ML20077F429
| ML20077F429 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 07/26/1983 |
| From: | Harrington W BOSTON EDISON CO. |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0619, RTR-NUREG-619 83-196, NUDOCS 8308010379 | |
| Download: ML20077F429 (3) | |
Text
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BOSTON EDISON COMPANY a
800 BOYLETON STREET BDaTDN, M AsBACHUBETTs D2199 WILLIAM D. HARRINGTON season venE peaseosur as W C LEAR July 26, 1983 BECo Letter No.83-196 Mr. Domenic B. Vassallo, Chief Operating Reactors Branch #2 Division of Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555 License No. DPR-35 Docket No. 50-293
Subject:
NUREG 0619 "BWR Feedwater Nozzle and Control Rod Drive Return Line Nozzle Cracking" Refererces:
(A) NRC Letter dated November 13. 1980 (B) BEco Letter dated February 3,1981 (C) HRC Letter dated June 4, 1981 (D) BEco Letter dated August 21, 1981 (E) BEco Letter dated September 22, 1982
Dear Sir:
This submittal is to provide an updated report on Boston Edison Company's imple-mentation of NUREG-0619 guidance, describe BECo's selected Control Rod Drive (CRD) return line option, advise the NRC of proposed changes in BECo's earlier conunitments, and request NRC review and concurrence.
NUREG-0619 was issued with Reference (A) in rasponse to the discovery of cracks in BWR feedwater (FW) and CRD nozzles.
The document identified causes of the cracking, together with suggested means'of mitigating the problem. BECo responded in Reference (B), committing to re-route the RWCU return flow to all FW nozzles, modify the low-flow FW controller, install equalizing valves in the CRD system and replace carbon steel piping in the stabilizing loop if CRD return line flow was not maintained, or. install a pressure-control station if flow was maintained.
Following your review of ' Reference (B), you recommended via' Reference -(C) that BECo take advantage of = analysis' which might demonstrate the adequacy of. the existing low flow FW control, and thereby obviate the need fo. modification in.
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this-area.- The reference also requests a BECo commitment to ' review and upgrade procedures per paragraph 4.4.1.2.2 of NUREG-0619, advise NRC whether BECo intends to operate the re-routed CRD return line valved-open or closed, and commit to inspect and test nozzles per Table 2 of the NUREG.
In Reference -(D), BECo acknowledged the recommendations,' and modified its commit-ments to consider the' guidance of Reference (C). ' In._the.~ same ~. reference, BECo 8308010379 830726 M
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.l committed to review and upgrade procedures as practicable, per Paragraph 4.4.1.2.2 l
dnd to notify NRC by October 1,1981 concerning the chosen arrangement for the CRD return line.
Also, BECo committed to perform nozzle inspections and testing per Table 2 of the NUREG.
In Reference (E), BECo revised its scheduled completion of NUREG-0619 compliance i
modifications to coincide with planned refueling outage dates. Since BECo's last communication on this topic, additional research has uncovered the need to further modify the implementation program.
In connection with FW nozzles, NUREG-0619 recommends nozzle clad removal, instal-lation of improved-design spargers, re-routing of RWCU return to all FW nozzles, installation of a new low-flow FW controller, and new operating and inspection procedures. Further, it suggests installation of thermal sleeve bypass monitors as a means of detecting the efficacy of thermal sleeve seals in preventing rela-l tivity cool FW from contacting hot nozzle surfaces.
Of the items suggested by NUREG-0619, BECo has cowleted clad removal, installa-tion of imoroved-design spargers, and implementation of new inspection procedures.
Following clad removal, all four FW nozzles were PT-inspected and found to be free of cracks. The recommended changes in operating procedures have been noted, and j
they will be implemented'as soon as practicable. The thermal sleeve bypass moni-tor has been avaluated, and a decision has been made not to install them at this time.
BECo has committed to re-route the RWCU return flow, and to install the new low-flow FW controller if _ the analysis recommended by NRC in R_eference (C) demon-strated the necessity of doing -so.
As of. this writing, the analysis has been completed and it' indicates that neither the RWCU re-route nor. the new low-flow FW controller is necessary.
Hence, our position on these items, as stated in reference (B), has been re-evaluated and we are retracting these commitments.
2 We request that-you review our revised position on these-items and advise us of its acceptability.
4 In connection with the CRD return.line nozzle, NUREG-0619 recommends inspection of bores and removal of cracks,-plus one of the following return ~line treatments:
1.
Valve out the. return line.
2.
Re-route the return line to another-system.
-3.
Cut and cap'the return line.
We have completed the' inspection of_ the nozzle bores and'have not discovered any cracking. We have also cut and capped the CRD return line.
NUREG-0619 also recommends that equalizing. valves be installed between the cool-
.ing1 water header and the -exhaust water. header, that the -carbon steel piping in the stabilizing loop be replaced with stainless steel > piping and that the exhaust water header piping be is'imilarly replaced with stainless steel (or alternatively,.
install; flush and drain ports).
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,Mr. 00menic B. Vassallo, Chief Page 3 As scheduled, we will complete the installation of the equalizing valves and the installation of the flush and drain ports in,the exhaust water header piping during RF0 46.
However, we have re-evaluated our commitment to replace the stabilizing loop piping and have concluded that it is not necessary. Our analysis indicates that the same purpose (minimization of corrosion products being gener-ated) can be achieved by simply valving out the stabilizing loop.
Our reconsidera-tion further shows that since the CRD return line has been cut and capped, the stabilizing loop and valves serve no functional purpose and therefore can be isolated.
Completion of the program discussed above will constitute completion of Boston Edison Company's implementation of the provisions of NUREG-0619; please review it and apprise us of its acceptability.
It would aid us greatly if you would respond to this request at your earliest con-venience, because the approach of RF0 #6 and the integration of tasks into a long range plan mandate early identification of any required changes.
We appreciate your attention to this issue.
If you require any further informa-tion, please contact us.
Very truly yours,
.