ML20085K473
| ML20085K473 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/16/1995 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20085K475 | List: |
| References | |
| TVA-BFN-TS-360, NUDOCS 9506230391 | |
| Download: ML20085K473 (12) | |
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Tennessee Vaney Aatnanty Post Oftce Box 2000. Decatur. Alabama 35009 JUNE 16, 1995 TVA-BFN-TS-360 10 CFR 50.90 U.S.
Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - UNITS 1,
2, AND 3 -
TECHNICAL SPECIFICATION (TS) 360 - TRAVERSING IN-CORE PROBE (TIP), OPERABILITY REQUIREMENTS In accordance with the provisions of 10 CFR 50.4 and 50.90, TVA is submitting a request for an amendment (TS-360) to licenses DPR-33, DPR-52, and DPR-68 to change the BFN TS for Units 1, 2,
and 3.
The proposed change would revise the TS to allow the TIP system to be considered operable with less than five TIP machines operable.
The proposed change would allow the data normally supplied by the inoperable TIP unit to be supplied by either substituting data from traverses of symmetric TIP locations or using normalized TIP readings calculated by the on-line core monitoring system.
TVA has determined that there are no significant hazards considerations associated with the proposed change and that the change is exempt from environmental review pursuant to the provisions of 10 CFR 51.22 (c) (9).
The BFN Plant Operations Review Committee and the BFN Nuclear Safety Review Board have reviewed this proposed change and determined that operation of BFN Units 1, 2,
and 3 in accordance with the proposed change will not endanger the health and safety of 260011 PDR ADOCK 05000259
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.j the public.
Additionally, in accordance-with'10;CFR j
. 50.91(b) (1), TVA' is sending a copy of this letter 'and -
enclosures-to the Alabama State Department'of Public=
. Health-t t to thisiletter'provides the description and l
evaluation of the proposed' change.
This1 includes-TVA's determination that the proposed change does not: involve a significant hazards consideration,'and is exempt from environmental review. contains copies ofsthe appropriate TS'pages-from Units 1, 2,
and 3 marked-up to j
show the proposed change. forwards the revised
'l TS pages for, Units 1, 2,
and 3 which incorporate the preposed change.
1 TVA requests 7that the revised TS be made effective within
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.30 days of NRC approval.
If you have any! questions regarding this change,:please telephone me at (205) 729-2636.
Since ely,g W
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.i Manager of Site-Licensing
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Enclosures f
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See:page 3 l
l Subscribed and sworn to before me-I
- f this,/26N1 day of 251V E 1995.
M AD ) k.
dmi Notary Public t
My Commission Expires Aly Commission Expires 10/0$/88
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Nuclear Regulatory Commission Page 3
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JUNE 16, 1995 cc (Enclosures):
Mr.
W.
D.
Arndt General Electric Company 735 Broad Street Suite 804, James Building j
Chattanooga, Tennessee 37402 l
Mr. Johnny Black, Chairman j
Limestone County Commission 310 West Washington Street Athens, Alabama 35611 Mr. Mark S.
Lesser, Acting Branch Chief U.S.
Nuclear Regulatory Commission 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. Joseph F. Williams, Project Manager U.S.
Nuclear Regulatory Commission i
One White Flint, North l
11555 Rockville Pike Rockville, Maryland 20852 Dr. Donald E. Williamson I
State Health Officer Alabama State Department of Public Health 434 Monroe Street Montgomery, Alabama 36130-3017 i
4 ENCLOSURE 1 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1, 2,
AND 3 PROPOSED TECHNICAL SPECIFICATION (TS) CHANGE TS-360 DESCRIPTION AND EVALUATION OF THE PROPOSED CHANGE I.
DESCRIPTION OF THE PROPOSED CHANGE The proposed change will revise the BFN Units 1, 2,
and 3 TS to permit the Traversing In-Core Probe (TIP) system to be considered operable with less than five TIP machines operable.
The proposed amendment will allow the utilization of substitute data in lieu of data from inaccessible TIP measurement locations.
The substitute data will be derived from either symmetric TIP measurement locations (under certain core conditions) or from normalized TIP data as calculated by the on-line core monitoring system.
When the reactor is operating in an octant symmetric (type A) sequence, certain Local Power Range Monitor (LPRM) strings will have counterparts that have comparable readings due to the symmetry of the core loading and the control rod pattern.
The symmetric TIP data from accessible locations may be substituted for inaccessible locations provided the core is octant symmetric and the total core TIP uncertainty for the present cycle is less than 8.7 percent.
Certain TIP locations which lie on the axis of symmetry do not have symmetric counterparts and some symmetric pairs are monitored by the same TIP machine.
Should these locations be inaccessible, TIP data would be generated by computer modeling of the core conditions using the on-line core monitoring system with the calculated data normalized to the available real data.
Use of the computer modeling methodology is not limited to the locations that lie on the axis of symmetry, nor does it require octant symmetry.
The computer modeling method may be used to gener te substitute TIP data for any TIP channel.
TVA's an: ysis, by General Electric (GE), supports the use of this fuethod for the generation of substitute TIP data for a total of nine TIP measurement locations, which is equivalent to the maximum number of locations for a single TIP machine.
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The proposed TS changes are described below.
1.
Units 1, and 2, TS page 3.1/4.1-11, Table 4.1.B.
Current Calibration Statement for LPRM Signal:
"TIP System Traverse (8)"
Proposed Calibration Statement for LPRM Signal:
"TIP System (8)"
2.
Unit 3, TS page 3.1/4.1-10, Table 4.1.B.
Current Calibration Statement for LPRM Signal:
"TIP System Traverse (8)"
Proposed Calibration Statement for LPRM Signal:
"TIP System (8)"
3.
Units 1, and 2, TS page 3.1/4.1-12, Notes for Table 4.1.B.
Current Note 8 reads:
"A complete TIP system trave.se calibrates the LPRM signals to the process computer.
The individual LPRM meter readings will be adjusted as a minimum at the beginning of each operating cycle before reaching 100 percent power."
Proposed Note 8 reads:
"The individual LPRM meter readings will be adjusted as a minimum at the beginning of each operating cycle i
before reaching 100 percent power.
TIP data for an inoperable measurement location'may be replaced by data obtained from that channel's redundant (symmetric) counterpart or by data obtained from the j
on-line core monitoring system, normalized with available operating measurements, provided the total number of simulated channels does not exceed nine."
4.
Unit 3, TS page 3.1/4.1-11, Notes for Table 4.1.B.
Current Note 8 reads:
"A complete TIP system traverse calibrates the LPRM signals to the process computer.
The individual LPRM meter readings will be adjusted as a minimum at the beginning of each operating cycle before reaching 100 percent power."
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fProposed NoteL8 reads:
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"The individual.LPRM meter readings will_be adjusted as a minimum at the:beginning:of each operating cycle-before. reaching 100 percent: power.
TIP: data for an inoperable measurement. location may.be(replaced by' z'
data ~obtained.from that' channel's redundant-(symmetric): counterpart'orfbycdata'obtained from the.
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- on-line core 1 monitoring system,Lnormalized with..
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- available operating measurements, provided the total ~-
number of-simulated channels does not exceed nine."
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Units 1,~and 2,ETS page 3.1/4.'l-20, TS. Bases, paragraph,Lfirst sentence.1
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1 Current Bases:
"The sensitivity of LPRM detectors decreases'with exposure to neutron flux at a slow-and approximately
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- constant rate."
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Proposed Bases:
l "The sensitivity of LPRM detectors changes with exposure _to neutron flux."
6.
Unit 3, TS page. 3.1/4.1-19,- TS' Bases, first paragraph,.
first sentence.
l Current Bases:
"The sensitivity of LPRM; detectors _ decreases with' l
exposureito. neutron flux at a slow and approximately constant rate."-
Proposed Bases:
"The sensitivity of LPRM detectors changes with.
exposure to neutron flux."
y 7.
Units 1, and 2, TS page 3.1/4.1-20, TS Bases, second paragraph.
. Current Bases:
" Compensation in the process computer for changes in.
LPRM sensitivity will be made by performing a. full core TIP traverse to update the computer calculated LPRM correction factors every 1000 effective full power hours."~
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I Proposed Bases:
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" Compensation in the process computer for changes in LPRM sensitivity will be made by using the TIP system and/or process computer to update the computer calculated LPRM correction factors every 1000 effective full power hours."
8.
Unit 3, TS page 3.1/4.1-19, TS Bases, second paragraph.
Current Bases:
" Compensation in the process computer for changes in LPRM sensitivity will be made by performing a full core TIP traverse to update the computer calculated LPRM correction factors every 1000 effective full power hours."
Proposed Bases:
" Compensation in the process computer for changes in LPRM sensitivity will be made by using the TIP system and/or process computer to update the computer calculated LPPM correction factors every 1000 effective full power hours."
II.
REASON FOR THE PROPOSED CHANGE The proposed amendment requests changes to the Browns erry Units 1, 2,
and 3 TS to allow the TIP system to be v
nsidered operable with less than five TIP machines t
.. arable.
The proposed amendment would allow the utilization of substitute TIP data in lieu of data from inaccessible TIP locations.
BFN TS (Table 4.1.B and Note 8 of Table 4.1.B) currently j
require that all five TIP machines and their associated i
hardware (TIP detector drive, readout equipment, and j
indexing mechanism) be operable.
It also requires that the five detectors be calibrated in a common location.
If these requirements are not met for each TIP unit, the TIP system is considered inoperable and cannot be used for calibration of the LPRM detectors or for monitoring core thermal limits [i.e., Average Planar Linear Heat Generation Rate (APLHGR), Linear Heat Generation Rate (LHGR), or Minimum Critical Power Ratio (MCPR)].
The Proposed TS amendment would allow the utilization of substitute TIP data derived from either symmetric TIP locations (under certain core conditions) or from normalized TIP data as calculated by the on-line core monitoring system.
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The proposed-TS amendmentuis intended to prevent-unnecessary load reductions cnr shutdowns that may be required by certain inoperable'TIP equipment.
The'two proposed methods of using-substitute TIP data (i.e.,
symmetric counterparts and/or computer modeling, using a 3-dimensional core simulator) are being used successfully-by other BWR licensees-(References 1,'2, and 3).
III.
SAFETY ANALYSIS BFN Units 1, 2, and 3 each have five gamma sensitive TIP-I machines that are used to-periodically determine the power i
distribution in the. core and to calibrate the LPRMs.
The TIP system consists of five. independent gamma photon detection units.
Each unit contains a small ion chamber 4
that is driven from outside the primary containment by-a j
-motor drive mechanism.
The detector is attached to the drive mechanism by means of a. flexible-drive cable.
Operation of the drive mechanism causes the ion chamber to be inserted into or retracted from the reactor core within i
individual TIP guide tubes.'
The TIP system provides a signal proportional to the axial l
neutron flux at 43 radial core locations.
This signal is used to provide:
Reliable calibration of the LPRM flux amplifier gains l
to compensate for changes in LPRM detector sensitivity that accompany prolonged neutron exposure i
Accurate core wide flux shapes to the process computer so power and exposure distributions can be calculated
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Accurate substitute inputs to the process. computer where LPRMs have failed The 43 LPRM strings are divided between the five TIP machines with one common LPRM assembly connected to all five TIPS for cross channel calibration.
Each TIP unit uses an indexing device to route the detector to the desired LPRM assembly.
The BFN Units 1, 2,.and 3,.
TS require normalization of the TIP detectors (process computer, On Demand'One program j
(OD1)] every 1000 effective fullpower hours (EFPH) for the l
performance of an LPRM calibration.
l The required LPRM calibration relates a known power distribution, as measured by the TIP system, to the then f
existing LPRM readings.
When the LPRMs are normalized to
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one another, to the TIP readings, and to a plant heat balance equation, the LPRMs provide a determination of the local power in six inch increments axially (nodes) along the 43 LPRM strings.
Outputs from the calibrated LPRMs are used in the Reactor Protection System (i.e., Average Power Range Monitor), the Rod Block Monitor, and the Process Computer.
Accuracy requirements for power distribution are defined by GE report, NEDE-32321, 3D Monicore (RL3D) Performance Evaluation Accuracy (Reference 4), which is part of the present reactor fuel licensing basis.
Specifically, Table 2.1 of NEDE-32321 requires the TIP readings to have a root mean square (rms) total nodal power uncertainty of no more j
than 8.7 percent for reload cores.
The accompanying Table 6.1 also applies to the power distribution as determined by the LPRM system.
Consequently, the accuracy in nodal power as determined by the LPRM system between TIP sets is included in the 8.7 percent rms uncertainty.
I Advances in process computer monitoring include the development of new mathematical techniques and algorithms I
combining three dimensional reactor physics theory with on-line core data, (e.g., LPRM readings).
One such l
methodology, currently in use at BFN, employs an adaptive learning algorithm using on-line as well as historical core data inputs to improve power calculations within the reactor physics model.
This is accomplished by effectively i
modifying the neutron leakage terms to force the calculated power distribution to match the measured power distribution as determined by the TIP system.
Subsequent calculations use the adaptive coefficients and LPRM readings during j
monitoring between TIP sets.
This reactor physics methodology is capable of calculating substitute normalized TIP data and utilizing it when measured TIP data is missing.
The methodology has been used to study the effect of operating with a failure to scan strings assigned to a TIP machine due to TIP machine failure.
Detailed statistical evaluations, described in NEDE-32321, of calculation results compared to identical calculation results with a TIP machine failure provide a TIP machine out-of-service uncertainty of 1.8 percent.
This small additional uncertainty, when combined with the other uncertainties _ associated with core monitoring, yields an overall uncertainty well below the limit for nodal power uncertainty.
When the reactor is operating in an octant symmetric (type A) sequence, certain LPRM strings will have counterparts that have comparable readings due to the j
symmetry of t'..e core loading and the control rod pattern.
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The symmetric TIP data from accessible locations may be substituted for inaccessible locations provided the core is octant symmetric and the total core TIP uncertainty is i
not exceeded.
The total TIP uncertainty for BFN is specified in the Updated Final Safety Analysis Report and is determined by plant implementing procedures.
Certain TIP locations which lie on the axis of symmetry do not have symmetric counterparts and some symmetric pairs are monitored by the same TIP machine.
Should these locations be inaccessible, TIP data will be generated by computer modeling of the core conditions using the on-line core monitoring system previously described, with the calculated data normalized to the available real data.
Use of the computer modeling methodology is not limited to the locations that lie on the axis of symmetry, nor does it require octant symmetry.
The computer modeling method may be used to generate substitute TIP data for any TIP channel.
TVA's analysis, by GE, supports the use of this method for the generation of substitute TIP data for a total of nine TIP measurement locations, which is equivalent to the maximum number of locations for a single TIP machine.
Therefore, it is concluded that the BFN TIP system can be operated within the design basis for TIP uncertainty, including performance of LPRM calibration, with a total of nine TIP measurement locations out of service indefinitely.
This is equivalent to the maximum number of raeasurement locations for a single TIP machine.
i IV.
FO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION TVA has concluded that operation of Browns Ferry Nuclear Plant (BFN) Units 1, 2,
and 3 in accordance with the I
proposed change to the TS does not involve a significant hazards consideration.
TVA's conclusion is based on its evaluation, in accordance with 10 CFR 50.91(a) (1), of the three standards set forth in 10 CFR 50.92(c).
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l A.
The propored amendment does not involve a sianificant increasc in the Drobability or consecuencer of an accident previous 1v evaluated.
The TIP system is not used to prevent, or mitigate the consequences of any previously analyzed accident or transient; nor are any assumptions made in any accident analysis relative to the operation of the TIP system.
The primary containment isolation function (TIP withdrawal) is not affected.
The proposed TS change does not alter the fundamental process involved in calibrating neutron instrumentation (LPRMs), but requires that only the equipment associated with the TIP channels necessary for recalibrating LPRMs and for El-7
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core monitoring functions be operable.
Collection and storage of TIP data without using all TIP channels is acceptable because TIP machine. normalization factors I
are ultimately derived from the most recent full-core i
TIP set, which intercalibrates the TIP machines in a common core location.
Additionally, the'use of symmetric detectors and analytical' values as substitute data for inaccessible TIP channels does not compromise the ability of the-process' computer to_accurataly represent the spatial neutron flux distribution of-the-reactor core.
The core monitoring methodology'is presently based on symmetry of rod patterns and fuel ~1oading.
This is not changed but extended to use a higher order of symmetry (octant. symmetry) which exists with " type A" sequence rod patterns.
Therefore, this change does not increase the probability or consequences of an accident previously evaluated.
i B.
The cronosed amendment does not create the nossibility of a new or different kind of accident from any accident previously evaluated.
The proposed change does not involve the installation of any new equipment, or the modification of any equipment designed to prevent or mitigate the
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consequences of accidents or transients.
Therefore, the proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated.
C.
The cronosed amendment does not involve a sianificant reduction in a marain of safety.
The total core TIP reading uncertainties will' remain within the assumptions of the licensing basis.
l Therefore, the margin of safety to the MCPR safety limits is not reduced.
The ability of the process computer to accurately represent the spatial neutron flux distritution for the reactor core is not compromised.
Additionally, the computer's ability to accurately predict the LHGR, APLHGR, MCPR rr.d its ability to provide for LPRM calibration is act compromised.
therefore, the proposed changes do not involve a significant reduction in a margin of safety.
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Y.
ENVIRONMENTAL IMPACT CONSIDERATION The proposed change does not involve a significant hazards consideration, a significant change in the types of, or a
significant increase in the amounts of any effluent that may be released offsite, or a significant increase in individual or cumulative occupational radiation exposure.
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of Therefore, the proposed change meets the eligibility criteria'for categorical exclusion set forth in 10 CFR
- 51. 22 (c) (9).
Therefore,. pursuant to 10 CFR bl.22(b), an environmental' assessment of-the-proposed change is not 7 -
required.
VI. REFERENCES 1.-
NRC letter to Georgia Power Company dated August 8, E
1994, Issuance of Amendment, Edwin I. Hatch Nuclear Plant, Unit 2 (TAC No. M89923) 2.
NRC letter to The Cleveland Electric Illuminating Company dated September 22, 1989, Amendment No. 25 to Facility Operating License No. NPF-58 (TAC No.
74498) 3.
NRC letter to Commonwealth Edison Company dated February 10, 1988, Issuance of Amendment Nos. 53 and 35 to Facility Operating License NPF-11 and NPF-18, La Salle County Station, Units 1 and 2 (TAC Nos.
66119 and 66120) 4.
General Electric Report, NEDE-32321, 3D Monicore (RL3D) Performance Evaluation Accuracy,. dated January 1994.
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