ML18153A807
| ML18153A807 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/28/1995 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 95-036D, 95-36D, NUDOCS 9505050312 | |
| Download: ML18153A807 (5) | |
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 28, 1995 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.
NL&P/CGL Docket Nos.
License Nos.
CORE UPRATE - INSTRUMENTATION AND CONTROL BRANCH REQUEST FOR ADDITIONAL INFORMATION 95-036D RO' 50-280 50-281 DPR-32 DPR-37 The Surry Core Uprate Technical Specification change request was submitted for NRC review by an August 30, 1994 letter (Serial No.94-509).. On March 2, 1995, we received a request for additional information from the Instrumentation and Control Branch (HICB) of NRR regarding our core uprate submittal. The HICB questions and our responses are documented in Attachment 1.
Very truly yours, f;>c/d~J~
James P. O'Hanlon Senior Vice President - Nuclear - Responses to HICB Request for Additional Information Regarding Proposed Technical Specification Changes to Accommodate Core Uprating - Surry Power Station Units 1 and 2 cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Commissioner Department of Radiological Health Room 104A 1500 East Main Street Richmond, Virginia 23219
.9505050312 950428 PDR. ADOCK 05000280
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ATTACHMENT 1 Instrumentation and Controls Branch (HICB)
Request for Additional Information Surry Power Station Units 1 and 2 Proposed Technical Specification Changes to Accommodate Core Uprating 1.
There are changes in the Reactor Trip Setpoints given in Table 4.7.1-1.
However, the Technical Specifications have not been changed.
Justify.
RESPONSE
Table 4.7.1-1 of the Surry Core Uprate Licensing Report compares the current limiting instrument settings and uprating analysis values for key Reactor Protection System and Engineered Safety Features Systems. Although Section 4.7.1 (p. 329) of the Surry Core Uprate Licensing Report states that the revised Technical Specifications functions are noted on Table 4.7.1-1, specific indication of what had been revised was inadvertently omitted from the table. However, Section 4.7.1 discusses the functions for which Technical Specifications changes were required (Overtemperature ~ T, Overpower ~T. and Recirculation Mode Transfer (RMT)).
Of the existing limiting settings presented in Table 4.7.1-1, only those three require revised Technical Specifications (TS) and they were included in our August 30, 1994 TS change request.
Table 4. 7.1-1 (Revision 1), which is attached, has been revised for clarification. The following changes have been made to Table 4.7.1-1:
Identification of the source of 'Current Limiting Settings' (i.e., TS or Precautions, Limitations, and Setpoints (PLS) Document)
Identification of 'Uprating Analysis' values which differ from existing values Addition of entries for RMT function Revision of entries for 'Uprating Analysis', High-High Steam Generator (SG) Level Revision of entry for 'Uprating Analysis', High Pressurizer Level-Reactor Trip Identification of items for which TS changes are proposed for uprated operation Footnote 1 of Table 4.7.1-1 (Revision 1) indicates that the assumed parameter value associated with the following functions has been revised for the uprating analysis:
High-High SG Level - Turbine Trip High-High SG Level - Feedwater Isolation RMT - Maximum and Minimum Allowed Setpoints High Pressurizer Level - Reactor Trip Each of these functions is described in the following paragraphs.
High-High SG Level - Turbine Trip and Feedwater Isolation - The uprating analysis assumes a value of 96% narrow range span for these functions. The existing limiting setting, found in the PLS document, is 75% span. It has been confirmed that the difference between the revised analysis value and existing limiting setting provides adequate allowance to accommodate the channel uncertainty and other margin components. Therefore, no change in the existing limiting setting is required.
1 - 1
RMT - Maximum and Minimum Allowed Setpoints - The uprating analysis assumes RMT occurs between a maximum value of 15.75% span and a minimum value of 11.25% span. The nominal RMT setpoint was placed at 13.5% span, which is the midpoint of the analyzed range. This change was necessary to obtain acceptable results in the containment integrity and safeguards components analyses described in Section 3.6.2 of the Surry Core Uprate Licensing Report. The proposed TS maximum and minimum setpoint limits were selected to provide adequate allowance with respect to the nominal setpoint to accommodate the channel uncertainty and other margin components. The TS change request documents the revised TS setpoint limits.
High Pressurizer Level - Reactor Trip - The uprating analysis assumes a value of 100% span for this function. The existing limiting setting, found in the TS, is 92% span.
It has been confirmed that the difference between the revised analysis value and existing limiting setting provides adequate allowance to accommodate the channel uncertainty and other margin components.
Therefore, no change in the existing limiting setting is required.
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Table 4.7.1-1 (Revision 1)
Assumed Reactor Protection & Engineered Safety Features Settings for Surry Core Rated Power of 2546 MWt PARAMETER VALUES Current Uprating Limiting Setting FUNCTION Engineered Safeguards Turbine Trip Limiting Settings Analysis Source Document High-High SG Level (% NRS)
Feedwater Isolation High-High SG Level (% NRS)
Accumulator N2 Pressure (psia)
Safety Injection Low Pressurizer Pressure (psia)
High Containment Pressure (psia)
Recirculation Mode Transfer, RMT (% span)
Maximum Allowed Setpoint Minimum Allowed Setpoint Reactor Trips High Flux - Hi Setting(% RTP)
High Flux - Lo Setting(% RTP)
Low Pressurizer Pressu*re (psia)
High Pressurizer Pressure (psia)
High Pressurizer Level (% span)
Low RCS Flow (% nominal)
RCP Underfrequency (Hz)
RCP Undervoltage (% nominal)
Overtemperature L'.1T1,3 Overpower i1T Low-low SG Level (% NRS) 75 75 600 1715 19.7 19.43 18.93 109 25 1875 2400 92 90 57.5 70 K1=1.135 K4=1.089 5
961,5 580 1715 21.7 15.751 11.251 118 35 1865 2425 1001,5 872 not credited not credited K1 =1.232 not credited 0
PLS PLS TS TS TS TS TS TS TS TS TS TS TS TS4 TS4 TS 1 Indicates a value or assumption which differs from-that of existing analysis 2 Analysis assumes 87% of minimum RCS total flowrate of 91,000 gpm/loop 3 Analysis supports existing TS values for Kandt constants; the term T' is revised to 573.0°F to reflect nominal full power T avg 4 TS changes for this item are proposed in the uprating TS change request 5 Revised from the value in August 30, 1994 uprate submittal to more accurately reflect the assumption in the accident analysis 1 - 3
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QUESTION:
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What setpoint methodology was used to determine the new trip setpoint values?
Discuss this methodology and provide a sample calculation for the Auto Recirculation Mode Transfer (page 330/TS page 3.7-26).
RESPONSE
For the changes in Overtemperature ~ T and Overpower ~ T functions, the Westinghouse methodology employed is documented in WCAP-87 46-A, entitled "Design Bases for the Thermal Overpower ~T and Thermal Overtemperature ~T Trip Functions," dated September 1986. The development of the Recirculation Mode Transfer (RMT) function is illustrated below.
A key component of the setpoint methodology is the calculation of channel statistical allowance (CSA). The method employed for calculation of CSA has been presented to NRG on several occasions during NRG inspections for review and use, most recently during a special announced inspection of Surry Plant Instrumentation Setpoints in January 1993 (documented in NRG Inspection Report 93-01 dated February 23, 1993). The CSA methodology involves statistical combination of independent, random components of uncertainty summed with dependent, nonrandom components to obtain an overall assessment of total channel uncertainty. Using this setpoint methodology, the difference between the actual protection function trip setpoint and the assumed actuation value for the function in the safety analysis must be greater than or equal to the CSA. For the RMT channel, the calculated CSA is 1.78% span. The manner in which the CSA is applied to the RMT function is illustrated below. There is a total tolerance of 2.25% span between either the upper or lower safety analysis assumed actuation value or limit and the nominal setpoint.
SAFETY ANALYSIS ASSUMED ACTUATION VALUE (UPPER)-----------------------
15.75% span I
CSA (1.78%)------- I I
Setpoint + Margin ------------------------------------ 13.97% span NOMINAL SETPOINT -----------------------------------
13.50% span Setpoint - Margin ------------------------------------- 13.03% span I
CSA (1.78%)------- I I
SAFETY ANALYSIS ASSUMED ACTUATION VALUE (LOWER) -----------------------
11.25% span 1 - 4