Practical MCNP for the Health Physicist, Medical Physicist, and Radiological Engineer

Additional Topic Information

Input File Preparation
All of the basic elements required to assemble an input file will be discussed:

• Surface-sense geometry description
• Source definition in terms of energy, spatial extension, and direction
• Transport options Tally types
• Material cards
• Peripheral cards

Interpretation of Output File
A total of 12 demo problems will be run in class. In each case, the output tables and tally results will be discussed in detail. These include the Problem Summary Table, Photon and Neutron Activity per cell, statistical checks, and the tally fluctuation charts.

Exposure and Dose Rate Calculations
Typically in radiation protection and shielding analysis, the desired end result is dose or exposure rate. It is possible to configure the tallys in MCNP so that these quantities are calculated by the code directly. Discussion will cover the various methods available to directly determine photon and neutron dose.

Radiation Shielding
Several demos will be presented, graded in difficulty, to illustrate the application of MCNP to solve essential radiation shielding problems. The three demos will deal with transmission of photons and neutrons through a thick concrete shield and the scatter of photons through a maze entrance. The various variance reduction techniques necessary to solve such problems efficiently will be discussed.

Skyshine Calculations
Monte Carlo transport methods are ideally suited for solving skyshine problems, especially when geometric complexity is present. A demo will be devoted to photon skyshine. The appropriate strategy for solving this class of radiation transport problem will be described in detail. Discussion will cover the Kansas State University Skyshine Experiment Benchmark calculations.

Detector Simulation
An exciting feature of MCNP is the Pulse Height Tally (type F8) which simulates the detector response function of a gamma spectrometer. A demo is devoted to the application of a type F8 tally to generate the photon spectrum of a real-world NaI detector. This tally can also be used to calculate dose deposition (in MeV) in a cell of interest from first principles by following the coupled electron-photon transport through a particular geometry.

Beta Bremsstrahlung Production
A demo problem devoted to the calculation of beta bremsstrahlung production will be discussed. The problem models a mixed beta spectrum incident on a ceramic substrate. Variance reduction methods are illustrated to obtain X-ray emission rates.