ML17214A454
| ML17214A454 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 03/02/1983 |
| From: | Held J ENERGY, INC., LAWRENCE LIVERMORE NATIONAL LABORATORY |
| To: | Alberthal G NRC |
| Shared Package | |
| ML17214A453 | List: |
| References | |
| CON-FIN-A-0250, CON-FIN-A-250, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM TAC-44404, TF-355-0812A, TF-355-812A, NUDOCS 8309270650 | |
| Download: ML17214A454 (7) | |
Text
Selected Operating Reactor Issues Program II Reactor Coolant System Yents (HUREG-00737, Item II.B.1. )
HRC F'-N A9250 - Project 9
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Tt'"HHICAL EYALL'ATi0's 7:-oORT FOR ST. Ll:" 1 Docket Number 50-335 HRC TAC Number 44404 Prepared by J. T. Held of Energy. Incorporated - Seattle (Subcontract 4324401) for Lawrence Livermore National Laboratory under contract to the HRC Office of Nuclear Reactor Regulation, Division ef Licensing.
0 HRC Lead Engineer - Gus Alberthal HOTICE "Tnis report was prepared as an account of work sponsored by the United States Government.
Neither the United States nor the United States D partment of Energy, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness'of any information, apparatus, product or process disclosed, or represents that its use would not.
infringe privately-owned rights."
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NRC TAC Number 44404 TECHMCAL EVALUATIONREPORT ON REACTOR COOLANT SYSTEM VENTS FOR ST. LUCK I INT..ODUCTION The requi.emen".s for rea"tor cr!an s stem hick pain'.
ven'.s are ~cted in por""rc)h (cX3Xiii) of IO Cr R 30.44 "Standards for Comb.'stib!e G~m Control System in L'&'afer Cooled Power Reoctors," and are further described in Standard Review Plan (SRP)
Section 5.4.12, "Reoctor Coolant System High Point Vents,"
ond Ifem II.B. I of NUREG-0737, "Clarification of TMI Acfion Plan Requirements'n response to these and previous requirements, the Florida Power 6 Light Company has submitted information in References I and 2 in support of the vent system at St. Lucie Unti I.
EVALUATION The functiori of the high point vent system is to vent noncondehsib!e qoses from the high points of the reoctor coolant system (RCS) fo assure fhat core cooling during natural circulation will not be inhibited.
The St. 'Lucie I reactor coolant gas vent system.
(RCGVS) provides venting capability from the reoctor vessel head and the pressurizer steom spoce.
The noncondensible
- gases, steam, and/or liquids vented from the reocfor vessel head and pressurizer steam space ore piped and dischorged to either the.
containment atmosphere or the pressurizer quench tcnk.
The RCGVS is designed to vent one holf of the RCS volume of hydrogen in standard cubic feet in one hour.
Flow restricfion orifices in the RCGVS paths, however, limit mass loss from a vent pipe break or inadvertent octuation of the RCGVS to. less than the makeup capacity of a single charging pump.
- Hence, the licensee's cornplionce with IO CFR 50.46, "Acceptonce Criteria for-Emergency Core Cooling Systems for Licht Water Nuclear Power Reoctors,"
hos not been affected by the oddition of the RCGVS.
The vent paths from the reactor vessel heod and the pressurizer each contain two independently powered solenoid-operoted valves in parolle! and connect to a common heoder that,dischorges either to the contoinment atmosphere or to the quench tonk
~m/TER-P-24 Enclosure 6
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- hrough on of two isolation volves in parollel that are also powered from diverse power sources.
Thus, a degree of redundancy has been provided by powering RCGVS valves from different emergency power supplies<.to ensure that RCS venting capability from both the reoctor vessel heod ond the pressurizer is maintained.
Volve control switches and valve position indication, ocfivated by reed switch assemblies on the solenoids, are provided in fhe moin control room.
RCGVS vaive seat leakoao is detected by pressu're jnstrumenta',ion v'ith associa; d
ola. ms in th rnoin control room indicafina a
leok
- hrouch one of 1h prirnc-.y RCG"S volv s.
A solenoid valve can then b op ned onC th fo cn;,=uwuI~ "r and eventuolly crcin d to th cradu"ted cvntoinrn r;t u;.,p t" L mecsar The portion of each RCGVS path up to and including the second normally closed valve forms a part of fhe reoctor coolant pressure boundary ond fhus must meet reoctor coolant pressure boundary requirements.
The licensee has stated that this portion of the RCGVS is designated Safety Class 2 (Safety Class I upsfream of the flow restriction orifices) and Seismic Category I in compliance with IO CFR 50.55a and Regulatory Guides 1.26 ond 1.29.
The
= RCGVS is designed for pressures and temperatures corresponding to the RCS design pressure ond femperature.
In addition, the vent system materiols ore austenitic sfainless
- steel, are compatible with the reactor coolant chemistry, and were fabricated ond fested in occordonce with the requirements of Section III of the ACME Boiler and Pressure Vessel Code.
The RCGVS is also occeptably separated and protecfed from missiles and the dynamic effects of postulated piping ruptures.
We therefore conclude that the design of the porfions of the RCGVS up to ond including the second normally closed valve conforms to all reactor coolant pressure boundary requirements, including IO CFR 50.55o and the applicable portions of General Design Criteria I, 2, 4, I4, 30, and 3l.
The licensee has further ascertained that the essential operotion of other safety-related systems will not be impaired by postulated failures of RCGVS components.
We hove reviewed the licensee's RCGVS design to assure on occeptably low probability exists for inodvertent or irreversible octuation of the vent system.
Each vent path hos two solenoid-operoted pilot valves in series, ond eoch valve has o separate key locked control switch.
Power is removed from the valves during normal reoctor operation, with odministrative controls for reconnection when venting is required.
The volves are powered by emergency power supplies ond fail to the closed position in the event of loss of power.
The, licensee has stoted that the controls and displays odded fo the main
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control room for the v n', system are beino considered in a human factors analysis conducted in occordonc with NUREG-0737 in order to reduce the potential for operator error.
However, recent tests of the RCGVS at St. Lucie I hove shown that operation of one solenoid-operated v'alve may cause other solenoidmperated valves in the system to op n temporarily.
It vm recommended in Reference 3 that plants with these solenoid-operated valves evaluate their vent systems and present their conclusi'ons including ~y c sign changes pessary to minimize the probability of m inodverten'.
ven, system actuation. 5'h rebore find that no sinale oc.ive component failure or humean e;ro-. s'rculd r su'2 in irndverient op n!ng or irrev.-sible opora'.ion (i.e. foilu.e to c':>~
aftor i"..en.'ional o>es',r:
) o; the RCGVS, "ontino nt on c satisfactory evaluatic;<
Ref rene Z.
I-~w ve.-, from tr.
o sign info. notion submitted by th licensee it is no? clear whether RCGVS valve position indication is depenoent on control power.
Depending on the configuration of valve control and position indication power, removing power from the valves as descriid above may result in loss of positive valve position indication during normal reoctor operation.
Until it is ensured'hat direct position indication is continuously provided, this is a confirmatory item.
We have also examined the locations where the RCGVS discharges to the containment atmosphere directly or'through the rupture disk on the pressurizer quencCi tonk. BoseB on a description provided by the licensee (Reference 2), these locations are in areas that will piovide good mixing with the containment atmosphere to prevent the accumulation or pocketing of high concentrations of hydrogen.
in compliance with IO CFR50.44, "Standards for Combustible Gas Control System in Light Water Cooled Power Reactors."
Additionally, these locations are such that the operation of safety-related systems would not be odversely affected by the 'discharge of the anticipated mixtures of
- steom, liquids, and noncondensible gases.
The licensee has stated that the potential discharge paths through the leakage detection occumulator to the containment pur'ge.
ducting and the drains to the reoctor cavity sump are intended to be used only during normal plant startup and shutdown, or for periodic drainage.
The licensee has stoted that the solenoid-operated volves will be tested for operability durinq cold shutdown in accordance with subsection IWV of Section Xl of the ASME Code.
2m/TE R ~D-2A Enclosure 6
CONCLUS!04!
V>e conclude that the 't.
Lucie I ';RCGVS design is sufficient to effectively vent noncondensible gases from the reactor'coolant system without leading to an unocc ptable increase in the probability of a LOCA or a challenge to containment integrity, m ts the oesign requirements of NUPEC-0737 Item!I.B.I, ond conforms to the reauirer;.ents of paragraph (cX3),'iii) of I0 CcR 50.44.
Se th reiore recommend
- tha, t'he St. Lucie I
RCGVS desicn be fou~~ occep:cbl wi h th follov:ing two coniirr.atory I>
." >e.">0 i-p
~ ate
. valves in th>e RCGVS mus b
evaluated pe! Re
> er n e 3 Tn
~'
>ol or"'lcm con" rn:~c rem-vG>
o; ir>dic-tion must be sa>is>o=tori!y r'es" ive~.
items were excluded from the scope of v
~ >ve co.
>e "ol DoÃa>
ond pet'f )ve ~~osjtjop I> should also be noted tnat th fo!Iowir>"
our review:
seismic ana environmental qualification of the RCGVS, RCGVS operating guidelines and procedures, and required modifications to the p!ant technical specifications and in-service inspection program for the RCGYS.
2m/TER-P -24 Enc'o.sure 6
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H RE FE REN~~r.S I
Letter, R.E. Uhrig (Florida Power 8 Light Company) to D.G. Eisenhut (NRC),
"St. Lucie Unit 1, Docket No. 50-335, Post-Tel Requirements, Reactor Coolant System Yents," dated Auovst 10, 1.Bl.
Le"ter,;.. Ui-.ig (r lorida Power 5 Light Compel ty) to R.A. Clark (NRC)
Unit 1, ~& '. h o.
".'-. =. Pcs'i-TM1 ~ea irements, Reo"tor Co~lant
-=s
~4sl
- ysle, l~ ail I'x y
~ g I rowo I
2m/TER-P-24 Enclosure 6
Pen~ (ri 6