ML19221B097
| ML19221B097 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-10.4.9, NUREG-75-87, NUREG-75-87-10.4.9, SRP-10.04.09, TAC-43664, NUDOCS 7907120417 | |
| Download: ML19221B097 (12) | |
Text
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OFFICE OF NUCLEAR REACTOR REGULATION SECTION 10.4.9 AUXILIARY FEECWATER SYSTEM (PWR)
REVIEW RESPONSIB1LITIES Primary - Auxiliary Systems Branch (ASB)
Secondary - Reactor Systems Brar.cn (RSB)
Instrumentation and Control Systems Branch (ICSB)
I Structural Engineering Branch (SEB)
Mechanical Engineering Branch (MEB)
Materials Engineering Branch (MTEB) l Power Systems Branch (PSB)
I.
AREAS OF REVIEW The auxiliary feedwater system ( AFS) normally operates during startup, hot standby and shutdown as the feedwater system for pressurized water reactor (PWR) plants. In conjunc-tion with a seismic Category I water source, it also functions as an emergency system fcr the remaval of heat from the primary system when the main feedwater system is not available for emergency conditions including small LOCA cases. The AFS operates over a time period soft:cient either to hold the plant at hut standby for several hours or to cool down the primary system, at a rate not to exceed limits specified in technical specifications, to temperature and pressure levels at which the low pressure decay heat removal system can operate. The design of the AFS should treet the requirements of General Design Criteria 2, 4, 5, 19, 44, 45 and 46.
The ASB reviews the AFS from the condensate storage tank (normal operation), or the seismic Category I water supply including valving and cross-connects (errergency operation), to the connections with the steam generators, which are made either through a connection to the main feedwiter piping or through separate auxiliary feedwater piping con.iected directly to the steam generators. All inter-connections and cross-connections l
are included in the resiew.
The review also includes AFS components, e.g.,
pumps, valves, and piping, with respect to their functional performance as affected by adverse environmental occurrences, abnormal operational requirements, and off normal conditions, e.g.,
small breaks ir the primary system or the loss of offsite power.
The system is reviewed to determine that a single malfunction, a failure of a component, or the loss of a cooling source does not reduce the safety-related functional performance capabilities of the s/ stem.
The ASB review assures that:
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I.
System components and piping have sufficient physical separation or shielding to protect the essential portion _ of the system from the effects of internally and externally generated missiles.
P.
The system satisfies the recommendaticns of Branch Ter.hnical Position ASB 3-1 with l
respect to the ef fects of pipe whip arid jet impingement thal may result from.igh or moderate energy piping breaks or cracks (in this regard the AFS is considered tc be a high energy system).
3.
The system and components satisfy design code requirements, as appropriate for the assigned quality group and seismic classifications.
4.
The f ailure of non essential equiptrent or components does not af fect essential functions of the system.
5 The sy. tem is capable of withstanding a single active failure.
6.
The system possesses diversity in rtotive po er sources such that system perf ormance requirements may be me with either of the assigned power sources, e.g., a system w't, an a-c subsystem and a redundant steam /d c subsystem.
7.
The system design precludes the occurrence of fluid flow instabilities, e.g., water hammer, in system inlet piping during normal plant operation or during upset or accident conditions (see SRP Section 10.4.7).
I 8.
Functional capability is assured by suitable protection during abnormally high water levels (adequate flood protection considering the probable maxinum flood).
l 9.
The capability exist; to detect, collect, and control system leakage and to isolate portions of the system in case of excessive leakage or component malfunctions.
10.
Provisions are made for operational testing.
l' Instrumentation and control features are provided to verify the system is operating in a car;ect mode.
l?
The system is capable of autonatically initiating auxiliary feedwater flou upon receipt of a system actuation signal.
13.
The system satisfies the recommendations of Regulatory Guide 1.62 with r0spect to the
= tem Japability to manually initiate protective action by the auxiliary feed *ater system.
Rev. I 10.4.9-2
14.
The system design possesses the capability to automatically terminate auxiliary feedwater flow to a depressurized steam generator, and to automatically provide feedwater to the intact steam generator.
15.
The system possesses sufficient auxiliary feedwater flow capacity so that a cold shutdown can be achieved.
16.
The applicant's proposed technical specifications are such as to assure the continued reliability of the AFS during plant operation; i.e.,
the limiting condi-tions for operatico and the surveillance testing requirements are specified and are consistent with those for other similar plants.
Secondary review evaluations are performed by other branches and the results used by the ASB to complete the overall avaluation of the system. The secondary reviews are as I
follows.
The RSB identifies any functional interfaces between essential components of the reactor coolant er emergency core cooling systems and the AFS that are required for operation during normal operations or accident conditions.
The RSB establishes post-accident heat loads and the associated time intervals available for cooling various components. The SEB determines the acceptability of the design analyses, procedures and l
criteria used for seismic Category I structures that must withstand the effects of natural phenomen3 such as the safe shutdown earthquake (SSE), the probable maximum flood (PMF), and tornado miss'ies.
The pef.evi(ws the seismic qualification testing and operability of components and cont irms that ctmponents, piping, and structures are designed in accordance with applicable cod ( s and standards. The MTEB verities that inservice inspection requirements are met for systom components and, upon request, verifies the compatinility of the materials of constrsction w;th service conditions.
The ICSB and PSB evaluate system controis, instrumentatiun, and power sources with respect to l capability, capacity, and reliability durir g rormal and emergency conditions.
II.
MCEPTANCE CRITERIA Ac ceptability of the design of the auxiiiary f eed ater system, as described in the applicant's safety analysis report (SAR), is based on specific general oesign criteria and regulatory guides.
Listed below are tte specific criteria as they relate to the M S.
General Design Criterion 2, as related tc structures housing the system and the system itself being capable of withstanding the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, ard floods.
I 2.
General Design Criterion 4, with respect to structures housing tha system and the system itself being capable of witnstanding the effects of external missiles and internally generated missiles, pipe wr-ip, and jet impinurment rces associated with pipe breaks.
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3.
General Design Criterion 5, as related to the capability of shared systems and com-ponents important to safety to perforn required safety functions.
4 General Design Criterion 19, as related to the design capability of system instrumen-tation and controls for prompt hot shutdown of the reactor and potential capability for sobsequent cold shutdown.
b.
General Design Criterico 44, to assure:
a.
The capability to transfer heat loads from the reactor system to a heat sink under both normal opeeating and accident conditions.
b.
Redundancy of components 50 that under accident conditions the safety function can be performed assuming a sing'e actise component failure.
(This may be coincident with the loss of of f site power for certain events. )
c.
The capability to isolate components, subsystems, or piping if required so that tre system safety function will be maintained.
6.
General Design Criterion 45, as reiated to design provisions made to permit periodic inservice ins ection of system components and equipment-7.
General Design Criterion 46, as related to design provisions made to permit appropriate functional testing of the system and components to assure structural integrity and leak-tightness, operability and performarice of active components, and capability of the integrated system to function as i ntended during normal, shutdown, and accident conditions.
8.
Regulatory Guide 1.26, as related to t he quality group classification of system cerconents.
9.
Regulatory Guide 1.29, as related to the seismic design classification of system components.
10.
Regulatory Cuide 1.62, as related to design provisions made f or manual initiation of each protect 1,o action.
11.
Regulatory Guide 1.102, as. elated to the protection of structures, systems, and components important to safety from the effects of flooding.
12.
Regulatory Guide 1.117, as related to the protection of structures, systems, and components important to safety from the effects of tornado missiles.
13.
Branch Technical Positions ASB 3-1 and MEB 3-1, as related to breaks in high and l
moderate energy piping systems outside ccntainment.
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14.
Brarch Technical Position ASB 10-1, as related to auxiliary feedwater pump drive I
and power supply diversity.
For those areas of review identified in subsection I of this SRP section as being the responsibility of other branches, the acceptance criteria and their methods of appli-cation are contained in the SRP sections corresponding to those branches.
III. REVIEW PROCEDURES The procedures below are used during the construction permit (CP) review to determine that the design criteria and bases and the preliminary design as set forth in the preliminary safety analysis report meet the acceptance criteria given in subsection II.
I For operatinf lice,se (Ot) anplications, the procedures are utilized to verify that the initial des'gn criteria and bases have been appropriately implemented in the final design as set forth in the final safety analysis report. The procedures for OL appli-cations also include a determination that the content and intent of the technical specifications prepared by the applicant are in agreement with the 3quirements for system testing, m'nimum performance and surveillance developed as a result of the staff's review.
Upon request from the primary reviewer, the secondary review branches will provide input for the areas of review stated in subsection 1.
The prim 3ry reviewer obtains and uses such input as required to assure that this review procedure is complete.
For the purpose of this SRP section, a typical system is assumed which has redundant l
auxiliary feedwater t: wins, with a 50% capacity motor-driven pump in each train feeding directly to the steam generators, and a 10(4 Capacity steam turbine-driven pump able to supply either of the redundant trains. The pumping capacity should permit the system to hold the plant at hot standoy and subsequently to cool down the reactor at specified cooldown rates.
This requirement should also be met for conditions involving a small break araa loss-of-coolant accident (LOCA) cr a pipe break outside containment. For cases where there are variations from the typical arrangement, the reviewer adjusts the review procedures to suit the design. However, the system design is required to meet the acceptanca criteria given in subsection II.
l i.
The SAR is reviewed to determire that th( system description and piping and instru-mentation diagrams (P& ids) identify tte AFS equipment and arrangoment that is used for normal operation and f or safe plant shutdown (essential) operation. The system P& ids, layout drawings, a-d component descriptions and characteristics are then reviewed to verify that:
a.
Minimum performance requirements for the system are sufficient for the v3rious functicas of the AFS.
b.
Essential portions of the AFS are isolab'a from non essential portinns, so that system performance is not inpaired in the event of a failure of a non-essential compnnent.
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c.
Component and system descriptions in the SAR include appropriate seismic and quality group classifications, and the P& ids indicate any points of change in piping quality group classification.
d.
Design provisions have been made that permit appropriate inservice inspection and functional testing of system components important to safety.
It is acceptable if the SAR information delineates a testing and inspection orogram and if the system drawings show the necessary recirculation loops around pumps or isolation valves as raay be required by this program.
2.
The reviewer varifies that the system safety function will be maintained as required, in the event of adserse environmental phenomena, breaks or cracks in fluid system piping outside containment, system component failures, loss of an onsite motive power source, or loss of offsite power.
The reviewer uses engineering judgment and the results of failura modes and effects analyses to determine that:
The failure of portions of the system or of other systems not designed to a.
seismic Category I standards and located close to essential portions of the system, or of non-seismic Category I structures that house, support, or are close to essential portions of the AFS, will not preclude operation of the essential portions of the AFS.
Reference to SAR sections describing site features and the general arrangement and layout drawings will be necessary, as well as the SAR tabulatico of seismic design classifications for structures and systems.
b.
The essential portions of the AFS are protected from the effects of floods, hurricanes, tornadoes, and internally or externally generated missiles. Flcod protection and missile protection criteria are discussed and evaluated in detail under the SRP Section 3 series. The location and design of the system.
l structures, and pump ruoms (cubicles) are reviewed to determine that the degree of protection provided is adequate. A statement to the effect that the system is located in a seismic Category I structure that is tornado missile and flood protected, or the components of the system will be located in individual cubicles or rooms that will withstand the effects of both flooding and missiles is acceptable.
The essential portions of the system are protected from the effects of high c.
and moderate energy line breaks in accordance with Branch Technical Position ASB 3-1.
Layout drawings are reviewed to assure that no high or moderate l
energy piping systems are close to essential portions of the AFS, or that protection from the effects of failure will be provided. The means of providing such protection will generally be given in Section 3.6 of the SAR and procedures fcr reviewing this information are given in SRP Section 3.6.
l Rev. I 10.4.9-6 149
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d.
Essential components and subsystems necessary for safe shutdown can function as required in the event of loss of offsite power. The SAR is reviewed to see that for each AFS component or subsystem affected by the loss of offsite power, system flow and heat transfer capability meet minimum requiremvits.
Statements in the SAR and the results of failure modes and effects analyses are considered in assuring that the system meets these requirements.
The system is designed with adequate redundancy to accommodate a single active e.
component failure without loss of function.
f.
Diversity in pump motive power sources and essential instrumentation and control power sources has been provided. The diverse system including pump (s), controls and valves should be independent of offsite and onsite AC power sources in accordance with the guidelines of Branch Technical Position ASB 10-1.
g.
The system is designed with adequat(- instrumentation to automatically initiate auxiliary feedwater flow to the steam generators upon receipt of an actuation signal. The initiation signal should start all auxiliary feedwater pumps and supporting systems, align the au> iliary feedwater sources, snd open flow paths from the auxiliary feedaater pumps to the steam generator (s).
h.
The system is designed with the capability to manually initiate the protective actions necessary so that the auxiliary feedwater system design satisfies the recommendation of Regulatery Guide 1.62.
i.
The AFS is designed with redundant instrumentation so that the system will automatically limit or terminate au>iliary feedwater ficw to a depressurized steam generator, and to assure that the minimum required flow is directed to the intact steam generator (s).
j.
The AFS is designed with suffici(nt flow capacity so that the system can remove residual heat over the ent ire range of reactor operation and achieve a cold shutdown condition.
IV.
EVALUATION FINDINGS The reviewer verifies that sufficient information has been provided and his review suppcrts conclusions of the following t 0e, te be included in the staff's safety esalu3-3 tion report:
"The auxiliary ferdwater system incluces all components and equipment from the condensate storage tank (normal operation) or the seismic Category I emergency water supply (including valves and crc ss connections) to the connection with the steam generators. Based on the resiew of the applicant's pronm ed design criteria, design bases and saf ety classification fcr the auxiliary feeduter system, and 149 127 l0.4.9-7 ROV-I
system performance requiremerts during normal, abnormal, and accident conditions, the staff concludes that the design of the auxiliary feedwater system and support-ing systems is in conformance with the Commission's regulations as set forth in General Design Crit +rion 2, " Design Bases fnr Prntection Against Natural Pheno-mena," General Design Criterion 4, " Environmental and Missile Design Bases,"
General Dmign Criterion 5, " Sharing nf Structures, Systems, and Components,"
General Design Criterion 19, " Control Room," General Design Criterion 44, " Cooling Water," General Design Criterion 45, " Inspection of Cooling Water System," and General Design Criterion 46, " Testing of Cooling Water System," and meets the guidelines contained in Regulatory Guide 1.26, " Quality Group Classifications and Standards for Water, Steam, and Radioactive-Waste-Containing Components of Nuclear Power Plants," Regulatory Guide 1.29, " Seismic Design Classification,"
Regulatory Guide 1.62, " Manual Initiation of Protective Actions," Regulatory Guide 1.117, " Tornado Design Classification," Branch Technical Position ASB 10-1, " Design Guidelines for Auxiliary Feedwater System Pump Drive and Power Supply Disersity for PWRs," and Branch Technical Position ASB 3-1 and MEB 3-1, and therefore, is acceptable.
V.
REFERENCES 1.
10 CFR Part 50, Apper. dix A, Genera: Desicn Criterion 2, " Design Bases for Protec-tion Against Natural Phenomena."
2.
10 CER Part 50, Appendix A, General Design Criterion 4. " Environmental and Missile Design Bases."
3.
10 CFR Part 50, Appendix A, General Design Criterion 5, " Sharing of Structures, Systems, and Components.'
4.
10 CFR Part 50, Appendix A, General Design Criterion 19, " Control Room."
5.
10 CFR Part 50, Appendix A, General De sign Criterion 44, " Cooling Water."
6.
10 CFR Part 50, Appendix A, General Design Criterion 45, " Inspection of Cooling Water System."
7.
10 CFR Part 50, Appendix A, General Design Criterion 46, " Testing of Ce
,g Water System."
8.
Regulatory Guide 1.26, " Quality Grcup Classifications and Standards fer Water, St 3m, and Radioactive-Waste-Containing Components of Nuclear Power Plants."
l 9.
Regulatory Guide 1.29, " Seismic Design Classification."
I l CJ, y Rev. I 10.4.9-8
10.
Regulatory Guide 1.62, " Manual Initiation of Protective Actions."
11.
Regulatory Guide 1.102, " Flood Protection for Nuclear Power Plants."
12.
Regulatory Guide 1.117, " Tornado Design Classification."
13.
Branch Technical Positions ASB ;-1, " Protection Against Postulated Pipirig Failures in Fluid Systems Outsidt Containment, attached to SRP Section 3.6.1, and MEB 3-1,
" Postulated Break and Leakage Locations in fluid System Piping Cutside Containment,"
attached to SRP Section 3.6.2.
I 14.
Branch Technical P:sition ASB 10 i, " Design Guidelines for Auriliary Feedwater l
System Pump Drive a.id Power Supply Diversity for Piessurized Water Reactor Plants."
149 129 10.4.,-l Rov. I
BRANCH TECHNICAL POSITICN ASB 10-1 l
DESIGN GUIDELINES FOR AUXILIARY FEEDWATER SYSTEM PUMP DRIVE AND POWER SUPPLY DIVERSITY FOR PRESSURIZED WATER REAC10R PLANTS A.
BACKGROUND Heat removal from pressurized water reactnr plants following reactor trip and a loss of offsite power is accomplished by the operation of several systems incluJing the secondary system via the steam relief system.
Similar capability is required to mitigate the conse-quences of certain postulated piping breaks.
Such heat removal involves heat transfer from the reactor to the steam generators, resulting in the production of steam which is then released to the atmosphere.
In this process it becomes necessary to supply makeup water to the steam generators. This is accomplished by the use of an auxiliary feedwater system, which generally consists of redundant components that are powered by both electrical and steam-driven sources.
The auxiliary feedwater system functions as an engineered safety system because it is the only source of makeup water to the steam generators for decay heat removal when the main feedwater system becomes inoperable. It must, therefore, be designed to operate when needed, using the principles of redundancy and diversity in order to assure that it can function under postulat"i accident conditions. The majority of current systems are powered by electrical or steam-driven sources. Operating experience demonstrates that each type of motive power can be subject to a f ailure of the driving component itself, its source of energy, or the associated control system.
The effects of such failures can be minimized by the utilization of diverse systems that include energy sources of at least two different and distinct types.
The provision of several independent flow paths for the auxiliary feedwater system serves to areclude the possibility of a complete loss of function due to a single event, either occurring alone, or in conjunction with the f ailure of an active component. The auxiliary feedwater system is categorized as a high energy system, because either that section of line which cc.inects te the main feedwater piping or the steam generator is pressurized during plac* operation or else the entire system is pressurized when in use during startup, hot standby, and shutdown.
The staff believes that it is necessary to establish design guidelines for the auxiliary feedwater system, arj in this regard has uevelnped guidelines that may be used to select the minimum diversity acceptable for auxiliary feedwater system pump drives and power supplies.
x s Rev. 1 10.4.9-1C
B.
BRANCH TECHNICAL POSITION 1.
The auxiliary feedwater system should consist of at least two full-capacity, independent systems that include diverse power sources.
2.
Other powered components of the auxiliary feedwater system should also use the concept of separate and multiple sources of motive energy. An example of the required diversity would be two separate auxiliary feedwater trains, each capable of removing the afterheat load of the reactor system, having one separate train powered from either of two a-c sources and the other train wholly powered by steam and d-c electric power.
3.
The piping arrangement, both intake and discharge, for each train should be designed to permit the pumps to supply feedwater to any combination of steam generators. This arrangement should take into account pipe failure, active component failure, power supply failure, or control system failure that could prevent system function. One arrangement that would be acceptable is crossover piping containing valves that can be operated by remote manual control from the control room, using the power diversity principle for the valve operators and actuation systems.
4.
The auxiliary feedwater system should te designed with suitable redundancy to offset the consequences of any single active component failure; however, each train need not contain redundant active components.
5.
When considering a high energy line break, the system should be so arranged as to assure the capability to supply necessary emergency feedwater to the steam generators,l despite the postulated rupture of any high energy section of the system, assuming a et.ncurrent single active failure.
C.
REFERENCES None ROV-I 10.4.9-11