Solidification on Polymers

DOE-HDBK-1129-99

8.1.4.b(2) Solidification on Polymers

PPPL has been performing studies of solidification in various polymers. PPPL ships tritium to

Hanford for burial. Three polymers are approved for absorption of radioactive liquids for land burial

at the Hanford site. In order for these polymers to absorb the liquids, and, therefore, exhibit the

properties of a solid, they must be used in accordance with EPA test method 9096, "Liquid

Release Test," so that they pass a pressure test of 20 psi (Hanford burial requirement). These

polymers can provide significant advantages over "clay-based" absorbents in that they do not

require mixing, and that they exhibit less than 1% expansion by volume.

PPPL's ER/WM Division has performed independent evaluations and testing of these polymers to

verify the ratios and absorption capability. The testing has been performed by Kiber Environmental

Services, Inc. of Norcross, Georgia. To date, one of the polymers has passed the 20 psi test using

a modified test plan to account for the small particle size. Stergo has passed the 20 psi test at a

ratio of 20:1 water:polymer. Also, two of the polymers have passed the test at a pressure of 50 psi

(the normal test pressure), using ratios of 10:1. The two polymers are Stergo (Corpex

Technologies) and SP-400 (Waterworks).

Users may want to perform their own additional independent testing to determine the correct

ratio(s) for their product (if different from the aforementioned) and/or for their specific liquid

characteristics. The PPPL testing was performed on tap water with a neutral pH.

8.1.4.b(3) Evaporation to the Environment

It is possible but expensive to solidify several thousand gallons of water containing only tens of

curies of tritium. When properly permitted by State and Federal regulations, tritiated wastewater

can be evaporated to the environment. An example of an evaporator, which was permitted by

EPA, is the evaporator used at the now closed TRL facility at SNL. This tritium-contaminated

wastewater evaporator was permitted to evaporate up to 100 Ci/yr to the environment. Over

several years this system evaporated tens of thousands of gallons of extremely low-level tritium-

contaminated water.

Evaporation may not be a reasonable or feasible method of wastewater disposal at every site;

however, it was the preferred disposal option at Three Mile Island. Over 2.2 million gallons of

tritiated water were collected for storage and treatment at the TMI site after the 1979 accident. This

waste water, with tritium concentrations ranging from 1.6E-1 Ci/mL to 2.4E-2 Ci/mL, resulted

from many sources including the primary coolant, spent fuel pool, submerged demineralized

system, and the EPICOR I and II ion-exchange processing systems. Lesser sources included

wastewater from the decontamination of systems and components including steam generators and

flushing of auxiliary systems. The principal constituents of this processed water were boric acid

and tritium. The water was accumulated in large Process Water Storage Tanks (~ 600K gallons)

and processed through a vacuum evaporator system. The majority of the tritiated water was

released to the environment. The boric acid and residual radioactive contamination was

concentrated into a powder form and disposed of at a LLW disposal facility in Barnwell, SC. In the

past, these low-level concentrations of tritiated water were diluted to meet the 10 CFR 20 Appendix

B limit of < 1.0E-3 Ci/mL and released. However, in this case, the estimated 1,000 Ci of tritiated

water was released to the environment by evaporation. Refer to Figure 2-3 for comparison of the

TMI accident-generated tritiated water concentrations with those found throughout the tritium

complex.