ML20083M035
| ML20083M035 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/11/1995 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20083M038 | List: |
| References | |
| TVA-BFN-TS-359, NUDOCS 9505190089 | |
| Download: ML20083M035 (13) | |
Text
a ep nn Tennessee Vaucy ALthority. Post Office Box 2000. Decatur Alabama 35609 May 11, 1995 TVA-BFN-TS-359 10 CFR 50.90 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 -
TECENICAL SPECIFICATION (TS) 359 - SCRAM PILOT AIR HEADER LOW PRESSURE TRIP In accordance with the provisions of 10 CFR 50.4 and 50.90, TVA is submitting a request for an amendment (TS-359) to licenses DPR-33, DPR-52 and DPR-68 to change the TSs for Units 1, 2,
and 3.
The proposed change reflects the interim addition of the scram pilot air header low pressure trip function on Unit 3.
This trip function is currently reflected in the Unit 2 TSs.
In addition, a note in the table that specifies the reactor protection system instrumentation requirements is being clarified for all three units.
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 the public.
Additionally, in accordance with 10 CFR 50.91(b) (1), TVA is sending a copy of this letter and enclosures to the Alabama State Department of Public Health.
1GC040 49 9505190089 950511 PDR ADDCK 05000259 j
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U.S. Nuclear Regulatory Commission Page 2 May 11, 1995 to this letter provides the description and evaluation of the proposed change.
This includes TVA's determination that the proposed change does not involve a significant hazards consideration, and is exempt from environmental review. contains copies of the appropriate Units 1, 2,
and 3 TS pages marked-up to show the proposed change. forwards the revised Units 1, 2,
and 3 TS pages that incorporate the proposed change.
TVA requests that the revised TS be made effective within 30 days of NRC approval.
If you have any questions about this change, please contact me at (205) 729-2636.
Singerely.,
s s dro'sklas Man g of Site Licensing Enclosures cc:
See page 3 Subscribed and sworn tp,before me this llih day of mAu 1995.
nma k GuyTsevt Notary Public g mmbslon Expkos 10/06/98 My Commission Expires
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U.S. Nuclear Regulatory Commission Page 3 l,
May 11, 1995 L
cc-(Enclosures):
Mr. W. D. Arndt General Electric Company 735 Broad Street Suite 804, James Building Chattanooga, Tennessee-37402 Mr. Johnny Black, Chairman j
Limestone County Commission l
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 l
Atlanta, Georgia 30323 l
NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 l
Athens, Alabama 35611 Mr. Joseph 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 Montgomery, Alabama 36130-3017
V
!t ENCLOSURE 1'
' TENNESSEE VALLEY AUTHOAITY
-EROWNS PERRY NUCLEAR PLANT (EFN)
- UNITS 1, 2 AND 3-ll PROPOSED TECENICAL SPECIFICATION.(TS)-CHANGE TS-359 DESCRIPTION AND EVALUATION OF.TNE PROPOSED CHANGE I.
DESCRIPTION OF THE PROPOSED CHANGE In summary, the proposed change reflects-the interim' addition of the scram pilot-air' header low-pressure trip function on Unit 3.-'This proposed-change is consistent with the' current Unit 2 TS.
The scram pilot air header low pressure switch scram function performs the same function as'the high water level switches in.the Scram Discharge Instrument Volume. ' The scram pilot air header low pressure switch scram function'has also recently_ contributed to decreased plant availability.
Therefore, TVA intends to pursue the overall reactor protection system design issue ~
and the long term need for the scram pilot air header low-pressure switch scram function.
In addition,.a note in-the table that specifies the reactor protection system (RPS) instrumentation requirements is being clarified for all three units.
The specific changes are described below.
1.
The current requirements for RPS instrumentation are listed in Table 3.1.A, RPS (SCRAM) Instrumentation Requirements.
The scram pilot air header low pressure instrumentation will be added to this table on TS Page 3.1/4.1-3 for Unit 3 as shown below:
Min. No. of Modes in which Function Must Be Operable Oocrable Instr.
Channels Por Trip Shut.
Startup/
System (t)(23) Trio Function Trio Level Settina ~ shLwn Refuel (7)
Hot Standby BE Action (1) 2 Low Scram Pilot
- t50 psig X(2)
X(2)
X X
1.A Air Hendes Pressure
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2.
Note 2 for Table 3.1.A on TS Page 3.1/4.1-5 for Unit 1 is revised as follows:
Current note:
" Scram discharge volume high bypass may be used' in. shutdown or refuel to bypass. scram discharge volume scram.with control rod block for reactor
-protection system ~ reset."..
Proposed note:
"The scram discharge volume high water level. bypass may be used.in SHUTDOWN or REFUEL to bypass the scram. discharge volume.high-high water level scram signal.in order to reset the reactor protection system trip.
A control. rod withdraw block'is-
'present when this scram signal is bypassed."
3.
Note 2 for Table 3.1.A on TS Page 3.1/4.1-5'for' Unit 2 is revised as follows:
Current note:
" Scram dischargeLvolume_high bypass may be used in SHUTDOWN or; REFUEL.to bypass scram discharge volume
. scram and scram pilot air header. low pressure' scram
]'
with control rod block for reactor protection system reset."
Proposed note:
"The scram discharge volume high-water level bypass may.be used in SHUTDOWN or REFUEL to bypass both the scram discharge volume high-high water level and scram pilot air header lov pressure scram' signals in order to reset the reactor protection system trip.
A control rod withdraw block is present when these scram signals'are bypassed."
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Note 2 for Table 3.1.A on TS Page 3.1/4.1-4 for Unit 3 is revised as follows:
Current note:
-" Scram discharge volume high bypass may be used in shutdown or refuel to bypass scram discharge-volume scram with control rod block for reactor protection system reset."
Proposed note:
"The scram discharge volume high water level bypass may be used in SHUTDOWN or REFUEL to bypass both the scram discharge volume high-high water level and scram pilot air header low pressure scram signals in order to reset the reactor protection system trip.
A control rod withdraw block is present when these scram signals are bypassed."
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Note 7'for Table 3.1.A on TS Page 3.1/4.1-4 for Unit 3
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is revised as follows:
Current note:
"When the reactor is-subcritical and the reactor water temperature is less.than 212*F,,only the' l
~following trip functions-need to be OPERABLE:
A.
Mode switch in SHUTDOWN B.
Manual' scram C.
High flux IRM' D.
. Scram discharge volume high level E.
APRM 15; percent scram" Proposed note:
"When the reactor is subcritical and the reactor water temperature is less.than 212*F, only the following trip functions need to be OPERABLE:
A.
Mode switch in SHUTDOWN B.
Manual scram.
C.
High flux IRM 1
D.
Scram discharge volume high level E.
F.
Scram pilot air header low pressure" I
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- 6. The current functional tests.and-the' minimum functional-test frequencies-for safety related RPS instrument and control circuits are listed in Table 4.1.A.
The low scram pilot air header pressure instrumentation will be:
added.to this table on TS Page'3.1/4.1-8 for Unit 3 as shown below Group (2)
Functannal Test Minamum Frcouencvd)
Low scram Pilot Air Hender.
'A Trip Channel and Alarm once/6 Months Pruesure (PS 85-35 A1, A2, B1,
& B2) -
- 7. The current RPS instrument calibration minimum calibration frequencies for reactor protection instrument. channels are listed in. Table 4.1.B.
The low-scram pilot air header pressure instrumentation'will be added to this table on TS Page 3.1/4.1-10 for Unit 3 as shown below:
Instrument Channel Groun (1)
Cahbration Minimum Freauencv(2)
Low Scram Pilot Air.
A Standard Pressure Source once/18 Months-Header Pressure (PS 55 35 Al, A2, B1, & B2) 1 8.- Bases Section 3.1, TS Page 3.1/4.1-15 for Unit 3 is revised as follows:
Current Bases:
"The high reactor pressure, high drywell
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pressure, reactor low water level.and scram discharge volume high level scrams are required for STARTUP and RUN modes of plant operation."
Revised Bases:
"The high reactor pressure, high drywell pressure, reactor low water level, low scram pilot-air header pressure and scram discharge volume high level scrams are required for.STARTUP and RUN modes of plant operation."
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The following discussion will-be.added to' Bases Section 3.1, TS Page 3.1/4.1-15 for Unit 3.
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"The low scramLpilot. air' header-pressure trip
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performs 1the same function as the high water level in the scram discharge instrument volume for. fast fill eventsiin.which the'high level-instrument response time'may be inadequate.
A-fast fill event is postulated.for certain degraded control air events in which the scram
.4 outlet valves unseat enough to-allow 5 gpa per drive leakage into the scram discharge volume but not enough to cause control rod insertion."
i 10.
Corrects the capitalization of the terms " operable" and " inoperable" on the affected Units 1, 2 and 3 TS pages in order to conform with the current TS t~
Definitions'section.
II.
REASON FOR THE PROPOSED CHANGE The scram pilot air header low pressure trip function g
L performs the same protective function as the existing scram discharge volume (SDV) high water level-trip.
Both trip 1
functions. ensure'that a reactor scram is initiated while sufficient _ volume remains in the SDV to accept discharged water from the control rod drives ( CRDs) '.
For a postulated
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' low air header pressure event,.where the scram outlet
. valves leak but do not fully open, the rate at which water could be introduced.into the SDV may cause the volume to fill with water before the high level switches can initiate a reactor scram.
The low air header pressure trip function.
provides added protection against this scenario'and is being added to the Unit 3 TSs.
In addition, the description of-the SDV high water level bypass in the Units 1, 2, and 3 TSs requires clarification in order to reduce the potential for misinterpretation.
l III.-
SAFETY ANALYSIS During a routine shutdown of BFN Unit 3 on June 28, 1980, 76 of 185. control rods failed to fully insert in response to a manual scram from approximately 30 percent power.
All rods were subsequently inserted within.15 minutes and no
' reactor damage or hazard to the public occurred.
- However, the event did cause an in-depth review of the Boiling Water Reactor (BWR) CRD system, which identified design deficiencies that required corrective measures.
These measures were set forth in the generic Safety Evaluation El-6 I
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-Report (SER), which was transmitted by'NRC letter to All J-BWR' Licensees, dated December 9, 1980, BWR Scram Discharge
. system.. The overall scram system design, with the addition of the scram pilot air header low pressure trip function, satisfies the criteria contained in the generic SER.
The scram. pilot air header low pressure' trip (which'was
. originally implemented generically as a short-term solution) performs the same protective function as the SDV.
high water. level trip.
Both trip functions ensure that a reactor scram is initiated while sufficient volume remains in the SDV to accept discharged water from the CRDs.
The scram inlet and outlet valves are held closed by the air pressure in the scram air header.' The scram outlet valves begin to unseat as the air pressure drops below i
43 psig-(which is higher than the pressure that scram inlet valves begin to. unseat).
The scram pilot air header low pressure switches detect losses in air pressure and initiate an anticipatory scram to ensure the scram is complete prior to the possible onset'of hydraulic locking.
in the SDV.
The proposed trip level setting of 50 psig is conservative and assures a trip signal and successful reactor scram is accomplished prior to hydraulic locking occurring in the SDV as a result of significant flow past the scram outlet valves.
I In addition, the description of the SDV'high water level bypass in the Units 1, 2,
and 3 TSs is being revised.to more concisely depict.the function of the SDV high water level bypass..
IV.
NO SIGNIFICANT HAEARDS CONSIDERATION. DETERMINATION TVA has concluded that. operation of BFN Units 1, 2, and 3 in accordance with the proposed-change to the TSs 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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Tha_ PEAR 20ed_ammadment does_not involve a'sianificant inacease in the archability or conseeuences of an accident nreviousiv evaluated.
The scram pilot air header low pressure switches perform the same function as the high water level switches in the scram charge instrument volume.
They automatically initiate control rod insertion (SCRAM) in the event that degraded conditions are detected in the BWR CRD System.
Since the scram pilot air header pressure trip function ensures that the CRD System is available to mitigate the consequence of an accident or i
transient, and the addition of the scram pilot air header low pressure _ trip scram function does not affect the precursors for any accident or transient analyzed in Chapter 14 of the BFN Updated Final Safety' Analysis Report (UFSAR), there is no increase in the probability of any accident previously evaluated.
The design criteria for the scram system is contained in the generic SER, which was transmitted by NRC letter to All BWR Licensees, dated' December 9, 1980, BWR Scram Discharge System.
The scram pilot air header pressure trip function ensures that the CRD System is available to mitigate the consequence of an accident or transient, and the overall scram system design, with the addition of the scram pilot air header low pressure trip function, satisfies the criteria contained in the generic SER. Since the scram function would be successfully performed, the addition of the scram pilot air header low pressure trip scram function does not involve a significant increase in the consequences of any accident previously evaluated.
The clarification of the description offthe SDV high water level bypass in the RPS does not, by itself, reflect a modification to plant equipment, maintenance activities, or operating instructions.
The revised description does not effect the precursors for any accident or' transient analyzed in Chapter 14 of the BFN UFSAR or equipment used in the mitigation of these accidents or_ transients.
Therefore, there is no increase in the probability of any accident previously evaluated nor an increase in the consequences of any accident previously evaluated.
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3.
The nronosed==anAm*MI does not Create the Dossib111tY
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of a new or different kind of accident from any accident previously evaluated.
The scram pilot air header low pressure trip performs the same protective: function as the SDV high water leve1~ trip.
Both trip functions ensure that'a reactor scram is initiated while sufficient volumeiremains in the SDV to' accept discharged water from the'CRDs.
The scram inlet and outlet valves are held closed by
.the air pressure in the scram air header.
The scram outlet valves begin to unseat as the air pressure drops below 43 psig (which'is higher than the pressure that scram inlet valves begin to unseat).
The scram pilot air header low pressure switches detect losses in air pressure and initiate an anticipatory scram to ensure C
the scram is complete prior to-the possible onset of hydraulic locking in the.SDV.
The proposed trip level setting of 50 psig-is conservative and assures a trip.
signal and successful reactor scram is accomplished =
prior to hydraulic locking occurring in the SDV as a result of significant flow past the scram outlet valves.
The overall scram system design, with the addition of the scram pilot air header low pressure trip function is in conformance with the generic SER.
No new system failure modes are created as a result of adding the scram pilot air header low pressure trip scram function.
Therefore, the addition of the scram pilot air. header low pressure trip scram' function _does not create the possibility of a new or different kind of accident from any accident previously evaluated.
4 The clarification of the description of the SDV high water level bypass in.the RPS does not, by itself, reflect a modification to plant equipment, maintenance-activities, or operating instructions.
No new external threats, system interactions, release pathways, or equipment failure modes are. created.
Therefore, the.
clarification of this description does not create the possibility of a new or different-kind of accident from any accident previously evaluated.
C.
The nroposed amendment does not involve a sianificant reduction in a marain of safety.
The overall scram system design, with the addition of the scram pilot air header low pressure trip function is'in conformance with the generic SER.
Since the scram system would successfully operate to mitigate the consequences of accidents and transients previously El-9
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c analyzed, the proposed amendment does not involve a significant reduction in the margin of safety.
.The clarification'of the description of the SDV high water level bypass in the RPS does not, by itself, reflect a modification to plant equipment, maintenance activities, or operating instructions.' There.is no change to the licensing or design basis of the RPS.-
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'Therefore, the revised description does not involve a significant reduction in the margin of safety.
V.
ENVIROMMENTAL IMPACT CONSIDERATION The proposed change does not involve a significant hazards consideration, a significant_ change in the types of.or significant increase in the amounts of any effluents that may be released offsite, or a significant increase in individual or cumulative' occupational radiation exposure.
Therefore, the proposed. change meets the. eligibility criteria for categorical exclusion set.forth in 10 CFR 51.22 (c) (9).
Accordingly, pursuant-to 10 CFR 51.22(b), an environmental assessment of-the proposed change is not required.
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