Generalized Computer Model Calibration for Radiation Transport Simulation

Abstract

Model calibration uses outputs from a simulator and field data to build a predictive model for the physical system and to estimate unknown inputs. The conventional approach to model calibration assumes that the observations are continuous outcomes. In many applications this is not the case. The methodology proposed was motivated by an application in modeling photon counts at the Center for Exascale Radiation Transport. There, high performance computing is used for simulating the flow of neutrons through various materials. In this article, new Bayesian methodology for computer model calibration to handle the count structure of our observed data allows closer fidelity to the experimental system and provides flexibility for identifying different forms of model discrepancy between the simulator and experiment. Supplementary materials for this article are available online.

keyword:

• Bayesian methods; Computer experiments; Count data; Radiation transport

Acknowledgments

The authors would like to thank Les Braby at Texas A&M University for his assistance on the CERT experiments.

Supplementary Materials

Supplemental sampling details: PDF document containing additional details about the sampling approach discussed in Section 3.1.

Further discussion on the choice of prior distributions: PDF document containing further discussion on the choice of prior distributions in Sections 3.1 and 5.2.

R-package for CERT calibration analyses in this manuscript: R-package certcalibration containing code to perform the analyses described in the article. The package also contains all datasets used as examples in the article. (GNU zipped tar file)

Additional information

Funding

This material is based upon work supported by the Department of Energy, National Nuclear Security Administration, under award number DE-NA0002376. Established by Congress in 2000, NNSA is a semiautonomous agency within the U.S. Department of Energy responsible for enhancing national security through the military application of nuclear science. NNSA maintains and enhances the safety, security, reliability, and performance of the U.S. nuclear weapons stockpile without nuclear testing; works to reduce global danger from weapons of mass destruction; provides the U.S. Navy with safe and effective nuclear propulsion; and responds to nuclear and radiological emergencies in the United States and abroad. This research was partially supported by a Discovery grant from the Natural Sciences and Engineering Research Council of Canada. This article is released under LA-UR-19-30814.