ML20066D293
| ML20066D293 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/02/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20066D288 | List: |
| References | |
| NUDOCS 9101140304 | |
| Download: ML20066D293 (6) | |
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1 ENCLOSURE 2 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.183 TO FACILITY OPERATING LICENSE NO. DPR-52 JENNESSEEVALLEYAUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-260
1.0 INTRODUCTION
By letter dated August 6, 1990, the Tennessee Valley Authority =(TVA), requested changes to the Technical Specifications (TS) for Browns Ferry Nuclear Plant, Unit 2.
TVA also provided additional information regarding its TS amendment request by letter dated October 9, 1990.
The change is to the trip setting for the Level 1 low reactor pressure vessel (RPV) water level. During the process of generating setpoint and accuracy calculations for plant parameters for which no calculational basis could be found, it was determined that the trip setting for the Level 1 low RPY water level was not conservatively based.
2.0 DISCUSSION l
A summary of the proposed changes to the reactor pressure vessel (RPV) level instruments are as follows:
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o-Trip Level Setting changed from 378 to 398 inches above vessel zero (IAVZ) - LIMITING SAFETY SYSTEM SETTING (LSSS),
Analytical limit changed from 378 to 372.5-IAVZ - SAFETY LIMIT (SL) o o
Revise the bases section, i
o Remove exception to operability requirements for certain reactor low-water level instruments during the time the RPV water level modifications are being performed.
Thera are no proposed TS changes to the minimum-number of _ operable instruments, action statement, surveillance requirements for frequency'of functional or calibration testing.
I The reactor vessel water level 1 instruments, 2-LS-3-58A-D and 2-LIS-3-56A-D, are used to measure reactor pressure vessel (RPV) water level. At the existing setpoint, 378 IAYZ, low water level causes the initiation of the following systems:
o containment spray system (CSS) i o
low pressure coolant injection system (LPCI) o main steamline isolation o
permissive inputs to the automatic depressurization system (ADS) 9101140304 910102 l
PDR ADOCK 05000260 l
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2 3.0 EVALUATION The original LSSS reactor vessel low water level value in TS Table 3.2.A and Table 3.2.B was equal to the SL of 378 inches above vessel zero (IAYZ). Section 50.36 " Technical Specifications" of 10 CFR 50 requires "Where a limiting safety system setting [LSSS) is specified for a variable on which a safety limit [SL) has been placed, the setting shall be so chosen that automatic protective action will correct the abnormal situation before a safety limit is exceeded."
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This requirement of 10 CFR 50.36 cannot be achieved if the LSSS is equal to the SL. The LSSS must be set to actuate at a higher reactor vessel water level l
l than the SL to account for instrument inaccuracies, loop inaccuracies, response time of; instrument channels, logic relays, isolation valves closing, or motor breaker closing, pump acceleration time, and injection water flow into the reactor vessel. Therefore, the licenser. proposed to change the LSSS from 378 l
to 398 1AVZ to assure the SL is not exceeded, and still prevent inadvertant actuation from normal operating level transients. The LSSS is 37-11/16 inches above the top of the reactor core (which is at 360-5/16 IAYZ).
The Level 1 low RPV water level trip level setting of 398 IAVZ is the limiting value that instrument setpoint can have when tested periodically, beyond which the instrument channel is declared inoperable and corrective action must be taken.
TVA stated: "The analytical limit [SL) provided by GE [ General Electric Company]
was used as a design input to a scaling and setpoint calculation which deter-mined the nominal trip setpoint and trip level setting [LSSS] based on inaccu-racies associated with the instrument loops.
The allowance for instrument inaccuracies in determining the actual trip setpoint provides conservative assurance that the trip function will be performed at or before reaching the analytical limit [SL)."
TVA performed a Setpoint and Scaling Calculation to determine the accuracy of the instruments and loops. This accuracy was compared to the required accu-racies to assure that there is sufficient margin between the setpoints and the operating limits, and the safety limits.
staff at TVA's Rockville office were as follows:The calculations reviewed by the Instrument No.
Calculation No.
Revision No.
2-LT-3-56A ED-02003-88122 3
2-LT-3-56B ED-Q2003 88123 3
2-LT-3-56C ED-Q2003-88124 3
2-LT-3-56D ED-Q2003-88125 3
2-LT-3-58A ED-Q2003-880126 4
2-LT-3-58B ED-Q2003-880127 4
2-LT-3-58C ED-Q2003-880128 4
2-LT-3-58D ED-Q2003-880129 4
The staff's review of the calculations verified that TVA addressed instrument and loop errors for normal operation and accident conditions associated with the following sources:
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o temperature o
power supply o
pressure o
seismic o.
zero o
radiation o
span o
water leg o
repeatability o
condensate pot location o
drift o
vessel growth The vendor's errors were extrapolated to 18 months plus 25%, which is 22-1/2 months. This is the maximum calibration interval.
The methodology for determination of instrument setpoints used by TVA was in accordance with Regulatory Guide (RG) 1.105 that endorses Instrument Society of America (ISA) Standard ISA-567.04 - 1982 "Setpoint for Nuclear Safety Related Instrumentation Used in Nuclear Power Plants". This standard provides guidance for ensuring that setpoints stay within TS limits.
The level instruments affected by this amendment, specified in the Setpoint and Scaling Calculations, are Rosemount models that have been identified in a 10 CFR Part 21 report, submitted by Rosemount, and NRC Bulletin 90-01 as being susceptible to failure under certain conditions. This failure is caused by leaking silicon oil from between the isolating diaphragm and sensing diaphragm of the instrument. The loss of silicon oil causes the transmitters to exhibit reduced performance (output shift lack of response over their full range, and/or increase in response time), prior to detectable failure. The safety ioncern is a common cause failure since the redundant instruments are the same manufacture and model. Although there has not been a TS change to the surveil-lante frequency, TVA has committed to comply with the Bulletin and Rosemount
'iechnical Bulletin Number 4.
TVA's program included the development of proce-dures for increased surveillance. These procedures are Procedure Nethod PM89-02 R1 (EE)
- Handling of Rosemount Transmitters" and Procedure No.
SII-2-XT-00-165, R0 "Rosemount Transmitter Special Monitoring Program."
In the NRC letter of September 7,1990, TVA was requested to provide documen-tation (surveying records) for the RPV zero elevation which is the reference for all water level instruments. TVA responded to this request by making available, at their Rockville office, a copy of a General Electric drawing 729E424 " Nuclear Boiler Vessel Instruments." The staff reviewed Revision 11 of this drawing and verified that the elevation listed on the drawing as 578 feet three inches above sea level was used in the calculations, and the drawing is referenced in the calculation in the " Source of Design Input Information (References)."
On November 15, 1990, TVA informed the staff "that documentation of the BFN Unit 2 vessel [ reactor pressure vessel) zero elevation is on file in the BFN licensing TS record file." The pertinent information excerpted from the docu-mentation dated September 14, 1971, and signed by H.L. Johnson was reviewed by the staff. The RPV zero elevation agreed with the elevation on drawing 729E424, Revision 11. The staff has no further concerns about the BFN Unit 2 RPV zero elevation.
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Changing the LS$$ will revise: Table 3.2. A instruments 2 LIS-3 56A-D; Table 3.2.B instruments 2-LS 3-58A-D; a Table 3.7. A note; and Bases Sections 1.2 and 3.7/4.7.
In this TS amendment, TVA is also deleting information which was added to the TS as a temporary amendment.
The temporary amendment was requested in their application dated October 14,1988, w11ch the staff issued as Amendment No.158 in a letter to TVA dated December 15, 1988. Amendment No.158 sodified the Limiting Condition for Operation which required specific conditions to be met when work involving the reactor vessel was being performed.
The specific instruments involved in the change to the OPERABLE definition were level instruments 2 LIS 3-203A-D and 2415-3-58A D.
The work on the reactor vessel involved installation of instrumentation for detection of inadequate core cooling in accordance with the NUREG-0737, item !!.F.2. Modifications were also made to the instru:aent sensing in accordance with TVA's response to Generic Letter 84-23. This work has been completed and Amendment 158 is no longer necessary.
4.0 ENVIRONMENTAL CONSIDERATION
3 This amendment involv 6 a change to a requirement with respect to the use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts and no significant change in the types of any effluents that may be released offsite, and that there is no significant Increase in individual or cumulative occupational radiation exposure. The Connission has previously issued a proposed finding that this amendment involves no signifi-cant hazards cunsideration and there has been no public comment on such finding (55FP.36353). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental imaact statement nor environmental assessment need be prepared in connection wit 1 the issuance of the amendent.
5.0 CONCLUSION
Based on our review of the material submitted by the licensee, we find the pro-posed changes acceptable. The proposed changes to the LSSS and SL settings are acceptabic because they are based on a value derived by approved calculational means. This change ensures that trips occur within the analytical limit used to confirm the design bases of the plant.
The deletion of a temporary amend-ment which modified the LCO requiring specific conditions be met when work involving the reactor vessel was performed is acceptable because the time for its need has passed.
TVA has a program to address the transmitter problems identified in Rosemount 10 CFR Part 21 report and NRC Bulletin 90-01.
The-adequacy of this program will be determined by the staff under separate correspondence and outside the scope of this safety evaluation.
The staff has no further concerns about the RPV zero elevation documentation since the survey records are now in the BFN licensing TS files.
5 The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not. be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendments will not be inimical to the comon defense and security nor to the health and safety of the public.
Principal Contributors:
S. M. Chatterton F. Paulitt Dated: January 2, 1991 l
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Mr. Oliver D. Kingsley, Jr.
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Mr. Marvin Runyon, Chairman Mr. O. J. Zeringue, Site Director Tennessee Valley Authority Browns Ferry Nuclear Plant ET 12A 7A Tennessee Valley Authority 400 West Sumit Hill Drive P. O. Box 2000 Knoxville, Tennessee 37902 Decatur Alabama 35602 Mr. Edward G. Wallace Mr. P. Carier, Site Licensing Manager Manager, Nuclear Licensing Browns Ferry Nuclear riant end Regulatory Affairs Tennessee Valley Authority Tennessee Valley Authority P. O. Box 2000 EN 157B Lookout Place Decatur, Alabama 35602 Chattanooga, Tennessee 37402-2801 Mr. John B. Waters, Director Mr. L. W. Myers, Plant Manager Tennessee Valley Authority Browns Ferry Nuclear Plant ET 12A 9A Tennessee Valley Authority 400 West Sumit Hill Drive P. O. Box 2000 Knoxville, Tennessee 37902 Decatur, Alabama 35602 Mr. W. F. Willis Chairman, Limestone County Comission Chief Operating Officer P. O. Box 188 ET 12B 16B Athens, Alabama 35611 400 West Sumit Hill Drive Knoxville, Tennessee 37902 Claude Earl Fox M.D.
StateHealthOfficer General Counsel State Department of Public Health Tennessee Valley Authority
. late Office Building 400 West Sumit Hill Drive Montgomery, Alabama 36130 ET llB 33H Knoxville, Tennessee 37902 Regional Administrator, Region II U.S. Nuclear Regulatory Comission Mr. Dwight Nunn 101 Marietta Street, N.W.
Vice President, Nuclear Projects Atlanta, Georgia 30323 Tennessee Valley Authority 6N 38A Lookout Place Mr. Charles Patterson 1101 Market Street Senior Resident Inspector Chattanooga, Tennessee 37402-2801 Browns Ferry Nuclear Plant U.S. Nuclear Regulatory Comission Dr. Mark O. Medford Route 12, Box 637 Vice President, Nuclear Assurance, Athens, Alabama 35611 Licensing and Fuels Tennessee Valley Authority Tennessee Valley Authority 6N 3BA Lookout Place Rockville Office Chattanooga, Tennessee 37402-2801 11921 Rockville Pike Suite 402 Rockville, Maryland 20852
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