“SSI-Toolbox” Integrated
Model Development

Program Brief

Statement of Problem: To exercise its authority to set radiation protection standards in Sweden and to evaluate whether such standards are implemented properly, the Swedish Radiation Protection Institute (SSI), located in Stockholm, needed a computer-based set of tools to evaluate alternatives, test basic concepts, and train its staff. The computer code known as “SSI Tool Box,” which simulates a geologic repository system in an integrated manner, was developed by CNWRA^® to meet this need.

Approach and Accomplishments: CNWRA assembled a team of subject matter specialists and programmers to accomplish the task. As a first step, a software requirements document (SRD) was prepared describing the specific needs the tool box must satisfy. The SRD identified the system components and related processes that must be simulated, specified the user interface, described post processing needs, and identified the hardware on which the code must operate. After the client approved the SRD, a basic design for the software was developed. To minimize costs, existing codes (e.g., CAP88 and ISOSHLD for shielding calculations) or existing codes with modifications (e.g., TRAM for calculation of transportation risks) were identified and used as modules of the Tool Box wherever possible. New codes (e.g., FRAC_SSI for flow and transport in a fractured medium and SOSIM for diffusive release from the engineered barrier subsystem) were developed where needed. A new code also was developed to ensure proper interface and exchange of data between these different modules to create an overall flexible and integrated model. A Monte Carlo algorithm was incorporated into the code so uncertainties in model parameters could be addressed quantitatively.

The user interface was designed to be friendly so nontechnical people could use the code also. Input could be entered interactively through well-designed computer screens. A post-processor was built to provide output in both tabular and graphical form. The code was delivered to the client with a user’s manual, and training was provided to SSI staff.

Client Benefits: The Tool Box is being extensively used by the SSI for repository simulations in Sweden. In addition, the SSI is using the Tool Box in Russia and other Eastern European countries as a training tool.