L-87-301, Forwards Info on Diverse Scram Sys Conceptual Design & plant-specific Auxiliary Feedwater Actuating Sys/Reactor Protective Sys Diversity Study,Per 861103 Commitment
| ML17308A240 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie |
| Issue date: | 07/15/1987 |
| From: | Woody C FLORIDA POWER & LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| L-87-301, NUDOCS 8707210600 | |
| Download: ML17308A240 (20) | |
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REQULAT INFORMATION DISTRIBUTION STEM (BIDS)
ACCESSION NHR: 8707210600 DOC. DATE: 87/07/15 NOTARIZED:
NO FACIL: 50-335 St.
Lucie Planti Unit ii Florida Power 5 Light Co.
50-389 St.
Lucie Planti Unit 2i Florida Power 5 Light Co.
AUTH. NAME AUTHOR AFFILIATION WOODY'. O.
Florida Power 5 Light Co.
REC IP. NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
DOCKET 05000335 05000389 BUHJECT: Forwards info on diverse scram sos conceptual design 5
plant-specific auxiliary feedwater actuating sos/reactor protective sgs diversity study'er 861103 commitment.
aa.c DISTRIBUTION CODE:
A055D COPIES RECEIVED: LTR J ENCL Q SIZE:
TITLE: OR/Licensing Submittal:
Salem ATWS Events GL-83-28 NOTES:
REC IP IENT ID CODE/NAME PD2-2 LA TOURIGNYe E COPIES LTTR ENCL 1
0 1
RECIPIENT ID CODE/NAME PD2-2 PD COPIES LTTR ENCL 3
3 INTERNAL: ARM/DAF/LFMH NRR/DEBT/ICSH NRR/DEST/RSH NRR/DOEA/QCH S/PMSH REG IL 01 1
0 1
1 1
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1 NRR LASHER' NRR/DEBT/PBH NRR/DLPG/GAH NRR/PMAS/ ILRH OGC/HDS2 RES/DE/EI H 1
1 0
1 0
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1 0
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EXTERNAL:
1 TOTAL NUMHER OF COPIES REQUIRED:
LTTR 20 ENCL 12
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X 14000, JUNO BEACH, FL 33408 iiIIII jj'r~~~4 FLORIDAPOWER 8 LIGHT COMPANY QU'Q i5 198~
L-87-30 I 10CFR50.62 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:
Re: St. Lucie Units I and 2 Docket Nos. 50-335 and 50-389 Anticipated Transients Without Scram (ATWS) Plant S ecific Information In accordance with Florida Power & Light Company (FPL) letter L-86-446, dated November 3,
l986, the plant specific Diverse Scram System Conceptual Design and the plant specific AFAS/RPS Diversity Study are enclosed.
Should any additional information be required, please contact us.
Yery truly yours,
~
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C. O. Wo Group Y President Nuclear Energy Department COW/GRM/gp Enclosures (2) cc:
Dr..J. Nelson Grace, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant r e7ovaioboo ooss5 Pgg ggOCK O500pg~
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ST. LUCIE UNIT 2 RPS BISTABLE SCHEMATIC NO. 34868 CARD PART NO. 34610 ST. LUCIE UNITS 1 AND 2 AFAS BISTABLE SCHEMATIC NO. 33441 CARD PART NO. 33440 FIGURE 5.5
ST. LUCIE UNITS I AND 2 AFAS BISTABLE AND MATRIXRELAY CARD FIGURE 5.6
ST. LUCIE UNIT 1 RPS MATRIXRELAY ORIGINALCLARE RELAYSHOWN WITH THE REPLACEMENT DOUGLAS RANDALASSEMBLY ST. LUCIE UNIT 2 RPS MATRIXRELAY CARD PART NO. 34610 FIGURE 5.7
- 6. 0 SYSTEM RELIABILITYAND RESISTANCE TO COMMON MODE FAILURES Diversity by itself is not sufficient to satisfy the intent of the ATWS Rule.
Several proposals to solve ATWS preceeded the requirements of 10CFR50. 62.
The Hendric Rule 46FR57521 proposed to resolve ATWS by establishing a
reliability assurance program for systems that prevent or mitigate ATWS accidents.
The Hendric Rule recognized that reliability/availability is the key to reducing ATWS risk.
In addition to the Final Rule requirements Commissioner Roberts suggested a reliability assurance program to improve plant safety.
Clearly, reliability and safety are most important.
The final ATWS rule with its diversity requirements is intended to improve these two qualities by diversity and resistance to common mode failures.
The initial reliability of a system depends upon piece parts selection criteria, circuit design margins (derating),
packaging, parts screening
- test, assembly burn-in, and many other mechanical, electrical, electronic, and environmental considerations.
After installation and startup, failure rates may be relatively high as weak parts, that escaped the test screens, are weeded out of the system.
Accumulation of system operation time acts to eliminate latent defects.
As operating time increases, the resistance to all failure modes, including common mode failures, increases.
After a few years of operation and correction of defects and deficiencies, the system approaches a minimum failure rate and maximum sustained reliability.
In a well designed all solid state system, this reliability is sustained indefinitely since there is no wear out characteristic.
The St Lucie RPS and AFAS have reached this mature level of reliability and proposed system changes to increase hardware diversity should be approached with extreme caution. 0381I/0031I
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APPENDIX A NRC EVALUATION OF CEN-315
SUMMARY
OF THE DIVERSITY BETWEEN THE REACTOR TRIP SYSTEM AND THE AUXILIARYFEEDWATER ACTUATION SYSTEM FOR CE PLANTS St. Lucie Unit 1 (Fi ure 6)
The RPS bistables and associated DC power supplies are from different manufacturers than the AFWS bistables and power supplies.
Both the RPS and AFWS matrix relays,
- however, are Douglas Randall electromechanical (reed switch) relays.
The relays have different model numbers and the associated power supplies are from different manufacturers and have different voltage ratings.
The RPS and AFWS initiation relays are both electromechanical
- relays, but are from different manufacturers.
The associated power supplies are also from different manufacturers and use AC versus DC power.
The final actuation devices are from different manufacturers, and use different power supplies and principles of operation.
CEN-315 claims that although the matrix relays have the same manufacturer and design principle, since they are different models and have different DC power
- sources, that an adequate level of diversity exists between the two systems.
The staff can not reach a conclusion regarding the acceptability of diversity between RPS and AFWS matrix relays based on the information provided.
The differences in the physical and operational characteristics of the two models must be analyzed to determine the potential for CMF mechanism affecting the two models.
The RPS and AFWS bistables, initiation relays, and actuation devices appear to be sufficiently diverse to satisfy the diversity requirements of the ATWS rule.
The plant specific submittal should include additional information concerning similarities and differences between the RPS and AFWS matrix relays and how these factors affect their susceptibility to CMFs. 0381I/0031I
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DIVERSITY BETWEEN THE EXI ING REACTOR TRIP SYSTEIMI AND AUXILIARYFEEDNATER SYSTEM ACTUATIONCIRCUITRY FOR ST. LUCIE UNIT 1 SENSORS STEAM GENERATOR LEVEI.
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SENSORS ARE NOT INCLUDED IN THE SCOPE I
OF THE ATWS RULE BISTABLE GULF MODEL ELD240-0000-IF COMPARATORI CLARE RELAYS POWER MATE
+16 VDC SUPPLY DOUGLAS RANDALL MODEL 378907 ELECTRO-MECHANICAL RELAYS GENERAL ELECTRIC "K"RELAY MODEL 12 NGV 13 A1A ELECTRO-MECHANICAL RELAY GENERAL ELECTRIC MODEL AK-2-25 s CIRCUIT BREAKERS UV & SHUNT TRIP COILS AC VITAL POWER MATE BUS 28VDC A
SUPPLY VITAL BUS ISOLATION RANSFORMER AC VITAL BUS 125 VDC BUS AC VITAL~
BUS TODD 12 VDC SUPPLY
'ODD 12 VDC SUPPLYo AC VITAL BUS IMIATRIXRELAYS 'NITIATIONRELAYS ACTUATIONDEVICE REACTOR TRIP SYSTEM ACTUATION CIRCUITRY E-M MODEL 33440 SUMMER/
DOUGLAS RANDALL RfLAY DOUGLAS RANDALL MODEL 29350 ELECTRO-MECHANICAL RELAYS POTTER BRUMFIELD MODEL R10-E1-W2-6800 ELECTRO-MECHANICAL RELAY E-M MODEL 4208 ELECTRO-MECHANICAL RELAY AUXILIARY FEEDWATER SYSTEM ACTUATION CIRCUITRY iAUCTIONEERED, FIGURE 6
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