ML20137L417
| ML20137L417 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/03/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20137L409 | List: |
| References | |
| NUDOCS 9704070221 | |
| Download: ML20137L417 (3) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION
\\*****lg WASHINGTON, D.C. 20606 4001 o
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 158TO FACILITY OPERATING LICENSE NPF-35 AND ACENDMENT NO. 150 TO FACILITY OPERATING LICENSE NPF-52
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CATAWBA NUCLEAR STATION. UNITS 1 AND 2 l
DOCKET NOS. 50-413 AND 50-414 j
1.0 INTRODUCTION
By letter dated January 3,1997, Duke Power Company, et al. (the licensee),
j submitted a request for changes to the Catawba Nuclear Station, Units 1 and 2, Technical Specifications (TS).
Specifically, the licensee proposed to (1) revise the Technical Specifications, Table 3.3-2, 3.3-4, 3.3-5, 4.3-2 and Bases Section 3/4.3.1 and 3/4.3.2 to eliminate the safety injection signal on low steam line pressure. The initial request was supplemented by a letter dated March 20, 1997, responding to the staff's request for additional information dated March 18, 1997.
2.0 DISCUSSION AND EVALUATION The safety injection (SI) system is designed to provide borated makeup water during loss of coolant accidents as well as cooldown accidents such as steamline breaks.
It is the licensee's goal to minimize unnecessary actuation of the SI system since the introduction of cold water into the primary coolant system can lead to an increase of reactor thermal power, resulting in a thermal transient and pressurization of the reactor coolant system. An added concern to the licensee is that the unnecessary addition of highly borated water into the core could create challenges to plant safety equipment.
The licensee has determined that removing the SI signal on low steamline 4
pressure will limit the number of unnecessary SI actuations. To determine that the removal of the SI actuation on low steamline pressure would not i
adversely impact the safe operation of the plant, the licensee used staff-approved methodologies to evaluate each of the Updated Final Safety Analysis Report (UFSAR), Chapter 15 transient analyses.
The results of the evaluation determined that the transient analyses fall into three categories: (1) transients which do not involve automatic SI actuation, (2) transients with automatic SI actuation, but initiated by a signal other than low steamline pressure, and (3) transients which involve SI actuation on low steamline pressure. Those transients that involve a significant decrease in steamline pressure were further evaluated or reanalyzed by the licensee.
9704070221 970403 DR ADOCK 0500 3
The purpose of the steamline break analysis is to demonstrate short-term core cooling capability in the event of a steamline break transient. During the licensing review, a spectrum of break sizes were analyzed and documented in the Final Safety Analysis Report (FSAR) for the steamline break transient to determine the most limiting break size. Thelicenseereanalyzedthisevgnt andfogndthatthelimitingbreaksizesremainedthesameandare1.4ft and 2.0 ft for Catawba Units 1 and 2, respectively.
The licensee determined that for the smaller breaks the SI will actuate on low pressurizer pressure before reaching the setpoint for.SI actuation on low stgamline>ressure. On the other han4 for larger breaks (greater than 2.5 i
- ft for Unit I and greater than 1.4 ft for Unit 2) the SI will reach the low '
i steamline pressure actuation.setpoint before reaching the low pressurizer l
l pressure SI actuation setpoint. Thus, removing the low steamline pressure signal will delay SI actuation until the low pressurizer pressure setpoint is reached. The licensee reanalyzed the larger breaks with the SI actuation on-low steamline pressure removed..The results showed that the minimum departure from nucleate boiling ratio (DNBR) remains above the regulatory DNBR limit of 1.3, with sufficient margin to conclude that the acceptance criteria for steamline break transient continues to be met with the removal of SI actuation on low steamline pressure.
i The licensee evaluated the mass and energy release analysis for a steamline break inside containment to demonstrate that the condition inside containment does not exceed the existing environmental qualification envelope during a i
steamline break.
In this case, regardless of the break size, the SI will actuate on high containment pressure prior to reaching the setpoint for SI actuation on low steamline pressure. Therefore, the removal of the low steamline )ressure SI actuation signal does not have any effect on the steamline areak mass and energy release as previously reported in the FSAR and UFSAR.
The worst-case scenario for loss of alternating current (AC) power transient results in no primary or secondary depressurization and therefore no SI j
actuation.. However, in the less limiting case, there is the possibility of primary and secondary depressurization due to excessive auxiliary feedwater i
delivered to the steam generators, compounded by extraction steam loads and the possibility of open steamline drains. The licensee has changed the plant's emergency procedures to include throttling the auxiliary feedwater in the event that 6.9-kV power is unavailable. This prompt operator action will reduce reactor cooling system overcooling and thereby avoid an unnecessary SI actuation.
If the throttling action does not occur and overcooling follows, SI actuai; ion on low pressurizer pressure is still available if needed.
l The feedwater line break is analyzed to demonstrate long-term cooling and the analysis is required to postulate the break only at the terminal ends of the i
feedwater piping.
For a feedwater line break at the main feedwater pumps, the check valve will prevent depressurization of the steam generator.
For a j
feedwater line break at the-steam generator, SI actuation occurs on high containment pressure. Therefore, the elimination of the SI actuation on low 1
steamline pressure does not adversely impact the feedwater line break transient'as reported in the UFSAR.
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In summary, the licensee's reanalysis or evaluation led to the conclusion that i
only those transients which involve a secondary system depressurization have the potential to be affected by the elimination of the SI signal on low steamline pressure. For all other transients in which SI actuation occurs, the initiating signal is low pressurizer pressure or high containment pressure, and are thus not affected by the proposed change. Thus all previous acceptance criteria will continue to be met. The staff has reviewed the licensee's submittals and agrees with tLe licensee's findings. The staff i
finds the licensee's proposed changes to the Technical Specifications and j
Bases, as conveyed in the licensee's January 3,1997, letter acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restrict area as defined in 10 CFR Part
?O. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant inciease in individual or cumulative occupational radiation exposure. The staff has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such' finding (62 FR 4345 dated January 29,1997).
The licensee's Marh 20, 1997, submittal only provides supplemental information and does not change the original amendment request. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22 (c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Sarita B. Brewer Date: April 3, 1997
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