ML19224D063

Requests Proposed Tech Spec Change 21 as Amend to License NPF-4,changing Power Range Neutron Flux Negative Rate Trip. Forwards Appropriate Amend Fee

ML19224D063
Person / Time
Site:	North Anna
Issue date:	07/06/1979
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton, Parr O Office of Nuclear Reactor Regulation
References
NUDOCS 7907100581
Download: ML19224D063 (6)

Text

..VIllO I NI A ELiccritic AN D P O W I?ll COMMNY HIcunown,VIHOIN 1A 23261 July 6, 1979 Mr. Harold R. Denton, Di rector Serial flo. 504 Of fice of fluclear Reactor Regulation LQA/ESG:esh Attn: fir. O. D. Pa rr, Chief Light Water Reactors Branch flo. 3 Docket No. 50-338 Div icn of Project Management U. S. Nuclear Regulatory Commission License No. NPF-4 Wasaington, DC 20555 Dea r fir. Denton:

AMENDMENT TO OPERATIflG LICENSE PROPOSED TECHNICAL SPECIFICATION CHANGE NO. 21 NORTH ANNA POWER STATION UNIT fl0. 1 Pursuant to 10 CFR 50.90, the Virginia Electric and Power Company hereby requests an amendment, in the form of changes to the Technical Specifications, to Operat ing License flo. NPF-4 for the florth Anna Power Station, Un i t flo. 1.

The pro-posed changes are enclosed, and have been designated ,s Change No. 21.

Our letters, Serial No. 230, April 6,1979, and Serial No. 241, April 10, 1979, described a deficiency which was discovered in the analysis of departure fron nucleate boiling ratio following a single dropped rod ev. 7t.

We stated at that time t hat Wes tinghouse Electric Corporation was conductir , an analysis to determine the most appropriate corrective action.

Westinghouse reported the results of i ts analyses to the NRC Staf f during a meeting on April 12, 1979, and in a subsequent telephone conversation on May 3, i979. Resolution of the probicm is achieved by changes to the Technical Specifica-tions concerning the power range neutron flux negative rate t rip.

Since the hard-ware generating the negat ve rate t rip t ime constant also supplies the time constant for the power range positive rate trip circuit, a corresponding change to the time constant speci fication for the posi tive rate t rip is also required. The necessary Technical Specification changes for Nor h Anna Unit No. I are enclosed.

s The positive rate t rip is a secondary means of protection for rapid power excursion transients. The florth Anna FSAR only takes credi t for the neutron flux high/ low setpoin t.

Consequently, there is no change in the margin of safety as preser.ted in ti.' FSAR.

This change has been reviewed and approved by the Station Nuclear Safety and Operating Commi ttee and the Sys tem Nuclear Sa fety and Operat ing Com1i ttee.

It has been dete rmined that this change doe.s not involve an unreviewed safety question as defined in 10 CFR 50.59.

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.s uvasa I:trenne no i>owru coxmy ro tir. Ha rol d R. Den ton 2 This request has been evaluated in accordance wi th the criteria of 10 CFR 170.22, and has been determined to be in Class Ill.

The changes involve a single issue, and the Staf f should be able to conclude that the request does not involve a significant hazards consideraticr.. Accordingly, our check in the amount of $4,000.00 is attached in payment of the amendment fee.

Very truly yours, f 'l_[i Llu t y J C. M. Stallings Vice President-Power Supply and Production Operations

Enclosures:

1.Proposed Change No. 21 2.Check in amount of $4,000.00 cc: Mr. James P. O'Reilly, Director Of fice of Inspect ion and Cn forcemen t Region lI bb,'-

.COMMONWEALTH OF V IRGINI A

))s. s.CITY OF RICHMOND

)Before me, a Notary Public, in and for the City and Comnon-wealth aforesaid, today personally appeared C. M.

Stallings, who being duly sworn, made oath and said (1) that he is Vice President-Power supply and Production Operations, of the Virginia Electric and Power Company, (2) that he is duly authorized to execute and file the fore-going Amendment in behalf of that Company, and (3) that the statements in the Amendment are true to the best of his knowledge and belief.

f',Given under my hand and notarial seal thish day of og..n ,, ,l.///l(s'[MyCommissionexpires.i' / / '.h. , . ,./1s.Ai /% L No try Public

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.f~LIMITING SAFETY SYSTEM SETTINGS BASES The Power Range Negative Rate trip provides protection to ensure that the minimum DNBR is mair,tained above 1.30 for rod drop accidents.

At high power a single or multiple rod drop accident could cause local flux peaking which when in conjunction with nuclear power being maintained equivalent to turbine power by action of the automatic rod control system could cause an unconservative local DNBR to exist.

The Power Range Negative Rate trip will prevent this from occurring by tripping the reactor for all single or multi-pie dropped rods.

.Intermediate and Scurce Rance, Nuclear Flux The Intermediate and Source Range, Nuclear Flux trips provide reactor core protection during reactor startup.

These trips provide redundant protection to the low setpoint trip of the Power Range, Neutron Flux channels The Source Range Channels will initiate a reactor trip at y about 10 counts per second ualess manually blocked when P-6 becomes active. The Intermediate Range Channels will initiate a reactor trip at a current level proportional to approximately 25 percent of RATED THERML POWER unless manually blocked when P-10 becomes active.

No credit was taken for operation of the trips associated with either the Intermediate or Scurce Range Channels in the accident analyses; however, their functional capability at tha specified trip settings is required by this specification to enhance the overall reliability of the Reactor Protection System.

Overtempera ture t.T The Overtemperature tT trip provides core protection to prevent DNB for all combinations of prersure, power, coolant temperature, and axial power distribution, provided that the transient is slow with respect to piping transit delays from the core to the temperature detectors (about 4 seconds), and pressure is within the range between the High and Low Pressure reactor trips.

This setpoint includes corrections for changes in density and heat capacity of ater with temperature and dynamic com-pensation for piping delays from the core to the loop temperature detectors. With normal axial pc',,er distribution, this reactor trip limit is always below the core safety limit as shown in Figure 2.1-1.

If axial peaks are greater than design, as indicated by the difference between top and botten power range nuclear detectors, the reactor trip is automatically reduced according to the notations in Table 2.2-1.

NORTH ANNA-UNIT 1 B 2-4[]!