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 I 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 l Unit 2 ATWS mitigation system TS changes. During this review, the staff concluded that Brunswick had installed the same type of analog transmitter and i
trip units (ATTU) for the ATWS/ARI system and the reactor trip system, which I 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 i their basis for concluding that hardware diversity is not needed to satisfy the i 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 )
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:
Central Files (k
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Contact:
H. Li (S SD/ DEST), x20781 ICSB RF !j P . !
NRC PDR SICB: DEST ST SIC EST L PDR t g HLi:bl 04//f/88
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/8[/88 SNe erry 04/f/88 S. Newberry J. Mauck / H. Li ,b k}'I ,
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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 1
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. ENCLOSURE I l l
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BWR OWNERS' GROUP /NRC MEETING ATWS ANALOG TRIP UNIT DIVERSITY l APRIL 7, 1988 ROCKVILLE, MD d
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MEETING CONTENT l
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 l
0 REVIEW HISTORY AND PHILOSOPHY OF DIVERSITY IN ATWS DESIGN 0 DESCRIBE EXISTING DIVERSITY PROVISIONS 1
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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 l I
0 CLOSE OUT MNUFACTURING DIVERSITY ISSUE l
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ARI CONCEPT l
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 l
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l ARI PROVIDES DIVERSE l R0D INSERTION i
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. s IEEE Btd
$821978 OENERAL PRINC!1 LES OF RELIABILITY ANALYala OF Table A7 Minimum Number of Like Functional Bloc's Required to l Suffer Common Mode Failure to Prevent Autor satic Reactor Trip l
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- _ __ _ _ __ _ l Number Numt te Transient Component Trata Affected Aethi Mode Overpressun Trip breaker, A and 3 2 2 Do not open circuit l 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.
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A3.8.1 Failure Com6(nattons. As with any Table A8 system failure, common mode failures arise Commor . Mode Failure Preventative Measures only when certain associated functions are - --
= = = - - -- - - - -- " -
i 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. aute Du),gn op 'dmj do, u t,. T,troh 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 Design administratne controls ;
nect. ion with common mode failure. 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 , l tween "independent" subsystems, compo-Functi cal y pents defie eney Functional diversity l (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. - - = - =_--s=-_- - - ---- =_- -=-_=_ --- _
- meters whose failure or abnormality causes l 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 64
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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 l o- PROCESS TRANSMITTER INPUT l o- MA OR V0LTS TRIP SETTING o- POWER SUPPLY I
- MAJOR COMMON CAUSE FAILURE (MIS-CALIBRATION)
NOT SIGNIFICANTLY REDUCED o- CALIBRATION PROCEDURES NOT SIGNIFICANTLY DIVERSE
- ADDITIONAL COMPLEXITY IN PLANT PROCEDURES (TWO CALIBRATION PROCEDURES) i MANUFACTURING DIVERSITY NOT JUSTIFIED 1 i
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FIGURE 4 RPS FAULT TREE WITH ARI, COMMON CAUSE FAILURE
& MANUAL SCR4M C: (((CE
- tii) + CM i FAILLRE TO INSERT SUFFICIDfT l RODS (C)
((CE
OR gg g C(# TON CAUSE FAILURE RSS ELECT Ato ARI j (CE
b CCet04 CAUSE FAILURE RPS ELECT AFO AR!
( CC )
$ : 5.0 E-2 CM : 1.0 E-5 - l BETA : 2.0 E 1 CC : 0.4 E-5
, RPS ELICTRICAL ARI IAIN FAILS
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A BRUNSWICK PRA RESULTS BASE CASE f%NUAL SCRAM = .05 NO ARI SYSTEM CDF = 2,496 E-05 COMMON ARl/,7.?S ANALOG TRIP UNITS MANUAL SCRAM = .05 BETA = 0.2 (FROM NEDC - 30844)
CDF = 2.388 E - 05 DIVERSE KANUFACTURER FOR ANALOG TRIP UNITS MANUAL SCRAM = .05 l BETA = 0,0 CDF = 2.367 E - 05 f CONC LUSIONS MANUFACTURIflG DIVERSITY lilPROVES CDF BY AT BEST ONLY 0.021 E - 05 l
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I C CNCLUSIONS I
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
1 MEETING ATTENDEES ,
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NRC BWR Owners' Group General Electric E. Adensam Terry Pickens (NSP) Larry Gifford S. Newberry SteveFloyd(CP&L) Bill Sullivan i 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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