ML19305A671

Proceedings of Fifteenth DOE Nuclear Air Cleaning Conference, Held in Boston,Ma on 780807-10.Summary of NRC Effects of Atmospheric Contaminants on Commercial Charcoals, Encl

ML19305A671
Person / Time
Site:	Crane
Issue date:	02/28/1979
From:	First M ENERGY, DEPT. OF
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References
TASK-TF, TASK-TMR NUDOCS 8001160739
Download: ML19305A671 (15)

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W 15th DOE NUCLEAR AIR CLEANING CONFERENCE yfl

~

w

' $o CONFIRMATORY RESEARCH PROGRAM -

N EFFECTS OF ATM0SPMERIC CONTAMINANTS 6

ON COMMERCIAL CHARC0ALS

• rc S

Ronald R. Bellamy U.S. Nuclear Regulatory Commission Washington, D.C.

20555 S

[

Victor R. Deitz 0

Naval Research Laboratory Washington, D.C.

20315

[<

.I ABSTRACT The increased use of activated charcoals in engineered-safety-feature and normal ventilation systems of nuclear power stations to continually remove radiciodine g

from flowing air prior to release to the environment has added importance to the

.L question of the effect of atmosphcric contaminants on the useful life of the char-coal.

In January of 1977 the Naval Research Laboratory (NRL) began an investiga-tion ** to determine the extent to which atmospheric contaminants in ambient con-centrations degrade the efficiency of various commercially-available charcoals for removing methyl iodide. AreportsummarizingtheFY77efforthasbeenpuh:jshedas This l

NUREG/CR-0025, " Effects of Weathering on Impregnant Charcoal Performance.t 1

caper will briefly sumarize that report and present the results available from the j

~Y78 investigations.

i approach employed by NRL is two-fold. First, charcoal samples are exposed to j

The unmodified outdoor air for periods of one to nine months, then examined for methyl iodide rete.* ion, increase in weight, and the pH of water extract. The atmospheric contaminants are identified by the NRL Air Quality Monitoring Station, and concea-trations of the various contaminants (ozone, 502, NO, C0g, methane and total l

2 hydrocarbons) are also available. Moisture content data is obtained from a neigh-t boring station (Washington National Airport) of the U.S. Department of Commerce.

Second, additional charcoal s mples are exposed to the same pollutants under con-trolled laboratory conditions in various pollutant combinations.

Results from FY77 indicate that the water vapor-charcoal interaction is an impor-tant factor in the degradation of the commercial charcoals. Laboratory results indicate the pollutant sulfur dioxide plus water vapor can result in significant charcoal deterioration, as did ozone plus water vapor. Conversely, carbon monoxide did not appear to affect the charcoal. Also, differences were. observed for various charcoals. The FY78 laboratory work will expand the pollutants to include a hydro-carbon mixture, use various concentrations of pollutants, verify differences in j

i charcoals, and attempt to determine if the effects are because of the base charcoal, the impregnation, or both.

j 1

O

• Paper to be presented at the 15th DOE Air Cleaning Conference, Boston, Mass, August 7-10, 1978.

• • Work performed under contract for the U.S. Nuclear Regulatory Comission under Interagency Agreement No. AT(49-24)-9006.

i 294 l

e 15th DOE NUCLEAR AIR CLEANING CONFERENCE' I

L, The outcoor' exposures at NRL consider the-integrated and accumulative effect of the i

~

pollutants. FY77 results. indicate-more degradation after three months than after 2

one month exposure for the same charco:1; FY78 results will extend the exposure F

time to nine months for various charcoals. FY77 preliminaryresults indicate two O

different charcoals differ in their ability to survive the weathering process over

' time; FY78 results will include up to twelve different charcoals.

s'

[

s This paper will discuss the progressive effect of the pollutants through the char-p p

coal bed. Both the laboratory and outdoor samples were layered to allow analysis.

[

of weight increase, methyl iodide removal, and pH of water extract as a function of y

bed depth..These results on exposed charcoals are compared to the known semi-log-0 q

(

arithmic dependance of decrease in penetration with increased bed depth for unex-

[I i[

posed charcoals.

k This paper will also present the proposed scope of work for the remainder of FY78

[

and FY79, including a discussion of plans to examine the weathering effects exhib-

'~

{

ited by spent charcoals of known history from power reactors.

I.

INTRODUCTION The impregnated activated carbon installed in engi'neered-safety-feature and normal ventilation systems at nuclear power stations to remove radiciodine prior to re-lease to the environment will not adsorb radiciodine indefinitely. The active i

sites on the carbon surface have a finite capacity for adsorption, and once that q

a:

capacity is reached, the carbon is saturated and will no longer remove radiciodine 4i from flowing air. The adsorption sites can be blocked by atmospheric contaminants, l

quickly destroying the adsorption capacity of the carbon. Comonly termed "weath-

,j

]C ering", there has not been (as of January 1977) an in-depth engineering analysis of the problem, to determine the extent to which atmospheric contaminants in ambient concentrations degrade the efficiency of various consnercially -'available charcoals l

for removing radioiodine. Recognizing this deficiency, the U.S. Nuclear Regulatory Commission contracted with the Naval Research Laboratory to perform such confirm-3j' atory research. Results on various carbons are not to be interpreted as a recom-

'i mendation of any manufacturer's carbon, but are presented to illustrate the effect of the carbon base and impregnant. This paper will discuss the results obtained to date, the work in progress, and the experiments planned for the remainder of the fiscal year, 1978, and 1979.

3 A two-fold approach has been undertaken to obtain the necessary data. First, char-coal samples are exposed to unmodified outdoor air for various periods of time, and then examined for changes in methyl iodide retention capability, weight and pH of water extract. This approach allows no control over'the concentration or type of atmospheric contamina~nt. Second, additional charcoal samples (of the same char-y coal as used for the outdoor exposures) are exposed to the same pollutants under controlled laboratory conditions in various pollutant combinations. This approach

,j i

allows pollutant types, concentrations, and combinations to be varied and con-

'1 trolled under the discretion of the investigator.

'L q

II. Accomplishment in Fiscal Year 1977

]

There are two' elements of the procedure for analysis of weathered samples that can significantly affect the results and conclusions, yet are unrelated to the weath-t ering phenomenon. The first is related to the preparation of weathered samples-

'I for' subsequent laboratory analysis for methyl iodide retention, the second is j

g related to the laboratory procedures employed for the methyl iodide retention s

analysis.

I l

i 300 kh

15th DOE NUCLEAR AIR CLEANING CONFERENCE 1

There are three methods available for preparation of weathered samples for lab-N cratory methyl iodide analysis:

A.

The weathered samples are prepared in four separate layers, each

)

4 inches in diameter and 0.5 in hes high. Each layer may be tested y

separately and independently by transferring each layer (with mixing) to a test canister 2 inches in diameter and 2 inches high.

4 f

1 i

B.

One-fourth of each layer of the weathered sample can be used to 1

I construct a test bed in which the same sequence of entrance to

?

[

exit is preserved in the bed, again yielding a test canister 2

)

inches in diameter and 2 inches high.

[

C.

Examine the weathered sample without removal of the charcoal from the exposure configuration. This requires exposure' canisters 2 inches in diameter and 2 inches high which are presently being 6

fabricated.

t The preferred procedure depends on the information that is desired. Procedure A yields information on the gradient within the bed brought about by weathering, while Procedures B and C yield information on the lifetime of the exposed carbon.

Results to date have been determined using Procedure A, in order to elicit as much information as possible from one weathering exposure.

The second element that will effect the results but is not directly associated with g

the weathering phenomenon is the laboratory procciure employed for the methyl 6

iodide retention analysis. Testing procedyrgs are being established by the k

American Society for Testing and Materialst21 (ASTM) for both new (unexposed) and t

weathered carbons. For laboratory determination of methyl iodide penetration for new carbons, the test temperatures, relative humidities and periods of equili-bration (with water vapor), feed (with methyl iodide), and purge (with air) are well-defined. However, the proposed procedures for testing of weathered carbons are only preliminary, and are being tried in various laboratories today.

y 8

As Table 1 illustrates, for new carbons there is considerably less penetration t

without prehumidification (the charcoals performed better). This effect is reversed for exposed carbons, as the prehumidification period cleans and regen-i erates the carbon, leading to better performance with prehumidification. Accord-ingly, the proposed ASTM procedures recommend static temperature equilibrium with no flow. This results in temperature excursions of 20*C or m

?

airentersthecharcoalbed,duetotheheatofadsorption.(3$rewhenthe95%RH To obtain consis-L tent results, NRL weathered samples are today being prehumidified for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or f

until the temperature rise is less than 1*C.

I 1

l An alternate procedure under investigation is to statically equilibrate the carbon I

v in an oven containing a water source until the carbon has adsorbed sufficient moisture to eliminate any significant temperature excursion.

l I

A..

Exposures To Outdoor Air In FY77 there were 8 different commercially-available charcoals weathered on the roof of the NRL Chemistry Building. Most of those were only exposed for one month, however, there were two carbons exposed for periods of one, two, and three months to examine accumulative effects. Samples of the same charcoal were exposed for

?

various one-month periods to analyze monthly weathering variations, and different charcoals were exposed for the same one-month period to begin an analysis of the effect of the base material and impregnant complex. FY77 results will be briefly 301 A

+a

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, ~., _

15th DOE NUCLEAR AIR CLEANING CONFEREl4CE a

1I

'l TABLE 1

,1 J

METHYL-IODIDE PENETRATION FOR NEW C0CONUT-BASE 4,

COMMERCIAL CHARC0ALS AT 21'C-

'l '

3i 1

1 i

j 'l 1

Penetration, Y, Water i

Nominal Extract Prehumidification Size pH 16 Hours None i

i BC 717 8 X 16 9.5 0.99 0.05 BC 727 8 X 16 9.5 4.8, 4.0 0.014 i

MSA 463563 8 X 16 8.5 2.5 0.13 g

h NAC k G-615 8 X 16 9.8~

0.27, 0.23 0.05 NACAR G-617 8 X 16 9.3 3.8 0.1 NACAR G-617-A 8 X 16 9.3 5.7 0.07 discussed to aid in the explanation of the work in progress and future plans.

The two charcoals for periods one, two and three months r

(cocoanut base with KI and TEDA impregnant).

The entrance layer showed the greatest degradation for all tests, both in p 4

higher penetration of methyl iodide and a lower pH of the water extract.t )

The charcoal in the three subsequent layers exhibited less penetration than the However, there first layer, indicating.the initial layer acting as a guard bed.is Of these two charcoals, NACAR G-615 performed better than

. unexposed charcoals.

Additional tests are required BC-727 for.the same exposure period (Table 2).

before the role of the impregnation complex can be identified with confidence.

Also, an increase in exposure time resulted in greater penetration for the first i

In general the longer exposure bed. layer, but not always in subsequent layers.

These results are presented time did' weather the entire bed to a greater extent.

in Table 2.

Identical charcoals exposed different months showed that dryer mo less weathering than wet months.

to _the total water vapor content during the month, or the water vapor contentIt

~during the last 2-3 days prior to termination of weathering.

study this effect in the laboratory under controlled conditions.

(

c 302 1

t 1 ~

t-IH 15th DOE NUCLEAR AIR CLEANINB C@NFERENCE y

H M

TABLE 2 0,

h GRADIENTS IN THE PENETRATIONS (P) 0F METHYL I0DIDE 3N AND THE pH OF WATER EXTRACTS ?

1 1, 2, AND 3 MONTHS EXPOSURE b

First Layer Second Layer Third Layer Fourth Layer

]f Exposure pH P

pH P

pH P

pH P_

.t i

NACAR G-615 f

5016 1 month 9.3 1.77 9.5 0.64 9.6 0.34 9.7 0,70 4

5031 2

8.2 3.42 9.8 1.32 10.0 0.86 10.0 1.02 i,4f.

5022 3 7.5 8.62 9.8 1.38 10.0 1.19 10.0 0.81 e

BC 727 L:

5014 1 month 8.8 2.67 9.3 1.20 9.3 0.68 9.3 1.31 5032 2 7.3 5.81 9.3 2.58 9.5 3.09 9.5 3.45 L'

~

(

5020 3 7.0 21.6 9.4 5.4 9.5 5.0 9.5 cia i

Available data for pollutant concentrations at NRL were obtained from the' NRL Air The pollutants identified and the range of monthly Quality Monitoring Station.

average concentrations inlude ozone (0.007 to 0.04 volume parts per million),

f sulfur dioxide (0.020 to 0.052 ppm), nitrogen dioxide (0.018 to 0.12 ppm), total hydrocarbons (1.8 to 3.1 ppm), methane (1.5 to 2.5 ppm), and carbon monoxide (0.6 to 1.9 ppm). For one-month continuous exposures these concentrations yield integrated insults on the order of hundredths of grams (see Table 18 in Reference i

i 1).

t f

B.

Laboratory Exposures Concentrations of pollutants for laboratory exposures were chosen in an attempt to represent the magnitudes prevalent in the outdoor exposures. Water vapor was added since in magnitude the water vapor constituent is present in far greater amounts than any other pollutant (kilograms for 100-hour exposures compared to grams for one-monthexposures). Of the many possible combinations of pollutants to study, i

FY77 work was limited to single component (water vapor) weathering or binary mixtures (water-vapor plus contaminant).

In ' addition, only two charcoals (BC-727

(

and NACAR G-615) have been examined.

Testing with water vapor as the only pollutant was performed at 50, 70 and 90% RH.

P The carbons increased in weight by approximately 50% af ter 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> exposure.

Significant penetrations of methyl iodide were observed, as high as 16% for the entrance layer of BC 727; pH of water extract values did not drop significantly.

y In the cases evaluated, the NACAR G-615 carbon performed better than the BC-727 e

'30 3

15th DOE NUOLEAR AIR CLEANING CONFERENCE

?

carbon (Table 9a in Reference 1), but these are only two of the carbons to be tested, and no conclusion as to a more suitable carbon or impregnant can be made at this time.

A water vapor (70 and 90% RE) plus sulfur dioxide (0.5 ppm 502) combination was used to weather the two carbons for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

In all cases, no sulfur dioxide was evident in the exit gases from the test. bed, and the penetrations of methyl iodide (as high as 66% for the first layer) and the pH of water extract values (as low as 2.7 for the first layer) indicate drastic deterioration of the carbon.

Total S02 insult was determined to be approximately 0.75 gm, which is significantly higher (by approximately a factor of 10) than expected due to ambient concentra-tions. Future work will attempt to reach the expected ambient concentration in l

the insult mixture.

Similarly to sulfur dioxide, no ozone was detectec' in the exit gases when 1-3 ppm were combined with 70 and 90% RH air. High penetrations for methyl iodide were observed (as high as 21.5% for the fourth layer), but pH valves were not signifi-cantiy affected (Table 9b of Reference 1). Lower inlet concentrations will be achieved in future work.

1 Converse to sulfur dioxide and ozone, carbon monoxide (2.5 ppm in 90% RH air),

passed through the charcoal unadsorbed. No change in carbon monoxide concentration from inlet to outlet of the test bed was observed.

In summary, the laboratory results obtained in FY77 show that the three pollutants water vapor, water vapor plus sulfur dioxide, and water vapor plus ozone degrade the two charcoals significantly in a short time, while carbon monoxide showed no degradation of the carbon.

III. Work in Progress and Results Present efforts are directed towards weathering various carbons to outdoor exposures and to laboratory pollutant mixtures.

A.

Exposures to Outdoor Air Outdoor exposures are obtained by drawing air thro 0gh the carbon samples as explained in Reference 1.

The number of independent exposure positions has been increased to allow 12 samples to be weathered simultaneously.

Table 3 indicates the entire outdoor weathering program under evaluation. Entries in the table indicate the number of repetitive samples for the same charcoal that will be exposed for each time period listed, and entries in parentheses indicate that the exposures have not been completed.

Partial results are available for those samples that have completed their outdoor exposures in FY78. Values of the pH of water extract have been determined. but penetrations of methyl iodide are not yet available due to the procedural questions of equilibration for laboratory methyl iodide determinations as previously dis-cussed in Section II of this paper. These results covering the NRL progress in FY78, will be published by December 1978.

Table 4 presents the results available on the two carbons BC 727 and NACAR G-615 that have be n weathered for 6 months on the roof of the NRL Chemistry Building.

The results for 1, 2, and 3 months from Table 2 are included for completeness.

Using a lower pH value as indicating additional degradation, the monotonic decrease in expected carbon performance as e)posure time increases is illustrated for the 304'

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15th DOE NUCLEAR AIR CLEANIN2 CONFERENCE lU TABLE 3 00TD00R WEATHERING PROGRAM N

4f EXPOSURE PERIOD, MONTHS rl Exposure 1

2 3

6 9

J P

1 (4) 1 (1) i NACAR G-615 1

1 I

4 BC 727 (10) 2 1

1 (1) h (5) 0 1

(1)

(1) y SS 207 l

MSA 463563 2

0 1

1 (1)

I 2701 2

0 1

(1)

(1)

KITEG 1

0 1

(1)

(1) a i,

Entries indicate the number of independent exposure periods.

Parentheses indicate tests not completed.

v 4

first bed layer, but it appears that the pollutants are not reaching subsequent

.l layers of the bed to any great extent (pH of water extract values for unweathered These conclusions should carbons are 9.8 for NACAR G-615 and 9.5 for BC 727).

i be substantiated when 9-month exposure data are available and when the penetrations of methyl iodide for the exposed carbons are available.

4 Table 4 also includes the available data for the carbon MSA 463563. The indicated degradations for 3 and 6 months are values obtained during FY78; 1 month values are included for completeness from Reference 1.

The expected increase of degrada-tion with increased weathering time is observed, and it also appears that the pollutants are reaching the second layer to a significant degree after 6 months e

463563 is 8.5).

Results exposure (initial pH of water extract for unexposed MSA g

for 9 month exposures and for all penetrations of methyl. iodide will be published f:

i by December 1978, Three month outdoor exposures have also been completed for Sutcliffe Speakman e

2078 plus 5% TEDA (coal based, with an initial pH of water extract of 8.8), and These rnults are presented in Table 5, including the KITEG (initial pH of 8.2).

3-month data for NACAR G-615 and BC 727, to illustrate the effect of the carbon base, the impregnant, and the effect of the type of exposure (winter versus summer, wet versus dry period).

i The meteorological conditions and pollutants, and the additional penetration of The results presented for methyl iodide data will be published when available.

463563 and 2701 are for the same exposure period, and for carbons carbons MSA Sutcliffe Speakman and KITEG are for the same exposure period.

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15th DOE NUCLEAR AIR CLEANING CONFERENCE f

s?

TABLE 4 GRADIENTS IN THE PENETRATIONS (P) 0F METHYL IODIDE AND THE pH OF WATER EXTRACTS AFTER 3

1, 2, AND 3 MONTHS EXPOSURE 3

First Layer Second Layer Third Layer Fourth Layer f

Exposure pH P

pH P

pH P

pH F

^

NACAR G-615 i,

(

5016 1 month 9.3 1.77 9.5 0.64 9.6 0.34 9.7 0.7C 5031 2 8.2 3.42 9.8 1.32 10.0 0.86 10.0 1.02 3

5022 3 7.5 8.62 9.8 1.38 10.0 1.19 10.0 0.81 l

5056 6 3.8 9.4 9.6 9.6 i

q BC 727 5014 1 month 8.8 2.67 9.3 1.20 9.3 0.68 9.3 1.31 5032 2 7.3 5.81 9.3 2.58 9.5 3.09 9.5 3.45 5020 3 7.0 21.6 9.4 5.4 9.5 5.0 9.5 5.7 5056 6 3.1 S.9 9.1 9.0 MSA 463563 5015 1 month 7.45 4.0 7.65 1.9 7.65 3.6 7.8 2.1 5021 1

6.7 15.5 8.2 8.0 8.2 8.8 8.2 8.4 5060 3 3.4 7.5 7.7 7.8 i-5059 6 2.5 6.9 7.8 a_n if 306

15th DOE NUCLEAR AIR CLEANING CLNFERENCE TABLE 5

_[

0b GRADIENTS IN THE PENETRATION (P) CF METHYL I0DIDE AND THE pH OF WATER EXTRACTS AFTER 3 MONTHS EXPOSURE

.'lt i

i ii f

First Layer Second Layer Third Layer Fourth Layer

[

Exposure pH P

pH P

pH P

pH P

L 8

5022 NACAR 7.5 8.62 9.8 1.38 10.0 1.14 10.0 0.81 G 615 5020 BC 727 7.0

?l.6 9.4 5.4 9.5 5.0 9.5 5.7 5060 MSA 463563 3.4 7.5 7.7 7.8 r

5063 SS 4.5 8.7 8.9 8.9 5061 2701 3.6 8.2

'8.5 8.6 5069 KITEG 2.8 7.2 7.3 7.4 p

The final results available for FY78 are additional one-month and two-month ex-posures for BC 727. Table 6 presents the pH of water extract values, and compara-tive values for FY77 exposures are included. From the two-month exposures, it appears that two winter months degrade the carbnn to a greater degree than two summer months. An identical type of profile for the two month (February - March 1978) period is observed as was reported in Reference 1.

That is, the first layer appears to act as a guard bed to remove the bulk of the contaminants, then any migration of impregnant complex will lead to a decrease in penetration for the subsequent layer, except for the fourth layer for which the penetration could increase due to the net loss of impregnant in the expelled air.

B.

Laboratory Exposures l

There are now two independent installations available to conduct the laboratory l

weathering experiments, allowing a greater accumulation of data in less time.

l Laboratory exposures that have been completed in FY78 have used water vapor as the single pollutant, and all exposures have been for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. Charcoals MSA 463563, l

AAF 2701, KITEG, and Sutcliffe Speakman have been exposed to air with both 50% and 90% RH. Table 7 lists the results available for the 90% RH exposures, including BC 727 and NACAR G-615 results as published in Reference 1, and Table 8 lists identical information for the 50% RH exposures. The penetration of methyl iodide values listed for MSA 463563 and NACAR G-617 carbons were evaluated according to Method B as discussed in Section II of this paper, i.e., use of one-fourth of each layer of the weathered sample to construct a test bed preserving the same entrance-to-exit sequence, and performing one methyl iodide penetration test on the 2-inch deep bed. Future tests for penetrations of methyl iodide to complete Tables 3n7

'15th DOE NUCLEAR AIR CLEANING CONFERENCE TABLE 6 CHARC0AL BC 727 EXPOSURES

\\

First Layer Second Layer Third Layer Fourth Layer Exposures pH P

pH P

pH P

pH P

/t +

5014 June 77 8.8 2.67 9.3

'l.20 9.3 0.68 9.3 1.31 5070 April 78 8.3 9.2 9.2 9.2 5032 Au9-Sept 77 7.3 5.81 9.3 2.58 9.5 3.09 9.5 3.45 1

/ :

5065 Feb-Mar 78 7.3 13.4 9.3 5.4 9.2 5.1 9.4 6.0 I

TABLE 7 LABORATORY EXPOSURES AT 90% RH i

First Layer Second Layer Third Layer Fourth Layer Exposures pH P(%)

pH P(%)

pH P(%)

pH P(%)

i 5036 BC 727 8.2 12.7 9.1 5.1 9.1 7.3 9.2 3.4 5037 NACAR 9.5 2.0 9.5 9.4 8.8 2.1 G-615 5072 SS 8.6 8.7 8.7 8.7 i

5074 NACAR G-617 P*=9.2%

, 9.6 9.6 9.6 9.6 l

5076 KITEG 7.8 7.7 7.7 7.7 1

5086 8.3 8.3 8.3 8.2 c,

MSA 463563

(

• = Penetration for a two-inch bed.

\\

]

i i

308 i=

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T 15th DOE NUCLEAR AIR CLEANING CONFERENCE t

h TABLE 8 LABORATORY EXPOSURES AT 50% RH i

First Layer Second Layer Third Layer Fourth Layer i

Exposures pH pH pH pH i

i I

5053 BC 727 9.5 9.5

.9.5 9.6 5054 NACAR G-615 9.9 9.9 9.9 9.9 5071 2701 9.0 9.0 9.1 9.1 5073 MSA 463563 0.2 8.3 8.3 8.3 i

P* = 4.7%

5075 KITEG 8.4 8.4 8.4 8.4 I5085 SS 8.4 8.4 8.4 8.4 I

• = Penetration for a two-inch bed.

I 7 and 8 will also be performed according to Method B.

From the pH of water extract i

I values listed there does not appear to be sufficient variation to draw any me.n-ingful conclusions.

I IV. FUTURE WORK i

Plans for future experimentation include outdoor exposures at NRL, laboratory f

exposures, examination of spent charcoals of known weathering history, and outdoor exposures at locations other than NRL.

A.

Exposures to Outdoor Air Table 3 indicates the charcoal samples that will be weathered in outdoor air at 4

At the end of the program, all charcoals listed will have been weathered for A number of charcoals will have been weathered for NRL.

1, 3, 6 and 9 month periods.

the same time periods, and one carbon (BC 727) will be weathered for nine 1-month t

Selected exposed samples will be periods to observe any seasonal variations. tested for methyl iodide penet mixing to obtain the profile), but most samples will be tested for methyl iodide penetration according to Method B, (use one-fourth of each layer of the weathered sample to construct a test bed preserving the same entrance-to-exit sequence and determine only one methyl iodide penetration). Samples will also be tested for methyl iodide penetration according to Method C (test without disturbing the weathered sample), once fabrication of appropriate canisters is complete.

309

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~T 15th DOE NUCLEAR AIR CLEANING CONFERENCE n

Two carbons (BC 727 and Sutcliffe Speakman) will also be evaluated to determine h

any influence of " resting" a sample.

For these tests, samples will be exposed for

{

one conth, held dormant (no weathering-inactive) for one month, then exposing for y

one additional month, and then analyzed for pH of water extract and penetratlon 4

of methyl iodide values.

The sequence expose-inactive-expose-inactive-expose-test (resulting in a total of

]

three months weathering) will also be examined.

i B.

Laboratory Exposures Laboratory exposures are to be completed using water vapor as the single pollutant for the carbons MSA 463563, Sutcliffe Speakman, 2701, KITEG and NACAR G-617 at 70%

RH, for 2701 at 90% RH, and for NACAR G-617 at 50% RH. This will result in all the carbons under study being evaluated at 50, 70 and 90% RH for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> exposures.

An atmospheric pollutant will be added to the water vapor plus air mixture. First, hexane (2.5 to 5 ppm) will be added to 50, 70 and 90% RH air and used as the insult gas for BC 727 and NACAR G-615 carbons. Hexane will also be added to 70% RH air and used as the insult gas for MSA 463563, Sutcliffe Speakman, 2701, KITEG and NACAR G-617 carbons.

Hexane is chosen to represent the total hydrocarbon 4

(including methane) pollutant in the environment. Second, methyl isobutyl ketone will be added to 70% RH air and used as the insult gas for BC 727 and NACAR G-615 carbons. Methyl isobutyl ketone is chosen to represent a paint solsent pollutant.

Third, ozone levels of 0.1 ppm will be achieved and added to 90% RH air for use as the insult gas for BC 727 and NACAR G-615 carbon. All of the above exposures will be for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

Laboratory work will include cycling water vapor levels.

For BC-727 and NACAR G-615 carbons, 50% RH air will be used as the insult gas for 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> followed by 90% RH air for 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />, and then evaluated (after the total exposure of 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />). The reverse order of RH values will then be examined; i.e., 90% RH air for 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> followed by 50% RH air for 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />.

Finally, selected synergistic combinations of pollutants (water vapor plus sulfur dioxide plus hydrocarbon, water vapor plus ozone plus hydrocarbon) will be used as the insult gas.

For all the above analysis of laboratory-exposed carbons, selected samples will be evaluated for penetrations of methyl iodide according to Method A (evaluate each one-half inch layer indep'endently), but the majority will be evaluated for pene-tration of methyl iodide using Method B (use one-fourth of each layer of the weathered sample to construct a test bed preserving the same entrance-to-exit sequence and performing one penetration test on the 2-inch deep bed). The pH of water extracts and weight gains will be evaluated for all carbons exposed as a function of bed layer.

C.

Outdoor Exposures at Locations Other Than NRL Due to variation of contaminants in the atmosphere in both time and location, it is desirable to expose the carbons to outdoor air at locations other than NRL. Gen-eral weather considerations will aid in the selection of suitable sites (the dry southwest, the humid southeast, industrial versus non-industrial areas), and data on the contaminants must also be available.

Sites in close proximity to nuclear 310 4

.6

15th DOE NUCLEAR AIR CLEANING CONFERENCE s

power stations will be chosen. The exposed charcoals will be changed periodically and returned to the laboratory for examination of penetrations of methyl iodide, i

pH of water extract and weight gains.

It is also planned to attempt to regenerate the spent carbon to recover methyl iodide trapping efficiency, and to analyze the carbon for the pollutants that have accumulated on the carbon (analysis of vola-tiles on programmed heating), and to determine the ignition temperature.

D.

Examination of Charcoals in Different Stages of Service Charcoals that have been in service at nuclear installations will be procured and will be analyzed similiarly to those carbons exposed at outdoor locations other than NRL. This information, with an indication of what service the carbon has experienced, will aid in correlating laboratory versus outdoor exposure data in order to predict the useful life of carbons.

V.

Conclusions Recognizing the need to determine the effect of atmospheric contaminants on the useful life of activated charcoal, the U.S. Nuclear Regulatory Commi.ssion contrac-ted with the Naval Research Laboratory (Surface Chemistry Branch) to detennine the extent to which such contaminants degrade commercially - available charcoals.

The work is in the second year; results for FY77 have been published in NUREG/CR-0026, " Effects of Weathering on Impregnated Charcoal Performance", March 1978.

This paper has briefly summarized the FY77 results, and also highlighted two problems with the evaluation of exposed carbons; the configuration to be employed for the laboratory determinations of the penetration of methyl iodide, and the equilibrium procedure used for such laboratory analysis. The pollutants water vapor, ozone and sulfur dioxide have been seen to seriously degrade the carbons, whereas carbon monoxide did not.

It has also been shown that the longer the ex-posure, the more the carbon degrades, but this effect has not proved to be mono-tonic with bed depth.

The laboratory and outdoor exposure work in progress has been sunmarized, which extends the time of exposure and the number and type of carbons to be tested.

Future work will include different combinations of three (and more) pollutants as the insult gas, outdoor exposures at various U.S. loca-tions, and examination of spent charcoal from nuclear power installations.

REFERENCES 1.

U.S. Nuclear Regulatory Commission NUREG/CR-0025, " Effects of Weathcring on Impregnated Charcoal Performance," V. R. Deitz (Naval Research Laboratary),

March 1978.

2.

American Society for Testing and Materials, " Standard Method for Radiciodine l

Testing of Nuclear Grade Gas-Phase Adsorbents," Draft Version, October 14, 1977 3.

Letter to H. Brockelsby, Reactor and Technology Support Division, Oak Ridge Operations Office, DOE from V. R. Deitz and J. B. Romans, Naval Research Laboratory, " Activities for March 1978, Project KZ, 03 04 03," 6170-211, May 1, 1978.

4.

A. G. Evans, "Effect of Service Aging on Iodine Retention of Activated Char-coals," Proceedings of the Fourteenth ERDA Air Cleaning Conference, Sun Valley, Idaho, 2-4 August, 1976, USD0E Report CONF-760822, pp. 251-263.

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15th DOE NUCLEAR AIR CLEANING CONFERENCE

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1 DISCUSSION w

EVANS:

L'hy does charcoal weather faster in the winter?

BELLAMY:

Additional data will be gathered during future work, but it appears that the combination of low temperature and moisture weathers the carbon to a great-i er degree than high temperature and moisture.

r 4

It appears that an i_n situ radiciodine test might be carried out

~

DEMPSEY:

n through the charcoal samples now that you have accurate proportional flow data,

[

i.e., a sufficiently small amount of radioiodine might be used to permit licensing.

Do you think this would be possible?

BELLAMY:

The present state of mind of the public with regard to the release of radioactivity to the atmosphere is such that these tests are impractical unless a

there is a very strong overriding technical reason for vaing a radioactive in-place test in preference to the standard in-place leak test with Freon and the correspond-ing laboratory radiotest for the carbon.

l 312

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