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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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e “compartmentalized” if the principal path <strong>for</strong> debris dispersal from the cavity communicates with<br />

a compartmentalized lower containment, the structures <strong>of</strong> which present additional barriers to debris<br />

transport to the main volumes <strong>of</strong> the containment; the geometry is said to be “open” if the principal<br />

path <strong>for</strong> debris dispersal communicates directly with the containment dome. To date, there is<br />

considerably more experience with analyzing DCH scenarios in compartmentalized geometries than<br />

in open geometries.<br />

The impact <strong>of</strong> any given uncertainty on the results <strong>of</strong> DCH calculations can depend strongly upon<br />

the initial and boundary conditions <strong>of</strong> the scenario <strong>of</strong> interest. It is there<strong>for</strong>e impossible to give a<br />

quantitative estimate <strong>of</strong> the magnitudes <strong>of</strong> these uncertainties that would be applicable to all DCH<br />

analyses. In some cases, there<strong>for</strong>e, the discussion in Section 13.3.2.2 includes suggested sensitivity<br />

calculations. These recommendations are designed to provide the user with a reasonable<br />

understanding <strong>of</strong> the uncertainty <strong>for</strong> the particular case at hand.<br />

To date, there has been only limited application <strong>of</strong> the approaches suggested hereto nuclear power<br />

plant (NPP) analyses. Hence, some <strong>of</strong> the suggestions <strong>of</strong>fered must be considered tentative.<br />

13.3.2.2 The Standard Input Prescription <strong>for</strong> DCH Calculations. This section presents the<br />

standardized input prescription <strong>for</strong> DCH analysis that was reported in References Wi195 and Pi195.<br />

It discusses how to define debris source tables to simulate RPV ejection and cavity entrainment<br />

processes.<br />

13.3.2.2.1 Philosophical Basis and Purpose <strong>of</strong> the Standard Prescription. As elsewhere in<br />

<strong>CONTAIN</strong>, the design philosophy <strong>for</strong> DCH modeling has been to provide mechanistic modeling <strong>for</strong> ~<br />

phenomena which are sufficiently well understood to justify a defensible mechanistic model, and to<br />

provide simpler or parametric models with flexible input options <strong>for</strong> phenomena that are not well<br />

understood, or that cannot be represented fully within the limitations imposed by the basic lumpedpararneter,<br />

control-volume architecture <strong>of</strong> the <strong>CONTAIN</strong> code. When combined with the<br />

complexity <strong>of</strong> DCH phenomenology, this philosophy has led to provision <strong>of</strong> a large number <strong>of</strong> input<br />

and modeling options <strong>for</strong> DCH analysis. This flexibility in <strong>CONTAIN</strong> DCH modeling is currently<br />

viewed as being essential in order to permit the user to study uncertainties in the results <strong>of</strong> DCH<br />

calculations, as well as to permit the user to take advantage <strong>of</strong> any fiture refinements in DCH<br />

understanding. However, it obviously presents problems with respect to quality control and<br />

consistency, if some type <strong>of</strong> control on DCH input is not available. Hence an important goal <strong>of</strong> the<br />

<strong>CONTAIN</strong> DCH assessment ef<strong>for</strong>t was to develop a standardized input prescription <strong>for</strong> DCH<br />

calculations.<br />

The standardized input prescription was defined <strong>for</strong> a number <strong>of</strong> purposes. These include providing<br />

guidance <strong>for</strong> code users and providing a means <strong>for</strong> allowing investigators working independently to<br />

obtain comparable results when consistency is desired. On the other hand, the standard prescription<br />

definitely is not <strong>of</strong>fered as a “cookbook” that must be followed, or that will guarantee good results<br />

if it is followed; it is not an “<strong>of</strong>ficial” prescription endorsed by the United States Nuclear Regulatory<br />

Commission or any other standard-setting body. It is only being <strong>of</strong>fered by the <strong>CONTAIN</strong> project<br />

as a suggested starting point or guideline. The standard prescription has potentially important<br />

limitations, and sensitivity studies to explore uncertainties are likely to be a part <strong>of</strong> any study that<br />

Rev O 13 24 6/30/97

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