ML20053C764
| ML20053C764 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/26/1982 |
| From: | Carey J DUQUESNE LIGHT CO. |
| To: | Varga S Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20053C765 | List: |
| References | |
| TAC-48018, NUDOCS 8206020544 | |
| Download: ML20053C764 (7) | |
Text
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May 26, 1982 c
Shippingport. PA 150774004 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Attn:
Mr. Steven A.
Varga, Chief Operating Reactors Branch No. 1 Division of Licensing Washington, D.
C.
20555
Reference:
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Cycle 3 Reload Safety Evaluation Gentlemen:
This letter provides additional information related to our application for amendment to Technical Specifications (No. lA-66) forwarded by our letter dated February 23, 1982 as amended by our letter dated May 5, 1982.
This letter also forwards revised pages which amend the May 5, 1982 revised proposed Technical Specifications and three originals and thirty-seven copies of this letter are provided for this purpose.
This letter addresses concerns of the NRC Staff related to this proposed Technical Specification as discussed in conference calls on May 21 and May 25, 1982.
During these telephone conference calls, the NRC Staff raised three concerns requiring resolution.
Each of these concerns is addressed herein and appropriate changes to the proposed Technical Specifications or procedures have been, or will be, made to satisfy the issues giving rise to these NRC concerns.
1.
The NRC Staff expressed concern that compliance with the one hour soak time which is allowed in proposed Specifications 3.1.3.1, 4.1.3.1.1, 3.1.3.2, 4.1.3.2.1, 4.1.3.2.2 (note) and Basis 3/4 1-3 is not achievable during normal operation since minor amounts of rod motion may be required to maintain plant parameters within the normal operating range.
This concern has been addressed by revising proposed Technical Specification pages 3/4 1-19, 3/4 1-20b, B 3/4 1-3; Specifications 4.1.3.1.1, 4.1.3.2.2 (note) and Basis 3/4 1-3 to allow a maximum deviation of 6 steps from the desired rod position during the one hour " soak" time permitted to achieve thermal equilibrium.
This proposed modification provides flexibility to the operator to move control rods through l
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Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Cycle 3 Reload Safety Evaluation May 26, 3982 Page 2 this limited range and addresses the concern that the performance of the surveillance requirements of Specifications 4.1.3.1.1, 4.1.3.2.1 and Note 4.1.3.2.2 will not be precluded becuase minor rod motion was required during the one hour soak period.
Our experience and testing has led us to the conclusion that rod motion in this limited range during the soak period will not upset the thermal equilibrium of the Rod Position Indication System detector coils to the extent that the basic calibration of the system is significantly disturbed.
Further, since rcds are moved as a bank, any thermal transient imposed upon the Rod Position Indication System will affect all rods in the bank in relatively the same manner; thus the ability to detect a rod out of bank situation is not materially impaired.
Amended pages 3/4 1-19, 3/4 1-20b, B 3/4 1-3 are attached to reflect this change.
Please note that a changed page for surveillance requirement 4.1.3.2.1 has not been submitted since this reference to soak time is more completely defined in 4.1.3.1.1 and repetition of these qualifying statements in 4.1.3.2.1 is not considered necessary.
2.
The NRC Staff expressed concern related to Specification 4.3.1.1 in that unless the plant computer is programmed to take into account the basic nonlinearity of the calibration of the Rod Position Indication System detector coils, spurious rod deviation alarms may be generated either due to rod motion or calibration differences.
This concern stems from the Company's past practice of representing the relationship between RPI signal conditioner output voltage and actual rod position as a straight line within the plant computer.
The plant computer actually has the capability of representing the RPI calibration function as a fifth order equation.
We will calibrate the computer during the performance of this, and each succeeding calibration of the analog Rod Position Indice ion System with higher order equations which close' oresent the actual calibration of the
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Cycle 3 Reload Safety Evaluation May 26, 1982 Page 3 analog Rod Position Indication System.
This calibration will be derived from the RPI signal conditioner output voltage versus actual rod position data.
The computer calibration curve will be fit to this RPI calibration data on a rod by rod basis using multiple regression or other suitable means.
The degree of equation (up to fifth degree) finally adopted will be selected on the basis that a sufficient number of higher order terms will be used to enable the computer calibration curve to represent the actual rod position at thermal equilibrium within two steps, if possible.
This recalibration of the plant computer should eliminate most, if not all, rod deviation alarms which would occur during normal operation provided that extreme rod motion which could occur during plant maneuvering does not create severe thermal disequilibrium within the Rod Position Indication System.
This magnitude of rod motion is not expected during normal operation.
We believe that this recalibration of the plant computer addresses the NRC Staff concern related to rod deviation alarms.
3.
The NRC Staff has requested that we explain how we intend to demonstrate compliance with surveillance requirement 4.1.3.3 which requires that OPERABILITY of the group demand position indicators shall be demonstrated by a CHANNEL FUNCTIONAL TEST at least once per 18 month period.
This requires demonstration that the calibration of the group demand position indicators are within + 2 steps of the group demand.
To address this issue, it is necessary to discuss the control banks and shutdown banks separately due to differences in equipment arrangement between these control rod categories.
There are no part length rods installed at Beaver Valley; therefore, part length rod control features will not be discussed herein.
The rod control system used at Beaver Valley is a standard Westinghouse design utilizing a ratchet type of drive mechanism, consisting of two stationary coils and one moveable coil.
The coils are operated in sequence to move control rods one step at a time in response to signals generated by manual operator control or automatic control.
Figure 1 (attached) illustrates the logic diagram for the major components of the rod control system.
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Cycle 3 Reload Safety Evaluation May 26, 198; Page 4 Rod demand position indication is provided by counting pulses generated by the Rod Control System.
Display of the demand position is provided by 12 electromagnetic counters on Benchboard - Section B in the Control Room.
These counters monitor rod groups as follows:
Shutdown Bank A Group 1 Shutdown Bank A Group 2 Shutdown Bank B Group 1 Shutdown Bank B Group 2 Control Bank A Group 1 Control Bank A Group 2 Control Bank B Group 1 Control Bank B Group 2 Control Bank C Group 1 Control Bank C Group 2 Control Bank D Group 1 Control Bank D Group 2 This arrangement provides for two indicators for each bank of rods.
In addition, pulse to analog converters provide rod demand position signals to the computer.
For control banks, additional indication of demand rod position is available within the logic cabinet associated with the bank overlap controller.
This indicator is electronic and is provided with a selector switch for Control Banks A, B,
C and D.
Our method of demonstrating compliance with specification 4.1.3.3 will be to calibrate the demand position indicators by performing an inter-comparison between the applicable benchboard indicators and the logic cabinet indicators at various control rod positions.
Specifically, all demand position indicators l
will be set to zero with rods fully inserted.
The rods in each bank will be withdrawn to as close-to the 228 step l
position as is possible without exceeding the full-out l
position and the intercomparison described above will be recorded.
Rods will be inserted to a position as close to the fully inserted position as is possible without over-inserting the rods and a second intercomparison will be made.
If the associated benchboard indicators agree with the logic cabinet indicator within + 2 steps, compliance will be considered to have been demonstrated.
Performing this calibration on both rod withdrawal and insertion will assure that the electromechanical counters operate properly in both directions.
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Cycle 3 Reload Safety Evaluation May 26, 1982 Page 5 For shutdown banks, there is no readily available means for indicating demand position other than the benchboard counters described above.
However, since there are two counters per shutdown bank, we believe that an appropriate intercomparison can be made between these two indicators in accordance with the above procedure for control banks to demonstrate compliance with the specification.
Since the shutdown banks are fully withdrawn during power operation, the probability that the step counters associated with the shutdown banks will malfunction is small.
We note that it is possible to operate test push buttons in the rod control system which will insert pulses to operate the step counters.
We believe that performing the calibration of the control rod demand position using the push buttons is a satisfactory method to be used in lieu of actual rod motion.
Further, to obtain maximum accuracy of the rod deviation alarm, the group demand position signals to the plant computer will be calibrated in conjunction with the rod position demand indicator calibrations.
We believe that this information satisfactorily responds to the concerns expressed by the NRC_ Staff.
Should additional questions arise, do not hesitate to contact my office.
Further, we wish to point out that the proposed Technical Specifications submitted by our May 5, 1982 letter are required for entry into MODE 3.
Entry into Mode 3 is scheduled for June 4, 1982.
Very truly yours, J.
J. Carey Vice President, Nuclear Enclosures
COMMONWEALTH OF PENilSYLVAllIA)
SS:
COUNTY OF BEAVER f j On this 4 6 f/ day of Ndz4
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, before me, w //gu/d; ///%7vS/fn(< a Notary Publio in and for said Commonwealth 7
and County, personally appeared J. J. Carey, who being duly sworn, deposed, and said that (1) he is Vice President of Duquesne Light, (2) he is duly authorized to execute and file the foregoing Submittal on behalf of said Company, and (3) the statements set forth in the Submittal are true and correct to the best of his knowledge, information and belief.
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Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Cycle 3 Reload Safety Evaluation May 26, 1982 Page 6 cc:
Mr.
R. C.
Ilaynes, Regional Administrator USNRC Region 1 Mr. Peter Tam Mr.
D.
L. Wigginton BVPS Unit 1 Resident Inspector USNRC Document Management Branch