ML20030D854

Safety Evaluation Supporting Amends 75 & 72 to Licenses DPR-33 & DPR-52,respectively

ML20030D854
Person / Time
Site:	Browns Ferry
Issue date:	09/03/1981
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20030D853	List: ML20030D852 ML20030D854 ML20030D856
References
NUDOCS 8109170072
Download: ML20030D854 (16)

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,gv v SAFETY EVALUATION BY,) 'E OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 75 TO FACILITY OPERATING LICENSE NO. OPR-33 NENDMENT' NO. 72 TO FACILITY OPERATING LICENSE NO. DPR-52 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR' PLANT, UNITS NOS.1 AND 2 DOCKET NOS. 50-259 AND 50-260- .. -, ~ 1.' O Introduction O } (.TVA BFNP 156) and suppl nted by By latter dated April 9, {9jl2, July 2,1981( , July 31,1981 and letter dated June)8,1981 August 17, 1981(5, the Tennessee Valley Authority'(the. licensee or TVA) requested changes to the Technical Specifications (Appendix A) appended to Facility Operating License Nos. DPR-33 and DPR-52 for the Browns Ferry Nuclear Plant, Unit Nos.1 and 2. The proposed amendments and revised Technical.' Specifications would accommodate operation of Browns Ferry Unit Nos i and 2 (.BF-1 and BF-2) with a modified electric distribution system. The electrical modifica-tions, reanalysis of the electrical systems r.nd changes to the Technical Specifications also resolve the generic issues of degraded grid protection for class IE power systems and adequacy of station electric distribution system voltages for BF-1 and BF-2. These issues wera raised by NRC's generic letters of June 3,1977, August 8,1979 and December 13, 1979 and responded to by TVA in their letters of July 22, 1977, May 2,1978, May 12,1978, September 4,1979, March 14,1980 and May 1,1980 as well as in the submittal of April 9,1981 referred to initially. 2.0 Backcround As a result of a degraded grid voltage occurrence at Millstone. Unit No. 2 on July 5,1976, we sent a letter to TVA and other licensees on August 12, 1976(6) requesting that each utility conduct an investigation of plart and equipment operation during a degraded gg1d voltage condition. After reviewing the information submitted by At and other licensees we issued a generic letter on June 3,1977 8) to TVA and other licensees requesting that TVA (and the other licensees for their facilities) assess the susceptibility of the safety-related electHcal equipment at the Browns Ferry Nuclear Plant to a sustained voltage degradation of the offsite source and the interaction of the offsite and onsite emergency power systems. The letter contained three positions with which the current design of the plant was to be compared. After comparing the 9109170072 810903 PDR ADOCK 05000 P

l, cur. , design to the stat..cositions, TVA was required to either propose ,odifications to satisfy the positiets and criteria or furnish an analysis to substantiate that the existing fac);'ty design has equivalt.- t capabilities. TVA responded initially on July 22,19.77(9) and concluded, at that time, that the addition of a second level of voltage protection 'with a time delay was not necessary. On October 17, 1977, while BF-1 and BF-3 were in a shutdown.cor.11 tion, Unit 2 tripped from essentially full load. There were indications that icw voltages on Browns Ferry' buses connected to the offsite system might have contributed to the cause of the trip. TVA initiated a detailed evaluation of the Browns Ferry inplant voltage levels that might result from aberrations in the offsite power supplies, including computer model studies. These studies indicated that under certain postulated conditions, an undervoltage condition might exist. Following a meetg)with the licensee,b] letters dated May 2,1978(10) and May 17, 1978 , TVA submitted a p~oposed design of short term modifications and proposed changes to the Technical Specifications to correct the possible undervolipca condition. The design was approved by our letter 'of May 31,1978t'2}; the ammdments changinTgithe Technical Specifications were issued by our letter of June 23, 1978(13). As a result of their retvaluation of degraded g-id voltage conditions, TVA also(sp1mitted a revision to their letter of July 22,1977 on May 12, 1978 8 in which they concluded that the installation of a second level of voltage protection for the onsite power system was necessary. Engineering design was also started on the permanent modifications to the Browns Ferry slectrical systems,.which are the subject of this safety evaluation. On September 16, 1978, an event at Arkansas tiuclear One (Af;0) station, which is described in f4RC OIE Information flotice No. 79-04, brought into question the conformance of the station electric distribution system to GDC-17. As a result of our review of this event, on August 8,1979 we issued a generic letter to all power reactor licensees regarding " Adequacy of Station Electric Distribution Voltages"(15). This letter required each licensee to confirm, by analysis, the a~dequacy of the voltage at the class lE loadi. This letter included 13 sprific guide-lines to be followed in determining if the load terminal voitage is adequate to start and continugys]y operate the class lE loads. In their response of September 4,1979t 501 TVA advised us that an actual transient at Browns Ferry " confirmed that with -theishort-term modifications in place, acceptable in-plant conditions (voltage) were maintained" and that this issue would be included in the engineering evaluation and design of the permanent modifications. A description of the grid system and interconnections and the plant electrical power system that will exist following the modifications is included in the revised chapter 8 to the Final Safety Analysis Report (FSAR) which was incorporated in IVA's April 9,1981 submittal. The most significant changes that have been completed as part of the permanent modifications include: 1 addition of a seventh 500 kV sransmission line from the Cordova Substation l Memphis, Tenn.) to Browns Ferry.

i 2. second level undervoltage protection was added to the 4160 volt shutdown boards for all three units at previous shutdowns-to ensure that upon a voltage degradation, the shutdown boards are supplied from an onsite power system (i.e., diesel generators). 3. capacitors were added to each cooling tower lift pump and to each unit's condenser circulating water pump. 4. generator low-side breakers are being added to all three units. 5. load tap-changing is being added to the unit station service trans formers. 6. a 42 Mvar and a 39 Mvar capacitor bank were installed prevously on the 161-kV system to improve power factors under high inplant load demand situations.- 7. upgrade the 161 kV capacitor bank controls.

3.0 Discussion

Sytem Descriotien e.Blant Electrical Power System Under normal operating conditions, units 1 and 2 are supplied electric ' power from their associated main generator via the unit station service trans formers. During normal startup and shutdown the unit's main generator is isolated by a generator br eaker,,and electric power ir ~ supplied to the unit auxiliary power system from the 500-kV grid via the ~ main transformers. If electric power from the 500-W grid is unvail: ble to a particular unit, power is then supplied from two 161-kV transmission lines via two common station service transformers. In addition, two cooling tower transformers prwide a bactup source of power for units 1 and 2 shutdown loads via the bus tie board. ~ The standby source of auxiliary powe: is from four diesel generator units. These units start automatically on loss of voltage or a degraded voltage on the associated shutdown board from self-contained starting air systems. In the long term following an accident, units 1 and 2 dierel generators will be paralleled with their unit 3 counterparts (

Reference:

FSAR Section 8.5.4.1) Figure 8.3-lb, attached to this safety evaluation, shows the electrical distribution systems for Browns Ferry Units 1 and 2 is from the material submitted by TVA.(2) The four shutdown boards (A, B, C and D) are powered by rhutdown buses 1 o'r 2, which derive their power from unit boards lA or 2B and 18 or 2A respectively. Shutdown buses 1 and 2 can also be powered by the 4 kV bus tie board associated with Unit 3. The unit boards are normally powered by the 500-kV swMchyard through the Unit Station Service "~ransformers (USST) 18 and 28. A generatcr breaker isolates the unit generator from the intemidiate voltage (22 kV) isolated phase bus on a unit trip. Unit boards lA, 1B, 2A and 2B can also be powered by the 161 kV grid via the Common Station Service Transformers (CSST) A or B. The 4 kV bus tie is also connected to the 161 kV grid via cooling tower transformers (CTT) I and 2. Therefore, 4 kV shutdown boards A, B, C and D have a access to two switchyards of different voitages through multiple redundant paths.

_ e. s The shutdown board ties between the Units 1 and 2 shutdown boards and the Unit 3 shutdown boards are used only to parallel diesel generator capacity. The use of these ties is controlled by Emergency Operating Instruction No. 5.(3) They have no impact on the TVA analysis. The 480 volt shutdown boards and diesel auxiliary boards each have access to two 4 kV shutdown boards for power sources. 120 V instrument and control buses derive their power from the 480 V shutdown boards. Each 4 kV shutdown board will have loss-of-voltage relaying and degraded-voltage relaying. 3.2 Existing Undervoltage Protection Each of the four 4160V class 1E shutdown boards and 4160 V start buses , l A and 1B have undegtage relays to detect loss of power. They have. a setpoint of. 2870V Should the relay logic of a shutdown board detect loss of voltace, the diesel generator associated with that bus will be started (or aT1 will be started if the loss of voltage occurs on start buses 1A or 1B). After a 3-l/2 second time delay the feed breakers to the bus will be tripped. The diesel-generator breaker automatically closes as the generator voltage and frequency become acceptable. 3.3 Modifications for Undervoltaae Protection The licensee has proposed to change the undervoltage protection scheme for Units 1 and 2. The changes include: 1. Degraded-voltage relaying system for Unit Nos.1 and 2, 4160 V shutdown boards, 2. Overvoltage alarms for Units 1 and 2, 4160 V shutdwon boards, 3. Annunciation if the 161 kV grid deteriorates below 166 kV, and 4. Removal of the start bus loss-of-voltage relaying (2), These changes are in addition to the' existing loss-of-voltage relays on the 4160 V shutdown boards. The degraded grid voltage relaying will consist of two-out-of-three relay logic for each shutdown bus. When + 20) V for 1.63 seconds the 4160 V shutdown hnard voltage is below 3920 (lie diesel generator.for the degraded voltage relaying system will start t that bus. After an additional 6.07 seconds, the offsite source breaker -is tripped and the' loads are shed in preparation for the connection of the diesel generator to the shutdown board. 4.0 Evaluation 4.1 Evaluation Criteria ~, 4.1 Ad'ecuacy of Station Electric Distribution System Voltages

.. The positions applied in determining the acceptability of the offsite voltage conditions in supplying power to the class lE equipment, are derived from the following: l. General _ design Criterion 17 (GDC 17), " Electrical Power Systems," of Appendix A " General Design Criteria for Nuclear Power Plants," l of 10 CFR 50. 2. General Design Criterion 5 (GDC 5), " Sharing of Structures, Systems, and Components," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50. l 3. General Design Criterion 13 (GDC 13), " Instrumentation and Control." of Apendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50. j 4. IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations." l ANSI C84.1-1977, '" oltage Ratings for Electric Power Systems and Equipment (60 Hz) 6. Staff positions as detailed in a letter sent to the licensee, dated August 8, 1979(16), In our generic letter of August 8,.1979, TVA was requested to review the electric ' power system at Browns Ferry Nuclear Plant. The review was I to consist of: a) Determining analytically the capacity and capability of the offsite power system and the onsite distribution system to automatically start as well as operate all required loads within their required voltage ratings in the event of 1) an anticipated transient, or 2) an accident (such as LOCA) without manual shedding of any electric loads, t l b) Datermining if there are any events or conditions which could result l in the simultaneous or, consequential loss of.both required circuits from the offsite network to the onsite electric distribution system and thus violating the requirements of GDC 17. The August 8,1979 letter included staff guidelines for performing required voltage analysis and the licensee was further required to perform a test j in order to verify the validity of the analytical results. l This safety evaluation addresses the capacity and capability of the onsite distribution system of Unit Nos. I and 2 of the Browns Ferry Nuclear Plant, in conjunction with the offsite power system,to maintain the volta 92 for the required class lE equipment within acceptable limits for the worst-case starting'and load conditions. Browns Ferry Unit No. 3 is scheduled to shutdown for its fourth refueling beginning on or.about September 25, 1981, during which time similar electrical modifications will be made on this unit as discussed herein for Units 1 and 2. TVA has not as yet submitted the changes to the Technical, Specifications that will be necarsary for I

Unit 3; besides, the Technical Specifications cannot be changed until.the modifications are actually made or the plant configuration would not be in conformance. The Unit 3 electrical modifications will be covered in a separate action. l 4.1. 2 Degraded Grid Voltace The design base criterir applied in determining the acceptability of.the system modifications to protect the safety-related equipment from a sustained degradation of the offsite grid are: 1. General Design Criterion 17 (GDC 17), " Electrical Power Systems,". of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50. . 2. IEEE Standard 279-1971, " Criteria for Protection Systems for Nuclear Pcwer Generating Stations." 3. IEEE Standard 308-1974, " Class lE Power Syster.s for Nuclear Power Generating Stations." 4. ANSI Standard C84.1-1977, " Voltage Ratings for Electrical Power Systems and Equipment (60 Hz)." + 5. Staff positions as detailed in a letter sent to the li ensee, dated June 3,1977.(9) 4.2 Adecuacy of Station Electric Distribution System Voltaaes 4 4.2.1 Analysis and Test Features TVA analyzed each offsite power source to the onsite distribution systm under maximum and minimum load conditions with the offsite power sources at maximum and minimum voltage, 500 KV and 465 KV on the 500 KV system and 166 KV and 170 KV on the 161 KV system. TVA has determined that the required minimum voltage on the 161 kV to support the Class lE equipment is 166 KV. Automatically connected capacitor banks have been added to assist in providing this voltage and annunciators will alarm in the control room if the voltage on this system (a third source'of offsite power) deteriorates to 166 KV. The analysis included the effects on the Class 1E equipment with all LOCA loads on one unit, shutdown loads on the other unit and simultaneous start of a residual heat removal'purrp and cor.: spray pump which produced the worst case loading on the shutdown boards under minimum grid voltage conditions. Table 1 shows the projected worst case class lE equipment terminal voltages with. the 500 kV grid as. source. Table 2 shows the projected worst case class lE equipment terminal voltages with the 161 kV grid as source. It has been established that the 4160 volt and 480 volt emergency loads will operate within allowable limits when supplied from the 500 KV grid. When the third source of offsite power. (161 KV grid) is sypplying power this voltage must be maintained above 166 KV. This is accomplished by the use of capacitor bar.ks on the common station service transformer. Alarms are installed which annunciate in the control room should this source fall to 166 KV. The use of these capacitor banks could cause an overvoltage

a e O su a QJ , ( condition.under the minimum loading condikakes. in the control room if the i n TVA has L provided an overvoltage alarm that annunc l. voltage on the 4160 volt shutdewn board exceeds 110%. This overvoltage condition is not considered significant since the alarm will allow . operator action to reduce this overvoltage and any significant loading of equipment on the buses would additionally reduce the voltage to within l safe operating limits. TVA has committed to test and to verify the i results of this analysis. These teste are to be completed by March 1983, i TVA has not outlined the scope of these tests. As a minimum NRC l requires the following criteria,be met: i Loading the station distribution buses, including all Class lE buses a. down to the 120/208 V level, to at least 30%; b. Recording the existing grid and Class lE bus voltages and bus loading l duwn to the 120/208 volt 19. vel at steady state conditions and during starting of both a large Class lE and non-Class 1E motor (not concur-rently). NOTE: To minimize the number of instrumented locations (recorders) l du' ring the motor starting transient tests, the bus voltages and. loading need only be recorded on that string of buses which l previously showed the lowest analyzed VM tages. Using the analytical techniques and assumptions 'of the previous c. l voltage analyses, and the measured existing grid voltage and bus l loading ccaditions recorded during conduct of test, calculate a new ' set of voltages for all Class 1E buses down to the 120/208 vol t. l evel. l d. Compare the analytically derived voltage values again.st the test resul ts. With good correlation between the analytical and the test results, e. the test verification requirements will be met. In general, the. test results should not be more than 3". lower than the analytical results; however, the difference between the two when subtracted from the voltage levels determined in the original analysis should never be less than the Class lE equipment rated voltages. 4.2.2 Desien Chenops As a result of the initial voltage analysis TVA has proposed the following l* design changes: l 1. On-load tap changer for unit station service transformer 1B and 2B. 2. Unit generator breakers for Uni +s 1 and 2. 3. The automatic alternate feed for the Class 1E 120V instrument and control buses is removed. A manual alterntte source connection will still be available. 4. Replacement of the 480/208/120 V instrument and control transformers with self regulating and larger capacity transformers. a w

pp - w 8_- i

5. ' Annunciation if the 4 KV. shutdown boards experience an overvoltage.

condition.. -The installation'of the generator circuit breakers for' units 1 and 2 changes the normal and alternate supply to the Class 10 distribution system. Operation of the generator circuit breakers will allow backfeeding from the 500 KV switi:hyard as the immediate access source of-offsite power to the onsite distribution system. The breakers are arrangeri to open automatically on a unit trip and maximum fault current. 'At the present time no standards exist, for testing of generator circ'uit . breakers of this type (isolated phase bus construction) and ~ size (over 5000 amperes current

• rating and 80 Ks interrupting rating at generator voltages). The existing. ANSI /IEEE Standards are applicable to high voltage switchyard breakers and meditm and low voltage breakers of the

. type used in plant. The test procedures described in ANSI C37.09-1971 wqre used by TVA to develop testing requirements for the generator circuit' breakers. This testing was performed by KEMA (The Netherlands) and witnessed by TVA. Breakers of this same type and manufacturer (with a higher rating) have been previously evaluated by NRC and its consultant (Union Ca', bide) and approved for installation in McGuire Nuclear Plant. TVA has performed :c ' -ircuit studies which show the maximum fault current anticipated for breue, aperation is 145 KA. Based on these studies TVA specified a rating of 165 KA for the generator breakers. The results of the~ tests (Table 3) demonstrates that the generator circuit breakers will satisfactorily perform their intended function of isolating the generator from the 500 KV. grid and allow the grid to backfeed through the main and Unit, station tervice transformer as an immedia.te source of, ~ offsite power on a unit trip. The generator c'rcuit breakers successfully passed all testing specified by TVA. As an additional precaution against out-of-phase switching TVA has installed a out-of-sync relay which supervises ge' rye'rator breaker closure by the operator. In the event that a generator breaker should fail to operate, additional sources Of offsite power are available from the 500 KV and 161 KV grids. In the unlikely event of a failure of more than two of the single phase stepup transformers, which could require use of a lower impedance temporary transformer, TVA has decided to upgrade the generator circuit breakers to a 200 KA rating. These modifications will be performed during the refueling cutage of unit 2. The additional testing to verify this higher rating will be performed on a similar unit' at the KEMA test facility and completed prior to installation of the modifications to the installed breakers. Preoper-ational tests will be performed on these breakers prior to placing them in operation. Periodic testing and maintenance of the breakers is planned for each plant refueling outage. TVA states that as experience is gained with these breakers, the testing and maintenance will be readjusted accordingly. Based on the above we find the generator breakers acceptable for use in Units 1-and 2. 4.2.3 Summary We have reviewed the design of the electrical modifications currently being implemented at Browns Ferry Unit Nos.1 ana 2 and the analyses submitted - by TVA. We have determined that upon satisfactory completion of the verification tests (which TVA has committed to perform and which are' discussed in Section 4.2.2, above) that the generic issue regarding the 1 g h 9 ,,2 r-- , -,. + -. - - -. -

.g-adequacy of station electric distribution system voltages is acceptably resolved for Browns Ferry. Units 1 and 3..Specifically, we have found that: (1) TVA has provided voltage analysis to demonstrate that the Class lE equipment voltages remain within acceptable operating limits for the postulated worst conoitions. Voltages within the operating. limits of the class 1E equipment are supplied for all projected combinations of plant load and normal offsite power grid conditions, including an accident in one unit and the safe shutdgwn of the other units. l (2) TVA has determined that no potential for either a simultaneous or consequential loss of.all offsite. power sources exists. (3)' TVA's reaffirmation of compliance with'GDC 17'requiiements is ~ acceptable. (4) Loss of offsite power to the Class 1E Juses, due to spurious operation of the voltage relays, will not occur with the 500 KV grid within its expected operating limits. Spur ous separation with the 161 KV grid as tlie power source will not o< cur as long as this grid is maintained a bg y.e. l.66.1$y. I. (5) The tests proposed by TVA, provided the methods outlined in Section 4.4.2 of this safety evaluation are incorpori ted, will verify the analysis accuracy. 4.3 Decraded Grid Protection 4. '3.1 Electrical modifications and chances to Technical Specifications l The fol'.owing electrical systems design modifications and Technical i Specification changes were proposed by TVA. l a. Installation of a second level of undervoltage relays on each of the l 4160 volt shutdown boards for Units 1 and 2. The second level degraded grid voltage relaying will consist of a two-o t-of-three logic l - for each shutdown board. When the 4160 veit shutdown board voltaae is belov' 3920 (120) volts for 1,63 seconds, the relays will start the diesel generator for the effected board. After an additional 6.07 i seconds, the offsite source breaker is tripped allowing the diesel generator to supply the effected shutdown board. b. Installation of overvoltage alarm annunciated in the control room for the Unit 1 and 2 4160 volt shutdown boards. c. Annunciation in the control room when the 161 kv grid (a third source of offsite power), normally operated between 160 and 170 kv, deteriorates below 166 kv. This is the minimum voltage required by this source to supply accident loads on one unit and safe shutdowr. loads on the second unit. This alarm will allow TVA to take action and maintain the voltage above 166 kv.

d. The start bus loss-of-voltage relaying which provides no safety functions after these modifications have been removed. Additions and changes to the plant Technical Specifications e. including the surveillance requirements, allowable limits for the setpoint and time delay, and limiting conditions for operatfort have been provided by the licensee. An analysis to substantiate limiting conditions for operation and minimum and maximum setpoint limits were included as part of the modification proposal. The changes and additions to Technical Specifications have been reviewed by the NRC and found acceptable with the exception of the periodic (10' month) testing requirements for Unit 2 onsite power syste.n. These tests are used to demonstrate the full-functional system operability and independence of the onsite power system. The licensee's present proposal on how this testing will be performed is under discussion with TVA and will be resolved prior to the actual testing that will be required during Unit 2 refueling outage. Browns Ferry Unit 2 is currently scheduled to shutdown for its fourth refueling beginning on or about March 26,1982 with a projected restart date of mid August 1982. Since the test program and schedule for testing the Unit i diesel generators meets all staff positions, there is reasonable expectation that a satisfactory schedule for testing the Unit 2 diesel generators can be resolved during the next year. One of the NRC staff positions in our generic letter of June 3, 1977(9) is that tests to demonstrate the full-functional operability and independence of the onsite power sources are to be performed at least once per i8 months during shutdown. The 'terts are to simulate interruption and subsequent reconnection of onsite power sources. These tests verify the proper operation of the load-shed system, the load-shed bypass when the emergency diesel generators are supplying power to their respective buses, and that there is no adverse interaction between the onsite and offsite p'ower sources. The proposed technical specifications comply with the requirement to test by simulated loss of offsite power in conjunction with a safety-injection signal. However, the Unit 2 technical specifications differ from the Unit 1 technical.sm,ecificatio31s in that they share diesel generation. The' technical specifications aHow the Unit i diesel generator loading test to serve or Unit 2. There is at present no requir'ement for periodic verification that' tne Unit"2' safety related loads can be sequenced onto and maintained on the diesel generators. 4.3.2 Summary We have reviewed the design and analysis of the electrical modifications currently being installed at Browns Ferry Units 1 and ? and have detemined that, subject to resolution of a verification test schedule for Unit 2, that the generic issue rega-ding degraded grid protection for class lE power systems is satirfactorily resolved for Units 1 and 2. Specifically, we have determined that: (1) The proposed degrad i grid modification will protect the Class lE equipment and syste ns from sustained degraded voltage of the offsite power source. t

, (2) The proposed Technical Specification changes whiae acceptable for Unit I are not fully acceptable for Unit 2. The one unacceptable test is presently being discussed with the licensee and will bc resolved prior to Ur.it 2 refueling shutdown. (3) The existing load shedding circuit will block load shedding once the diesel generators are supplying the safety loads. The load shedding feature will be reinstated if.the diesel generator breaker should trip. 5.0 Environmtatal Considerations We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendments involve an action which is insignifican; from the standpoint of environmental impact and pursuant to 10 CFR 51.5 (d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepered.in connection with the issuance of the amendments. 6.0 Conclusion We have concluded, cased on the consiaeration discussed above, that: (1) because the amendments' do not involve a signifinant increase in the probability or consequences of accidents prev ously considered and do not involve a significant Jecrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable ast rance that the health and safety of the public will not be endangered by operation in the prpresed manner, and (3) such activities will be conducted in compliance with the Commission's regulatior.s and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public. Dated: September 3,1981 9 e a 5

he - m REFERENCES 1 - Letter, L. M. Mills, TVA, to Harold R. Denton, NRC, dated April 9,1981. 2. Letter, L. M. Mills, TVA, to Harold R. Denton, NP.C, dated' June 8,1981.

3. ' Letter, L. M. Mills, TVA, to Harold R. Denton, NRC, dated July 2,1981.

4 Letter, L. M. Mills, TVA, to Harold R. Denton, NRC, dated July 31, 1981. 5. Letter, L. M. Mills, TVA, to Harold R. Denton, NRC, dated August 17, 1981. 6. Letter, A. Schwencer, NRC, to Godwin Williams, TVA dated August 12, 1976. 7. Letter, J. E. Gilleland, TVA to Al Schwencer, NRC, dated September 15, 1976. 8. Letter, A. Schwencer, NRC, to Godwin Williams, TVA, dated June 3,1977. 9. Letter, J: E. Gilleland, TVA, to A Schwencer, NRC, dated July 22, 1977.- 10. Letter, J. E. Gilleland, TVA, to Edson G. Case, NRC, dated May 2,1978. 11. Letter, R. H. Davidson, TVA, to Edson G. Case, NRC, dated May 17, 1978. 12. Letter, George Lear, NRC, to N. B. Hughes, TVA, dated May 31, 1978. 13. Amendment Nos. 39, 37 and 13 to Facility Licenses Nos. DPR-33, DPR-52 and DPR-68 for the Browns Ferry Nuclear Plant, Unit Nos.1, 2 and 3, dated June 23,1978. 14 Letter, J. E. Gilleland, TVA, to George Lear, NRC, dated May 12, 1978 15. Generic Letter to "All Power Reactor Licensees (except Humboldt Bay) RE: Adequacy of Station Eltetric Distribution Voltages" dated August 8,1979. 16. Letter, L.- M. Mills, TVA, to W. P. Gammill, NRC dated September 4,1979 ~

a I l-TABLE 1. CLASS 1E EQUIPMENT VOLTAGE RATINGS At.4D ANALYZED WOPST CASE TERMINAL VOLTAGES--BROWNS FERRY UNIT NOS. 1 AND 2 (% of nominal voltage) 500 kV GRID SOURCE f i Maximum Minimum Analyzed Ecutoment Condition Rated. Analyzed Rated Steady State Transient 94.3 85 4 KV Motors Start Operate 110 105.5 90 103.5 85 89.4 460 V Motors Start Op'erate 110 111.la 90 96.5 l 85 88.6 4S0 V Starters Pickup 88.6 60 Dropout j Operate 110 106.5 90 94.3 Other Equipmentb l l . 111.1% is based on no station loads. With any load connected, some a. transformer and feeder cable voltage drop would be present. TVA indicates that the minimum feeder voltage drop is 1%.4 Therefore, with the l connection of a 460 V motor, it would not have a voltage in excess of 110% l of its rated value. b. 120 V instrumentation and control circuits will, after the proposed modification is complete, have self-regulating transformers to maintain the l bus voltage at 120 V +1% with an input voltage of 480 V +10%-20%. As seen j above for the 4S0 V starters, the 480 V bus voltage is within these ratings. I l l l l 9 4 S

A 4 4 ok 4 -,,A- ,-L.- n f I I l l. TABLE 2. CLASS lE EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE l TERMINAL VOLTAGES--BROWNS FERRY UNIT N05. 1 AND 2 l,. (% of. nominal voltage) 161 kV GRID SCURCE l-l Maximum Minimum l 5teady State Transient Analyted Ecutoment Condition Rated Analyzed Rated l 4 kV Motcrs Start 85 88.7 l Operate 110 112.6a go 97,7 89.4b 460 V Motors Start 85 Operate 110 115.9 90 96.5b 88.6b 430 V Starters Pickup 85 l Dropout 88.6b 60 i Operate 110 111.lc 90 94.3b l Other Equipmentd i l .This is based en no statien loads, i.e.--no equipment is-connected. a. The observed voltage would be lower as loads are connected. l. b. This is based on the lower limit of the degraded voltage relays. c. 111.1% is based on no station loads. With minimal stat' ion shutdown loads, the starter rating would not be exceeded. d. 120 V instrumentation and control circuits will, after the proposed modification is complete, have self-regulating transformers to maintain the bus voltage at 120 V +1% with an input voltage of 480 V +10%-20%. As seen f or the 480 V starters, the 480 V bus voltage can exceed this rating. How-ever, as the 480 V bus voltage reaches 115.9% the 120 V voltage we'uld approach 6% higher than the bus rating. This would not exceed the equipment ratings when station loads are taken into account. l' 9 s rms~ v

s. TABLE 3.. BROWS FERRY SPECIFIED RATINGS AND TESTS FOR GENERATOR BREAKERS Parameter Rating ' Tests 1. Voltage kV-rms 24 ' Dielectric withstand 60-kV-r:s, 1 =inute, parsed (routine test). 2. Lcad current 36 Heat run 23C Rpt No. (continuous) kA HAQ-2611E (en Bellefonte generator contract 72C2-85500), 40.8 kA 50 H: 38.51 kA 60 H:, breaker within acceptable te:perature rise. 3 Insulation level 150 kV BIL Withstood 1.2 x 50 ,,,, _=_icroseconds 195 kV crest, positive and -~ ~ ~ negative waves,.BBC test - .m 1-352780-041-900 c. (3e11efonte). ~ 4 Interrupting li5 -r capacity, kA-f=s A. Sy==etrical 176 kA 9 15.5 kV. (See Raccoon Mot atain DEMA test No. 2366-74 Passed. 230 kA 9 15.5 kV. (See B. Asy= metrical KEMA 2366-74). Passed. 5 Cicse and latch, tt6 558 kA f 20.5 kV.- (See kA-peak KEMA test report 624-80). Passed. 6. Short time, kA. 3 sec e 4 seconds e 46r kA. -(See 165 kA KEMA 2366-74). Passed. T. - Maximum rate of Not specified 3 kV/ microseconds. (See rise of recovery KEMA 2366-74).. Adequate. voltage ) 29.5 kV, 29.5 kV f 98 kA-8. Out-of-phase 90 kA asymmetrical. (See KEMA_, -2366-T4)..',? ass ed.._.; - .. ~.

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