ML19220B898
| ML19220B898 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 12/09/1975 |
| From: | Kniel K Office of Nuclear Reactor Regulation |
| To: | Arnold P METROPOLITAN EDISON CO. |
| References | |
| NUDOCS 7904270620 | |
| Download: ML19220B898 (12) | |
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DCLCSCPE ATEPE7f CF TEE FFCELEM In the unlikely event of a FWR primary coolant srter pipe rupture in the inrediate vicinity cf the reacter vessel, transient leads cricinatino frcm three principal causes will be exerted en the reactor vessel suppcrt system.
'Ihese are:
1.
Blowdcwn jet forces at the locaticn of the rupture (reaction forces),
2.
Transient differential pressures in the annular recicn between the vessel and the Shield, and 3.
Transient differential pressures across the core berrel within the reacter vessel.
The blcwdcwn iet forces are edecuately understcod and desicn crecedures are available to account for them.
Both cf the " differential pri ;sure" forces, however, are three-dirensicca.1 rd tire dependent and tecuire scphisticated analytical precedures to tra
.ste them into Iceds actino on the reactor vessel support system. All of the loads are resisted by the inertia and by the suppcrt verbers and restraints of other ccrpenents of the primary ecolant system includino the reactor pressure vessel suppcrts.
'Ite transient differential pressure actinc externally en the reacter vessel is a result of the ficw of tre blcwdcwn effluent in the reactor cavity.
'Ibe racnitude and tre tire dependence cf the resultino forces depends en the nature and the size of the cipe rupture, the clearance between the vessel and the shield and the size and locaticn cf the vent cpenines leadinc frcr the cavity to the containrent as a whcle.
For scre time refined analytical methods have been available for calculatinc these transient differential pressures (multi-node analyses).
'Ihe results of sucn analyses indicate that the consecuent leads en the veFsel suCrort system Calculated by less sephisticated nethcds ray nct te as ccnservative as cricinally intended for earlier desiens. Attachrent 1 to this enclosure prcvides for your information a list of informatien recuests for which rescenses could be needed for a prcper assessment of the irpact of the cavity differential cressure en the desien adecuacy cf the vessel suppcrt syster for a pcwer plant.
Sm=FE9 84-004
. The centro 11ine Icads for desien purposes, however, a: pear in typical cases to be these associated with the internal differential pressures acrcss the core barrel. The internally cenerated Icads are due to a rcrentary differential pressure which is calculated te exist across the core barrel when the pressure in the reactor annular recien between the core barrel and wssel well in the vicinity of the ructured pipe is assured to rspidly decrease to the saturatien pressure of the primary coolant due to the cutflow of water. Althouch the depressurization wave travels rapidly around the core barrel, there is a finite pericd of tire during whicf1 the pressure in the annular recien cpposite the break locaticn is assured to remain at, er near, the original reacter cceratinc pressure.
Thus, transient asynretrical forces are exerted en the core barrel and the vessel wall which ultirately result in transient 1 cads en the supcort systers.
These are the 1 cads which were underestimated by the licensee crigirally reportire this crebler and which may be underestimated in other cases.
They are therefore of ceneric concern to the staff. to this erclcsure provides for ycur informaticn a list cf informaticn recuests for wnich resperses wculd be needed for a crecer assessment of the i get that the vessel internal differential cressure, in cenjunction with the other ccccurrent leads, could have en the desien edecuacy cf the support syster.
In that there are censiderable differences in the reacter sucpert syster desions for varicus facilities and crchably in the desien margirs provided by the desicners of older facilities, the underestiraticn cf these " differ-ential pressure" loads ray or ray not result in a determinatien that the adecuacy of the vessel sucport syster for a specific facility is cuestien-able. Since local failures in the mssel supports (such as plastic deforratien) do not necessarily lead to the failure of the sucports as an intecral syster, there ray be scre limited reacter vessel action provided that rc further sicnificant consecuences would ensue and the erergency core ccolinc systers (ECCS) wculd be able to ;mrforr. their desicn functions.84-005
~
9 ATTAC: STENT 1 C_0NTAIt! MENT SYSTEMS BRAiiCH nUUEST FOR ADDITIONAL INFORMAT!O.1 In the unlikely event of a pipe rupture.inside major component subccmpartments, the initial blcwdown transient would lead to non-uniform pressure loadings on both the structures and enclosed components.
To assure the integrity of these design features, we request that you perform a compartment multi-node pressure response analysis to provide the following information:
(a) The results of analyses of the differential pressures resulting from hot leg and cold leg (pump suction and discharge) reactor coolant system pipe ruptures within the ra::.i.or cavity and pipe penetrations.
(b)
Describe the nodalization sensitivity study performed to determine the minimum number of volume nodes required to conservatively predict the maximum pressure within the reactor cavity.
The nodalization sensitivity study should :nclude considrration of spatial pressure variation; e.g., pressure variations circumferentially, axially and radially within the reactor cavity.
(c)
Provide a schematic draving showing the nodalization of the reactor cavity.
Provide a tabulation of the nodal net free volumes and interconnecting flow path areas.
(d)
Provide sufficiently detailed plan and section drawings for several views showing the arrangement of the reactor cavity structure, reactor vessel, piping, and other major obstructions, and vent areas, to permit verification of the reactor cavity nodalization and vent locations.
(e)
Provide and justify the break type and area used in each analysis.
h
_2 (f)
Provide and justify values of vent loss coefficients and/or friction
, factors used to calculate flow between nodal volumes.
When a loss coefficient consists of more than one component, identify each component, its value and the flow area at which the loss coefficient applies.
(g)
Discuss the manner in which movable obstructions to vent flow (such as insulation, ducting, plugs, and seals) were treated.
Provide analytical justification for the removal of such items to obtain vent Provide justification that vent areas will not be partially or area.
completely plugged by displaced objects.
(h)
Provide a table of bloadua mass flow rate and energy release rate as a function of time for the reactor cavity d'esign basis accident.
(i)
Graphically show the pressure (psia) and differential pressure (psi) responses as functions nf time for each nod..
Discuss the basis for establishing the differential pressures.
(j)
Provide the peak calculated differential pressure and time of peak pressure for each node, and the design dif?erential pressure (s) for the reactor cavity.
Discuss whether the design differential pressure is uniformly applied to the reactor cavity or whether it is spatially varied.
(Standard Review Plan 6.2.1.2, Subcompartment Analysis attached, provides additional guidance in establishing acceptable design values, for determining the acceptability of the calculated results.)l T-g4-007
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U.S. NUCLEAR. REGULATORY COMMISSION February, 1975 STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.2.1.2 SUSCCMPARTMENT ANALYSIS REVIEW RESPC EIBILITIE_S Primary - Contai.' ment Systems Branen (CSB)
Secondary - Mechanical Engineering Branch (MEB)
Core Performance Branch (CPB)
Auxiliary and Power Conversion Systems BrancP (APCSB)
I.
AREAS OF REVIEW The C58 reviews tne information presented by the applicant in the safety analysis report concerning the deter-ination of tne design differential pressure values for containment sub-ccmcartments. A succompartment is defined as any fully or partially enclosed volume within the primary containment that houses nigh energy piping and wculd limit the flow of fluid to the main containment volume in the event of a postulated pipe rupture within this volume.
A sr. ort-term pressure pulse woulo exis' inside a containment subcomoartment following a pipe ructure within tnis volume. This pressure transient produces a pressure differential across the walls of the subcompart ent whicn reacNes a maximum value generally within the first second after blowdown begins. The magnitude of the peak value is a function of several parameters, wnich include blowdown mass and energy release rates, subcompartment volume, vent area, and vent flow tenavior. A transient oifferential pressure response analysis should te provided for each subcomcartment or group of subcompartments that meets the above definition.
The C5B review includes the manner in ahien the mass and energy release r?te into the brean compart ent aere determined, nodalization of subcomcartments, su0 compartment vent flow behavior, and succomcartment design pressure margins. This incluoes a coordinated review effort witn the CPB. The CPB is res;onsible for the ace';uacy of the blowdown model.
The CSB review of the mass and energy release rates includes the basis for the selection of the pice break site and locaticn within each subcompartment containing a hign energy line and the analytical procedure for predicting the short-term mass and energy release cates.
IN CSB review of the succompartment model includes the basis for the nodalization within each succompartment, the initial thermodynamic conditions within each subcompartment, the nature of eacr. vent flow path considered, and the extent of entrainment assumed in the vent flow mixture. The review may also include an analysis of the dynamic character,istics of ccmconents, such as doors, blowout panels, or sand plugs, that must optn or be rekoved to USNRC STAND ARD REVIEW PLAN stenews re ew e4ene we ereceree fer me o eeace se me omes of = eeeer aseeter me 4enen meef ressene.eee for ene rewow of es-en,to eennn.e, one coerete sewer psents These see _
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Generes es, ease of regesastery are, eures one secsones. Stendere review piene are not euest#tutes for F*Tu* story guedes or tne Cemaname.on a reeventsene one gesageience meta taent at het reewared. The stendere reweew poen esenene are sewed to Aeweseen 2 of me Stendere Forseest one Centent of See ter 8hsekeer Peerer Ptesets. Not en gesteene of the Steneere Ferntet neve e et g reweew seen.
Puedene. Stendere re4*eur Diene unE be rewese. -
. es etereeresse te essentspeede J eernmente esse to renect new enferissetten and eatenence Ceemse of egendere rewteve piene queev be eeteunee bT reewest te me U.S. Meeseer A,
,C freenengton. D.C. 2DERE Attennen: Office of sevesew Reester Ap f
_ ene oesggesteene for waterswenient cred be coneseeres and eneesee case es sent to tne Ofnee of anveneer moector megwee, pen.
O provide a vent flow path, and tne methods and results of components tests performed to demonstrate the valioity of these analyses. The analytical procedure to determine tne 1..s coefficients for each vent flow path and to ::redict the veM maf t flow rates, including flow correlations used to compute sonic and sacsonic flow conditions within a vent, is re-viewed. The design p essure enosen for each subcompartment is also eviewed. On reouest from tne APCSB, the CSS evaluates or performs pressure response analyses for succompartments outside containment.
The ME3 is responsible for review).
the acceptability of the break locations chosen and of the design criteria and provision methods employed to justify limited pipe motion for breaks postulated to occur within Wocompartments (See Standard Review Plan 3.6.2).
II.
ACCEPTANCE CRITERIA 1.
The subcompartment analysis snould incorporate the 'ollowing assumotions:
a.
Break locations and types snould be chosen according to Regulatory Guide 1.46 for subcompartments inside containment and to Brancn Tecnnical Position MES 3-1 (attached to Standard Review Plan 3.6.2) for succoccartments outside contairment.
An acceptable alternate procedure is to postulate a circumferential double-ended rupture of each hign pressure system p.pe in the subcompartment.
b.
Of several breaks postulated on the basis of a, above, the break selected as the reference case for subcompartment analysis should yield the hignest mass and energy release rates, consistent with the criteria for establishing the break location and area.
c.
The initial plant operating conditions, such as pressure, temperature, water inventory, and pcwer level, snould be selected to yield the maximum blow 2cwn conditions. The selected operating conditions will be acceptable if it can be shown that a change of each parameter would result 1.1 a less severe blowdown p ro fil e.
2.
The analytical approach used to compute the mass and energy release profile will e accepted if both the computer program and volume noding of the piping system are similar to those of an aporoved emergency core cooling system (ECCS) analysis. The computer programs that are currently acceptable includa SATAN-VI (Ref. 24), CRAFT (Ref. 23), CE FLASH-4 (Ref. 25), and RCLAP3 (Re' 21), when a flow multtpiier of 1.0 is used with the applicable choked flow correlation. An alternate accroacn, wnich is also acceptable, is to assume a constant blowdown profile using the initial conditions with an acceptable choked flow correlation. When RELAP-4 is accepted by the staff as an operational ECCS blowdown code, it will be acceptable fer succompart-ment analyses.
3.
The initial at.iospheric conditions within a subcomcartment snould be selected to max-imize the resultant differential pressure. An acceptable mocel would 'be to assume air at the maximum allowable temperature, minimum absolute pressure, and zero percent rel-a tive humidity. If the assumed initial atmospheric conditions differ from these, the selected values should be justified.
80 009 6.2.1.2-2
Another mcdel that is also acceptable, for a restricted class of subcompartments, in-volves simplifying the air mccel outlined above. For this mcdel, tne int tlal atmcs-chere within tne subccmpartment is maceled as a ncmogeneous water-steam mixture altn an aver 2ge censity equivalent to the cry air model. This accroacn should ce limited to subccmpartments tnat have choked flow witnin tne vents. However, the aceouacy of this simplified model for sa0 compartments naving primarily suosonic ficw througn the vents nas not been estaclished.
4 Subccmpartment nodalization schemes should be chosen such that there is no sucstantial pressure gradient within a node, i.e., the nadalization scheme should be verified cy a sensitivity study that includes increasing the numcer of noces until tne peak cal-culated pressures converge to small resultant changes.
5.
If vent flow paths are used whien are not immediately available at tne time of pipe rupture, tne follcwing criteria apply:
a.
The vent area and resistance as a functicn of time af ter the creak should be based on a dynamic analysis of the subccccartment press ire response to pipe ruptures.
b.
The validity of the analysis should be succorted by experimental data or a testing program snould be proposed at the construction permit stage that will support this analysis.
c.
The effects of missiles that may be generated during the transient should be considered in the safety analysis.
6.
The vent flow behavior through all ficw paths witnin tne nodalized compartment model snould be based on a homogeneous mixture in thermal equilibrium, with the assumption of 100% water entrainment. In additico, the selected vent critical flow correlation snould be conservative with respect to available experimental cata. Carrently accept-able vent critical 'lcw ccrrelations are tne frictionless Moody" with a multiplier of 0.6 for water-ster.: mixtures, and the thermal noregeneous equilibrium model for ai r-steam-water mixtures.
7.
At the construction permit stage,'a factor of 1.4 should be applied to the peak differential pressure calculated in a manner f:und acceptable to the C58 for the subccmpartment. The calculated pressure multiplied by 1.4 should be considered the design pressure. At the operating license stage, ile peak calculated differential pressure should not exceed the design pressure. It is expected that the peak calcu-lated differential pressure will not be sucstantially different from tnat of the construction pennit stage. However, improvements in the analytical models or changes in the as-built subccupartment may af fect the availaDie margin.
III. REVIEW PROCEDURES
~
The procedures described belcw are followed for the subcompartment analysis review. The reviewer selects and empnasizes material from these procedures as may be appropriate for 84-010 6.2.1.2-3
9 a particular case. Portions of the review may be carried out on a generic Dasis or by adopting the results of previnus reviews of piar.ts with essentially the same subcompart-ent and hign pressure piping design.
The CSB reviews the initial conditions selected for determining the Ass and energy release rate to the subcompartments. These values are ccmpared to the spectrum of allowable opera-tirig conditions for the plant. The CSS will ascertain the adequacy of the assumed conditions based on this review.
The CSB confins with the MEB the validity of the applicanJs analysis of subcompartments containing high energy lines and postulated pipe break locatio.'s, using elevation and plan drawings of the containment showing the routing of lines contoining high energy fluids. The CSB deter nines that an appropriate reference case for subcompartment analysis has been identified. In the event a pipe break other than a double-ended pipe rupture is postulated by the applicant, the MES will evaluate the applicant's justification for assuming a limit 31 displacement pipe break.
The CSB may perfom confimatory an s of the blowdown mass and energy profiles within a succompartment. The analysis is (...e using the RELAP3 computer program (See Reference 21 for a description of this code). The purpose of the analysis is to confim the predic-tions of the mass and energy release rates appearing in the safety analysis report, and to confirm that an appropriate break location has been considered in this analysis. The use of RELAP3 will continee until the RELAP4 computer code has been aporoved Dy the staff as an acceptable blowdown code. At that time, the CSB will replace RELAP3 with RELAI4 for all subsequent analyses.
The CSB detemines the adequacy of the information in the safety analysis report regarding succompartment volumes, vent areas, and vent resistances. If a subcompartment must rely on doors, blowout panels, or equivalent devices to increase vent areas, the CSS reviews the analyses and testing programs that substantiate their use.
The CSB reviews the nodalizatio.a of each subcompartment to determine the adecuacy of the calculational model. As necess", CSB perfoms iterative nadalization studies for sub-compartments to confirr. that suft::1ent nodes have been included in the model.
The CSB compares the initial subcompartment air pressure, temperature, and humidity conoi-tions to the critaria of II, above, to assure that conservative conditions were selected.
The CSB reviews the cases, correlations, and comouter codes used to predict subsonic and sonic vent flow behavior and the capability of the code to *nodel compressible ar.d un-compressible flow. The bases should incluoe comparisons of the correlations to both experimental data and recognizej alternate correlations that have been accep;ed b,y the i ta f f.
84'011 5.2.1.24
Using the nadalization of each subcompartment as specified in the safety analysis recort, the CSS perfoms analyses using one of several available computer programs to determine tre adequacy of the calculated peak differential pressure. The computer program used will depend upon the subcompartment under review as well as the fle4 regime. At the present time, the two programs used by the CSB are RELAP3 (Ref. 21) and CDNTEMPT-L1 (Refs. 7, 3, and 9). A multi-volume computer code is currently under development.
At tne construction pemit stage, the CSB will ascertain that the subcompar+2ent design pressures incl"* appropriate marg 6s above the calcula;ed values, as given in II, above.
iV.
EVALUATDN Fa M '3GS The conclusions rdached on completion of the review of this s;ction are presented in Standard Review Plan 6.2.1.
V.
REFERENCES The references for this plan are those listed in Standard Review Plan 6.2.1, together with the following:
14.
Regulatory Guide 1.46, " Protection Against Pipe Whip Inside Containment."
2a. Standard Review Plan 3.6.2, " Determination of Break Locations and Dynamic Effects Associated with the Postulatad Rupture of Piping," and attached Branch Technical Position ME3 3-1, " Postulated Preak and Leakage Locations in Fluid System Piping Outside Containment."84-012 6.2.1.2-5