Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
ACCESSION #: 9601300209
NUMERICAL APPLICATIONS, INC.
Engineering Software
Development and Applications
825 GOETHALS DRIVE, SUITE A o RICHLAND, WA 99352 o
TELEPHONE (509) 943-0861 TELECOPY (509) 943-6617
January 16, 1996
Director, Office of Inspection and Enforcement
U.S. Nuclear Regulatory Commission
Washington, D.C. 20555
Dear Sir:
This letter is to inform you of a reportable defect under 10CFR Part 21.
The defect is in the early versions of the GOTHIC and FATHOMS computer
programs for containment and general thermal-hydraulic analysis and is
described in the attached error notification being sent to all users of
record with the affected versions.
The notification applies to all organizations with current or future use
of GOTHIC 3.1 or earlier and all versions of FATHOMS.
The defect was confirmed on January 15, 1996 and all affected users are
being notified.
Version 3.2 of GOTHIC (July 1990) eliminated the identified problem.
Earlier code versions with the identified problem are not frequently
used. Modifications are available from NAI to correct the problem.
If there are any questions, please contact me at the number shown above.
Sincerely,
Thomas L. George
January 15, 1996
GOTHIC ERROR NOTIFICATION - GOTHIC.3.1.34
To: GOTHIC Users
An error has been discovered in GOTHIC_S 3.1 and earlier versions, and
all versions of the precursor code FATHOMS, that may effect the accuracy
of some calculations. The error does not exist in version 3.2 or later
of GOTHIC.
The error may result in an overprediction of the vaporization of water in
superheated environments. GOTHIC 3.1 and earlier versions, including
FATHOMS, use a single energy equation for the combined liquid and drop
phases and correspondingly a single source term for the total
vaporization rate of drops and liquid. In certain analyses, e.g., a
steam line break, there should be a minimal amount of drops in the
atmosphere. However, the code selected initial value for the drop
surface area and a small drop area source term associated with the break
in these early code versions, results in a substantial drop surface area
during the blow-down, even though the drop mass is negligable. Because
the drop and liquid vaporization are combined, the large drop area
combined with the significant liquid from condensation on heat sinks,
results in a high estimate for the vaporization rate. This vaporization
cools the atmosphere and results in lower peak containment temperatures
and pressures. This effect does not cause a problem in steam/water
blowdowns because the significant drop injection quickly leads to
realistic values for the drop surface area and the total rate of phase
change.
Any safety analyses performed with these early code versions should be
reviewed with regard to the identified error.
Necessary corrections may be obtained from NAI.
NAI considers this error to be a reportable defect under 10CFR Part 21
and an error notification has been sent to the NRC.
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