Document: NUREG-0800
Document ID: 90078267-41fd-4e45-bc4c-a21ef5ed6dfb
Document Type: srp
Title: Revision 3 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070740442.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6
CFR Part: 
CFR Title: 

Content:
hermo-physical properties are shown in Table 2. Applicants should provide a detailed list of passive heat sinks with appropriate dimensions and properties. B. Heat Transfer Coefficients. The following conservative condensing heat transfer coefficients for heat transfer to the exposed passive heat sinks during the blowdown and post-blowdown phases of the loss-of-coolant accident should be used: (i) During the blowdown phase, assume a linear increase in the condensing transfer coefficient from hinitial = 8 Btu/hr-ft2-EF, at t = 0, to a peak value four times greater than the maximum calculated condensing heat transfer coefficient at the end of blowdown, using the Tagami correlation, hmax=7.25(Q/Vtp)0.62 where hmax = maximum heat transfer coefficient, Btu/hr-ft2-EF Q = primary coolant energy, Btu V = net free containment volume, ft3 tP = time interval to end of blowdown, sec. (ii) During the long-term post-blowdown phase of the accident characterized by low turbulence in the containment atmosphere, assume condensing heat transfer coefficients 1.2 times greater than those predicted by the Uchida data and given in Table 3. BTP 6-2-4 Revision 3 - March 2007 (iii) During the transition phase of the accident between the end of blowdown and the long-term post-blowdown phase, a reasonably conservative exponential transition in the condensing heat transfer coefficient should be assumed (See Figure 2). The calculated condensing heat transfer coefficients based on this method should be applied to all exposed passive heat sinks, both metal and concrete, and for both painted and unpainted surfaces. Heat transfer between adjoining materials in passive heat sinks should be based on the assumption of no resistance to heat flow at the material interfaces. An example is the containment liner to concrete interface. (iv) Variations from these guidelines may be acceptable if the overall ECCS performance evaluation model produces an acceptable peak calculated fuel cladding temperature. C.