ML20154G285
| ML20154G285 | |
| Person / Time | |
|---|---|
| Issue date: | 04/19/1988 |
| From: | Huan Li Office of Nuclear Reactor Regulation |
| To: | Newberry S Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8805240301 | |
| Download: ML20154G285 (13) | |
Text
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APR 191929 MEMORANDUM FOR:
Scott Newberry, Acting Chief Instrumentation & Control Systems Branch Division of Enginearing & Systems Technology THRU:
Jerry Mauck, Section Chief Instrumentation & Control Systems Branch i
Division of Enginctring & Systems Technology FROM:
Hulbert C. Li Instrumentation & Control Systems Branch Division of Engineering & Systems Technology
SUBJECT:
SUMMARY
OF MEETING WITH BWR OWNERS' GROUP TO DISCUSS DIVERSITY REQUIREMENTS FOR ATWS RULE (10CFR50.62)
IMPLEMENTATION i
On April 7, 1988 NRC staff members met with the BWR Owners Group and represent-atives from General Electric to discuss, on a generic basis, the diversity requirements for the ATWS Rule (10CFR50.62) implementation. This issue was raised during a plant-specific technical specification (TS) review on Brunswick Unit 2 ATWS mitigation system TS changes. During this review, the staff concluded that Brunswick had installed the same type of analog transmitter and trip units (ATTU) for the ATWS/ARI system and the reactor trip system, which does not appear to be in conformance with the ATWS Rule. The BWROG believes that this issue has generic implications and, during the meeting, presented their basis for concluding that hardware diversity is not needed to satisfy the diversity requirements of the ATWS Rule.
This belief is cased on the extent of existing functional diversity within the General Electric reactor trip system and the fact that hardware diversity would add very little to safety. A limited
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PRA was provided by the BWR0G to support their view along with a rough estimate i
(verbal) for the cost of implementing hardware diversity at a plant that has installed this non-diverse ATWS instrumentation. The staff requested that the BWROG fomally submit the information provided during the meeting. We intend to review this information and provide our conclusions in a subsequent safety evaluation.
The copy of the slides from the BWROG presentation are attached in Enclosure 1.
A list of the meeting attendees is in Enclosure 2.
8805240301 880419 PDR TOPRP Et1VGENE Hulbert C. Li C
PDR In trumentation & Control Systems Branch Divuion of Engineering & Systems Technology
Enclosures:
As stated cc: See page 2 DISTRIBUTION:
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Contact:
H. Li (S SD/ DEST), x20781 ICSB RF k}'I NRC PDR SICB: DEST ST SIC EST L PDR t
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1 Scott Newberry cc w/ enclosures:
J. Sniezek T. Martin L. Shao A. Thadani E. Adensam W. Hodges T. Collins R. Jones D. Lynch E. Sylvester SICB Members
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ENCLOSURE I i
BWR OWNERS' GROUP /NRC MEETING ATWS ANALOG TRIP UNIT DIVERSITY APRIL 7, 1988 ROCKVILLE, MD d
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MEETING CONTENT O
REVIEW ATWS RULE REQUIREMENTS REGARDING MANUFACTURING. DIVERSITY OF ANALOG TRIP UNITS 0
PRESENT RESULTS FROM EVALUATION OF SYSTEM LEVEL SENSITIVITY TO DIVERSITY FROM RELIABILITY VIEWPOINT 0
REVIEW HISTORY AND PHILOSOPHY OF DIVERSITY IN ATWS DESIGN 0
DESCRIBE EXISTING DIVERSITY PROVISIONS r
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MEETING OBJECTIVE 0
PROVIDE BASIS FOR CONCLUDING THAT MANUFACTURING DIVERSITY IS NOT NEEDED FOR ANALOG TRIP UNITS TO SATISFY THE DIVERSITY REQUIREMENTS T THE ATWS RULE 0
CLOSE OUT MNUFACTURING DIVERSITY ISSUE G
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ARI CONCEPT 0
PROVIDE DIVERSE R0D INSERTION 0
RECOGNIZE EXISTING DIVERSITY WITHIN RPS DIVERSE SENSORS FOR ALL ANTICIPATED TRANSIENTS ANALOG TRIP UNIT DIVERSITY 0
PROVIDE DIVERSITY FROM RPS WHERE MOST BENEFICIAL ARI PROVIDES DIVERSE R0D INSERTION i
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$821978 OENERAL PRINC!1 LES OF RELIABILITY ANALYala OF Table A7 Minimum Number of Like Functional Bloc's Required to Suffer Common Mode Failure to Prevent Autor satic Reactor Trip
_ _ _ _ _ _ _ _ - - - _ = _ _ _ _-
Number Numt te Transient Component Trata Affected Aethi Mode Overpressun Trip breaker, A and 3 2
2 Do not open circuit DC nlays A and 3 2
4 Do not open etreult AC relays A and 8 4
6 Do not open circuit Analog ehennels A and a 2
3 Do not nmove power to relay coil NOTE: A similar tabulation can be made for combinations of unlike co iponents.
I A3.8.1 Failure Com6(nattons. As with any Table A8 system failure, common mode failures arise Commor. Mode Failure Preventative Measures i
only when certain associated functions are
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not performed. If, for this example, one as-N"" C ** E 'Y P " #' N"" d" M'"""
sumes that the typical trip function shown in External n nmal Fig. l is the entire system, and that no others enwront ent runctional diversity act, a table can be made to summarize the sit.
Du),gn 'dmj aute T,troh op do, u
t,.
eontrots untion (Table A7).
sat. tailun mod.
A3.3.2 Causative Factors. Identification of g
dar on the important causative factors to be consid-Equipment diversity ered is the next step in the analysis. Five ren-D ign de aciency Functions! diversity eral categories of causes are identified in con.
Physical wperation i
nect. ion with common mode failure.
Design administratne controls operations) administrative controts (1) External NormalEnvironment:
safe calluso mode.
(a) Dust dirt Majnten nee Functional diversity (b) Temperature errors operational administrative controts (c) Humidity moisture Equipment dinrsity (d) Vibration Extuna cstast ophe Functional diversity (e) Electricalinterference r3y,;e,i.epar. tion (2) Design Dc/iciency Dairn administritive controts (a) Unrecognized interdependence be-pq','y,uQ tween "independent" subsystems, compo-Functi cal pents defie eney Functional diversity y
(b) Unrecognized electrical or mechanical Design administrerive controls 2
dependence on common element O P'" 'I "'I '.d *l"'i' ti" " 18 a
Equipnent diversity j
(c) Dependence on equipment or para.
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meters whose failure or abnormality causes j
need for protection (3) Operation and Maintenance Errors (a) Miscalibration (5' Functionaldeficiency (b) Inadequate or improper testing a) Misunderstanding of process variable I
(c) Outdated instructions or prints beh; vlor l
(d) Carelessness in maintenance
.b) Inadequacy of designed protective ac-(e) Other human factors tior (4) Erternal catastrophe (c) Inappropriate instrumentation (a) Tornado
/ 3.3.3 Preventative Measures. Redun-(b) Fire dai cy forms the principal Insurance against (c) Flood rar dom failures in that the probability of sev-(d) Earthquake ers i redundant components all failIng togeth-l l
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DIVERSITY BETWEEN RPS LOGIC AND ATWS LOGIC TYPE RPS LOGIC ATWS. LOGIC LOCATION OF L%IC RPS CABINETS ECCS CABINETS POWER SOURCE 115 VOLT AC 125 VOLT DC LOGIC CONTACTS DURING OPERATION CLOSED OPEN OUTPUT STATUS ENERGIZED DE-ENERGIZED e
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ANALOG TRIP UNIT MANUFACTURING DIVERSITY 0
MANUFACTURING DIVERSITY DOES NOT PROVIDE SIGNIFICANT IMPROVEMENT
- TRIP UNITS AVAILABLE FROM DIFFERENT MANUFACTURERS ARE SIMILAR IN DESIGN o-PROCESS TRANSMITTER INPUT o-MA OR V0LTS TRIP SETTING o-POWER SUPPLY
- MAJOR COMMON CAUSE FAILURE (MIS-CALIBRATION)
NOT SIGNIFICANTLY REDUCED o-CALIBRATION PROCEDURES NOT SIGNIFICANTLY DIVERSE
- ADDITIONAL COMPLEXITY IN PLANT PROCEDURES (TWO CALIBRATION PROCEDURES)
MANUFACTURING DIVERSITY NOT JUSTIFIED i
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FIGURE 4 RPS FAULT TREE WITH ARI, COMMON CAUSE FAILURE
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RODS (C)
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RPS ELECTRICAL
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RPS PCCHANICAL AND AR1 FAILS FAILURE OR AND
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gg g C(# TON CAUSE FAILURE RSS ELECT Ato ARI j
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b CCet04 CAUSE FAILURE RPS ELECT AFO AR!
( CC )
$ : 5.0 E-2 CM : 1.0 E-5 BETA : 2.0 E 1 CC : 0.4 E-5 RPS ELICTRICAL ARI IAIN FAILS
( CE )
( AR) )
4
A BRUNSWICK PRA RESULTS BASE CASE
.05 f%NUAL SCRAM
=
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COMMON ARl/,7.?S ANALOG TRIP UNITS
.05 MANUAL SCRAM
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0.2 (FROM NEDC - 30844)
BETA
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2.388 E - 05 CDF
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DIVERSE KANUFACTURER FOR ANALOG TRIP UNITS
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0,0 BETA
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f 2.367 E - 05 CDF
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CONC LUSIONS MANUFACTURIflG DIVERSITY lilPROVES CDF BY AT BEST ONLY 0.021 E - 05 4
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I C CNCLUSIONS ARI DIVERSITY TO THE RPS IS IN THE ATWS RULE AND IS ACHIEVED BY THE CURRENT DESIGNS r
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ENCLOSURE 2 4
MEETING ATTENDEES NRC BWR Owners' Group General Electric E. Adensam Terry Pickens (NSP)
Larry Gifford S. Newberry SteveFloyd(CP&L)
Bill Sullivan W. Hodges L. G. Byrves (GPC)
George Samstad J. Mauck Jeff Esterman V. Thomas (Sargent & Lundy)
E. Sylvester Jack Fulton R. Stevens (Boston Edison)
H. Li Sofia Toth (NYPA)
Pat Simpson (SERI)
E.Fotoponlos(Bechtel)
Richard January (Yankee Atomic)
LinTurner(TVA) j l
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