ML20083C962
| ML20083C962 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/18/1995 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20083C966 | List: |
| References | |
| TVA-BFN-TS-357, NUDOCS 9505230163 | |
| Download: ML20083C962 (6) | |
Text
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Bl4 Tennessee Valley Autnonty, Post Office Box 2000, Decatur. Alabama 35609 May 18, 1995 l
TVA-BFN-TS-357 10 CFR 50.36 U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
)
Docket Nos. 50-259 Tennessee Valley Authority
)
50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - UNITS 1, 2,
AND 3 -
REVISION TO TECHNICAL SPECIFICATION (TS) BASES (TS-357)
The purpose of this letter is to inform NRC of changes TVA made to the BFN Units 1, 2,
and 3 TS Bases.
TVA revised Bases Sections 2.1.B and 3.2 to clarify the design function of the Average Power Range Monitor rod block system.
Additionally, TVA revised Bases Section 3.5.M to reflect current information on core thermal-hydraulic instabilities. provides a description of the bases changes and the reason for these changes. contains copies of the appropriate Units 1, 2,
and 3 TS Bases pages marked up to I
the show the changes. forwards the revised Units 1,
2, and 3 Bases pages.
There are no commitments contained in this letter.
If you have any questions about these bases changes, please contact me at (205) 729-2636.
Si le of
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g o Salas Manager of Site Licensing Enclosures cc:
See page 2 9505230163 950518 PDR ADOCK.05000259 P
PDR s
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4, U.S. Nuclear Regulatory Commission Page 2 May 18, 1995 2nclosures cc (Enclosures):
Mr.
W.
D. Arndt General Electric Company 735 Broad Street Suite 804, James Building Chattanooga, Tennessee 37402 Mr. Johnny Black, Chairman Limestone County Commission 310 West Washington Street Athens, Alabama 35611 Mr. Mark S.
Lesser, Acting Branch Chief U.S.
Nuclear Regulatory Commiccion Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35611 Mr. J.
F. Williams, Project Manager U.S.
Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Dr. Donald E. Williamson State Health Officer Alabama State Department of Public Health 434 Monroe Street Montgonery, Alabama 36130-3017
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ENCLOSURE 1 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1, 2,
AND 3 REVISION TO TECHNICAL SPECIFICATION (TS) BASES (TS-357)
DESCRIPTION OF AND REASON FOR CHANGES I.
DESCRIPTION OF THE CHANGES A.
Bases Section 2.1.B -
TVA revised in its entirety, this section of Units 1, 2,
and 3 Bases to clarify the design function of the APRM rod block system.
These changes are provided below.
1.
Units 1, 2,
and 3 page 1.1/2.1-14 and 1.1/2.1-15, paragraph 2.1.B were revised to read as follow:
Reactor power level may be varied by moving control rods or by varying the recirculation flow rate.
The APRM system provides a control rod block to prevent rod withdrawal beyond a given point at constant recirculation flow rate and thus prevents scram actuation.
This rod block trip setting, which is automatically varied with recirculation loop flow rate, prevents an increase in the reactor power level to excess values due to control rod withdrawal.
The flow variable trip setting is selected to provide adequate margin to the flow-biased scram setpoint.
B.
Bases Section 3.2 - TVA revised this section of Units 1,
2, and 3 Bases to clarify the design function of the Average Power Range Monitor (APRM) rod block system.
These changes are provided below.
1.
Unit 1 page 3.2/4.2-68, the first paragraph; Unit 2 page 3.2/4.2-68, the second paragraph; and Unit 3 page 3.2/4.2-67, the second paragraph provide a discussion on control rod block function.
The first sentence of each paragraph currently reads:
The control rod block functions are provided to prevent excessive control rod withdrawal so that MCPR does not decrease to 1.07.
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L This sentence is revised to read as follows:
The control rod block functions are provided to generate a trip signal to block rod withdrawal if the monitored power level exceeds a preset value.
2.
Unit 1 page 3.2/4.2-68, the third paragraph; Unit 2 page 3.2/4.2-68, the fourth paragraph; and Unit 3 page 3.2/4.2-67, the fourth paragraph provides a discussion on the APRM rod block function.
Each paragraph currently reads as follows:
The APRM rod block function is flow biased and prevents a significant reduction in MCPR, especially during operation at reduced flow.
The APRM provides gross core protection; i.e.,
limits the gross core power increase from withdrawal of control rods in the normal withdrawal sequence.
The trips are set so that MCPR is maintained greater than 1.07.
This paragraph is revised to read as follows:
The APRM rod block function is flow biased and provides a trip signal for blocking rod withdrawal when average reactor thermal power exceeds pre-established limits set to prevent scram actuation.
l C.
Bases Section 3.5.M - TVA revised this section of the Units 1, 2,
and 3 Bases to reflect the current industry position on interim recommendations to address core tharmal-hydraulic instabilities.
The change is provided below.
i 1.
Unit 1, page 3.5/4.5-34; Unit 2, page 3.5/4.5-32; l
and Unit 3, page 3.5/4.5-35, deleted the first sentence in the fourth paragraph.
This sentence l
currently states that during regional oscillations, the safety limit MCPR is not approached until APRM oscillations are 30 percent peak-to-peak or larger in magnitude.
II.
REASON FOR THE CHANGES Part 1, Bases Section 2.1.B and 3.2 - TVA revised Units 1, 2,
and 3 Bases to clarify the design function of the APRM rod block.
Under the current licensing basis for transient analyses performed for Browns Ferry, no credit is taken for the operability of the APRM flow-biased rod El-2
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block'in mitigating the consequences of a Rod Withdrawal Error transient (the.A MCPR resulting from this transient is a function of the Rod' Block Monitor setpoint).
The revision to the TS Bases is consistent with the APRM.
4 system design basis found in the'FSAR Section 7.5.7..
t Part 2, BasesLSection 3.5.M TVA revised Units 1, 2,
i and 3 Bases ~to reflect the current industry position on interim recommendations to address core thermal-hydraulic instabilities.
Technical Specification (TS) 3.5.M was implemented at BFN in response.to NRC IE Bulletin 88-07, Supplement 1.
In 1988, General Electric (GE) recommended and NRC endorsed (Reference 1) interim corrective actions, l
which included use of'an immediate manual' reactor scram in i
the event of core thermal-hydraulic instability, as evidenced by.APRM peak-to-peak oscillations of greater than 10 percent.
At that time. qualitative studies had indicated that a 30 percent APRM oscillation magnitude would be necessary to challenge the MCPR safety limit.
I BFN incorporated the interim corrective actions into the TS prior to Unit'2 restart in May 1991.
However, by 1992, i
the Boiling Water Owners Group (BWROG) and GE had developed an analytical methodology.for determining MCPR margins during regional oscillations, and recognized that under some conditions it may be possible to violate the MCPR safety limit with the APRM signal oscillating at less than 10; percent peak-to-peak.
In 1992'the BWROG issued implementation guidance for the interim corrective actions (Reference 2) which reflected the new information available'on stability.
BFN incorporated this guidance into plant procedures; however, the TS Bases still contain the 1988 guidance.
This revision deletes the outdated information from the TS. Bases.
III.
REFERENCE 8 i
1.
NRC Bulletin No. 88-07, Supplement 1: Power i
Oscillations in Boiling Water Reactions (BWRs) 2.
BWROG-92030 dated March 18, 1992, Implementation Guidance for Stability Interim Corrective Actions l
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'i t ENCLOSURE 2 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1, 2,
AND 3 REVISION TO TECKNICAL SPECIFICATION (TS) BASES (TS-357)
MARKED PAGES' I.
AFFECTED PAGE LIST Unit 1 Unit 2 Unit 3 1.1/2.1-14 1.1/2.1-14 1.1/2.1-14 1.1/2.1-15 1.1/2.1-15 1.1/2.1-15 3.2/4.2-68 3.2/4.2-68 3.2/4.2-67 3.5/4.5-34 3.5/4.5-32 3.5/4.5-35 II.
MARKED PAGES See Attached.
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