ML20085G259

Proposed Tech Specs,Revising Surveillance Requirement 4.8.1.1.2.d.3 Re Diesel Generator Load Rejection Overshoot Limits

ML20085G259
Person / Time
Site:	Sequoyah
Issue date:	10/11/1991
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20085G253	List: ML20085G251 ML20085G259
References
NUDOCS 9110240210
Download: ML20085G259 (9)

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. . i 4-i ENCLOSURE 1 1R0 POSED TECHNICAL SPECITICATION CilANCE -f SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2  ;

DOCKET NOS. 50-327 AND $0-328 3 (TVA-SQN-TS-91-17)  !

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_ LIST OF AFFECTED PAGES.

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ELECTRICAL POWER SYSTEMS SURVEILLANCE REQUIREMENTS (Continued)

d. At least once per 18 months during shutdown by:

1. Subjecting the diesel to an inspeution in accordance with procedures prepared in conjunction with its manufacturer's recommendations fer this class of standby service,

2. Verifying the generator capability to reject a load of greater then or equal to 600 kw while maintaining voltage within i gio3 10 percent of the initial pretest voltage and frequency at 60 + 1.2 Hz. At no time sna11 the transient voltage exceed 8276V.

3. Verifying the generator capability to reject a load of 4400 kw ut tripp5ng. The generator voltage shall lR68 eed

\20 -H4- ercent of the initial pretest voltage o wh'chever 31o3 ess during and following the load rejecti n

4. Simulating a loss 01 offsite power by itself, and:

a) Verifying de-energi:ation of the -hutdown boards and load shedding from the shutdown boards, b) Verifying the diesel starts on the tuto-start signal, energizes the shutdown brards with permanently connected loads within 10 seconds, energizes the auto-connected shutdown loads through the load sequencers and operates -

) for greater than or equal to 5 minutes while its generator "---

is loaded with the shutdown loads. After energization, the steady state voltage and frequency of the shutdown boards shall be maintained at 6900 1 690 volts and 60 1 1.2 Hz during this test.

5. Verifying that on a ESF actuation test signal (without loss of of*:ite power) the diesel generator starts on the auto-start signal and operates on standby for greater than or equal to 5 minutes. Tha generator voltage and-frequency shall be 6900 1 690 volts and 60 1 1.2 Hz within 10 seconds after the auto-start signal; the steady state generator voltage and fre-quency shall be mM ntained within these limits during this test. R$3

6. Simulating a loss of offsite pow 2r in conjunction with an ESF actuation test signal, and a) Verifying de-energization of the shutdown boards and load shedding from the shutdown boards.

"I O b) Verifying the diesel starts on the auto-start signal, energizes the shutdown boards with permanently ccnnected loads within 10 seconds, energizes the auto-connected emergency (accident) loads through the lodd sequencers and operates for greater than or equel to 5 minutes while its generator is loaded with the emergency loads. After energization, the steady state voltage and frequency of the emergency busses shall be maintained at 6900 1 690 volts ('

and 60 1 1,2 Hz during this test. R141 SEQUOYAH - UNIT 1 3/4 8-4 Amendment No. 49, 64, 114, 137 April 27, 1990

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, ELECTRICAL POWiR SYSTEMS'  !

SURVEILLANCE REQUIREMLA S (Continued)  ;

- d. At least once per 18 months during shutdown by: l

1. ,$ubjecting the diesel to an inspection in accordance with _;

.procedores prepared in conjunction with its manufacturer's '

recomiaendations for this class of standby service, ,

2. Verifying the generator capability to reject a load of greater than or equal to 600 kw while maintaining voltage at within i R88 i p 10 percent of the initial pretest voltage and frequency at -!

K 60 + 1.2 Hz. At no time shall the transient voltage exceed 8273V.

b 3. Verifying the generator capability to reject a load of 4400 kw R$6 f

t out tripping. The generator voltage shal need '

120 -H4 ercent of the initial pretest voltage 00 " wh chever R88 ess during and following the. load rejec o .N

4. Simulating a-loss of offsite power by itself, en : )

a) Verifying de-energization of the shutdown boards and load  !

shedding from the shutdown boards.

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b) Verifying the diesel starts on the auto-start signal, energi7es the shutdown boards with permanently connected ,

loads within 10 seconds, energizes the auto-connected shutdown loads through the load sequencers and operates  !

for greater than or equal to 5 miautes while its generator i

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[. is loaded with the shutdown loads. After energization, the steady. state voltage and frequency of the shutdown >

boards shall be maintained at 6900 t 690 volts and 60_i 1.2 Hz during this test.  ;

A 5._ - Verifying that on a ESF ac. > ' n test signal, without loss of-offsite power, the diesel v tor. starts on the auto-start r signal:and operates on stancg for greater than or equal to 5

. minutes. The generator voltage and frequency shall be

'6900 t 690 volts'and 60 1 1.2 Hz within 10 seconds after the i

, auto-start signal;_the steady state generator voltage aad frequency shall be maintained within these limits during this R41 test.  :

-6. Simulating a less of offsite power in-conjunction with an ESF actuation test signal, and a) Verifying de energization of the shutdown boards and load l shedding from the shutdown boards, s -b). Verifying the diesel starts on the auto-start signal, j energizes the shutdown: boards with permanently connected loads'within-10 seconds, energizes the auto-connected emergency (accident)-loads through-the load sequencers and t aperates for greater than or equal to 5 minutes while its generator is loaded with the emergency loads. After

energization, the steady state voltage and frequency-of  :

, the emergency busses shall be maintained at 6900 t 690 volts  !

and 6011.2 Hz during this test.

L SEQUOYAH - UNIT 2 3/4 8-4 gmegmpp,t b90 4

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ENCLOSURE 2 FROPOSED T1.CilNICAL SPECIFl(. ATION CllANCE SEQUOYAll NUCLEAR PLANT LNITS 1 AND 2 DOCKET N05, 50-327 AND 50-32a (TVA-SQN-TS-91-17)

DESCRIPTION AND JUSTIFICATION FOR REVISION TO VOLTAGE OVERSil00T LIMITS FOR DIESEL GENERATOR LOAD REJECTION TEST

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- - FNCLOS1;RE 2 l

l Description of Change TVA proposes to modify the Sequoyah Nuclear Plant (SQN) Units 1 anil 2 technical' specifications (TSs) to revise Surveillance Requirement , (SR) 4.8.1.1.2.d.3 f rom the 114 percent of inicial pretest voltage limit for t voltage overshoot- on a total load rejection to 120 percent. The voltage limit of 8.276 volts (V) will also be increased to 8.712 V to correspond  ;

with the increase to 120 percent described above. j Reason for Chang <

On October 7. 1991, the testing of the 1A-A diesel generator (D/G) for a I full load rejection resulted in.approxim tely 115 percent voltage overshoot [

from the initial pretest voltage. On October 9, 1991. t' same test for the 3 IB-B D/G resulted in approximately 119 percent voltage ourshoot. These

• results do not comply with the TS 4.8.1.1.2.d.'s requirement to not-exceed 114 percent voltage overshoot during a full load rejection. TVA requested ,

and was granted a waiver of compliance by Office of Nuclear Reacter i Regulations.on October 10, 1991. The reason for requesting emergency

- processing of this TS change is to allow continued full power operation of .

Unit 2. to minimir.e the additional D/G SR testing and associated unnecessary  !

wear and teat because of the inoperability of these D/Gs and to maintain  !

- critical' path work activities for the Unit 1 Cycle 5 refueling outage after {

- expiration of the waiver.- '

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Justification for Change  !

TVA proci:.ssed a TS change request in January 1989 to modify SR 4.8.1.1.2.d.3 i to the; acceptance voltage values listed above. The voltage' limit of 8.276 V 1 was based on-114 percent of the expected maximum plant operating voltage of-7,260 V.- The 114 percent of pretest voltage value was based on past test

.results that indicated approximately 112 percent voltage overshoot and was not-based on any criteria associated with equipment damage. -

Since the approval and implementation of amendrnents -f or Units 1 and .2 that .

incorporated these values. modifications have been implemented to the i

transient voltage response of the D/G. The modifications have been to the i generator exciter control ~ system that altered the excitation current transformer (CT) tap settings to provide a' boost of the: field current for a '

given D/G-kilovoltampere (kVA) load and addition-of the voltage overshoot reduction device (VORD) that shunts the iiuid current-to zero if-the transient. overshoot during the D/G loading sequence exceeds 103 percent of=

- nominal duric ischronous mode of operation.' -The VORD is not active in the D/G circuit during performance of the load rejection test that is' performed'

'in the droop mode. This_ is because the shutdown board's normal-voltage' '

range during-plant operation exceeds the 103 percent operating setpoint of the VORD.

In addition, procedural changes have bee- intly incorporated that require generator loading to-the design rating ( ,400 kilowatt and 5.000 kVN.

This change in testing was-incorporated o a result of industry operating enperience information (NRC Information Notice 91-13) and is more eon-e-,- ,,m-n,-.,.-_ wee.,vw--,..m.-.,,.-+,e..-swwr-rwwcr-, --.,-w-,w-er---m--,.-ww-m- w e - ---v,-w-w m ,-r w -e-e - c= r ir e ,- *-- t y--r t e :we- p g y yv ><vve-

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2 conservative than previous test conditicns. This change results in au increase in the internal generator voltage setpotut, which is required to ,

overexcite the generator to be able to obtain a rated kilovoltampere reactive (kVAR) output of approximately 2,375. This change also increases  :

generator field current. Both the higher internal voltage and the l

additional field current tend to create a higher voltage overshoot when the  :

rated load is suddenly removed.  !

i An additional factor that contributed to identification of the overshoot was i tbc use of high-speed visicorder data to determine voltage overshoot.

Previously, voltage overshoot had typict.11y been determined from installed ,

panel gauge data. This panel instrumentation had significantly reduced capability for identifying high-speed, snort-duration transients.

The-described conditions that identified voltage overshoots in excess of TS limits and previously measured values are believed to have been caused by '

the combination of the revised procedural requirements to test at rated '

generator load (resulting f rem review of IEN 91-13), the CT modification, I and the.use of more accurate instrumentation capable of identifying f short-duration transients. The combined effect of these changes increases the voltage overshoot of the D/G during load rejections. The inoividual i contributions of each change are not known and would require additional D/G ,

testing that is not recommended for reliability considerations. However, it is considered that the chaages in test kVA loading are the driving .;

contributor to this condition. The-individual changes, as well as the ,

combined effect of these changes, were not applicable or were not expected I at the time of the TS change requested in 1969. Additionally, the effect of  !

these changes could not be quantified at the time of initial implementation -

and-therefore was not identified until performance of the subject testing.

There is negligible safety significance associated with the subject voltage overshoot levels. The test rieficiencies were of very brief durat.lons (13 and 23 cycles for 1A-A and 1B-B respectively) and of small magnitude relative to equipment-consideratiers. The brief transient overvoltages (8,250 and 8,a20 V forLIA-A and 1B-B respectively) would not overstrcss the

, generators'. insulation system. Insulation-life is inversely proportional to [

voltage stress, but the dure. tion of these transients le so small that the effert'on insulation life would be negligible.- The generator manufacturer I has' determined that an acceptance criteria ~of 8,712 V f7r a maximun duration ,

of.30 cycles would not significantly reduce the qualified life of the

-generator. The D/G vendar has determined that the engine and/or' generator controls.would not experience detrimental effects for transient voltages up

.to 9,000 V. Accordin31y, it is considered that overshoot limits in excess of those.provided in either current SQN or standard TSs are technically adequate to prevent equipment damage or degradation following a full-load rejection. -In summary, while the_ testing results exceed the SQN TS overshoot value, the' subject voltage levels have not and.will not adversely affect D/G equipment or capability to perform the intended function.

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e Environmental impact Evaluation

The proposed change request involves testing requirements for D/Gs .nd will not affect the functions or operation of any equipment such that an unreviewed environmental question would be involved because operation of SQN Unita 1 and 2 in accordance with this change would not!

. 1. Result in a significant increase in any adverse environmental impact

,, previously" evaluated in the Final Environmental Statement (FES) as modified by the Staff's testimony to the Atomic Safety and Licensing Board,-supplements to the FES, environmental impact appraisals, or

- decisions-of the Atomic Safety and Licensing Board.

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- 2.. Result-in a significant change in effluents or power levels.

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3. Result in matters not previously reviewed in the licenslag basis for SQN tuat may have a significant environmental impact.

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Enclosure 3 l

PROPOSED TECl!NICAf, SPECIFICATION CilANGE ,

SEQUOYAll NUC1. EAR PLANT UNITS. i- ANL) 2  ;

DOCKET NOS. 50-327 AND 50-3P.8  ;

i (TVA-SQN-T3-91-17) j DETERMINATION OF-NO SIGNIFICANT ilAZARDS C0FSID" RATION j f

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Significant Hazards Evaluation TVA has evaluated the proposed techniesi spectrication (TS) change and has  ;

-determined that it does not represent a significant hazards consideration  ;

based on criteria establisned in 10 CFR 50.92(c). Operation of Sequoyah  !

Nuclear. Plant-(SQN) in accordance with the proposed amendment will nots  :

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1.  : Involve a significant increase in the probability or consequences of an' i accident.previously evaluated. i This-request proposen a TS change for the Surveillance Requirement {

(SR) 4.8.1.1.2.d.3 to allow a voltage overshoot of 120 percent of pratest voltage orc 8.712 volts, whichever is less. .It has been determined that these increased values would not result in damnge to the ,

diesel generator.(D/G) and will continue to ensurs operability as _

discussed in the_ previous justifications. The revised limits will ,

-ensure that safety-related functions are adequately veriflod.  ;

Therefore the D/Gs will continue to be verified to meet safety- '!

. requirements and_the subject changes will not increase the consequences  !

ofran accident. In addition. the D/Gs are not postulated _to be the l source ofiany design basis accident and therefore cannot-increase-the i probability for an accident. j i

! 2'- - Create the possibility of a, new or dif ferent kind of accident f rom any- i

!previously analyzed.-  ;

.This request only provides an increase in the-allowable voltage ,

overshoot on a total-D/GLload rejection. . This change.does not' create

.any new type of; accident because alteration of test requirements for tSe-  !

-D/G or any other_D/G test or operation cannot create an accident. The- [

.D/Gs only_ provide accident mitigation functions. i t

3.- Involve a significant reduction in a margin of safety.

f The revised voltage values will not result in damage to any D/G ,,

components and therefore=the D/G safety functions will be maintained.

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.Since the D/Gs will continue to provide full accident mitigation- t capabilities a margin of. safety will not be reduced.-

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