ML20002A493
| ML20002A493 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 03/29/1978 |
| From: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WYR-78-34, NUDOCS 8011170361 | |
| Download: ML20002A493 (3) | |
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- YANKEE ATOMIC ELECTRIC COMPANY 20 Turnpike Rood Westborough, Mossochusetts 01581
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E United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Office of Nuclear Reactor Regulation
References:
(1) License No. DPR-3 (Docket No. 50-29)
(2) NRC letter dated August 12, 1976 (3) YAEC letter WR 76-96, dated September 16, 1976
Dear Sir:
Subject:
System Voltage Degradation Reference 2 required us to provide certain information with regard to plant operation and equiprent failures during degraded grid voltage condition.
Reference 3 provided this information; however, it has since come to our attention that the infonnation supplied under item 2 was incomplete, and possibly misleading. Please delete item 2 of Reference 3 and substitute it with Attachment A.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY l
HM R.'H. Groce Licensing Engineer x,_" -;"~ TG f
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ATTACHMEtTI A 2.
The functional safety requirements of the undervoltage trips is to detect the loss of offsite power system voltage and to initiate the necessary actions required to transfer safety related buses to the onsite power system.
At Yankee Rowe, a loss of voltage to the emergency 480 volt buses for more-than 1.8 seconds will result in the initiation of automatic load shedding and load sequencing.
Connected to each 480 volt emergency bus is an undervoltage relay (Relay 27).
When this relay senses a voltage below its set point it actuates and energizes an auxiliary relay (Relay 27X) which initiates the following action:
i (a)
It picks up a high speed lockout relay (Relay 86) electrically resetable by manual action. This relay (Relay 86) in turn isolates the emergency bus by tripping all incoming feeder breakers, starts the diesel generator, and permits closure of the diesel generator breakers.
'(b)
It trips the HPSI pump.
When the diesel generator is up to speed and voltage its breaker closes, thus restoring voltage to the emergency bus.
The auxiliary relay described above (Relay 27X) is now de-energized, precipitating the following action:
(a) The LPSI pump is started.
(b) The HPSI pump trip is removed and a permissive is given for it to start.
When the voltage recovers to normal (after the LPSI pump has started) a 10 second timer is initiated which then starts the HPSI pump. This action completes the load sequencing.
It should be noted that the load shedding feature for the HPSI pump, is retained.
The LPSI pump is never shed. The' retention of the HPSI load shedding is justified based on the fact that no other loads are sequenced following the HPSI pump; therefore, there' is no possibility of subsequent low voltages occurring that could interfere with or prevent the HPSI pump f rom performing its safety function.
Moreover, Section 8.3.1.1.5 of the FSAR states that when the HPSI
. pump is started a' voltage dip of 15% occurs with a recovery time of 3 seconds.
Item le of Reference 3 shows that the undervoltage relay (Relay
- 27) initiating HPSI pump load shedding will actuate in 7 seconds with a 20% voltage drop.
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Of OfO REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
DISTRIBUTIOf4 FOR INCOMItJG. MATERIAL 50-029-REC:
ORG: GROCE R H DOCDATE: 03/29/78
.NRC YANKEE ATOMIC ELEC DATE RCVD: 04/04/78 DOCTYPE: LETTER.
NOTARIZED: NO COPIES RECEIVED LTR 3 ENCL 40
SUBJECT:
COMMENTS RE: SYSTEM VOLTAGE DEGRADATION.
PLANT NAME: YANKEE ROWE REVIEWER INITI AL:
XRS DISTRIBUTOR INITIAL:
- t-**********
DISTRIBUTION OF THIS MATERIAL IS AS FOLLOWS ******************
GENERAL DISTRIBUTION FOR AFTER ISSUANCE OF OPERATING LICENSE.
(DISTRIEUTION CODE AOO1)
FOR ACTIOt4:
BR. CHIEF'7IEMANN**W/7 ENCL kREG FILE **W/ ENCL NRC PDR**W/ ENCL INTERNAL:
F'tc E**W/2 ENCt~
OELD**LTR ONLY HANAUER**W/ ENCL CHECK **W/ ENCL EISENHUT*tW/ ENCL SHAO**W/ ENCL EAER**W/ ENCL BUTLER **W/ ENCL GRIMES **W/ ENCL J ~;OLLINS**W/ ENCL J.
MCGOUGH**W/ ENCL EXTERNAL:
LPDR'S GREENFIELD, MA**W/ ENCL TIC **W/ ENCL NSIC**W/ ENCL ACRS CAT B**W/16 ENCL 1
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o DISTRIBUTION:
LTR 40 ENCL 39 CONTROL NBR:
7SO970314 SIZE: 1P+1P
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- THE END
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