1. Bench-Scale Treatability Testing in Support of Fukushima Accident Stabilization and Recovery Activities
W.D. Bostick, MCL, Inc.
M.S. Denton, Kurion, Inc.
J.L. Mertz, Kurion, Inc.

2. J. Nucl. Mater. Mgt, Summer 2011 Fukushima Units 1-3 BWR
Tsunami and subsequent earthquake damaged buildings, caused loss of AC power (with loss of cooling water supplied to reactor cores).
Partial meltdown of core releases fission products.
Additional structural damage after hydrogen explosions.
Seawater was injected to provide emergency core cooling.
Damaged facilities are left with millions of gallons of highly radioactive seawater in basements, now admixed with turbine oil.

3. Reported radionuclide activities found early in the recovery process
Reported values for Select Radionuclides at Fukushima 1 Daiichi Nuclear Power Plant (2011)* *
Nuclide
Specific Activity
(Bq/g)
Reference Value
Bq/mL
g/mL
Source
Cs-137
3.20 x 1012
1.80 x 106
5.63 x 10-7
Basement, unit #1
(March 25, 2011)
3.00 x 106
9.38 x 10-7
Basement, unit #2
(April 19, 2011)
I-131
4.64 x 1015
2.10 x 105
4.53 x 10-11
1.30 x 107
2.80 x 10-9
Other radionuclides are present, but are hard to estimate

4. Some Water Treatability Issues
Fission product nuclides of immediate health concern (initially > 1E+06 Bq/mL):
Cs-137 (beta/gamma, half-life ~ 30 y; decays to nonradioactive Ba) – analog is natural Cs+ (1 ppm total Cs is equivalent to ~ 3.2E+06 Bq/mL as Cs-137)
I-131 (beta, half-life ~ 8-d; decays to nonradioactive Xe) – analog is natural I (primarily as I- and/or IO3-)
High salinity (Na+ competes with Cs+ on most treatment media, including zeolites)
Oil and grease (10 to >> 200 ppm) can coat binding sites on all treatment media
Concerns are radiation dose (affects shielding requirements) and ultimate decay heat production. TEPCO data indicated that Kurion AGZ removes ~ 85% of I-131, sugesting that iodide is predominant form.

5. Cs+ >> Sr2+ > Ca2+ > Mg2+ > Na+
Herschelite
Immediately available from Kurion and economical in the large quantities required for emergency response;
Similar media were the historic “workhorse” for reducing high dose and heat-generating radionuclides (Cs-137 & Sr-89/90) in waste waters from TMI accident.
Cation selectivity is generally in the order:
Cs+ >> Sr2+ > Ca2+ > Mg2+ > Na+
Natural seawater has very high Na (~ 10,000 ppm), moderate Sr (~ 10 ppm), low I (~ 0.06 ppm) and very low Cs (~ ppm)
Ag+ also has a high affinity for chabazite

6. Proposed Treatment Flow Chart
Oil skimmer – to remove the bulk of the turbine oil contaminant;
Surface-modified zeolite (SMZ) – sacrificial medium to remove residual entrained oil;
Herschelite(KUR-H) – high-grade for bulk Cs+ removal (within heavily shielded columns);
Silver modified Herschelite (KUR-AGH) – selective for radioiodine as iodide.
Some other media, more costly and in short supply, are more selective for Cs over Na, and may have a role as an effluent “polishing” agent after the bulk of Cs-137 has been removed.

7. Surface-Modified Zeolite (Affinity for anions and oil)
Robert Bowman (New Mexico Tech.): HDTMA exposed to a negatively charged zeolite surface will form admicelles. The sorbed surfactant creates an organic-rich layer on the zeolite surface, and the charge on the surface is reversed from negative to positive.
Commercial product by St. Cloud Mining has been used in recovery efforts to remove spilled petroleum from seawater
SMZ is multi-functional (“AC/DC”), also retaining substantial ability to bind cations. High affinity to remove O&G. “Mule” is a low-grade zeolite (less affinity for cesium ion)

8. Distribution (Kd) Coefficient as Figure-of-Merit
The distribution coefficient (Kd, mL/g) describes the partitioning of contaminant from aqueous solution (volume V) to a solid phase (sorbent, mass M)
Can be estimated by mass-balance from batch-tests:
Kd (mL/g) = C(solid, g/g)/C(liquid, g/mL)
=(F/(1-F)*(V, mL)/(M,g)
𝐾 𝑑 = 𝑉 𝑚 𝐹 (1−𝐹) , 𝐹=1− 𝐴 𝐴 0
(F = fraction of contaminant left in solution)
Use to predict contaminant loading in spent medium
(e.g., Ci/ ft3, and hence estimates for shielding requirements, heat generation potential, etc.);
Use to estimate column breakthrough (operational life)
At the highest level of Cs-137 (~ 1E+06 Bq/mL) in SW, Herschelite has the capacity to load > 100 Ci/ft3

9. From July, 2011 (http://www. ndreport
TEPCO says about 3,000 m3 of radioactive seawater has been stagnant in the basements of the plant’s reactor and turbine buildings since being hit by the tsunami.
More than 110,000 tons of highly radioactive water has accumulated on the plant’s basements and tunnels with more accumulating every day.
The amount is growing by 500 tons/day as freshwater is injected into reactors, and injected and sprayed into the fuel pools in an effort to keep them covered and cool.

10. Effect of salinity on uptake of Cs-137 by select media
In diluted seawater (with competing Na+), the Kd value for H-G is ~ 12-times that of SMZ.

11. Removal of Radioiodine by Silver Modified Herschelite (KUR-AGH)
Silver ion can precipitate iodide in seawater
In seawater, AgCl will be more soluble due to formation of higher chloride complexes
AgCl(s) + nCl- ↔ AgCl(n+1)n- (n < 3)
Solute Name
Formula
Ksp
Silver Iodate
AgIO3
3.0 X 10-8
Silver Chloride
AgCl
1.8 x 10-10
Silver Iodide
AgI
8.5 X 10-17
Solubility data are for DIW; AgCl is more soluble in seawater, due to formation of anionic silver chloride complexes. Site test results suggest that AGH removes ~ 85% of radio-iodine (infers that iodide is predominant species)

12. Removal of traced iodide (as I-129) from synthetic seawater using AGH

13. Full-Scale Operation vs. Scoping Studies
Multiple treatment lines have been operating on-site (~ 200 GPM total) for several months;
On-site performance tracks well with bench-scale scoping study expectations, which had used radioactive tracers or natural analogs in synthetic seawater;
Additional bench-scale tests have been performed, as-requested, to address field operational or regulatory questions.

14. Herschelite treatment skids for cesium removal (From Nuclear Decommissioning Report)

15. Summary
Use of commercial synthetic seawater (“Instant Ocean™”) and natural analogs of priority radionuclides allowed rapid, remote estimation of key treatment design parameters;
At-site testing with authentic contaminated seawater was consistent with the surrogate test results.