ML19280D100
| ML19280D100 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 04/06/1983 |
| From: | Held J ENERGY, INC., LAWRENCE LIVERMORE NATIONAL LABORATORY |
| To: | NRC |
| Shared Package | |
| ML19280D101 | List: |
| References | |
| CON-FIN-A-0250, CON-FIN-A-250, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM TAC-44416, TF-388-0823A, TF-388-823A, NUDOCS 8306240029 | |
| Download: ML19280D100 (7) | |
Text
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g ' r;g LAWRENCE LIVERMORE LABORATORY h
E.rd i\\L oj ENCLOSURE 2 inhAsa Selected OperLting Reactor Issues Program II
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Reactor Coolant System Vents (flVREG-00737, Item II.B.1. )
NRC FIN A0250 - Project 9 tit'AL TECHNICAL EVALUATION REDORT FOR YANKEE-R0k'E r
Docket Number 50-29 NRC TAC Number 44416 Prepared by J. T. Held of Energy Incorporated - Seattle (Subcontract 4324401) for Lawrence Livermore National Laboratory under contract to the NRC Office of Nuclear Reactor Regulation, Division of Licensing.
NRC Lead Engineer - Gus Alberthal NOTICE "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, 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."
TF-388/0823a April 6,1983 B306240029 830616 CF ADDCK 05000029 CF Un versity v' Californic P.O. Box Sob Livctmore, California 9 550 C. Telephone (415)4221100 : Twx 910 3ES 2339 UcLL LVMR i
Docket Number'50-29 NRC TAC Number 44416 ~
TECHNICAL EVALUATION REPORT
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ON REACTOR COOLANT'SYSTGA VENTS FOR YANKEE-ROWE INTRODUCTION The requirements for reactor coolant system high point vents are stated in porograph (cX3)(iii) of 10 CFR 50.44, " Standards for Combustible Gas Contro! System in Light Water Cooled Power Reactors," and are further described in Standard Review Plan (SRP)
Section 5.4.12, "Reac tor Coolant System High Point Vents," and item it.B.I' of NUREG-0737, " Clarification of TMl Action Plan Requirements." in response to these and previous requirements, the Yankee Atomic Electric Company has submitted information in References I through 3 in support of the vent system at Yankee-Rowe.
EVALUATION The furction of the reactor coolant system vent system (RCSVS) is to vent noncondensible gases from the high points of the reactor coolant system (RCS) to assure that core cooling during natural circulation will not be inhibited. The Yankee-Ro,we RCSV5 provides venting capability from high points of the pressurizer and the reactor vessel head. The noncondensible gases, steam, ond/or liquids vented frorn either the pressurizer or the reactor ussel head are piped and discharged to the vapor container atmosphere through the PORV discharge piping rupture disk or the rupture diaphroorn frorn the low pressure surge tank (LPST). Small volumes of vented gas may be stored in the LPST without release to the vapor container otmosphere. The RCSVS is capoble of venting the volume of noncondensible gases generated from o 100% zirconium-water reaction in less than one hour. However, flow restriction orifices in the pressurizer and reactor vessel head vent paths limit the flow from o pipe rupture or from inadvertent actuation of the vent system to less than the copobility of the reactor coolant makeup system. Hence, the licensee's compliance with 10 CFR 50.46, " Acceptance Criterio for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors," is not offected by the addition of the RCSVS.
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The normal RCSVS paths from the pressurizer and the reacto'r vessel head to the LPST each contain two motor-operated volves (a vent volve and a block volve) in series which Indication of volve position is also are remotely controlled from the main control room.,
provided in the main control room. However, the licensee hos not provided sufficient information regarding the method of volve position detection to verify acceptability.
This is a confirmatory item. The reactor vessel head vent volve and the pressurizer block volve are powered by one emergency motor control center (MCC). The reactor vessel head block volve is powered by the other emergency MCC. The pressurizer vent volve is powered from o nonemergency MCC, which is unocceptable even though it con be powered by the sorne emergency diesei that supplies the reactor vessel ~ head block volve. This is on open item. A. piping cross-connect jo. ins the two normal RCSVS paths between the vent volves and block volves to ensure that RCS venting capability from one high point is maintained even with the failure of one emergency MCC. RCSVS volve seat leakoge can be detected by temperature detectors in the discharge piping and LPST temperature, level, and pressure instrumentation which is indicated and clarmed in the main control room.
The portion of each RCSVS path up to and including the second normally closed vol"e forms o part of the reactor coolant pressure boundary and thus must meet recetor coolant pressure boundary requirements. The licensee has stated that this portion of the vent system is designated Safety Class 2 (Sofety Class I upstream of each flow restriction orifice) in compliance with 10 CFR 50.55a and Regulatory Guide 1.26. The portien of the RCSVS upstream of the second isolation volve is designed to seismic
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criteria consistent with the present plant design. 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 be identified in on occeptable manner.
Although the RCSVS is designed to seismic criterio consistent with the existing plant design, the licensee has not verified that the portion of the RCSVS that is part of the reactor coolant pressure boundary has been occeptably identified and classified Seismic Category I or proposed on occeptable oliernative method for complying with the requirements of SRP Section 3.2.1. In addition, the RCSVS is, designed for pressures and
'emperatures corresponding to 'the RCS design pressure and temperature.
The vent sysiem materials are also compatible with the reactor coolont chemistry, and are designed, fabricated, and tested in accordance with the plant piping specifications and established procedures. The reactor vessel head vent and the pressurizer vent are also acceptobly separated and protected from missiles and the dynamic effects of postulated fe/TER P-32 Enclosure !!
Pm 2
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piping ruptures. We therefore conclude that the design of the portions of the RCSVS up to and including the second normally closed volve conforms to all reactor coolont pressure bourdary requirements, including 10 CFR 50.55o and the opplicable portions of General Design Criterio I, 2, 4,14, 30, and 31, contingent on confirmation by the licensee of the classification of this portion of the system os Seismic Category I or provision of on occeptoble alternative to SRP Section 3.2.1.
The licensee has further escertained that the essential operation of other safety-related systems will not be impaired by the postulated failure of vent system components.
We have reviewed the licensee's RCSVS design to assure on occeptably low probcbility exists for inadvertent or. irreversible octuation of the vent system. Each vent path has two motor-operated volves in series, and each volve has a separate key-locked control j
switch under administrative control and a position indicating light. Also, the volves in each normal vent path are powered from different power supplies and thus, offer intentionally opening a normal RCSVS vent path, o loss of one power supply or on active failum of one volve will not prevent the vent path from being isolated by the remaining volve. However, if the cross-connect piping was used in lieu of either of the normal venting configurations to establish a vent path, or if both the reactor vessel head and pressurizer were being vented at the some time, the RCSVS would be subject to i
irreversible opening if one power source failed. The licensee has stated that the cross-connect poth wou d be used only if a single active failure hos already disabled the normal vent paths and the potential onsequences of not venting were more severe than the potential inability to terminate venting.
The licensee has also indicated that the operator would not vent the reo +,r vessel head and pressurizer at the some time. Since irreversible opening of the RCSVS in the normal situation is not subject to o single active failure, we find this design assures on occeptchly low probability of RCSVS failure contingent upon'the oppropriate incorporation of the above operating restrictions into plant procedures. The licensee has also stated that the controls and position indicating lights added to \\the main control board are located in o section that requires only infrequent operator octions, yet is in close proximity to other indications needed for RCSVS operations and that this should also reduce the potential for inadvertent opera tion. We therefore find that no single octive component foilure or human error should result in inadvertent opening or irreversible operation (i.e., failure to close ofier inieniionc! opening) of the RCSVS.
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w We have also examined the locations where the vent system would discharge to the vapor container atmosphere through the PORV discharge piping rupture disk or the.LPST safety volve rupture diaphragm. Based on o word description and drawing submitted by the licensee (Reference 3), these locations are in areas that assure good mixing with the vapor container otmosphere and prevent the occumulation or pocketing of high concentrations of hydrogen in compliance with 10 CFR-50.44, " Standards for Cornbustible Gas Control System in Light Water Cooled Powei Reactors."
Additionc!!y, these locations are such that the operation of safety-related system. would not be impaired by t
the dischorge of the anticipated mixtures of steam, liquids, and noncondensible gases.
i The licensee has stated that the RCSYS design incorporates provisions for operability testing in accordance with subsection IWV of Section XI of the ASME Code for Category B volves. However, the licensee has not stated that the RCSVS volves will be exercised daring cold shutdown or refueling roih-r than every three months. This is a confirmotary item.
~ CONCLUSION We conclude that the Yankee-Rowe RCSV5 design is sufficient to effectively vent noncondensible gases from the reactor coolant system without leading to on unocceptable increase in the probability of a LOCA or o challenge to containment integrity, meets the design requirerr ents of NUREG 0737 Item 11.B.1 and the opplicable portions of General I
Design Criterio 1, 2, 4,14, 30, and 31, and co'nforms to the requirements of po'rograph (cX3Xiii) of 10 CFR 50.44, with one exception conceming the nonemergency power supply for the pressurizer vent volve os noted above. We therefore recommend following resolution of this open item that the Yankee-Rowe RC5VS design be found acceptable with the following confirmatory items.
The licensee must provide sufficient design information to allow determination of the acceptobility of the volve position indication provisions; verify that the portion of the RCSV5 that is part of the reactor coolant pressure boundary is classified Seismic Category I or provide on occeptable alternative to the requirements of SRP Section 3.2.1; and commit to sexercise the RC5YS volves during cold shutdown or refueling rather than every three months in occordance with the requirements of svSsection IWV of Section XI of the ASME Code for Category B volves.
It should be noted that the fo!!owing items were excluded from the scope of our review:
environmental and seismic qualification of the RCSVS, the RCSVS operating guidelines and plant-specific procedures (which must include procedures that instruct the operator 1 9e /TE R.P-32
to use the RCSV5 cross-connect piping only if the normal RCSVS paths are not operable, and not to vent the reactor vessel head and pressurizer at the some time), and required modifications to the plant technical specifications and in-service inspection program for the RCSV5.
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.i REFERENCES l.
Letter, J.A. Kay (Yonkee Atomic Electric Company) to D.M. Crutchfield (NRC),
"Cateoory 'A' ltem 2.1.9 - Reactor Coolant System Venting," doted July 22,1980.
2.
Letter, J.A. Kay (Yonkee Atomic Electric Company) to D.M. Crutchfield (NRC),
"TMl Action Plan item II.B.1 - Reactor Coolant System Vents," dated July 14, 1981.
3.
Letter, J.A. Kay (Yonkee Atomic Electric Company) to D.M.- Crutchfield (NRC),
" Reactor Coolont System Vent System," dated June 15, 1982.
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