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the system. Discrepancies in the annular thickness are potentially safety significant and must be
corrected whereas discrepancies in the height are immaterial and no further action is required.
Therefore, if a given system parameter can be extended to infinity or an infinite system and
criticality is not achieved, discrepancies in the model or report related to this parameter are not
safety significant.
One area where an overly detailed model can impact the analysis and operation adversely is in
the area of "infraction traps." If the description section is extremely detailed then there is a good
chance the associated limits and controls will be similarly prescriptive. Such unnecessary
"requirements" can overwhelm operations with trivial demands, damage the credibility of the
criticality safety program, and mask more serious noncompliance issues. The reviewer should be
aware of the potential to "over describe" the system and define controls which have no bearing
on the criticality safety of the operation. Consider the annular tank example again. Assume the
description section specifies the annular dimension as 1.500 +/- 0.125 inches. Then the
associated limit follows suit. Note that if the actual annular dimension is found to be either 1.3
inches or 1.7 inches, a criticality safety infraction ensues. For an isolated annular tank, the tank
will remain subcritical with an annular thickness up to just over 3 inches (assuming uranyl nitrate
solution concentrations not exceeding 400 g/l). There is no need to specify a minimum annular
tank thickness unless it is an Engineering Safety Requirement in Section 7. Hence, operations
will be unduly impacted by a criticality infraction that has no bearing on safety (i.e., "infraction
trap"). The reviewer should ensure that the descriptions of the system and associated models are
detailed enough to ensure that potential criticality scenarios are analyzed appropriately without
unnecessary specification. For example, if the tank deformation must be bounded, design
pressure and available pressure sources for the tank system must be discussed.
Key Review Issues
If not familiar with the fissile system/operation, conduct a walkdown of the facility.
Identify those items and parameters with safety significance.
Ensure there is enough detail to understand what was analyzed.
Compare the system description to calculational models (internal consistency) and to the "as
found" facility (external consistency).
Identify safety significant discrepancies.
Look for unnecessary specification of the system and "infraction traps."
Look for equipment used in the operation that has criticality safety significance.
3.0 Requirements
Any special requirements that impact the methodology of the analysis or drive special
documentation are specified in this section. References to predecessor criticality safety
evaluations relied upon to provide detailed documentation of the safety basis may be included.
There is no need to state requirements of "routine" orders (e.g., 5480.24) and standards (e.g.,
ANSI/ANS) either explicitly or by reference.

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