k k 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 1 1 0 1 0 1 1 NRR LASHER' NRR/DEBT/PBH NRR/DLPG/GAH NRR/PMAS/ ILRH OGC/HDS2 RES/DE/EI H 1 1 0 1 0 1 0 1 0 1 1 EXTERNAL: LPDR NSIC NRC PDR 1 1 TOTAL NUMHER OF COPIES REQUIRED: LTTR 20 ENCL 12
Transcript
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REQULAT INFORMATION DISTRIBUTION STEM (BIDS)
ACCESSION NHR: 8707210600 DOC. DATE: 87/07/15 NOTARIZED: NOFACIL: 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)
DOCKET0500033505000389
BUHJECT: Forwards info on diverse scram sos conceptual design 5plant-specific auxiliary feedwater actuating sos/reactorprotective sgs diversity study'er 861103 commitment.
NRR LASHER'NRR/DEBT/PBHNRR/DLPG/GAHNRR/PMAS/ ILRHOGC/HDS2RES/DE/EI H
1
1 01 01 01 01 1
EXTERNAL: LPDRNSIC
NRC PDR 1 1
TOTAL NUMHER OF COPIES REQUIRED: LTTR 20 ENCL 12
P. X 14000, JUNO BEACH, FL 33408
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FLORIDA POWER 8 LIGHT COMPANY
QU'Q i5 198~
L-87-30 I
10CFR50.62
U. S. Nuclear Regulatory CommissionAttn: Document Control DeskWashington, D.C. 20555
Gentlemen:
Re: St. Lucie Units I and 2Docket Nos. 50-335 and 50-389Anticipated Transients WithoutScram (ATWS) Plant S ecific Information
In accordance with Florida Power & Light Company (FPL) letter L-86-446, datedNovember 3, l986, the plant specific Diverse Scram System Conceptual Designand the plant specific AFAS/RPS Diversity Study are enclosed.
Should any additional information be required, please contact us.
Yery truly yours,
~ ~C. O. WoGroup Y PresidentNuclear Energy Department
COW/GRM/gp
Enclosures (2)
cc: Dr..J. Nelson Grace, Regional Administrator, Region II, USNRCSenior Resident Inspector, USNRC, St. Lucie Plant
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ST. LUCIE UNIT 2 RPS BISTABLESCHEMATIC NO. 34868 CARD PART NO. 34610
ST. LUCIE UNITS 1 AND 2 AFAS BISTABLESCHEMATIC NO. 33441 CARD PART NO. 33440
FIGURE 5.5
ST. LUCIE UNITS I AND 2AFAS BISTABLE AND MATRIXRELAY CARD
FIGURE 5.6
ST. LUCIE UNIT 1 RPS MATRIXRELAYORIGINALCLARE RELAYSHOWN WITH THE
REPLACEMENT DOUGLAS RANDALASSEMBLY
ST. LUCIE UNIT 2 RPS MATRIXRELAY CARDPART 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 of10CFR50. 62.
The Hendric Rule 46FR57521 proposed to resolve ATWS by establishing areliability assurance program for systems that prevent or mitigate ATWS
accidents.
The Hendric Rule recognized that reliability/availability is the key toreducing ATWS risk. In addition to the Final Rule requirementsCommissioner Roberts suggested a reliability assurance program toimprove plant safety.
Clearly, reliability and safety are most important. The final ATWS rulewith its diversity requirements is intended to improve these twoqualities by diversity and resistance to common mode failures.
The initial reliability of a system depends upon piece parts selectioncriteria, circuit design margins (derating), packaging, parts screeningtest, assembly burn-in, and many other mechanical, electrical,electronic, and environmental considerations.
After installation and startup, failure rates may be relatively high asweak 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 anddeficiencies, the system approaches a minimum failure rate and maximumsustained reliability. In a well designed all solid state system, thisreliability is sustained indefinitely since there is no wear outcharacteristic. The St Lucie RPS and AFAS have reached this maturelevel of reliability and proposed system changes to increase hardwarediversity should be approached with extreme caution.
-18- 0381I/0031I
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APPENDIX A
NRC EVALUATION OF CEN-315 SUMMARY OF THE DIVERSITY BETWEEN THE REACTOR TRIPSYSTEM 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 differentmanufacturers than the AFWS bistables and power supplies. Both the RPS andAFWS matrix relays, however, are Douglas Randall electromechanical (reedswitch) relays. The relays have different model numbers and the associatedpower supplies are from different manufacturers and have different voltageratings. The RPS and AFWS initiation relays are both electromechanicalrelays, but are from different manufacturers. The associated power suppliesare also from different manufacturers and use AC versus DC power. The finalactuation devices are from different manufacturers, and use different powersupplies and principles of operation.
CEN-315 claims that although the matrix relays have the same manufacturer anddesign principle, since they are different models and have different DC powersources, that an adequate level of diversity exists between the two systems.The staff can not reach a conclusion regarding the acceptability of diversitybetween RPS and AFWS matrix relays based on the information„ provided. Thedifferences in the physical and operational characteristics of the two modelsmust be analyzed to determine the potential for CMF mechanism affecting thetwo models.
The RPS and AFWS bistables, initiation relays, and actuation devices appear tobe sufficiently diverse to satisfy the diversity requirements of the ATWS
rule. The plant specific submittal should include additional informationconcerning similarities and differences between the RPS and AFWS matrix relaysand how these factors affect their susceptibility to CMFs.
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DIVERSITY BETWEEN THE EXI ING REACTOR TRIP SYSTEIMIAND AUXILIARYFEEDNATER SYSTEM ACTUATIONCIRCUITRY FOR
