ML19309E838
| ML19309E838 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/31/1980 |
| From: | Pollack G MICHIGAN STATE UNIV., EAST LANSING, MI |
| To: | Gilinsky V NRC COMMISSION (OCM) |
| Shared Package | |
| ML19309E835 | List: |
| References | |
| NUDOCS 8004240479 | |
| Download: ML19309E838 (6) | |
Text
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MICHIGAN STATE UNIVERSITY (Of IIGl. OF NATL RAL SCIENCE
- DI PARTMENT OF PHYSICS I AST LANSING
- MICIIIGAN
- 4M24 March 31,1980 The Honorable Victor Gilinsky Conmissioner US Nuclear Regulatory Commission 1717 H Street, NW Washington, DC 20555
Dear Dr. Gilinsky:
Here is my report on the suitability of the Selective Absorption Process System for removing Krypton-85* from the atmosphere of the reactor building of Unit 2 at Three Mile Island.
This is a follow-up to my previous report, of March 24, to you.
In order to prepare this and to learn more about the system at first-hand I visited and talked with the group which developed it at the Oak Ridge Gaseous Diffusion Plant. While I was there I examined as well as I could the pilot-plant scale system which they've constructed.
I also read and studied some of their reports.
I asked them many questions and I made the questions as probing as I could; I think that I have an accurate picture of their system and its properties.
My main conclusion is that the Selective Absorption Process System could be used to remove the Kr-85 from TMI-2 and would probably do an excel-lent job. My visit to the facility confirmed my opinion that Selective Absorption is the best choice of the five alternative methods for Kr-85 decontamination discussed in the NRC Staff Report's Environmental Assessment.
The Cryogenic Process System is the second best choice, in my opinion.
I do not have any first-hand experience with the Cryogenic Process System so this is still somewhat tentative. The Reactor Building ? urge is my third choice.
In view of what I learned about the Selective.ibsorption 8004240 yg
2 System, I 'think that there is probably no need to actively consider further the Charcoal Adsorption System or the Gas Compression System. These were, respectively, the fourth and fifth choices in my report of March 24.
I see now that they would have all of the disadvantages but none of the advantages of the Selective Absorption System.
The only disadvantage of the Selective Absorption System compared to any of the other four alternatives is that it would take longer and cost more than the Reactor Building Purge.
The advantage of Selective Absorption over purging is that it is a zero-release system and so would have minimal public and environnental effects.
I understand that during the time it would take to set up a decontamination system, emergencies could arise which would require that extensive work be done in the reactor atmosphere.
I haven't included this problem since I don't know its details.
In the main body of this report I shall discuss several of the scien-tific, engineering, and other aspects of the Selective Absorption System which bear on its use at TMI-2.
I have kept the discussions brief but I am prepared to provide you with quantitative details of any of the points.
A.
How the Selective Absorption System removes Kr-85 from a contaminated atmosphere.
Krypton is preferentially soluble in the common refrigerant Freon (a fluorocarbon, CCl F ).
The idea is to dissolve Kr-85 in a counterflowing 22 stream of liquid Freon.
The contaminated reactor atmosphere is fed into the absorption section of the system where the refrigerant is cold and absorbs Kr-85. Absorbed gas is carried by the stream to the stripping section of the system where the refrigerant is heated and therefore releases the Kr-85 and other volatile soluble contaminants into a collecting system.
[
The Kr-85 ultimately is concentrated in standard-sized gas cylinders.
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3 B.
What has been done with the system so far.
The group at the Oak Ridge Gaseous Diffusion Plant (ORGDP) has been working on the Selective Absorption System since about 1967.
From 1974-1978 they operated a second generation working, pilot-plant system (a three-stage system with separate columns for absorption, intermediate stripping and final stripping). They made extensive tests on studying, varying, and optimizing the parameters of this system in order to improve it and they have constrrcted a third generation pilot-plant system. This system is an improved, single-stage, system and has been operating for 1 1/2 years.
It is operated regularly now for 4 days a week.
It was working when I visited ORGDP and I examined it.
The principle motivation of the ORGDP group in developing this system was for use to treat and decontaminate the off gas from nuclear fuel reproc-essing plants. However, the system can also be straightforwardly adapted and used for cleaning radioactive atnospheres from a reactor accident such as the one at TMI-2. The relevant divisions at ORGDP have considered the problem of the TMI-2 reactor atmosphere decontamination and they have written a preliminary proposal on how they would go about it.
I read the proposal and the scientific and engineering parts seem to me to be solid.
There is a unique aspect of this Selective Absorption System which strengthens it. There are three people at ORGDP who have worked on the system extensively: Drs. J. R. Merriman, M. J. Stephenson, and B. E.
Kanak. A large fraction of their scientific careers t.s been involved with the system and it has been the subject of doctoral and master's degree theses. This means that the group has a firm, first principles, understanding of the system. I think that is an invaluable advantage to have in using the system and scaling it up.
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4 C.
What are the scientific and engineering considerations in using this system for the cleanup at TMI-2?
The Selective Absorption System that is proposed for use at TMI-2 would process about 250 Standard Cubic Feet per Minute (SCFM) of reactor atmosphere.
It would achieve 90% removal of Kr-85 on a single pass of atmosphere through the column and provisions could be made for recycling. Such a system would clean up the reactor atmosphere in about 60-70 days, once it was functioning in place.
The scale of the system that would have to be built for TMI-2 is naturally larger than the pi-lot-plant scale.
For example:
The present pilot plant uses absorption. column tubes that are 3" in diameter, whereas the TMI system would use tubes about 20" in diameter.
The pilot plant has a throughput of 15 SCFM compared"to 250 SCFM for the TMI system, as men-tioned above.
In my judgment this scale-up would cause no problems.
Because the system has built-in elasticity of design, it will probably be easy to optimize and, if necessary, trouble-shoot.
For example:
(a)
One can vary the pressure and temperature, presently planned at 125 psig and -30 F, since these regions are convenient to work in.
(b) One can vary the gas throughput rate as well as the solvent flow rate.
(c) In the pilot-plant scale, separations in a single pass of 99.9% for Kr-85 have been achieved but for application at TMI only 90% is required in a single pass.
(d) One can vary the number of cylinders and the pressure inside them for collection and final storage of the Kr-85; presently this is planned at about 5 standard cylinders at 500 psia.
There is one important point which, in rqy opinion, requires further experiment now.
That point is the different Kr concentration scale that we encounter at TMI-2 compared to the pilot plant. The pilot-plant system n
5 has been tested at Kr concentrations from 0.1 ppm to 880 ppm. However my calculations show that at TMI-2 the Kr-85 concentration now is 0.7 ppm and it will probably be necessary to reduce the total Kr levels to well below 0.1 ppm.
It is important to test the pilot-plant system at these lower levels to be sure that good separation factors can be achieved.
I am fairly confident that this will not be a serious problem but it must be tested.
D.
What is the cost and how long would it take to set up a Selective Absorption System at TMI-27 The people involved give cost estimates for the Selective Absorption cleanup of Kr-85 ranging from $4-20 million and estimated times from 1 1/2 to 4 years. The higher cost and longer time estimates are due to concerns they have about special expensive hardware, materials and techniques required for the system to be built and operated rigorously to nuclear code con-struction standards. The estimates also reflect their concerns about potential delays due to legal and political problems.
Finally there is feeling that there may be unforeseen delays and expenses associated with interactions between DOE and General Public Utilities and NRC.
In this connection it's natural to ask whether in the interests of economy and speed in the cleanup:
Is it possible to smooth these interactions?
Is it advisable to modify the construction standards?
In contrast it should be emphasized that scientific and engineering considerations alone are consistent, in my opinion, with a time of 1 1/2 years and a relatively low cost estimate.
The Selective Absorption System is less complicated than current automobile emissions systems,its principles of operation are simpler and it is easier to fix.
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E.
Other advantages associated with developing the Selective Absorption System for use at TMI-2.
(1) The system could be mobile.
One design proposed by ORGDP would fit on five trailers so that after use at TMI the system could be used at any future reactor accidents.
(2) Once the system is scaled up for use at TMT, it would be closer to the further scale up necessary for decontamination of off gases from operation of reprocessing plants. That is a problem that we shall soon have to solve and this is probably a good approach.
(3) The present system traps tritium (99.99% removal in a single pass).
Since there is a lot of tritium in the reactor building at TMI (3.6x10-5 Ci/cm ), one could use the same selective absorption system for 3
the tritium cleanup.
(4) Once the system were developed for use at TMI and should it prove as efficacious as anticipated in the cleanup, the portable system might be marketable worldwide (D0E has a patent on the process).
1 (5) Finally, and somewhat conjectural: The system collects and con-centrates Xe as well as Kr. This opens up the possibility that a Selective Absorption System could be used to decontaminate the off gases associated with normal operation of nuclear reactors. One might then be able to achieve essentially zero radioactive gas release from reactor operation.
I believe this would lead to better public acceptability of nuclear power.
Report submitted by, k
Gerald L. Pollack Professor of Physics ds a