ML20138J069

Application for Amend to License DPR-46,relocating Control of Standby Liquid Control Relief Valve Setpoint in TS Section 4.4.A.2.a & Associated Bases

ML20138J069
Person / Time
Site:	Cooper
Issue date:	05/05/1997
From:	Horn G NEBRASKA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20138J073	List: ML20138J069 ML20138J075
References
NLS970093, NUDOCS 9705080007
Download: ML20138J069 (10)

Text

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p7 y COOPEH NUCLEAR STATION g j, 17 /c P.O. BOX 96. BROWNVLLE, NEBRASKA 68321 n 1 Nebraska Public Power District h.u -- .

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NLS970093 May 5,1997 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:

Subject:

Proposed Change to CNS Technical Specification  ;

Standby Liquid Control (SLC) System Relief Valve '

Cooper Nuclear Station, NRC Docket 50-298, DPR-46 In accordance with the provisions of 10 CFR 50.4 and 50.90, the Nebraska Public Power District (the District) requests an amendment to License DPR-46 to change the Cooper Nuclear Station (CNS) Technical Specifications. This request for an amendment supersedes the previously submitted proposed change to CNS Technical Specifications in a letter (NLS970089) dated May 2,1997, and provides additional information supporting the District's position on the SLC relief valve issue. The proposed Technical Specification is considered to be a compensatory measure to resolve a Nuclear Regulatory Commission (NRC) concern regarding potential reduction in margin of safety and hence, a potential unreviewed safety question (USQ) with respect to the SLC relief valve operability.

The purpose of this proposed change is to relocate the control of the SLC relief valve setpoint described in Technical Specification Section 4.4.A.2.a and its associated Bases in Bases Section 3.4.A for the following reasons:

(1) The original calculated nominal SLC system pressure of 1380 psig which was used in establishing the Technical Specifications SLC relief valve minimum opening pressure of 1450 psig by adding 70 psi margin has been recalculated to be 1419 psig based on test data; this increase in nominal SLC system pressure from 1380 psig to 1419 psig has brought into question the adequacy of the Technical Specification minimum pressure for the SLC relief valves.

(2) The SLC relief valves are set and administratively controlled at a nominal setpoint of 1540 psig 1% per the IST Augmented Testing Program, which is much higher than the Technical Specification minimum opening pressure of 1450 psig and therefore, yields a margin of 121 psi above the recalculated SLC system 07007i3 pressure than the 70 psiof 1419 margin psig.

which ThisTechnical the current marginSpecification of 121 psi minimumis greater and mo opening pressure is based on.

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% t NLS970093 May 5,1997 Page 2 0f 4 (3) The relocation of the SLC relief valve setpoint control from the Technical Specifications has also been proposed in CNS Improved Technical Specification (ITS) submittal (NLS970002) dated March 27,1997. It is based on the adequacy of the administrative control established on the changes to SLC testing and relief valve setpoint requirements in the IST program.

l (4) The SLC relief valve nominal setpoint of 1540 1% and its associated bases have l been included in the USAR , a copy of which is being enclosed with this proposed  !

change request. It confirms that any changes to the SLC relief valve nominal l setpoint would fall under the purview of 10 CFR 50.59 regulation.  !

Irrespective of the above mentioned reasons for this proposed Technical Specification change, the District has been maintaining and continues to maintain the control of the SLC relief valve nominal setpoint at 1540 psig 1% under current CNS IST Augmented Testing Program. When a setpoint drift of 3% is applied to the relief valve nominal setpoint this setpoint can drift under the worst case conditions, down to 1478 psig; however, the maximum expected SLC system pressure for two-pump operation is 1433 psig which includes allowances for pump ripple effects.

Consequently, under the worst setpoint drift condition, the SLC relief valve nominal setpoint would still maintain significant margin above 1433 psig to ensure that the relief valves will not lift and cause recirculation flow during the operating interval between setpoint verification tests.

Furthermore, inclusion of the SLC relief valve setpoint at 1540 psig 1% into the USAR l provides a more strict control of the setpoint change via the 10 CFR 50.59 procen. Tb refore, the District believes that it does not involve a reduction in margin of safety and a USQ in this ,

case.

Attachment 1 provides the detailed description and evaluation of this proposed change to the

CNS license and basis for an emergency approval. Attachment 2 contains the bases for the change, the no significant hazard consideration determination, and the CNS Technical Specification pages revised by this change. This proposed change has been reviewed by the necessary safety review committees and incorporates all amendments to the CNS Facility Operating License through Amendment 175 issued on April 29,1996.

Pursuant to 10 CFR 50.91 (a) (5) the District requests emergency approval of this amendment to support the startup of CNS from its present refueling outage. Approval of this amendment on an emergency basis is warranted because the current situation satisfies the definition of emergency:

Failure to act in a timely way would result in the prevention of resumption of operation

[10 CFR 50.91 (a) (5)].

The District's request for an Emergency License Amendment has resulted from the fact that the NRC notified the District on May 1,1997, of the SLC relief valve setpoint concern as a CNS

s 1-1 j NLS970093 ,

l. May 5,1997

]- Page 3 of 4 i . startup issue. Since the current projected date for CNS startup is May 12,1997, the District requests that the amendment implementing this proposed Technical Specification change be 4

issued on or before May 10,1997.

t j By copy of this letter and its attachments the appropriate State of Nebraska official is being notified in accordance with 10 CFR 50.91 (b)(1). Copies to the NRC Region IV office and the CNS Resident Inspector are also being provided in accordance with 10 CFR 50.4 (b) (2).  !

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j . Should you have any questions or require any additional information regarding this submittal, j i please contact Brad Houston at (402) 825-5819.

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uy . Horn

'or Vice President  ;

! of Energy Supply .

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! Attachments

, Enclosure l cc: Regional Administrator

! USNRC - Region IV i

l Senior Project Manager l USNRC - NRR Project Directorate IV-1 l

i Senior Resident Inspector USNRC i

j- Environmental Health Division - Program Manager j Nebraska Department of11ealth NPG Distribution f

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NLS970093 May 5,1997 i Page 4 of 4 l i

STATE OF NEBRASKA ) l

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G. R. Horn, being first duly sworn, deposes and says that he is an authorized representative of the ;

Nebraska Public Power District, a public corporation and political subdivision of the State of l Nebraska; that he is duly authorized to submit this correspondence on behalf of Nebraska Public l Power District; and that the statements contained herein are tree to the best of his knowledge and i belief.

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' G. R. IIorn Subscribed in my presence and swom to before me this 5 W day of MA~f-

,1997, d

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0 'J Attachment I to NLS970093 Page1of3 DESCRIPTION AND EVALUATION OF THE PROPOSED CHANGFS Background for the Need for a License Amendment The Technical Specifications specify a minimum and a maximum SLC relief valve opening pressure setpoint and a minimum reset pressure setpoint. The maximum opening pressure setpoint is based on system overpressure protection requirements. The purpose of the minimum operating pressure and reset pressure setpoint for the SLC is to preclude recirculation flow I through the relief valves. Otherwise, recirculation would allow a portion of the pumped borated solution to flow back to the pump suction instead of to the reactor vessel, and thereby reduce the i rate of boron injection into the reactor vessel.

Prior to 1983, the CNS Technical Specification limits were 1400 to 1680 psig and the SLC relief valves were set at a nominal value of 1460 psig. In 1983, the relief valve setpoint was raised to a nominal setpoint of 1540 psig which was in the middle of the allowable range of 1400 to 1680 psig.

In April of 1986, General Electric (GE) performed a calculation as a part of" Cooper ATWS l Assessment," which determined the discharge pressure with simultaneous operation of two (2)

SLC pumps to be 1380 psig (approximately). Subsequently, GE added 70 psi to the calculated ,

pressure to account for 3% allowance for setpoint drift and the rest for pump ripple. Based on j this analytical result, GE recommended raising the SLC relief valve minimum setpoint in the l Technical Specifications from 1400 to 1450 psig to minimize valve leakage.

1 Subsequently, CNS in a letter (NLS870187) dated April 18,1987, to the NRC provided ATWS information that stated the pump discharge pressure would increase to 1378.5 psig and that the SLC system relief valve lower setpoint pressure would be raised to provide approximately 70 psi  ;

setpoint margin to minimize valve leakage. It should be noted that this information was provided l to the NRC prior to any testing while the SLC relief valves were already set at the nominal setpoint of 1540 psig 1%. On December 23,1987, the Safety Evaluation Report (SER) issued by the NRC relating to the ATWS Rule for CNS concluded that CNS's proposed changes to the SLC system conformed to the ATWS Pule. It also indicated that CNS should submit a Technical Specification Change as soon as possible. On April 29,1988, CNS applied for a Technical Specification Amendment (Proposed Change No. 35) based on the NRC's acceptance of the proposed changes to the SLC system which proposed to raise SLC relief valve minimum setpoint to 1450 psig (nominal). In May of 1988, SLC pump injection test was performed, which noted higher discharge pressures at the pumps (1419 psig approximately).

On July 5,1988, the NRC issued License Amendment 123 based on Proposed Change No. 35 and approved raising minimum operating pressure for the SLC relief valves from 1400 to 1450.

The Safety Evaluation Report issued by the NRC stated the purpose of the minimum pressure setpoint was to preclude recirculation flow through the relief valves.

i 3 Attachment 1 to NLS970093 Page 2 cf 3 Although the actual pump testing in May 1988 revealed a higher discharge pressure of 1419 psig (approximately), on September 29,1988, GE reevaluated the previous calculation and stated that there was sti4 sufficient relief valve pressure margin at the system design flow rate of 106 gpm (both pump loops operating) to assure full flow rate to the reactor. The GE report also stated that while the SLC system test results were higher than predicted, there was no evidence that the SLC system would not meet the ATWS Rule requirements as intended. GE recognized that CNS normally set the SLC relief valves at a nominal setpoint of 1540 psig and in light of that fact, felt that the minimum 1450 psig was still valid because the 31 psi would still account for the pump ripple and that there was no need to include the 3% allowance for setpoint drift at 1450 psig because CNS did not set the SLC relief valves at that pressure. This new information did show an increase in the initial conditions, but this increase was still lower than the minimum Technical i Specification limit of 1450 psig; therefore, it provided confirmation that the lower limit of 1450 psig was still valid.  ;

In November of 1996, the NRC identified this as a potential reduction in the margin of safety, because the Technical Specification Change Request (Proposed Change No. 35) submitted on

, April 29,1988 to implement the ATWS Rule, indicated a 70 psi difference between the system pressure of 1380 psig (approximately) during ATWS and minimum Technical Specification pressure of 1450 psig; however, the testing and revised calculation data performed in May 1988 indicated a difference of only 31 psi. The NRC and CNS both recognized that the ATWS requirements were met with relief valve setpoint of 1540 psig since this setpoint was midrange for the Technical Specification setpoint band of 1450 and 1680 psig. Still the NRC viewed this issue as a reduction in the margin of safety (a reduction from 70 psi to 31 psi) and a potential 1 USQ.

When the NRC identified this potential issue, CNS started its investigation to determine if the ,

lower Technical Specifications limit of 1450 psig was adequate. All subsequent analyses and l calculations performed to date have shown that the predicted higher discharge pressures are still  !

bounded by the lower Technical Specifications limit of 1450 psig. Furthermore, the existing

relief valve setpoint at 1540 psig (nominal) 1% set per IST Augmented Testing Programs maintains a margin of 121 psi above the recalculated nominal SLC pressure of 1419 psig.

Therefore, although CNS recognizes NRC's position on this matter, CNS believes that a reduction of margin of safety is not involved in this situation and that there is no potential USQ concern.

CNS also feels that since raising the SLC system pressure from 1380 psig to 1419 psig brought into question the Technical Specification lower pressure limit of 1450 psig, the actual setpoint of SLC relief valve pressure would be better administratively controlled by the existing IST Augmented Testing Program and by the USAR through 10 CFR 50.59 process rather than by the

. Technical Specifications requirements. For that reason, CNS considers this proposed Technical Specification change as a compensatory measure to resolve the NRC's concern and preclude any further recurrence of this issue.

e i Attachment I to NLS970093 i Page 3 of 3 Basis for Emergency Amendment Pursuant to 10 CFR 50.9) (a)(5), the District requests emergency approval of this amendment to support the startup of CNS from its present refueling outage. Approval of this amendment on an emergency basis is warranted because the current situation satisfies the dermition of emergency:

Failure to act in a timely way would result in the prevention of resumption of operation

[10 CFR 50.91 (a)(5)].  :

Although the NRC identified the concern regarding potential reduction in safety margin and USQ  :

back in November of 1996, the District continued to believe that the District's action were conservative until the NRC notified the District on May 1,1997, of the SLC relief valve setpoint concern as a CNS startup issue.

Since the projected startup date at CNS is May 12,1997, the amendment to the CNS license needs to be issued on or before May 10,1997, i

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l Attachment 2 l to NLS970093 l Page1of3 ,

COOPER NUCLEAR STATION I TECHNICAL SPECIFICATIONS STANDBY LIOUID CONTROL SYSTEM RELIEF VALVES Revised Pages 107 110 1.0 Bases for Changes S.ection 4.4. A.2.a This paragraph delineating the operability testing of SLC relief valves has been removed based on the fact that the control of the relief valve setpoint has been relocated to the Augmented Testing Program which is a part of the In-Service Testing Program and to the USAR.

Section 3.4.A Bases The paragraph describing the significance of SLC relief valve setting has been deleted since the SLC relief valve setpoint control have been relocated from the Technical Specifications.

2.0 Significant Hazard Determination 10 CFR 50.91 (a) (1) requires that licensee requests for operating license amendments be accompanied by an evaluation of significant hazard posed by the issuance of an amendment. This evaluation is performed with respect to the criteria given in 10 CFR 50.92 (c).

This proposed change to Cooper Nuclear Station (CNS) Technical Specifications deletes the SLC relief valve operability testing.

I 2.1 The proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated. Standby Liquid Control (SLC) system is designed to meet two functions: a) bring the Reactor to a cold shutdown condition without use of control rods, and b) meet the requirements of the ATWS Rule per 10 CFR 50.62. Neither of these functions are impacted by l

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s s Attachment 2 to NLS970093 Page 2 of 3 the relocation of the SLC relief valve setpoint control from the Technical Specifications to the IST Augmented Testing Program and to the USAR.

Furthermore, the removal does not alter any input parameters or precursors for any accident analyses described in the USAR. The function of the SLC relief valves during an ATWS event is to remain closed during two-pump SLC operation, thereby preventing recirculation flow. Also, the relief valve testing requirements per the IST Augmented Testing Program preserves the requirements to test the valves. Consequently, the ability of the relief valves to perform their credited function is not challenged by this proposed change. Therefore, relocation of the SLC relief valve setpoint control from the CNS Technical Specifications does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2.2 The proposed change will not create the possibility of a new or different kind of accident than evaluated in the USAR. The proposed change does not result in any physical change to CNS Structures, Systems, or Component, nor does it change the fit, form, or function of any equipment / component taken credi; for in the accident analyses described in the USAR. Therefore, the relocation of the SLC relief valve setpoint control from the Technical Specifications does not create the possibility of a new or different kind of accident.

2.3 The proposed relocation of SLC relief valve testing from the CNS Technical Specifications to the IST Augmented Testing Program and to the USAR will not l reduce the margin of safety. The SLC relief valve setpoints are being tested at the i same frequency under the IST Augmented Testing Program. Under this program, the valves are set at a nominal setpoint of 1540 psig 1%. Since the maximum nominal SLC system pressure based on test data is determined to be 1419 psig, a margin of 121 psi is available between this calculated pressure and the relief valve j nominal setpoint. This 121 psi margin allows fbr pump ripple and setpoint drift as opposed to only 70 psi which in the past has been added as a margin to obtain the current Technical Specification minimum limit of 1450 psig from the original calculated maximum SLC system pressure of 1380 psig to account for the same l reasons. Although the SLC calculated maximum system pressure has increased from 1380 psig to 1419 psig based on test data by setting the SLC relief valve at a nominal setpoint of 1540 psig 1%, an increase in the margin will be achieved since consistent methodology has been applied in both cases.

3.0 Conclusion The District has evaluated the proposed changes described above against the criteria of 10 CFR 50.92 in accordance with the requirements of 10 CFR 50.91 (a)(1). This evaluation has determined that the proposed change to

b 4 Attachment 2 to NLS970093 Page 3 of 3 Technical Specifications will not (1) involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the possibility for a new or different kind of accident from any accident previously evaluated, or (3) create a significant reduction in the margin of safety. Therefore, the District requests NRC approval of this proposed change.

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