ML20056C323
| ML20056C323 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/10/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20056C322 | List: |
| References | |
| NUDOCS 9305180469 | |
| Download: ML20056C323 (3) | |
Text
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%,.... 4l SUPPLEMENTAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO OPERATOR ACTION TIMES DURING A STEAM GENERATOR TUBE RUPTURE HOUSTON LIGHTING & POWER COMPANY CITY PUBLIC SERVICE BOARD OF SAN ANTONIO CENTRAL POWER AND LIGHT COMPANY CITY OF AUSTIN. TEXAS DOCKET NOS. 50-498 AND 50-499 SOUTH TEXAS PROJECT. UNITS 1 AND 2 BACKGROUND The staff's Safety Evaluation (SE) dated April 20, 1992, indicated that Houston Lighting and Power Company's (HL&P) response to confirmatory issue 1 (NRC letter of March 30, 1987) was incomplete because operator response times were obtained for three operating crews rather than for all operating crews.
This issue was retained as an open item. HL&P's response to the open item by letter dated December 16, 1992 is discussed below.
EVALUATION The staff's evaluation contained in a letter dated March 30,1987, of the Westinghouse Owner's Group WCAP-10698 stipulates plant-specific criteria for assessing operator action times in the event of a steam generator tube rupture (SGTR). Those criteria were employed to evaluate the information provided by HL&P regarding operator action times during an SGTR at South Texas Units 1 and 2.
The evaluation is based on the following:
Criterion 1.
Provide simulator and emergency operating procedure training related to a potential SGTR.
The staff's SE dated April 20, 1992, concluded that HL&P had satisfied Criterion 1.
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[riterion 2.
Complete demonstration runs to show that the operator action times assumed in the SGTR analysis are realistic and achievable by plant operators.
9305180469 93051o PDR ADOCK 05000498 P
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' 1 In the staff's SE dated April 20, 1992, the staff indicated that HL&P had used the longest demonstrated crew times for each operator action as the assumed times (shown in Table 1 below) for the overfill analysis. The staff found that such an approach for SGTR analysis was acceptable.
However, only 3 of 10 operating crews participated in demonstration runs regarding the overfill scenario.
i The staff requested that the licensee submit to the NRC the demonstrated SGTR operator response times for the overfill scenario representing all of the current South Texas operators.
By letter dated December 16, 1992, HL&P submitted demonstrated operator response times representing all of the South 3
Texas Units 1 and 2 operators.
1 Table 1 OVERFILL SCENARIO l
ACTIONS (Assumed Times in Minutes) 1.
Identify and isolate ruptured 10 steam generator 2.
Initiate cooldown of reactor 4
coolant system l
3.
Initiate depressurization of 3
Initiate safety injection 2
j termination The data representing response times for all of the South Texas operators indicated that for three of the actions (i.e., actions 2-4 in Table 1) all of the demonstrated times by the ten operator crews were bounded by the assumed
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times. However, none of the ten operator crews identified and isolated the i
ruptured SG within the time originally assumed in the licensee's analysis.
HLs" completed a calculation to determine the effect of the slowest operator l
crew response time for action 1 on the licensee's SGTR analysis.
The calculation indicated the additional mass that would be added to the faulted i
SG based on the slowest operator response time and showed that sufficient margin existed in the licensee's analysis such that the SG would not overfill.
HL&P noted that the increase in operator response times is believed to result from operating procedure steps added since the initial timing of the cperators. The licensee, therefore, has completed procedure revisions to reduce operator response times.
On the basis of the above information and the actions taken to reduce operator l
response times, the staff finds that the licensee has satisfactorily addressed 1
Criterion 2 and the open item identified in the SE dated April 20, 1992.
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Criterion 3.
Complete demonstration runs to show that the postulated SGTR accident can be mitigated within a period of time compatible with overfill prevention, using design basis assumptions regarding available equipment and its impact on operator response times.
As noted above, the licensee reported in its letter dated December 16, 1992, that demonstrated times for the overfill scenario are bounded by the assumed operator response times except for the time to identify and isolate the ruptured SG.
Further, the licensee addressed the exception by performing a calculation which indicated that there is margin to SG overfill using the recent demonstrated time (i.e., the slowest time) for identifying and isolating the ruptured SC.
Based on the results of the licensee's calculation and the other information discussed under Criterion 2 above, the staff finds that the licensee has satisfactorily addressed Criterion 3.
Criterion 4.
If the emergency operating procedures (EOPs) specify SG sampling as a means of identifying the SG with the ruptured tube, provide the expected time period for obtaining the sample results and discuss the effect on the duration of the accident.
The staff's SE dated April 20, 1992, concluded that the licensee had satisfied Criterion 4.
CONCLUSION The staff has reviewed Houston Lighting and Power Company's responses regarding operator response times during an SGTR, and concludes that the licensee has satisfied all four criteria required to complete the staff's review.
Principal Contributor:
G. West Date: May 10, 1993
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