ML20057C435
| ML20057C435 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 09/22/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20057C431 | List: |
| References | |
| NUDOCS 9309280367 | |
| Download: ML20057C435 (3) | |
Text
.
ps ascoq yq j,., 1 j E
UNITED STATES NUCLEAR REGULATORY COMMISSION
\\..v
,/
WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 144 AND 122 TO FACILITY OPERATING LICENSE NOS. DPR-70 AND DPR-75 PUBLIC SERVICE ELECTRIC & GAS COMPANY PHILADELPHIA ELECTRIC COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY SALEM NUCLEAR GENERATING STATION. UNIT NOS. 1 AND 2 DOCKET NOS. 50-272 AND 50-311
1.0 INTRODUCTION
By letter dated June 17, 1993, Public Service Electric and Gas (PSE&G or the licensee) requested an Emergency License Amendment for Salem Nuclear Generating Station (SNGS), Units 1 and 2, to the Updated Final Safety Analysis Report (UFSAR). This request concerns a change to the current licensing basis requirements to address a potential single failure identified in the Rod Control System (RCS).
Investigation of an RCS failure during the startup of Salem Unit 2 has determined that a single failure in the RCS may result in a single Rod Cluster Control Assembly (RCCA) withdrawal or an asymmetric RCCA withdrawal event.
The SNGS UFSAR presently states that multiple failures would be required for a single RCCA withdrawal to occur.
If the identified failure is a single failure, it has not been addressed in the current licensing basis.
Based on the information currently available, the identified failure is being treated as a single failure which would result in an Unreviewed Safety Question in accordance with 10 CFR 50.59. The current UFSAR analysis for RCCA single withdrawal at power indicates that localized Departure From Nucleate Boiling (DNB) would result.
This was acceptable because UFSAR Sections 4.3 and 15.3.5.1 describe single RCCA withdrawal events using the assumption that multiple failures would be required for a single RCCA withdrawal to occur.
If a single failure can cause a single RCCA withdrawal ce an asymmetric RCCA withdrawal, General Design Criterion (GDC) 25 which states, "The protection system shall be designed to assure that specified acceptabie fuel design limits are not exceeded for any single malfunction of the reactivity control systems such as accidental withdrawal (not ejection or dropout) of control rods," is not met.
9309280267 930922 PDR ADOCK 05000272 P
pop
. Furthermore, the identified potential single failure that could cause a single or multiple asymmetric rod withdrawal event without an urgent failure alarm involves a change to the current licensing basis for Salem Units 1 and 2, because UFSAR Section 15.3.5.1 states that a single RCCA withdrawal at power would result in an " urgent failure" and a rod " deviation alarm" on the control room console.
The staff determined that emergency approval of the potential unreviewed safety question was not required because there was no change to the technical specifications and, for the case of Salem, compliance with GDC 25 was shown.
Therefore, the request was processed on a non-emergency basis.
The licensee was notified of this determination before the restart of Salem, Unit 1 on June 19, 1993.
2.0 EVALUATION The licensee has provided a justification for restart and continued operation of Salem Units 1 and 2.
The basis for this justification includes an evaluation of the licensing basis safety analysis to account for the effects of the identified failure.
This evaluation demonstrated that no fuel design limits are exceeded for the affected transients, which is consistent with
)
i General Design Criterion 25.
UFSAR Chapter 15 accident events were examined for adverse impact resulting from the postulated rod control system single failure. The only previously j
analyzed event impacted is the Single RCCA Withdrawal At Power (UFSAR 15.3.5).
Multiple asymmetric RCCA withdrawals both at power and from subcritical have been evaluated based upon the postulated failure scenario. Analyses performed for Salem Units 1 and 2 showed that the single RCCA withdrawal at power event was determined to be bounded by a multiple RCCA withdrawal of two adjacent D-bank RCCAs at full-power. The multiple asymmetric RCCA withdrawal at power case was divided into three cases depending on the power level and the rods allowed to be inserted into the core in accordance with the rod insertion limits.
Above 68% power, since rod insertion limits allow only D bank rods to j
be inserted, any number of the nine D-bank rods could withdraw.
The most limiting case for the multiple asymmetric RCCA withdrawal was shown to be the withdrawal of two adjacent D-bank rods.
When more than two RCCAs are withdrawn, the maximum peaking factor would be reduced as a result of the flattened power distribution.
Between 15 and 68% power, D bank and C bank RCCAs are allowed to be inserted into the core.
Thus any combination of the nine D-bank and eight C-bank RCCAs could withdraw.
Explicit analyses for Units 1 and 2 showed that there is no combination of asymmetric withdrawals that is more limiting than the previously mentioned limiting case.
Below 15% power, where C bank and B bank rods are allowed to be inserted, any combination of the eight C-bank and B-bank RCCAs (4 for Unit 1 and 8 for Unit 2) could withdraw.
Again this case is bounded by the first case.
3 CiL l The standard NRC-approved methodology described in WCAP-9272 was used for this analysis. Consistent with the current licensing-basis analysis in UFSAR Section 15.3.5, no rod deviation or rod control urgent failure alarm or operator action was assumed. The analysis concluded that the DNB design basis was met for the limiting case.
The final case to be considered was the asymetric RCCA withdrawal from subcritical. Administrative measures are being imposed to preclude achieving criticality should an asymetric rod withdrawal accident occur.
This is being accomplished by maintaining the reactor coolant system boron concentration sufficient for the reactor core to remain subcritical even if all rods are postulated to spontaneously move to their fully withdrawn position.
In sumary, RCCA withdrawal events resulting from the potential single failure have been evaluated against the criteria in GDC 25. The Salem-specific analyses demonstrated that the DNB design limits for the fuel are met.
In addition, PSE&G has imposed compensatory actions including performing a new surveillance test prior to startup, and ensuring that operators are cognizant of the failure symptoms and applicable responses. This is considered an interim measure for Salem, Un.ts 1 and 2, pending completion of ongoing actions and industry initiatives to resolve this concern.
Based on the staff evaluation as detailed above, and compensatory measures relative to testing and operator training, combined with existing alarms and procedures, the staff concludes that startup and continued operation of Salem, Units 1 and 2, is acceptable.
3.0 STATE CONSULTATION
In accordance with the Comission's regulations, the New Jersey State official was notified of the proposed issuance of the amendments. The State official had no coments.
4.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32, and 51.35, an environmental assessment and finding of no significant impact have been prepared and published (58 FR 48904) in the Federal Reaister on September 20, 1993. Accordingly, based upon the environmental assessment, the staff has determined that issuance of this amendment will not have a significant effect on the quality of the human environment.
5.0 CONCLUSION
The Comission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the 1
public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendments will not be inimical to the comon i
defense and security or to the health and safety of the public.
l Principal Contributor:
M. Chatterton 1
Date: September 22, 1993