**1. NAME AND TITLE**

TACT-III: Calculation of the Transport of Radioactivity from a Reactor Core.

**AUXILIARY ROUTINE**

Nuclide data pre-processor to convert from BCD to binary format.

**2. CONTRIBUTORS**

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

U. S. Nuclear Regulatory Commission, Washington, D. C.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; IBM 370/3033.

**4. NATURE OF PROBLEM SOLVED**

TACT-III (an acronym for ``Transport of ACTivity") is one of a series of codes developed for the purpose of evaluating the mitigating effects of engineered safety features. It has been applied to analyses of light water reactors with a data base consisting of iodines and noble gases.

TACT-III is a computational vehicle for representing a mathematical model by a system of ordinary
differential equations and calculating a numerical solution of the differential equations. It is not a
model, itself, nor is it tied to a fixed set of source terms or other parameter values.

**5. METHOD OF SOLUTION**

TACT-III simulates the movement of radioactivity released from a reactor core as it migrates
through user-defined regions (nodes) of the containment, is immobilized by filters and sprays, and leaks
to the outside environment. The user's input data specify a dynamic compartment model which is
represented by systems of ordinary differential equations with constant coefficients. The equations are
solved explicitly by matrix transformation methods. TACT-III carries out the integration of these
systems of equations over a succession of contiguous time intervals following reactor shutdown, with
the interval boundaries corresponding to transitions of system parameter values. Outputs are shown
for the end of each time interval and include the level of radioactivity in each node of the containment
and in the environment, broken down as iodines, noble gases, and solids, and the radiation dose to
reference individuals at the exclusion radius, the boundary of the low population zone, and in the
control room. Values of input parameters are also printed and a summary is available at the user's
option.

**6. RESTRICTIONS OR LIMITATIONS**

Data are required from two sources: (1) input data from the user which varies from one run to
another according to the analysis to be made and (2) a permanent data base which normally does not
change from one run to another but which can be regenerated to include new data. System parameter
values must be constant within each time interval.

**7. TYPICAL RUNNING TIME**

The sample problems tested required < 10 seconds each.

**8. COMPUTER HARDWARE REQUIREMENTS**

TACT-III is operable on the IBM 370/3033 computers. A typical case requires 840 K bytes of
core storage.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran Q (H extended enhanced) compiler is required. TACT-III uses the IBM OS/MVS JES2
system.

**10. REFERENCE**

G. G. Killough, C. L. Begovich, A. L. Sjoreen, L. W. Bell, "A Guide for the TACT III Computer
Code," NUREG/CR-3287, ORNL/TM-8763 (May 1983).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code and sample problem input and output.

**12. DATE OF ABSTRACT**

January 1984.

**KEYWORDS: ** NUCLIDE TRANSPORT; FISSION PRODUCTS; RADIOACTIVITY RELEASE; REACTOR ACCIDENT