Code Manual for CONTAIN 2.0 - Federation of American Scientists

2) Medium = prediction of prime quantity to within 20-40% and trends predicted; and,
3) Low = prediction of prime quantity less than 50% and only a few trends predicted.
C.3 Individual CV&A Summaries
C.3. 1 Atmosphere Thermal Hydraulics and Intercell Flow
Table C-3 presents a summary of the validation and assessment studies for the atmosphere thermal
hydraulics and intercell flow models in CONTAIN. One area of specific concern for model
adequacy was whether CONTAIN could predict the observed stable stratifications that typically
occur for elevated source injection locations within a containment. A review of the performance of
the code in the ISP-29 test seemed to suggest that CONTAIN 1.11 could not handle this class of
problems. As a result of experiences like these a code improvement effort was undertaken to address
the problem of overmixing in lumped parameter codes. A hybrid flow solver was developed for
CONTAIN to solve this problem of overrnixing for stably stratified containment. [Mur96] A
comparison of data and code results for the light gas distribution in the upper dome of the HDR
facility for the ISP-29 testis shown in Figure C-1. The improvement in the results for the hybrid
flow solver in CONTAIN 1.2 is clearly evident. This case shows how the CV&A procedure can
identifj shortcomings in code performance, provide guidance for additional code development, and
finally establish confidence in a revised model.
C.3.2 Heat and Mass Transfer
Table C-4 presents a summary of the validation and assessment studies for the heat and mass transfer
models in the CONTAIN code. Energy transport by condensation/evaporation processes are very
important to the predictions of atmospheric pressure, temperature, and gas composition. The
modeling approach for such processes is based on diffusion boundary layer theory in conjunction
with a heat and mass transfer analogy (HMTA). Table C-5 presents additional validation studies that
have been completed for this approach, in addition to the CONTAIN-specific efforts described in
Table C-4. An example of the type of experimental comparison used to show the adequacy of the
modeling is the comparison between the experimentally derived heat transfer coefficient for
condensation and the CONTAIN blind post-test results for the LACE LA-4 experiment, as shown
in Figure C-2. A code-to-code comparison exercise between CONTAIN and the Purdue finite
difference boundary layer code was recently completed. This comparison showed that the
CONTAIN treatment gives good results for high evaporative mass transfer rates when simulating
the evaporation occurring in an asymmetrically heated vertical channel cooled by a falling water
film. The CONTAIN comparisons for high condensation rates in condenser tubes also show good
agreement with data, as illustrated in Figure C-3. Agreement such as this shows not only the
adequacy of the HMTA modeling methods, but also the appropriateness of the correction factors
used to modify the HMTA at high mass fluxes. Recent ALWR test comparisons involving
condensation/evaporative processes have also confirmed that the HMTA, as implemented in
CONTAIN, provides very good accuracy for mass transfer in both free and forced convective
regimes.
Rev O c-5 6/30/97