ML13331A531
| ML13331A531 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/31/1991 |
| From: | Morgan H Southern California Edison Co |
| To: | NRC/IRM |
| Shared Package | |
| ML13331A533 | List: |
| References | |
| NUDOCS 9102040264 | |
| Download: ML13331A531 (3) | |
Text
Southern California Edison Company P. 0.
BOX 128 SAN CLEMENTE, CALIFORNIA 92672 H. E. MORGAN TELEPHONE VICE PRESIDENT AND SITE MANAGER 714-368-9470 SAN ONOFRE January 31, 1991 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Amendment Application No. 189, Supplement 2 ECCS Actuation Logic and Vital Bus Transfer San Onofre Nuclear Generating Station, Unit 1 Enclosed is Supplement 2 to Amendment Application No. 189 for the San Onofre Nuclear Generating Station, Unit 1 (SONGS 1).
This supplement provides additional information concerning Technical Specification changes that were proposed by the original Amendment Application 189 (dated September 28, 1990) and Supplement 1 to the amendment application (dated January 14, 1991).
That amendment application and supplement were submitted to:
- 1) reflect changes to the Technical Specifications resulting from resolution of single failure susceptibilities of the 4160 volt electrical distribution system and the Safeguards Load Sequencing System (SLSS), and 2) propose a license condition to require resolution prior to Cycle 12 operation of a single failure susceptibility concerning vital electrical bus automatic transfer.
This supplement concerns only item 1 above. The proposed license condition for resolution of the vital bus automatic transfer issue remains unchanged.
This supplement provides the specific setpoint/response time curve for Specification 3.5.1 for the 4160 volt bus undervoltage reactor trip instrumentation channels. The curve has been confirmed by recent tests on the associated relays presently installed in the plant. The significant hazards analysis presented in Supplement 1 to this amendment application is unaffected by this supplement.
BACKGROUND The proposed Technical Specification changes previously submitted by Amendment Application 189, in conjunction with plant modifications being performed during the current refueling outage, will resolve Open Issue No. 8, Sequencer Logic Deficiency, that was identified in the Emergency Core Cooling System 91020'4026~4 910131 PE)
PPUL.O5Q2'
Document Control Desk January 31, 1991 Single Failure Analysis Interim Report dated July 31, 1990. During the review of that amendment application, the NRC requested additional information concerning the submittal. Supplement 1 to the amendment application provided the requested information.
However, one of the requested items could not be included in Supplement 1 in sufficient time to support expedited NRC review of the amendment. We committed in the supplement to provide the one remaining item, i.e., the setpoint/response time curve for the 4160 volt undervoltage reactor trip channels.
SETPOINT/RESPONSE TIME CURVE A new proposed Technical Specification Figure 3.5.1-1 is enclosed to replace the typical setpoint/response time curve for the 4160 volt bus undervoltage reactor trip channels that was included in Supplement 1. The curve provided in that supplement was included for information while the final curve was being developed. The accuracy of the new curve has been recently confirmed by tests conducted on the specific relays used in the undervoltage reactor trip circuitry. Double revision bars in the left margin of the enclosed proposed Technical Specification page indicate changes made in the curve since submittal of Supplement 1.
BASIS FOR SETPOINT/RESPONSE TIME CURVE The 4160 volt bus undervoltage relays provide inputs for reactor trip and the loss of power (LOP) signal to the SLSS. The reactor trip function of the undervoltage relays is a balance-of-plant feature and is not credited in any of the Chapter 15 safety analyses. The trip settings specified by Figure 3.5.1-1 are derived from the actual expected component performance characteristic including acceptable tolerances. The one second time delay at zero volt allows for voltage dips due to feeder short circuit fault clearing without causing a spurious reactor trip.
In addition, to preclude inadvertent actuation of the undervoltage relay during the anticipated range of voltage variations (e.g., degraded grid, load sequencing), the relays are set for a maximum pickup voltage of 71% of the nominal bus voltage. This setting is four percent lower than the minimum bus voltage expected during voltage variations (75% of nominal bus voltage).
The relays also provide input to the SLSS to generate a SISLOP signal.
The need for these relays to actuate on a loss-of-power for input to the sequencers is based on providing an LOP signal prior to the need to automatically load the diesel generators during a SISLOP. The diesels are automatically started at the beginning of the SISLOP by the SIS or LOP signals. The diesels are required to automatically load within 10 seconds after a SISLOP. As specified in Figure 3.5.1-1, the 1.0+/-0.1 second response time (i.e., the zero voltage trip setting in the figure) provides adequate margin to provide the LOP signal to enable diesel generator breaker closure and subsequent diesel generator loading.
Document Control Desk January 31, 1991 The setpoint/response time curve for these channels is proposed for inclusion in Specification 3.5.1, Reactor Trip Instrumentation, even though the timing requirements embodied by the.curve are also required by the engineered safety feature (ESF) functions of the SLSS. The curve was included at this location in the Technical Specifications for convenience since the format of the SONGS 1 Technical Specifications does not correspond to that of the Standard Technical Specifications for Pressurized Water Reactors, NUREG-0452.
This supplement fulfills our commitment to provide the setpoint/response time curve for the 4160 volt bus undervoltage reactor trip channels. As stated in our letter dated January 14, 1991, on this subject, NRC approval of Amendment Application 189 (as amended by Supplements 1 and 2) is needed prior to entering mode 4 (scheduled for February 20, 1991).
Therefore, we request expedited approval by February 13, 1991, to allow time to complete our administrative process after receipt of NRC approval.
Please let us know if a meeting with your staff would be of assistance to your review.
Very truly yours, Enclosure cc:
J. B. Martin, Regional Administrator, NRC Region V C. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3 C. D. Townsend, NRC Resident Inspector, San Onofre Unit 1