​Initial Conditions for HAC Thermal Evaluations
(effective date 11/​30/2015 )


When the Nuclear Regulatory Commission (NRC) adopted the International Atomic Energy Agency (IAEA) Safety Series 6 (-85 Edition), the final rule in the Federal Register stated that the NRC held the view that insolation may be neglected before and during the Hypothetical Accident Condition (HAC) Thermal Test (Ref 10 CFR 71.73(b) for Test Conditions and 71.73(c)(4) for Thermal test):

"... NRC adopts the view of the thermal experts who participated in developing the IAEA regulations. Those experts thought the effects of solar radiation may be neglected before and during the thermal test but that such effects should be considered in the subsequent evaluation of the package response." (Ref Federal Register / Vol. 60, No. 188 / Thursday, September 28, 1995 / Rules and Regulations 50257)

When IAEA superceded Safety Series 6 with TS-R-1 (-96 regs), the IAEA thermal experts changed their position and required insolation in Para 728 of TS-R-1 as an initial condition for the HAC Thermal Test.  When these regulations were adopted by NRC. there was no discussion of this change in the final rule in the Federal Register.  In addition, the initial conditions for the Thermal Evaluation under Hypothetical Accident Conditions in NRC's Standard Review Plan for Transportation Package for Radioactive Material (NUREG_1609), still requires verification that the application justifies the most unfavorable initial conditions of an ambient temperature between -20°F and 100°F with no insolation (Ref NUREG-1609, page 3-10).

The Department of Energy (DOE) Packaging Certification Program sought clarification and asked colleagues at NRC, "When did NRC change their position on requiring insolation as the initial condition for HAC thermal?  Is it documented?"

NRC responded that their Standard Format and Content of Part 71 Applications for Approval of Packages for Radioactive Materials (RegGuide_7-9) states in Section 3.4.1 for the initial conditions of the thermal evaluation under hypothetical accident conditions, “This section should identify initial conditions, and justify that they are most unfavorable, including initial ambient temperature, insolation, internal pressure, decay heat, etc.”   Also, 10 CFR 71.73(b) states that the “…initial internal pressure within the containment system must be the maximum normal operating pressure…”  Neglecting insolation prior to the fire would result in an initial temperature in the containment system that is inconsistent with that corresponding to the maximum normal operating pressure. Therefore, based on the above it is necessary to include insolation during the initial conditions of the thermal evaluation under hypothetical accident conditions.​  

Based on this clarification from NRC, PCP will require applicants for DOE CoCs to include insolation as an initial condition for their thermal evaluation under ​HAC.

For questions or comments contact DOE PCP Manager, Dr. Shuler, (301) 903-5513, james.shuler@em.doe.gov




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