Venting Above the Liquid Level or Overall Contain ment Failure

DOE-HDBK-3010-94

3.0 Liquids; Aqueous Solutions

Other recent investigations (Leach, 1993; Gieseke, Kogan and Shaw, September 1993) using

an analytical model suggest that, under some conditions, the fraction of drops in the finer

size fractions (i.e., 10-m and less) are greater for fine orifices (and possibly slot-type

breaches) at high pressures and that the evaporation of the liquid prior to deposition may

reduce the size of the larger diameter drops to some extent. There is considerable

uncertainty as to the value to assign the critical factor (Q, a drop size fitting parameter) and

the analytical model, though useful in understanding the phenomenon, cannot presently be

used to predict the size distribution of sprays.

3.2.2.3.2 V en tin g A b ove th e L iq u id L evel or O verall C on tain m en t F ailu re. The

amount of liquid entrained as droplets in depressurization flow depends on several factors.

The effect of dissolved gases, surface turbulence and stratified two-phase flow are considered

below.

A . E levated L evels of D issolved G ases. Sudden depressurization of a liquid allows

the release of dissolved/trapped gases. This sudden release of gases may result in

bubble formation that can create very small drops upon collapse. The drops formed

can be carried with the venting gases. Figure 3-3 previously presented illustrated the

relationship between the amount of gas/vapor released and the fraction airborne.

Experiments were performed to measure the ARF due to venting pressurized volumes

of aqueous solutions in quasi-equilibrium with their pressurizing gases (Sutter, August

1983). Data from the referenced document (reproduced as Tables A.4 through A.7 in

Appendix A) describing airborne release of aqueous solutions are tabulated in Table

3-3. The experimental apparatus is shown in Figures A.4 & A.5 of Appendix A.

The average ARF as a function of pressure, solution density and source size are

shown in Table 3-4 (tabulated as weight percent, 0.05 wt/o = 5E-4 fraction) from the

reference and plotted in Figure 3-5. ARF increases with pressure and decreases with

density and source size. Due to the pressures employed, there appears to be a

significant difference between bounding ARF and RF for pressure less than

0.345 MPag (50 psig) and between 0.352 MPag (51 psig) and 3.45 MPag (500 psig).

Bounding values for each pressure range are given. For the venting of liquids with

elevated levels of dissolved gases or overall vessel failure/blowout to 0.345 MPag, the

ARF and RF values range from 3E-6/0.8 to 5E-5/0.8. The bounding ARF and RF are

assessed to be 5E-5 and 0.8.

For the venting of liquids with elevated levels of dissolved gases or overall vessel

failure/blowout in a range of 0.352 MPag to 3.45 MPag, the data appears to show

some dependency on experimental parameters. For the uranine solution (lower

density liquid, ~1 g/cm3), a bounding ARF of 2E-3 with a fraction of airborne

Page 3-22