Program evaluates propellant heating in a nuclear rocket stage. Program code employs infinite-medium buildup factors to calculate gamma dosage and employs the Albert-Welton kernal to calculate the fast neutron dosage

Lahti, G. P.

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December 1970	 Brief 70-10648 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
A Computer Program for Evaluating Propellant Heating and Radiation

Dosage to Crews of Nuclear-Powered Rocket Vehicles 
In nuclear vehicles, special problems that require 
evaluation are the propellant heating and the radiation 
dosage emitted to the crew during the operation of 
the reactor. Excessive heating of the propellant may 
produce pumping problems so that shielding, addi-
tional pressurization, or venting of the propellant may 
be required. In a manned stage, the radiation dosage to 
the crew can control the shielding requirements. In 
many configurations, the propellant can serve as a 
shield between the crew and the engine. During engine 
operation, however, the consumption of propellant 
results in a continuous reduction of this shielding. 
A FORTRAN IV computer program, QADHD, 
was written to evaluate the propellant heating in a 
nuclear rocket stage and to calculate the gamma and 
fast neutron dosages received by a crew from the radia-
tion emitted by the nuclear engine during the operating 
period. The code uses the Los Alamos Scientific Lab-
oratory (LASL) point-kernel line-of-sight code QAD4 
as a basis for its calculations. The QADHD is a com-
bination of three codes: QAD4, QADH, and QADD. 
The LASL QAD4 is a general purpose program writ-
ten to calculate gamma and fast neutron dosages due 
to a volume-distributed source in a complex source-
shield geometry that is generally describable by quad-
ratic surfaces. QAD4 employs infinite-medium 
buildup factors to calculate the gamma dosage and 
employs the Albert-Welton kernel to calculate the 
fast neutron dosage. The QAD4 included here was 
revised slightly from the LASL version to facilitate its 
use in the QADHD, as well as to simplify data input. 
QADH utilizes the QAD4 routines to evaluate local 
heating throughout the propellant (and tank wall)
and then integrates these heating rates over the entire 
volume of the propellant. Assuming that this heat 
is distributed uniformly throughout the propellant 
by natural convection, the complete-mix model en-
ables the rate of temperature rise of the propellant to 
be determined. QADH then determines the total 
temperature rise and accumulative heat input to the 
propellant as a function of reactor operating time. 
In some nuclear rocket configurations, the propellant 
may serve to shield the crew from radiation emitted 
by the engine. In these cases, QADD utilizes the 
QAD4 routines to calculate biological dosage rates 
to the crew during engine operation, while the propel-
lant depth in the tank (or amount of shielding the 
propellant provides) changes with time. QADD 10 
integrates these dosage rates over engine operating 
time to obtain a total dosage time history. 
Notes: 
1. This program is written in FORTRAN IV for use 
on the IBM 7094 11/7044 Direct Coupling System. 
2. Inquiries may be directed to: 
COSMIC 
Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B70-10648
Source: G. P. Lahti

Lewis Research Center

(LEW-10951) 
Category 01 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
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A computer program for evaluating propellant heating and radiation dosage to crews of nuclear-powered rocket vehicles

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