ML18153A712

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Application for Amends to Licenses DPR-32 & DPR-37,proposing Changes to Ts,By Establishing New Setpoint Limit for Steam Generator high-high Level & Provides More Restrictive Setting Limits for Certain Rps/Esfas Setpoints
ML18153A712
Person / Time
Site: Surry  Dominion icon.png
Issue date: 07/20/1995
From: Ohanlon J
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML18153A713 List:
References
95-365, NUDOCS 9507270067
Download: ML18153A712 (10)
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Text

e VIRGINIA. ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 July 20, 1995 United States Nuclear Regulatory Commission Serial No.95-365 Attention: Document Control Desk NLP/GDM RO Washington, D. C. 20555 Docket Nos. 50-280 50-281 License Nos. DPR-32 DPR-37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATION CHANGE SETPOINT LIMITS Pursuant to 10 CFR 50.90, the Virginia Electric and Power Company requests amendments, in the form of changes to the Technical Specifications, to Operating License Nos. DPR-32 and DPR-37 for the Surry Power Station Units 1 and 2, respectively. The proposed change establishes a new setpoint limit for steam generator high-high level and provides more restrictive setting limits for certain Reactor Protection System/Engineered Safety Features Actuation System (RPS/ESFAS) setpoints.

Administrative changes are also being proposed. The proposed change is discussed in Attachment 1.

This request has been reviewed and approved by the Station Nuclear Safety and Operating Committee and the Management Safety Review Committee. It has been determined that the proposed change does not involve an unreviewed safety question as defined in 10 CFR 50.59 or a significant hazards consideration as defined in 10 CFR 50.92. The proposed change to the Technical Specifications and the basis for our no significant hazards consideration determination are included in Attachments 2 and 3, respectively.

Very truly yours,

~P.Of/Jc~

James P. O'Hanlon Senior Vice President - Nuclear Attachments 9507270067 950720 PDR ADDCK 05000280 P PDR

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cc: U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRG Senior Resident Inspector Surry Power Station Commissioner Department of Radiological Health Room 104A 1500 East Main Street Richmond, Virginia 23219

COMMONWEALTH OF VIRGINIA )

)

COUNTY OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by J. P. O'Hanlon, who is Senior Vice President -

Nuclear, of Virginia Electric and Power Company. He is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this 'aO day of °""Su\:> , 19°\ S.

My Commission Expires: f\-,°ou"6\- ~\ , 19~.

J,tw\~.\~_

Nofary Public I.*

(SEAL)

ATTACHMENT 1 DISCUSSION OF THE PROPOSED CHANGE

  • DISCUSSION OF CHANGES INTRODUCTION Virginia Electric and Power Company is proposing a revision to the Surry Technical Specifications to- 1) revise three Reactor Protection System/Engineered Safety Features Actuation Systems (RPS/ESFAS) channel trip setpoint limits, 2) add a new setpoint limit for high-high steam generator water level, and 3) incorporate editorial changes to revise the measurement units of one setpoint limit and to delete certain references to two-loop operation.

Three RPS/ESFAS setpoint limits are being revised to provide assurance that the effects of instrument channel uncertainties during accident conditions are adequately addressed and are bounded by accident analysis assumptions. The existing Technical Specifications limits were not conservatively specified, since some sources of instrument error, including that due to harsh environmental conditions, were not previously considered and included in the setpoint limits. However, since the RPS/ESFAS setpoints actually implemented in the station are conservative with .

respect to the existing and proposed Technical Specifications values, these changes do not result in an unreviewed safety question or a significant hazards consideration.

Also, a new setpoint limit is proposed for high-high steam generator water level. This protective function is to limit the cooldown associated with a feedwater malfunction event and preclude steam generator overfill.

Editorial changes are also being proposed by this change. The measurement units for the high-high containment pressure setpoint limit are being revised for consistency with the control room instrumentation faceplate indication, and certain references to two-loop operation are being deleted since Surry Power Station is not licensed for operation in that manner.

BACKGROUND Virginia Electric and Power Company has completed a systematic review of instrument channel uncertainties for the Reactor Protection System/Engineered Safety Features Actuation Systems (RPS/ESFAS) instrument actuation setpoints. This effort required the development of a standard calculational methodology for computing the total channel statistical allowance (CSA) for actuation or trip setpoints. This review considered sources of error, such as may be induced by a harsh environment, that were not originally recognized or well understood in initial plant design or licensing.

Consequently, it was considered prudent to reconsider RPS/ESFAS setpoints to ensure they were conservative with respect to accident analyses' assumptions and the more recently considered sources of setpoint error.

As a re'sult of the above review program, the Technical Specifications limits for three protection trip setpoints were identified as requiring revision, and a new setpoint limit was identified for implementation. The affected setpoints are as follows:

1) Steam Generator Water Level Low-Low 2} Steam Generator Water Level High-High
3) Pressurizer Low-Low Pressure
4) High Containment Pressure Editorial changes are also being implemented by this proposed change. The existing high-high containment pressure setpoint limit is being revised to change the measurement units from "psig" to "psia" for consistency with control room instrumentation faceplate indication. Furthermore, the Technical Specifications section that discusses Permissive P-8 Reactor Trip Interlock (unblock) is also being revised to delete references to two-loop operation since Surry Power Station is not licensed to operate in this condition.

The basis for each proposed change is discussed below.

Steam Generator Water Level Low-Low The accident analyses discussed in the Updated Final Safety Analysis Report (UFSAR) that assume the availability of steam generator low-low level protection are loss of normal feedwater and loss of offsite power to the station auxiliaries. The current setpoint limit for this function provided in Technical Specifications 2.3 and 3.7 is >5% of the narrow range span. The accident analyses assume an actuation setpoint of 0%.

However, the original Surry licensing basis did not include a feedline break event in containment. We have since provided summary results for our analyses of a feedline break in containment at Surry in response to NRC Staff questions relating to NUREG-0737, Item II. D. 1, Performance Testing of Relief and Safety Valves (Ser. No.86-094, dated February 28, 1986). These analyses assumed a steam generator low-low level trip setpoint of 0%, consistent with the other accident analyses presented in the UFSAR. However, since the feedline break event creates the potential for an abnormal containment environment, it is necessary to consider harsh environmental effects in the setpoint to ensure the continued validity of the analyses prepared for the NUREG-0737, Item 11.D.1 response.

In view of the above, we are proposing a new narrow range setpoint limit of ~ 14.5% of narrow range span which addresses the channel statistical allowance due to a harsh environment. Station procedures have historically implemented a setpoint of 17% for this narrow range span, and, therefore, no plant operational impact is generated by this change.

St~am Generator Water Level High-High A Technical Specifications setpoint limit does not currently exist for high-high steam generator water level. A Technical Specifications setpoint limit of < 80% of narrow range span is being proposed. This protective function is provided to limit the cooldown associated with a feedwater malfunction event and to prevent steam generator overfill. The setpoint limit has been conservatively based on maintaining water level within the narrow range level span and includes allowances for normal instrument uncertainties and process measurement errors.

Pressurizer Low-Low Pressure This setpoint limit ensures Engineered Safety Features (ESF) actuation for loss of primary or secondary cooling events in accordance with accident analysis assumptions. The accident analysis assumes a safety injection signal is generated when Reactor Coolant System pressure reaches 1715 psia (1700.3 psig) .. However, a harsh environment due to a small steam line break in containment could introduce additional instrument uncertainty. To ensure the original accident analysis assumptions remain valid in such an environment, a channel statistical allowance addressing the condition has been factored into the Technical Specifications setpoint limit. Consequently, a setpoint limit of ~ 1760 psig is proposed. A clarifying statement has also been added to the Bases section for this setting limit that notes the limit is based on nominal atmospheric pressure.

In an operating license amendment request, Serial No. 90-094A, dated May 16, 1990, we demonstrated that plant protection is not dependent on low-low pressure safety injection occurring in a harsh environment. However, because there are operational advantages to ensuring this capability, the proposed operating license amendment was withdrawn and this proposed Technical Specifications setpoint limit change is requested.

High Containment Pressure This setpoint limit ensures primary ESF actuation for high energy line breaks inside containment in accordance with accident analysis assumptions. The accident analysis assumes an ESF signal is generated when containment pressure reaches 19.7 psia

(<5 psig in the current Technical Specifications setpoint limit). To ensure this assumption remains valid, normal environmental errors that instrumentation outside containment may experience are included in the proposed Technical Specifications setpoint limit of $19 psia. The units of the proposed setpoint limit are expressed in "psia" rather than "psig" for consistency with control room instrumentation faceplate indication.

High-High Containment Pressure This setpoint limit ensures ESF actuation for high energy line breaks inside containment in accordance with accident analysis assumptions. The existing setpoint limit is not being changed, however, the units of the proposed setpoint limit will be expressed in "psia" rather than "psig" for consistency with control room instrumentation faceplate indication. Therefore, the units of the current Technical Specifications setpoint limit of$ 10.3 psig will be changed to 5 25 psia.

Permissive P-8 Reactor Trip Interlock (Unblock)

The proposed change does not affect the current Technical Specifications setpoint for the P-8 Permissive interlock. Rather, the proposed change is limited to the Technical Specifications wording and the supporting Basis section. These two sections presently include a discussion of the operation of the P-8 Permissive during two-loop operation. Since Surry is not licensed for two-loop operation, the proposed revision deletes the references to operation in this manner.

SPECIFIC CHANGES The following specific Technical Specifications changes are proposed:

  • Technical Specification 2.3.B.2, "Limiting Safety Settings, Protective Instrumentation," is revised to delete references to two-loop operation regarding operation of the P-8 Permissive interlock.
  • Technical Specification 3.7, Basis, is revised to note that the Pressurizer Low-Low Pressure setting limit is based on atmospheric pressure.
  • Technical Specification Table 3.7-4, is revised as follows:.

Item no. 1 - The setting limit for High Containment Pressure is changed from "5. 5 psig" to 11 5. 19 psia."

Item No. 2 - The setting limit for High-High Containment Pressure is changed from "5. 10.3 psig" to "5. 25 psia."

Item no. 3 - The setting limit for Pressurizer Low-Low Pressure is changed from"?. 1700 psig" to"?. 1760 psig."

Item no. 6a - The setting limit for Steam Generator Water Level Low-Low is changed from "?.5% narrow range" to "?.14.5% narrow range."

Item no. 10 - A new heading, "Turbine Trip and Feedwater Isolation" is included for the newly added Functional Unit number 1Oa, "Steam Generator Water Level High-High," with the Channel Action of "Turbine Trip, Feedwater Isolation," anq the Setting Limit of "5. 80% narrow range."

SAFETY SIGNIFICANCE e

The proposed setpoint limit changes will provide added assurance that the effects of instrument channel uncertainties during accident conditions are adequately addressed, and will also ensure that the relationship between actual plant settings for the RPS/ESFAS and the accident analyses' assumptions is properly maintained.

The setpoint limit changes that are being proposed are consistent with design basis accident analysis assumptions and existing plant practices. Furthermore, the proposed setpoint limit changes are more conservative than those setpoint limits currently allowable in Technical Specifications. The remaining changes, revising the units of a setpoint limit and deleting certain references to two-loop operation, are editorial in nature and not safety significant. As such, these changes do not alter the conclusions of the existing safety analyses. Consequently, an unreviewed safety question does not exist.

No increase in the probability of occurrence or consequences of an accident will result from the proposed RPS/ESFAS Technical Specifications allowable setpoint limits. The changes affect setpoints used to mitigate accidents and therefore have no bearing on the probability of an accident. The consequences of an accident would not increase, since the changes ensure that the setpoint limits used to mitigate an accident bound the setpoints used in the accident analyses. Therefore, the probability of occurrence or consequences of an accident will not be affected as a result of this change.

Implementation of the proposed Technical Specifications setpoint limits does not create the possibility of an accident of. a different type than was previously evaluated in the safety analysis report. Actual plant setpoints are not being affected. New accident precursors are not introduced, since the proposed setpoint limits are more conservative than the values currently provided in the Technical Specifications. Consequently, no new accident precursors are created as a result of the new Technical Specifications setpoint limits.

The proposed changes ensure plant RPS/ESFAS setpoint limits in the Technical Specifications will bound the existing accident analysis assumptions including instrument channel uncertainties due to environmental considerations. Actual plant setpoints are not being affected. Therefore, the margin of safety as defined in the Technical Specifications bases is unaffected.

e ATTACHMENT 2 PROPOSED TECHNICAL SPECIFICATIONS

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