ML20077K845

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

ML20077K845
Person / Time
Site:	Davis Besse
Issue date:	03/14/1983
From:	Held J ENERGY, INC., LAWRENCE LIVERMORE NATIONAL LABORATORY
To:	Alberthal G NRC
Shared Package
ML20077K848	List: ML20077K845
References
CON-FIN-A-0250, CON-FIN-A-250, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM TAC-44364, TF-366-0817A, TF-366-817A, NUDOCS 8306130456
Download: ML20077K845 (6)

Text

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Lawrence Livermore National Laborai.or; a

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I Selected Operating Reactor Issues Program II' V Reactor Coolant System Vents (NUREG-00737: Item II.B.1.)

NRC FIN A0250 - Project 9 -

FINAL TECHNICAL EVALUATION REPORT FOR DAVIS-BESSE 1 fr Docket Number 50-346 NRC TAC Number 44364 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 s Division of Licensing.

NRC Lead Engineer - Gus Alberthal NOTICE "This report was prepared as sa account of work sponsored by the United States Government.

Neither the United States not the United States Department of Energy. not any of their employe:s.

nor any of their contractors, subcontractors, or their employees, makes any warranty, espress or implied, or assumes any legalliability or respon.

sibility for the accuracy, completeness or usefulness of anyinformation.rpparatus,produs or process disclosed, or represents that its use ,

would not infringe privately-owned rights."

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Dockst Number 50-345 NRC TAC Number 44364 TECHNICAL EVALUATION REPORT -

ON REACTOR COOLANT SYSTEM VENTS FOR DAVIS-BESSE I .

INTRODUCTION .

The requirements for reactor coolont system high point vents cre stated in paragraph (cX3)iii) of 10 CFR 50.44, " Standards for Combustible Gas Control System in Light Water Cooled Power Reacters," and are further described in Standard Review Plan (SRP)

Section 5.4.12, " Reactor Coolant System High Point Vents;" and item 11.B.1 of NUREG-0737, " Clarification of TMI Action Plan Requirements." In response to these and previous requirements, the Toledo Edison Company has submitted information in References I through 4 in ' support of the vent system on Davis-Besse Nuclear Station Unit 1.

I EVAL'dATION .

.e The funcfkm of the reactor coolant system (RCS) high point vent system is to vent noncondensible gases from the high points of the RCS to assure that core cooling during natural circulation wil! not be inhibited. The Davis-Besse i RCS high point vent system provides venting capability from high points of the pressurizer and both RCS hot legs. ,

However, the Davis-Besse I high point vent system does not include o reccior vessel head vent as required by 10 CFR 50.44 (cX3Xiii). Until on acceptable reactor vessel head vent is provided, this is on open item.

l The noncondensible gcses, steem, and/or liquids vented from the hot legs discharge to the containment atmosphere by way of the steam generctor compartments. The pressurizer vent discharges into the pressurizer quench tenk. Each path of the RCS high point vent system is designed to vent at least three cubic feet of hydrogen per second at design RCS operating temperature and pressure. A flow restriction orifice in each RCS high point vent system path limits the flow from a pipe rupture or from i.nadvertent actuction of the RCS high point vent system to less than the capability of the reactor coolont makeup system. The flow restriction crifices cre located downstrecm of the isolation volves so T j4/TER-P-6 Enclosure 2 Pcge I of 5

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that maximum protection from flashing and cavitation is efforded to the isolation valves. In.oddition, ths vent system has not introduced any new piping whose size is not encompassed by existing pipe break analyses, and hence, the licensee's compliance with -

10 CFR 50.46, " Acceptance Criteria for Emergency Core Cooling Systems for Light Water Power Reactors,"is not affected by the installation of the high point vents.

The vent paths from both RCS hot leg high points to the containment atmosphere ecch contain two solenoid-operated valves in series. The vent path from the pressurizer to the pressurizer quench tank contains two previously existing mctor-operated valves in series. The volves in all three vent paths are remotely controlled from the main control i room. Positive indicatiedof volve position is also provided in the main control room by the means of position switches mounted on the volves. A degree of redundoney has been provided by powering each of the four solenoid-operated valves in the hot leg vent paths from a different emergency bus to ensure that RCS venting capability from at least one hot leg high point is maintained. Isolation volve seat teokoge con be detected together with other unidentified RCS ieokoge by way of increased makeup requirements and the existing pressurizer, containment, and pressurizer quench tank instrumentation.

The pirtion of each vent path up to and including the second normally closed volve forms a part of the reactor coolant pressure boundary, and thus must meet reactor coolant pressure boundary requirements. The licensee has stated that the vent system is '

designated Ovality Class I (equivalent to Safety Class 1) and Seismic Category I in compliance with 10 CFR 50.55 and Regulatory Guides 1.26 and 1.29. The RCS high point vent system is designed for pressures and temperatures corresponding to the RCS design i

pressure and temperature. In addition, based on a description provided by the licensee, the vent system materials are as follows: -

pipe, ASME SA-376 Type 316 stainless steel.

i fittings, ASME SA-182 F316 stainless steel.

volves, ASME SA-182 F316, SA-240 type 316, SA-479 type 316 stainless ,

steel.

restriction orifice, ASME SA-479 type 316 stainless steel.

All of these materiais cre compatible with the reccior coolant chemistry. The fabrication end installation specifications meet the requirements of SRP Section 5.2.3 and NRC Regulatory Guide 1.44. The RCS high point vent system is also acceptchly j4/TER-P-6 Enclosure 2 Page 2 of 5

l protected from missiles and the dynamic effects of postulated piping Erptures. We therefore conclude that the design and construction of the portion of the RCS high point vent system up to crid including the second normally closed volve conforms to all reactor -

coolant pressure boundary requirements, including 10 CFR 50.55a and the applicable portions of General Design Criteria I, 2, 4,14, 30, and 31. The licensee has further ascertained that the essential operation of safety-related systems will not be impaired by postulated failures of vent system components.

We have reviewed the licensee's RCS high point vent system design to assure on ecceptably low probcbility exists for inodvertent or irreversible octuation of the vent system. Each het leg vent path has two solenoid-operated vent valves in series with separate . Class IE power supplies. The pressurizer vent path has two motor-operated valves in series with the some Class IE power supply, but separation requirements are imposed on the power circuits and control wiring for the two volves to prevent the possibility of hot shorts cousing inodvertent or irreversible opening of the pres.surizer vent path. The licensee has' stated that the valves in both hot leg and pressurizer vent paths will' fait closed on loss of power and that power will be removed from the volve operators during normal operation. The licensee has also stated that o' human factors analysis will be performed on the additional displays and control,s located in the main control room due to addition of the RCS high point verit syste"tri. We therefore find that no single octive component failure or human error should result in inodvertent opening or failure to close offer intentional opening of the RCS high point vent system.1-lowever, 3

from the design inforrnation submitted by the licensee it is not clear whether vent volve l

position indication is dependent on control power. Depending on the configuration of  !

I volve control and position indication power, removing power from the volves os described

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cbe,ve may result in loss of positive volve position ' indication during normal reactor operation. Until it is ensured that direct position indication is continuously provided, this is a confirmatory item.

We have also examined the locations where the RCS high point vent system normally -

discharges to the containment atmosphere inside the steam generator compartments and through the pressurizer quench tank. Based on a description provided by the licensee, these locations are in crecs that would provide good mixing with the containtrent

, atmosphere to prevent the accumulation or pocketing of high concentrations of hydrogen in compliance with 10 CFR 50.44, "Stendards for Combustible Gas Control System in Light Water Cooled Power Reactors." Additionctly, these locations are such thet

J4/TER-P-6 Enclosure 2 Pace 3 of 5

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operation of safety-related systems would not be impacted, by the discharge of the anticipated mixtures of steam, liquids, and noncondensible gases.

The licensee has proposed that the surveillance requirements of Davis-Besse Technical Specification 4.0.5 be opplied to the RCS high point vents except that the surveillance will be performed once per 18 months during the cold shutdown or refueling modes.

CONCLUSION -

We conclude that the Davis-Besse i RCS high point vent system design is sufficient to effectively vent norcond$nsible gases from the reactor coolent system without leading to on unocceptable increase in the probability of a LOCA or o challenge to containment integrity, meets the design requirements of NUREG-0737 Item II.B.I and tne opplicable portions of General Design Criterio I, 2, 4, 14, 30, and 31, and conforms to the requirements of porograph (cX3Xiii) of 10 CFR S0.44, with one exception concerning the required reactor vessel head vent as noted above. We therefore recommend following resolution of this open item that the Davis-Besse i RCS high point vent system design be found occeptable with the following confirmatory item. The pothntial problem conceming the removal of volve control power and positive posit, ion indication must be satisfactorily resolved. It should also be noted that the following items were excluded from the scope of our review: seismic and environmental qualification of the RCS high point vent system, RCS high point vent system operating guidelines crid procedures, and required modifications to the plant technical specifications and in-service inspection program for the RCS high point vent system.

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REFERENCES ,

1. ' Letter, R.P. Crouse (Toledo Edison Company) to R.W. Reid (NRC),with attachment, -

" Reactor Coolant High Point Vents System Design Criteria (Revision 1)," dated February 27,1981.

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2. Letter, R.P. Crouse (Toledo Edison Company) to J.F. Stolz (NRC), with attachment,

" Reactor Coolont High Point Vents S'ystem Design. Criteria (Revision 2)," dated March 23,1982.

3. Letter, R.P. Crouse (Toledo Edison Compaiy) to J.F. Stolz (NRC), responding to NRC's request for additional information on reactor coolant system high point vents, dated April 13,1982., .

4. Letter, R.P. Crouse (Toledo Edison Company) to J.F. Stolz (NRC), with

. Attachment I, " Application for Amendment of Focility Operating License No. NPF-3 for Davis-Bene Nuclear Power Station Unit No.1," dated May 5,1982. ,

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