ML17261A949
| ML17261A949 | |
| Person / Time | |
|---|---|
| Site: | Point Beach, Turkey Point, Ginna, Robinson, 05000000 |
| Issue date: | 02/02/1990 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Rossi C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9002220345 | |
| Download: ML17261A949 (14) | |
Text
FEB Oa 1990 MEMORANDUM FOR:
Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation FROM:
SUBJECT:
Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data DESIGN DEFICIENCY OF WESTINGHOUSE SAFETY INJECTION BLOCK SWITCH On April 18, 1989, we issued the enclosed Technical Review Report, AEOD/T904, on a design deficiency of the Safety Injection (SI) block switch used at Point Beach Nuclear Plant, Unit 1.
The existing scheme uses a single "block/unblock" manual selector switch for both SI trains.
A licensee analysis indicates that a single failure of this switch can block low pressurizer pressure or low steam-line pressue SI signal in both trains.
On August 19, 1988, the Wisconsin Electric Power
- Company, the owner of the Point Beach Nuclear Plant, issued LER 88-007 detai ling the deficiency they had found in the existing scheme.
They have resolved the issue by installing two selector
- switches, one for each train.
At our initiation, Westinghouse, the NSSS vendor, has investigated the generic aspects of this single failure issue.
Westinghouse has identified three other plants - Ginna, Turkey Point Units 3
II 4, and and Robinson Unit 2 which use similar block switches.
Westinghouse has informed the licensees of these three plants of the problem and its proposed resolution (see enclosed copy of Westinghouse letters on this issue).
This completes our study on this issue.
Enclosures:
As stated Distribution:
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Sestlngh ouse Bectric Corporation Energy Systems RGE-89-647 Nucteat aad Mvanced Technol~ Oivlatcn Box 355 Ptttahtrgtt Peeeyharia 15230 0355 October 12, 1989 NS-DPLS-OPL-I-89-517 Hr. R. Biasz Rochester Gas and Electric Corp.
49 East Avenue Rochester, NY 14649 ROCHESTER GAS L ELECTRIC CORPORATION RE GINNA STATION
Dear Nr. Eliasz:
The purpose of this letter is to prov1de confirmat1on and formal not1ficat1on to you as follow-up to our telephone conversation of August 17, 1989.
The issue involves the use of a single switch to control the block/unblock function for both trains of safety in)ection.
During a control rooe design review at the Point Beach Nuclear Plant, the use of a single manual SI block/unblock switch for both SI trains was questioned.
A. subsequent, review led to the conclusion that a s1ngle failure of the switch (Mestinghouse OT2) could block either the automatic low pressurizer pressure or the low steamline pressure SI signal in both trains.
Point Beach prepared LER 88-007 (attached) on 9/16/88 describing in detail their review and conclusion.
Mestinghouse was contacted by the NRC informing us of the issue and requesting our review.
Mestinghouse has reviewed both the LER and the postulated sw1tch failure mechaniss and agrees that a single Mlure could cause the blocking of both SI trains.
Four contact blocks are stacked in series and operated by a single switch Iechanisa.
If the upper contact block internals stick it would cause both contacts to remain in the block position.
Hore recent Mestinghouse designs have provided one switch per train and Point Beach is planning to do the same.
RGE-89-647 NS-OPLS-OPL-1-89-517 October 12, 1989 Page 2
If automatic initiation of SI is blocked by a failed switch, an annunciator will alert the operator so that SI may be initiated manually.
The operator should also observe a failed switch during a normal cooldown for the same reason.
For most events, pressurizer pressure and steamline pressure SI are also backed up by SI initiation on containment pressure.
These coupled with the low probability of failure of a control board switch (10- /yr.)
provide sufficient 5ustification for continued operation until a convenient time to add a separate switch.
Our records (Dwg. $110E059 Sheet 3 Rev. 10) indicate that the above mentioned block functions were implemented with a single switch at Ginna.
Although not an immediate safety concern, westinghouse recommends that design changes be developed to provide separate block switches for each train.
Ifyou have any questions or comments, please contact the undersigned.
847~et,A.h4b S. DiTommso/
Attachment cc:
G. Mrobel, HQ D. Lewis, EUFS
ESTINGHOUSE ELECTRIC CORPORATION S.
. Swigart, Pro ct Hanager New York Area Customer Pro5ects Department
Ilestlnghouse Bectrlc Corporation Energy Systems Nuclear and Advanced Technology 0lvision 8ox 355 Pittsburgh Pemsylvanla 15230 0355 October 26, 1989 FPL-89-884 NS-OPLS-OPL-II-89-779 Nr. D. A. Chancy, Director Nuclear Licensing Department Florida Power 5 Light Company P. 0.
Box 14000 700 Universe Blvd Juno
- Beach, Florida 33408 Attention: Nr.
P.
L. Pace FLORIDA POMER 5 LIGHT COMPANY TURKEY POINT UNITS 3 Sr 4
Dear Hr. Hale:
The purpose of this letter is to provide confirmation and formal notification to you as follow-up to our telephone conversation of August 17, 1989.
The issue involves the use of a single switch to control the block/unblock function for both trains of safety injection.
During a control room design review at the Point Beach Nuclear Plant, the use of a single manual SI block/unblock switch for both SI trains was questioned.
A subsequent review led to the conclusion that a single failure of the switch (g OT2) could block either the automat1c low pressbrizer pressure or the low steamline pressure SI signal in both trains.
Point Beach prepared LER 88-007 (attached) on 9/16/88 describing in detail their review and conclusion.
M was contacted by the NRC informing us of the issue and request1ng our review.
JQ$ f,U~S g has reviewed both the LER and the postulated switch failure mechanism and agrees that a single failure could cause the blocking of both SI trains.
Four contact blocks are stacked in series and operated by a single switch mechanism.
If the upper contact block internals stick it would cause both contacts to remain in the block pos1tion.
Nore recent }f designs have provided one switch per train and Po1nt Beach is planning to do the same.
FPL-89-884 NS-OPLS-OPL-II-89-779 Page 2
A T
If automatic initiation of SI is blocked by a failed switch, an annunciator will alert the operator so that SI may initiated manually.
The operator should also observe a failed switch during a normal cooldown for the same reason.
For most events, pressurizer pressure and steamline pressure SI are also backed up by SI initiation on containment pressure.
These c~upl~d with the low probability of failure of a control board switch (10 10 /yr.) provide sufficient justification for continued operation until a convenient time to add a separate switch.
Our records (Dwg.
$110E188, sh 5, Rev.
- 10) indicate that the above mentioned block functions were implemented with a single switch on your plant.
Although not an immediate safety concern, Westinghouse recommends that design changes be developed to provide separate block switches for each train.
If you have any questions, please contact the undersigned.
Very truly yours, WESTINGHOUSE EL CTRIC CORPORATION e.
. J. Richards, Manager Florida Power 8 Light Project
~
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Nestlnghouse Bectrtc Corporat ton Enerlt Systems Box 355 Ptttsburgh PemsytetA 15230 0355 CPL-89-633 October 13, 1989 NS-OPLS-OPL-I I-89-751 Nr. R. E. Norgan General Nanager H. B. Robinson SEG Plant Carolina Power i Light Company P. 0. Box 790 Hartsville, NC 29550 CAROLINA POWER 5 LIGHT CONPANY H. B.
ROBINSON UNIT 2
Dear Nr. Norgan:
The purpose of this letter fs to provide confirmation and formal notification to you as follow-up to our telephone conversation of August 17, 1989.
The issue involves the use of a single switch to control the block/unb1ock function for both trains of safety fn5ectfon.
During a control room design review at the Point Beach Nuclear Plant, the use of a sfngle manual SI block/unblock switch for both SI trains was questioned.
A subsequent review led to the conclusion that a single failure of the switch (Westinghouse OTZ) could block either the automatic low pressurizer pressure or the low steamlfne pressure SI signal fn both trains.
Point Beach prepared LER 88-007 (attached) on 9/16/88 describing fn detail their review and conclusion.
westinghouse was contacted by the NRC informing us of the issue and requesting our review.
QHKKBQH westinghouse has reviewed both the LKR and the postulated switch failure mechanism and agrees that a single failure could cause ihe blocking of both SI trains.
Four contact blocks are stacked fn series and operated by a single switch iechanism, If the upper contact block internals stick ft would cause botg contacts to remain in the block position.
Nore recent westinghouse designs have provided one switch per train and Point Beach is planning to do the same.
E
Nr. R. E. Horgan
-2 CPL-89-633 October 13, 1989 If automatic initiation of SI is blocked by a failed switch, an annunciator will alert the operator so that SI may be initiated Ianually.
The operator should also observe a failed switch during a normal cooldown for the same reason.
For most events, pressurizer pressure and steamline pressure SI are also backed up by SI initiation on containment pressure.
These co~pled with the Iow probability of failure'f a control board switch {1D-5/yr.)
provide sufficient Justification for continued operation until a convenient time to add a separate switch.
Our records (Dwg. NIIOEI98 Sheet 6 Rev.
- 12) indicate that the above mentioned block functions were implemented with a single switch at H. B. Rohinson.
Although not an iamediate saf'ety concern, Mestin~house recoaeends that design changes be developed to provide separate b ock switches for each train.
Ifyou have any questions or coaeents, please contact the undersigned.
Very truly yours, WESTINGHOUSE ELECTRIC CORPORATION 6.
. Percival, a ager Carolina Area Customer Prospects Department
/gas cc:
R. E. Morgan (CPSL - HBR) 1L C. R. Oietz (COL - HBR) 1L J. H. Curley (CPSL - HBR) 1L D. H. Boatwright (COL - HBR) 1L B. H. Slone
{CPSL - HBR) 1L N. J.
Flanagan (COL - HBR) 1L L. I. Loflin {COL) 1L R. H. Parsons (COL) 1L T. B. Clements (CP8L) 1L C. lf. Crawford (COL) 1L R. L. Sanders
{CPEL) 1L J.
F. Nevill (COL) 1L R. J. Ruth (}f - HBR) 1L
- 6. S. Meingarten (M - Raleigh) 1L
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