ML19319B895
| ML19319B895 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 07/05/1973 |
| From: | Maccary R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8001290624 | |
| Download: ML19319B895 (4) | |
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JUL 5
'973 R. C. DeYoung, Assistant Director for Pressurized Water Reactors Directorate of Licensing DAVIS-BESSE NUCLEAR POWER STATTON Plant Name: Davis-Besse Nuclear Power Station Licensing Stage: OL Docket Number: 50-346 Responsible 3 ranch and Project Manager: P9Rf4, I. Peltier Requested Completion Date: 7/6/73 Applicant's Response Date Necessary for Completion of Next Action Planned on Project:
N.A.
Description of Response: IIesponse to Westions Review Status: Avaiting Information A review of the information furnished by the applicant in the PSAR and amendments through revision 1, amendment /15, has been completed by the Mechanical Engineering Branch. Areas in which additional information is required are identified in the enclosure.
Original siJned by it R. Mace.uy R. R. Maccary, Assistant Director for Engineering Directorate of Licensing
Enclosure:
Request for Additional Information cc w/ encl:
S. H. Hanauer, DRTA J. H. Hendrie, L A. Schwencer, L J. P. Knight, L I. A. Peltier, L R. J. Bosnak, L Docket File 50-346 L, Reading File ec w/o encl:
L:MEB File A. Gimmhusso, L W. G. Mcdonald, L
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DAVIS-BESSE NUCLEAR STATION DOCKET NO. 50-346 REQUEST FOR ADDITIONAL INFORMATION
_3. 6 Protection Against Postulated Pipe Rupture 1.
Describe the functional difference between a pipe rupture restraint and a pipe whip restraint as stated in 3.6.2.5.11.
Describe the configuration and design criteria of a rupture restraint.
2.
(a) Provide a diagram for each of the systems identified in Table 3-5 i
that is postulated to rupture and for which restraint is necessary.
j (b) Indicate the break locations and the location of the restraints and their constrained directions on the diagram, and provide the criteria utilized to select break locations. Part C of Regulatory Guide 1.46 contains an acceptable method of determining locations for postulated pipe breaks inside containment. The same criteria may also be applied outside containment to determine break locations.
Justify the use of alternate criteria.
(c) Provide the configuration of representative pipe whip restraints.
(d) For high energy systems outside of containaent, indicate the i
supplemental protection required to protect systems and structures necessary for the safe shutdown of the plant from the environmental ef f ects, including j et impingement, of through wall pipe cracks.
3.
Reconcile the pipe whip restraint design criteria differences which now appear in Sections 3.6.2.5.4, 3.6.2.5.5, 3.6.2.5.12, with respect to design allowable stress and strain. An increase of 10% in the specified minimum yield strength to account for strain rate effects 1
is acceptable, but an increase of 20% is not.
4.
The thrust coefficients and the analysis =ethods used for obtaining dynamic effects to pipe whip restraints are inadequate and apparently l
use different design bases inside and outside containment as presented in Section 3.6.2.
An acceptable method for pipe whip analysis is provided in Attachment A.
Justify the use of alternate procedures and methods.
5.
Provide the basis and a more detailed description concerning the formulation of the jet impingement force acting on an adjacent object 3
from the postulated pipe rupture, including loading distribution on the impinged surface.
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6/4/73 Attachment A MEB REGULATORY PO3ITION 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 impaired or precluded. The analysis methods used should be adequate to determine the resulting loadings in terms of:
the kinetic energy or momentum induced by the impact of the whipping a.
pipe, if unrestrained, on a protective barrier or a component impor-tant 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 determine 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 Whio Dynamic Analysis Criteria a.
An analysis of the pipe run or branch should be performed for i
each longitudinal and circumferential postulated rupture at the i
design basis break locations.
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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 connected to a contained fluid energy reservoir having a sufficient capacity to develop a jet stream.
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d.
Dynamic analysis methods used for calculating the piping or
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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, i
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(2) impact and rebound (if any) effects as permitted by gaps between piping and restraint.
(3) clastic and inelastic deformatida of piping and/or restraint and (4) lL=iting 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
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capable of determining tne inelastic behavior of piping-restraint system response within these design limits.
f.
A 10% increase of minimum specified design yield strength (S )
y 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 system or piping / restraint system, (2) the analytical method of solution selected, (3) solutions for the most severe response among the design basis breaks analy7.ed, (4) solutions with de=enstrable accuracy or justifiable conservatism, h.
The extent of mathe=atical modeling and anal'ysis should be governed by the method of analysis selected among those specified by these criteria.
II.
Acceptable Dynamic Analysis for Restrained piping Systems a.
Acceptable Models for Analysis for ASM2 Class 1, 2 and 3 piping systems are:
4' (1) Lumped-Parameter Analysis Model; Lumped =sss points are inter-connected by rprines to take into account inertia and stiffness effects of the system, and time histories of responses are i
computed by numerical integration to account for gaps and in-elastic effects.
(2) Energy-Balance Analysis Model; Kinetic energy generated during the first quarter cycle =ovement of the ruptured pipe as im-parted to the piping / restraint system through i= pact is converted into equivalent strain energy. Defor=ations of the pipe and the O
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restraint are compatible with the level of absorbed energy.
For applications where pipe rehaund may occur uoan 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 after the first quarter cycle of response. Amplification factors other than 1.5 =ay be used if justified by more detailed dynaode analysis.
(3) Static Analysis Model - The jet thrust force is represented by a conservatively amplified static loading, and the ruptured system is analyzed statically. The amplificatilyn fsetor used to establish the magnitude of the forcing function should be based on selection of a conservative value as obtained by comparison with the f actors derived from detailed dynamic analysis performed on comparable systems.
III. feceptable Dvnamic Analysis for Unrestrained pine Whip Lumped-Parameter Analysis Model as stated in II.a(1) is acceptable.
a.
.6 b.
Energy-Balance Analysis Model as stated in II.a(2) is acceptable.
The energy absorbed by the pipe deformacien may be deducted from the total energy imparted to the system.
The assumptions used to guide the 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
. I a.
The time function of the thrust force induced by jet flow at the design basis pipe break location should consider:
(1) the initial pulse, (2) the thrust dip, and (3) the transient function.
b.
A steady state forcing function can be used when conditions as specified in e below are met.
The function should have a =agnitude not less than T=Kg 4
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. v. 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 subecoled water-nonflashing.
c.
A pulse rise ti=e not exceeding one =illisecond should be used for the initial pulse, unless longer crack propagation times or rupture opening times gcan be substantiated by experimental ' ta or analytical theory.
d.
The transient function should be provided and justified. The shape of the transicn functicn, 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 lessas, the flew directional ~ changes, and the application or flow limiting devices.
e.
The jet thrust force may be represented by a steady state function, b above, provided the following ccnditions are met:
(1) The transient function, IV a. (3) above, 'is sonotonically 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 acceptabic.
(3) The energy approach is used for the impact effects of the unrestrained piping, i
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9 3.9 Mechanical Systems and components 1.
Clarify Table 3-10 with regard to the use of Code Cases for Class 2 and 3 components.
The entry "ncne" appears in Table 3-10 in the Code Case column for several systems, but the balance of the column is blank. The use of individual Code Cases tequires specific approval by the Commission in accordance with 10 CFR 50.55a (refer to (a)(2)(ii) and footnote 6 of the regulation). Complete che table indicating the cases used for each system as appropriate.
2.
The design loading combinations and stress limits for the various plant operating conditions for ASME Class 2 and 3 components have not been completed in Section 3.9.2 or Table 3-10.
Regulatory Guide 1.48 provides a summary of current acceptable limits. Provide these design criteria for the Davis-Besse plant. Justify any limit which exceeds that specified in the Guide, and demonstrate the adequacy of the design safety margin selected.
3.
Describe the measures to be taken which will assure that Class 1, 2 and 3 (seismic Category I) active pumps and valves will operate under plant conditions when their safety function must be relied upon to effect a plant shutdown or to mitigate che consequences of an accident.
The material in 5.2.1.16 and 3.9.2.6 is not definitive enough to be acceptable in the area of functional testing.
l 4.
The description of the design criteria for safety / pressure relief valve stations in dections 3.2.2 ana J.9.2.d is not serinitive enougn for I
acceptance.
Indicate how the method of analysis has included consid-eration of the reaction force, dynamic effects of the valve opening time, effect of the sequence of valve openings, including simultaneous discharge, to produce the highest caxi=wm instantaneous value of stress.
i 5.
In Section 3.9.1.3, only the topical report BAW-10051 is referenced to confirm the design adequacy of reactor internals to withstand the flow-induced vibration during normal operating. A concurrent reference to topical reports BAW-10037, 10038 and 10039 should be included for a complete verification of the valid prototype preoperational vibration testing.
6.
Justify that the seismic disturbances of the reactor internals at the Davis-Besse plant are less severe than the seismic input used in the topical report BAW-10008, Part I, Rev. 1 and BAW-10041. A comparison of response spectra at the component support locations should be provided.
In addition, a list of analysis results including maximum stresses or deformations in the reactor internals due to LOCA and SSE loadings as well as their comparison to the allowable values should be provided, i
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3.10 Seismic Design of Category I Instrumentation and Electrical Eculpment 1.
Provide a summary of seismic testing results of those electrical equip-ments which are not included in the topical report RAW-10003.
Infor-mation should include the following:
(a) Describe briefly the testing facilities, including functional capability.
(b) Provide a list of equipment (devices or assemblies) and supporting structures tested.
(c) Identify the type of testing input, including intensity level, frequency content,. number of. axis, input. duration and time history sketches of the typical input. The validity of such testing input should be demonstrated.
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(d) Describe the number, type, and location of monitoring sensors on each equipment and document the =aximum response recorded.
(e) Identify whether devices were tested in operating condition during the testing of assemblies or supporting structures (i.e. panels and racks).
(f) Identify whether devices were mounted during the testing of assemblies or supporting structures and demonstrate the validity of any test? corducted withcut the devices (cr suitabic substitutas) or with the mounted devices in inoperative condition.
(g) Describe frequency finding testing, including sweep rates and amplitude used. Provide a su= mary of the frequency finding test results.
(h) In the event analyses were used for determining the testing input, provide a description of the analytical methods and procedures, including sketches of the mathematical models used.
(1) In the event testing was replaced by analyses, provide justification for assuring the proper functioning of the equipment during the DBE event.
(j) Document and discuss any malfunctioning occurring during the testing.
2.
Verify that the response of c., binet assemblies at various instrument or device mounting locations due to Safe Shutdown Earthquake disturbances are less than ig, the device testing input level specified in BAW-10003.
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l 4.0 Reactor, Mechanical Design _
I 1.
Identify which of the three prototypes control rod drive assemblies discussed in B & W topical BAW-10029 will be utilized for Davis-Besse, and describe any differences from the design described in the topical j
report.
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m 5.0 Reactor Coolant System 1.
The design criteria for settinz stress levels of Class 1 active and non-active valves (differentiate between standard design rated and design by analysis types, as appropriate) and active pumps associated with the loading combinations of the emergency and faulted operating conditions requires more definition than given in Section 5.2.1.7 of the FSAR. The levels of maximum stress specified in your design requirements for these components to cover these combined loads should be given in the FSAR. A summary of the currently accepted limits appears in Sections C2 through C5 of Regulatory Guide 1.48.
Provide justification for exceeding any of the limits specified in the Guide, and demonstrate the adequacy of the design safety margins selected.
2.
(a) Specify which of the three faulted stress limit alternatives
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Pressure Boundary components.
(b) Specify and justify the values selected of ultinate material strength at temperature used in the faulted limit analysis.
3.
Reconcile the statement regarding the non-use of plastic instability methods with elastic system dynamic analysis stated in Section 5.2.1.9, and the plastic instability limits specified in Table 5-12.
Indicate which of the alternate linit criteria in the table is used for what specific analysis.
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