ML20198F267
| ML20198F267 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 01/02/1974 |
| From: | Maccary R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Moore V US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| CON-WNP-0937, CON-WNP-937 NUDOCS 8605280455 | |
| Download: ML20198F267 (16) | |
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V. A. Moore, Assistaat Director for Light Water Reesters, Group 2 Directorate of Licensing FIRST It0UMD REVIEW OF DOCKETED PSAR, WPPSS Plant Names WFFSS Nuclear Project No.1 Licensing States CF Docket Number: 50-460 1
Responsible RP Branch and Project Manager: LWR 2-3, T. Cox 3esponsible TR Branch: MEB
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Requested Completion Dates December 28, 1973 Descripties of Resposee Applicant's amended PSAR, following acceptance review Review Status: Ausiting Information I
Adequate respeesee to the enclosed list of comments, prepared by the
,yff Mechaalcal Engineering Branch, Directorate of Licensing, are required before we can complete our review of the subject application. These i
,,.y p comments pertala to the subject PSAR through Amendment 1.
Pleaue note that there are several instances of a brand area of possible difference between the applicant's proposals and acceptable staff positions. These instances include pipe whip protection both 1
inside and entside co=*=i===ne and au cperability assurance program for active pumps and valves. The apparent differences are of such a nature as to require a timely meeting with the applicant's qualified persosaal.
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With respect te comuments 3.9/5, 5.0/2 and 5.0/3 in the enclosed list, i
note that the applicant has agreed to address these matters in a future
=====l===e in the saae of the first comment and "as soou as the new
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requirements have been evaluated" in the cases of the other comments.
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The subjects of the comments are active component operability assurance programs, stress eriteria for Class 1 active valves and establishing the acceptability of computer prograss. The applicant's responses should be available for review well before the second round of comments and positions requested completion date.
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JM 2 V. A. Moore ID It-frequently ot. cure that an applicant will taka full advantage of the possibility of postponing SAR infor: nation until the OL stage.
In some instances this is quita logical, in others it may create the possibility of undue hardship upon the applicant at a later date, and in still other instances it may create the possibility of a delayed inconvenience. A situation somewhere between the latter two cases exists in connection with tha required explanation of analysis procedures to be used in lieu of testing for the seismic qualification of mechanical and electrical equipment. The applicant Esa cited, in PSAR 3.10.2, an example of a' typical method for a pump motor set.
It is advisable to alart the applicant to the need for more detailed explanations covering all Seismic Catence I equipment by the time of the OL review.
Oiiginal sig5ed by 1111 Leeary R. R. Maccary, Assistant Director for Engineering Directorate of Licensing cc w/ encl:
S.11. llanauvr( DRTA J. M. Hendrie, L A. Schwencer, L J. P. Knight, L T. II. Cox, L
- 5. M. Hou, L A. B. Miller,} L cc w/o encir-A. Giambusso, L W. G. Mcdonald, L Docket File 50-460 L, Reading File L:MEB File
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MECHANICAL ENGINEERING BRANCH DIRECTORATE OF LICENSING WPPSS NUCLEAR PROJECT NO. 1 DOCKET No. 50-460 REQUEST FOR ADDITIONAL INFORMATION 3.6 Protection Acainst Dynamic Effects Associated with the Postulated Rupture of Piping 1.
Criteria acceptable to the staff and contemporary with this application for postulating pipe breaks, cracks and leaks in high energy lines and in moderate energy lines both inside and outside containment and for establishing a design basis for pipe-whip restraints, barriers and the like as' well as for other measures such as separative plant layout are presented in the following documents:
(a) Regulatory Guide 1.46 entitled:
" Protection Against Pipe Whip Containment" (b) Letter dated circa December 29, 1972 from Regulatory (A. Giambusso) to the industry on the subject " General Information Required for Con-sideration of the Effects of a Piping System Break Outside Contain-ment" (c) Attachment 1 to this enclosure, entitled " Pipe Whip Analysis."
A significant number of the criteria for these matters presented in PSAR 3.6 differ from those given in the references cited above in major
2-specific details. It is possible, however, that implementation of the criteria of PSAR 3.6 may provide equivalent protection for this plant to that which would be provided by implementation of those criteria which are already judged acceptable. Demonstrate that the proposed criteria provide protection equivalent to that provided by the acceptable criteria or modify the proposed criteria to conform with those of the references a, b and c listed above.
2.
Sub=it the design criteria for pipe runs which extend from the primary Containment penetrations and extend to the first isolation valve outside containment.
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. 3.9 Mechanical Systems and Components (Comment 2, below, includes a reference to 3.10 Seismic Qualification of Category 1 Instrumentation and Electrical Equipment) 1.
The plan for the Vibration Operational Test Program presented in PSAR 3.9.1.1 is partially lacking in detail even for the CP stage.
Provide an adequate response which makes a commitment to more clearly conform to the procedures described in the Attachment B ("Preoperational Piping Dynamic Effects Test Program") to Enclosure No. 1 of the letter dated August 20, 1973, from Regulatory (A. Giambusso) to the Washington Public Power Supply System (J. J. Stein).
2.
Criteria acceptable to the staff and contemporary with this application for planning the dynamic testing portion of a seismic qualification program for safety related mechanical and electrical equipment are presented in the Attachment C to Enclosure No. 1 of the letter dated August 20, 1973 from Regulatory (A. Giambusso) to the Washington Public Power Supply System (J J. Stein).
Said Attachment C is entitled:
" Electrical and Mechanical Equipment Seismic Qualification Program." The corresponding criteria presented in PSAR 3.10.2 do not conform in a number of specific areas, including the effects of additive responses resulting from directional cross-coupling and also resulting from off-resonance responses to various frequency components of the design basis, in-situ excitation.
Additionally, the degree of conservatism of the envisioned test input intensity is not clear. Also, it is not completely clear from the text of the PSAR whether the test plan described is intended to apply to mechanical as well as to electrical equipment.
ee.
Identify the differences between the PSAR program and that which is recognized acceptable by the staff. Modify the program plans accord-ingly or demonstrate that the programs are equivalent in their imple-mentation.
3.
The commitment by the applicant in PSAR 3.9.1.3 regarding the Dynamic System Analysis Methods for Reactor Internals is satisfactory in its present extent in citing an unnamed precursor B & W 205 Subassembly nuclear power plant to be the prototype and in citing conformance with Regulatory Guide 1.20.
However, provide as well a commitment to keep the staff informed regarding the progress of the prototype and the degree of congruity. Also provide a commitment to perform prototype testing at WPPSS 1 as defined in Regulatory Guide 1.20, if a suitable prototype can not be identified.
4.
While the reporting of numerical model parameters and numerical results is reserved for the FSAR, nevertheless describe in the PSAR the methods of analysis and the correlation of the vibration aspects of reactor internals response to flow induced phenomena as predicted and as measured. A program which is acceptable to the staff is presented in Attachment 2, entitled: "Preoperational Vibration Assurance Program for Reactor Internals."
5.
Provide an acceptable response to co==ent 3.20 regarding an operability assurance program for ASME Code Class 2 and 3 active pumps and valves.
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6.
The description of the design and installation criteria for ASME Code Class 2 component pressure-relieving devices in PSAR 3.9.2.5 is not completely adequate. Provide assurance that a sequence of valve operations will be postulated for valves on a common header such as to produce the greatest ratio of estimated instantaneous stress to allowable stress at any point, independent of the relative set-points of the valves.
Simultaneous discharge should be one of the candidates for this most severe condition.
Indicate whether any safety and relief valves discharge into closed systems.
Also provide assurance that the loads to be used in the stress analysis will include the SSE loads along with the fluid dicch rge Iceds and tha normal condition loads.
7.
The stress limits for reactor internals for the faulted plant condition provided in PSAR 4.2.2.4.6 correspond to a design procedure described in ASME III Appendix F combining component inelastic analysis and elastic system analysis followed by a check of the elastic analysis for effects of component plastic deformation.
Specify whether it is your intent to employ this type of analysis, including the iterative modification to the elastic analysis when the need for such is indicated. If other types of analysis are planned in this instance, provide justification.
8.
Supplement Section 1.5 or 3.9 of the PSAR by providing a detailed description of the program to implement a loose parts monitoring system
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should include the types, number, and locatio'n of sensors to be irstalled, the logic to detect the occurrence of loose parts, the devices required to perform the monitoring functions, and the assessment of the system capability.
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5.0 Reactor Coolant System and Connected Systems
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1.
Provide responses to comments 5.1 and 5.2 regarding the stress criteria for ASME Code Class 1 active valves, and active pumps if any, and regarding the operability assurance program for said components.
2.
Provide a response to comment 5.3 regarding the acceptability of computer program analysis of mechanical components and equipment.
3.
In PSAR 5.2.2.2, reference is made to allowable stress limits in table 5.2-6.
This appears to be an incorrect reference. Please provide a clarification or a correction.
4.
With respect to PSAR 5.2.1.16 regarding analytical methods for stresses in pumps and valves (ASME Code Class 1), provide the stress allcwsbics to 'ue used Lu assure mecn' anical/ pressure integrity.
5.
With respect to the stress limits for Code Class 1 pressure vessels in PSAR table 5.2-4, justify any departures from the criteria of Regulatory Guide 1.48 and indicate the type of analysis (such as elastic / inelastic, for example) planned to be employed with the tabular stresses for the faulted plant condition.
6.
Past experience with various types of rotating machinery indicates that the condition of greatest hardship for a bearing is not necessarily the condition of greatest bearing load.
In PSAR 5.2.1.17 provide assurance that conditions other than those producing the greatest bearing loads will be examined for possible anomalies, including self-excited vibration.
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Also specify whether the 20% or more critical speed margin designed into the reactor coolant pumps is based upon:
(a) nominal speed or a design speed which includes possible temporary overspeed, (b) analysis of critical speed assuming that bearing supports are immovable or are characterized by mechanical impedance or flexibility.
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PIPE WHIP ANALYSIS Analyses are required to assure that pipe motion caused by the dynamic effects of postulated design basis breaks will not impact or overstress any structures, systems or components important to safety to the extent that their safety function is inpaired or precluded. The analysis methods used should be adequate to determine the resulting loadings in terns of:
a.
the kinetic energy ot nomentum induced by the impact of the whipping pipe, if unrestrained, on a protective barrier or a component important to safety, b.
the dynamic response of the restraints induced by the impact and rebound if any, of the ruptured pipe.
The basis used to deternine the magnitude of jet thrust force as required in dynamic analysis should be provided.
The methods of dynamic analysis specified in II and III are acceptable provided the following associated criteria are met:
I.
Pipe Uhip Dynamic Analysis Criteria a.
An analysis of the pipe run or branch chculd be performed for each longitudinal and circunferential postulated rupture at the design basis break locations.
b.
The loading condition of a pipe run or branch prior to postulated rupture in terms of internal pressure, temperature, and stress state should be those conditions associated with reactor operating condition (normal and upset),
c.
For a circumferential rupture, pipe whip dynamic analysis need only be performed for that end (or ends) of the pipe or branch which is conne,cted to a contained fluid energy reservoir having a sufficient capacity to develop a jet stream, d.
Dynamic analysis methods used for calculating the piping or piping /
restraint system response to the jet thrust developed following postulated rupture should adequately account for the effects of:
(1) mass inertia and stiffness properties of the system, (2) impact and rebound (if any ef fects as permitted by gaps between piping and restraint)
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(3) elastic and inelastic deformation of piping and/or restraint and (4) limiting boundary conditions.
e.
The allowable design strain limit for the restraint should not exceed 0.5 ultimate uniform strain of the materials of the restraints. The method of dynamic analysis used should be capable of determining the inelastic behavior of piping-restraint system response within these design limits.
f.
A 10% increase of minimum specified design yield strength (Sy) may be used in the analysis to account for strain rate effects.
g.
Dynamic analysis methods and procedures should consist of:
(1) a representative mathematical model of the piping systen or piping / restraint system, (2) the analytical method of solution selected, (3) selutions for the nost severe response among the design basis breaks analyzed, 4
(4) solutions with demonstrable accuracy or justifiable conservatism.
h.
The extenr ni marha ar4re! modeling and analyci cheuld bc gaecrnad by the method of analysis selected among those specified by these criteria.
II.
Acceptable Dynamic Analysis for Restrained Pinine Systems Acceptable Models for Analysis for ASME Class 1, 2 and 3 piping systems a.
are:
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(1) Lumped-Parameter Analysis Model; Lumped mass points are interconnected by springs to take into account inertia and stiffncss effects of the system, and time histories of responses are conputed by numerical 4
integration to account for gaps and inelastic effects.
(2) Energy-Balance Analysis Model; Kinetic energy generated during the first quarter cycle movement of the ruptured pipe as imparted to the piping / restraint system through impact is converted into equivalent strain energy. Deformations of the pipe and the restraint are compatible with the level of absorbed energy. For applications where pipe rebound may occur upon impact on the restraint an additional amplification factor of 1.5 should be used to establish the magnitude of the forcing function in order to determine the maximum reaction force of the restraint af ter the first quarter cycle of response. Amplification factors other than 1.5 may be used if justified by more detailed dynamic analysis.
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O (3) Static Analysis Model - The jet thrust force is represented by a conservatively amplified static loading, and the ruptured system is analyzed statically. An amplification factor of 3 can be used to establish the magnitude of the forcing function if the piping and restraint system remain clastic. liovever, a factor based on selection of a conservative value as obtained by com-parison with the factors derived from detailed dynamic analysis performed on comparable systems is also acceptable.
III. Acceptable Dynamic Analysis for Unrestrained Pipe Whip Lumped-Parameter Analysis Model as stated in II.a(1) is acceptable.
a.
b.
Energy-Balance Analysis Model as stated in II.a(2) is acceptable.
The energy absorbed by the pipe deformation may be deducted from the total energy imparted to the system.
The assumptions used to guide th'e mechanism of pipe movement should c.
be' justified to be conservative.
d.
The results of analysis should be expressed in terms compatible with the approach used for verifying the design adequacy of the impacted structure.
IV.
Flow Thrust Force The time function of the thrust force induced by Jct flow at the a.
design basis pipe break location should consider:
(1) the initial pulse, (2) the thrust dip, and (3) the transient f u'nc tion,
b.
A steady state fcircing function can be used when conditions as specified in e below are met.
The function should have a magnitude not less than T = KpA where p = system pressure prior to pipe break A = pipe break area, and K = thrust coefficient.
Acceptable K values should not be less than the following:
(a) 1.26 for saturated steam, water and steam / water mixture (b) 2.00 for subcooled water-nonflashing, i
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A pulse rise time not exceeding one millisecond should be used for c.
9 the initial pulse, unless longer crack propagation times or rupture opening times can be substantiated by experimental data or analytical theory.
d.
The transient function should be provided and justified. The shape of the transient function, IV a.(3) above, should be related to the capacity of the upstream energy reservoir, including source pressure, fluid enthalpy, and the capability of the reservoir to supply high energy flow stream to the break area for a significant interval.
The shape of the transient function may be modified by considering the break area and the system flow conditions, the piping friction losses, the flow directional changes, and the application of flow limiting
- devices, e.
The jet thrust force may be represented by a steady state function, b above, provided the following conditions are met:
(1) The transient function, IV a.(3) above, is monotonically diminishing.
(2) The energy balance model or the static model is used in the analysis.
In the former case, a step function amplified to the magnitude as indicated in II.a(2) is acceptable.
(3) The energy approach is used for the impact effcces of the unrestrained piping.
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9 Attachment PREOPERATIONAL VISRATION ASSUPM:CE PROGIVl! FOR RFACTOP, I';TERNALS A preoperational vibration assurance program for reactor internals should be required. The program should conforn with the requirements of Regula-tory Guide 20
" Vibration Measurements on Reactor Internals." If the elements of the program differ from the procedures recommended by Regula-tory Guide 20, the basis for such differences should be provided.
In adSition, the following guidelines concerning the analytical solutions necessary to predict vibrations for the prototype plants should be followed:
1.
The analytical results of the vibration prediction for a prototype reactor should consist of the following:
A.
Dynamic responses to operating transients at critical locations of the internal structures should be determined and, in particular, at the locations where vibration sensors will be mounted on the reactor internals. For each location, the maximum response, the modal contribution to the total response, and the response causing the naximus stress amplitude should be measured.
B.
The dynamic properties of internal structures, including the natural frequencies, the dominant mode shapes and the damping factors should be characterized.
If analyses are performed on component structural element basis, the existence of dynamic ecupling c:cng cc;poncat structure eleuents should be invesciga ec.
C.' The response characteristics, such as their relationships to the hydrodynamic excitation forces, the flow path configuration, the coolant recirculation pump frequencies, and the natural frequencies of the internal structures should be identified.
D.
Acceptance criteria of allowable responses should be established including the location of vibration sensors.
Such criteria should be related to the ASME code allowable stresses or strains and limits of deflection amplitudes established to preclude loss of function with respect to the reactor core structures, fuel assen-blies.
2.
The forcing functions should account for the effects of transient flow conditions and the frequency content. Acceptable nethods adopted to fornulate forcing functions for vibration prediction are as follows:
A.
Analytical Method - Based on acceptable hydrodynamic theories, the appropriate governing differential equations of vibratory notions should be developed and solutions obtained with justified boundary conditions and paranaters. This nethod is acceptable where the geomatry along the fluid flow paths are rathematically tractable.
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B.
plant tests orTest-Analysis Conbinatio which will include thedistribution data), f
- tests, ng functions (e.g. velocity or pressa ned fr urations, and wide variatioeffects of complex flow pat ure C.
characteristicsResponse-Deductinn Method ns of pressure distribution config-s.
as may be deduced from plan-Based on a test data, forcing fun since such functions may should be formulated.t test orof t ctions computational procedures scaled not be the basis for theuniquely repres representative forcing functi and 3.
, the Acceptable ons predictionsmethods employed to should be defined. selection of the are as follows:
obtain dynamic of the forcing functionsForce-response compu responses for vibration A.
ns are and the mathematical model of i are predetermined onacceptable if the charreteristics sentative of the If the forcing functionsreactor internal design.nt B.
epre-methods are acceptable: are (1) A cpectral enalysis of not pre-determined, the foll owing similar design tha tempuuse signals reactor internals may be perfmeasurco tron the amplitude and codal contributions (2) Parameter orced, to predict results from thestudies may be pertinent fo based on composite statisimilar design internalsr extrapolating th 4.
Vibration predictions componenta stics.
or test results differ subshould be verified by test behavior, further revisistantially from the predict d be conducted to improve th results.
on of vibration prediction If the vaIidate the e
e response for predicting responsesacceptability of theagreement with test results analysis should units where confirmatory testsof the prototypeanalytical method as appro and to unit, as well as for other priate are to be conducted.
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