ML20008F028

Safety Evaluation Supporting Amend 40 to License DPR-66

ML20008F028
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Site:	Beaver Valley
Issue date:	03/03/1981
From:	Office of Nuclear Reactor Regulation
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UNITED STATES

[

"k NUCLEAR REGULATORY COMMISSION y.,

g WASHINGTON, D. C. 20555 bq \\ w /

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 40 TO FACILITY OPEMTING LICENSE NO. DPR-66 DUQUESNE LIGHT COMPANY OHIO EDISON COMPANY PENNSYLVANIA POWER COMPANY BEAVER VALLEY POWER STATION, UNIT NO.1 DOCKET NO. 50-334 Introduction and Summary The criteria and staff positions pertaining to degraded grid voltage protection were transmitted to Duquesne Light Company (DLC) by NRC generic letter dated June 3, 1977. In response to this, by letters dated October 15,1979, May 14, 1980 and July 24, 1980, the licensee proposed certain design modifications and changes to the Technical Specifications. A detailed review and techni-cal evaluation of these proposed modifications and changes to the technical specifications was performed by EG&G, under contract to the NRC, and with general supervision by NRC staff. This work is reported by EG&G in a draft report, "Tachnical Evaluation Report on Degraded Grid Voltage Protection for Class 1E Power Systems" ( Attachment 1). We have reviewed this technical eval-uation report and concur in its conclusion that the proposed design modifica-tions and Technical Specification changes are acceptable.

Proposed Changes and Evaluation Criteria The following design modifications and Technical Specification changes were proposed by DLC.

a.

Installation of second level undervoltage relays, two on each 4160 V Class lE bus and two on the secondary side of one of the two, parallel 4160/480 V load center transformers with a drop out setting at approxi-mately 90% of nominal bus voltage and a maximum of 95 second time delay.

These relays on each of the two voltage levels are arranged in a two-out-of-two logic scheme. A similar protective scheme is provided on the redundant train. The existing loss of voltage relays setpoint is changed fron 80% to 75% of nominal bus voltage.

b.

Installation of circuitry to block the undervoltage trip load shedding feature on the 4160 V Class lE buses when the diesel generators are supplying these buses, and automatically reinstating this feature when the diesel generator breakers are tripped, s

8103120 09

c.

Addition of trip setpoint, limiting conditions for operation and surveillance requirements in the Technical Specifications associated with the design modifications cited above.

The criteria used by EG&G in its technical evaluation of the above proposed changes include GDC-17. " Electric Power Systems," of Appendix A to 10 CFR 50; IEEE Standard 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations," IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations," and the staff positions defined in NRC generic letter to DLC dated June 3,1977.

Conclusions We have reviewed the EG&G Technical Evaluation Report and concur in its findings that (1) the proposed modifications will protect the Class 1E equipment and systems from a sustained degraded voltage of the offsite power source, and (2) the proposed changes to the Technical Specifications meet the criteria for periodic testing of protection systems and equipment.

Therefore, we conclude that DLC's proposed design modifications and changes to the Technical Specifications are acceptable.

Environrental Consideration.

We have determined that the amendment does not authorize a change in affluent types or total amounts nor an increase in pcwer level and will not result in any significant environmental impact. Having made this deter-nination, we have further concluded that the amendment involves an action which is insignificant frcri the standpoint of envircnnental impact and, pursuant to 10 CFR s51.5(d)(4), that an environmental impact statement or negative declaration and environ-rental impact appraisal need not be prepared in connection with the issuance of this amendment.

Ccnclusion We have concluded, based on the considerations discussed above, that:

(1) because the amendment dces not involve a significant increase in the pecbability or censequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in conpliance with the Commission's regulations and the issuance of this amendment will not be inimical to the cccmon defense and security or to the health and safety of the public.

Date: March 3,1981

TICHNICAL EVALUA!!CN RI? ORT DECRACE3 GRID PROTECTICN FCR CLASS lE PC'El SYSTEMS 3~. AVER VALLEY PC'4R STATICN, "N!! NO. I

1.0 INTRODUCTION

On ' June 3,1977, :he NRC reques:ed :ne Duquensne Ligh: Co=pany (DLC)

o assess :he suscep ihili:y of the safe:y-rela:ed ele::ri:a1 equipment a:

the 3eaver Valley Power 3:ation, Uni: No. 1 (3V?S-1) :s a sustained voltage degrada: ion of :ne offsi:e sour:e and in: era:: ion of :he offsi:e and o=si:e e=er en:, p2wer sys::=s.1 The le::e :en:ained :hree posi: ions vi:~.:

wnien :he curren: design of :he plan: was :s be conpared. Af:e co= paring

ne curren: design to the s:aff positions, DLC was required to ei:her pro-pose =edifica: ions to sa:isfy :he positions and ::iteria or furnish an analysis to substan:ia:e tha: the existing f acili:y design has equivale=:

apas:5.:ies.

3y la::e da:ed 0::ober 15,1979, 3LC proposed :er:ain design ::difi-

a: ions an' --- :- =' o furnishing techni:a1 spe:ifi..a: ion changes i= the future to sa:isfv. :he ::i:eria an.d staff oosi:i:ns.

Sv. le::ers da:ed May 11, 1930g, and July 21, 1980*, DLC did sub=i: te:hni:a1 spe:ifi:a-

ion changes :s :o: ply with :he s:af f posi: ions. The nodifica: ions consis:

of :he ins:alla: ion of a second-level undervol: age pro:e : ion sys:e= for

he class IE equip =en: and blocking of :he load-shedding fea:ure when the diesel genera:or is supplying power to :ne e=ergen:y buses. The NRC required :ha: the se: point, surveillance require =en:s, tes: require =en:s.

and allewaole li=i:s were :o be in:luded by OLC in the plan: :e:hni:a; spe:i;t:a: ions.

2.0 DESIGN 3ASE CRITERIA The design base ::i: aria :ha: vere applied in deter =ining :he ac:ep:-

abili:7 of the sys:e= = difica: ions :o prote:: :he safety-related equipmen:

' fro = a sustained degrada: ion of :he offsi:e grid are-1.

General Design Cri:erion 17.(COC 17), " Ele : ical Power 3ys:e=s," of Appendix A, " General Design Cri:eria for Nuclea: Power Plants," of 10 CFR 503 2.

IIII S:andard 279-1971, " Class II Power Sys:e=s for Nuclea Power Genera:ing Sta:ic,ns"6 1.

EEE S

andard 303-1971, " Class IE Sower Sys:e=s for Nu:*ea Power Genera:ing Sta: ions"'

5:sff posi: ions as de: ailed in a let:e sen: :o :he li:ensee, da:ed June 3, 19771 5.

'ANS: S:andard 084.1-1977, " Voltage Ra:ings for Electri-cal ?:ver Sys: ens and Equip =en: (50 Hz)."3 1.

3.0 EVALUATION This section provides; in Subsec: ion 3.1, a brief description of the existing undervol: age pro:ecti:n at the 3VPS-1: in Subsee:icn 3.2, a description of the licensee's oposed =odifications for the second-level undervol: age protec: ion; and :.. Subsection 3.3, a discussion of hev :he proposad =cdifications =ee: :he design base criteria.

3.1 Existing Unde: voltage ? otec: ion. The presen: scheme at SVPS-1 consists of six undervol: age (UV) relays en each load group. (The sta:ica distribu: ion systes consis:s of :wo load groups.)

1.

Two UV relays on each 4160V nonclass 1E bus. One relay is called ou: as the primary relay and :he a:her as the secondary relay with se:poin:s of 80% vol: age and 32-cycle time delay and tha: of 0 vol:s and :hree-second ti=e delay, respectively. Either of these relays will

rip the supply and feeder breakers :o the associa:ed 4153V class 1E bus and load shed the 4160V nonclass lE bus.

2.

Two UV relays on each 4160V class II bus. One se: a:

33 vol: age wi:5 'a 12-cycle ti=e delay tha: starts :he associated diesel generator. The o:her relay is se: a:

30" vol: age wi:h a three-second time delay. This relay sneds all 480 and 4160'V bus loads excep: :he 4160/430V

ansfor=ers feeding the emergency buses.

3.

Two UV relays, one each on the two 430V class lE buses, se: a: 33" of 430V and a 41-secend :i=e delay. These relays shed.all :he loads on : heir associa:ed 430V class 1E bus.

3.2 Modifica:icas. The existing UV relay fune: ions and/or se: points included in See:ica 3.1 will be i:eswise = edified as follevs:

1.

The relays on :he 4160V nonclass lE but will not ::ip the supply and feeder breakers to :he bus.

2.

The load-shedding relay on :he 4160V class 1E bus will hate i:s se: point changed :o 75* of 4160V wi:h a one-second :ise delay. This relay will ::ip the supply and feeder breakers to the bus and be used :o sense a loss-of-effsi:e pever.

3. -

The lead-sheddingL:elays on :he 430V class II buses will have their voltage se:poin:s changed :o 75% of a30V.

For second-level uncervoltage protec: ion, the licensee has proposed adding :wo relays.to each 4160V e=ergency bus,and two_ relays :o the secon-dary of :he 4160/030V ::ans for=er. feeding.cne of :he 430V, class 1E buses.

-These relays will have a se: point of 90

(+3, -0).of bus vol: age. Each I

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pair of :hese relays will have their con: acts wired in series :o a ti=ing relay se: for 90 5 seconds :ime delay on pickup. The timing relay will ini:ia:e the trip of the in:cming line and feeder breakers to :he al6CV, class 1E bus.

Load-shedding, once the diasel generator is supplying :he : lass *E:

buses, will be disabled. The load-shed feature will be reins:a:ed when the buses are supplied frem the offsi:e source.

Proposed changes :o the plant's :echnical specifications (adding :he surveilizn=e requiremen:s, allowable limits for :he se:poin: and ti e delay, and li=i:ing ::ndi: ions f:: opera: ion for the second-level undervol: age protection) were also furnished by :he licensee.

3.3 Discussion. The first posi: ion of :he NRC staff let:erl rec,uired :ha: a secend level of undervoltage protec: ion for :he onsite peuer sys:as be provided. The le::er s:igul::es o:her cri:eria :na: the undervoltage pro:ec:ica =us: =ee:.

Each cri:erion is resca:ed below followed by a discussion regardie; the licensee's complian:e wi:h :ha:

cri:eri:n.

1.

"Tne sele:: ion of vol: age and :i=e se: points shall be deter =ined from an analysis of :he vol: age require =ents of :he safe:y-rela:ed loads 4: all onsi:e system dis-

ribu: ion levels."

The li:rnsee's proposed se: point of 37447 a: the al60V bus is 90~ of :he motor-ra:ed voltage of al60V. Inis se:poin:, refle: ed down :o :he 130V buses, will be greater :han 90~ of :he motor-ra:ed vol: age.

As the so: ors are :he most limiting equipment in :he sys:em,

his se: point is accep:able.

2.

"The voltage pro:ee: ion shall include coincidence logic to preclude spurious : rips of :he offsite power sources."

The proposed modifi:a: ion incorporates a two-out-of-:vo logic scheme, thereby sa:isfying this cri:erion.

2.

"The ti=e delay sele::ed shall be based on :he fol-lowing conditions:

4.

The allowable :i=e delay, including margin, shall no: exceed the maximum time delay cha: is assumed in the FSAR a :ident analysis."

The proposed =axi=um :ise delay of 95 seconds does.

no: ex:eed :his =aximum time delay. This is sub-s:an:iated by the licensee in his proposal.

3

The proposed time delay will not be :he cause of any thermal damage to the safe:y-rela:ed equip-ment. The setpoint is wi:hin vol: age ranges recom-mended by ANSI C34.1-1977 for sus:ained operation.

b.

"The time delay shall minisize :he effec: of short-duration disturbances from reducing the unavail-ability of the off si:e power sour:e(s)."

The licensee's proposed minimum :i=e delay of 35 seconds is long enough :o override any enor:,

inconsequen:ial grid disturbancas. Further, I have reviewed :ne licensee's analysis and agree with :he licensee's finding : hat any voltage dips caused from the starting of large so: ors will no:

rip the offsite source, "The allowable :ime duration of a degraded voltage c.

condi:ica at all distribu: ion sys:es levels shall not resul: in failure of safe:y sys:e=s or Components."

A review of the licensee's voltage analysis 2,10,11 indica:es that the :i=e delay will not cause any failures of the safety-related equip =ent since :he voltage setpoin't is within :he allowable tolerance of the equipmen:-rated vol: age.

4.

"The voltage =onitors shall automa:ically initia:e the disconnec: ion of offsite power sources whenever the voltage se:poin: and time-delay li=i:s have been e x:ee de d. "

A review of :he licensee's proposal substan:iates that this cri:erion is set.

3.

The voltage moni: ors shall be designed :o satisfy the requirements of IEEE Standard 279-1971."

Ine licenses has sta:ed in his proposal : hat the modi-fica: ions are designed to =eet or exceed I EE S:an-dard 279.

5.

"The teennical specifica: ions shall include limiting cu..ditions for operations, surveillance requirements,

rip setpoints wi:h mini =um and maximum limits, and allowable values for the second-level voltage protec-tion monitors."

The licensee's proposal for :echnical specification changes includes all :he required i: ems.

The setpoint of 3744V (+123, -0) does no: infringe in:o the expected opera:ing envelope and will no: compromise :he life of 4

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the mo: ors.

Spurious : rips are, thereby, not foreseen.

The limi:ing conditions for operatien, calibration checks, and surveillance requirements mee: the criteria of the staff's posi: ions.

The ie:ond NRC staff post: ion requires :ha: the system design aute.-

natically prevent load-shedding of the emergen:y buses once the on:i:e sour:es are supplying pouer to all sequenced loads. The load-shedding nus:

also be reinsta:ed if the onsite breakers are tripped.

The licensee Pas s ated in his proposal :ha: :his position will ce me:

l.n:h*.nsvundervoltageprotectionscheme.

~

The third NRC staff position requires that :er:ain test requirements be added :o the technical specifications. These tes:s were to demonstra:e the full-functional operability and independence of the onsite power seu :es.. and are to be performed at leas: once per 13 montas during shu:-

down. The tes:s are to simulate loss of offsi:e power in conjunction wi:h estety-injection actuation signal, and :o si=ulate interruption and su'r-a sequer.c reconnection of onsi:e power sources. These tes:s verify :ne pr:per operatica of :he load-shed system, the load-shed bypass when the emergency diesel genera: ors are supplying power :o : heir respective buses, and tha:

there is no adverse in:eraction between the ensi:e and offsi:e power sources.

The exis:ing :es: proc'edures used by :he li:ensee comply wi:h :he full in:en: of :his procedure. Load-shedding on of f si:e power trip is :ested.

Load-sequencing, once the diesel genera:or is supplying :he safety buses, is tes:ed. The time dura: ions of the tes:s (3 minutes wi:h full safety loads) will verify tha: :he time delay is suffi:ien: to avoid spurious trips and tha: :he load-sned bypass cir:ui: is func:ioning properly, a.3 CONC'_US ION S 3ased on :he informa: ion provided by DLC, i: has been determined : hat ne proposed :hanges comply with NRC staff posi:ica 1.

All of the s:aff's requiremen:s and design base cri:eria have been net.

The setpoint and time delay will pro:ac: the : lass 12 equipmen: from a sustained degraded vol: age 4

conci: ion of the offsite power source.

.he me.4ified laad-shed cir:ui:ry ecmplies vi:h staf f posi: ion 2 ani vi* 1 prevent adverse interaction of the offsite and onsi:e emergency power sys: ems.

The proposed enanges to the :achnical specifications adequately :es:

he system modifications and comply with staff position 3.

The surveil-

& :t *=mii

-en;s, limiting conditions for operation, minimum and maxirus limi;s for _ the : rip se: point, and all:vable values =eet the inten: of staff

- posi: ion 1.

It is :here fore ' concluded ena: DLC's proposed modifications and tech-ni:21 specifica: ion changes.are-ac:eptable.

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5.0 REFERENCES

1.

NRC le::e (R. W. Reid) to DLC (C. N. Dunn), dated June 3, 1977 2.

DLC letter (C. N. Dunn) :o NRC (A. Schwencer), da:ed October 15, 1979.

3.

DLC letter (C. N. Dunn) :o NRC (S. A. Varga), da:ed May la,1930.

4.

DLC le :e (C. N. Dunn) to NRC (S. A. Varga), dated July 24, 1983.

5.

General Design Cri:erion 17 "Elec::ic Power Sys: ens," of Appen-dix A, 'Ceneral Design Cri:eria for Nu: lear *?cwer ?lancs," :o 10 CFR Par: 50, " Domes:i: Li:ensing of ?:odue: ion and Utili:a: ion Facili:ies."

6.

IEEE Standard 279-1971, " Criteria for ?:ste:: ion Sys:e=s fer Nuclear Power Generating S:ations."

7.

IIEE S:andard 303-1974, "S:andard Cri:eria for Class lE Power Systems for Nuclea: Power Generating Sta:icus."

3.

ANSI CSa.1-1977, "vol: age' Ra:ings for Ile:: ic Power Systems and Equipmen: (60 H:)."

9.

DLC let:e (C. N. Dunn) to. NRC (R. W. Reid), da:ed July 22, 1977.

10.

DLC le :e: (C. N. Dunn) :o NRC (R. W. Reid), dated November 11.

1976.

11.

DLC let:e (C. N. Dunn) :o NRC (A. Schwencer), dated February 22, 1980.

12.

Final Safety Analysis Repor (FSAR) for :he 3eaver Valley ? cue 5:ation, Uni: 1.

1