ML19224C335

Forwards Proposed Change Request 39 to App a of Tech Specs, Reducing Time Constant of Neutron Flux Rate Reactor Trips from 2-s to 1-s & Reducing Setpoint of High Negative Rate from 5% to 3%

ML19224C335
Person / Time
Site:	Beaver Valley
Issue date:	06/26/1979
From:	Dunn C DUQUESNE LIGHT CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
TAC-11902, NUDOCS 7907020168
Download: ML19224C335 (5)

Text

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• E .a. Ells (412) 471-4300 435 Sixth Avenue Pittsburgh, Pennsylvania 15219 June 26, 1979 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Attention: A. Schwencer, Chief Operating Reactors Branch No. 1 Division of Operating Reactors Washington, DC 20555

Reference:

Beaver Valley Power Station, Unit No. 1 Docket No. 50-334 Request for Amendment to Operating License Technical Specification Change Request No. 39 Gentlemen:

Enclosed are three (3) signed originals and thirty-seven (37) copies of a proposed change to the Beaver Valley Power Station, Appendix A Technical Specifications which reduces the time constant of the Neutron Flux Rate Reactor Trips from two seconds to one second, and reduces the trip setpoint of the High Negative Rate from five percent to three percent.

Safety Evaluation The proposed changes are presently in effect as a result of a notification by the Westinghouse Electric Corporation that the existing setpoints are not adequate to ensure that the minimum DNBR is maintained above 1.30 for certain rod drop accidents, that might occur at high power levels when the automatic rod control system acts to restore the reactor power level to match the turbine power.

Safety Evaluation The requested setpoints are required to assure that minimum departure from nucleate boiling ratio is always maintained above the value of 1.3 which is utilized in the safety analyses.

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Beaver Valley Power Station, Unit No. 1 Docket No. 50-334 Request for Amendment to Operating License Technical Specification Change Request No. 39 Page Since the staff has previously been informed of the institution of an administrative control which placed these setpoints in effect at Beaver Valley, we have determined that change should be properly categorized as a Class 11 change.

A check in the amount of $1200.00 is enclosed.

Very truly yours,

/ "

C. N. Dunn Vice President, Operations Attachment 268 060

. Mr. A. Schwencer Technical Specification Change Request No. 39 June 26,1979 (CORPORATE SEAL)

Attest:

H.W. 'Staas Secretary COniOtrdZALTH OF PENNSYLVANIA)

) SS:

COUL"I'Y OF ALLEGENY )

On this 26 day of - / s ^/ < I , 1979, before me, DONALD W. SRENON , a Notary Public in and for said Common-wealth and County, personally appeared C. N. Dunn, who being duly sworn, deposed, and said that (1) he is Vice President of Ducuesne Light, (2) he is duly authorized to execute and file the foregoing Submittal on behalf of said Company, and (3) the statements set f o rt*- in the Submittal are true and correct to the best of his knowledge, information and belief.

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DCN ALD W EP/E.ON. NOTARY PUBUC F11TSCUC.CH. ALLECHENY CCUNTY MY COMMISSION EXP!RES JUNE 7.1983 Member, Pennsylvama Assocaten cf Nyaries 268 06:

LIMITING SAFETY SYSTEM SETTINGS BASES The Power Range Negative Rate trip provides pmtection to ensure that the minimum DNBR is maintained 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 0"BR to exist.

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

Intemediate and Source Range, Nuclear Flux The Intemediate and Source Range, Nuclear Flux trips provide reactor core protection during reactor startup. These trips provi e J redundant protection to the low setpoint trip of the Power Range, Neutron Flux channels. The Source Range Channels will initiate a reactor trip at about 10+5 counts per second unless 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 THERMAL POWER unless manually blocked when P-10 becomes active. No credit was taken for operation of the trips . associated with either the Intermediate or Source Range Channels in the accident analyses; however, their functional capability at the specified trip settings is required by this specification to enhance the overall reliability of the Reactor Protection System.

Overtemperature AT

.The Overtemperature AT trip provides core protection to prevent DNB for all combinations of pressure, 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 water with temperature and dynamic compensation for piping delays from the core to the loop temperature detectors. With n.ormal axial power distribution, this reactor trip limit is always below the core safety limit as shown on Figures 2.1-1, 2.1 -2 and 2.1 -3. If axial peaks are greater than design, as indicated by the difference between top and bottom power range nuclear detectors, the reactor trip is automatically reduced according to the notations in Table 2.2-1.

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