ML19329D632
| ML19329D632 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 07/07/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19329D626 | List: |
| References | |
| NUDOCS 8003160255 | |
| Download: ML19329D632 (2) | |
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i BRANCH TECHNICAL POSITION E!CS3 IB APPLICATICN.CF THE SIN 0' E FAILURE CRIit;"C'. TO.9 cat.LY.CONTRCLLC ELECTRICALLY CPIRAILO V:L'iES A.
BAC KC:C';NO Where a single failure in an electrical system can result in 1:ss of ca: ability to rerf:r.
a safety fun:tica.. tne ef fect 3" Plant so,fety cust be eval.ated, lhis is necessary regard-1ess of whetr.er the loss of safety function is caused y a c: ;arent fatiir.; tc ce'er a requisite rechanical motion, or ty a cer:cnent rcrfor-in; an untestrable aecner.ial :tien.
This position establishes tne a::e:tasility of discenec ting re.;ce to electrical :: :39ects of a fluid sysics as one reans of designin; against a single failure that ei;$t :evse an un-desirable c: ;:9ent acti:n. Trese :revist:ns are cased on the ass otton trat tre :: :ener.t is then equivalent 10 a si.ilar cc :: rent trat is n:t desiga.cd 'cr electrical :::rati:n.
e.g., a valve t=at can te c:ene: cr closce only of direct aar.ual c.eratto. of ttt.?l.e.
They are also Lased en tre assertion nat no sir.gle failure can ::t' restore t::.2-to tne electrical syst" and cause Pc:*.09ical rotion :.f tne c: ::nants ser.ed b ' !"0 ele:tei:al system. The validity of tnese ass' otions snosid 0: verified t +- a::lyin; **is ::si*ic't.
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Failurcs in t:.-
te ~f ail to functi:C scnw cn3 t*e "und: sir:ble ft, :tt:- se.se :f corpotents in cicetrical syste s ef sal. es a.d etner 'luid syste c: r-re.v. s ;.i:
be considered in etsi;nic; a;ainst a str;ie faihre. even to;h tne v *.se o :t er fluid systen co7 : rent ay c.:: te called u;:n to fe: tion in a gi.cn safn ::trati:nsi sequen c.
2.
Where it is deter-ined th:t failure of an electrical syste :: :: raat c!n :a.se undestred ee'thei:al :ticr. Of a valse or other fluid syste :: :: ent and ** 's rotien results in loss of inc sysic safety fu-:ti 9 it is 7:cc:tatic, in lic., Of design c. en;cs 193t also t a to a::c abic, to dis::.re:t ::..ec t tne electric syste s of the valvt or :tner fluid siste :: ::n:nt. Tec lant'te:t nical s:eci'icattens shoul:
include a list cf all elect-ically-::erated valves, and 'tec re:utred ::sitir s of these valves, to which the re:uirerent for re eval of electric p:..er is a:; lied in arcer to satisfy the single failure criterien.
3.
Electrica'.ly-cccrated valves that are classified as ' active" valves, i.e.. are re;uired to c?en or close in vario;5 safety sysic ::crati:nal se:sce:es. but are ranually-controlled, she,,1 te : erated fr:n the.ain centrol recr. Su:n valves may not te included a ng those s alves frc,.hien,0..er is re :ved in order to -eet i. e single failure criteri:n unless: (i) electrical re-er can de rest: red to the valves fr:n the main control re::.(o) valve c:eration is n:t necessary for at least ir. r.inutes k
following occurrence :( inc event requiring such c:cration, and (:) it is ce-~:nstrated 1
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,that t'here is reasonable as.urance that all necessary operator actions will te per-forred within the ti c shewn to be ace uate by the analysis. The plant technical specifications should include a list of the retuired positions of ranually-c:ntrolled.
electrically o:erated valves and should identify those valves to wnien the re:uire-sent for re eval of electric power is applied in order to satisfy the sic;1e f ailure criterien.
4.
n en the single failure criterien is satisfied by re eval of electrical :: ee frem valves described in G) and O), above, inese valves sr.:uld have redundant pestti:n indication in the t ain c:. trol room ar.c the position indication syste srcule.itself.
reet the single failure criterion.
5.
The phrase " electrically-o;erated alves" includes meth valves operated directly t..
an electrical device (e.g., a roter-crerated valve er a solenoid-operated salve) and tt:se valves crerated indirectly by an electrical cevice (e.g., an air-c:2 rated valse a sse air supply is c:ntro11cd by an electrical soleccic val.e).
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REfEAD.CES E
1.
Memrande to R. C. DeYoung and V. A. Peere from V. Stello. $cteder 1.1973.
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