ML20054C404
| ML20054C404 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 03/31/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20054C403 | List: |
| References | |
| NUDOCS 8204210004 | |
| Download: ML20054C404 (3) | |
Text
.
o reeg
/
o UNITED STATES l 3 NUCLEAR REGULATORY COMMISSION n
{
WASHINGTON, D. C. 20555
\\....+/SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 59 TO FACILITY LICENSE NO. DPR-35 BOSTON EDIS0N COMPANY PILGRIM NUCLEAR POWER STATION DOCKET NO. 50-293 Authors: Kenneth T. Eccleston, W. Hazelton, B. Hardin 1.0 Introduction By letter dated April 3,1980, Boston Edison Company (the licensee) requested Technical Specification (TS) changes which reflected the fact that no credit for core spray heat transfer was assumed in the supporting LOCA analyses. The purpose of these requested TS changes and the accompanying analyses was to address concerns related to the discovery of crack-like indications observed on the Pilgrim core spray spargers during the 1980 refueling outage.
Improved lighting and inspection techniques were utilized during the 1981 refueling outage to produce better images to enable more detailed evaluation of the indications detected during the 1980 refueling outage.
Computer enhancement techniques were also employed to improve contrast and resolution of both the 1980 and 1981 video signals.
Based on the results of its subsequent evaluations, the licensee requested, by letter dated January 18, 1982, changes to the Technical Specifications l
to increase Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) l operating limits by taking credit for core spray heat transfer based on the i
licensee's conclusion that the core spray spargers are fully operational.
l The licensee concluded that structural integrity of the core spray spargers will be maintained through the next fuel cycle.
2.0 Evaluation 2.1 Core Spray Sparger Integrity Proceeding under the conservative assumption that the linear indications were actual cracks, a crack growth analysis using fracture mechanics l
l methodology was performed to assess the possible growth of the cracks assuming an intergranular stress corrosion cracking mechanism.
The results of the inspections and the crack growth predictions were presented by the licensee in a preliminary report, " Structural Evaluation of the Pilgrim Station Core Spray Spargers Based upon Results from the October 1981 Remote Visual Inspection." Major conclusions of the report are:
$$h00 0
P
^
2 1.
Six indications found during the 1980 inspection were resolved as not significant, because they were determined to be caused by grinding marks, other mechanical marks, or could not be found during the 1981 inspection.
2.
One area, described as "B header to pipe weld and the (adjacent) area to nozzle 25B" appears to have crack-like indications, but a comparison of the 1980 and 1981 video results do not show any evidence of propagation.
3.
The crack growth rate analysis supports the licensee's view that if cracks are present, further growth will be slow.
4.
The licensee concludes that the Core Spray Spargers are fully operational, and, based on the results of the evaluation description above, structural integrity will be maintained through the next fuel cycle.
We have reviewed the detailed submittals provided by the licensee and agree that continued operation is justified.
Our bases for this conclusion are:
1.
We agree that the improved inspection procedures and computer enhancement have shown that most suspicious areas and indications are unlikely to represent cracks.
2.
We also agree that the indication in the B header area have not changed significantly, if at all, from the 1980 examination. This finding is important, because it means either that the indications do not represent cracks, or if they are cracks, they are propagating at a slow rate.
3.
Because there is no evidence of highly active crack growth, it is unlikely that deleterious loss of structural integrity will occur during the next operating cycle.
Consequently, we conclude that credit for core spray heat transfer should be allowed during future operation; the continued integrity of the core spray spargers will be verified as a result of the ongoing inservice inspection program.
2.2 Increased MAPLHGR Operating Limits In order to satisfy the acceptance criteria of 10 CFR 50.46, MAPLHGR reduction factors were applied to each fuel type for Cycle 6 by assuming no credit for core spray heat transfer. These reduction factors were determined from the results of loss of coolant accident (LOCA) calculations performed both with and without core spray heat transfer.
Based upon the results of the most recent core spray sparger inspections, the licensee has requested revisions to its TS to restore credit for core spray heat transfer and to eliminate the MAPLHGR reduction factors for Cycle 6 operation.
3 We have previously reviewed the licensee's analyses applicable to Reload 5 (Cycle 6) operation including plant response to LOCA with benefit of core spray heat transfer in the safety evaluation supporting Amendment No. 54 to DPR-35, dated March 20, 1982. The results of these calculations show that the acceptance criteria of 10 CFR 50.46 are satisfied if no MAPLHGR reduction factors are applied and credit is given for core spray heat transfer.
Based on our review, we conclude that the LOCA calculations submitted for Cycle 6 operation (assuming credit for core spray heat transfer) satisfy the criteria of 10 CFR 50.46 and are therefore acceptable.
We have also reviewed the licensee's proposed changes to Technical Specifications involving the 3
increased fMPLHGR operating limits and conclude that these changes are in accordance with these calculations.
Consequently, we find them acceptable.
2.3 Summa ry Based upon our review of the licensee's submittals we find (1) that deleterious loss of core spray sparger structural integrity is unlikely to occur and that core spray heat transfer should be allowed for future operation 2) the LOCA calculations satisfy the criteria of 10 CFR 50.46 and 3) the licensee's proposed Technical Specifications are acceptable.
3.0 Environmental Considerations We have determined that the amendment does not involve a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 51.5(d)(4) that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
4.0 Conclusions We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not l
involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated: March 31,1982
- - - - - -