Speaker
Description
In the designing a high-power tungsten target, such as the one being designed
at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source
(SNS) Second Target Station (STS), a thorough understanding of decay heat
driven temperature rise is crucial for ensuring safety during maintenance peri-
ods and loss-of-coolant accidents (LOCA). Tungsten, when exposed to steam
at temperatures above 800°C, hydrates and becomes volatile, posing significant
safety concerns. Therefore, it is imperative to accurately predict decay power
and the resultant temperature rise in the target under various operational sce-
narios. This study undertakes a comparative analysis of decay heat calculations
in a water-cooled solid tungsten target using two popular particle transport
simulation codes: FLUKA and MCNP6 paired with CINDER2008.
The target-moderator-reflector (TMR) system modeled in this research in-
cludes a water-cooled solid tungsten target, water premoderators, liquid hy-
drogen cold moderators, beryllium reflectors, and water-cooled stainless-steel
shielding. The tungsten volume is clad with a thin layer of erosion/corrosion
resistant material, such as tantalum, to mitigate the effects of coolant exposure.
This comprehensive modeling approach allows for an in-depth examination of
the decay heat generation and its transport within the target system.
The study reveals significant differences in the calculated decay heats be-
tween FLUKA and MCNP/CINDER2008, attributed primarily to variations
in radiative capture cross-sections used by these codes, and the treatment of
the emitted residual radiation. The effects of different neutron data libraries
on decay physics calculations and subsequent decay heat predictions are also
explored, along with the effects of transporting decay betas and gammas.
The findings of this study provide valuable insights into the uncertainty
range associated with decay heat predictions for high-power spallation targets,
critical for hazard analysis and safety assessments. By elucidating the differences
in decay heat calculations between FLUKA and MCNP/CINDER2008, this
research contributes to the development of more accurate and reliable predictive
models for spallation target design and operation. Ultimately, this work aims to
enhance our understanding of decay heat phenomena, facilitating the safe and
efficient operation of high-power particle accelerators and spallation neutron
sources.