ML20030C674
| ML20030C674 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 08/21/1981 |
| From: | Morisi A BOSTON EDISON CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-10, REF-GTECI-RV, RTR-NUREG-0619, RTR-NUREG-619, TASK-A-10, TASK-OR 81-197, NUDOCS 8108270636 | |
| Download: ML20030C674 (3) | |
Text
e BOSTON EDISON COMPANY GENERAL DrricEs 800 BovLETON STREET Bo sTON. Mass ACHusETTs 0219 9 NUC LE AR OPE RAT RT DEPARTMENT NUCLEAR OPERATIONS SUPPORT DEPARTMENT August 21, 1981 37en,,%
BECo. Ltr
/
by d
Mr. Thomas A. Ippolito, Chief
]3, Operating Reactors Branch 72
/\\UC 2 G 1981
- _f Division of Licensing 6
( v.3,uuan amu Office of Nuclear Reactor Regulation
,1,
/
U.S. Nuclear Regulatory Commis ion Washington, D. C.
20555 g
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License Docket No. 50-293 Additional Infornation Concerning NUREG 0619 Implementation of Unresolved Safety Issue A-10, BWR Re:
Nozzle Cracking
Dear Sir:
This letter responds to the request for additional information contained in your letter of June 4, 1981.
Recuest:
(1)
"C; der Generic Letter 81-11 (2/20/81) prior to modifying F. W. bypass regulating valve."
Response
Boston Edison (BEco) will consider the guidance provided by Generic Letter 81-11.
As part of this consideration, we shall examir.e the specific applicability of BECo shall General Electric's generic fracture mechanics analysis to PNPS.
undertake a plant-specific analysis should GE's prove inapplicable.
Re_ quest:
" Commit to review and upgrade procedures, as practicable, in accordance with (2) the guidance of Paragraph 4.4.1.2.2 of NUREG-0619.
_R.espons e :
feedwater modifications to which we are committed are completed, BECo When tr shall review and upgrade procedures, as practicable, in accordance with the fON U
guidante of paragraph 4.4.1.2.2 of NUREG-0619.
.s
/O 0108270636 810821 PDR ADOCK 05000293 P
- f. CD TON EDIZON COM PANY o
Mr. Thomas A. Ippolito, Chief August 10, 1981 Page 2 Request:
(3)
"With regard to the control rod drive return line nozzle modifications, your letter is not complete with respect to your commitment to follow the guidance of Paragraph 8.2 (2) or 8.2 (3), depending on your decision to operate with or without flow through the re-routed line".
Response
BECo is currently evaluating whether to operate with or without flow through the rerouted line. We expect this evaluation to be completed by October 1,1981, at which time we shall submit our chMen operational mode and the entailed commitments to be completed by June 30, 1983.
Request:
(4)
"We will also need your justification for an extension of the completion of control rod drive system modifications to June 30, 1983 since the staff has requested a completion date of June 30, 1982 in NUREG-0619".
Response
An extension of the implementation deadline to June 30, 1983 would make the CRD system modifications concommitant with modifications to the feedwater system.
We believe that this correspondence of related modifications will contribute to a more thorough, comprehensive and coherent resolution of the involved issues.
The concern regarding vessel nozzle cracking was that the cracks found in the nozzles of operating reactors present a potential safety problem. The observed rate of crack growth with the time in service was such, that the margin of l
safety against fracture might be reduced below acceptable values unless the cracks were detected and repaired.
CRDRL nozzle cracking is the result of high-frequency thermal cycling which j
occurs during normal operation. This thermal cycling is due to the tur-I bulent mixing of hot vessel water with lower temperature water entering through j
the nozzle. Crack propagation was the result of low-cycle fatique caused by
(
startup/ shutdown thermal and pressure cycles, and from flow changes during l
PNPS has completed modifications that eliminated CRDRL return flow, thereby eliminating the cracking problem. The remainder of the system modifications outlined in Part II of NUREG-0619 are to assure the long term operation of the L
CRD system by mitigating corrosion induced system degradation.
In summary, the public health and safety was potentially compromised only by the nozzle cracking problem, and then only after undetected cr'2s had propagated to such an extent that safety margins would be violated.
l PNPS perfonned a dye penetrant test and elimiated all existing cracks at the time of CRDRL reroute. By rerouting the CRDRL we have also eliminated the cause of crack initiation.
COIJTD,N 'EDIE DN COMPANY j
Mr. Thomas A. Ippolito, Chief July 31,1981 i
Page 3 Therefore, we do not believe that the public health and safety would in any way be compromised by the requested deadline extension.
Request:
(5) " Finally, with regard to both the feedwater nozzles and control rod drive system, we need your commitment to perform inspections, demonstrations and testing in accordance with Table 2 and paragraphs 8.2 (2) and 8.2 (3) of NUREG-0619".
4
Response
BECo is committed to perform the inspections and testing as described in Table 2 of NUREG-0613.
As stated previously, BECo has not completed the engineering evaluation of whether to operate the CRDRL with or without flow. Once this determination is made, w.2 shall supply our commitments to the requirements of the appropriate paragraph (8.2 (2) or 8.2 (3)) of NUREG-0619.
We believe that this response satisfactorily addresses your request for additional information concerning NUREG-0619. Should you have further questions, please-contact us.
4 i
Very truly yours, 1
i I
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