ML19246B027

Effects of Weathering on Charcoal Performance, Naval Research Lab Memo Rept 4006

ML19246B027
Person / Time
Site:	Crane
Issue date:	05/10/1979
From:	Deitz V NAVY, DEPT. OF, NAVAL RESEARCH LAB.
To:	NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
References
CON-FIN-B-6003, TASK-TF, TASK-TMR NUREG-CR-0771, NUREG-CR-771, RQ, NUDOCS 7907100672
Download: ML19246B027 (79)

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NRL Memorandum Report 4006 NUREGICR-0771 RO Effects of Weathering on impregnated Charcoal Performance Vicron R. DaTz Surface Chemistry Branch Chemistry Division May 10,1979 Prepared for Division of Safeguards, Fuel Cycle and Environmental Research Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Under Interagency Agreement No. AT(49-24)-9006 NRC FIN No. B-6003 Sh k ws NAVAL RESEARCII LABORATORY Washington, D.C.

493 12 Approsed for public relcaw; dhtribution an!!mited.

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i NOTICE i

This report was prepared as an account of work sponsored by the United States Government. Neither the United Stz.tes nor the United States Nuclear Regulatory Commission, nor any of their employees, nor any of their contractors, subcontr actors, 3

or their employees, makes. any warranty, express or bplied, y

l nor assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, g

apparatus, product or' process disclosed, nor represents th.?t its use would not infringe privately owned rights.

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20. Abstract (Contimaed) methyl iodide.131 penetration. The influence of moisture in laboratory air flows of 50,70, end 90"o Ril has been st 2 died in detail for the eight charcoals. 'Ihe exposures of the charcoals to outdoor air have now been extended to nine months and the results show a progrer,sive decrease in iodine trapping efficiency. There is evidence from both the laboratory and outdoor exposure tests that moisture can enhance charcoal degradation. An adverse synergistic influence of moisture and liydrocarbon vapors has also been observed. All samples were layered to permit a determination of the profile in properties along the line of flow. The entrance layer, first of four equal layers, was found to be the most significantly affected by the exposure insult. It is believed that local meteorological conditions of high humidity combined with atmospheric pollutants in the test vicinity contribute jointly to the degradation of impregnated activated carbons.

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Contents Pagg Contents iii Acknowledgement v

Abstract vi List of Tables vn List of Figures viii I

Introduction 1

II Problems in Testing Charcoal 8

1.

The Weathering and the Tecting Procedures 8

2.

Temperature Excursions During Testing 10 3.

Testing With and Without Prehumidification 14 III Laboratory Weathering 17 1.

Air Flows at Three Levels Relative Humidity 17 2.

Exposures to Two Sequential Air Flows of Different Relative Humidity 22 3.

Hydrocarbon-Air-Water Vapor Mixtures 26 IV Weathering of Charcoals in Unmodified Outdoor Air at NRL 30 1.

Scheduling of the Exposures 30 2.

Depth Profile of Properties in Weathered Charcoals 33 3.

Results for the Penetration of Methyl Iodide-131 38 4.

Behavior in Intermittent Air Flows 46 V

Concludio; R^ marks 50 1.

Moisture Influence on Charcoal Efficiency 50 2.

Moisture and Contaminant Influence on Charcoal Efficiency 50 3.

Future Plans for FY79 54 VI References 58 VII Appendices 1.

Physical Properties of the Charcoals Under 60 Investigation 2.

Average Monthly Dew Points (*F) for 1970-1978 at the Washington National Airport (7) 61 3.

Monthly Average Concentrations (ppm v/v) of Pollutants during 1477 at NRL 62 493 19b iii

CONTENTS (Cont'd)

Page 4.

Radiciodine/ methyl Iodide Standard Test Conditions Proposed by ASTM D28.04. 1978 63 5.

Temperatures Observed betwece Sample at.d Back-up Beds during the Methyl Iodide-131 Penetration Test No.

5088, previously Weathered at 90% R.3.

65 6.

Dependence of Weight increases and pH oi the Water Extract af ter 100 hr exposttre in an Air Flow of 100 L/ min at cesignated Relative Humidity 66 7.

AST7f Specifications for Nuclear Gra 'e Charcoals (Draft 2, 7 August 1978), D28.04 67 8.

Relative Humidity (%) and Dew Points ('F) During the 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Before Charcoal Sampling 68 9.

Average 1:'nthly Dew Points F for 1972-1978 at the Chicago O' Hare Airport (7) 69 49B iV

Acknowledgements The technical guidance of J. T. Collins and his Staff and the overall program guidance of C. B. Bartlett and D. Solberg of the U.S.

Nuclear Regulatory Commission are very much appreciated.

The important contribution to the laboratory work by J. B. Romans of the Surface Chemistry Branch, Naval Research Laboratory, is gratefully acknowledged.

A. Stamulis of the Radiological and Environmental Protection Branch has been most helpful in advising on contaminant evaluation and the Branch has generously permitted the use of unpublished results.

Thanks are due to the several manufacturers and suppliers who kindly provided the samples of commercial charcoals.

V

Abstract The useful life of activated carbon filters in engineered-safety-feature and normal ventilation systems of nuclear power stations is slowly impaired by the conts.minants accumulated from the large volume of air being processed.

The weathering of eight commercial impregnated activated carbons have now been studied by a two-fold approach:

(1)

Exposure to unmodified outdoor air for periods up to nine months, followed by measurements of methyl iodide-131 penetration, and (2) exposure of the same type charcoals to air flows of known pollutant species and concentrations under controlled laboratory conditions, also followed by measurements of the methyl iodide-131 penetration.

The influence of moisture in laboratory air flows of 50, 70, and 90% RH has been studied in detail for the eight charcoals.

The exposures of the charcoals to outdoor air have now been extended to nine months and the results show a progressive decrease in iodine trapping efficiency.

There is evidence from both the laboratory and outdoor exposure tests that moisture can enhance charcoal degradation.

An adverse synergistic influence of moisture and hydrocarbon vapors has also been observed.

All samples were layered to permit a determination of the profile in properties along the line of flow.

The entrance layer, first of four equal layers, was found to be most significantly affected by the exposure insult.

It is believed that local meteorological conditions of high humidity combined with atmospheric pollutants in the test vicinity contribute jointly to the degradation of impregnated activated carbons.

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Tables Page 1

Impregnated Commercial Charcoals Under Investigation 3

2 Methyl Iodide Penetration of Weathered Activated Carbons and those Removed from Service when Tested With and Without Prehumidification at 95% RH and 30*C 15 3

Exposure Schedule with Air-Watcr Vapor of Constant Relative llumidity for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> 19 4

Results for Charcoals Exposed for 100 Rours at Constant Relative Humidity and an Air Flow of 100 Liters per minute 21 3

Exposure Schedule of Charcoals with Air-Water Vapor at Two Levels of Relative Humidity, each for 50 Hours 22 6

Results af ter Exposure at Two Levels of Relative Humidity, each for 50 Ho.rs 26 7

Influence of Prehumidification on the Trapping Efficiency af ter Hydrocarbon Contamination 29 8

Weathering Schedules for the Charcoals Exposed to Unmodified Outdoor Air at NRL 31 9

Profile Along Line of Flow in the Weathering of Charcoals in Unmodified Outdoor Air at NRL - pH and Weight Increases 35 10 Correlation of the Weight Increases with the Relative Humidity and the Dew Point Existing Before Terminating the Exposure 37 11 Calculation of the Penetration in Mode 2 Configuration from the Results in Mode 1 Configuration 39 12 Comparisons of the Penetrations of Methyl Iodide-131 for the Same Charcoals Weathered in Both Mode 1 and Mode 2 40 Configuration 13 Methyl Iodide-131 Penetration through Charcoals after Weattering in Unmodified Outdoor Air 41 14 The Penetration of Methyl Iodide through NACAR 615 and Duration of Exposure 43 15 The One-Month Performance of NACAR 617 in June and July 1977 44 16 One-Month Exposures of BC 727 46 17 Schedule for Intermittent Weathering in Exposures to Unmodified Outdoor Air at NRL 47 18 Intermittent Exposures with BC 727 48 19 Intermittent Exposures with NACAR G 615 48 200 4 9 3

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Figures Page 1

Adsorption of Oxygen by a Charcoal at the Indicated Moisture Content, Dry Basis 5

2 Temperature Excursions in Testing Non-Humidifed Weathered Charcoals at 30*C 11 3

Temperature Excursions in Testing Non-Humidified Weathered Charcoals at 130 C 12 4

Dynamic Adsorption and Desorption of Water by Coconut Activated Carbon (NACAR C 210) at 25 C (kindly furnished by Frank R.

Schwartz, Jr., North American Carbon, Inc.)

16 5

Temperature Record of Optical Dew Point and Air Flow in Laboratory Weathering 18 6

Methyl Iodide-131 Penetration for Charcoals Weathered at Con-stant Relative Humidity (21-23*C) for 100 Hours at 100 L/ min 20 7

Exposures to Two Sequential Air Flows of Different Relative Humidity 24 8

Penetration on Exposure to Sequential Changes in Relative Humidity 25 9

Penetration of Methyl Iodide-131 through BC 727 After One-Month Exposure to Outdoor Air (Table 13) 45 10 Weight-Gains (%) of the Four Sequential layers Exposed 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> at 50% RH 51 11 General Dependence of Fractional Penetration over the Complete Range of Breakthrough Concentration 53 e

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I.

Introduction The use of activated and impregnated charcoals by the nuclear industry for periods of two to three years without regeneration is an adsorbent application with new and undefined maintenance problems.

Tbese relate to the ef fect of environmental contaminants on the useful life of the charcoal.

During the period in service the charcoal must be ready to serve its role in the retention of radiciodine should an incident occur, or in the continuous removal of low concentration levels of radioactive lodine. The immediate objective of this investigation is to determine the extent to which atmospheric contaminants degrade the efficiency of impregnated activated carbons for trapping methyl iodide, an organic species found in nuclear power plant operations.

In the first reports (1,2) from NRL the many complex factors in-volved in weathering of charcoal were discussed.

Results of initial tests were then reviewed wherein the trapping efficiency for methyl lodide-131 was determined for a few charcoals af ter exposure to ozone, sulphur dioxide, carbon monoxide and water vapor. The present report describes tests, carried out on a greater variety of charcoals, which utilized water vapor and/or hydrocarbons as the principle weathering agents.

The results to be described illustrate the propertiec of certain base charcoals with particular impregnations and should not be interpreted as an endorsement or reccamendation of any particular manufacturer's product.

The impregnated activated carbons installed in engineered-safety-features and in normal ventilation systems of nuclear power plants are subject to a continuous interaction with ambient and local contaminants found in air.

The ambient contaminants include volatile hydrocarbons, ozone, sulfur dioxide, nitric oxides and carbon monoxide which are widely distributed in the environment.

Local contaminants are materials drawn into air ducts leading to the charcoa! filters as a result of solvent spills, evaporation of lubricating agents, and volatilization Nos: Manuscript submitted April 10,1979.

498 20L

of paint components. The prolonged exposure of charcoals to these contaminants has a degrading influence on the trapping efficiency for methyl iodide-131. Methyl iodile is generally considered as representa-tive of the organic iodides present in nuclear power operations and these compounds may be generated by a series of chemical reactions between elementc1 iodine, a fission product, and the organic compounds present in the containment space.

The adsorption sites of a charcoal can be occupied by atmospheric contaminants and thes prevent a reaction with methyl iodide.

Also, the specific chemical sites in the interface between the base charcoal and the impregnants, where chemical reactions with methyl iodide molecules take place, can be physically damaged or destroyed. Both categories of enange occur in " weathering" of charcoals by exposure to contaminants, and there has not been hitherto (as of January 1977) an in-depth engineering analysis of the problem.

The commercial impregnated charcoals used in this study (Table 1) include both coconut and coal as source materials f or the base char-coals. The impregnations include a mixture of KI and elementary iodir.e, and a tertiary amine, either alone or with iodine salts. The first report (1) dealt mainly with BC 727 and G 615 and the present report extends the number to those shown in Table 1.

Add it io nal properties of the eight charcoals are given in Appendix 1.

A two-fold approach has been fol? owed in these sutides to obtain the necessary data.

First, charcoal samples wcre exposed to unmodified outdoor air for various periods of time, and then examined for changes in methyl iodide retention capability, weight changes, and pH of the water extract. This approach is representative of conditions which might exist in the charcoal service life, but allows no control over the concentration or type of atmospheric contaminant. Second, addi-tional samples of the same charcoals were exposed under controlled laboratory conditions in various known pollutant combinations.

In this way pollutant types, concentration and combinations can be varied under the discretion of the investigator.

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Table 1:

Impregnated Charcoals Under Investigation

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Charcoal Size Activity

• Source Impregnation BC 727 8 x 16 90 Coconut KI + I 2 BC 717 8 x 16 60 Coconut KI + 1 2 G 615 8 x 16 60 Coconut KI + TEDA G 617 8 x 16 95 Coconut KI + I 2 MSA (463563) 8 x 16 60 Coconut KI + 1 2 AAF 2701 8 x 16 60 Coconut KI + I 2 KITEC 8 x 16 60 Coal Iodine Salts and Tertiary Amines Sutcliffe, Speakman & Co 8 x 16 60 Coal 5% TEDA

• ASTM D3467; TEDA E triethylenediamine Since the initiation of this investigation (1), the ambient con-taminants encountered in the outdoor air at NRL have varied over the four seasons of the yea. The absolute humidity (dew point) was maximum in July and August and rainimum in January and February.

These trends are similar to previous years (see Appendix 2, 770-1978) and appear to be a general characteristic of the climatological location of which NRL is a part.

From the NRL Air Quality Data (3,4) for 1976, 1977 and 1978 the monthly average concentrations of five common pollutants (Appendix

3) may be seen to have uniform trends. The NO e ncentrations were 2

fairly uniform over the year; the S0 ws greater in the first and 2

fourth quarters than in the second and third; the total hydrocarbons including methane were uniform over the year.

The oxidants (mainly ozone) were higher in the second and third quarters. These are some of the facts that have to be considered in any attempt to correlate the weathering behavior of charcoals in outdoor air during long periods of 10]

exposure.

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Tests under controlled laboratory weathering conditions have been beneficial in identifying water vapor as a very important factor. The influence of moisture on the subsequent methyl iodide-131 penetratien was demonstrated in the previous report (1) by the action of the 16-hour prehumidification in the testing of new coconut-base charcoals.

In fact, the interfering behavior of water vapor led to the introduction of the triethylenediamine impregnation of charcoals developed by Collins, Taylor and Taylor (5).

Since a water vapor-air mixture can be characterized by relative humidity and the dew point, a question r.ay be raised as to which measurement is the more helpful parameter in understanding the water vapor-charcoal interaction of a long durat

.n.

It appears that both parameters are important. The physical adsorption of water vapor at a specified temperature is determined by the relative humidity whicl con-trols the mass transfet of the water vapor from a continuous air flow into the activated carbon. On the other hand, the actual partial pressure of water vapor is the measure of chemical reactivity in any kinetic rate process and thus determines the rate of chemical reaction of water vapor with the charcoal. Hence, dew point, a measure of abso-lute humidity, is of value in a consideration of the long-range weather-ing reactions. The methyl iodide-131 trapping efficiency of a charcoal af ter relatively short contact times (24 - 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />) with high humidity air (95% Ril) can be rec. overed by drying the charcoal in warm air of lower relative humidity, but prolonged exposures to high relative humidities may lead to a degradation that is non-reversible at ambient temperatures (unpublished results, NRL).

The above behaviors suggest strongly that both relative humidity and absolute humidity must be taken into account in the charcoal weatherir.g processes.

The slow oxidation of an activated carbon at ambient temperatures by the oxygen content of air is also a factor to be considered in weathering processes of long deration. Unfortunately, little work has been reported on this topic.

In 1956, some research was reported at 49B 201 4

NRL (6) in which laboratory-prepared activated carbons were exposed to oxygen and to oxygen-water vapor mixtures.

It was shown that a steady uptake of oxyt;en occurred at 24 C and that this adsorption was enhanced in the presence of moisture. The results in Figure 1 indicate that the increase in oxygen adsorption was approximately proportional to the moisture content of the activated carbon.

In view of the constant pro-portion of oxygen in air, this parameter will not be varied in the weathering experimentation. Iloweve r, it remains to be considered as an additional chemical reactant, along with the pollutants, in the mechanism of weathering.

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It may be helpful to repeat the several questions raised at the beginning of this investigation (1) and to review these based on the data obtained sin e then.

The following queries were submitted:

(1) How can a judgment be made on when the charcoal must be replaced?

(2) What precursor behavior and information can be used to anticipate the need for a replacement?

(3) How can the useful lifetime of the charcoal be incre.

J?

It appears that a judgment might be made based on the profile of contaminants along the normal flow direction through the charcoal bed.

The observations with all of the charcoals have demonstrated that the entrance layer of the charcoal behaves as a " guard" bed and af ter a few months exposure this layer permits several-fold greater penetration of methyl iodide than the remainder of the charcoal. However, the subse-quent layers are not as efficien. as an equivalent amount of the unex-posed charcoal.

It appears that a charcoal bed has a chromatographic behavior along the direction of the air flow and also displacement phenomena can occur in whi:h one contaminant may displace another which had been previously adsorbed.

In view of these facts, it may be feasible to judge when to replace the charcoal by measurements in the effluent air in real time on an on-line basis of these displaced contaminants.

Ultimately, of course, the charcoal must be evaluated by a methyl iodide penetration test and it is then necessary to preserve the actual profile present in the bed of weathered charcoal.

Minimizing the moisture influence by decreasing the air flow during high humidity periods and enhancing the flow during ury periods may extend the useful life of a carbon adsorber.

The engineering aspects of this practice would have restrictions local to every installation.

Intermittent exposure of charcoal to air flows of high 6

498 2.0 11

and low humidity has been studied as part of this project in order to establish the effects of such a method of operation on laboratory-scale f il te rs.

It has been mentioned above that superimposed on the normal weathering of charcoal by the pollutants of the air is the action of organic vapors derived from local solvent spills and/or the solvent vapors from large paint operations conducted within a facility.

These are special situations, but are very important to the ef ficient opera-tion of carbon filters.

Pertinent laboratory r,'--iments are now in progress to follev the methyl iodide trapp.

et lciency of charcoals after exposure to concentrations of organic vapors greater than ambient total hydrocarbons (Appendix 3).

It may be noted that considerable methane (1 to 2 ppm) is always present in outdoor air and in the presence of ozone, the products derived from a methane-ozone reaction may also contribute to the degradation of the activated carbon.

8 493 208 7

II.

Problems in Testing Weathered Charcoals.

1.

Weathering and Testing Procedures Uaiform procedures for the determination of iodine and methyl iodide penetrations for new impregnated activa *si carbons are being established for the nuclear industry by Subcommittee D-28.04 of the American Society of Testing Materials (ASTM) and a summary tabulation of these is given in Appendix 4.

The specified parameters of the tests are the bed dimensions, flow rates, temperatures, relatise humidities, pre-equilibration t imes, the methyl iodide-131 feed period (temperature, relative humidity, concentration and duration of feed), and the elution period (temperature, relative humidity, flow rate, and daration).

Three test modes, or configurations, containing the weathered charcoals have been used (1) in the determination of the methyl iodide-131 penetration:

Mode 1 - Measurement of the penetration through each of the four charcoal layers, exposed in beds 2-inch diameter and 2-inch depth.

Mode 2 - Measurements of the penetration using one-fourth of tl.e weathered charcoal from each layer, reconstructed in the same sequence of entrance-to-exit as in the exposed sample.

Mode 3 - Measurements of penetration after the charcoal was weathered in standard test beds and do not require the transfer of the charcoal after the exposures.

It is essential to keep in mind that the experimental weathering parameters are distinct from the charcoal testing procedures. The test bed (Appendix 4) is specified as 2 inches (5.08 cm) in diameter and 1

493 isesu 8

2 inches high and it is packed with a uniform sample of the charcoal.

In the present study the weathered samples have to be of sufficient quantity to make all of the desired determinations.

Therefore, the charcoals were exposed in large stainless steel containers in beds 4-inch diameter (10.16 cm) and 2-inch height (5.08 cm).

Each sample was introduced

'n four equal layers, each 0.5 inch deep (1.27 cm) and separated by perforated stainless steel discs (see Figure 2, NUREG/CR-0025, page 8).

After exposure, the four layers were handled separately.

In thir. manner, the vertical profile in the weathering of the charcoal could be determined.

The use of the ASTM testing procedures, designed to qualify n^w material, raises uncertainties when they are applied to weathered samples.

The problem may be examined by noting the following general objectives and requirements of test proc 2dures for activated carbons used in nuclear applications (1) A means nust be provided to make a decision when the activated carbon must be replaced.

(2) The test must be demonstrated to be relevant to plant operation and simulate as close as practical accident conditions.

(3) The test must provide a capability to attain reproducible results between laboratories.

(4) The test results must not be negated by the action of specific contaninanto that accumulate during service.

In adapting the ASTM procedures to weatl.ered samples, it has been suggesmed that weathered charcoals not be subjected to the 16-hour prehumidification with 95% Hli air which is prescribed for new material.

It is thought that ti e e'imination of the prehumidif ication is a better 2.10 493

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simulation of accident conditions since a carocn filter must be ready at all cimes to serve its role as an engineered safety feature.

Several investigators do not recommend any pretreatment in order to prevent a partial regeneration of the carbon which would increase the measured trapping efficiency. Should the regeneration be appreciable, the test results would be invalidated Another suggested pretreatment is to store the sample as received in a static enclosure at 30 C over water for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, followed by a rapid transfer to the test container.

In the present study, the testing of weathered samples has not been made with the 16-hour prehumidification.

The procedures used wi]l be discussed in the next section.

2.

Temperature Excursions during Testing Charcoals weathered at NRL with outdoor air are exposed on a time basis and accordingly are removed under the meteorological condi-tions existing at that time.

The final days of an exposure may, there-fore, occur during a very wet or a very dry period.

A record of the dew points at NRI (7) over the past eight years, shown in Appendix 2, combined with tne changing daily temperature, establishes a variability in relative humidity that is beyond prediction. Charcoals from exposures completed during a period of dry weather have a small weight increase due chiefly to lack of adsorbed water. When these samples are exposed to the 95% RH air during the methyl iodide testing, a significant temperature rise occurred. The rise was recorded by inserting a thermo-couple in the air flow between the sample and back-up beds. The tempera-ture rise can be ascribed to the release of the heat of adsorption of water vapor on charcoal. Some typical examples are given in Figure 2 for a 30 C test and in Figure 3 for a 130 C test.

Because of the temperature gradients within the charcoal test sample, there is a corresponding change in the linear air flow velocity and in the calcu-lated contact time within the bed.

These are estimated to be approxi-mately 1 to 3% for a temperature change of 10 C.

The above observations are instructive for an understanding of the source of the temperature

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excursions within a test bed.

When the charcoal sample had been exposed to 90% RH air before testing, no temperaturc increase was observed as shown by the tabulated data for NRL Test 5083 given in Appendix 5.

Relative to other sources of uncerta;acies, for example, the charcoal sampling error, the influence of the temperature g adient in the bed may not be significant.

However, the temperature ccntrol specified by the ASTM test procedures need not be as precise for scathered sampics as that specified for new charcoals.

It also should be noted that the designated control conditions specified by the ASTM Test procedures (Appendix 4) apply only to the inlet air flow.

Using weathered charcoals completed during periods of low relative humidity (< 30% RH), it was possible to ameliorate the rise in temperature observed during methyl iodide testing by first placing the test sample in a stainless steel wire basket and keeping it overnight over water in static storage in a closed container.

The procedure was successful in substantially minimizing the temperature rise in tescing at 30 C; however, it is not known to what extent the procedure had in-fluenced the observed value for penetration. Moreover, its significance to plant-scale carbon bed operation is not known. The consensus men-tioned in a previous paragraph, namely to seek in a testing procedure the best simulation of accident conditions, would require that a pre-humidification technique not be used. Accordingly, after a number of tests to be described later, the above prehumidification technique in the wire basket was no longer used.

Milham and Jones (8) observed a partial reconeration of BC 416, a non-impregnated coconut charcoal, when the test bed was heated to 60 C for about 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> with pu-ified air at 7.5 f t/ min.

Af ter these condi-tions oome improvement was acted in the elementary iodine trapping efficiency.

It may be noted that an air flow of 95% RH at 30 C drops to 22% RH at 60*C which presents a dif ferent set of test parameters relative to that employed in the standard 30*C test procedure.

Tempera-tures well above 60 C are necessary to reach a level of regeneration 49'8

[

13

equivalent to new charcoal, as shown in 1947 in a detailed study of kilns (Herreshoff Kiln, a Rotary Kiln, and a Kiln with Stationary Retorts) for the regeneration of char (9).

3.

Testing Charcoals With and Without Prehumidification The accumulated experiences with weathered charcoals at NRL indicate that any prehumidification before testing at 90% RH and above contributes to a further lowering in trapping efficiency relative to that observed without prehumidification.

Thus, the use of a high rela-tive-humidity in the prehumidification of weathered charcoals can i in-fuse the results of the subsequent methyl iodide efficiency. Table 2 summarizes some penetration results for a number of charcoals weathered at NRL and also a few charcoals received after plant service.

These were determined with and without prehumidification (16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> in 95% RH air at 25 L/ min, see Appendix 4).

In all cases, the penetration is greater af ter prehumidification. When compared with the ASTM suggested performance requirements of new activated carbon (Appendix 7), six of the ten samples would not qualify when tested after preconditioning.

There are several possible changes that could occur in nuclear charcoals during the prolonged exposure at high b"midity air flows.

Chemically, there are hydrolytic reactions and hydra tin changes among the impregna-tion constituents. Physically, the base cru coal adsorbs water vapor in a strongly increasing amount with increase of relative humidity above about 40-50% (1). The behavior for a coconut activated carbon is shown in Figure 4.

A charcoal filter, exposed accidentally to the vapors from solvent spills or to organic vapors from plant operations, is subject to a synergistic interaction with water vapor. This behavior requires additional understanding before a judgment can be made as to charccal replacement. The above facts will be discussed in following sections.

14

Table 2: Methyl Iodide Penetration of Weathered Activated Carbon and those Pemoved from Service Testad with and without Prehumidifcation at 95% RH and 30*C Activated CH I-131 Penetration %

l Carbon Exposure Prthumidification Yes No 4

NRL 4289 on C202 4-29 Oct 76 6.74 0.73 NRL 4258 on MBV l-30 Nov 76 1.10 0.22 SS (KI on 207B) 2-29 Dec 76 18.7 14.6 G-618 10-31 Jan 77 0.62 0.05 NRL 4230 on MBV 1 Feb - 1 Mar 77 1.75 0.30 GX 176 2-31 Mar 77 0.89 0.45 BC 717 1 Apr - 2 May 77 3.79 0.67 GX 176 Paint Fumes,

. week 13.6 9.4 Used (Not Identified)

Removed from Plant 5.45 2.36 G 615 Removed from Plant 17.

d m

15

I i

i i

i i

l l

40

=

DESO RPTI ON' 30 u

H I

ADSORPTION c

k a

/

C 20

(

h f

x N

a 10 S

}

1 i

l i

l l

l l

l 20 40 60 80 100 RELATIVE HUMIDITY Figure 4: Dynamic Adsorption and Desorption of Water by Coconut Activated Carbon (NACAR G 210) at 25 C (Kindly furnished by Frank Schwartz, Jr.)

2.l~1 493 M

16

III. Laboratory Weathering 1.

Air Flows at Three Levels of Relative Humidity The controlled exposures of seven commercial charcoals to air flows at three levels of relative humidity (50, 70, 90% RH) have been completed. The air flow was continuous at a flow rate of 100 L/ min for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. The residence time was 0.25 see and the linear flow rate was 12.3 m/ min.

The total flow was thus 600 M and the total weight of water (calculated at 22*C) to which each charcoal was exposed, was 0.97, 1.74, and 2.61 kg at 50, 70, and 90% RH, respectively.

The exposures of the charcoals (Table 3) and the sequence of relative humidities were random in sequence. The temperature of the air conditioned laboratory was kept in the range 21 to 23 C.

The relative humidity in each of the two independent exposure systems was monitored by a devpoint hygrometer (General Eastern, Series 1211 P Sensor) and the air temperature was measured simultaneously with a platinum resistance thermometer (General Eastern, 1212 P).

The measurements illustrated in Figure 5 are con-tinuous recordings of dew points and air temperature as the air flow from the two systems was alternately passed through the instrument. The control, experimentally based on thermostated water supplies, was calcu-lated to realize an overall standard deviation of 1-8% RH over the 100-hour laboratory exposure.

The results for pH, weight increase, and methyl iodide-131 penetration are given in Table 4 for the above exposures. The pH re-mained aboat the same throughout the four layers of each charcoal (see detailed results given in Appendix 6). The weight increases (also given in Appendix 6) followed a behavior consistent with the water adsorption isotherm of the charcoal. The latter has the naracteristic cur m are of Figure 4 which accounts for the non-linearity of weight increas, with relative pressure (see also Figure 5 of NUREG.CR-OL25), the weight in-creases of all seven charcoals were greatest at the highest humidity.

The profilt of weight increase through the four layers of each charcoal 7

498 213

-40 m

$bk_ _

• Y._

.o

~

e t

-e R

v m.

~W--_---_

AtR Plov,*P s

s 58 60 62 64 66 Time (hours)

Figure 5:

Temperature Record of Dew Point and Air Flow in Laboratory Weathering 49B 18

can be obtained from the results given in Apps 'lix 6, since the dry weights (initially dried at 100"C) of charcoal introduced into each of the four layers were equal. The results at 50% RH showed a much greater gradient than the weight increases at 70 and 50% RH.

It may be noted that the weight increase at 90% RH was 30 wt.% or above for all char-coals under investigation (Table 4) and at 50% RH the weight increase was below 25% or less in all cases.

Table 3:

Exposure Schedule of Charcoals with Air-Water Vapor of Designated Constant Humidity for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> Constant Humidity Maintained During Entire Exposure Charcoal 50% RH 70% RH 90% RH BC 727 4-8 Oct 1977 1-5 Aug 1977 15-19 Aug 1977 5053*

5030*

5036*

C 615 11-15 Oct 1977 8-12 Aug 1977 22-26 Aug 1977 5054*

5035*

5037*

MSA 24-28 Apr 1978 5-9 Jun 1978 8-12 Fby 1978 5073*

5100*

5086*

S&S 8-12 May 1978 7-11 Jun 1978 18-22 Apr 1978 5085*

5101*

5072*

2701 18-22 Apr 1978 12-16 Jun 1978 15-19 May 1978 5071*

5102*

5038*

C 617 15-19 Fby 1978 12-16 Jun 1978 24-25 Apr 1978 5087*

5103*

5074*

KITEG l-5 Fby 1978 13-19 Jun 1978 1-5 May 1978 5075*

5104*

5076*

• Indicates the NRL Test Number The methyl iodide-131 penetrations (Table 4) increased for all seven charcoals with increase in the relative humidity of the air flow.

The increase from 50 to 70% RH was greater than the increase from 70 to 90% RH.

The differences among the different charcoals, seen in Figure 6, vary to some extent, but it is important to remember that these 498 210 9

I l

l l

l0 C

/

Ms A

270 IE no

~

G 617 G 615 1.0 p

,z x

Hwz 10

u. O.l

.01 50 70 90 RELATIVE HUMIDITY, %

Figure 6: Methyl Iodide-131 Penetration for Charcoals Weathered at Constant Relative llumidity (21-23*C) for 100 lirs at 100 L/ rain M

498 'd

measurements are based on a single production sample (25 pounds) of each type.

The behavior of the S6S, 5% TEDA, according to these measurements is outstanding for weathering in water vapor only. Mixtures of pollutants and water vapor will be discussed in another section.

Table 4:

Results for Charcoals Exposed at Constant llumidity for 100 llours at a Rate of 100 L/ min Relative Average of Methyl Iodide-131 Humidity pli Weight Increase Penetration Charcoal (av)

BC 727 50 9.5 25.8

1. 9 70 8.7 45.4 o.3 90 8.9 47.6 13.6 C 615 50 9.9 20.0 0.50 70 9.4 28.6 1.8

.04 90 9.3 29.9 2.0 MSA 50 8.3 21.4 4.66

.09 463563 70 8.1 36.1 8.6

.09 90 8.3 39.0 9.27

.06 S&S 50 8.4 15.4

<.01 (5% TEDA) 70 8.4 26.7

<.03 90 8.7 31.9

.04

.01 AAF 2701 50 0.1 18.9 0.24

.02 70 8.6 43.6 3.29 i.04 90 8.7 51.5 7.21

.05 C 617 50 9.4 20.3 1.10

.02 70 9.2 57.4 6.20 t.05 90 9.6 61.5 9.10

.13 FITEC 50 7.7 18.6 u.25

.03 70 7.7 29.1

.45

.03 90 7.7 40.0 A.37 i.27 The general behavior of the seven cha ;oals was found to be reproducible.

For example, two samples of BC 727 were exposed in August 1977 and in October 1978 and the results are given below:

493 221~

21

Test Exposure RH%

% Penetration 5030 1-5 Aug 1977 70 6.3 5131 16-20 Oct 1978 70 6.12 t.076%

5036 15-19,ug 1977 90 13.6 5132 16-20 Oct 1978 90 13.7

.127%

The good reproducibility obtained for BC 727 may be due in part to the close control possible in laboratory weathering and to the good repro-ducibility of the charcoal samples withdrawn from the master stock supply.

2.

Exposures to Two Sequential Air Flows of Different Relative Humidity Since the actual relative humidity of an air flow is never constant during an exposure to outside air, the question was raised as to how rapidly a charcoal filter responds to air flows of different relative humidity. The laboratory ec90sure-schedule detailed in Table 5 was carried out in which the 100-hour exposure was replaced by two 50-hour periods.

Each

'T two charcoals (G 615 and BC 727) was exposed in the following sequent f relative humidity:

50 + 90, 90 + 50, and 90 + dry air (dew point < 2 F).

Table 5:

Exposure Schedule of Charcoals with Air-Water Vapor at Two Levels of Relative Humidity (each 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />)

First Exposure Second Exposure NRL Test Charcoal Datt

%RH Date

%RH 5089 G 615 22-24 May 78 50 24-26 May 70 90 5090 C 615 22-24 May 78 90 24-26 May 78 50 5108 G 615 3-5 July 78 93 5-7 July 78 dry air 5106 BC 727 26-23 Jun 78 50 28-30 Jun 78 90 5107 BC 727 26-28 Jua 78 90 28-30 Jun 78 50 5109 BC 727 3-5 July 78 90 5-7 July 78 dry air 22 498 i)$92

The quantity of water retained by a charcoal at a given rela-tive humidity (see example in Figure 4) is greater on the desorption than on the adsorption branch of the isotherm. This hysteresis is reproducibic only under the steady state canditions reached in static

~

systems.

In flow systems pertinent to the present studies, the rates of adsorption and desorption that modify the weight-gain and weight-loss behavior depends on the duration of the exposure. Deitz and Blachly (16) showed that the largest weight-gains were obtained within the first 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and increased only slowly af ter 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. A study of the results (Tabic 6) indicate that the highest relative humidity of a two-stage exposure may be the controlling factor in the weight-gain observed.

These results are plotted in Figure 7 and an arrow indicates the direc-tion of the approach to steady-state values. The change from 90% RIl to 50% Ril or the change from 50% RII to 90% Ril yields approximately the same weight-gain of adsorbed water.

However, the change ftom 907. Ril to 0.8%

RIl does result in almost complete water r nnoval. This behavior demon-strates the need to use low humidity air to dry charcoals which have been exposed to au flows of high relative humidity.

The penetration of methyl iodide was also studied by Deitz and Blachly (16) as a function of the duration prehumidification (air at 25 L/ min and 95% RII) and the penetration va

')

increase with in-creased times of prehumidification.

It required.cout 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> before the penetration leveled off; the penetration doubled on extending the nrchumidification from 50 to 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. A cudy of the present results (Table 6) show a similar dependence on expocure time.

The penetration af ter the 100-hour contact times are given, Figure 8, for G 615 end BC 727.

It is evident that the two additional exposures for each char-coal that had received only 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> at 90% RH did not result in as much penetration. The F reased penetration with increased times of pre-humiditication u

.e t.nexpected when first observed in 1976 with experimental charconis, and it is important to ncte that the same effect is present for cormrcial charcoals.

b 493 ii$

u

l l

l50 hrs atl 50 RH t 90 RH

[*p 50 --

50 hrs at 90 RH 50 hrs at 50 RH 100 hrs at 90 RH 100 his at 70 RH 49 30 OC hrs at 50 RH 3m0 u

BC 727

<5 10 m

/

S 50 hrs at 90 y

50 hrs at RH I

I I

I I

q 40 50 hrs at 50 RH 50 hrs at 90 RH 4

g 50 hrs at 90 RH H

50 hrs at 50 RH 30 10 hrs at 90Rl[

100 hrs at 70 RH 20 <-

100 hrs at 50 RH G 615 10 50 hrs at 9

<1 50 hrs

.8 RH 2

1 I

I I

20 40 60 80 100 RELATIVE HDfIDITY, %

Figure 7:

Exposures to Two Sequential Air Flows of Different Relative Humidity 226 9b 24

I I

I I

i i

i I

l 20 100 hr ; at 90 RH 100 hrs at 70 (H

G 615 he, at 90 RH 10 w.rs at 50 RH 0

C 50 n.4

.t 90 RH 50 hr > at 50 RH 100 hrs at 50 Rif E

50 ' rs s,,l' 50 hr > at 90 RH ct0 C

E Wt i

I l

I I

f f

3 50 100 a?

a I

I l

l l

l l

l c

15 100 hrs at 90 RH fc Da d

5 r-10 4

BC 727 100 hrs 50 hrs at 90 RH at70Rlb 5

50 hrs at 50 Rli 50 hf'; a t 50 RH 50 hr 4 at 90 RH 30 hrs at 90 RH T

" 100 hrs at 50 RH i

i i

I I

I I

l 50 100 RELATIVE HUMIDIT"!

Figure 8: Penetration on Exposure to Sequential Changes in Relative Humidity 493 226 25

Table 6: Results af ter Exposure at Two Levels of Relative Humidity (Tota? Time 100 nours)

Total Exposure Wt Change Penetration Charcoal Time (hrs)

% RH pH G 615 50 50 50 90 9.5 38.8 0.66

.02%

G 615 50 90 50 50 9.4 34.8 0.69

.06 G 615 50 90 50 dry air 9.3 0.84 0.06

.01 G 615 100 90 9.3 29.9 2.00 C 615 100 50 9.9 20.0 0.50 r^

BC 727 50 50 90 9.2 50.1 5.88

.05 BC 727 50 90 50 50 9.0 46.9 3.95

.04 BC 727 50 90 50 dry air 8.9 0.78 1.02

.05 BC 727 100 90 8.9 47.6 13.6 BC 727 100 50 9.5 25.8 1.69 The above examples of the exposure of charcoals to two levels of relative humidity are only a small approximation to the great varia-bility encountered in practice.

The charcoal filter in service is sub-jected to relatively short periods of high and low relative humidity; periods of dry air will be favorable to high charcoal efficiency and periods of wet weather will steadily increase the moisture content of the charcoal. These preliminary results indicate that it could be advantageous to introduce a flow of air in dry weather to dehydrate ef fectively charcoal filters which otherwise may not be in operation at that time.

3.

Hydrocarbon-Air-Water Vapor Mixtures Of the contaminants studied, the normally occurring total hydrocarbon fraction (including methane) of the environment is second in g2.7 493 326 26

magnitude only to water vapor.

The adverse influence of extraneous organic materials on methyl iodide penetration was reported several years ago by Bennett and Strege (10). Assuming a concentration of 5 ppm hexane, for example, and a flow of 100 L/ min, the amount of hydrocarbon entering a 2-inch charcoal test filter in 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> is 10.3g.

Depending on the density of the charcoal, this quantity corresponds to a potential loading of 5 to 7 wt. percent of the charcoal.

In some preliminary experiments at NRL, a number of nuclear grade charcoals were first allowed to adsorb a known quantity and type of hydrocarbon and the penetrations of methyl iodide-131 were then determined.

In one series, the charcoals were then prehumidified (16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> exposure to air of 95% RH at a flow of 25 L/ min) and in the second series the same charcoals were not prehumidified.

The objective was to observe the magnitude of the synergistic influence of water vapor and hydrocarbon on the ef ficiency of the charcoal.

The results (Table 7) give the methyl iodide-131 trapping efficiencies of four charcoals with ar.d without prehumidification after the hydrocarbon contamination and these results may be compared with the behavior af ter exposure to water vapor alone. Without prehumidification, there is an increase in penetration relative to the original charcoal, but the efficiencies remain within the ASTM suggested acceptable performance requirements for nuclear crade charcoals (Appendix 7).

After the pre-humidification of the charcoals, the penetration was markedly increased.

All of the combinations of charcoals and pollutants in Table 7 were not studied since the results already demonstrated the synergistic influence of water vapor and hydrocarbon.

For example, the penetration for BC 727 was 4.8% for water vapor alone, 0.63% for 2% C H 1 ""'

14 30 and 9.5% for both water vapor and 2% C H Also, the penetration for 14 30 MSA 463563 was 2.5% for water vapor alone, 1.01% for 2% C H

y4 30 " "'

m ? 7.5% for both water vapor and 2% C H The weathering exposures 14 30 now in progress involve the insult mixture of organic vapor and 95% RH air going continuously to the charcoal and this is followed by the determination of methyl iodide-131 penetration.

The compounds selected include n-hexane, methanol, cyclohexanone and methyl isobutyl ketone.

??O

,MG,3 mma 27

The last two compounds are found in paint formulations.

Some pertinent data helpful in the preparation of the vapor mixture of the desired concentrations are given below:

Temp at MW d(g/cc) bp*C 10 torr ("C) n-hexane 86.17 0.659 68.7

-25.0 methanol 32.04 0.792 64.7

-16.2 cyclohexanone 98.14 0.947 155.7 methyl isobutyl ketone 100.16 0.804 j

117-119 In these exposures the air flow is 100 L/ min (residence time 0.25 sec) and the duration 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

Calibrated permeation tubes ac2 used as standards for n-hexane and methanol air mixtures and diff asion tubes are used for the higher boiling liquids.

The above organic vapors in air mixtures without water vapor were added to one of the charcoals to a 1cvel of 11 wt.%.

The results are:

Test Charcoal Contaminant CH I-131 Penetration 3

BC 727 None 0.014 5114 BC 727 Hexane 2.04

.04 5115 BC 727 Methanol 0.77

.05 5116 BC 727 Methyl Isobutyl Ketone 1.19

.10 The addition of 11 wt.% of these compounds did not degrcde the charcoal below the allowable performance requirements.

However, based on the results presented in Table 7, unacceptable methyl iodide penetration can be expected when a combined flow of water vapor a_d organic vapor is allowed to enter the charcoal. As detailed above, such experiments are now in progress.

22.9 498 is25EL 28

Table 7:

Influence of Prehumidification on Trapping Efficiency Af ter 11ydrocarbon Contamination

% Penetration Cll ~

3 BC BC MSA G

Charcoal

• Prehumidification 717 727 463563 615 Orig.

No

.05

.014 0.13 0.05 Orig.

Yes 1.0 4.8 2.5 0.27

+10%

No 0.37 Octane Yes 9.2

+10%

No 1.2 0.33 0.80 C H Yes 5.3 15.6 15.9 g 30

+2%

No 0.63 0.63 1.01 0.18 C il Yes 8.8 9.5 7.5 1.5 g 30

+0.2%

No 0.09 es 0.81 14"30

• Prehumidif ication:

16 hrs, 25 L/ min, 95% Ril.

230 493 39 29

IV.

Weathering of Charcoals in Unmodified Outdoor Air at NRL 1.

The Scheduling of the Exposures The study in outdoor air weath; ting has now been extended to include the same seven commercial charcoals used in the laboratory work.

When completed, all of these will have been exposed continuously for 1, 2, 3, 6, or 9 months. One of these charcoals (BC 727) will be weathered in each month of the year in a series of 1-month exposures to cover seasonal changes (for example, the dew point variations, Appendix 2).

The contaminants in air exist with a considerable variation in concen-tration (Appendix 3).

Moreover, a charcoal filter behaves as a chromatographic column and the different contaminants vary widely in the retention time in the filter.

Those contaminants that are irreversibly held by the charcoal can be expected to modify the chromatographic behavior in a progressive manner. The successful use of any impregnated charcoal by the nuclear industry (for two or ehree years without regen-eration) must somehow be dependent on the reversible adsorption of some of the contaminants and the non-reversibility of the iodine trapping.

The weathering schedule of the charcoals exposed to outdoor air at N'.tL (ctill in progress) is summarized in Table 8.

The volume of air in each case was deternined by the integrating gas meter placed directly downstream from the charcoal; there is a separate meter and a separate air pump for each sample of charcoal.

From the time (t) and the volume (V), the number of filter displacements, n, and the average residence

times, T,

can be estimated:

n=

and r =

where v is the volume of the charcoal container and Q is the average flow rate of the air, namely V/t. Table 8 contains the calculated values for n and T in addition to the exposure dates, V, and the corres-ponding times, t.

The large magnitude of n results from the huge volume 7,5 I

[g ;]

C 30

of air that is passed through a charcoal filter. A contaminant concen-tration of 1 ppm becomes a significant insult when integrated over the total flow.

Table 8: Weathering Schedule for the Charcoals Exposed to Unmodified Outdoor Air at NRL Period Time folume 6

n T

Test (Months)

(Hours)

(10 cu. ft.)

Exposure Date (10 )

(sec.)

NACAR 615 5016 1

667 0.1018 2-30 Jun 77 7.0

.34 5031 2

1506

.2209 29 Jul - 30 Sep 77 15.2

.36 5022 3

2178

.3302 1 Jul - 30 Sep 77 22.8

.34 5097 3

2151

.3077 3 Jun - 1 Sep 78 21.2

.36 5098 3

2151

.3130 3 Jun - 1 Sep 78 21.6

.36 5099 3

2151

.3124 3 Jun - 1 Sep 78 21.5

.36 5058 6

3982

.6288 16 Nov - 1 May 78 43.4

.33 5057 9

6552 1.0379 16 Nov - 16 Aug 78 71.6

.33 NACAR 617 5017 1

667 0.1044 2-30 Jun 77 7.2

.33 5023 1

668

.1017 1-29 Jul 77 7.0

.34 BC 727 5014 1

667 0.1100 2-30 Jun 77 7.6

.32 5070 1

599

.0919 7 Apr - 2 Fby 78 6.3

.34 5081 1

743

.1143 2 Fby - 2 Jul 78 7.9

.34 5082 1

745

.1076 2 thy - 2 Jul 78 7.4

.36 5083 1

745

.1110 2 May - 2 Jul 78 7.7

.35 5113 1

717

.1097 2 Aug - 1 Sep 78 7.6

.34 5121 1+

1009

.1623 1 Sep - 13 Oct 78 11.2

.32 5124 1

764

.1248 13 Oct - 14 Nov 78 8.6

.32 5032 2

1505

.2274 29 Jul - 30 Sep 77 15.7

.34 5065 2

1366

.2065 9 Feb - 7 Apr 78 14.2

.34 5096 2

1409

.2159 3 Jun - 1 Aug 78 14.9

.34 5020 3

2200

.3422 1 Jul - 30 Sep 78 23.6

.34 5056 6

3984

.6575 16 Nov 77 - 1 May 78 45.3

.32 5055 9

6552 1.0105 16 Nov 77 - 16 Aug 78 69.7

.34 h(!3 2YL 31

Tc' ale 8 (Continued) l Period Time folume 6

n T

Test (Months)

(Hours)

(10 cu. ft.)

Exposure Date (10 )

(sec.)

BC 717 5084 1

745

.1085 2 Fby - 2 Jun 78 7.5

.36 5013 1

667

.09930 2 Jun - 30 Jul 77 6.8

.35 5010 1

741

.08262 1 Apr - 2 May 77 10.1

.26 5024 1

668

.1057 1-29 Jul 77 7.3

.33 5019 1

668

.1001 1-29 Jul 77 6.9

.35 AAF 2701 5039 1

696 0.1071 1-30 Sep 77 7.4

.34 5040 1

696

.1131 1-30 Sep 77 7.8

.32 5061 3

1920

.3088 16 Nov - 4 Feb 78 21.3

.32 5118 6

incomplete 5120 9

incomplete KITEG (Nuclear Consulting Services, Inc.)

5042 1

644

.0954 3-30 Sep 77 6.6

.35 5069 3

1968

.2952 5 Feb - 2 bby 78 20.4

.35 5119 6

incomplete 5117 9

incomplete g

Sutcliff & Speakman (5% TEDA) 5033 1

786 0.1204 29 Jul - 30 Aug 77 8.3

.34 5034 1

786

.1259 29 Jul - 30 Aug 77 8.7

.33 5078 1

743

.1234 1 bby - 1 Jun 78 8.5

.31 5079 743

.1189 1 May - 1 Jun 78 8.2

.33 5090 1

726

.1138 2 May - 1 Jun 78 7.8

.33 50.3 1+

1077

.1746 2 Jun - 17 Jul 78 12.0

.32 5110 1

740

.1200 18 Jul - 18 Aug 77 8.3

.32 5063 3

1946

.3160 9 Feb 78 - 1 May 78 21.8

.32 5064 6

3623

.6736 9 Feb 78 - 10 Aug 78 46.5

.28 5066 9

6670 1.0104 9 Feb 78 - 14 Nov 78 69.7

.34 FEA (463563) 5015 1

667 0.1025 2 Jun - 30 Jun 77 7.1

.34 5021 1

568

.0912 1 Jul - 29 Jul 77 6.3

.38 5060 3

1920

.3263 16 Nov 77 - 4 Feb 78 22.5

.31 5059 6

3982

.6276 16 Nov 77 - 1 !by 78 43.3

.33 5077 9

incomplete 1b 498 M 3

2.

Depth Profile of Properties in Weathered Charcoals The pH of the water extract of charcoal from the entrance layer was always lower than the remaining charcoal and was also lower than the unexposed material. Table 9, in which the tests are arranged in the same sequence as in Table 8, shows that the pH of the entrance layers generally accreases with exposura time (months) and these values are listed below:

Month 615 727 2701 S&S MSA KITEG 1

9.3 8.5 7.6 8.1 7.5 6.7 2

8.2 7.5 3

7.8 7.0 3.6 4.5 3.4 2.8 6

3.8 3.1 2.4 4.0 2.5 2.4 9

4.1 3.3 3.2 2.7 The pH values of the remaining three layers of charcoal in the test beds did not differ significantly from each other until about

• & 2 ninth month of weathering at which time some penetration of the pH-lowering contami-nants was detectable.

The observed weight-increases varied considerably with the dew point of the outdoor air supply. The majority of the 48 weathering tests (Table 9) showed a two-digit weight increase, but 11 of these were definitely smaller, having average increases of only 2.5 to 6.0 wt.%.

The exceptions grouped in Table 10, include weathered charcoals sampled at four different times in 1978; five completed exposures on 1 lby and 2 May, three eu 1 June, two on 4 February, and one on 10 August. Using the published observations given every 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> (7) of the relative humidity and de-points in the immediate vicinity of NRL, the averages were obtained f, c the immediate 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> before termination and also for the period 24 to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> before termination (see also data given in Appendix 8).

The results (Table 10) indicate no correlation among the various kinds of charcoal (one exception) and no correlation with the duration of weathering. However, five charcoals (BC 727, KITEG, G 615, MSA, and 2701) have in common the fact that the relative humidity was gQ 33 493 42st3

below 50% and the dew points were 24 F and less.

Thus, the small in-crease in weight correlates with the known small adsorption of water vapor for these five charcoals under these conditions. The retaining four charcoals in this set of exposures were manufactured '

Sutcliffe and Speakman and constitute an anomaly.

The results on SSS (5% TEDA) (Table 10) could indicate that the expected gain in weight due to water adsorption might be offset by some loss in weight, possibly the impregnant.

The impregnation of this char-coal is nominally 5 wt.% TEDA (triethylenediamine).

Some volatilization might have taken place in detectable amounts during the lono exposure times, since the vapor pressure of TEDA is about 0.2 torr st 25*C.

How-ever, even in the unlikely loss of all TEDA, the weight 3ain on weathering would have been decreased by only 5 wt.% bc:ow the nominal increase due to water vaper adsorption.

The average dew points during the final days of the exposure (1 Fay - 1 June 1978) were not exceptionally low and consequently, it is not known wha' could have prevented the expected weight increases of the S&S samples. As will be shown in the next section, the corresponding values for methyl iodif2-131 penetration for the S&S charcoal were of a satisfactory low level.

b 34

F k

Table 9: Profile Along Line of Flow on Weathering Charcoals in Unmodified Outdoor Air - pH and Weight Increase i

pH of Layers

% Weight Increase of Layers Test Months 1

2 3

4 1

2 3

4 NACAR 615 h

5016 1

9.3 9.5 9.6 9.7 21.7 19.8 17.0 14.7 5031 2

8.2

'8 10.0 10.0 21.3 20.7 20.5 17.7 5022 3

7.5 9.8 10.0 10.0 25.9 26.2 26.6 25.7 5097 3

7.9 9.2 9.2 9.3 35.8 35.4 35.4 36.1 E

5098 3

7.9 9.2 9.2 9.2 36.7 35.3 35.5 35.1 5099 3

7.9 9.2 9.3 9.2 36.0 36.1 36.2 37.1 5058 6

3.8 9.4 9.6 9.6 6.5 4.0 3.2 2.9 5057 9

4.1 8.5 9.2 9.2 36.4 35.0 35.2 35.6 NACAR 617

~

_u I

5017 1

8.8 9.4 9.4 9.4 22.2 20.3 18.8 16.9 h

5023 1

8.4 9.2 9.2 9.2 45.9 46.3 44.9 42.6 BC 727 5014 1

8.8 9.3 9.3 9.3 25.2 24.0 22.0 20.5 5070 1

8.3 9.2 9.2 9.2 4.9 5.6 5.8 5.8 5081 1

8.4 9.2 9.2 9.2 11.4 19.1 27.8 28.4 5082 1

8.5 9.3 9.3 9.3 12.8 20.0 26.1 26.2 5083 1

8.4 9.2 9.2 9.2 12.9 19.1 19.6 19.9 5113 1

8.6 9.0 9.0 9.0 46.6 47.0 46.8 46.8 5121 1+

8.0 9.1 9.0 9.0 31.1 36.0 36.6 37.0 5124 1

7.5 8.9 8.8 8.8 33.3 34.7 35.6 35.6 5032 2

7.3 9.3 9.5 9.5 34.8 35.6 34.7 32.2 5065 2

7.3 9.3 9.2 9.4 27.0 24.6 22.2 19.5 5096 2

8.0 9.3 9.4 9.4 46.8 46.6 47.2 48.0 5020 3

7.0 9.4 9.5 9.5 34.5 36.0 35.0 33.0 5056 6

3.1 8.9 9.1 9.0 9.1 3.0 2.6 2.5 5055 9

3.3 8.5 8.8 8.8 47.4 45.1 45.1 44.7 BC 717 I

5084 1

8.2 9.1 9.1 9.1 16.0 23.7 29.0 30.9 5013 1

8.8 9.2 9.3 9.?

24.1 21.8 20.1

8 5010 1

8.5 8.9 9.0 9.2 37.0 36.7 35.5

'4.0 5024 1

8.6 8.6 8.9 9.0 35.3 35.5 35.6 35.6 5019 1

8.1 8.6 8.9 8.8 13.2 11.6 11.8 9.9 E

498 236 35 E

.4

Table 9 (Continued) pH of Layers

% Weight Increase of Layers Test Months 1

2 3

4 1

2 3

4 2701 (American Air Filter) 5039 1

7.6 8.5 9.1 9.1 27.4 30.2 28.2 25.0 40 1

7.6 8.7 9.1 9.1 26.7 29.4 26.7 22.2 61 3

3.6 8.2 8.5 8.6 5.5 2.0 1.8 1.7 5118 6

2.4 7.0 8.0 8.0 27.0 18.9 16.5 14.8 notfinishedl 5120 9

KITEG (Nuclear Consulting Services, Inc.)

5042 1

6.7 9.2 9.6 9.6 16.8 16.2 16.7 ! 17.3 5069 3

2.8 7.2 7.3 7.4 9.2 5.2 5.0 4.7 5119 6

2.4 5.7 6.9 7.0 27.0 20.0 19.1 18.4 511" 9

not finished L-._

Sutcliff & Speakman (5% TEDA) 5033 1

7.1 7.9 7.8 7.9 21.2 15.8 14.7 14.2 5034 1

7.2 8.0 8.1 8.0 14.5 13.7 14.4 14.3 5078 1

8.2 8.6 8.6 8.6 1.0 1.5 6.0 9.4 5079 1

8.1 8.6 8.6 8.6 0.4 1.3 5.8 9.4 5080 1

8.2 8.6 8.6 8.6 0.0 2.3 6.8 9.8 5093 1+

7.7 8.2 8.3 8.3 25.7 26.9 26.3 26.4 5110 1

8.0 8.3 8.3 8.4 19.5 20.8 21.9 21.5 5063 3

4.5 8.7 8.9 8.9 5.9 2.4 2.1 2.0 5064 6

4.0 8.1 8.3 8.4 30.7 28.7 28.5 28.6 5066 9

3.2 7.4 7.9 8.1 26.5 22.2 22.0 22.0 MSA (463563) 5015 1

7.45 7.65 7.65 7.8 19.8 17.3 14.6 11.8 5021 1

6.7 8.2 0.2 8.2 30.0 30.3 30.1 30.3 5050 3

3.4 7.5 7.7 7.8 5.0 1.9 1.6 1.6 5059 6

2.5 6.9 7.8 8.0 8.0 2.4 1.7 1.6 5077 9

2.7 6.9 6.9 7.3 9.2 1.6 0.92 0.06 237

<g

.s 36 r

Table 10:

Correlation of Weight Increases with the Relative Humidity and Dew Point of the Air Average Average Termination Wt. Increase Relative Humidity

( F) Dew Point Test Charcoal Months Date

% (Av.)

48 - 24 24 - 0 48 - 24 24 - 0 5070 727 1

2 Mhy 78 5.5 26 35 23 24 5069 KITEG 3

2 May 78 6.0 26 35 23 24 5058 615 6

2 thy 78 4.2 26 35 23 24 5056 727 6

1 thy 78 4.3 26 35 23 24 5059 MSA 6

1 May 78 3.4 26 35 23 24 5060 MSA 3

4 Feb 78 2.5 59 46

'c 8

d 5061 2701 3

4 Feb 78 2.8 39 46 la 8

5079 S&S 1

1 Jun 79 4.2 73 64 66 63 5G80 S&S 1

1 Jun 78 4.7 73 64 66 63 5063 S&S 6

10 Aug 78 3.1 72 78 72 69 J :-

5078 S&S 1

1 Jun 78 4.4 73 64 66 63 e

CO NOTE:

24-0 signifies the 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> before termination.

N 48-24 signifies the period between 48 and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> before termination of the exposures.

trJ

3.

Results for the Penetration of Methyl Iodide-131 Of the three test-modes or configurations for conducting the methyl iodide-131 test for weathered charcoals (see page 8), it is possible to calculate a result for Mode 2 from the four values of penetration obtained by Mode 1.

Using the expressicn for penetration 1

- ; = exp (- k T)

(1)

C v

C E

1/- In C k

=-

v o

initial concentration, T =

where C = penetration concentration and C

=

1 g

residence time and k reaction rate constant, the values of k are first y

y calculated with the data of Mode 1.

In each of these cases, T = 0.25

.0625 in each layer of Mode 2, the penetration is then sec.

Since T

=

calculated for each of the four layers using the corresponding value of k.

Third, the product is calculated for the desired penetration, y

namely C

C C

7 2

3 4

4 Produc t = - x - x - x - = -

(2) o 1

2 3

0 Some examples are given in Table 11 using the data for weathered charcoals.

It was not possible to make a comparison between calculated and observed penetrations in Mode 2 of the weathered charcoal exan.ples given in Table 11 because all of the weathered sample was required for the four determinations of Mode 1.

Accordingly, two add 4tional samples were weathered under the same conditions with the laboratory control previously used (air at 100 L/ min for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> at 70% RH and at 90%

Ril). The results given in detail in Table 12 show excellent agreement between calculated and observed penetrations of methyl li dide-131 for k

2 59

Table 11:

Calculation of Penetration in Mode 2 Configuration From the Results in Mode 1 Weathered Depth Penetration

-k T Test Layer (cm)

Fraction T

k T

e v Product

• 5016 1

5.08

.0177 0.25 16.137

.0625 0.365 2

5.08

.0064 0.25 20.206

.0625

.283 3

5.08

.0034 0.25 22.736 6625

.241 4

5.08

.0070 0.25 19.847

.0625

.289 0.72%

5031 1

5.08

.0342 0.25 13.592

.0625 0.430 2

5.08

.0132 0.25 17.310

.0625

.339 3

5.08

.0086 0.25 19.024

.0625

.305 4

5.08

.0102 0.25 341

.0625

.318 1.41%

5022 1

5.08

.0862 0.25 9.004

.0625 0.542 2

5.08

.0138 0.25 17.132

.0625

.343 3

5.08

.0119 0.25 17.725

.0625

.330 g

4 5.08

.0081 0.25 35.264

.0625

.300

' 84%

5014 1

5.08

.0267 0.25 14.492

.0625 0.404 2

5.08

.0120 0.2',

17.691

.0625

.331 3

5.08

.0068 0.25 19.963

.0625

.287 4

5.08

.0131 0.25 17.341

.0625

.338 1.30%

D>

so 5032 1

5.08 0.0581 0.25 11.382

.0625 0.491 Co 2

5.08

.0258 0.25 14.630

.0625

.401 3

5.08

.030y 0.25 13.908

.0625

.419 4

5.08

.0345 0.25 13.467

.0625

.431 3.56%

y 5020 1

5.08 0.216 0.25 6.130

. 062:~

0.682 2

5.08

.054 0.25 11.675

.0625

.482 3

5.08

.050 0.25 11.983

.0625

.473 4

5.08

.057 0.25 11.459

.0625

.488 7.6%

• Product deternined from equation (2).

the same charcoal (BC 727). The reproducibility of the laboratory weathering procedure is also established by these measurements.

Table 12: Comparison of the Penetrations of Methyl Indide-131 for the Same Charcoal Weathered in Mode 1 ated Mode 2

+

Weathered Depth Penetration T

T Penetration

-k Test Layer (cm)

Fraction (sec) k (sec) e v Calc (%)

Obsvd (%).

T 5030 1

5.08

.163 0.25 7.256

.0625

.6354 (Mode 1) 2 5.08

.132 0.25 8.100

.0625

.6028 3

5.08

.152 0.25 7.535

.0625

.6244 (90% RH) 4 5.08

.107 0.25 8.940

.0625

.5719 13.6 5132 1,2,3,4 5.08

.137 0.25 13.7 (Mode 2) 5036 1

5.08

.127 0.25 8.254

.0625

.5970 (Mode 1) 2 5.08

.051 0.25 11.904

.0625

.475 (70% RH) 4 5.08

.034

0. ; 13.526

.0625

.4293 6.3 5131 1,2,3,4 5.08

.0612 0.25 6.12 NOTE:

The two columns headed 1,2,3,4 signify that the test column was assembled with equal volumes of carbon from the four weathered layers and arranged in the same seauence.

The results for the penetration of methyl iodide-131 after weathering in outdoor air are summarized in Table 13.

These include all d::ta for the different commercial charcoals at the specified exposure times listed in monthlv increments. These times have now been extended suf ficiently to see the seasonal influence of the environment.

A considerable amount of information is contained in Table 13.

For example, the results in weathering NACAR 615 are assembled in Table 14.

24/

4 98

-i*s:0

Table 13: Methyl Iodide-131 Penetration Through Channels Af ter Weathering in Unmodified Outdoor Air Period

% Penetrations Caled.

Obserd.

Test (Months) 1 l

2 l

3 4

1,2,3,4 1,2,3,4 NACAR 615 5016 1

1.77 0.64 0.34 0.70 0.72 5031 2

3.42 1.32 0.86 1.02 1.41 5022 3

8.62 1.38 1.19 0.81 1.84 5097 3

3.13

.03 5098 3

1.83 5099 3

3.10

.049 5058 6

8.33 0.27 0.34 0.18 0.61 5057 9

6.62

.20 NACAR 617 I

5017 1

1.90 0.62 0.32 0.64 0.70 5023 1

12.91 5.40 BC 727 5914 1

2.67 1.20 0.68 1.31 1.30 5070 1

1.13 5'81 1

0.92

'082 1

0.69 5083 1

0.83 5113 1

13.2 5121 1+

3.31 5124 1

0.81 5032 2

5.81 2.58 3.09 3.45 3.56 5065 2

15.4 4.8 5.1 5.8 6.84 3096 2

3.79 0.16 5020 3

21.6 5.4 5.0 5.7 7.59 5056 6

13.3 0.97 1.50 0.97 2.

5055 9

15.6 BC 717 5084 1

5013 1

0.83 0.44 1.68 0.92 0.87 5010 1

0.67 5024 1

11.7 3.75 3.75 4.86 5.32 5019 1

13.2 11.6 11.8 9.86 11.55 klb s,

41

Table 13 (Continued)

Period

% Penetrations Caled.

Obscrd.

Test (Months) 1 2

3 4

1,2,3,4 1,2,3,4

';G1 (American Air Filter) 5039 1

5.95 3.9 2.6 1.75 3.21 5040 1

4.38 2.8 1.75 1.11 2.21 5061 3

0.287

.051 5118 6

5120 9

KITEC (Nuclear Consulting Services, Inc.)

5042 1

0.73 5069 3

3.22

.09 5119 6

5117 9

butcliff and Speakman 5033 1

8.63 0.52 5034 1

3.88 0.87 0.4.

0.45 0.90 5078 1

.05 5079 1

<.02 5080 1

.02 5093 1+

.13

.02 5130 1

0.39 5063 3

1.93

.05

.13

.08 0.18 5064 6

0.82 0.12 5066 9

0.46

.02 MSA (463563) 5015 1

4.03 1.86l 3.61 2.061 2.73 5021 1

15.5 8.0 8.81 8.39 9.78 5060 3

0.659

.020 5059 6

5077 9

NOTE:

The two columns headr 3 1,2,3,4 signify that the test column was assembled with equal volumes of carbon from the four weathered layers and arranged in the same sequence.

j 'O h

)O 42

Table 14:

The Penetration of NACAR 615 and Duration of Exposure NRL Time Termination Dew Points *F Penetration Test (Months)

Date S-2 0-1 S

5022 3

30 Sep 77 52*

45*

51*

'l.84 5097 3

1 Sep 78 71 72 69 3.13

.03 5099 3

1 Sep 78 71 72 69 3.10

.049 5058 6

1 thy 78 35 38 19 0.61

.17 5057 9

16 Aug 78 75 77 77 6.62

.20 the two samples (5097, 5099), expesed during the same three-month period ending 1 September 1978, gave the reproducibility indicated in Table 14 for the penetration values.

Included are the uncertainties of sampling the starting material, those inherent in weathering and those in the determination of the penetration. The mean value for penetration of 3.12 is based on too few measurements for statistical analysis. The test 5022 also for three-months ending 30 September 1977 showed less penetration, but this behavior may be correlated with the lower dew point just before sampling.

In Table 14, the Column S-2 gives tho dew points two days before termination of the exposure, S-1 gives values one day before, and Colunn S corresponds to the day of termination. Sample 5058 weathered for six months terminated on 1 Fby 1978 during a period of rather dry weather (very low dew point) and showed only 0.61% penetra-tion.

After 9 months of weathering the sample of G 615 showed a high penetration (6.62% in Mode 2) and a corresponding low acidity of the entrance layer (pH = 4.1).

The above results are yet another example of the effect of water adsorption on charcoal and the subsequent penetration of methyl iod id e-131.

The separate contributions of contaminants and water vapor and their synergistic influence on the weathering of cnarcoal are important and critical factors.

The reduction in the partial pressure of water during the period of low humidity weather may function as a

• OO GEB_A 4/d e-4,-

43 1%

regeneration process with respect to a partial recovery of the methyl iodide trapping efficiency.

The weight-gain of a charcoal was found to respond to the meteorological conditions during the exposure. For example, NACAR 617 was exposed for one month in June 1977 and in July 1977.

The data for the two tests with the charcoal a re summarized in Table 15.

Table 15: The One-Month Performance of NACAR 617 in June and July 1977 June July Average Temperature ("F) 74*

80.9 Average Dew Point (*F) 59*

67*

Weight Increase - Tayer 1 22.2%

45.9%

2 20.3 46.3 3

18.8 44.9 4

16.9 42.6 Penetration -

Layer 1 1.9%

12.9%

2 0.62 3

0.32 4

0.64 5.4 The moisture content of the air was less in June than in July and accounts for the two-fold increase in adsorbed moisture of the July sample.

By reference to Figure 8, however, it is seen that the increase comes in the critical region where the penetration increases sharply with relative pressure. As a result a 7-to C-fold increase in penetration was realized.

The attempts to correlate the one-month exposures of BC 727 with neterological data are su nmarized in Figure 9.

The monthly-average dew point and tenarature for each exposure are given in Table 16 with the observed petetration of methyl iodide-131. The latter is plotted (Figure 9) at c function of dew point, relative humidity and the quantity 44 t

14 O, X*

13 I

I 12 l

11 j

l 10 I

l 9

/

,/

8 n

i I

7 f

g" 6

/

/

c 2

/

5 f

/

4 j

0

/

3 j

/

2

/

s O

X

-r

--OC e

• Q X

1 liI l 8 88 I I II Il 3 II I I II I i III III II 5{QDewPoint, 0

70 F

I 3

I I

I I

I I

I I

I I

i 1

50 60 70 X, Relative Humidity, E I

I I

J l

i I

I I

i l

l 1

5 10 15 e Moisture, g/M Figure 9:

1enetration of Methyl Iodide-131 through BC 727 After One-Month Exposure to Outdoor Air (Table 13) 493 245

of water vapor that were present during exposure. The penetration in-creased sharply within the same range since these paramete*s are inter-related. The behavior is similar to that previously reported (Figure 7) for laboratory exposures with water vapor-air flows.

Table 16: One-Month Exposures of BC 727 Average Average Penetration Sample Date Temp.

F Dew Point 5014 2-30 Jun 77 74 59 1.30 5070 7 Jan - 2 May 78 60 44 1.13 5081 2 May - 2 Jul 78 69 56 0.92 5082 2 May - 2 Jul 78 69 56 0.69 5083 2 Fby - 2 Jul 78 69 56 0.83 5113 2 Aug - 1 Sep 78 79 68 13.2 5124 13 Oct - 14 Nov 78 58 45 0.81 5121 1 Sep - 13 Oct 78 70 57 3.31 4.

Behavior in Intermittent Air Flows Frequently, a charcoal filter is place' on a stand-by basis and thus is used with intermittent air flows. One result of such operations may be to redistribu e the adsorbed contaminants through surface mobility on the large area of the activated carbon. Adsorbed molecules are Known to diffuse in directions parallel to the surface and the extent varies with the potential energy barrier that exists.

Low boiling hydrocarbons, for example, may diffuse with less restraint than a strongly held con-taminant like ozone.

In order to observe the possible influence of " resting" impregnated activated carbons, three samples (bC 727, NACAR G 615, and Sutclif fe and Speakman 5% TEDA) were exposed for known periods of outdoor air flow and stand-by.

The weathering was conducted for one month, then held inactive by a secure closure of the inlet and outlet, and then again exposed for an additional month. An additional off-on cycle was 9 b ()

khb b

46

Table 17:

Schedule for Intermittent Weathering in Exposure to Unmodified Outdoor Air at NRL Time folume Exposure Dates Total Exposure n6 Test Charcoal (Hours) (10 cu ft) 1978 (Months)

(10 )

(sec)

Pene.

5094 BC 727 On 1077

.17G4 2 Jun - 17 Jul 11.7

.33 Off 768 17 Jul - 18 Aug on 744

.1155 18 Aug - 18 Sep 7.94

.34 (11.8.302)%

Total On 1821

.2859 2.5 5095 BC 727 On 1077

.1677 2 Jun - 17 Jul 11.6

.34 Off 768 17 Jul - 8 Aug on 745

.1186 18 Aug - 18 Sep 8.18

.33 Off 720 18 Sep - 18 Oct f

On 888

.1450 18 Oct - 24 Nov 9.97

.32 (12.0.106)%

Total on 2710

.4313 3.7 5112 S&S On 740

.1150 18 Jul - 18 Aug 7.91

.34 Off 744 18 Aug - 18 Sep

-}

On 720

.1162 18 Sep - 18 Oct 7.99

.32 cub off 720 18 Oct - 18 Nov on 672

.0985 18 Nov - 18 Dec 3.0 6.77

.35

(.019.002)%

rsJ Total on 2132

.3297 D.

~J 5111 G 615 On 740

.1156 18 Jul - 18 Aug 7.95

.34 off 744 18 Aug - 18 Sep on 720

.1165 18 Sep - 18 Oct 2.0 8.01

.32

/.089.014)%

To tal On 1460

.2321

added in two cases. The schedule of these exposures is suumarized in Table 17, where n is the number of filter displacements and t is the average residence time during the exposure perioc:s.

Although not all of these measurements have been completed, the intermittent weathering of BC 727 appears to be more degrading than con-tinuous operations with tne same carbon. A summary of the results for BC 727 is given in Table 18.

Table 18: Intermittent Exposures with BC 727 Total Exposure Penetration Test Operation Time (months) 5032 Continuous 2

3.56 5065 2

6.84

.12 5096 2

3.79

.16 5020 3

7.59 5094 Intermittent 2.5 11.8

.302 5095 3.7 12.0

.106 Incomplete results for another charcoal, NACAR G 615, which contained TEDA as part of the impregnation, indicate a different behavior (Table 19).

Table 19:

Intermittent Exposures with NACAR G 615 Time Penetration Test Operation (Months) 5031 Continuous 2

1.41 5022 Continuous 3

1.84 5111 Intermittent 2

0.09 The " resting" of the filter in this case appeared to reduce the subsequent penetration of methyl iodide.

The difference in behavior may be due to the type of impregnation. The G 615 contains c.mong other things soms TEDA and tne BC 727 contains KI in the impregnation. The TEDA of the 48

/l G o

') f} OO t/0 L

impregnation appears to be stable in the environment of the adsorbed contaminants and in fact improves during " resting".

Additional work is obviously needed to include the influence of the changing concentratioas of moisture that existed during the exposures to outside air and in the period just before the termination of the weatl.ering.

Future experimen-tations may be more amenable to the control available in laboratory ex-posures rather than in outside air.

4(;48 249 49

V.

Concluding Remarks 1.

Moisture Influence on Charcoal Efficiency It has been shown in this report that the interaction of water vapor with impregnated charcoals, as judged by methyl iodide trapping efficiency, depends on relative pressure and contact time.

In the laboratory exposures (Appendix 6), the water retained by the charcoals was approximately 1% of the water introduced during the 160 hours0.00185 days <br />0.0444 hours <br />2.645503e-4 weeks <br />6.088e-5 months <br />. After this period in air flows of 50% RH, a gradient in the water rctained was observed in the four layers (sae Figure 10).

The dynanic adsorption behavior of the charcoals for water vapor is thus shown.

In air flows of 70% RH and 90% RH, gradients in water-retained are not observed which demonstrates the greater surface mobility of adsorbed water at high humidities. The hysteresis behavior of water adsorption and desorption explains why it is difficult to dry an activated carbon bed af ter exposure to humidities greater than 50% RH.

In addition to this mass transport factor, the adsorptivity deteriorates after long 2xposutes to air of high dew point relative to air of low dew 1> int.

In the environment of NRL, the dew point in the last three years has been above JO F for o-"y 30 to 40% of a year (see Appendix 2).

In the southeastern.reas of che country, the percentage is larger and in the desert areas it is less.

It remains to be demon-strated to what extent the useful life of a charcoal installation (without local abnormal loading) depends on the existing meterological conditions.

2.

Moisture and Contaminant Influence on Charcoal Efficiency The adsorption isotherms of organic compounds on activated carbons are of the Langmuir _ype and the quantity adsorbed at low partial pressures is large.

This behavior is quite different than a water adsorption isotherm. The removal efficiency in a flow of air through a

,. 3 A00 dju niO 50

1 I

I I

BC 727 x

J 617 N

MSA KITEG T

s 2701 b

10 N

O

-O S&S I

I i

i 1

2 3

4 Sequence - Entrance to Exit Figure 10: Weight-Gains (%) of the Four Layers Exposed 100 Hours at 50% RH Pj8 251 51

charcoal depends on the molecular species as well as the source of activated carbon.

In a ficw system the concentration in the first effluent air is much less than steady-state adsorption.

Eventually, the steady-state value finally breaks through as indicated by general sigmoidal dependence in Figure 11.

When moisture and contaminant are both present, the removal of the contaminant is independent of moisture at low relative humidities since this is the region of small water adsorption. The testing con-ditions that specify 95% RH, however, correspond to high surface coverage by moisture and in this region there is a competition of the water molecule and methyl iodide for the available surface. A successful impregnated charcoal of high trapping efficiency must interact strongly with the remaining surface and some mechanism must be present that is highly efficient in doing so.

Deitz and Jonas (17) have proposed a catalytic trapping of methyl iodide at specific sites on the impregnated charcoal and the observed kinetics have been tested over a ten-fold change in residence time.

A general observation in the profile of the methyl iodide penetration measurement through the four-layer test bed is not only a definite greater penetration through the entrance layer relative to the remaining three layers, but also a somewhat greater penetration througli the exit layer relative to the second and third layers.

This behavior is compatible with a chromatographic separation among the several components of the gaseous contaminants in the air flow and perhaps to a differential surface mobility of a component of the impregnation.

Superimposed on the normal weathering of charcoal by atmospheric contaminants and moisture in the air flow to a filter are organic vapors derived from local solvent spills and/or solvent vapors from large paint operations conducted within a facility (11).

These are special and isolated occurrences that can, however, accumulate and involve a consid-erable ourface coverage of the charcoal. The desorption of a highly GQ

[t / u 52

f I

I I

.80

.60 E

C A

Di5.40 m

.20

.10

_-.,-__3___.

__ 7 ie TOTAL FLOW OF METIIYL IODIDE AND AIR Figure 11: General Dependence of Fractional Penetration Over the Complete Range of Breakthrough Concentration

-r ; R.s

f. G 53

volatile caterial into flowing air (12) may be effective in removing some of the adsorbed vapor; also, the removal would be enhanced during a test procedure which uses a temperature of 80* or 130*C.

However, the experience to date given in Table 7 has shown that at ambient temperatures, the recovery level of the methyl iodide trapping efficiency upon pre-

~

humidification is not realized.

In fact, it is further degraded.

The program of weathering with untreated outdoor air is now being supplemented by pertinent laboratory experiments designed to weather charcoals at high organic concentrations. These measurements now in progress in FY79 should yield useful information as to the influence of accidental solvent spills on chat coal ef ficiency.

The possibility of obtaining precursor information that could be used to anticipate a need for charcoal replacement was raised at the beginning of this report. To this end, it might be helpful to integrate the quantities of organic vapors that get into the air ducts leading to a charcoal filter. Any excessive hydrocarbon loading on the charcoal could then be determined and thus, it would be possible to an'.icipate the need for replacement due to such sources of contamination.

3.

Future Plans for FY79 The following ba31c tasks will be performed during the continua-tion of the research activities in FY79:

(1) Laboratory controlled exposures of commercial charcoals to air inixtures with water vapor and pollutant.

(2) Weathering of charcoals in ambient un-modified outdoor air at the NRL site and at two additional locations selected for dif f erent environmental conditions.

(3) Laboratory examination of spent charcoals of known history.

4[/h

} } /g 54

Labora tory-Controlled Exposures One significant observati;n in the research in progress is the important contribution of water vapor of high relative humidity to the degradation of impregnated charcoals.

Furthermore, a synergistic influ-ence of the water vapor in mixtures with hydrocarbon vapors exists which has an important bearing on the degradation.

It is planned, therefore, to weather three of the charcoals now being studied (BC 727, C 615 and S&S-5% TEDA) with air mixtures which w contain n-hexane, methanol, cyclohexanone, or methylisobutyl ketone.

The exposures will be in air flows of 100 L/ min for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> at ambient temperature (22-23"C).

The air will be maintained at 90% Ril and a hydrocarbon concentration will be selected to yield a weight increase of the charcoal that vill result in significant loss in trapping efficiency for methyl iodide-131. These measurements will establish the magnitude of organic loading that is compatible with good methyl iodide trapping under the conditions of the exposures.

In the previous report for FY77 (te' pp.16-17(1)) the labora-tory measurements with ozone were completed at a concentration of 2.5 to 2.7 ppm.

The ozone generator has now been adjusted to produce lower concentrations in the total air flow of 100 L/ min.

A lower concentration of about 0.1 ppm will be used and c posures will be repeated in 50%, 70%

and 90% RH during FY79.

The lower concentration is desired for weather-ing the charcoal since it is a closer approximation to actual environ-mental conditions.

In the real world the environment contains, of course, complex mixtures of pollutants in variable proportion. It is planned to make a few charcoal exposures in the laboratory with an air flow containing water vapor, hydrocarbon, ozone or sulphur dioxide.

This spot check with a multi-component pollutant mixture in 90% RH air may indicate the presence of factors that might cancel each other in the influence on methyl iodide-131 trapping.

khb 55

Exposure to Outdoor Air at NRL The exposures of the six commercial charcoals started in FY78 will be completed to include 6 and 9 month periods.

Exposures of BC 727 and G 615 of 12-month duration will also be completed. One charcoal, BC 727, will be exposed for one month in each of twelve consecutive months in order to establish the seasonal influence on the trapping

~

efficiency of one particular charcoal.

In connection with intermittent exposures, the BC 727 and the S&S-5% TEDA charcoals will each be exposed for three one-month periods with one month rests between each exposure.

In all cases the weathered bed of charcoal will be divided into four equal layers for analysis of the methyl iodide penetration in each of the four successive layer' in the flow direction. There is a gradient of pollutants in a weathered bed and this gradient is responsible for the profile observed in the methyl iodide-131 penetration. A continued study will be made during FY79 of the meteorological conditions during the la=*

few days before terminating an exposure to outdoor air.

When the de-sorption of adsorbed water is favorad by a continuous period of dry wea ther, the subsequent efficiency for methyl iodide-131 trapping should increase, provided the accumulation o1 pollutants has not exceeded a specified surface coverage to be determined from laboratory experiments.

The data will be examined from this point of view.

Exposares to Outdoor Air at other Sites There are two categories of contaminants that have a changing influence on the weathering of charcoals:

(1) local meteorological conditions that define the water content of the air, and (2) the concen-trations of pollutants that vary in the vicinity of the weathering.

It is planned, therefore, to expose charcoal samples to the environmental conditions at locations other than NRL.

One site is the Argonne National Laboratory near Chicago and another is a dry area in the far west.

k9hp 56

It has been pointed out (Appendix 2) that the monthly average dew points observed at the National Airport Weather Station showed a pattern of similar variations for the period 1970-1978. A similar compil-ation has been made for the Chicago O' Hare International Airport (Appendix

9) for the period 1971-1978. The two locations differ in that the time when the dew point is above 50*F at O' Hare is half that of National.

The O' Hare airport is in the general vicinity of the Argonne National Laboratory.

The second location will be sought where a drier climate exists.

It is also necessary to have additional information at these other locations on the pattern of pollutants that exist during the weathering.

The Chicago location is in a more industrialized area than NRL and published records assembled by U.S. Environmental Protection Agency (14) for the Chicago area show a high sulfur dioxide emission.

Contact will be made with the Chicago EPA stations and the records of the p;11utant concentrations in the immediate area of the Argonne Laboratory will be obtained. From the records comparisons will be made to characterize the pollutant concentrations with respect to the influence on nethyl iodide-131 penetration data (15).

The field units will be assembled to be capable of exposing two samples of charcoal in each unit.

Separate air flow reters and blewers will be used for each sample. The only facility required in the field is a source of 120 volts AC.

Samples of

",C 727 and G 615 charcoals will be exposed for periods of cae-month and six-months at each site.

Service Charcoals With the cooperation of the research staff of Nuclear Regulatory Commission, a number of charcoal samples will be obtained that have been used in commercial operations and which have well defined exposures.

Laboratory tests will be performed at NRL co determine those charcoal properties that are pertinent to residual efficiency for methyl iodide-131 trapping.

57 khb b}

n

_ _. -... -. i -

References 1.

"Ef fects of Weathering on Impregnated Charcoal Performance" by Victor R. Deitz, Naval Research Laboratory, NUREC/CR-0025 (1977).

2.

R. R. Bellamy and V. R. Deitz, " Confirmatory Research Program -

Effects of Atmospheric Contaminants on Commercial Charcoals,"

Proc. 15th DOE Nuclear Air Cleaning Conference 1978.

3.

A. Stamulus, "The 1976 NRL Air Quality Daca," NRL Memo Report 3652, 41 pp.

4.

A. Stamulus, "The 1977 NRL Air Quality Data," NRL Memo Report 3764, 27 pp.

5.

D. A. Collins, L. R. Taylor and R. Taylor, "The Development of Impregnated Charcoals for Trapping Methyl Iodide at High Humidity,"

TRC Report 1300 (W), U.K. A.E. A. (1967).

6.

R. E. VanderVennen, "The Oxidation of Activated Carbons at Room Temperature," NRL Report 4823 (24 August 1956).

7.

Local Climatological Data, National Weather Service Of fice, Washing-ton National Airport, Monthly Summary Reports for 1978, N.O.A.A.,

Ashville, North Caroli na.

8.

R. C. Milham and L. R. Jones, " Iodine Retention Studies," DP 1213 and DP 1234, Savannah River Laboratory (1969).

9.

Victor R. Deitz, " Survey of Char Revivification and Filtration,"

301 pp., National Bureau of Standards, Washington, D.C.

(1947).

10. E. C. Bennett and D. E. Strege, " Evaluation of Weathered Impregnated Charcoals for Retention of Iodine and Methyl Iodide," UNI-251 (August 8, 1974) and UNI-425 (November 7, 1975), United Nuclear Industries, Inc., Richland, Washington.

11. A. G. Evans, "Parsonal Communication," Publication Pending in 1978 Report from the Savannah River Laboratory.

12. J. Louis Kovach and L. Rankovic, " Evaluation and Control of Poison-ing of Impregnated Carbons Used for Organic Iodide Removal," Proc.

15th DOE Nuclear Air Cleaning Conference, 1978

13. D. R. Muhlbaier, " Standard Non-Dentructive Test of Carbon Beds for Reactor Confinement Applications - Final Progress Report," Feb -

Jun 1966, DP 1082.

14. National Air Quality and Emissions Trends Report, 1976.

EPA-450/1-77-002 December 1977, EPA Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina 27711.

58 498 25f7

15. A. Stamulis, "The Characterization of Pollutant Concentration by a Relative Measure of Variability," NRL Memorandum Report 3659, (1977).

16. Victor R. Deitz and Charles H. Blachly, "The Zf fect of Exposure Times in the Prehumidification of Impregnated Charcoals," Proc.

14th DOE Air Cleaning Conference, Volume 2, 836-843 (1976).

17. Victor R. Deitz and Leonard A. Jonas, " Catalytic Trapping of Methyl Radioiodide by Beds of Impregnated Charcoal," Nuclear Tech. 37_,

59-64 (1978).

08 259 59

Appendix 1:

Physical Properties of Impregnated Lnarcoa'.s Charcoal Weight Percent on Each Sieve Nom.

Hard.

Particle fulk Dusting

1. 8 10 12 14 16 20 PAN Size (ASTM)

Diameter d.

Coef.

Change BC 727 0.4 10.0 36.0 36.2 16.1 1.3 0.2 Ax16 94.8 88.1 0.46 0.20 BC 717 0.9 6.6 27.2 41.2 21.8 2.2 0.1 8x16 97.3 94.1 0.51 0.20 C 615 1.4 10.5 30.8 40.5 15.4 1.0 0.3 8x16 97.4 96.4 0.54 0.04 G 617 0.5 6.9 35.4 43.5 11.6 1.8 0.2 8x16 96.8 93.5 0.43 0.06 MSA (463563) 0.9 7.5 30.8 42.2 17.4 1.0 0.2 8x16 96.6 97.4 0.56 0.0f AAF '701 1.4 12.0 33.4 36.2 14.0 2.8 0.3 8x16 90.6 80.0 0.44 0.22 KITEC 0.2 9.9 40.3 34.4 13 -.

1.2 0.6 8x16 95.7 94.6 0.42 0.13 SS (5%

0 2.3 36.2 51.9 6.4 1.4 1.8 10x16 85.4 82.0 0.51 1.6 TEDA) l 1ASTM Hardness (Av. Particle Dia. After Hardness Test /Av. Dia. Before Test) x 100 sf' 3

c;3 Density A.S.T.M. Procedure D-2854 Dusting Coefficient (method developed at NRL to be published in 1979)

N C7%

NOTE: Measurements made at NRL by Poonsuk Pongpat, IAEA Fellow, 1978-1979.

C3

e Appendix 2

Dew Points, F (Monthly Average) at the Washington ?iational Airport 1970 1071 1972 1973 1974 1975 1976 1977 1978 January 17 19 27 23 31 29 20 12 18 February 22 25 23 23 23 28 29 23 15 March 28 25 30 40 31 29 35 36 28 April 41 33 39 42 41 34 38 44 35 May 54 49 53 50 51 56 49 56 52 June 61 64 59 65 60 62 60 59 51 July 65 64 67 66 64 66 64 67 67 August 65 64 65 67 67 67 66 68 71 September 61 63 61 60 59 59 60 63 60 October 51 57 44 48 42 52 46 44 45 d

November 39 36 35 36 36 41 29 40 40 December 28 34 33 29 31 28 22 26 28

s,.

i 1

]..

.)

\\

1 y.

o a

6 A

hi

~~

c, (*'

61

.5 L_

s.

,),,.

3 T8,3;k'

... ' -A'

'^.-

• I

Appendix 3: Monthly Average Concentrations in ppav of Pollutants During 1976 and 1977 at NRL 0

S0 NO RHC*

CO 3

2 2

Month 1976 1977 1978 1976 1977 1978 1976

'977 1978 1976 1977 1978 1976 1977 1978 January

.013 0.007

.013

.042 0.052

.028

.038 0.018

.011 0.11 0.28

.04 1.58 1.92

.45 February

.012 0.010

.038 0.029

.046 0.055

.09 0.48 1.32 1.22 March

.014 0.012

.027 0.023

.036 0.079

.05 0.24 0.08 3.77 April

.010 0.013

.034

.024 0.023

.016

.028 0.051

.087

.20 0.40

.02 0.68 0.63 1.10 May

.008 0.015

.037

.017 0.020

.013

.024 0.047

.031

.25 0.22

.10 0.54 0.32 1.24 June

.022 0.020

.052

.015 0.020

.014

.020 0.116

.006

.49 1.06

.05 0.33 0.98 1.06 July

.040 0.040

.035

.026 0.023

.014

.044 0.078

.025

.53 0.07

.07 1.23 0.95 1.06 August

.038

.026

.015

.029

.011

.47

.06 1.81 1.25 September

.013

.030

.035

.024

.035 0.29

.02 1.92 1.14 October

.008 0.018

.055

.019 0.015

.024

.050 0.075 0.08

.09 1.65 1.14 1.56 November

.010 0.013

.012

.035 0.015

.029

.057 0.028 0.11 0.04

.28 2.67 1.17 2.25 December

.006 0.012

.006

.036 0.022

.017

.084 0.061

.015 0.49 0.06

.89 1.79 1.62 1.52 43, so CO Yearly

• excludes CH4 Ps) Average

.013 0.014

.031

.u27 0.024

.019

.043 0.058

.027 0.29 0.25 0.16 1.,42 1.33 1.36 Ch N

"The 1976 NRL Air Quality Data" by A. Stamulis, NRL Memo Report 3652, 41 pp.

"The 1977 NRL Air Quality Data" by A. Stamulis, NRL Memo Report 3764, 27 pp.

"The 1978 NRL Air Quality Data" by A. Stamulis, unpublished data.

Appendix 4:

Proposed Radiciodine/ Methyl Iodide Standard Test Conditions of ASTM D 28.04, 1978 Section 3.1 3.2 3.3 3.4 3.5 Methyl Iodide Mathyl Iodide Methyl Iodide Elemental Iodine Elemental Iodine Test Description Penetration Penetration Penetration Penetration Retention 30 C 95% RH 80 C 95% RH 130 C 95% RH 30*C 95% RH Units Test Adsorbate

(

C11 "3

)

)

3 2

2 Test Adsorbate 3

Concentration 1.75 0.25 1.75 0.25 1.75 0.25 17.510.5 75 5 mg/m Equilibration Temp 30.0 0.5 80.0 1.0 130 2 30.0 1.0 30 5

• C

1. I RH 95 2 (Note a) 95 3 95 2 (Note a)

Duration 16.0 0.5 0

(Note b) 16.0 0.5 0

hr Feed Temp 30.0 0.5 80.0 0.5 130i2 30.0 0.5 30 5 C

Period RH 95 2 35 1 95 3 95 1 Ambient Duration 120!1 60 1 60 1 120 1 10.0 0.2 min Elution Temp 30.0 0.5 80 0.5 130 2 30.0 0.5 180 3

• C 4

Period:

'O RH 95 1 95 1 95 3 95 1 NA CO Duration 240 1 240 1 240 1 24011 240 1 m'n Absolute Pressure (Note c) 104 5 104 5 104 5 104 5 104 5 k Pt g

O Gas Velocity 12.2 0.5 12.2 0.5 12.2 0.5 12.2 0.5 12.2 5 m/mt, u

Bed Depth (Note d) 50 1 50 1 5011 50 1 25 1 mm Above list is standard for adsorption media used in 50 mm bed depth tray filters, as described in AACC CS-8 and for media used in other med depths and operated at tbc same gas velocity (12.2 0.5 m/ min).

For other operating velocities and for all media to operate at conditions substantially different from the above, any deviations from the above list msut be specified.

!iOTES :

a.

For each of these tcsts, the test bed is brought to the listed equilibration temperature without air flow before other phases of the test begin.

For tests 3.2 and 3.5 this thernal equilibration is the only equilibration. For tests 3.1, 3.3 and 3.4, humid air at the stated temperature and humidity is passed through the beds for the stated period followinc bed warm-up.

b.

For test 3.3, humid air flow is maintained for 2.0 0.1 hr, or until the upstream / downstream dry-bulb temperature differential is less than 2*C.

c.

101 kPa = 1 atm.

Tests 3.1, 3.2, 3.4 and 3.5 are run slightly above one atmosphere to allow for a blow-through system with flow measurement, demister, etc.

d.

The test bed for tests 3.1 - 3.4 may be a single canister of full depth, or two 25 mm deep canisters in series.

For test 3.5, a single 25 mm deep canister is used.

493 264 64

Appendix 5: Temperatures Observed Between Sample and Back-up Beds during Methyl Iodide-131 Penetration Test for Sample #5088 (1,2,3,4), Weathered at 93% Ril TIME TEMPERATURE *C

%RIl

.IN" TEMPERATURE *C

%RH INLET OUTLET INLET OUTLET I

1300 29.5 30.0 94.4 PURGE ON 1300 30.0 30.0 94.4 3

1305 29.5 30.0 94.4 1505 30.0

~ 30.0 94.4 1310 29.5 29.5 94.4 1510 30.0 30.0 94.4 1315 29.5 29.5 94.0 15.l5 30.0 30.0 94.4 1320 29.5 29.5 94.0 1520 30.0 30.0 94.4 1325 29.5 29.5 94.0 1525 30.0 30.0 94.4 1330 30.0 30.0 94.4 1530 30.0 30.0 94.4 1335 30.0 30.0 94.4 1535 30.0 30.0 94.4 1340 30.0 30.0 94.4 1540 30.0 30.0 94.4 1345 30.5 30.5 94.4 1545 30.0 30.0 94.9 1350 30.5 30.5 94.9 1550 30.0 30.0 94.5

~

1355 30.5 30.5 94.9 1555 30.0 30.0 94.4 1400 30.5 30.5 94.9 16;0 30.0 30.0 94.0 1405 30.5 30.5 94.4 1605 30.0 29.5 94.4 1410 30.5 30.5 94.4 1610 30.0 30.0 94.9 1415 30.5 30.5 94.4 1615 30.0 30.0 94.4 1420 30.5 30.5 94.4 1620 30.0 30.0 94.4 1425 30.5 30.5 94.4 1625 3(.0 30.0 94.4 E_

1430 30.0 30.5 94.9 1630 30.0 30.0 94.4 s-

=

1435 30.0 30.5 94.9 1635 30 0 29.5 94.4 1440 30.0 30.5 94.4 1640 30.0 30.0 94.4 1445 30.0 30.5 94.4 1645 30.)

30.0 94.9 1450 30.0 30.0 94.4 1650 30.0 30.0 94.9 1455 30.0 30.0 94.9 1655 30.0 30.0 94.9 FEED OFF 1500 30.0 30.0 94.9 PURGE OFF 1700 30.0 30.0 94.9 NRL SAMPLE = 0.140 (1) pCi 0.23%

Backup A

= 0.108 (0) pCi 0.39%

Backup B

= 0.723 (-3) pCi 4.34%

[

NRL Penetration = (7.21 0.05)%

u 498 26T

?

A1,pendix 6: Dependence of Weight Increase and the pH of the Water Extract after 100 hr Exposure at Designated Relative Humidity at a Flow of 100 L/ min

% Wt. Increase in Layer pH in Layer Charcoal

% RH 1

2 3

4 1

2 3

4 BC 727 50 27.7 26.3 25.1 24.2 9.4 9.5 9.5 9.6 70 45.4 45.3 45.5 45.3 7.7 9.2 9.1 8.8 90 47.7 47.7 47.5 47.3 8.2 9.1 9.1 9.2 G 615 50 22.3 19.6 19.5 18.6 9.9 9.9 9.9 9.9 70 28.6 28.5 28.6 28.6 9.0 9.5 9.6 9.6 90 29.8 30.0 29.7 29.9 9.5 9.5 9.4 8.8 MSA 463563 50 23.2 21.5 20.7 20.1 8.2 8.3 8.3 8.3 70 35.9 36.1 36.5 36.1 8.1 8.1 8.1 8.1 90 38.4 38.9 39.9 38.7 8.3 8.3 8.3 8.2 S&S 50 16.2 35.4 15.'

14.8 8.4 8.4 8.4 8.4 (5% TEDA) 70 26.4 26.8 27.2 26.5 8.3 8.3 8.4 8.4 90 31.7 31.7 31.9 32.1 8.6 8.7 8.7 8.7 AAF 2701 50 21.3 19.2 18.1 17.0 9.0 9.0 9.1 9.1 70 44.1 44.2 43.3 43.0 8.7 8.5 8.6 8.6 90 51.0 51.3 51.5 52.2 8.7 8.7 8.7 8.7 G 617 50 22.7 20.5 19.6 18.6 9.4 9.4 9.4 9.5 70 58.2 58.3 55.9 57.0 9.2 9.2 9.2 9.2 90 61.9 60.6 63.0 60.3 9.6 9.6 9.6 9.6 KITEC 50 19.5 18.8 18.3 17.8 7.6 7.6 7.7 7.7 70 28.6 28.3 29.7 29.8 7.7 7.6 7.7 7.7 90 38.8 39.6 40.5 41.3 7.8 7.7 7.7 7.7 k9b 2bb 66

Appendix 7: ASTM Suggested Performance Requirements of New Nuclear Grade Carbons (Draft 2, 7 August 1978)

ASIN Test Test Method Specificar n l.

Methyl iodide penetration at 30*C, 05% RH( )

D 3.0 percent, maximum 2.

Methyl iodide penetration at 80*C, 95% RH D

1.0 percent, maximum 2) 3.

Methyl iodide penetration at 130*C, 95% RH D

2.0 percent, maximum 4.

Elemental iodine penetration 030*C, 95% RH(y)

D 0.1 percent, maximum 5.

Elemental iodine retention @l80 C D

99.5 percent, minimum Physical Properties ASTM Test Test Method Specification 1.

Apparent dr.sity D 2854 0.38 g/ml, minimum 2.

Particle size distr.bution, D 2862 ASTM E-11 Steves:

Retained on No. 6 0.1 percent, maximum Retained on No. 8 5.0 percent, maximum Through No. 8, Retained on No. 12 60.0 percent, maximum Through No. 12, Retair,ed on No. 16 40.0 percent, minimum Through No, 16 5.0 percent, maximum Through No. 18 1.0 percent, maximum 3.

Ash content (3)

D 2866 State value 4.

Moisture content D 2867 State value 5.

Ignition temperature D 3466 330 C, minimum 6.

CC1 ctivity (3)

D 3467 60 percent, minimum 4

7.

Ball-pan hardness D....

92 percent, minimum 8.

pH D....

State value (1) - Methyl iodide end elemental iodine tests at 30*C and 95% RH to be performed only for qualification purposes.

(

- Methyl iodide test at 130 C and 95% RH to be performed only for qualification purposes on activated carbon to be installed in primary containment cican-up systems.

(3) - These tests to be performed on the base carbon prior to impregnation.

49a 267 67

Appendix 8: Relative Humidity % and Dew Points (*F)

Observations at 3-hour Intervals During the 48 Hours Before Charcoal Sampling Date Hour

% RH d.p.

• F Date Hour

% RH d.p. *F 2 May 13 28 29 4 Feb 13 36 6

10 37 28 10 44 5

7 48 27 7

57 6

4 51 26 4

55 8

1 44 25 1

47 9

1 thy 22 32 23 3 Feb 22 47 10 19 23 19 19 47 11 16 20 19 16 39 10 13 23 21 13 41 10 10 24 18 10 47 11 7

30 18 7

62 11 4

32 19 4

63 13 1

23 17 1

69 16 30 April 22 23 20 2 Feb 22 63 17 19 26 29 19 63 18 16 31 40 16 67 22 1 June 13 40 61 10 Aug 13 59 70 10 51 61 10 69 71 7

62 60 7

93 71 4

71 60 4

93 71 1

84 65 1

90 70 31 bby 22 76 65 9 Aug 22 87 70 19 67 65 19 83 71 16 65 70 16 55 69 13 79 70 13 52 69 10 76 67 10 61 70 7

79 66 7

85 74 4

87 65 4

91 74 1

79 65 1

85 74 30 dby 22 69 63 8 Aug 22 72 73 19 65 67 19 68 74 16 50 65 16 63 73 sa 268 6o v 68

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11 21 18 21 13 1

9 February 20 14 22 19 20 25 17 10 March 25 23 35 29 25 31 32 24 April 32 35 38 39 33 37 38 35 May 41 48 44 47 50 43 50 47 June 60 53 59 55 61 56 53 56 July 58 62 64 61 61 60 63 63 August 59 65 65 61 64 57 60 62 September 58 57 57 49 50 49 57 58 October 51 41 30 41 43 36 43 41 November 30 32 34 33 39 20 33 33 December 28 20 23 25 25 11 18 20 69

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