Document: NUREG-0800
Document ID: 9738c583-ac33-4836-b8f1-580dc98eb7f0
Document Type: srp
Title: RADIOLOGICAL CONSEQUENCES OF THE FAILURE OF SMALL LINES CARRYING
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350147.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.6.2
CFR Part: 
CFR Title: 

Content:
ation valve outside containment), the failure is postulated to occur downstream of the valve in conjunction with a single failure (i.e., valve does not close). Unless other isolation or flow reduction capabilities are provided (e.g., orifice in line) which will be evaluated on a case-by-case basis, it is assumed that this line failure cannot be isolated and the primary coolant release will continue until the primary system is depressurized. c. The amount of primary coolant released is conservatively estimated by assuming critical flow at the small line break location with the reactor coolant fluid enthalpy corresponding to normal reactor operating conditions. The reviewer evaluates the reactor coolant release rates provided by the applicant, taking into consideration similar information for plants recently reviewed. The reviewer should verify the release rates and the total amount of coolant released with the RSB in a coordinating review effort. d. The initial fission product concentrations in the primary coolant are assumed to be the maximum equilibrium values permitted by the standard technical specification for the NSSS vendor or those pro- vided by the applicant. In addition, it is assumed that an iodine spike occurs as a result of the reactor shutdown or depressurization of the primary system. The spike is modelled by increasing the equilibrium fission product activity release rate from the fuel by a factor of 500. The reviewer consults with the RSB regarding the potential for and extent of damage to the fuel as a result of the line failure. If appropriate, the additional fission product activity in the primary coolant activity will be included in the analysis. 15.6.2-3 Rev. 2 - July 1981 The fraction of the iodine assumed to become airborne and available for release to the atmosphere, without credit for plateout, is equal to the fraction of the coolant flashing into steam in the depressuri- zation process. The flash fraction is determined by assuming the