ML20012C929
| ML20012C929 | |
| Person / Time | |
|---|---|
| Issue date: | 03/18/1990 |
| From: | Hurt R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20012C912 | List: |
| References | |
| REF-PROJ-M-32 NUDOCS 9003260129 | |
| Download: ML20012C929 (3) | |
Text
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o UNITED STATES
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WASHINoToN, D. C. 20555 j/
MAR 181990
- ROTE TO FILE:
FROM:
R. Davis Hurt, West Valley Project Manager
SUBJECT:
WEST VALLEY VITRIFICATION OFF-GASES
-This is a preliminary review of the vitrification off gases to be expected at the West Valley Demonstration Project (WVDP).
Vitrification is the process that will'be used to incorporate high-level radioactive waste (HLW) into borosilicate glass.
In this case, it will involve slowly feeding a HLW slurry.
onto the top of a pool of molten glass.
The inventory of radioacti6ity that' __
will be fed to the glass melter will be large (in excess of 27 million curies) and the potential for the generation of radioactive off gas in such a high-temperature process is clear. The conclusion of this preliminary review is that the WVDP off gas treatment system will in all likelihood be adequate to reduce concentrations of radioactivity in the off gas to the necessary degree._ The text of.the review will attempt to justify this conclusion and to explain where there are still areas of uncertainty.
The review considers the twelve radioisotopes most likely to come to mind as potentially important off gas constituents.
The twelve are either volatile at molten glass te'mperatures (approximately 1175 C in this case), present in large quantities, or-especially hazardous as airborne contaminants.
The text that follows considers the isotopes one at a time, in order of increasing atomic weight._ They are H-3, C-14, Sr-90, Tc-99, Ru-106, I-129, Cs-137, Pu-238, Pu-239, Pu-240, Pu-241, and Am-241.
For each isotope there is an estimate of its inventory-(specifically, how many curies of that isotope can be expected to reach the melter), a discussion of the degree of confidence associated with the inventory estimate, and a discussion of the relative significance of the isotope as'an off gas component.
- Significance" in this instance is meant to-indicate the extent to which the concentration of a particular isotope in the off gas must be reduced.
For some isotopes (H-3 and C-14) the inventories fed to the melter will be so small that even with no off gas treatment system their stack concentrations-(that is, their concentrations in air exhausted from the vitrification facility) would be expected to be below their respective 10 CFR 20 site boundary limits.
These isotopes are labeled in the following review as " low" in significance.
Pending-resolution of a few uncertainties discussed in the sections on those isotopes, it-should not be necessary to consider them further or to concern ourselves with the particularities of how they behave in the vitrification process.
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-P-For a second group of-isotopes (Tc-99, Ru-106, 1-1?9, and the plutonium isotopes) 3 stack concentrations would exceed the Part 20 limits if there were no off-gas treatment system, although concentrations at the site boundary, which is normally the point of interest and is the point at which the Part 20 limits would apply, would-be below Part 20 because of dilution effects.
(Dispersion 5
will reduce airborne concentrations by a least a factor of 10 between the stack and the site boundary at West Valley.) For this intermediate group of isotopes, good off-gas system performance is desirable but not absolutely essential, and-these are labeled as of " moderate" significance.
For a third' group (Sr-90, Cs-137, and Am-241) it is essential that the off-gas system achieve a substantial degree of decontamination. These isotopes are present in large enough quantities that their concentrations at the site boundary would probably exceed Part 20 limits if there were no off-gas treatment,-
.and they are therefore labeled in the following review as having a "high" significance as off-gas components, it is rqy suggestion that future staff who perform an evaluation of the WVDP vitrification off-gas system concentrate on these three isotopes.
The reference UVDP vitrification off-gas system consists of, in this order, a submerged-bed. scrubber (SBS), a high-efficiency mist eliminator (HEME), and, probably, two high-efficiency particulate air (HEPA) filters in series. The important features of these pieces of equipment will be discussed where necessary in the following review.
The main sources of information I have used are the following documents.
1.
L. E. Rykken, "High-Level Waste Characterization at
~
West Valley," 00E/NE/44139-14, June 1986.
2.
" Status of the Vitrification Off-Gas System," viewgraph package presented informally to R. D. Hurt at West Valley in April 1989.
3.
S. H. Brown, et al., " West Valley Demonstration Project Preliminary Safety Analysis Report - Volume III, Vitrification System, December 1986 4
J. M. Perez, Jr., et al., " West Valley Pilot-Scale Melter Experiment PSCH-19/19E Run Summary," 7H35-85-2, Pacific Northwest Laboratory, January 1985.
5.
R. W. Goles and C. M. Andersen, "LFCM Emission and Off-Gas System Performance for Feed Component Cesium," Proceedinos of the American Nuclear Society International Topical Meeting on Waste Management and Decommissioning, September 1986.
"4 i'
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Savannah River Plant and Laboratory, " Waste Management Program-Technical Progress Report, July-September 1981," DP-81-125-3, June 1982.
7.
Savannah River Plant and Laboratory, " Waste Management Program Technical Progress Report, January-March 1983," DP-83-125-1, September 1983.
8.
Savannah River Plant and Laboratory, " Waste Management Program Technical Progress Report, January-March 1984'," DP-84-125-1, December 1984.
9.
Savannah River Plant and Laboratory, " Waste Management Program Technical Progress Report, October-Docember 1982," DP-82-125-4, July 1983.
10.
U.S. Department of Energy, Office of Civilian Radioactive Waste Management, " Characteristics of Spent Fuel, High-Level Waste, and Other Radioactive Wastes Which May Require Long-Term Isolation," 00E/RW-0184, December 1987.
All of these'except the second are publically available documents.
I used the informal viewgraph package (item number 2 above) because the Safety Analysis Report on the vitrification system (item number 3) is out of date on some-subjects'and is being updated by the WVDP.
O..U U R. Davis Hurt West Valley Project Manager Advanced Fuel and Special Facilities Section Fuel Cycle Safety Branch Encloure:
Review of WVDP Vitrification Off-Gases Distribution:
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