Document: NUREG-0800
Document ID: 848ab24d-ac9b-4ec5-85ff-099e13b769c3
Document Type: srp
Title: CONTAINMENT SPRAY AS A FISSION PRODUCT CLEANUP SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0601/ML060150001.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.5.2
CFR Part: 
CFR Title: 

Content:
nical. (1) Elemental iodine removal during spraying of fresh solution During injection, the removal of elemental iodine by wall deposition can be estimated by the equation Where, 8w is the first-order removal coefficient by wall deposition, A is the wetted- surface area, V is the containment building net free volume, and Kw is a mass- transfer coefficient. All available experimental data are conservatively bounded if Kw is taken to be 4.9 meters per hour (Reference 7, page 17). During injection, the effectiveness of the spray against elemental iodine vapor is chiefly determined by the rate at which fresh-solution surface area is introduced into the containment building atmosphere. The rate of solution surface created per unit gas volume in the containment atmosphere can be estimated as 6F/VD, where F is the volume flow rate of the spray pump, V is the containment building net free volume, and D is the mass-mean diameter of the spray drops. The first-order removal coefficient by spray, 8s, may be taken to be where Kg is the gas-phase mass-transfer coefficient and T is the time of fall of the drops, which may be estimated by the ratio of the average fall height to the Rev. 3 - December 2005 6.5.2-12 terminal velocity of the mass-mean drop (Reference 20). This equation represents a first-order approximation if a well-mixed droplet model is used for the spray efficiency. The equation is valid for 8s values equal to or greater than 10 per hour. 8s must be limited to 20 per hour to prevent extrapolation beyond the existing data for boric acid solutions with a pH of 5 (References 16 and 15). For 8s values less than 10 per hour, analyses using a more sophisticated expression are recommended. (2) Elemental iodine removal during recirculation of sump solution The sump solution at the end of injection is assumed to contain fission products washed from the reactor core and removed from the containment atmosphere. If the solution is acidic, the radiation absorbed by the sump