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Code Manual for CONTAIN 2.0 - Federation of American Scientists

Code Manual for CONTAIN 2.0 - Federation of American Scientists

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11.2 Safetv Relief Valve (SRV) Model<br />

The SRV model deals with external sources <strong>of</strong> gases, coolant, aerosols, and fission products in<br />

aerosol <strong>for</strong>m that are introduced into a cell at a fixed elevation and require partitioning between the<br />

atmosphere and pool. The nature <strong>of</strong> the partitioning depends on whether the source elevation is<br />

located above or below the pool surface. If the source is submerged, gas-pool equilibration and<br />

aerosol scrubbing are modeled. In the gas-pool equilibration modeling, any coolant liquid is<br />

removed, complete temperature equilibration, and nearly (95%) complete vapor pressure<br />

equilibration is assumed. The scrubbing <strong>of</strong> aerosols and fission products is modeled according to<br />

either the SPARC or the SCRUB model discussed in Section 7.7. If the source is not submerged,<br />

coolant phase separation is modeled under the assumption that the source volume expands<br />

isenthalpically until the source materials reach the local pressure. The coolant liquid remaining after<br />

expansion is directed to the pool, and the coolant vapor, gases, aerosols, and fission products are<br />

directed to the atmosphere. Although there is no consideration in the SRV model <strong>of</strong> the fact that<br />

some entrainment <strong>of</strong> the liquid could occur, the user has the option to calculate the entrainment <strong>of</strong><br />

the liquid separately and then allocate the entrained liquid fraction to an atmosphere source. In<br />

contrast to SRV sources, the materials specified in an atmosphere source, with the possible exception<br />

<strong>of</strong> DCH materials, are directed to the atmosphere without partitioning.<br />

The gas-pool equilibration modeling <strong>for</strong> submerged SRV sources is discussed in Section 11.2.1. The<br />

coolant phase separation modeling <strong>for</strong> an SRV source that is not submerged is discussed in Section<br />

11.2.2.<br />

11.2.1 Gas-Pool Equilibration <strong>for</strong> Submerged SRV Sources<br />

This section discusses the gas-pool equilibration model <strong>for</strong> submerged external sources. These are<br />

assumed to equilibrate in temperature with the pool. In addition if the BOIL option has been<br />

specified <strong>for</strong> the pool, these sources are assumed to be nearly (95%) equilibrated with respect to the<br />

pool vapor pressure. However, if the BOIL option has not been specified, coolant vapor and any<br />

homogeneously dispersed coolant liquid in the source will be completely retained in the pool.<br />

The SRV model is activated through the SRVSOR keyword described in Section 14.3.4. Source<br />

tables are used in this model to describe the rates <strong>of</strong> introduction <strong>of</strong> the various materials. The SRV<br />

discharge is assumed to be at the elevation above pool bottom specified by the ELESRV keyword<br />

in the SRVSOR input block. Although the model is intended primarily <strong>for</strong> modeling SRVS,it could<br />

be used in any situation in which the source partitioning between atmosphere and pool is appropriate.<br />

A unique feature <strong>of</strong> SRV aerosol sources is that the lognormal size distribution parameters <strong>for</strong> the<br />

aerosol source can be specified in the source table as a finction <strong>of</strong> time. Jf given, these values are<br />

used <strong>for</strong> the aerosol source instead <strong>of</strong> the global size distribution parameters defined <strong>for</strong> the aerosol<br />

component in the global AEROSOL block (Section 14.2.5).<br />

The user should take care to ensure that the gas, aerosol, and fission product source table input as<br />

described in Section 14.3.4 are consistent. For example, a finite aerosol source rate would not make<br />

sense unless there is a supporting gas source rate to convey the aerosols into the pool. A finite<br />

fission product source rate also would not make sense unless the supporting aerosol source rate <strong>for</strong><br />

Rev O 11 19 6/30/97

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