ML19221B127
| ML19221B127 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-06.2.1., NUREG-75-87, NUREG-75-87-6.2.1., SRP-06.02.01.02, SRP-6.02.01.02, NUDOCS 7907120464 | |
| Download: ML19221B127 (4) | |
Text
NUREG 75/087 pm REce
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U.S. NUCLEAR REGULATORY COMMISSION
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W;Q'" i STANDARD REVIEW PLAN
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OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.2.1.2 SUBCOMPARTMENT ANALYSIS RUllLW RESPONSIBILITIES Primary - Containment Systems Branch (CSS)
Secondary - Mechanical Engineering Branch (MEB)
Structural Engineering Branch (SEB) l I.
AREAS OF REVIEW The CSB reviews the i' emp ion presented by the applicant in the safety analysis report concerning the detern. lati i of the design 'if f erential pressure values for containment subcompartments. A sub umpartment is definu as any fully or partially enclosed volume within the primary ct ' a i nmen t t ':a'e houses high energy piping and would limit the flow of fluid to the ma i, _ i nN -,
'i"me in *he avent of a postulated pipe rupture within the volume. A short-term rrM 'u' puide we ld e-inside a cont ' ament subcompartment following a pip ru; iu.
tc volume.
Thit pressure tran', ?nt produces a pressure l differential ace,"
t M walt f the sJbc^mpertment which reaches a maximum value general-i ly within the fir,t ia
- c.. t el lowdown begins. The magnitude of the peak value is a function of se eral ta s, which nclude blo down mass and energy release rates, i
v subcompaY tment volume, /e^t area, cnd vent flcw behavior. A transient differential pressure response ai,31y,13 snould be provided for each subcompartment or group of sub-compartments that meets the above defir.ition.
The CSB review includes the distribution of the mass and energy reles,ed into the break compartment, nodalization of subcompartments, subcompartment vent flow behavior, and subcompartment design pressure margins.
l The CBS review of the subcompartment model includes the basis for the nodalization within each subccmpartment, the initial thermodynamic conditions within each subcompart-ment, the nature of each 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 charac-teristics of components, such as doors, blowout panels, or sand plugs, that must open or be removed to provide a vent flow path, and the methods and results of components tests performed to demonstrate the validity of these analysee The analytical procedure to determine the loss coefficients and inertia terms (t/A, ft ) for each vent flow path, and to predict the vent mass flow rates, is reviewed. The design pressure chosen for each subcompartment is also reviewed.
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MEB and SEB are responsible for reviewing the mechanical and structural design of movable and stationary devices provided for vent flow control in subcompartments.
II.
ACCEPfANCE CRITERIA 1.
The initial atmospheric conditions within a 3uDcompartment should be selected to maximize the resultr,t uitterential pressure. An acceptable model would be to a s s o'".
dir at the maximum allowable temperature, minimum absolute pressure, and zero percent relative humidity. If the as3umed initial atmotpheric conditions differ from these, the selected values should be justified.
Another model that is also acceptable, for a restricted class of subcompartments, involves simplifying the air nadel outlined ab >ve.
For this model, the initial atmosphere within the subcompartment is modeled as a homogeneous water-steam mixture with an average density equivalent to the dry air model.
This approach should be limited to subcompartments that have choked flow within the vents.
However, the adequacy of this simplified model for subcompartments having primarily subsonic flow through the vents has not been established.
2.
Subcompartment nodalization schemes should be chosen such that there is no sub-stantial pressure gradient within a node, i.e., the nodalization scheme should be verified by a sensitivity study tP+ includes increasing the number of nodes until the peak calculated pressures converge to small resultant changes. The nodaliza-tion sensitivity study should include consideration of spatial pressure variation, e.g.,
pressure variations circumferentially, axially and radially within the sub-compartment, for use in calculating the transient forces and moments acting on components.
3.
If vent flew paths are used which are not immediately available at the time of pipe rupture, the following criteria apply:
a.
The vent area and resistance as a function of time af ter the break should be based on a dynamic analysis of the subcompartment pressure response to pipe ruptures.
b.
The validity of the analysis should be supported by experimertal data or a testing program should 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.
4.
The vent flow behavior through all flow paths within the nodalized compartment model should be based on a homogeneous mixture in thermal equilibrium, with the assumption of 100% water entrainment. In addition, the selected veni critical flow correlation should be conservative with respect to available experimental
)th[ 22f Rev. 1 6.2.1.2-2
data. Currently acceptable vent critical flow correlations are the "fri nionless Moody" with a multiplier of 0.6 for water steam mixtures, and the thermal homogeneous equilibrium model for air steam water raixtures.
5.
At the construction permit stage, a factor of 1.4 should be applied to the ceak differential pressure calculated in a manner found acceptable to the CSB for the subcompartment, structure and the enclosed components, for use in the design of the structure and the component supports. At the operating license stage, the peak calculated differential pressure should not exceed the design pressure. It is expected that the peak calculated differential pressure will not be substantially different from that of the construction permit stage. However, improvcments in the analytical models or changes in the as-built subcompartment may affect the avail-able margin.
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 applica-tion are contained in the SRP sections corresponding to those branches.
III. REVIEW PROCEDURES The procedures described below are followed for the subcompartment analys: review.
The reviewer selects and emphasizes material from thes< procedures as may be appropriate for a particular case.
Portions of the review may be carried out on a generic basis or by adopting the results of previous reviews of plants with essentially the same subcompart-ment and high pressure piping design.
Upon request from the primary reviewer, the secondary review branches will provide input for the areas of review stated in subsection I.
The primary reviewer obtains and uses such input as required to assure that this review procedure is complete.
The CSB may perform confirmatory analyses nf the blowdown mass and energy profiles within a subcompartment. The analysis is done using the RELAP-4 computer program (see Reference 21 fcr a descriptiva of this code) or the CCMPARE computer program (Reference 34).
The purpose of the analysis is to confirm the predictions 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 CSB determines the adequacy of the information in the safety analysis report regard-ing subcompartment volumes, vent areas, vent resistances, and inertia tarms.
If a subcompartment must rely on doors, blowout panels, or equivalent devices to increase vent areas, or unique flow limiting devices to control vent flows, the CSB reviews the analysis and testing programs that substantiate their use.
The MEB and SEB may also be requested to evaluate the mechanical and structural design of such flow control devices.
The CSB reviews the nodalization of each subcompartment to determine the adequacy of the calculational model. As necessary, CSB performs iterative nodalization studies for sub-compartments to confirm that sufficient nodes have been included in the model _
6.2.1.2-3 Rev. I
The CS3 compares the initial subcompartment air pressure, temperature, and humidity conditions to the criteria given in subsection II, above, to assure that conservative l
conditions were selected.
The CSB reviews the bases, correlations, and computer codes used to predict subsonic and sonic vent flow behavior and the capability of the code to model compressible and incom-pressible flow.
The bases should include comparisons of the correlations to both experi-mental data and recognized alternate correlations that have been accepted by the staff.
Using the nodalization or each subcompartment as specified in the safety analysis re-port, the CSB performs analyses using one of several available computer programs to determine the adequacy of the calculated peak differential pressure. The computer program used will depend upon the subcompartment uncer review as well as the flow regime.
At the present time, the two programs used by the CSB are RELAP-4 (Ref. 21) and COMPARE (Ref. 34).
At the construction permit stage, the CSB will ascertain that the subcompartment design procedures include appropriate marqins above the calculated values, as given in Subsection 11, above.
l IV.
EVALUATION FINDINGS The conclusions reached on completion of the review of this section are presented in SRP Section 6.2.1.
V.
REFERENCES The references for this SRP Section are those listed in SRP Section 6.2.1.
Rev. 1 6.2.1.2-4 14_/
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