ML20042D242
| ML20042D242 | |
| Person / Time | |
|---|---|
| Issue date: | 12/27/1989 |
| From: | Hurt R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Sjoblom G NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-PROJ-M-32 NUDOCS 9001080111 | |
| Download: ML20042D242 (4) | |
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MEMORANDUM FOR:
Glen L. Sjoblom, Acting Chief
_ Fuel Cycle Safety Branch Division of Industrial and
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Medical Nuclear Safety FROM:
R. Davis Hurt s
West Valley Project Manager Advanced Fuel and Special Facilities Section Fuel Cycle Safety Branch Division of Industrial and Medical Nuclear Safety
SUBJECT:
TRIP TO SAVt.NNAH RIVER SITE I visited the Savannah River Laboratory (SRL) on December 6, 1989, to discuss vitrification off gas treatment for the Defense Waste Processing Facility (DWPF) anti to see how-SRL's experience with vitrification off gasses might shed light on the West Valley Demonstration Projects' (WVDP) plans in this My main hosts were Ken Thames of the Department of Energy's Savannah area.
River Operations. office and Bruce Kitchen of 3RL.
I met with several SRL staff members working on off gas issues (see the enclosed list.), all of whom were generous with their time and knowledge.
The startup schedule for the DWPF is more-or-less the same as when I visited SRL last, in July 1988.. Cold runs will start in October 1990 and hot runs no later than mid-1992.
This puts the DWPF at least a year ahead of the WVDP in terms of hot vitrification, which is why it is useful for those of us interested in West-Valley to follow the DWPF's progress fairly closely.
The DWPF off gas system is very similar to West Valley's.
The two systems have most of the same types of equipment in the same sequence:
melter, film cooler, scrubber, high-efficiency mist eliminator, and two high-efficiency '
particulate air (HEPA) filters.
The melters will generate almost identical types of off gas, 'at least-in radiological terms.
There are some differences, though,-and these merit consideration.
First, the DWPF will use a steam-atomizer scrubber while the WVDP will use a submerged bed scrubber.
I asked the SRL staff about this difference, having discussed the same issue previously with staff from the WVDP and their contractors at Pacific Northwest Laboratories (PNL).
It seems that experience with both scrubbers has been good; neither has been a problem during test runs. West Valley chose to use a submerged bed scrubber at least partly because PNL recommended it.
PNL in turn had considered using other types of scrubbers for this application but decided that the passive nature of the submerged bed scrubber, plus successful experience with it elsewhere at Hanford, were a good recommendation.
The future Hanford vitrification plant will apparently also use a submerged bed scrubber.
The SRL staff did not dispute the selection of a submerged bed scrubber for West Valley, but chose the steam atomizer scrubber for their own use because they believe it is somewhat better at dissipating off gas surges,
&OQ1 691227 M-32 PDC
DEC 2 71M Glen L. Sjoblom,
A second difference between the processes is that the DWPF will have a sand filter af ter the HEPA filters as a final treatment component, while at West Valley the off gas will be vented to the environment directly after the E'.PA filters, at least as far as radiological treatment is concerned.
Sand filters are not common in the nuclear processing industry, but they are apparently somewhat of a tradition at the Savannah River site.
The DWPF' sand filter is very large, probably very expensive, and probably not appropriate for a relatively short-lifetime operation like the WVDP.
(West Valley vitrification is scheduled to least only a year and a half as opposed to many years of projected operation-for the DWPF.)
A third difference between the processes is that the DWPF will have a backup off gas system that almost completely duplicates the original, so when the main off gas line is shut down to change a filter or fix a piece of equipment, the melter can keep operating as normal.
West Valley will have only one off gas treatment system.
If it breaks down, the melter will presumably have e
to be shut down, too.
This is a calculated risk, but probably a reasonable cao for a facility with such a short operating life.
There a few areas where the SRL staff expects off-gas behavior or treatment equipment performance to be a little different from what we have heard at West Valley and PNL.
The SRL staff is not convinced that halogen concentrations in the melter will strongly influence cesium volatilization rates, in contrast to the PNL staff's opinion.
This question bears further enquiry since all parties agree that cesium volatilization will be the main challenge to the off gas system under almost all foreseeable circumstances.
Another area of disagreement is that the DWPF high efficiency mist eliminator will be operated wet (that is, with continuous washing of the filter medium), while PNL has experienced problems with wet operation and has recommended that the WVDP operate their equipment dry.
I am not certain at this point if the divergence l
of opinion can be explained by small differences in the designs of the mist eliminators used by the two groups.
This subject should also be investigated further.
One last point of interest:
both the DWPF and the WVDP will use two HEPA filters in series contained in a remotely replaceable jumper unit.
As far as can be determined at present, both parties plan to operate these units in the same way.
The HEPA filters will be di-octyi pthalate (DOP) tested in the jumper units to guarantee that the filters are seated properly.
Once the jumpers are placed in the cell, it will not be possible, at least during hot operation, to 00P test the filters again.
But if there were any leakage at the jumper connection points, it would only be leakage from the off gas line into-the cell atmosphere, so it would not really affect the performance of the off gas system as normally defined.
This seems to me a good way to handle the otherwise difficult question of how to leak test remotely emplaced filters and how to determine what credit to take for their effectiveness in our safety analysis.
For analysis purposes, the SRL staff is assuming a decontamination factor of 200 for the two HEPA filters together, which corresponds to a removal efficiency of 97.8 percent for each HEPA, a very conservative figure.
f DEC 2 71m j
Glen L. Sjoblom 3-
.I have not seen a definitive prediction for West Valley regarding their HEPA
' filter performance, but this will be an interesting point of comparison.
DW@@
b R. Davis Hurt West Valley Project Manager Advanced fuel and Special Facilities Section Fuel Cycle Safety Branch Division of Industrial and
-3 Medical Nuclear Safety
Enclosure:
Main contacts at SRL
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!!ain contacts during visit to Savannah River Laboratory (SRL)
December-6, 1989 Ken Thanes DOE /SRO Bruce Kitchen SRL Carol.Jantzen SRL Ray Novak SRL Chris Randall SRL Harcourt Bull SRL Noel Chapman Savannah River Plant t
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