ML20076F263

Selected Operating Reactor Issues Program Ii:Rcs Vents (NUREG-0737,Item II.B.1), Final Technical Evaluation Rept

ML20076F263
Person / Time
Site:	Millstone
Issue date:	03/02/1983
From:	Held J ENERGY, INC., LAWRENCE LIVERMORE NATIONAL LABORATORY
To:	Alberthal G NRC
Shared Package
ML20076F267	List: ML20076F263
References
CON-FIN-A-0250, CON-FIN-A-250, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM TAC-44385, TF-349-0812A, TF-349-812A, NUDOCS 8306080065
Download: ML20076F263 (6)

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. LAWRENCE UVEBUORE LABORATORY -

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. Selected Operating Reactor Issues Program II Reactor Coolant System Yents (NUREG-00737, Item II.B.1.)

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FINAL TECHNICAL

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D'ALUATION RE? OFT FOR MILLSTONE 2 l

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' ' Docket Number 50-336

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Prepared by J. T. Held of Energy Incorporated - Seattle (Subcontract" 4324401) for Lawrence Livennore National Laboratory under. contract to the NRC Office of Nuclear Reactor Regulation, Division of Licensing.

NRC Lead Engineer - Gus Alberthal NOTICE l "This report was prepared as 'an account of work sponsored by the United States Government. Neither the United States nor the United States Department of Energy, nor any of their employees, nor any of their contractors, subcontractors, or their employees,' c:akes 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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l XA Copy Has Been.Sent 16]DR , ,

a l I March 2, 1933

Docket Number 50-336 .

NRC TAC Number 44385 ,

, TECHNICAL EVALUATION REPORT ON REACTOR CODLANT SYSTEM VENTS .

FOR MILLSTONE 2 INTRODUCT'ON '

The r:nuirements for reactor coolont system high point vents c.e stated in paragrcph (cK3)(iii) of 10 CFR 50.44, "Stonderds for Combustible Gas Control System in Light Water Cooled Power Reactors," and 'are furthdidescribed in Standard' Review' Plan (SRP') ~

Section S.4.12, " Reactor Coolant System High Point Vents," and item !!.B.I , of NUREG-0737," Clarification of TMI Action Plan Requirements." In. response to these and previous requirements, the Northeast Nuclear Energy Company has submitted '

) information in References I through 3 in support of the vent system at Unit 2 of the Millstone Nuclear Power Station. -

l t EVALUATION' , , ,, ,

The function of the reactor coolant system (RCS) vent rystem is to vent noncondensible ,

j gcses from the high points of the RCS to cssure that core cooling during naturol circulation will not be inhibited. The Millstone 2 RCS vent system provides venting capability from high points of the pressuriner and the reactor . vessel head. The l noncondensible gases, steam, and/or liquids vented from either the pressurizer or the reactor vessel head are piped and discharged to o common sparger in the containment outer annulus in the vicinity of the containment air recirculation and cooling units. Each RCS vent path is designed to vent a volume of gas in excess of one half of the RCS volume in standard cubic feet in one hour. The addition of the RCS vent system has not, however, introduced any new piping whose size is not encompassed by existing pipe break

. onelyses. Hence, the acceptability of the licensee's previously cpproved Icss-of-coolant-occident analyses and complia'nce with 10 CFR 50.46, " Acceptance Criteria for l Emergency Core Cooling Systems for Light Water Nuclear Power Reactors," is not i offected by the addition of the RCS vent system.  ;

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' ICO EM-3 5 _ _ . _ _ _ . _ _ . _ , _ _ _ _ . . _ _ _ _ _ _ _ _ _ . _ , _ _ __ . _ . Enclosure _ ____ _

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The vent from the pressurizer end the vent from the reactor vessel head to the containment each contain two parallel treins of two solenoid-operated globe valves in series which are r motely controlled from the main control room. Indicction of valve position for each of the eight volves is also provided in the main control room.

Redundancy bcs been provided for both the pressurizer and the recetor vessel hecd vents by powering the volves in the percitel piping trains from each high point vent from secc ete 12SV DC emergency buses to ensure thct RCS venting cepebility from ecch hic:-

4 po;nt is maintained. RCS vent svstem volve sect leakage con be detected by wey of thermocouples i uteiled downstreem of the veives. At a predeterrnined set ocint on clorm typewr*ter will be 'octucted, identifying a high te nperature reading on the oppropriate thermocouple.

9 The portion of each RCS vent path up to and including the second normally closed valve forms a part of the reoctor coolant pressure boundary and thus must meet reactor coolant pressure boundary requirements. Accordingly, this portion of the RCS vent system is designated as Class I, the reoctor vessel head vent and the pressurizer vent are acceptably separated and protected from missi}~es and the dynamic effects of postulated piping ruptures, and the RCS vents are designed for pressures and temperatures corresponding to the RCS design pressure and tempercture. In cddition, the vent system

. components are made of 316 stainless steel and are compatible with the reoctor coolant

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chemistry. The RCS vent system mcteriais are also manufactured and certified in

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occordance with ASME Code Section II. The solenoid volves are qualified as Seismic Category I, and the piping was analyzed occording to ASME Code Section til Subsection NS which includes the seismic design criteria to remain functional during the safe shutdown earthquake. However, SRP Section 3.2.1 requires that structures, systems, and components that are important to safety be classified as Seismic Category I items and l

identified in on occeptable manner. Although the RCS vent system is designed to l

cceepicble seismic criteric, the licensee has not verified that the portion of the system piping that is port of the reactor coolont pressure boundary has been ecceptably identified and classified Seismic Category I. We therefore conclude that the desian of the portions of the RCS vent system up to and including the second normally closed valve conforms to all reactor coolont pressure boundary requirements, inc!vding 10 CFR 50.SSa and the applicable portions of General Design Criteria I, 2, 4,14, 30, and 31, with the exception of the needed confirmation by the licensee of the cicssificction of the pipin,g es Seismic Category I. The licensee hos further ascertained that the essential ooerotion of other safety-related systems will not be imocired by postulated failures of RCS vent syste m components.

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We hcve reviewed the licensee's RCS vent sy' stem design to cssure en ceceptably low

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probability exists for inodvertent or irreversible octuation of the vent system. Each vent path has two solenoid-operated volves in series, and ecch valve hcs an individual key-locked vc!ve switch with open end clcsed position indication which is maintained under odministrative control. The valves cre powered by independent, redundant vital OC emergency buses energized from sepercte, redundent battery systems cnd foil to the ciosed position in tN ev-nt of loss of powr. In ocdition, power is removed from the ec!ves during normal operation. Fu-the me e, the licensee hcs stcted thet the controls cnd dispicys..o5ded to the main control room were reviewed from the humen engineering standpoint and location, operation and instrumentation indication are in occordance with

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NUREG-0700.' We therefore find that no single active component failure or human error t

should result in inadvertent opening or irreversible operation (i.e., failure to close offer i

intentional opening) of the .RCS vent system. However, RCS vent volve position .

fndication is powered from 'fl$e sarne power supply which supplies control power. If the -

licensee's intention is to remove controf power by opening the breakers rather than locking out power to the valves by the key-lock switches, positive valve position l

l fndication during normo! plant operation will be lost. Until the licensee verifies that the breckers will not be maintained open during normal plant operation or the licensee provides an acceptable alternative method of continuous valve position indication, this is on open item. . -

We have oiso examined the location where the vent system normally discharges to the l containment atmosphere in the vicinity of the containment cir recirculation and cooling units. Based on a description provided by the licensee (Reference 2) this location is in on creo that assures good mixing with the containment atmosphere to prevent the occumulation or pocketing of high concentrations of hydrogen in complicnce with 10 CFR 50.M, " Standards for Combustible Gcs Control System in Light Water Cooled Power Reoctors." Ad:litionc!!y, this location is such that the operation of safety-related systems would not be adversely affected by the discharge of the enticipated mixtures of stecm, liquids, and roncondensible gases.

The design provides for individual test and open/ closed indication of each volve, end the licensee has mode provisions for operobility testing in accordance with subsection IWV of Section XI of the ASME Code. However, the licensee has not stated that the RCS vent volves will be exercised during cold shutdown or refueling rather then every three rnenthr. This is a confirmatory item.

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1. I CONCLUSION ~

We conclude that the Millstone 2 RCS vent system design is sufficient to effectively vent noncondensible gcses from the reactor cooient systern without leading to on unocceotchie increcse in the probcbility of a LOCA or c challenge to containmer.t inte;:rity. meets the cesig , recuirements of NUR:_G-0737 Item II.B.! cnd the coolicable portions of General Dett gr .Criteric I , 2, 4, 14, 30, and 31, cr4 ec-forms to the recuirer .r s of i peregree (cX3Xiii) of 10 C R 50.44, with one exception concerning pos:tive vc ve

! t position indication es noted cbove. We therefore recommend following resolution of this l

l cpen item that the Millstone 2 RCS vent system design be found acceptable with the 4 i

following two confirmatory iterr)s. The licensee must verify that the portion of the RCS j vent system piping that is part of the reoc' tor coolant pressure boundary is classified Seismic Category 1, and the licensee must commit to exercise the RCS vent volves during l

cold shutdown or refueling rather than every three months in accordance with the i requirements of subsection IWV of Section XI of_the ASME Code for Category B volves. '

! ' in addition, it should be noted that the following items were excluded from the scope of our review: seismic and environmen'tal qualification of'the RCS vent system, RCS vent

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system operating guidelines and procedures, and required modifications to the plant . . .

technical specifications and in-service inspection program for the RCS vent system.

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REFERENCES 1.

Letter, W.G. Counsit (Connecticut Ycnkee Atomic Power Company, Northeast Nuclear Energy Company) to H.R. Denton (NRC), "Haddcm Neck Picnt, Millstone Nuclear Power Station, Unit,Nos. I cad 2, TMI-2 .nort-Term Lessons-Lectned Ir plementation," dcted December 31,1979.

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Letter, W.C. Counsit (Nc+ecst Nuciec- E.sergy Com:n. y) to 0.G. EisenhUt (NRC),

" Millstone Nuclecr Power Station, Unit No. 2, Reccior C:oient System Vents,"

dated June 29, I 981. .~-

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3. Letter, W.G. Counsil (Connecticut Yankee Atomic Power Company, Northeast Nuclear Energy Company) to D.M. Crutchfield (NRC), "Hoddom Neck Plant, Millstone Nuclear Power Station, Unit No. 2, Recctor Coolant System (RCS) Vents,

(! tem II.B. I), Request for Additional Information," dated June 2,1982. ,

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. -ef TER_.o.! 6 Enclosure