Page 114 - AERB Annual Report 2020

factor between each pin with every other pins and

1200
1.41001E8 PT of 220 MWe and 540/700 MWe IPHWR fuel
1100 1.42001E8 bundle were estimated with good accuracy to
1.43001E8
1000 1.44001E8 avoid over/under estimation of radiation heat
1.45001E8 transfer. Further for use in safety analysis code,
Temperature (K) 800 1.47001E8 fuel-pin-ring wise view factors of each pin were
1.46001E8
900
also estimated.
700
600
500
400
0 2000 4000 6000 8000 10000 12000 14000
Time (s)
Fig. 7.1(c): Affected pass clad Temperature

7.1.2 Development of Monte Carlo Model for
View Factor Calculation of the IPHWR
Fuel Bundles

Fuel failure criteria and phenomenon like
hydrogen generation and release of ssion
products are strong functions of the fuel Fig. 7.2: Effect of number of rays on Computed
temperature during the severe accident
View Factor between two Parallel Pins
progression. In order to obtain realistic estimates
of the fuel temperatures for safety assessment, the
radiation heat transfer need to be modelled
accurately with sufcient details. Radiation heat 7.1.3. ISOMED Source Storage Cooling
Analysis: Effect of the Air Gap
emitted by a body is proportional to fourth power
of the temperature, emissivity, surface area, etc.
ISOMED (Irradiation Sterilization of
However, when two bodies are involved,
radiation heat transfer between any two bodies is Medical Products), the rst irradiation plant for
sterilization of medical products, was set up in
also directly proportional to the view factor. The
India by the Department of Atomic Energy (DAE)
fraction of heat emitted by one body that is
at Trombay with the assistance of the United
intercepted by other body needs to be calculated
Nations Development Programme (UNDP). In
precisely. Among the various methods available 60
for computation of view factor, Monte-Carlo this facility, Co is used as the source of radiation
and the plant had been in operation for more than
method has been adopted to estimate view factors
for Indian PHWR (IPHWR) fuel bundles because four decades (since 1974). The radiation source is
housed in a concrete cell and this concrete is
of its accuracy and exibility. The method
cooled by water circulation through cooling coils
involves estimation of fraction of rays emitted by
embedded in the concrete shild. Towards
pin that are intercepted by the other pins and the
estimating the cooling capability of the
Pressure Tube (PT). As number of ray's increase,
this factor approaches view factor (see Fig.7.2). embedded coil, a 3-D model of the concrete shield
along with the steel liner was developed using
multi-physics software COMSOL and the cooling
The developed code was validated against
of the concrete through this coil was also
analytical solution of view factor for innitely
assessed.While reviewing the cooling
long parallel cylinder and effect of number of rays
on view factor was also studied. With 1E+06 rays; analysis results, it was suggested that the
view factor could be estimated with reasonable effect of air gap between the coil & concrete,
accuracy i.e. error ≤ 0.1629 %. and steel liner and concrete also needs to be
studied. Further, the 3D model was modied
The code was further validated with cases to include the air gap at various locations. It
available in the open literature. An array of tubes was observed that even if there is air gap in
arranged in square matrix was selected from the the last leg of the cooling coil (Fig. 7.3 (a) and
literature for the validation. The results obtained (b)), the peak concrete temperature
from this code are in close agreement with the
results given in the literature. Radiation view estimated was within the acceptable limits.

74
AERB Annual Report 2020