Code Manual for CONTAIN 2.0 - Federation of American Scientists

for the Sequoyah plant given in Chapter 15 includes DCH modeling that conforms closely to the
standard input prescription described in Section 13.3.2.2. In addition, a hardcopy listing of an input
file that was used in the analysis of the Zion-geometry Integral Effects Test (lET) experiments
[Al194] is given in Reference Was95.
Some of the recommendations made in this section are to be viewed as suggestions only, since any
given problem likely will have features that cannot be taken into account here. These features may
well justi~ substantial departures from our recommendations. In addition, some of our
recommendations are based upon our judgments concerning uncertain DCH-related phenomena
about which knowledgeable investigators may reasonably be expected to disagree. As always in
performing complex CONTAIN calculations, results should be examined carefully to ensure that the
calculated behaviors are physically reasonable, and sensitivity studies are warranted in order to
determine the extent to which the results of interest are sensitive to uncertain input parameters and
uncertain modeling assumptions.
There are two major parts to this presentation. The f~st is given in Section 13.3.2.2 and presents
what is called the standardized input prescription for DCH analyses that was developed in Reference
Wi195. This standardized input prescription does not include a prescription for use of the new RPV
and cavity entrainment models, but it does provide guidance as to how to define debris source tables
for simulating the RPV ejection and cavity entrainment processes. The second major part of this
presentation describes use of the RPV and cavity models (Sections 13.3.2.3 and 13.3.2.4). Note that
when these models are used, the standardized input prescription is still applicable except for those
portions of the standard input that deal with setting up the debris sources. Users of the RPV and
cavity entrainment models should be aware that experience with them to date has been very limited
and that they can behave in complex ways; it is especially important to check the results to ensure
reasonable behavior when using these models. It is recommended that users be familiar with the
results of the assessment of these models that are described in Reference Wi195. Note also that this
assessment concluded by recommending that these models should be used principally on a “friendly
user” basis; i.e., used by analysts who are familiar with DCH phenomenology and who are willing
to assume the responsibility of examining the results for possible unreasonable behavior.
Perspectives Concerning Uncertainties. The discussion of DCH analysis that follows acknowledges
that important modeling uncertainties exist for some of the phenomena involved in DCH. However,
this fact does not mean that the DCH loads calculated by CONTAIN will normally be heavily
affected by a large number of uncertainties, because the results in any given instance will commonly
be insensitive to some of the uncertain phenomena. For example, there are important uncertainties
in the models controlling debris trapping and transport, yet the CONTAIN predictions of
containment pressure rise (AP) and hydrogen production in the Zion- and Surry-geometry IET
experiments were found to be quite insensitive to these uncertainties. ~i195] Typically, the results
of a given analysis will be sensitive to, at most, a small number of uncertain parameters or modeling
assumptions; however, the identity of the more important uncertainties can be different for different
DCH scenarios.
One example of this dependence upon scenario is that the dominant sensitivities maybe different
for compartmentalized versus open containment geometries. Containment geometries me said to
Rev O 13 23 6/30/97