Computer program contains an input library of nuclear data for 44 elements and their isotopes to determine the induced radioactivity for gamma emitters. Minimum input requires the irradiation history of the element, a four-energy-group neutron flux, specification of an alloy composition by elements, and selection of the output

Heiser, P. C.

Ricks, L. O.

English

NASA Technical Reports Server

December 1967	 Brief 67-10665 
AEC-NASA TECH BRIEF 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Computer Program Calculates Gamma Ray Source Strengths
of Materials Exposed to Neutron Fluxes 
^j
The problem: 
Activation predictions are a significant part of 
radiation analysis. For example, activation of reactor 
components can determine their reuse in subsequent 
reactor tests. Also, activation of reactor test area and 
reactor components determines personnel access time 
at the reactor test sites after shutdown and removal of 
the reactor system. An activation analysis code is 
needed that includes a comprehensive element library 
not previously included in codes of this type. 
The solution: 
A computer program which contains an input 
library of nuclear data for 44 elements and their 
isotopes to determine the induced radioactivity for 
gamma emitters. Minimum input requires the irradia-
tion history of the element, a four-energy-group 
neutron flux, specification of an alloy composition by 
elements, and appropriate selection of the output. 
How it's done: 
The activation code calculates gamma ray source 
strengths (in four energy groups) of materials exposed 
to neutron fluxes as a function of exposure and decay 
time. Options are provided in the code to calculate 
activity, including cyclic reactor operation of equal 
time duration and burnup of target material to ac-
count for flux depressions and resonance self-shielding. 
The program contains a library of nuclear properties 
(activation cross sections, isotopic fractions, decay 
constants, and gamma ray energy yields) for 44 
elements, 200 isotopes, and 129 reactions, including
radioactive captures and transmutations due to fast 
and thermal neutrons. 
The input consists of control cards for calculation 
and print options, material composition, neutron flux, 
exposure time, and time at which the gamma activity 
is to be printed. The output may present activity by 
alloy, target element, or isotope for parent and 
daughter at each requested time. Running time is less 
than one minute for a typical alloy. The accuracy of 
the calculations is governed primarily by the accuracy 
of the material composition specification, and the 
neutron flux cross-section weighting. 
Notes: 
I. This program is written in modified Fortran II for 
use on the IBM 7090/94 computer. 
2. Inquiries concerning this program may be made to: 
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B67-10665 
Patent status: 
No patent action is contemplated by AEC or 
NASA.
Source: L. 0. Ricks and P. C. Heiser 
of Westinghouse Astronuclear Laboratory

under contract to
AEC-NASA Space Nuclear Propulsion Office 
(NUC- 10143) 
Category 06 
This document was prepared under the sponsorship of the Atomic	 liability resulting from the use of the information contained in this 
Energy Commission and/or the National Aeronautics and Space document, or warrants that the use of any information, apparatus, 
Administration. Neither the United States Government nor any per- 	 method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights.
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Computer program calculates gamma ray source strengths of materials exposed to neutron fluxes

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