPO: 1981~0960
~
E nrau
0
~
Senator Cranston 2
The second concern raised was the premature aging of studs and bolts (threaded fasteners).
The NRC has identified 44 incidents of threaded fasteners degra-datfon since 1964.
Since
- 1975, 15 such incidents, related to the reactor coolant boundary application, have been recorded.
The failure mode of the fasteners is generally attributed, as shown in Table 1 of the enclosed IE Bulletin No. 82-02, to borated water corrosion or stress cracking.
None of the reported failures resulted in any radiological release.
Increased emphasis has been placed on maintenance, installation procedures, and increased surveillance of threaded fasteners in the reactor coolant boundary system as required by IE Bulletin No. 82-02.
With respect to the capability of the steam generator tubing, studs and bolts at Diablo Canyon to withstand a seismic event, in addition to the action steps discussed an extensive independent seismic design verification program is currently underway.
The purpose of thfs program is to ensure that all safety related
- systems, structures, and components can withstand a 7.5N HOSGRI earthquake.
I can assure you that this matter is being vigorously pursued by our staff.
The last concern was the malfunctioning of pilot operated relief valves (PORVs) at THI and Ginna.
The failure modes of the PORVs are different from those associated with steam generator tube rupture.
The PORVs are located at the top of a pressurfzet vesse'l for the purpose of reducing reactor system pressure during operational transfents including steam generator tube rupture.
Recognizing the need to improve the overall reliability of the PORVs, the staff has required additional testing of the PORVs under'arious simulated conditions.
The Electrical Power Research Institute has completed the valve testing program and results to date show that PORVs, the same as those installed at Diablo Ca~yon, performed satisfactorily.
The staff recognizes that failures of the type discussed in llr. tlansfield's letter can occur again.
We believe, however, that the steps we have taken reduces the probability of such failures and that with the defense-in-depth designed into the plant that radioactive releases would be safely controlled.
I trust that the above information l>as been responsive to your constituent's
- -concerns.
Sincerely, (Signed) T.'.h M
Enclosure:
Distribution:
As stated See attached sheet
- See previous Concurrences/Initials William J. Dircks Executive Director for Operations OFFICEI SUANAMElN OATEf DL:LB83
~ 0 ~ ~ 00 ~ 0 ~ ~ 0 ~ 0 ~ ~ ~ 0 ~ ~ OttO ~
BBuckl ey : ph
~ 0 ~ 00 ~ 0 ~ 0 ~ 0 ~ 00000 ~ ~ 0 ~ 0 ~ 0 26/82
~010$ 0000000 ~ 000000000 DL:LBg3
- GKniqhton
~ ~ eeeoooooto
~ 0000000000
~
10/26/82
~ 0 ~ 0 ~ 0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 ~ 0 ~ 0 ~ ~
DL:AD:L
~ ~ ~ ~ 0 ~ 0
~ 0 ~ 0 ~ 00000 ~ ~ ~ 0 ~
- TNovak
~ 0 ~ ~ ~ ~ 0 ~ ~ 0 ~ 00 ~t ~ ~ Oettoo ~
10/26/ 82.
~tte ~ 00 ~ 0 ~ ~ ~ ~ to ~ te ~ 0 ~ 0 ~ 0
~ ~ 0 ~ ~ ~ ~ ~ ~ ~ ~ 0 ~
DEi senhut
~\\ ~ ~ ~ 0 ~ 0 ~ ~ 0 ~ ~ ~ 0 ~ ~ ~ ~ ~ ~ ~ ~ 0 10/29 /82
~\\ ~ ~ 0 ~ ~ ~ 0 OP% ~ ~ ~ 0 ~ ~ ~ ~ ~ ~ 0 ~
NR I
HDe n
~
~ ~ ~
~ ~
~ ~ ~ ~ ~
~ ~ ~
~
1 / g/82 EDO OELD WDircks
- Atto'rneys
'j)'j"~782:" T0727/82""""
NRG FOAM 318 (10~) NRCM 0240 OFFIClAL RECORD COPY USGPO:
$981~960
I A' 0
~,7
~ g
Senator Cranston 2
The second concern raised was the premature aging of studs and bolts (threaded fasteners).
The NRC has identified 44 incidents of threaded fasteners degra-dation since 1964.
Since 1975, only 15 such incidents, related to the reactor coolant boundary application, have been recorded.
The failure mode of the fasteners is generally attributed, as shown in Table
'l of the enclosed IE Bulletin No. 82-02, to borated water corrosion or stress cracking.
None of the reported failures resulted in any radiological release.
Increased emphasis has been placed on maintenance, installation procedures, and increased surveillance of threaded fasteners in the reactor coolant boundary system as required by IE Bulletin No. 82-02.
I With respect to the capability of the steam generator tubing;"studs and bolts at Diablo Canyon to withstand a seismic event, in addition to the action steps discussed an extensive independent seismic design'erification program is currently underway.
The purpose of this program'is to ensure that all safety related
- systems, structures, and components can withstand a 7.5th HOSGRI earthquake.
I can assure you that this matter. is being vigorously pursued by our staff.
The last concern was the malfunctioning of pilot operated relief valves (PORVs) at TllI and Ginna.
The failure modes of the PORVs are different from those associated with steam generator tubegrupture.
The PORVs are located at the top of a pressurizer vessel for the purpose of reducing reactor system pressure during operational transients including steam generator tube rupture.
Recognizing the need to improve the overall reliability of the PORVs, the staff has required additional testing of the PORVs under various simulated conditions.
The Electrical Power Research Institute has completed the valve testing program and results to date show that PORVs, the same as those installed at Diab'lo Canyon, performed satisfactorily.
I trust that'the above information has been responsive to your constituent's concerns.
Sincerely, Enclosur,:
As state" DISTR IBIjTION; See next page William D. Dircks Executive Director for Operations OFFICE/
SURNAME DATEQ
. /'ley/ph
~ ~ ~ o ~ oo ~ o ~
~ ~ o ~ o ~ o ~ oooo r
~olQj o o82oooooo
~
~ o
~t ~
.D
'Gg q
~ ~ oofo ~
~ o ~ottto ~ ~ o ~ ~ o ~
..sop.0gzz.....
~ ~
a
~
~ ~ o ~ o oQL iDotRo ~ ~ ~ ~ ~ ~ ~ ~ ~
DEisenhut Nlm;.OI.R.........
HDenton
.>o/... BZ........1O/...../82......
10/....J.M...
GOO........
WDi'rcks 10J..../N....
j.D............
<~ -Qo>v4
.:.glB,ALA(
i'/82 NRC FORM 818 (10-80) NRCM 0240 OF ICIAL RECORD COPY USGPO: 1981~960
1
GREEN TICKE7. No.
12384 Diablo Canyon Distribution:
Document Control (50-275) w/incoming NRC PDR w/incoming L PDR w/incoming PRC System w/incoming LBb'3 Reading File GKnighton BBuckley JLee w/incoming DEisenhut/RPurple
- JJordan, IE
Correspondence Clerg NRR (EDO 812384)
SECY (3)
OCA (3)
VStello REngelkeh Cunningham, ELD LUnderwood ECase/HDenton PPAS SHanauer RMattson RVollmer HThompson PCheck BSnyder lJDircks OFFICE/
SURNAME/
DATE Q NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USOPO: 1991~~960
~
~