ML19290D037
| ML19290D037 | |
| Person / Time | |
|---|---|
| Issue date: | 06/12/1975 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML19290C953 | List: |
| References | |
| 750114, ACRS-R-0725A, ACRS-R-725A, NUDOCS 8002150527 | |
| Download: ML19290D037 (15) | |
Text
-) V '
- 4 D
j EXCERPTS FROM PAST ACRS ffEETIflG MIfiUTES Af40 REPORTS RELEVAfiT TO THE "FIFTEEf1 TECHf4ICAL ISSUES" 1.
Treatment of ficn-Safety-Grade Ecuiernent in Evaluations of Postulated Steam Line Break Accicents Su: mary Raport, 151st ACRs Meeting Hecting Date:
November 9-11. 197*
MEETINC VITH THE DI2'*C* ORATE OF LICE!!SI??C Consacuences of Stea :line "atlure in theJ:xilisrv T.uildinas of the Prs ti to I.: land and.'irqit C.
Sum ar.su;:lesr ?lancs Mr. C. C. Long, DL, described for the Co :=ittee the '!SL pipinr.
layout relative to Auxiliary Suildia; design festurca, equipment locations and other ::.atters related to Stait/ Applicant investir,ation snd resolution or the steamlino break issue for these. reactor plants.
r In addition, the Committee developed and appreeed the following
. request to he transmitted to the Pc:tulatory Sta ff.
Steam Line Brenks and'Sinele.reilures The ACRS requests that they he ndvised in*a timely
~
manner of the number and identity of Was aircady in operation, which have received ACl3 operating license reports but are not yet l'icenaed, or which have received construction eermits, and which e.sy be subject to question with re: ard to adverse e f fects from stes:s line breaks or frcro loss of ECCS function under certain circumstances due to failure of a single, active ce=ponent#
- Also, e Cc=mittee : equesta that where operating ~
license reviews are in progress but not ce: pleted on such reactors, the Cc=nittee be given a preliminary technical evaluation of the stems lina break problem at the December /Cas reeting and an opportunity for further consideration prior to cecpletion of the Regulatorv processes le: ding j
to issuanca of such cperating licenses.
-l (This decision / request was transmitted by telecon, R. T. Fraley l
to E. G. Case, on November 13.)J
= - -.... -. _ _.
Dresden 2. "ovember 24 1955
" Chile the isolation valves and fittings in the hish pressure secan lines frc=
t*ne reactor to the turbine are being designed carefully, the Ce.ittee reec.= ends th:t special a::entica be given to insure that no single rupture can. lend to sequential failure and loss of contain=ent."
Virril C. Summer. r!nt: 1. i*ovember 15. In72 - C?
She: aron ila rric. Uni t s 1 - i.. Janu rv 17 19 7 3 - c 2
~
The applicant has proposed criteria for =eans to =iciga:e safc:y-related consequences of a possibic =ain stec= line or feede :er line rup:ure out-side the con:ainment buildihg.
This =at:cr should be rcsolved in a conner satisfactory ec the Regulatory Staff; the Cocti::ce vi:hes :o be kep: in-for=cd.
s North Anna. Unt:s 3 and 4. March 13. 1973 - Cp The applicant has under study.=ecas to citign:e the consequencas of passi-ble rupture of the =:in scca: lines cnd feedvs:e lines on: side the cca-tainment building.
This =t:ter should be resoieci :o the sa:isfae:icn of the Regulatory Staff; the Cc==it:ee uishes to be kep: infor=cd.
Prairie Island. Units 1 and 2. Aoril 15. 1973 - CL The Co==ittee considered the proble= of the unlikely.rup:ure cf a high
' cr:crgy piping line ou: side o f
- contain=en:.
The cpplictn: der ribed an valuation, carried.ou: in s cordance vi:5 cri:cris es:cblir;.ed by the
.cgulatory St:ff. Ocsign modifica:icns including enespsu'a:icn sleeves, equip =en: protec:icn, equipnent reicca:icn, equip =an: -qualifiestica and i=pingc=ent berriers are under considcrecien.
The C:==i::ec rc=== ends that the final design an'd installation =ee: t,he require =en:s of the 2cguia-cory Staff.
~
Coooer. Unit 1. Anril.IS. 1873 - OL 11s t e h, Unit 1, June 12, 1973 - OL The applicant has exc=ined the prebic=s :hs: =igh: de.elop should a =ain ste== line or feeducier line rupture cu: side of cen::in=en: and has cen-cluded : hat the pisn.: could be shut dew: c 'ely.
The Ec.;-i.:icry S:sif ic reviewing the appliennt 's sub=it:al.
The Ceamit:ce rec:==end: :hs; this
=atter be resolved in a =anner sati:iac:Org to :he heaul::ory S:aff.
g 6
sse g@2@2b
2.
Lack of Indeoendence of Interlocks on ECCS Valves L. Manning Muntaing.,-
The Cocm11ttee suggests that further atten' tion.be given to ques tions which arise in conneccion with procedures involving physically logking out electrical sources to specific motor-operated valves required in the engineered safety functicas of ECCS systems, based on the assumption that a spurious electric s'ignal at an incpportune ti=e could actuate the valves to the adverse position; e.g.,
closed rather than epened, er cpened rader than closed. ' E.tamples where this procedure is being applied include Ycijan, Salem, and Seaver, Valley.
The ACRS believes that the catter should be studied using a system appecach, both for existing and for future plar.ts.
Examples of suggested questiens to be answered include:
~(1) An evaluation of the probability of a spurious signal; (2) Can the valve. operator be reactivated in a reasonable time af ter indication of loss of electric pcwcr; (3) If the circuit b'reaker is opened, are signal _ lights lost; (4)
If the signdl' lights are deactivated, is it possible to reactivate them through bypass circuits, etc. ;.
(5)
Is it possibic to lock a valve out in the apparently open position whereas it actually is closed since one depeads on indicator position; (6) Cases are documented where valve stems have brokca leaving the gate in the closed positicn; is the indicator such dat the lights indicate an cpen valvc chile it is actually closed (a) Is there a positive testing peccess applicable on a routino basis to establish tht.t the critical valrcs are indeed ccrrectly aligned, permitting a flow path; (b) -If no testing process exists,. can one u!J non-destructive examination techniques to unequivocally Locate the gate position (7) NouldamorereliableECCSsystemresult if fewer motor-eperated valves, more check valves, and core parallel paths were used; what other facters influence the choice of alternate designs; (8) What are the pros and cons of a~ system where an incorrect acci'on can be rapidly reversed by an alert cperator cec pared to a system where electric power is locked out, but ene or more valves are incorrectly aligned requiring the operator to go scee distance in a very short ti=e to reactivate the circuit breakers.
..s u\\
O
Toseeh M. Farlev: 2652 M'le :
OL:
6/12/75 The NRC Staff has proposed that electrical pcuer be nor: ally disconnected fres certain =ocor-operated feedwater valves required for e=ergency core cooling operations in order to prevent a single failure in the electrical syttes f rom disabling a part of an essential safety system.
The applicant has argued that a spurious repositioning of these valves is highly improbable and that locking out pcwer to these valves will not lead to greater safety.
The Co-4 tree belieses that a eceplete syste=s analysis.of this generic probles has not been =ade which takes account of all possible failures, both elettrical and =echanical, for these valves in both the 1cck'ed-cut and nor-
=al configurations. Additional studies of possible alternatives are being made by the Applicant and shot.ld be evaluated before this c:acter is resolved.
The Coc=ittee. wishes to be kept infor=ed.
IIC IDC1GG CUT CF ECCS KFdR-GERA*ED VAINES Se physical locking out of electrical sources to specific cotor-operated valves required in the engineered safety functicns of ECCS has been required, based on the a m tion that a spurious electrical signal at an iropportune tim could activate the valves to the adverse position; e.g., closed rather than cpen, or opened rather than closed. hhile strh an went'has a finite probability another probability exists that the valves might be adversely psitioned due to operator error.
~
,e Se A3S believes the mattir should be sttdied using a systers approach, and considering such itets as (1) the evaluatica of the probability of a t
spurious signal; (2) tim required to reactivate the valve operator; (3)
' status of signal lights when the ciruit breaker is open; (4) can the valve
,t be locked out in an impreper psiticx1 due to a faulty indicator; (5) are I
I there other designs i= proving reliability without lock-out; (6) what are the advantages and disadvantages of corrective action by an alert cperator in case of incorrect psitioning vis-a-vis a systm with pwr locked out.
3.
Acceptability of Swing Bus Design of BWR-4 Plants Honorable Glenn T. Seaborg May 15, 1958 The e=ergency power syste= originally provided for Units 1 and 2 has been redesigned and expanded to serve all three units.
Four diesel-generators are now incorporated instead of three.
The design as pro-posed appears =arginally acceptable. Questions arise regarding the capacity of the diesel-generators and regarding the necessity for Parallcling of generators at so=e ti=e after an accident.
Considera-tion should be given to i= prove =ent of the syste=.
The Co==ittee
. believes that.these improve =ents should be resolved between the applicant and the Regulatory Staff.
Browns Ferry, 3/14/67 "The. diesel-generator sets for e=crgency power appear to be fully loaded with little or no margin (on the design basis of one of three failing to start).
They are required to start, synchronize, and carry load within less than thirty seccnds.
The applicant stated that tests vill be conducted by the diesel =anufacturer to de=enstrate capability of =eeting these re-quire =ents.
Any previously untried features, such as the cethod of syn-chroniration, will be inclu~ded in the tests.
The results should be evaluated carefully.by the AEC Regulatory Staff..In addition, ti.e installed e=ergency generating system should be tested thoroughly under simulated c=ergency con-dicions prior to a request for an operating license".
Brown's Ferry, Unies 1-4, 9/21/72 - OL Four diesel-generator sets have been provided for energency power.
Originally, the applicant planned to have these sets serve all three units of the plant. However, in order to reduce diesel-generator loadings, lessen the extensive interrelationship a=ong the units' control circuits, ano reduce the required a=ount of operator coordination, he recently pro-posed a =odification which provides for sharing of these sets be' tween Units 1 and 2 only, with four additional diesel-generator sets to be provided at a later date for Unit 3.
The final design details of the proposed codifi-cation vill not beco=e available for several =enths.
The Co==ittee believes that the codified arrange =ent, which involves negligible change in Unit 1, is satisfactory for Unit 1 operation. After submittal of the system design details, review of the adequacy of the =odificatica in regard to operation of Units 2 and 3 vill be =ade by the F.cgulatory Staff and the Cc~~4 ttee.
~
Honorable Dixy Lee Ray '
ggg g g gg The e:ergency power systen originally proposed has been substantially modified and i= proved.
The changes were =ade pri=arily to assure adequate power capacity, lessen interactions between the units, and reduce the a=ount of operator coordination required.
In the revised design, four diesel-generator sets are shared between Units 1 and 2 and four additional, si=ilar sets are provided to serve Unit 3 vith capability for =anual paralleling with the first four sets for long ters operation. The co=mittee believes this'= edification to be satisfactory.
s The on-site emergency power supply for Unit No. 3 e= ploys four 4'80 V buses energized (upon loss of nor=al pover) by three dies 21 generators, two of which are required to furnish energy to engineered safety fea-l tures., Die applicant proposes an auto =stic ' system of cross-connecting sources and loads. The Ccemittee beli~ eves that the on-site power i
sources should have a greater independence than in the proposed syste=,
8 at least to the extent that they cannot be connected together.vich auto-
=atically operated devices. An appropriate =odification should be de-veloped by the applicant and the =atter resolved with the Regulatory Staff.
I The applicant stated that the control syste=s for e=ergency power will be designed and tested in accordance with standards for reactor protec-tion syste=s. Also, he will explore further possibilities for improve-
}
aent, particularly by diversification, of the instrucentation that initiates emergency core cooling, to provide additional assurance against delay of this vital function.
I The Coc=ittee reco== ends that the applicant give further consideration to the design of the e=ergency cr-site power system with regard to the need for synchronization of the diesel-driven generators. The Co==it-tec also reco==cnds that rigorous, realistic preoperational and in-service testing. progra=s be undertaken on the diesel system which is adopted. The Cc==ittee wishes to be kept infor=cd on the results of I
these considerations.
e
4.
Loss of Offsite Power Subsequent to Manual Safety Iniection
~
Reset Following a LOCA ACRS Meeting Minutes May 9-11, 1968 E.
On-Site Electrical Pouer The Coc:mittee.has expressed its concern with the oa-site electrical power systems that require paralleling diesel-driven generators. The paralleling action provides an opportunity for improper operation and the, j
at least, te=porary loss of part or. all' of the on-site electrical power most when tha it is/needed. The Coemittee does not object to paralleling opera-tion of diesel-driven generators some time ~ well after the initial criticci had period sad. after most of the emergency loads have been ps 29 M up and A
when the loss of a diesel-driven generator would not endanger the cere.
The Coc:mittee believes that ceneral Design Criterion No. 39 needs
%M clarification in this 4esca.r..
,1 In su= mary, the Co=mittee has expressed its concern with on-site electrical power systems that require synchronization of diesel-driven generators (ACRS report on Cooper Nuclear Station dated March 12, 1968).
l In addition, DEL h.as indicated that parralleling of e=ergency diesels t
l appears to violate the requirement of ceneral Design Criterion No. 39 for
. independent emergency power systems.
During this meeting, the 'Coemittee concluded (in connection with BroEs Ferry No. 3) that synchronization and Paralleling of diesel-driven generators may be accepted under so=e condi-
, tions (e.g., when the need for emergency power is not " critical" and the probability of other powe'r sources or the probability that a specific ccmbination of loads is not '11kely to develop). It was agreed that addi-tional discussion with DRL is required t'o clarify this issue.
Dr. Zabel is to inform Dr. Morris that the Ccemittee desires to discuss this matter at the June ACRS c:eeting.
sinut s of 168th ACRS Meeting Mccting Date: April I-1-13,1974 D.
Perrm anea of r.
rcer.cs-nionels.
T. R. Ullson described and discussed an US study of the reli.tbility of cr rgency dicsc1 gen:rstor sets used in nuclear power plants. All op.:rsting plants were revicued (ence. t humooldt and Occace witich do not use diescis). The n
study shovud that cast recorded failures occurred during periorm:nce testinc., not tehile on load. The reliability, while probably opti=istic, is shcrn to be.99 uith a 50%.
confidence Icvol. Except for the Cooper-Sessener machines at Ziun, the reliability of.the nachinos manufactured by diffe. rant vendors has been very similar. The larg.:r units have a very slightly hir.her fcilurc rate than intermediate-size units. Most failurcs v:re caused in starting circuits or auniliary systems. There h:ve teen no f iluren affecting the r21 esse of r:dicactivity.
So=a licence,cs are taking positive corrective ections.
?
' Revised: 1/20/70 5
Su= mary, llSch ACRS Meccias. 11/20/69 l
3 Encreenev DEesci and Offsite Power Reliabilf tv a.
Diesel - The Cc==ittee decided that a review is required of the reli:bility of escrgency dicscl generstors, including an investigs-r tion of hou =uch the utilicies have to rely on the diesels for emergency power support. The Chcirman was authori:cd to assign a Subcommittec'to review this subject.
(Dr. Hansuer h:s assigned this review to the Subec==ittee on Electrical Systa=s, Centrol, and I'nst:a=entation.)
b.
Offsite Power - The Coc=ittes decided to ask the Regulatory Staff to consider a genersi appro:ch for technical specifiestions of licensed reacto:
owners (oneratars) uith respect to:
(11 s di=inution of nor=al off-site power capability,cnd (2) a threat to offsite power cap:bility.
(Dr. Morris has been advis d of this Cc==ittee request.)
,a
Meeting Date:
April 5, 1972 CODES. STANDARDS AND CRI VRIA St*3CC:'MITTEE PIETINC
.17I7 H Street, Wesk.. D.C.
Acril 5, 1972 ATTENDEES ACRS DRS H. Etherington G. Arlotto H. G. Mangelsdorf V. Moore N. J. Palladino
' W. Burns (Staff)
RtMia_RY The Subce=:ittee reviewed the chronologv o'f the deveico=ent of General Design Criterion 17 from 1967 (designated Criterion 39) to the present with benefit of discussion with Messrs. Arlotto and Moore. The purpose of the review vas to establish that the Regulatory interpretation of and bases for Design Cri-terion 17 are sufficiently in accord with the viewpoint of the ACRS to ensure that i.ts application will result in no undue mk to the public healthfand safety.
n.
The following' infor=ation was provided to the Subco=mittee:
Offsite power availability is the third' level of protection-in-e depth against the potential of an unacceptable event caused by failure of onsite c=ergency diesels to start.
e Thermal circulation of primary coolant, in co=~oi=ation with steam-driven feed-water pu=ps would nor ally allow sufficient time for re-estab1Lhing an adequate supply of electric power.
All PWR's, except Sequoyah, have stea=-driven TJ pc ps.
Sece e
BWR's do not have steam-driven E*J purps.
I Although the conponents of the steam drive syste':s are not of e
en eineered safety feature grade, they h' ave a record of high I
reliability.
j The ACRS previously accepted the concept of en extended outage e
of of fsite power in lieu of automatic switching to an alternate system to re-establish power (Forr Calhoun).
l The probability of failure (per hour) of the grid is at least-e one order of magnitude greater than the probability of failure (per hour) of a transmission line connecting r.pl.snt to a grid.
D
Meeting Date:
April 5, 1972 A recent utility analysis of the reliability of power grids e
(based on 28 rcactor-years)has disclosed a power outage proba-bility of-G.S x 10 This is within the range used by the Staff as a basis for the requirements of Design Criterion 17.
Based on the foregoing, the gain in offsite power avail' ability e
attributable to first order redundancy in connecting lines between the plant and the distribution grid is at most a factor of two or three. Thus, the added cost of radundancy becomes l
. difficult to justify (free. the utility point of view).
l In discussion related to the power outage prob 0bilitics and relative relia-bilities of power distribution grids and connec :ing lines to the plants, Dean Palladino pointed out that if the reliabil. ties should be found to be reversed (for s,ome installations) there would be ample justification for ccmpletely separate, redundant transmission lines.
He also mentioned that it 'had always, been his position. that the towers carrying the redundant lines should be far enough apart to preclude a common-mode failure event. Mr.
Etherington pointed out that it would be desirable to have firmer data on failure probabilities for support of DC-17, as for most of the reactor safety matters of' concern to the i. ORS, and that the duration 'of cutages should be taken into account as well as their frequency. Messrs. Moore and Arlotto concurred with these obr rvations, but indicated that the old Criterion 39 didn't require indeoendcat transmission paths; that it made no distinction between grid and line reliabilities; that good information on power grids was difficult to obtain; and that the Staff did factor in the outage ti=e in developing probability i.tlor=ation from total cutage ti=c *- total time.
Mr. Moore reviewed 'for the Subco==ittee t'he nature and sourres of data and information used by the Staff' in 1969 as bases for the development of the requirements of DC-17, and he agreed to provide the Subco==ittee with this record information for study in advance of the 144th ACRS meeting.
In Executive Session, Dean Palladino suggested that the full Committee should be advised that his opinion and recom=cndation would depend upon the ouceo=e of his review of the Staff's reliability bases for DC-17.
1
)\\
6 9 \\\\ QT e
4.....em-i-e.
5.
Analvsis of Pontulated Reactor Coolant Pumo Rotor Seizure Incidents
~
Point Be ch 1, Ma> 16.1967 and Point Bench 2. !!av 15,1968 "The applicant is performing a detail ~ed analysis of the ef fects of sudden failurc (e.g., by seizure) of a main coolant pump, particularly in respect to the minimum departure-from-nucleate-boiling ratio reached in the core.
The Regulatory Staff should continue to review this work."
Indian Point 3. J..n 15.19'i9 and Calvert Cliffs 1 & 2. March 13,1969 "The main-coolant-pump flywheels represent a potential source of missiles within the containnent. ar.d the applicant has described easures taken to assure censervative design and high quality fabrication to minimize the possibility of flywheel faildre. Additional steps cay be warranted to ascure the integrity of the flywhcci assembly, :nd the Cer.mittee rccer. mends that details concerning the adequacy of design, the catorial characteristics, quality assurance, and in-service insoection requirements be resolved between the applicant ahd the Regulatory Staff."
't l!.
i t
i
'I h
$p ~%fd i
i s
6.
Protection Against Single Failures in Reactivity Control Systems Allens Creek-1/2; 3579' P!(t): CP; 12/12/74 Perrr-1/2: 3579 i Ut): C?: 17/12/74 River tend-1/ 2 : 2 W14 'T.H t ) ; CP: 1/14/75 A recent publication (Sce Reference 11) suggests a need for the use of three-dicensional calculations to correctly predict peak flux and temperature distributions for super-proep:-critical excursions.
This may be relevan: to analysis of the rod-drop acwident, and both Cencral Electric and the Regulatory Staff have initiated work to clarify the situation. This ca::cr should be. resolved in a =anner satisfactory to the Regulatory S_taf f.
The Co==ictce wishes to be kept infor ed.
Fitznatrick. Unit 1. 12/15/72.- OL Analyses of postulated control.od drop acciden:s have been revised by the applicants to ecploy a core. realistic rate of reac:ivity 'nsertion than for:erly assu ed, and to accoun: for chan;es sde in core design, in the use of a number of fuel enrich =ents, and e=picy=ent of full-and par -
length gadolinia' bearing fuel rods.
These analyses indicate that, for postulated accidents dur,ing certain portions 'of :he fuel cycle, the results are unacceptable.
The applicants have proposed a rod secuance control syte= which is intended to render the probabili:y of occurrence of such an accident negligibly lcv.
This =at:er is under review and shculd be resolved in a canner satisfactory to the Regulatory Staff and the Cot =it:ee.
Approved measures should be placed into effect prior to operation abova 1%
of rated power.
Susquehanna. Units 1 & 2, 4/13/72 - CP The techniques for analysis of the control rod drop. accident are being revised by the Cencral Electric Company.
The adequacy of the revised model and the acceptability of the results s'suld be established in a manner satisfactory to the Regulatory Staf f.
The Co=mittee wishes to bc kept informed of the resolution of this matter.
Hanford, Unit 2, 9/19/72 - CP -
Analyscs of postulated control-rod drop accidents occurring in si=ilar cores during certain portions of the fuel cycle indicate unacceptable results.
Studies of provisions to reduce the probability of this accident to negligible levels are undcrusy. This =c::er should be resolved in a =anner satisfactory to the Regulatory Staff prior to completion of construction.
6 U" QS \\
' va D $;08d9g $u ej b
e
Monticello. Unit 1, 9/19/72 - OL An'alyses of postulated control-rod drop accidents have been revised by the applicant to employ a more realistic ra:e of reac:ivity inser: ion than formerly assu=ed. These analyses indicate that, for accidents occurring during certain operations and certain portions of the fuel cycle, the results cay be unacceptable.
The applican: has preposed interim procedures which the Cocaittee believes to be satisfactory.
The final resolution sh'culd be cade in a canner satisfactory to the Regulatory Staff.
~
Brown's Ferrv. Units 1-4. 9/21/72 - OL Peach Bottom, Units 2 & 3. 9/21/72 - OL Analyses of postulated control rod drop accidents recently have been revised by the applicant to employ a more realistic rate of reactivity insertion than for=erly assu=ed, and to account for the changes made in the core design, in particular the use of a number of fuel enrichments and e=ployment of full and part-length gadolinia bearing fuel rods.
These analyses indicate that, for accidents occurring during certain portions of the fuel cycle ~,.the results are unacceptable.
The applicant has pro-posed possible changes in plant design or operating procedures which he -
believes would render the probability of occurrence of such an accident negligibly lov. The general approach appears feasible; however, details.
of the proposal are not yet available and will require thorough evaluation af cr submittal. This matter should be ress ved in a manner satisfactory to the Regulatory Staff and the Committoc.
Approved measurcs should be placed into effect prior to operation above 1% of rated power.
Browns Ferr7-2/3: 3293 MNt: OL:
12/11/73 Revised analyses of postulated control' red drop accidents which takes into account the changes =ade in core design and which utilize recent es-ti= aces of rate of rea::ivity inser:1cn, indicate that, for such accidents occurring during certain par:s of the fuel cycle, the results would be unacceptable; i.e., the peak fuel enthalpy resul:ing in se e fuel rods vould exceed 280 calories per gra=.
In view of this, the applicant pro-poses to install a Red Sequence Control Sys:e= (RSCS) which he believes will render the probabili:y of occurrence of such an accident adequately lov.
Browns Ferrv-2/3: 3293 MR:: OL:
12/11/73 The proposed RSCS is a hard-wired syste= designed to ' * -ad cove ent sequences so as to preclude establish =ent of single-red reae:ivi:y wor:hs capable of generating excessive peak fuel enthalpy.
The Cc--d::ee finds this provisien. satisfac:ory.
Brunswick'-1/2: 2436 MNt: OL:
12/11/73'
~
To 11=1: :he causequences of a : d d: p accident the applican: plans to' install a Rod Sequence Control Sys:e= (RSCS) which vill include a group notch control feature.
The f' nctional adecuacy of :he installed a::ange should u
be verified by the Regulatory Staff pri N, s
Duane Arnold Unit 1, 3/13/73 - OL The applicant is cc--deted to the insta11stien of a red sequence centrol syste= which will render the probability of cecurrence of a pcstulated, high-vorth control rod drop accident negligibly Icu.
This =atter is under review and should be resolved in a =anner satisfactoty to the Fagiatori Staff-Approved =easures should be placed in effect prior to operatica above l'.' of rated power.
Midland Units 1 & 2, 6/18/70 and Trojan Unit 1, 7/17/70 "The Co -4 tree recc== ends that the appliesnt accelerate the study of
=eans of preventing ec on failure =ades fro = negating sers= act:ca and of design features to =ske tolerable the conseg,uences of failure to scra= during anticipated transients.
The applicant stated that the engineering design would =sintain flexibility with regard to relief capacity of the pri=ary i
systc=.and to a diverse =eans of reducing reactivity.
This =atter should be resolved in s =2nner satisfactori to the Regulatory Staff during construction.
The Cor *teee wishes to be kept informed."
i i
i Ver=ent Yankee Nuclear Pover Station, 3/9/71
' i.
'{
"The applicant is ceni:inuing to study further =eans of preventing co==on = ode f ailures fro = negating reactor scra= action, and of design features to =ake tolerable the consequences of f ailure to scrs= during i
anticipated transients.
The Co-d etee believes it desirable to expedite i
these studies and to i=ple=ent in ti=ely fashicn such design =odif.ications
.i as are found to i= prove significantly the safety of the plant in this regard.
.I The Co-d etem.rishes to be kept infor=ed of the resolution of this =atter."
l h
7.
Passive Failures Following a Loss of Coolant Accident Summary Report, 152nd ACRS Meeting Meeting Date:
Dec e=be r 7-9, 1972 Pipe Whio -- Rastraints are provided where feasible. At 21even locations where insufficient space was available for installation of restraints, protection of critical features will be provicad by impingement plates or increased surveillance.
i ECCS Eeuipment Room Floodini -- Watertight partitions are to be used for protection of critical cocponents.
Virr!1 C. Summer, Unit 1, rovember 15, 1972 - CP Shenron liarris, Unita 14, Januarv 17. 1973.- c3 The applicant has proposed criteria for meano to mitiqate safety-related consequences of a possibic cain secam line or feed:.acer if ne rupture out-side the containment building.
This matter should be resolved in a manner satisfactory to the Regulatory Staff; the Cocatttee wiches to ba kept in-formed.
North Anna. Units 3 and 4 M.irch 13, 1973 - CP The applicant has under study means to mitigate the consequei.ces of possi-tic rupture of the main secan lines and feeduater lines cutside the con-l tainment buil' ding.
This matter should be resolved to the satisfaction of the Regulatory Staff; the Committee wishes to be kept informed.
Prairic Islan'd, t'nita 1 and 2, Aoril IS, 1973 - CL ihe Cc=mittee considered the probica of the unlikely rupture of a.high cricrgy piping line outside of contain=ent.
The applic nt dercribed an evaluation, carried out in accordance with criteria ccrablished by the
'egule,cory Staff. Design modifications including encapsulation sleeves, uip=ent protection, equipnent relcention, equip: cat qualification and apingement barriers are unoer consideration.
The Cc==ittee recor= ends that the final design and installation ucet the require =ents of the Regula-
_ tor 1 5taff.,___,
_Coor.
. Unit i _Anril 18, 1973 - OL t
lla tcl Unit 1.
1une 12, 197.) - OL The applicant has examined the problocs that might develop should a main steam line or feeduater line rupture outside.of containment and has con-cluded that the plant could be shut down safely.
7.*ic Regulatory Staff is review'ing the applicano's submittal.
The Cc==1ttee recc==cnds that this matter be resolved in a manner satisfactory to the Regulatory Staff.
b D