ML18139B667
| ML18139B667 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 12/31/1981 |
| From: | Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Harold Denton, Varga S Office of Nuclear Reactor Regulation |
| References | |
| 233A, NUDOCS 8201070010 | |
| Download: ML18139B667 (3) | |
Text
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e VIRGINL:\\. ELECTRIC AND POWER COMPANY RICHMOND,,. VIRGINIA 23261 R, H. LEASBURG VxoE PRESIDENT NUCLEAR 0PERATXONS December 31, 1981 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation Attn: Mr. Steven A. Varga, Chief Operating Reactors Branch No. 1 Division of Licensing U.S. Nuclear Regulatory CoITUllission Washington, DC 20555 Gentlemen:
GENERAL DESIGN CRITERIA 17 ANALYSIS SURRY POWER STATION UNIT NOS. 1 AND 2 Serial No. 233A PSE&C/KSB Docket Nos. 50-280 50-281 License Nos. DPR-32 DPR-37 In our letter to you dated May 26, 1981, Serial No. 233, we informed you of our GDC 17 analysis progress to that point in tine and of our course of action for completing the analysis.
We believed we could develop a final decision on the permanent solution and submit this solution and supporting analysis to you by late 1981.
Due to unforseen problems, our analysis is not complete at this time.
The purpose of this letter is to inform you of our current status and expected completion date.
The scope of our analysis is based on all the guidelines and requirements set forth in the NRC' s August 8, 1979 letter, entitled "Adequacy of Station Electrical Distribution System Voltages".
Our scope includes those guidelines which are general in nature from the NRC's June 25, 1980 letter concerning our North Anna Power Station.
While the June 25, 1980 letter was directed at North Anna, we believe these guidelines should also apply to Surry.
We are analyzing the normal and reserve Station Service electrical system.
The Reserve Station Service (RSS)
System at Surry supplies the emergency buses and the intake structure buses (supplied at the 34.5 KV level) at all times.
It also supplies all unit auxiliaries required during a start up, until these loads are manually transferred to the normal Station Service System.
In the case of a unit trip, all loads on the normal Station Service System are automatically transferred to the RSS System.
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e VIRGINIA ELECTRIC AND PoWEH COMPANY TO Mr. H. R. Denton In the event of two unit simultaneous loading on the RSS System, an automatic load shedding scheme sheds non-safety related loads from both units.
The following operating precautions are normally in effect as required to implement the automatic load shed scheme:
Unit 1
- 1.
Operating procedures have "A" FW pump running during unit start up and when on the line.
- 2.
Operating procedures have "B" or "C" condensate pump running during unit start up and when on the line.
Unit 2
- 1.
Operating procedures have "B" FW pump running during unit start up and when on the line.
- 2.
Operating procedures have "A" or "B" condensate pump running during unit start up and when on the line.
A manual override switch is provided in the control room to allow manual restarting of the shed loads under a controlled condition.
Within 20 minutes after two unit simultaneous loading occurs on the RSS System, an operating procedure is implemented to insure that a sufficient amount of non-safety related load is manually shed to reduce the loading of the switchgear to within its continuous rating.
As discussed in our May 26, 1981 letter, the original design basis for the RSS System was for it to be capable of handling the loads required for one unit to start up, or to handle the load automatically transferred in the case of a unit trip.
Our GDC-17 analysis includes worst case conditions of two unit loading on the RSS System as well as worst case conditions of single unit loading on the RSS System.
These cases include two units tripping both with and without one unit experiencing a Consequence Limiting Safeguard (CLS) action, one unit in start up and the other unit tripping both with and without a CLS, and one unit operating at 100% power and the other unit tripping both with and without a CLS.
We have reviewed our electrical distribution system to determine whether any events or conditions exist which could result in the simultaneous or consequential loss of both required circuits to the off site network.
This review has indicated we must implement several minor
- rrodif ications (administrative control of several sets of 34.5 Ki/ disconnects, and low voltage cable relocation in the station service switchyard) to ensure compliance with GDC-17 in this regard.
These modifications will be completed in 1982.
e VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. H. R. Denton Our equipment rating determination is complete with the exception of the ratings for the 4KV underground cable between the Reserve Station Service Transformers and the 4KV transfer bus switchgear.
Additionally, we are investigating with the manufacturer of our notor operated valves (MOV' s) certification of MOV's which receive either a Safety Injection (SI) or a CLS signal to start on a minimum voltage of 80% of rated voltage.
Our steady state equipment overload analysis is currently being revised and requires the cable ratings discussed in the preceding paragraph.
Preliminary results indicate that for the very conservative worst case loading on each individual reserve transformer, there exists the potential for overloading the 4KV transfer bus switchgear and one Reserve Station Service Transformer.
Based on the worst case overload of the 4KV transfer bus switchgear and calculations completed in accordance with ANSI C37.010-1979 Section 4.4.3.3.1, operator action to reduce loading on the switchgear to within its continuous rating within 20 minutes after the occurrence of the overload condition assures the loading profile on the switchgear is within the rating of the switchgear.
The reserve station service transformer overload, which,is less severe than the switchgear overload, will be removed by this operator action.
our voltage analysis is presently incomplete.
Our major delay has been ensuring that the MOV' s which receive either a SI or CLS signal have sufficient voltage to start and complete valve movement.
We are presently continuing our analysis on the basis that the MOV' s will be rated for 80%
voltage starting.
This is in a parallel path with the MOV vendor evaluation, which we are expediting.
In our May 26, 1981 letter to you, we discussed the pending emergency bus undervoltage protection modification.
The nodification has been completed on Unit 2 and will be completed on Unit 1 in 1982.
Our voltage analysis includes this new protection.
A detailed analysis will be presented in our final submittal.
Assuming a timely response from the MOV manufacturer, our final submittal, including equipment ratings, assumptions, results, and identification of any required :rrodifications, will be made by March 31, 1982.
Although we have postponed our analysis submittal date, it is still our intent to complete all required modifications in 1982.
Please contact us if you require further information prior to our final submittal.
R.H. Leasburg cc: Mr. J.P. O'Reilly, Regional Administrator Office of Inspection and Enforcement Region II