ML20207F005

Application for Amend to License NPF-1,consisting of License Change Application 141,changing Tech Specs to Reflect That Differential Pressure Across ECCS Pumps Must Be Measured Vice Discharge Pressures to Determine Operability

ML20207F005
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	07/17/1986
From:	Withers B PORTLAND GENERAL ELECTRIC CO.
To:
Shared Package
ML20207E992	List: ML20207E988 ML20207F005 ML20207F018
References
TAC-62186, NUDOCS 8607220461
Download: ML20207F005 (7)

Text

W PORTLAND CENERAL ELECTRIC COMPANY EUGENE WATER & ELECTRIC BOARD AND PACIFIC POWER & LIGHT COMPANY Operating License NPF-1 Docket 50--344 License Change Application 141 This License Change Application requests a modification of the Surveillance Requirements of Technical Specification Section 4.1.2.3, 4.1.2.4, and I

4.5.2.1, regarding ECCS pump differential pressure, Appendix A to Operating l License NPF-1 for the Trojan Nuclear Plant, t

i PORTLAUD CENERAL ELECTRIC COMPANY By ' 4 -M Bart D. Withers Vice President Nuclear I

Subscribed and sworn to before me this 17th day of July 1986.

j Notary Public of Oregqjf l

/+f M 9MyCommission v '

l 8607220461 860717 i PDR ADOCK0500g4 P

r s

k LCA 141 Attachment A Page 1 of 6 DESCRIPTION OF CHANGE The surveillance requirements for the Emergency Core Cooling System (ECCS) pumps are described on Pages 3/4 1-11, 3/4 1-12, and 3/4 5-6a of the Technical Specifications, Sections 4.1.2.3, 4.1.2.4, and 4.5.2.1.

The following changes to the above Technical Specifications are made.

Technical Specification 4.1.2.3 - The surveillance requirement for the centrifugal charging pump (CCP) operability requirement for Modes 5 and 6, is changed to " verifying, that on recirculation flow, the pump develops a differential pressure 12400 psid when tested pursuant to Technical Specification 4.0.5".

Technical Specification 4.1.2.4 - The surveillance requirement for the CCP operability requirement for Modes 1, 2, 3, and 4 is changed to

" verifying, that on recirculation flow, each pump develops a differential pressure 12400 psid when tested pursuant to Technical Specifiaation 4.0.5".

Technical Specification 4.5.2.1 - The surveillance requirement for the ECCS pump performance verification is changed to "By verifying that each of the following pumps develops the indicated differential pressure on recirculation flow when tested pursuant to Technical Specification 4.0.5:

"1) Centrifugal charging pump 12400 psid, "2) Safety injection pump 11455 psid, and "3) RHR pump 1157 psid."

REASON FOR CHANGE

a. The verification of ECCS pump performance is changed from measuring pump discharge pressure on recirculation flow, to measuring pump differential pressure on recirculation flow. This change is based on the following:

1. Draft Revision 5 to NUREC-0452 (Standard Technical Specifica-tions for Westinghouse Pressurized Water Reactors) calls for the measuring of pump differential pressure to verify pump performance for the ECCS pumps,

11. Pump performance is verified when tested pursuant to Technical Specification 4.0.5, which is Inservice Inspection and Testing of ASME Code Class 1, 2, and 3 pumps and valves in accordance with Section XI of the ASME Boller and Pressure Vessel Code and applicable Addenda. In ASME Section XI, differential pressure is a measured test quantity with clearly defined allowable ranges, and actions to be taken should the value fall outside a particular range.

LCA 141 Attachment A Page 2 of 6 111. Vendor pump curves are given in terms of either differential head vs flow rate, or total head vs flow rate. Measuring only pump discharge pressure does not allow direct comparison to the manufacturer's pump curve.

iv. Pump discharge pressure is not a true indication of pump per-formance since it is dependent upon pump suction pressure. An increase in pump suction pressure will cause a corresponding increase in pump discharge pressure, independent of how the pump is performing, or if it is even running.

b. The values of pump differential pressure used to verify pump operability are changed based upon:

1. Each CCP must develop 12400 psid on recirculation flow. This is the value used by Westinghouse in the FSAR Chapter 15 acci-dent analysis and is based upon a Westinghouse study of pumps of the same manufacturer and model with a 5 percent (of design head) margin being applied to the lowest pump curve in the study, ii. Each safety injection pump must develop 11455 psid on recircu-lation flow. This is the value used by Westinghouse in the FSAR Chapter 15 accident analysis and is based upon a Westinghouse study of pumps of the same manufacturer and model with a 5 percent (of design head) margin being applied to the lowest pump curve in the study.

iii. Each residual heat removal (RHR) pump must develop 1157 psid on recirculation flow. The value of 157 psid was determined by an evaluation by Westinghouse. This evaluation was performed because of an apparent degradation occurring to the RHR pumps.

i The evaluation involved reducing a 1983 as-measured RHR pump curve (which was itself reduced by approximately 15 percent in pump head below the vendor pump curve) by an additional 5 per-cent head, at the design point, over the entire pump performance l curve.

l The following safety analysis performed by Westinghouse showed that the resulting flow had minimal impact on peak clad temperature (PCT). Since small break LOCAs are not assumed to actuate RHR pumps, only large break LOCA analysis needed to be analyzed.

I The effect of reduced safety injection flow on large break l performance as calculated within the 1979 analysis is to prolong the refilling of the reactor vessel with water.

The PCT of 1970*F is calculated to occur at time 47.34 sec-onds in the 6 percent SGTP analysis limiting case break (CD = 0.6 DECLG). The PCT transient turns around once t

7-6 LCA 141 Attachment A Page 3 of 6 enough water has been injected via accumulator and pumped safety injection that the hot fuel in the core begins to be recovered. At that time, steam generated near the bottom of the core rises and provides adequate cooling at the PCT elevation to terminate the temperature rise. Any delay in the liberation of steam which cools the fuel at the PCT elevation will extend the PCT heatup correspondingly.

In an Appendix K ECCS performance analysis, a limiting single failure nust be assumed. Revised RHR pump flow delivery considering the limiting single failure and the spilling of the lowest resistance injection line have been computed based upon the as-measured RHR pump curve degraded by an additional 5 percent head at the design point. This 5 percent head is subtracted uniformly over the entire pump performance curve.

The impact of the reduced RHR flow delivery is that 1140 lbs le&J water is pumped into the Reactor Coolant System from the start of pumped injection through time 47.34 seconds that was credited in the 6 percent SGTP analysis. In order to make up for this shortfall.

0.25 seconds of additional accumulator / safety injection flow at the prevailing rate must be delivered to provide the water inventory necessary to achieve PCT turn-around.

An additional 0.25 seconds of fuel rod heatup at the PCT elevation will occur as a result.

The consequence in calculated PCT of this additional 0.25 seconds heatup has been conservatively evaluated utilizing the maximum fuel cladding heatup rate observed between end of blowdown and the time of PCT. Based upon this maximum rate of 42*F/second, the PCT elevation will increase 11*F in temperature due to the reduced RHR pump performance. This upper bound to the PCT impact is small, and much margin remains to the regulatory limit of 2200*F.

The revised PCT for the Trojan limiting case break is:

1970*F from the 6 percent SGTP analysis

+ <20*F due to upflow conversion

+ 11*F to accommodate reduced RHR pump flow

<2001*F resulting PCT Clearly, the reduction in pumped RHR flow is acceptable from a LOCA standpoint.

The RHR pumps are not actuated in the Trojan small break LOCA analysis, so it remains unaffected.

1

LCA 141 Attachment A Page 4 of 6 The issue and the follow-up corrective action proposed by this LCA were discussed in NRC Inspection Reports 85-13, 85-16, 85-21, and 85-32. The specific issue was designated by NRC Region V as Unresolved Item 85-13-01 and has been closed in Inspection Report 85-32.

SAFETY / ENVIRONMENTAL EVALUATION As shown in the Significant Hazards Consideration, the measurement of pump differential pressure, over discharge pressure, is a net improvement in the determination of pump performance. The differential pump head values for the safety injection and CCPs are not being changed. These are the values used by Westinghouse in the FSAR Chapter 15 accident analysis. The differential pump head values for the RHR pumps have been evaluated by Westinghouse as meeting the 10 CFR 50.46 PCT limit of 2200*F. From the above staten.ents, these values of differential pump head do not involve an unreviewed safety question.

These pumps do not affect the Plant discharge to the environment and, thus, do not involve an unreviewed environmental question.

SIGNIFICANT HAZARDS CONSIDERATION In accordance with the requirements of 10 CFR 50.92, the enclosed application is judged to involve no significant hazards considerations based upon the following information:

1. Does the proposed license amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response

Pump discharge pressure is not a true indication of pump performance since it is dependent upon pump suction pressure. An increase in pump suction pressure will cause a corresponding increase in pump 6ischarge pressure, independent of how the pump is performing or if it is even running. The change of units from psig to psid will measure the actual pump performance and, thus, does not increase the probability or consequences of an accident.

Centrifugal charging and safety injection pumps are to develop pres-sure differentials of 2400 psi and 1455 psi, respectively. These values were used by Westinghouse in the FSAR Chapter 15 accident analysis.

RHR pumps must develop pressure differentials of at least 157 psid.

Although the value of 157 psid is 8 psi lower than the current limit of 165 psi, based on the following information it meets the design function of the RHR System. The RHR System serves three functions:

cools the RCS to and maintains the RCS at shutdown temperatures,

e LCA 141 Attachment A Page 5 of 6 provides low-head injection and recirculation during LOCA conditions, and transfers water between the Refueling Water Storage Tank and the refueling cavity. During cooldown operations, flow through the heat exchangers meets the design basis of 3000 spm as specified in TTS 4.9.8.1. The most limiting LOCA analysis is for that of a large break. The new value of RHR pump head requires an additional 0.25 seconds of accumulator / safety injection flow to achieve the PCT turn-around. This 0.25 seconds of additional heatup results in an 11*F increase of PCT to the temperature 2001*F (see Reason for Change, Item b.lii). This PCT of 2001*F is well within the 2200*F 10 CFR 50.46 limit. The third function, the transfer of RCS water

, for refueling, is a non-safety-related function.

From these statements, the pump head values, for all three type of pumps, do not increase the probability or consequences of an accident.

2. Does the proposed license amendment create the possibility of a new or different kind of accident from any accident previously evaluated?

Response

As shown in the response to Question 1, the ECCS pumps will continue to provide adequate flow and head to allow the ECCS to fulfill all of its design functions and, thus, incorporating the ECCS pump head values into the TTS does not create a new or different kind of accident.

3. Does the proposed amendment involve a significant reduction in a margin of safety?

Recponse:

The margin of safety (the capability of boron injection and emergency cpre cooling) provided by the safety injection, charging and RHR pumps will be improved by replacing the imprecise requirements with those specified in this amendment request which will produce more precise results by changing the units from psi to psid.

The safety injection and centrifugal charging pump heads are the original numbers used by Westinghouse in the FSAR Chapter 15 accident analysis and, thus, no reduction in the margin of safety is being made.

Due to the degradation of RHR Pump A, Westinghouse has determined the new requirement for the RHR pumps should be 157 psid at 600 gpm recirculation flow. Based on the RHR pump capability to meet design flow through the RHR heat exchangers and the 199'F margin to the 10 CFR 50.46 PCT limit, no significant reduction in a margin of safety will occur.

e LCA 141 Attachment A Page 6 of 6 In the April 6, 1983 Federal Register, the NRC published a list of examples of amendments that are not likely to involve a significant hazards concern. Examples No. 2 and 6 of that list applies to the inplementation of more stringent test procedures of the safety injection, charging and RHR pumps and the revised calculation of the required RHR pump differential head, respectively.

Example No. 2 states:

"A change that constitutes an additional limitation, restriction, or control not presently included in the technical specification: for example, a more stringent surveillance requirement."

Example No. 6 states:

"A change which either may result in some increase to the probability or consequences of a previously analyzed accident or may reduce in some way a safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan: for example, a change resulting from the application of a small refinement of a previously used calculational model or design method."

While a reduction in the requirement of RHR pump head does reduce in a small way the margin of safety, the results of the change clearly fall inside the acceptance criteria of the Standard Review Plan.

Based on the above evaluation, this proposed change does not involve a significant hazards consideration.

NRO/kal 5813k.786