ML18030A222
| ML18030A222 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 03/02/1981 |
| From: | Curtis N PENNSYLVANIA POWER & LIGHT CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, PLA-638, NUDOCS 8103090408 | |
| Download: ML18030A222 (5) | |
Text
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0 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIOS)
ACCESSION NBR t 8103090408 OOC ~ DATE: 81/03/02 NOTARIZED; NO DOCKET ¹ FACIL:5 Susquehanna Steam Electric Stationr LJn{ t 1r Pennsyl va 05000387 0
388 squehanna Steam Electric Stationr Unit 2i Pennsy1va 05000388 AU, AUTHOR AFFILI4TION CURT r
~ 'H ~
Pennsylvania Power 8 Light Co ~
REC IP ~ LIAME RECTPIEtJT AFFILIATION GRIERr B ~ H ~
Reqinn lr philadelphiar Office of the Director
SUBJECT:
Status update of deficiency re excessive voltaqe droos in power 8 control circuits initially reported R01020,Partial stop work on Unit 2 cable installation for affected circuits imolemented,Final rept will he submitted in May 1981, DISTRIBUTION CODE:
80198 COPIES RECEIVED:LTR Q ENCL SIZE-'ITLE:
Construction Deficiency Repor t (10CFR50.55E)
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PAL TWO NORTH NINTH STREET, ALLENTOWN, PA. 18101 PHONE: t2 I S) 770-5151 so-3~~
3ZZ NORMAN W. CURTIS vice Presidenr-Engineering rL Constrrrcgon-Nucieer 770538I March 2, 1981 Mr. Boyce H. Grier Director, Region I U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 SUSQUEHANNA STEAM ELECTRIC STATION STATUS UPDATE OF A DEFICIENCY RELATING TO EXCESSIVE VOLTAGE DROPS IN POWER AND CONTROL CIRCUITS ERs 100450/100508 PLA-638
References:
PLA-560 (10/20/80)
PLA-570 (11/17/80)
Dear Mr. Grier:
This letter serves to supplement the above referenced correspondence which advised the Commission of deficiencies relating to AC motor operated valve control circuits (PLA-560) and DC power supply cables (PLA-570).
Due to similarities in the causes and the corrective actions required to resolve these conditions, PPGL has chosen to address both problems in this combined response.
PP&L in'iated Deficiency Report (DR) I 0138 on November 26, 1980 which described the deficiencies detected in the AC and DC circuit designs.
In addition to resolv'ng.tnese design deficiencies, Bechtel has also been directed to 'dentify and correct the cause of the design problems in order to preclude recu"rence.
PPGL has also invoked a partial stop work on Unit 2 cable installation for all circuits which may be affected.
Po/1 S>O309('4 08 PENN 5 Y LVANIA POWER IL LIGHT COMPANYr
Mr. Boyce H. Grier Max'ch 2, 1981 Pursuant to the oxovisions of 10 CPR 50.55(e),
the attachment to this letter provides:
a description of the problem; the probable causes; an analysis of safety implications; and the corrective action planned.
We anticipate that a final repox't on these deficiencies will be submitted in May, 1981.
Very truly yours, N.
W. Curtis Vice President-Engineering 6 Construction-Nuclear FLW:sab Attachment cc:
Mr. Victor Stello (15)
Director-Office of Inspection
& Enforcement U.
S. Nuclear Regulatory Commission Washington, D.C.
20555 Mr. G..McDonald, Director (1)
Office of Management Information
& Program Control U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Mr. Robert M. Gallo U. S. Nuclear Regulatoxy Commission P.
O.
Box 52 Shickshinny, PA 18655
At ent to PLA-638 Status Reoort
~sub ece Excessive voltage drop in power and control circuits.
Descriation of Problem Excessive voltage drop occurs in various power and control circuits when motors are started or coils are energized. 'he specific problem areas at Susquehanna SES are:
l.
AC motor starters (motor starters are devices which provide the control of power to motors.) - Excessive control cable resistance caused excessive voltage drop in control cables.
This resulted in inadequate voltage across the terminals (less than 85% of rated voltage) of the motor starter.
The motor starter could not operate at this reduced
- voltage, and therefore, the motor would fail to operate.
A review of all safety related AC motor starter control circuits has shown that excessive control cable resistance existed for fifty nine (59) safety-related motor starters.
These starters control the power to motors for valves,
- pumps, and fans.
2.
250V DC power cables - Excessive power cable resistance caused excessive voltage drop in power cables.
This resulted in inadequate voltage (less than 80% of rated voltage) across the terminals of 250V DC motors used to operate valves.
The motors would not start at this reduced voltage.
Analysis of all safety related DC motor circuits has shown that excessive power cable resistance existed for fourteen (14) safety-related 250V DC
.motor operated valves.
3.
4.16Kv Circuit Breaker Controls - Excessive control cable resistance caused excessive voltage drop in 125V DC control cables.
This resulted in inadequate voltage across the close (less than 90 volts DC) coils of 4.16Kv circuit breakers.
The subject circuit breakers would fail to operate when required.
Analysis of all 4.16Kv circuit breaker control circuits has shown that-excessive control cable resistance existed for four (4) safety-related 4.16Kv circuit breakers.
Cause The most probable causes of the low voltageprcblem are 1) a lack of attention to detail in the area of permissible voltage drops in powe" and control cables by the circuit design engineer, 2) a lack of cont"ol on final cable lengths by the engineer(s) at Bechtel who designed the subject
- schemes, and 3) a lack of design criteria and design documentation by Bechtel that orovided control of cable size and length by the design engineer.
Page 1 of 2
chment to PLA-638 Anal sis of Safety Implications These design deficiencies affect multiple components of various safety related systems.
The systems include Residual Heat Removal, Reactor Core Isolation Cooling, and High Pressure Coolant Injection.
The nature of the design deficiency is such that critical equipment will not be controllable to perform design safety functions.
Engineering considers this deficiency to be reportable under 10CPR 50.55(e).
Corrective Action 1.
AC motor starters - Interposing relays or, larger control transformers (whichever is appropriate) will be installed in the deficient motor starter control circuits.
Interposing relays require less power than motor starters and can ope ate satisfactorily with existing control cables.
The interposing relay contacts will control the motor starters through rewired low impedance circuits.
In some cases, larger control transformers could be used because the voltage drop across these transformers is less since the load remains the same.
This allows a larg r voltage drop in the control cable.
In using this fix, the total drop in the larger control transformer and the existing control cable must not be so great as to allow the starter voltage to drop below 85% of rated.
2.
250V DC power cables existing power cables will be replaced with larger power cables for the subject devices.
3.
4.16Kv circuit breaker controls interposing relays, applied similarly to
~ the description in item 1 above, will be installed.
Schedule for Completion These changes will be accomplished on Unit 1 prior to tray 1, 1981.
Corrective action for Unit 2 will be addressed in our final report.
Page 2 of 2