technical specifications for class 1e vital instrument buses
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REQUEST FOR OMS REVIEW*
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PL 96 5111:Che:v cne!Technical Specifications for Class 1E c ,,: .se::.:. 35 c7 sa.r.ss,:..,
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- 4:s a: .Nse:s anc uses (5 *: :s : : orsi. 'NRC plans to issue a letter requesting additional data from licensees on technicalik
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specifications for Class lE Vital Instruments Buses.
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SUPPORTIliG STATEMEliT
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1. Justification
A review of nuclear plant operating experience shows th7.t plantsafety could be improved by restricting the way electrical power issupplied to instrumentation important to safety. fiornally, the porterto this instrumentation ecmes from " vital" power sources (usually 4)
i that are uninterruptable. However, during maintenance on a vitalpower source, one vital source is taken out of service, and a lessreliable power source (interruptable) is used instead. The problemis that the vital source con be taken out of service for an indefinatelength of time. Info mation obtained from the nucTear plant utilities(licensees) will pertrit the fiRC to change their plant licensees to
; restrict the out of service time of the vital power source.
The information requested is available only from the individual *
licensees, and h=s not been previously sent to.,the fiRC.,
'2. Descriotion of Survey Plan, ,
1) This request for information will be sent to licensees withpressurized water reactor (PWR) nuclear plants. The number,
' of these plants is about 45. A mailing list for these plantsis available at the fiRC.
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; 2) fio survey design is needed as this request is not a survey.i Licensee non-response cou'id cause the fiRC to issue ORDERS' requiring the licensee to respond.
3) fiA;
4) liAI 3. Tabulation and Publication Plans!
Information requested by this letter will not be tabulated for theipurpose of publication.' 'The fiRC staff will review the information
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to determine compliance with fiRC requirements. On completion of'
that review, a Safety Evaluation Report will be sent to each PWR,^ . licensee and b.e made available to the public.
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4. Time Schedule for Data Collection and Publication
Information requested by this letter will be due from the licensees30 days after their receipt of the letter. Our Safety EvaluationReports should be completed by July 1982. As previously mentioned,
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information collected by this letter will not be oublished.,
5. Consultations Outside the Acency
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6. Estimation of Respondent Reportine Burden.
The estimated average number of hours required per response isbased upon NRC experience with requests of this nature.
7. Sensitive Ouestions
NA ,
S. Estimate of Cost to Federal Government
This letter request is not a survey. Total cost tb the covernmentwill be 50 professional man days and $200,000 technical issistance funds.
9. Practical Utility. .
The inftrmation received from this letter will. form the legal basisto improve plant sa fety. The date for submission of the informationis practical. Resources are available to review the information, as'
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a contractor has been retained. -
10. Necessity
The primary mission of the NRC is to ensure that the design, constructionand operation cf nuclear power plants does not endanger the health andsafety of the public. As the NRC becomes aware of new ways to improveplant safety, requirements are issued to the licensees. The informationreceived from the licensees will use to upgrade the safety of the plants.
11 Co:y Reauirements
This information request will require the licensees to submit' to the NRCan a; plication for amendment to their license under 10 CFR 50
12. Record Retention
The information submitted by the licensees will be retained for thelife of the.nu_ clear facility (normally at least 30 40 years).
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393 Cscoq#o-
UNITED STATES#..
- J '' "i a f [ g NUCLEAR R,5GULATORY COMMISSIONe- *t "j.g WA5MINGTON. O. C. 20555g . ,
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TO ALL PWR LICENSEES .
(Generic Letter No. 81- ).}|| ;'
SU5 JECT: TECHNICAL SPECIFICATIONS (TSs) FOR CLASS lE 120 VAC VITAL Ifi3TRU--
MENT BUSES
Gentlemen: ,.
Based upon our review of plant operating experience, we have deteminedthat some operating nuclear power plants do not have TSs that restrictthe operability of their Class 1E 120 VAC vital buses and associated DC ,
powered invertors. The lack of such restrictions will allow a vital busor associated invertor to be taken out of service for an indefinitelength of time. Safety systems that require these power supplies to per- -
form their functions are then left in an operating mode for a significantperiod of time without Class lE qualified backup supplies. In some plantdesigns de-energizing two vital buses will cause spurious engineered
! safety features (ESF) actuations. In other plants, the loss of power onI two buses can prevent automatic actuation of ESF systems. Such situationsj are unacceptable and require corrective action. Placing limitations on
the time that a vital bus is not energized from its DC powered invertor pro-vides substantial safety improvement.*
Consequently, you are requested to propose an amendment to your TS::,
1 utilizing the enclosed model TSs for guidance. Please submit your pro-j posed amendment to us withir. 30 days of receipt of this letter.
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' Sincerely,-.
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j Darrell G. Eisenhut, DirectorDivision of LicensingOffice of Nuclear Reactor Regulation i
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Enel osure: -
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| Fodel Technical Specifications..
t c w/ enclosure: .
Service Lists i,
This request for information has been reviewed by the Office of Management*
; and Budget with approval # which expires>
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i ELECTRICAL POWER SYSTEMS!
j 3/4.8.2 ONSITE POWER DISTRIBUTION SYSTEMS |
A.C. DISTRISTION - OPERATING
L7MIT]NG CONDITION FOR OPERATION'
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3.8.2.1 The following A.C. electrical busses and inverters shall be OPERABLE-
and energized with tie breakers open between redundant busses:
(4160) volt Emergency Bus #<
4 (4160) volt Emergency Bus #
(480) volt Emergency Bus #'
; (480) volt Emergency Bus #
(120) volt A.C. Vital Sus # . energized from inverter #. .
j connected to D.C. Bus Train "A'.'" and 480 Volt Emergency sus # .
; (120) volt A.C. Vital Bus # energized 'from inverter #; connected to D.C. Sus Train "A"* and 480 Velt Energency Bus # .
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| (120) volt A.C. Vital Bus # energized from inverter #* *
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1 connected to D.C. Sus Train "B"* and 480 Volt Emergency Bus # .,
) (120) volt A.C. Vital Bus # energized from inverter #| connected to D.C. Sus Train "S"* and 480 Volt Energency Bus # .
j APPLICABILITY: MODES 1, 2, 3, and 4.! ACTION:
; a. With less than the above complement of A.C. busses. 0?ERAELE and energized, -
1 restore the inoperable btisses to OPERABLE and energized status withini 8 hours or be in at least HDT STANDBY within the next 6 hours and in COLD| SHUTDOWN within the following 30 hours. .
j b. With one inverter inoperable, energize the associated A.C. Vital Bus .
j within 8 hours; restore the inoperable inverter to OPERABLE and energized'
! status within 24 hours or be in at least HOT STAND 5Y within the next6 hours and in COLD SHUTDOWN within the following 30 hours.
SURVEILLANCE REOU!REMENTSi
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j 4.,8.2.1 The specifi&d A.C. busses and inverters shall be determined OPERABLE-and energized with tie breakers open between redundant busses at least once ;
per 7 days by verifying correct breaker alignment and indicated voltage on thej busses. .
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Two irverters may be disconnected from their D.C. source for up to 24 hours.
for the purpose of performing an equalizing charge on.their asscciated; battery bank provided (1) their vital buses are OPERABLE and energized, and
(2) the vital busses associated with the other battery tank are OPERASLE and~energized.
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ELECTRlCAL POWER SYSTEMS~
A.C. DISTRIBUTION - SHUTDOWN
LIMITING CONDITION FOR OPERATION
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3.8.2.2 As a minimum, the following A.C. electrical busses and invertersshall be OPERABLE and energized:
1 - (4160) volt Emergency Bus'
1 - (480) volt Emergency Bus s
2 - (120) volt A.C. Vital Busses energized from their respectiveinverters connected to their respective D.C. Bus Train and 480 Volt,
Emergency Bus. ,
APPLICABILITY: MODES 5 and 6. .
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ACTION: ,~
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With less than the above complement of A.C. busses and inverters OPERABLE andenergized, establish CONTAINMENT INTEGRITY within 8 hours.
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SURVEILLANCE REOUIREMENTS.
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4. 8. 2.'2 The specified A.C. busses and inverters shall be determined-0PERABLE: and energized at least once per 7 days by verifying correct breaker alignment|
and inoicated voltage on the busses.;
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