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Conf. 660904. 1
SEP 22 18
ORNL - AEC - OFFICIAL
CFSTI PRICES
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MASTER
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.
IN-PIACE IODINE FILTER TESTING
J. H. Swanks
Oak Ridge National Laboratory
Prepared for Presentation
at the
Ninth AEC Air Cleaning Conference
*Operated by the Union Carbide Corporation for the U. S. Atomic
Energy Commission
LEGAL NOTICE
DONI - AFC - OFFICIAL
RELEASED FOR ANNOUNCEMENT
the report was prepared u an account of Government sponsored work. Noltbor the United
Stalas, por the Commission, oor way po7800 acung od behalf of the Cominsandoa:
A. Makes my warranty or representadon, expressed or implied, with respect to the accu-
racy, compiettaess, or wel 'ness of the information contaipod in this report, or that the wo
o: any information, apparatu, method, or process declosed in Wlo report may not talriaco
printely owed righto; or
B. Assumes way Habillues with respect to the use of, or for damages ronidos from the
One of way information, apparatus, method, or process disclosod in while report
Au used in the abovo, "person acting on behalf of the Commissioa" lncludra my one
ployee or contractor of obe Commission, or employde of such contractor, to the extent that
ruch employee or contractor of the Commission, or employee of such coolractor preparus,
dierontaates, or provides accons to, may Informauca purmuat to do employmeat or contract
with the Commission, or his employment wild such contractor.
ORNL - AEC - OFFICIAL

DI MUCLEAR SCIENCE ABSTRACTS
:

.
ORNI - AEC - OFFICIAL
ORNI - AEC - OFFICIAL
2 9A
IN-PLACE IODINE FILTER TESTING
...
. - .
J. H. Swanks
.
.
Oak Ridge National Laboratory*
-
...
ABSTRACT
A series of in-place iodine filter tests was performed
on the charcoal iodine filters at the High Flux Isotope
Reactor. Two sets of charcoal filters were tested - the
first for elemental iodine retention and the second for
methyl iodide and elemental iodine retention. This paper
presents the results of those tests and discusses the con-
clusions drawn from those results.
INTRODUCTION
At the Oak Ridge National Laboratory charcoal filters are used in various
air-decontamination systems which must prevent releases of radioactive iodine to
the atmosphere; and, as integral parts of those systems, the charcoal filters
must be reliable components whose efficiencies are known. In order to determine
theso efficiencies, in-place tests are performed on the filters immediately after
their installation and periodically thereafter.
The purpose of this paper is twofold. The first is to consider these tests
with respect to the general techniques, problems, and limitations involved with
special emphasis or methods of obtaining and analyzing the data. The second
purpose is to emphasize the necessity for performing the in situ experiments. It
is erroneous to assume that the mere installation of a set of properly designed
and pretested filters is adequate; because manufacturing techniques, instaliacion
procedures, filter loading or poisoning, and other factors significantly affect
efficiencies.
In general, the efficiency tests, as performed at ORNL involve releasing a
radioactive isotope of iodine into a system at some point upstream from the fil-
ter unit being tested. Then samples of the air-iodine mixture are withdrawn into
small charcoal-filled sampling traps from points upstream sat downstream from the
ORNI - AEC - OFFICIAL
*Operated by the Union Carbide Corporation for the U. S. Atomic Energy
Commission.
ORNL - AEC - OF SICIAL
filter unit. The radioactive iodine content of the traps is determined by spec-
tral analysis techniques, and each filter unit's efficiency is derived from the
amount of radioiodine collected by the two sampling traps.
ORNL - AEC - OFFICIAL
A series of these iodine filter tests was performed on the charcoal filters
at the High Flux Isotope Reactor (HFIR). The following description of those
tests illustrates the methods used in testing at ORNI, and the conclusions that
may be diawn from the tests.
DESCRIPTION OF HFIR TESTS
The HFIR: loys two separate systems for the disposal of radioactive gases
and for cleaning air which might become contaminated. As the primary element in
the dynamic containment system, the special building hot exhaust (SBHE) system
provides a method for the filtering and subsequent disposal of large amounts of
possibly contaminated air. Each of two separate segments of the SBHE draws
14,500 cfm of air from areas of the reactor building which contain potential
sources of radioactive gases. In general, the SBHE system handles large quan-
tities of low-concentration effluents.
The second system, the hot off-gas (HOG) system, is actually a radioactive-
gas-disposal unit which handles normal gaseous releases from the subsystems of
the reactor such as the cooling system and from experiment facilities. It is
designed to handle small amounts of high-concentration effluents and is itself
made up of two components: the closed hot off-gas (CHCG) and the open hot off-
gas (OHOG) systems. The CHOG serves pressurized facilities, whereas the OHOG
serves only unpressurized ones. The maximum f100 in each component is 500 cfm.
Air from the SBHE and HOG systens passes through separate underground filter
assemblies and is then forced up a 250-ft stack. Each system has three parallel
filter assemblies or units (Figure 1). Under normal conditions any two of the
assemblies may be used, so that the third is in a standby condition. Manually
operated dampers are used to regulate and controi the path of flow. The two fil-
ter systems are very similar and consist of Fiberglas prefilters, absolute fil.
ters, silver plated copper woni filters, two charcoal iodine absorbers in series,
and another bank of absolute filters. Two main differences exist between the two
systems. The higher capacity SBHE system has a series arrangement of two banks
of twelve single charcoal filters in a 3 x 4 array, the HOG system has only two
single filters in series in each unit. The other difference is that the SBHE
system has conventional 24-in.. x 24-in. pleated-type charcoal filters and the
HOG systems have an arrangement of canister-type charcoal filters. The total
flow rates are equivalent to about 1240 cfm per single filter in the SBHE system
and 25 cfm per canister in the HOG system.
ORNL - AEC - OFFICIAL
The HFIR operating limits require that the iodine filters be tested at the
time of installation and semiannually thereafter. The tests described herein are
those performed after the installation of the first two sets of SBHE system fil-
ters. The first set was tested with elemental iodine, and the second set was
tested with methyl iodide as well as elemental iodine. The first SBHE filters
had nominally 1/2-in. thick activated charcoal beds contained between perforated
sheet metal plates, cadmium plated to inhibit corrosion. The HOG filters were
canisters having 3/4-10. thick beds of activated charcoal.
ORNI - AEC - OFFICIAL
ORNL - AEC - OFFICIAL
ORNL - AEC - OFFICIAL
-
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ORL=LR-DWG TITIORS
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OHOG FANS
OMGG DIVERSKON DAMPERS
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CHOG FANS
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SUVER-COPPER FILTEK
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MICOTICIENCY FILTER
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CHARCOAL MILTERS
FROM REACTOR BAY
HIGH-EFTIAENGT FILTER
MOEROLAS PREFILTER. -
BEAN AND EXPERIMENT ROOMS
SOME OIVERSION CAMPERS -
ORNI - AEC - OFFICIAL
*
ORNL - AEC - OFFICIAL
ORNI – AEC - OFFICIAL

OKNL - AEC - OFFICIAL
Iodine-131 was chosen as the radioactive isotope to be used in the tests
because, due to its 8.05-day half-life, there would be no real hurry to remove
and analyze the traps. For the fests on the SBHE system filters, 100 mg of sta-
ble 141 traced with 30 mc of but I were used. For the HCG, tests, the same amount
of carrier was used, but it was traced with only 15 mc of I.
The iodine sources were obtained from the ORNL Isotopes Division as elemen-
tal iodine crystals which were contained in a glass ampoule. The ampoule was
placed into the apparatus shown in Figure 2. This container served a twofold
purpose. It protected the ainpoule from breakage during transit to the testing
facility, and it served as an apparatus with which to inject the iodine into the
system being tested.
The injection tube was mounted in a glovebox wiich contained the rest of the
injection system (Figure 3) and the injection tube was connected to the system to
be tested. For the condi.ions existing at the HFIR, it was decided that no exact
requirements would be placed on the injection rate but that the iodine should be
injected at a reasonably constant rate over a period of about 15 minutes while
noraal flow and temperature conditions were maintained in the system being tested.
In order to release the iodire vapors into the system, a small air flow was es-
tablished through the injection tube. Then the thin-wall tubing of the injection
tube was mashed thereby breaking the glass ampoule. The air flow which had beer
previously established swept the iodine vapors from the crushed ampoule into the
system being tested. By gradually varying the flow rate, the rate of injection
was kept fairly constant; and, after the injection period, only an insignificant
amount of the iodine remained in the tube.
The air streams were sampled with sampling traps like those shown in Fig.
ure. 4. Activated charcoal was used as the iodine absorber. A11 of the other
parts of the sainplers were made of glass and stainless steel with the exception
of rubber O-rings used on each end of the glass pipes. The larger traps were
used during the tests on the SBHE system from which 14.5-cfm samples were drawn.
The smaller traps were used for the tests on the HOG system from which 1.5 cfm
samples were drawn. In both systems the samples were withdrawn immediately up-
stream and downstream from the filter assemblies through the sampling tubes which
extended to the centerline of the duct. It was assumed that complete mixing of
the air and iodine had taken place upstream from the first sampling point and
that the samples withdrawn were of the average concentration. Samples were drawn
simultaneously and continuously during the entire injection period and for approx-
imately two hours after the injection was begun. Thus any iodine that came off
the filters daring this two hours was detected in addition to that which passed
through the filters during the injection period.
After the sampling period, the traps were removed and disassembled for anal-
ysis. The charcoal was removed from the traps and divided into small quantities.
Then the inside of the traps were swabbed to remove any charcoal dust and iodine
that might have deposited on the surfaces. The individual charcoal samples and
the swabs were placed in petri dishes and counted separately with a gamma spec-
trometer. The radioiodine content of each sample was then determined, and the
total for the entire trap was obtained by summing the activities of the compon-
ents.
ORNI - AEC - OFFICIAL
ORNL - AEC - OFFICIAL
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ORNI - AEC - OFFICIAL

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ORNL - AEC - OFFICIAL
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NVIDIJOK
INIO
VI2140-331-INO.
· ORNL-DWG 66-6747
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TO EAST SBHE
NOTAMETER
FLEXIBLE TUBE
TO WEST SBHE
TO EAST HOG
TO WEST HOG
INJECTION
APPARATUS
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ORNL - AEC - OFFICIAL :
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ORNL - AEC - OFFICIAL
AEC - OFFICIAL ..mmg menyerang pangyayari
ORNI
ORNL – AEC - 9:"CAL
The results of the first series of tests are given in Table 1. The indi.-
cated decontamination factor (DF) is the simple ratio of the upstream to down-
stream iodine concer.trations and is related to the efficiency by the following
relation:
ORNL - AEC - OFFICIAL
te no
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Efficiency = 1 -
..
.
Table 1. Results of First Test of 1/2-Inch-Thick Filters
......
System Tested
Iodine Removal
Efficiency (%)
Decontamination
Factor (DE)
East SPHE
Standby SBHE.
West SBHE
99.06
99.62
99.40
106
260
166
4120
: East HOG
Standby HOG
West HOG
99.98
99.93
99.99
3700
8200
1
Upon examination of the results of these tests it was concluded that the
HOG filter systems performed satisfactorily and that no modification or further
· testing of those systems was necessary. However, the fact that the efficiencies
of the SBHE systems' filters were so low caused some concern, for it was felt
that their efficiencies should be on the order of 99.8% or greater. In order to
check the results of the first tests, another test was performed on the west bank
of SBHE filters. The results of this test were:
-
-
Efficiency = 38.9%
= 92
DF
In order to determine the cause of the low efficiencies, the filters were
removed from their compartments and inspected. Several large openings were ob-
served around the framework of the filters, 80 a large portion of the air stream
had been bypassing the filters.
The leaks around the filters were sealed, the filters were replaced in their
compartments, and more tests were performed. The results indicated in Table 2
were obtained from those tests. As may be noted here, sealing the leaks improved
the system efficiency somewhat, but the efficiencies were still lower than de-
sired.
.
-
.
•
Table 2. Results of Second Test of 1/2-Inch-Thick Filters
System Tested
Iodine Removal
Efficiency %.
Decontamination
Factor (DE)
ORNL - AEC - OFFICIAL
East SBHB
Standby SBHE
Best SBHE
ORNL - AEC - OFFICIAL
99.65
99.75
99.77
263
397
442

In order to determine whether or not the fault lay in the thickness of the
charcoal. filters, a comparison was made between the results of tests run on two
1/2-in-thick HFIR charcoal filters and two 3/4-in. filters which were available.
Identical conditions were maintained while running the tests of the two types of
filters and the results shown in Table 3 were obtained.
ORNI - AEC - OFFICIAL
Table 3. Results of Comparison Tests
System Tested
Iodine Removal
Efficiency (%)
Decontaminatior.
Factor (DE)
1/2-in. filters
99.67
303
3/4-in. filters
99.94
1730
-
.-
.
--
-
-
-
-
Due to the low efficie.icies of the 1/2-in.-thick filters and due to a etudy
regarding the methyl iodide hazards at the HFIR, it was decided to replace the
1/2-in.-thick filters with a new set of thicker filters. The new filters are
made of perforated stainless steel witn an impregnated activated char::oal filler
which is nominally 1 1/8-in. thick.
Two types of iodine retention tests were performed on the new filters. They
were first tested for elemental iodine retention using the same procedures that
were used while testing the set of 1/2-in.-thick filters. In addition, the new
filter:r were tested for metliyl iodide retention. The sampling and analytical
techniques for the methyl tests were identical to those used in the elemental
tests, but the injection procedure had to be modified somewhat. The same quan-
tity of iodine was used as in the elemental tests except that it was in the form
of methyl iodide and was contained in a stainless steel U-tube. In order to
obtain a fairly uniform release rate, the U-tube was installed in the injection
apparatus, a delay tank was connected to the downstream side of the U-tube, and
the tank was connected to the system to be tested. A very small air flow was
established through the U-tube so that methyl iodide vapor moved into the delay
tank and then slowly flowed from the tank into the system being tested.
During the test on the west SBHE filters, the elemental iodine and methyl
iocide tests were run simultaneously by using elemental iodine-131 and methyl
jodide-130. By using both of the isotopes, only, one injection and sampling was
necessary. Spectral analyses of the samples allowed one to distinguish between
the UI and II isotopes during the analyses. The results of the test are
presented in 7able 4.
Table 4. Test Results of Stainless Steel Filters
in West SBHE
Type of Test
Iodine Removal
Bfficiency (%)
Decontamination
Factor (DE)
Elemental Iodine
98.55
47.37
ORNL - AEC - OFFICIAL
Meth:1 Iodide
1.9
ORNL - AEC - OFFICIAL
Considering these results, it was obvious that something was wrong with the
system because the original, thinner filters performed more efficiently than
these.
ORNI - AEC - OFFICIAL
The filters were inspected in place, and no leaks were evident. They were
then removed from their compartments, disassembled, and opened for examination.
Upon removal of the tops of the filters, the problem was seen immediately; the
charcoal had settled to such an extent that numerous air gaps had formed at the
top of the filters. A typical settled filter 18 shown in Figure 5. The filters
were refilled with the same type of charcoal, reinstalled in their compartments,
and retested. The results of the tests of all the SBHE systems are given in
Table 5.
Table 5. Results of Tests of Stainless Steel
SBHE Charcoal Filters
System Tested
Iodine Removal
Efficiency_(%.
Elemental
Methyl
Iodine
Decontamination Factor
Elemental Methyl
East SBHE
Standby SBHE
West SBHE
99.994
99.994
99.995
99.97
99.97
99.98
17,300
16,100
20,300
3,580
3,850
The absolute accuracy of the results of these tests 18 somewhat question-
able, for the activities in the downstream samplers were quite low. However,
the results are definitely conservative and the systems are at least as efficient
as these results indicate.
These tests 11lustrate that the filters perform quite satisfactorily for
both elemental iodine and meti:yl iodide. It, of course, still remains to be seen
CONCLUSIONS
Considering the results of the tests performed at the HFIR, several general
conclusions may be drawn.
If iodine test results indicate that a filter unit is inefficient, it re-
mains then to decide whether the inefficiency is due to poor charcoal filter
design, air leaks around the filters, loading and poisoning of the filters, or
some other fault. In other words, the mere fact that a test indicates a low
unit efficiency does not necessarily mean that the filters themselves are ineffi-
cient. They may indeed be, but one must carefully inspect the system to deter-
mine what fault or combination of faults causes the inefficiency. Generally, as
far as the results of the tests are concerned, no distinction can be made as to
what type of fault exists.
WWJIV
ORNI - AEC - OFFICIAL
In-place filter tests are the only reliable method of determining whether a
system wili perform as it was designed; however, the methods and procedures used
in performing those tests are essential in obtaining valid, reliable results
10

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- OFFICIAL
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ORNL - AEC - OFFICIAL
which are necessary to evaluate an installed system properly. Tests performed
under conditions different from those normally present in a system or with poor
regard for injection and sampling procedures are of questionable value and may
lead to erroneous conclusions.
ORNI - AEC - OFFICIAL
It must be recognized that various chemical forms of iodine may exist in a
system, and the capability of a filtration system for removing one of these forms
does not insure its capability for removing another. Systems to be tested must,
therefore, be investigated to determine what chemical forms of iodine might be
present and then the appropriate tests may be performed.
If the filter system is required to have a definite capability, then it is
imperative that the system actually be tested in situ in order to guarantee that
capability. Furthermore, periodic tests should be performed to determine whether
or not the system maintains its capability.
--
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ORNL - AEC - OFFICIAL
ORNL - AEC - OFFICIAL
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ORNI - AEC - OFFICIAL
1.
F. T. Binford and E. N. Cramer (Eds.), The High Flux Isotope Reactor: A
Functional Description, Vol. 1, USAEC Report ORNL-3572, Oak Ridge National
Laboratory, May 1964, Rev. March 1, 1965.
ORNL - AEC - OFFICIAL
Operating Safety Limits for the High Flux Isotope Reactor (HFIR).._(100 MW
Maximum Power), USAEC Report ORNL-TM-1532, Oak Ridge National Laboratory,
May 16, 1966.
3.
R. E. Adams, W. E. Browning, Jr., W. B. Cottrell, and G. W. Parker, The
Release and Adsorption of Methyl Iodide in the HFIR Maximum Credible
October 1, 1965.
-
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ORNL - AEC - OFFICIAL
ORNL - AEC - OFFICIAL

IND
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MATORI
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END
DATE FILMED
10/21 / 66




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TAN
1919,,T
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