Document: NUREG-0800
Document ID: 5cb19e99-a561-4571-92e5-2933a6181985
Document Type: srp
Title: CONTAINMENT SPRAY AS A FISSION'PRODUCT CLEANUP SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340761.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.5.2
CFR Part: 
CFR Title: 

Content:
the concentration of iodine in the spray solution. Experiments with fresh sprays having no dissolved iodine were observed to be quite effective in the scrubbing of elemental iodine even at a pH as low as 5 (Refs. 9 and 11). However, solutions having dissolved iodine, such as the sump solutions that recirculate after an accident, may revolatilize iodine if the solutions are acidic (Refs. 5 and 10). Chemical additives in the spray solution have no significant effect upon aerosol particle removal because this removal process is largely mechanical in nature. (1) Elemental iodine removal during spraying of fresh solution During injection, the removal of elemental iodine by wall deposition may be estimated by Aw = Kw A/V Here, A is the first-order removal coefficient by wall deposi- tion, Awis the wetted surface area, V is the containment build- ing net free volume, and Kw is a mass-transfer coefficient. All available experimental data are conservatively enveloped if K is taken to be 4.9 meters per hour (Ref. 13, 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 may 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, As, may be taken to be 6K TF where k is the gas-phase mass-transfer coefficient, and T is the timP of fall of the drops, which may be estimated by the ratio of the average fall height to the terminal velocity of the mass-mean drop (Ref. 14). The above expression represents a first-order approximation if a well-mixed droplet model is used for the spray efficiency. The expression is valid for As 6.5.2-10 Rev. 2 - December 1988 values equal to or