BMI-X-660

AN ASSESSMENT OF THE POTENTIALLY BENEFICIAL USES OF KRYPTON-85

Final Report, Task 64

BATTELLE Columbus Laboratories 505 King Avenue Columbus, Ohio 43201 DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Energy Research and Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assunnes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. BMI-X-660

AN ASSESSMENT OF THE POTENTIALLY BENEFICIAL USES OF KRYPTON-85

Final Report, Task 64

Philip E. Eggers William E. Gawthrop

BATTELLE Columbus Laboratories 505 King Avenue Columbus, Ohio 43201

NOTICE This report was prepared as an account of work sponsored by the United States Government Neither the United States nor the United States Energy Research and Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or impbed, or assumes any legaJ liabibty or responsibibty for the accuracy, completeness or usefulness of any information, apparatus, product or process disUosed, or represents that its use would not mfnnge pnvalely owned rights

Prepared for United States Energy Research and Development Administration Under Contract W-7405-eng-92

Report Date: June, 1975

>

DrSTRlBUTiCN OF THIS DOCdulENT fS UNLir^/slTED TABLE OF CONTENTS

INTRODUCTION 1 SUMMARY 2 RECOMMENDATIONS 5 BACKGROUND AND CHARACTERISTICS OF KRYPTON-85 5 Properties, Collection, and Enrichment 5 Output by the Nuclear Power Industry 8 TECHNICAL ASSESSMENTS 8 Self-Lumlnous Light Sources 8 Lights for Underground Mines 18 Lights for Inland Waterways 24 Lights for Airport Visual Aids 24 Other Lighting Concepts 30 Military Applications 31 Conclusions 34 Technical Assessment of Radioisotope Thermoelectric Generators Involving Krypton-85 Heat Sources 34 Introduction 34 Description of Selected RTG Concepts 36 One Watt(e) RTG 37 Forty-^llllwatt(e) RTG 39 Potential Benefits of Kr3T)ton-85 RTG's 42 Potential Limitations of Krypton-85 RTG's 42 Conclusions 43 Dynamic Energy Conversion Systems 44 Brayton-Cycle Systems 46 Stirling-Cycle Engines 47 Ranklne-Cycle Engines 48 Conclusions 49 Polymerization 49 Conclusions 51 Concepts Based on Property 1 51 Concepts Based on Property 2 51 Concepts Based on Properties 5 and 6 53 TABLE OF CONTENTS (Continued)

Page

Nondestructive Testing 54 Gauging 54 Leak Detection and Fluid Flow Tracing 55 Flaw Detection and Thermal Mapping 56 Miscellaneous Applications 57 Conclusions 58 Biomedical Applications 59 Conclusions 60 Waste Treatment 61 Specific Applications 64 Military Unique Waste Disposal or Waste Treatments 64 Germ-Warfare Agents 65 Chemical-Warfare Agents 65 GB and VX 66 Persistent Organics in Wastewater 66 Conclusions 67 Environmental Control of Submerslbles 69 Submersible Environmental Control System 69 Personnel Transfer Capsule Environmental Control Gas Heater 70 Wet Suit or Dry Suit Diver Heating System 70 Submersible Battery Heaters 70 Conclusions 71 REFERENCES 72 APPENDIX A SELECTED PHYSICAL PROPERTIES OF KRYPTON-85

APPENDIX B

THE NUCLEAR POWER INDUSTRY

APPENDIX C

QUANTITATIVE ESTIMATION OF KRYPTON-85 QUANTITIES REQUIRED TO DESTROY REFRACTORY MOLECULES LIST OF TABLES

Page

Table 1. Comparative Properties of Three Radioisotopes Used for Self-Lumlnous Lighting Applications ^^ Table 2. Comparisons of Some Common Levels of Brightness .... i^ Table 3. Candidate Applications for Krypton-85 Self- Lumlnous Lights 17 Table 4. Dynamic Energy Conversion System Applications 45 LIST OF FIGURES

Figure 1. Projected Cimiulative Availability of Krypton From Light Water Reactors(21) 10 Figure 2. Maximum Visible Distance as a Function of Activity of Krypton-85 14 Figure 3. Increase in Maximum Visible Distance by Optically Increasing the Diameter of Source 15 Figure 4. Bare Source Radiation Profiles as a Function of Brightness 16 Figure 5. Flat Pan Krypton-85 Self-Lumlnous Light Source .... 19 Figure 6. Reflector - Type Krypton-85 Self-Lumlnous Light Source 20 Figure 7. Concept for Krypton-85 Self-Ltraiinous Light Source Used as a Delineation Device in Underground Mines (Passageway Cross-Sectional View Shown Above) 22 Figure 8. Concept for Krypton-85 Self-Lumlnous Light Source Used as a Form of Low-Level Area Illumination 23 Figure 9. Concept for High-Intensity Krypton-85 Self- Lumlnous Light Used in a Buoy 25 Figure 10. Concept for a Krypton-85 Self-Lvimlnous Light Source Used as a Barge Marker 26 Figure 11. Concept for a Krypton-85 Self-Lumlnous Light Source Used as a Pier Marker 27 Figure 12. Sketch of a Krypton-85 Runway Marker From a Photograph Supplied by Permission of American Atomics Corporation, Tucson, Arizona 28 Figure 13. Concept for Krypton-85 Self-Lumlnous Light Source Used for Runway Delineation 29 Figure 14. Concept for a Fixed Installation Physical Perimeter Security System Using a Krypton-85 Self-Luminous Light Source 32 Figure 15. Concept for a Field Installation Physical Perimeter Security System Using Krypton-85 Self-Lumlnous Light Sources 33 Figure 16. Schematic View of l-Watt(e) RTG Featuring Krypton-85 Heat Source 38 Figure 17. Schematic View of 40-Milllwatt(e) RTG Featuring Kr3T)ton-85 Heat Source 40 Figure 18. Disc-Shaped Thermoelectric Module Concept Featuring Thin-Film Thermoelements 41 Figure 19. Quantity of Cobalt-60 That can be Afforded for Different Treatment Costs for a 1-MGD Treatment Plant 63 FINAL REPORT

on AN ASSESSMENT OF THE POTENTIALLY BENEFICUL USES OF KRYPTON-85

to

ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION

from

BATTELLE Columbus Laboratories

Prepared by

Philip E. Eggers and William E. Gawthrop

June 30. 197S

INTRODUCTION

This report presents the results of a study aimed at assessing the potentially beneficial uses of krjT)ton-85 derived from waste of gases of nuclear fuel reprocessing facilities. In this study the authors have attempted to identify candidate applications for krypton-85, assess the candidate applications (technically and economically) and point out which applications have been or could be readily implemented.

Not only was the literature surveyed (1964 to present) but many persons in government, industry, and the academic community were also interviewed during the course of this study. The literature provided many of the historical data relative to krypton-85 and the nuclear Industry in general while the interviews provided very up-to- date information as to the present trends in krypton-85 uses, research, and development now going on. The interviews also provided valuable insight into new concepts for applications. While the technical assessments of the identified candidate applications were readily accomplished, the economic assessment that was attempted was not so successful. The problem of indefinite cost data for enriched krypton-85 made the economics assessment very difficult if not Impossible. Nevertheless, the authors have attempted, at least, to give order-of-magnltude estimates. 2

Sm^lARY

A study of the potentially beneficial uses of by-product krypton-85 from nuclear fuel reprocessing facilities has been accomplished. The main objective of the study was to assess the potentially beneficial uses of kr3T)ton-85 by systematically identifying and evaluating candidate uses of the fission product gas in terms of technical and economic cost benefits. Major emphasis in the study was geared not only toward identifying poten­ tially beneficial uses but also toward identifying applications where large quantities of krypton-85 could be utilized. Furthermore, emphasis was placed upon those applications where a number of devices using krypton-85 could be realized (and not on a single device that would require the total available inventory of the gas).

The overall program approach was accomplished In a project comprising four principal tasks: (1) characterization of the krypton-85, (2) identification of candidate applications, (3) technical assessments of the candidate applications, and (4) summary of the findings. The program was initiated by conducting a survey of the available literature relative to krypton-85 properties, availability, separation and enrichment, and identified applications. In addition, the literature survey also Included a review of the nuclear power Industry. Following the literature survey, a team of experts was given literature references, articles, and reports pertinent to their respective areas of expertise for their individual assessments. Eight application areas were addressed during the course of the study. The eight areas Included (1) self-luminous lights, (2) direct energy conversion, (3) dynamic conversion, (4) polymerization, (5) non­ destructive testing, (6) biomedical applications, (7) waste treatment, and (8) environmental control of submerslbles. As a conclusion to the program, the Identification and assess­ ment process yielded several specific areas where kirypton-85 could be utilized. These application areas include (1) self-luminous lights, (2) direct energy conversion (using krypton-85 heat sources), (3) polymerization, (4) nondestructive testing, (5) biomedical applica- 3

tlons, and (6) waste treatment. Dynamic energy conversion, an identified candidate application at the onset of,the program, appeared to be unattractive from the standpoint of required thermal Inventory. Likewise, environmental control for submerslbles appeared equally unattractive from the same standpoint. In fact, a single application In either of these areas could consume the entire available inventory of krypton-85. Furthermore, even If one could consider a relatively small dynamic energy conversion application (,^100 watts), the cost of the krypton-85 alone would be prohibitive (estimated to be in excess of $2,000,000). Self-luminous light sources appear to represent the foremost beneficial use for krypton-85 because (1) many lights could be made from a small quantity of gas (depending on the particular lighting application a demand ranging of from 100 mllllcurles to as much as 100 curies per light), (2) the gas could be used In its unenrlched form, and (3) a considerable nimber of lights could be fabricated using In turn a large total quantity of krypton-85. The major advantage of the light sources themselves comes from the fact that they can supply a long-term (> 5 years), uninterruptable source of light, totally independent of elec­ trical power.

Direct energy conversion and polymerization applications could be ranked next in order of significance (for utilizing a large quantity of krypton-85); yet both of these applications would require enriched krypton-85. Very specific applications for krypton-85 heat sources for use in direct energy conversion applications have been identified but not yet reduced to prototypes. Several methods of utilizing krypton-85 as a source of radiation to promote certain polymerization reactions have been identified and some of these methods have already been applied.^ ^ Irradiation of thin layers appears to represent the most unique application area for utilization of krypton-85. Although the use of krypton-85 in nondestructive testing is well established and very Important, at present this application area consumes only a few thousand curies per year (at most). Krypton-85, as used in nondestructive testing, is used primarily li» sealed source configurations for gauging .applications. Other established nondestructive applications Include employment of the gas in leak testing applications and employment of the gas in a few kryptonation applications. 4

Krypton-85 used in biomedical applications comprises the fifth beneficial usage in the list. Biomedical applications, to date, have been of an experimental nature and usually one-of-a-kind in nature. It is not anticipated that biomedical applications would consume very much of the available krypton-85; nevertheless, these applications are important. Using krypton-85 as a source of dry heat and penetrating radiation is the remaining consideration for krypton-85. However, no specific process has yet been identified to utilize the gas.

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RECOMMENDATIONS

Of the total spectrum of applications that have been studied, at present only small amounts of krypton-85 are being utilized. The reason is twofold: (1) the price of the gas Is very high (2) and (2) there is only one (inefficient) enrichment facility (supplying at best 45 percent enriched kr3^ton-85). TWo other enctmiberances to the utilization of krypton-85 include (1) lack of good quantitative health physics data, and (2) lack of quantitative solubility data. Three of the four items above can be rectified through further research and development. The price of the gas will have to be lowered to realize any kind of a market for the krypton-85. In order of Importance, the authors recommend the following additional research and development In support of the overall study on the potentially beneficial uses of krypton-85: (1) development of an enrichment process which would be more efficient than the present thermal diffusion process (at Hollfleld National Laboratory), (2) assessment of the biophysical hazards associated with krypton-85 (an experimental study), and (3) assessment of the solubility of krjrpton in various inorganic and organic media. Furthermore, it is recommended that the decay product, rubldlum-85, be studied from a materials compatibility standpoint In order to assess the reliability of krypton-85 containers.

BACKGROUND AND CHARACTERISTICS OF KRYPTON-85

Properties. Collection, and Enrichment

The physical properties of the fission product gas krypton-85 are given in Appendix A. Krypton-85 is generated as a "waste product" of reactor fuel burn-up and can be recovered along with the other noble gas fission products via collection from the fuel/cladding dissolution off- gas stream in a spent fuel reprocessing plant. It is estimated that in the 1980's all krypton effluent from reprocessing plants will have to be held up and stored for environmental reasons. Thus, krypton should be more readily available for various applications in the future. 6

There are a nimiber of processes for separating each of the noble gases from the off-gas stream. Of these processes two separation methods seem to be most promising: fluorocarbon extraction and cryogenic distilla­ tion. The absorption process has been tested on the pilot plant scale while the cryogenic distillation process has been successfully applied (3 4) in actual operations. ' "^ Each processing method has the capability of recovering 99 percent of the gases. Fission product krypton, as separated from the other fission product gases, consists (depending on the reactor operating conditions and the fuel composition and age) mainly of four isotopes: mass 86, /w50 percent, mass 85, .^4 percent, mass 84, ^^30 percent, mass 83, ,^14 percent, followed by trace quantities of masses 80 and 78. Although the krypton-85 can be employed in several applications in this dilute (unenrlched) form, an enrichment process is necessarily required to Increase the quantity of krypton-85 in the Isotopic mixture for many applications. There are four major considerations for enrichment processes: (1) Calutron, (2) thermal diffusion, (3) plasma centrifuge, and (4) laser. A method for electromagnetic separation (the Calutron) of krypton-85 has been described in Reference 5. ' The method consists of trapping the energlc particles in the lattice of a moving foil. Although the process can yield enrichments for krypton-85 in excess of 50 percent, the Calutron can work only with relatively small quantities of the gas and, thus, is not suitable for enriching large amounts of krypton-85. The thermal diffusion process for enriching krypton-85 is the only "production" process now suitable for processing large amounts of krypton. As described in Reference 6, the thermal diffusion apparatus consists of coeixial colimms each with an inner hot wall and an outer cold wall. In each coltimn the hot wall is separated from the cold wall by a small distance and the column is arranged in a vertical attitude. The countercurrent phases consist of an upward-moving layer of hot gas rising along the hot wall and a downwaird-movlng layer of cold gas falling along the cold wall. While normal convection keeps these currents moving continuously in opposite directions, the thermal diffusion creates a | 7

small tendency for the lighter molecules to drift toward the hot region where they are carried upward while at the same time the heavier molecules drift toward the cold region where they are carried toward the cold end. The small separation effect is amplified by the countercurrent flow, effecting a "large" enrichment which Is realized in the vertical plane. ^ ^ The thermal diffusion method thus described is at least a working method, but because it depends upon the mass ratio for achieving enrichment, the process is quite an Inefficient one for the enrichment of krypton-85. The plasma centrifuge method, although not fully developed, appears to be at least as good if not better than the thermal diffusion method. A nimiber of investigators have studied the process. ^ " -' The plasma centrifuge works on the principle of separating by mass difference. In one concept of a plasma centrifuge a "toronado" of rapidly spinning gases (rotating 5 x 10^ meters/sec) forces molecules of highest mass to the outside diameter of the centrifuge where they could be drawn off. Thus, in a two-stage centrifuge configuration krypton-86 could first be removed from the gas followed by removal of the krypton-85. Although a great deal of experimentation Is needed to prove the device's capability, it at least appears to be an attractive, near- term alternative to the thermal diffusion process. The laser separation method appears to offer the most promise as an efficient method of enrichment for krypton-85. Hie reason is that the laser can be tuned to specific excitation lines unique to the isotope krypton-85. However, although considerable research in laser separation techniques^ ^^, no one has reported on a laser separation technique for the enrichment of kr3T)ton-85. The main reason for no work in the area of transparent gaseous enrichment (such as for krypton-85) is that there are no tunable lasers available that operate in the short-wave­ length ("hard" ultraviolet) region, a necessary requirement for enrichment of transparent species. 8

Output by the Nuclear Power Industry

Several references '>"''' provide insight into the future growth of the nuclear power industry. Although the industry's real as well as projected output is constantly changing, at least a rough estimate of the fission product output can be shown. In terms of the anticipated fission product output, krypton-85 production can also be estimated and is, therefore, presented in Figure 1. Data for the graph in Figure 1 come from Reference 24. As one can clearly see, a significant Inventory of krypton-85 will be available even in the near future. Appendix B provides further background data relative to the nuclear power Industry in general.

TECHNICAL ASSESSMENTS

Eight general application areas were addressed in assessing the potentially beneficial uses for krypton-85. The assessments of each of the individual areas are presented below. The assessments were made keeping in mind applications which utilize the unique properties of kr3rpton-85. Furthermore, attention was given to those uses whereby large quantities of the fission product could be employed.

Self-Lumlnous Light Sources

The use of nuclear radiation exciting of luminescent materials to produce visible light has been known for many years. The principle consists of beta particles (electrons) from the nuclear radiation course striking and exciting a phosphor causing light to be emitted from the phosphor. The color of the emitted light is dependent upon the particular phosphor being used while the brightness of the light is dependent upon the quantity and strength of the nuclear radiation source.

( 3.0 —

2.5 —

M O X 2.0 — o vo 3 •o •

0.5

FIGURE 1. PROJECTED CUMULATIVE AVAILABILITY OF KRYPTON FROM LIGHT WATER REACTORS 10

Self-luminous light sources using nuclear radiation (B) to excite phosphors has particular appeal for such lighting applications as safety lighting and continuous markering devices. This appeal derives from several strong advantages over conventional sources of light. The advantages include:

(1) A light source that is fully self-contained, i.e., no external power or hookup required (2) A continuous source of light which provides a uniform output over an extended period of time (years) (3) A maintenance-free source of light that will not "bum out" (4) A light source which can be used effectively over a wide temperature range (nominally -100 F to +150 F) (5) A light source which is uneffected by humidity (6) A light source free of spark and (electrical) shock hazard.

Two disadvantages are also associated with the self-lvimlnous light sources:

(1) A light source which must be licensed by the Nuclear Regulatory Commission (because it contains radioactive material) (2) A light source which is priniarily useful in darkness (not effective in daylight).

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Today several domestic and foreign conq>anles manufacture self- luminous light sources. Most familiar are the radium (which requires charging by a light source) and low-intensity tritium lights on watch dials and instrument panels. Some of these companies also produce self- luminous light sources of higher power including those using krypton-85 as the ^-radiation source. Krypton-85 is a particularly good source of beta particles without 8S a large gamma energy component (<0.5 percent of total emissions from Kr are y). Krypton-85's relatively long half-life and inertness also make it an attractive candidate for lighting applications. Table 1 gives some comparisons between krypton-85 (^^Kr), tritium (%), and promethium-147 (1^7pni) isotopes which can be used in self-luminous sources.* It can be seen from Table 1 that krypton-85 far surpasses the other two in its ability to excite phosphors. Shown in Table 2 is a list of luminescing qualities of various common-known sources of light. It can be seen, then, from this table that krypton-85 can be used not only in applications for self-luminous indicator- type lights but also for area illumination as well, in fact, at least one domestic supplier is now producing krypton-85 powered light sources (mainly for indicator-type applications). Figures 2, 3, and 4 present data that are presented in product literature of American Atomics Corporation, Tucson, Arizona. Comparing the brightness to the quantity and then to the activity levels one can get an idea of the relative biological exposure that can be expected from a given krypton-85 self-luminous light source. Also, for applications where llltmilnatlon Is the prime concern, the number of light sources that could be deployed to accoiiq>llsh the necessary llltimination will be limited by the ability to shield (biological) the respective krypton- 85 sources.

* From product literature of American Atomics Corporation, Tucson, Arizona. 12

TABLE 1. COMPARATIVE PROPERTIES OF THREE RADIOISOTOPES USED FOR SELF-LUMINOUS LIGHTING APPLICATIONS

8\r h l^^Pm

Half-life, year 10.75 12.3 2.6

Common physical form Gas Gas or solid Solid

Maximum brightness, 12 2.5 2.5 foot-lamberts (green phosphor)

Quantity of material 1 mc 50 mc 2 mc required to produce a brightness of 0.1 foot-lambert (green) 13

TABLE 2. COMPARISONS OF SOME COMMON LEVELS OF BRIGHTNESS

Foot- Source Lamberts

Moon (as observed from earth) 750^^ > Candle flame 2880^°' Fluorescent lamp (20W, T12) November football field 50* > Page brightness for reading fine print lO*) Highlights, 35-millimeter movie 40-) Radioisotope powered self-luminous source 'Dollar' variety 'Night Light' 1- 6^'^ Television screen (average) 88'"

(a) American Institute of Physics Handbook. 2nd Edition.

(b) Reference data for Radio Engineers .

(c) Product literature from American Atomics Corp., Tucson, Arizona.

(d) Estimation by author.

(e) Determined by author from data presented by Sliney and Freasier, "Evaluation of Optical Radiation Hazards", Applied Optics, Vol. 12, No. 1, January 1973. 14

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FIGURE 3. INCREASE IN MAXIMUM VISIBLE DISTANCE BY OPTICALLY INCREASING THE DIAMETER OF SOURCE 16

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FIGURE 4. BARE SOURCE RADIATION PROFILES AS A FUNCTION OF BRIGHTNESS

( 17

Although the magnitude of the krypton-85 self-luminous light source market is very small in terms of total profits, the market could be quite large if the price of the gas were not so high. If the price of the gas could be lowered many applications could be undoubtedly implemented. Table 3 lists some of these applications.

TABLE 3. CANDIDATE APPLICATIONS FOR KRYPTON-85 SELF-LUMINOUS LIGHTS

• Airport runway and taxlway delineation • Pier markers • Barge markers • Exit signs and corridor 'direction' markers • Underground mines, passageway markers • Underground mines, area illumination • Inland waterway buoys • Air-navigational visual aids • Heliport markers • Shipboard safety lights 18

The singular most important advantage of using krypton-85 as the source of radiation is its abundance of beta radiation (it has the capability of producing four times more light than tritium). Krypton-85 is also an inert gas which means that should the integrity of the light source ever be broken the gas will not chemically combine with anything. (The most notable disadvantage of krypton-85 is a gamma energy component in its total radiation spectrum.) The gamma energy, even though it accounts for only about 0.5 percent of the total radiation, must be shielded (using a dense media such as lead) to provide necessary biological protection for personnel in the vicinity of the light. Having the background well in mind, one can then conceive of a variety of lighting applications for which krypton-85 self-luminous light sources are particularly unique. Modifications of two distinct configura­ tion types are discussed and illustrated below. The two distinct types are (1) a "direct" radiating type (flat pan) as shown in Figure 5, and (2) a reflecting type self-luminous light as shown in Figure 6. Based on these two configuration concepts, then, are a number of applications as discussed below.

Lights for Underground Mines

Krypton-85-powered, self-luminous light sources can conceivably be employed for two distinct safety applications: (1) delineation and (2) area illumination. Lights for both applications would best be installed in passageways and in coal mines where it is particularly dangerous to "string" electric lights. In fact, there are no such delineation or area illumination lights now being employed for either of these purposes in underground coal mines. Krypton-85-powered, self-luminous lights used in delineation applications could provide guidance to miners caught in passageways without a functioning cap light. Or, the delineation lights could be used to complement the cap light. Certainly, it would be advantageous for the miner to know which way the passageway bends or where the passageway roof is in front of him.

( 19

Krypton-85 gas between glass plate & ZnS phosphor-

Gloss

Cu or

Steel pan

FIGURE 5. FLAT PAN KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE 20

Steel canister

-Glass seal (front face)

Concave reflecting surface

Krypton-85 gas

ZnS phosphor

Gloss Seoled source-

FIGURE 6. REFLECTOR - TYPE KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE 21

The delineation devices could be quite small and yet quite effective. An envisioned concept is shown in Figure 7. Note that although tjrpically the lights would be securely affixed to the passageway walls and/or roof, they could be moved to new locations by simply unfastening and then remounting at the new location. Note also that since no electrical hookup is required, the delineation lights could be considered portable devices. With regard to safety, one could consider these delineation lights as not much of a hazard. Certainly, in their normal mode of opera­ tion they are completely contained, emitting little if any radiation outside of their respective enclosures. Indeed, the worst possible hazard would involve their deliberate destruction, in which case the gas (typically less than 200 millicuries) would be released to the atmosphere. But even if the gas were released, the rate of air flowing through a passageway is typically quite large and would be effective in removing any gas. Above all, if a person were to inhale the krypton-85 he would most likely not retain any of it in his system since it is inert. Several programs have, in fact, addressed the subject of inhalation of kr3rpton-85 and have shown that it is not particularly harmful. The low-level-illumination applications for illuminating areas of the passageways using krypton-85 would involve light sources of relatively higher intensity and of larger fluorescing areas. A concept for a low-level illimiinating source using krypton-85 is shown in Figure 8. The particularly beneficial use of the krypton-85 light source is that it actually illuminates the passageway floor. The miner, therefore, would be aided then in knowing what was on the floor since his cap light could not possibly illuminate everything that he needed to see such as cables, rails, or other obstacles, to get to where he was going. The same hazards that are associated with the delineation lights are also associated with the area illumination lights, namely, the accidental release of the kr37pton-85 gas. In the case of the area illumination lights, however, the output of gas per light is much greater (more than 2 curies per light). Nevertheless, the implementation of such a self-luminous lighting system could provide much needed safety illumination (where none now exists). 22

Krypton-85 Self-Luminous Light

FIGURE 7. CONCEPT FOR KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE USED AS A DELINEATION DEVICE IN UNDERGROUND MINES (PASSAGEWAY CROSS-SECTIONAL VIEW SHOWN ABOVE) 23

Stringer Containing the Lights

FIGURE 8. CONCEPT FOR KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE USED AS A FORM OF LOW-LEVEL AREA ILLUMINATION 24

Lights for Inland Waterways

Krypton-85 used in self-luminous.light sources for various inland waterway lighting applications can also be envisioned. For these applica­ tions the advantages of long-life, constant light, and maintenance-free sources all appear to show krypton-85 self-luminous lights as attractive and unique. Specific applications include barge markers, pier and obstacle markers, and buoys. All of the applications mentioned above can be envisioned as using rather high-intensity light sources and, hence, sources containing several curies of krj^ton-85. Thus, the configured systems will necessarily have to be heavily shielded (biological) krypton-85 light sources with light pipes used to actually transmit the light to the environ­ ment. A concept for such a shielded source in a buoy (channel marker) is shown in Figure 9. A modification of the buoy-light concept is shown in Figure 10 where it is envisioned that a shielded source could be used as a marker on a river barge. Likewise, a pier marker could be configured as conceptual in Figure 11. For all of these envisioned applications, krypton-85-powered, self-luminous lights are useful primarily in night lighting conditions.

Lights for Airport Visual Aids

Another application area for kr3T)ton-85 self-luminous lights is for visual aids for airports. These visual aids could include taxiway delineation, runway delineation, runway distance markers, and miscellaneous safety lights. Indeed, a runway distance marker has already been demonstrated by American Atomics Corporation, Tucson, Arizona. A sketch (made from a photograph supplied by American Atomics Corporation) of the runway marker is shown in Figure 12. A potentially useful airport visual aid is a runway delineation device such as that shown in Figure 13. The unique advantage of a constant light source (requiring no external electrical hookup) makes the concept shown in Figure 13 particularly unique, especially in remote areas such as Arctic regions where electrical power interruptions might be more frequent 25

Light Pipe

Low-Density Foam Filler

Biological Shielding

Krypton-85 Gas

Phosphor

Buoy Outer Skin

Light Source Support

FIGURE 9. CONCEPT FOR HIGH-INTENSITY KRYPTON-85 SELF-LUMINOUS LIGHT USED IN A BUOY 26

Light Pipe

Biological Shielding

Gas-Tight Seal Krypton-85 Gas Phosphor on Bottom of Canister

FIGURE 10. CONCEPT FOR A KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE USED AS A BARGE MARKER 27

Light Source Recessed in the Pier

FIGURE 11. CONCEPT FOR A KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE USED AS A PIER MARKER > 28

^^i- ^^^^^mm^22:i:!2222l222122l^^^^^^^...,^^

i^.T't-^

^J*" -,/> -I

L,tUl

Marker Containing a Series of Small Krypton-85 Self- Luminous Lights

FIGURE 12. SKETCH OF A KRYPTON-85 RUNWAY MARKER FROM A PHOTOGRAPH SUPPLIED BY PERMISSION OF AMERICAN ATOMICS CORPORATION, TUCSON, ARIZONA 29

Light Pipe With Light Source Below (Similar to Configuration Shown in Figure 4)

Plowed Snow Lights ^,->^'

Runway Plowed Snow

'A X-.

/ / /

FIGURE 13. CONCEPT FOR KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE USED FOR RUNWAY DELINEATION 30

and especially where snow pileup would render ground-mounted lights useless. The single, most important advantage that can be realized from the krypton-85 self-luminous lights used in visual aids applica­ tions is that these lights provide a constant, long lifetime, uninterrupted source of light (a very critical detail when one considers the possibility of the lights going out when an aircraft is in the process of landing).

Other Lighting Concepts

There are many other possibilities for lighting using krypton-85 self-luminous light sources. These applications are lumped together here under a miscellaneous category and include such diverse devices as (1) beacons for towers, (2) highway traffic signs, (3) shipboard safety lights, and (4) building corridor (safety) delineation. Beacons (not approved navigational aids) utilizing krypton-85 self-luminous lights are certainly possible to consider, yet probably impractical because of the very large amount of krypton-85 gas (greater than 1,000 curies) that would be necessary. The large amount of gas introduces two problems: (1) a high gamma radiation profile about the source, and (2) a high rate of phosphor degradation. The gaimna radiation could be shielded against, but the phosphor damage would present the ultimate limit on the light (there is very little that can be done to prevent or retard the damage, and still maintain an all-effective, high-intensity source of light), Krypton-85 self-luminous lights could not be used for Federal Aviation Administration navigation systems because the self-luminous lights do not have the required output (minimum output equivalent to a 116 watts). At least one highway traffic sign has been installed which used krypton-85 self-luminous lights. This specific sign enjoyed only marginal success, however, due to the fact that there were many high-intensity electric lights in the vicinity of the krypton-85 light. It is envisioned that many other candidate highway signs illuminated with self-luminous sources would also experience the same fate as the demonstrator. Both shipboard safety lighting and building corridor (delineation) safety lights could very well be considered possible candidate applications 31 for krypton-85 self-luminous lights. Configurations similar to those shown in Figures 7 and 8 for the mining applications could be tailored for shipboard as well as building corridor applications. The greatest advantage for the self-luminous sources is that they provide a constant, long-term source of light.

Military Applications

Krypton-85 self-luminous lights could be envisioned for the following specific military-oriented applications: (1) light marker for missile guidance reference, (2) light beam (breaker) intrusion detection, (3) markers for air-dropped sensors, (4) remotely deployable aircraft landing reference (marker), and (5) safety lighting for bunkers and silos. Several light markers for missile guidance references have, in fact, already been built and installed for the United States Air Force by f28^ American Atomics Corporation. On the subject of light sources for physical security systems, krypton-85 self-luminous light sources could be envisioned for use in light- beam breaker applications such as the one shown in Figure 14. The unique advantage of the light source is that it requires no external power, and hence, no electrical hookup or battery supplies. Even though battery supplies for equivalent electric load capacities can be designed to operate up to a year, these battery supplies are very sensitive to temperature and humidity. Therefore, another great advantage for the krypton-85 self- luminous lights is that they can operate over a temperature range of, nominally, -100 F to + 150 F with no sensitivity to humidity. Various adaptations of the system shown in Figure 14 could also be envisioned in a portable configuration such as might be deployed by a group of men, a configuration such as that shown in Figure 15. 32

100 meters

Krypton-85 Self-Lumlnous Light

DetectoT:/Transmitter

FIGURE 14. CONCEPT FOR A FIXED-INSTALLATION PHYSICAL PERIMETER SECURITY SYSTEM USING A KRYPTON-85 SELF-LUMINOUS LIGHT SOURCE 33

100 meters

Self-Luminous Light Source

De t ec tor/Trails mi tter

FIGURE 15. CONCEPT FOR A FIELD-INSTALLATION PHYSICAL PERIMETER SECURITY SYSTEM USING KRYPTON-85 SELF-LUMINOUS LIGHT SOURCES 34

Conclusions

In conclusion, there are many applications for self-luminous light sources including those powered by the fission product gas, krypton-85. In terms of safety lighting, the krypton-85 self-limiinous lights can provide an uninterruptible, constant intensity, explosion-free, long-term source of light, a claim that cannot be made for conventional electric lights. In terms of runway delineation and other airport visual aids, the advantage of the uninterruptible light source again appears along with the virtually maintenance-free aspects of the self-luminous light. Finally, one must remember that there is, of course, no hookup of wiring for any of the self-luminous lights (since no external power source is required) making the installation of these self-luminous light sources quite an easy task.

Technical Assessment of Radioisotope Thermoelectric Generators Involving Krvpton-85 Heat Sources

Introduction

The design, development, and fabrication of thermoelectric generators for terrestrial, space, and undersea applications have been well documented over the past 15 years both in the United States and abroad. Early thermoelectric generators ranged in electrical output power from several watts to more than 100 watts. Applications included auxiliary power for spacecraft (satellite) instruments and transmitters/ receivers, ocean buoy% remote weather stations, detection systems, and portable auxiliary power for military applications. In more recent years, the advent of microelectronics has greatly reduced power requirements and has placed demands for smaller thermoelectric generators—down to several hundred microwatts in the case of cardiac pacemakers. Surveillance 35 equipment, projectile fuzes, and other applications involving lifetimes of 5 years or more are also placing increasing demand for thermo­ electric generators with output powers ranging from tens of milliwatts to several watts. However, three principal areas must be addressed (beside reliability) in the design of thermoelectric generators for certain selected applications.

• Safety • Cost • Specific power (both size and weight).

The cost of RTG's has been influenced principally by the (1) cost of the encapsulated radioisotope heat source (e.g., plutonium-238 heat sources), (2) associated design, analysis, and testing of RTG safety features, and (3) thermoelectric convertor design and fabrication. One explanation for the high cost of RTG's has been the lack of standardization in RTG design and fabrication—each new application has t3^ically involved the development of a totally new concept and configuration, often involving a new feunlly of thermoelectric materials. Also, few RTG applications to date (aside from pacemakers) have involved more than tens of units of a given design. The third area in RTG design is that of specific power—both in terms of kilograms/watt and cvcr/vatt. The relatively high thermal power density and minimal shielding requirements of plutonium-238 make it a particularly attractive choice of fuel form. Again, the question of safety in the event of accidental release of plutonium places demands on the radioisotope containment subsystem and restricts the use of this type of heat source in certain applications. The above three design considerations, together with the convertor reliability, must thus be traded off in a given application in order to 36 satisfy all of the requirements imposed. In the current study of potentially beneficial uses of krypton-85, BCL has identified the possibility of using krypton-85 as the radioisotopic heat source for selected RTG applications in which "safety" is of overriding importance. In certain selected applications, it must be assumed that the radioisotope may be released—inadvertently or intentionally. In such an event, a gaseous heat source (e.g., krypton-85) would be highly desirable since it would dissipate into the atmosphere, thus minimizing the chances of a localized radiation hazard or incident. Of course, the penalty of low power density and relatively energetic gamma radiation associated with krypton-85 must be paid in the form of a heavier RTG than would be possible with a plutonlum-fueled RTG. In the discussion which follows, two concepts for krypton-85-fueled RTG's are described—one having an output power of 1 watt(e) and involving a conventional discrete-element thermoelectric converter and a second concept featuring an output power of 0.04 watt(e) and involving a thin-film thermoelectric convertor design.

Description of Selected RTG Concepts

Two design requirements were considered in this conceptual study— pressure containment of the heat source vessels and shielding to reduce surface dose rates to less than 200 mRem/hr. The assumptions made in this conceptual study included

• RTG surface dose rates < 200 mRem/hr • Output power = 1.0 watt(e) and 0.040 watt (e) • Total RTG conversion efficiency =2.5 percent (discrete elements converter) and 2.0 percent (thin-film converters) • Hot-junction temperature = 475 K (202 C) • Cold-junction temperature =325 K (52 C)

( 37

• 50 percent enriched krypton-85 • Maximum heat source temperature 533 K (260 C) • Depleted uranium shielding with density = 18.7 g/cm • Bismuth telluride thermoelectric convertors.

Two RTG concepts have evolved using krjT)ton-85 heat sources and these are described next. In both of these concepts, a pressurized cylinder ranging in diameter from 0.635 cm (0,25 in.) to 1.27 cm (0.50 in.) is envisioned. The size of the overall heat source and the internal working pressure of the kr3rpton-85 has been selected on the basis of examining the effect of working pressure on containment wall thickness and, hence, power density of the heat source. Assuming close packing of right-circular cylinders, the power density per unit area and unit length, Q, was calculated as a function of krypton-85 operating pressure at 533 K. These analyses have indicated that working pressures of up to 6000 psi were required to achieve satisfactorily high heat source power densities.

One Watt(e) RTG. One concept for a 1-watt RTG is illustrated in Figure 16 and features the use of a multiplicity of krypton-85-filled cylinders (0.635-cm diameter x 6 cm long). These cylinders can either be individually sealed or be fabricated using a coiled length of tubing. The externally shielded concept shown in Figure 16 is a cylinder having a diametral dimension of 13.8 cm (5.4 in.) A conventional bismuth-telluride thermoelectric convertor is envisioned at two or more locations around the perimeter of the heat source, providing an output power of nominally 1 watt at 2 to 6 volts. Although relatively compact, the total weight of this con­ vertor will be less than 40 pounds.* Except for the design, fabrication, and closure of the heat source "modules", this RTG design draws on established technology. The heat source is envisioned having three separately sealed enclosures as shown in Figure 16: (1) the modular heat source cylinder, (2) the heat source container, and (3) the RTG container. Several variations on this heat source design are also envisioned. For example.

*RTG weights of 15 to 30 pounds are possible in the case of Internally shielded designs. 38

— Thermoelectric convertor e or both ends)

Modularized Kr-85 ieat source cylinders in cylindrical arraj

Heat source container (sealed)

Thermal insulatioi

RTG container (sealed

Shieldtnj

Shielding overcla

Note: Actual size, power leads not shown.

FIGURE 16. SCHEMATIC VIEW OF 1-WATT(e) RTG FEATURING KllYPTON-85 HEAT SOURCE 39 the heat source might be made by boring an array of holes in a block and diffusion bonding a "header" plate on one end. This approach would offer simplicity since only one charging port would be involved. Also, this approach would offer good heat transfer through the packed array of heat source "cylinders". The two-piece shielding subsystem is envisioned as shown in Figure 16 in order to readily facilitate Insertion and removal of the RTG unit. This is an important consideration since the RTG unit will have to be handled remotely once the krypton-85 is introduced.

Forty~Jlilliwatt(e) RTG. A 40-mllllwatt(e) RTG concept is illustrated in Figure 17 and features the use of a singular cylindrical heat source capsule (1.3-cm diameter x 5.7 cm long). A thin-film bismuth-telluride thermoelectric convertor is envisioned comprising 5 to 8 disc-shaped modules, as illustrated in Figure 18. It is anticipated that such a thin- film thermoelectric convertor will Involve bismuth-telluride films ranging in thickness from 0.001 to 0.005 cm and providing an output power of 40 milliwatts (e) at 6 to 10 watts. A similar thin-film thermoelectric con­ vertor was recently evaluated at BCL for the U.S. Air Force for f29') use in projectile proximity fuzes.^ ' It is noteworthy that, even though the thermal inventory in the heat source for this 40-milliwatt RTG has decreased by a factor of 20 compared with the 1-watt case, the required shield thickness has decreased by only a modest amount. Hence, the specific power of the RTG decreases as we consider RTG's with decreasing levels of output power. In the present conceptual study, it appears that the weight of the overall shielded 40-milliwatt(e) RTG . will range from 8 to 15 pounds (3.8 to 7.0 kilograms)*. The heat source is envisioned as a thick-wall cylinder con­ taining an internal pressure of about 6000 psi. This inner cylinder is encased in a sealed heat source container and, finally, the unit is sealed in the overall RTG container (see Figure 17).

*The lower weight applies to internally shielded configurations. 40

11.4 Shielding overclad

•Shielding

Thermal insulatior

Thermoelectric convertor involvir multiple disc modi

Heat source contaj

Unit Krypton-85 heat source cylinc

RTG Container

Note: All dimensions in centimeters, power leads not shown

FIGURE 17. SCHEMATIC MIW OF 40 MILLIWATT (e) RTG FEATURING KRYPTON-85 HEAT SOURCE Hot Straps for Heat Collection

_ Substrate --,

Hot Junction s Thermoelectric (Aero Heating / Elements Occurs Here)

Note: All units in inches.

FIGURE 18. DISC-SHAPED THERMOELECTRIC MODULE CONCEPT FEATURING THIN-FILM THERMOELEMENTS 42

One possible design trade-off that may lead to reduced overall system weight involves internal versus external shielding. In both example concepts discussed in this report, the external shielding approach was assumed. However, it is possible to move the shielding closer to the krypton-85 heat source (i.e., internal shielding approach), thereby reducing the shield weight based solely on geometrical considerations. The required shield thickness will of course Increase as we move the shielding closer to the radiation source. Nevertheless, this trade-off will lead to substantial weight reductions, particularly in the case of the 1-watt(e) RTG.

Potential Benefits of Krypton-85 RTG's

Based on the conceptual studies to date, it appears that krypton-85- powered RTG's offer several advantages over conventional solid radioisotope fuel forms:

• Minimize hazards associated with accidents which lead to the release of the heat source • Minimize the chances of "detection" in the event that heat source is purposely or unknowingly opened • Krypton-85's half-life of 10.7 years provides for useful RTG lifetimes of greater than 5 years.

Potential Limitations of Krypton-85 RTG's

The foregoing conceptual studies have, however, indicated several potential problem areas or limitations associated with the use of krypton-85 heat sources:

• Require relatively heavy shielding • Require operation at relatively high pressures involving highly enriched krypton-85 sources • Limit the specific power of the RTG, particularly at low levels of output power. 43

Conclusions

Preliminary findings during the program are:

• Use of kr}rpton-85 in compact, low-power RTG's requires high containment pressures (2000 to 7000 psi) and/or high krypton-85 enrichment levels (25 to 50 percent). • Specific weight (lb/watt) of shielded krypton-85 heat sources favors the use of internally shielded con­ figurations (inside thermoelectric convertor and insulation) • Specific weight (lb/watt) of shielded krypton-85 heat source decreases significantly with increasing thermal inventory. • Overall weight of 0.04 watt(e) RTG powered by krypton-85 ranges from 4 to 8 pounds (internally shielded). • Overall weight of 1.0 watt(e) RTG powered by krypton-85 ranges from 15 to 30 pounds (internally shielded). • Multiple-tube bundle heat source configuration -minimizes hazards associated with failure of single pressure vessel; the penalty in this design is the increased size and weight of the heat source.

The conceptual studies accomplished in this program have not attempted to fully optimize the design but rather to present generalized design con­ figurations. Therefore, given these generalized design criteria and given a specific application, a more detailed design trade-off effort can be performed in order to arrive at a more optimum RTG configuration (from the standpoint of weight, size, and "safety"). Finally, there appears to be at least two noteworthy incentives for developing kr3^ton-85 RTG's. One incentive follows from the need for an alternative to storage battery systems (in long-term missions, 5 years or more) for deployment in critical locations. A second incentive derives from the fact that krypton-85 is projected to be available in increasing quantities towards the end of the decade^ reaching hundreds of kilowatts (thermal) by the mid-1980's due to anticipated krypton recovery from the increasing nimiber of operating nuclear reactors and the reprocessing of their associated fuels. 44

Dynamic Energy Conversion Systems

Because of the high cost per thermal watt of krypton-85, practical applications for dynamic energy-conversion systems will be limited to those not presently served effectively by fossil fuels or central electric power. One thermal watt of kr3^ton-85, if converted at an overall efficiency of 0.25, will produce a total power output of about 16.4 kwh in 10 years, worth about 50 cents at a rate of $0.03/kwh. While the cost of 1 watt, . . of krypton-85 is indefinite at this time, it is likely to be several thousands of dollars. Accordingly, only applications having one or more of the following characteristics can be envisioned:

(1) Long-term unattended operation, i.e., no refueling or recharging (2) No exhaust/low signature (3) Implantability.

Such applications cannot be served by conventional fossil-fueled power plants. Table 4 gives a list of potential applications for dynamic energy conversion systems using krypton-85 as the heat source. Biomedical applica­ tions are missing from this list because of the heavy shielding requirements. Considering probable future inventories of krypton-85, applications in the range of 10 to 100 watts are of greatest interest. Input thermal power for this output level is likely to range from 40 to 1000 watts. As shown in Table 5, for most of the applications listed, there are some require­ ments in the 10 to 100-watt range. In general, dynamic systems will have an efficiency advantage over direct conversion systems, such as thermoelectric generators. Dynamic system overall efficiencies may range from 0.1 to 0.4, depending upon the size and type of converter. However, the dynamic systems will, in general, be more complex than the direct system.

( 45

TABLE 4. DYNAMIC ENERGY CONVERSION SYSTEM APPLICATIONS

Application Output Power Level

(1) Undersea, deep submergence (a) propulsion 10 kw and up (b) electrical power 2 w and up

(2) Aerospace, electrical power 100 w and up

(3) Remote area/marine . .^n 1 W - lUU w (a) navigational beacons (b) weather telemetry (c) comaiunications relays (4) Long-shelf-life emergency power 1.5 kw and up

(5) Military applications (a) low-signature propulsion 50 kw and up (b) low-signature surveillance 1 w and up 46

Item 5 of Table 4, low-signature military applications, was listed because of the possible strategic advantage over a conventional exhaust-producing propulsion system, which has a thermal and chemical signature. However, the krjT>ton-85 power plant would not be completely without signature, there being waste-heat rejection from the system radiator at temperatures up to 100 C. The krypton-85 d5mamic system would also be free of combustion noise, but would not be as quiet as a direct energy-conversion system.

Brayton-Cycle Systems

Brayton-cycle energy conversion systems are well suited to a variety of applications ranging from 10 kw to over 50 mw; applications in this size range are generally well beyond what can be considered practical for krypton-85 heat-source applications. Brayton-cycle systems can be designed for lower outputs, but with some loss in efficiency. Tip speed is an important parameter in the design of Brayton- cycle turbomachinery; for low power levels, the wheel diameters are necessarily small, requiring high rotative speed to maintain tip velocity. Thus, at some extreme low power level, wheel diameters become too small and rotative speeds become too high to be practical. Small turbomachines generally suffer from a high ratio of tip clearance to blade height which leads to excessive leakage and low efficiency. Nevertheless, Brayton systems have been designed for as low as 0.5-kw output. Reference 30 describes such a system for a plutonium-238 heat source, which operates at 48,000 rmp with low working fluid pressures (4.2 psia compressor inlet, 7.7 psia discharge). The working fluid for this closed-cycle unit is a mixture of xenon and helium having a molecular weight of 60. The estimated cycle efficiency of this unit is 0.156 compared to about 0.3 for larger units using radioisotope heat sources.

i 47

An interesting feature of the Brayton-cycle system in this instance is the fact that krypton could be used as the working fluid; Reference 31 describes experiments with closed-cycle Brayton units operating with krypton. Alternatively, a Kr-He mixture could be used advantageously, as are Xe-He mixtures. With some mixture of krypton-85 as the working fluid, no heat exchanger would be needed to transfer heat to the working fluid; rathei^ a fluid reservoir placed between compressor discharge and turbine inlet would seirve to heat the fluid. Residence time of the fluid within the Brayton rotating unit is sufficiently small that heat release within the engine would be negligible. Unfortunately, the required volume of the krypton reservoir would be large and not worthy of consideration because of the limited supply of the gas. Assuming 0.5 kw(e) output and 3.2 kw(th) input (as for the system described in Reference 1), an inventory of about 5.2 kg of krypton-85 would be needed. At the 0.53 atm turbine discharge pressure, a reservoir 3 volume of 23.6 m would be required with 45 percent enriched krypton-85. The turbine could be designed to operate at a higher discharge pressure with an attendant increase in rotative speed and possibly a decrease in efficiency. Alternatively, the krypton-85 could be stored in an array of pressurized tubes which form an effective configuration for heat transfer to the working fluid, which presumably would not be krjrpton. The Brayton-cycle units would offer good potential for high efficiency and long unattended service life, and would be the preferred choice for most applications above 3 kw; it would be usable in applications as small as 0.5 kw.

Stirling-Cycle Engines

Stirling engines can be built for power levels ranging from a few watts to several hundred kilowatts. Small Stirling engines have been built for biomedical applications (32,33) that developed about 5-w output with about 40-w thermal input; such units use plutonium-238 as the heat source 48 and experimental units have been run 5000 to 7000 hours without failure. As previously mentioned, krypton-85 is not a desirable heat source for biomedical applications at this power level; however, the small Stirling- engine technology developed for this application would probably be trans- ferrable to other applications. Stirling engines have a peculiar design limitation: their performance is penalized by large void volume in the heat-transfer com­ ponents of the engine. Since the krjrpton-85 heat source could be en- capsuled in tubes of any configuration, a great deal of flexibility in heater design is afforded, and some operational benefits could result. Krypton-85 would not be desirable as a Stirling-engine working fluid, as low-molecular-weight fluids such as hydrogen or helium are found to be most advantageous.

Rankine-Cycle Engines

Rankine-cycle engines can be built either with piston expanders or turbine expanders. The Rankine turbine has size limitations analogous to those of the Brayton turbine, although Reference 34 describes a 7-watt output Rankine turbine with a 1/2-in.-diameter expander rotating at 200,000 rpm. In one form or another, the Rankine engine can be built in a virtually unlimited size range. The cycle fluid, temperatures, and pressures must, of course, be selected so that the fluid goes through phase transformations in the boiler and condenser. Water/steam is a commonly used fluid; steam units must be protected from freezing environments and the expander bearings must generally be sealed from the water—a design complication. Organic fluids can also be used; these are limited to moderate peak cycle temperatures (300 to 400 C) with correspondingly modest thermal efficiencies, but organic fluids can be selected that will not freeze in normal environments and which are miscible with lubricants (or have some lubricating properties themselves). Krypton could not be used as a Rankine-cycle working fluid at normal temperatures. 49

Rankine-cycle system boilers have no unusual design requirements that would either favor or prohibit the use of krypton-85 as a heat source. Presumably, an encapsulating tube array could be designed that would seirve well as the boiler heating surface.

Conclusions

The cost of krypton-85 per thermal watt is such that it is not competitive with applications that can be seirved by fossil fuels or, in general, by solar energy including solar cell arrays for aerospace applica­ tions, which can be produced for under $100/thermal watt. Competitive with other radioisotopes, the cost must be considered on a case-by-case basis. Although kr}^ton-85 is usable in a Brayton cycle engine, the minimum thermal requirements would be in the 500-watt to 1-kilowatt class and this is a rather impractical consideration (either from a cost or quantity basis).

Polymerization

Much work has been done in the past 20 years on the use of radiation (cy, 3, y* ^'"^^ neutron) to polymerize vinyl monomers and modify (cross-link, graft) performed polymers. Most of the research reported in the literature has centered on cobalt-60 y irradiation. Commercial applications have been relatively few but several important industrial processes have resulted. These include the use of cobalt-60 y irradiation for the preparation of methyl iodide, for the manufacture of polymer impregnated (in situ polymerization of methyl methacrylate) hardwood parquet flooring, and for some specialty polymer grafting and cross-linking reactions. Electron beam curing of polyethylene wire and cable jacketing, indoor and outdoor wood paneling (principally polyester impregnated), and solvent-free liquid polymer coatings are also commercial realities. 50

Both cobalt-60 y and electron beam 3 Irradiation are capital- intensive radiation tools. Gamma irradiation is highly penetrating and requires extensive shielding but allows curing reactions to be carried out through thick cross sections. Beta irradiation requires sophisticated and expensive equipment but is nevertheless a good tool for curing or hardening surface layers or thin cross sections, such as wire jacketing. Ganna and beta irradiation in general are capable of relatively rapid or efficient polymerization or cross-linking reactions without requiring the use of precious heat energy or contaminating organic peroxides. A potentially useful source of P irradiation that has received (35) almost no research attention to date is krypton-85. ^ The most unusual feature of kr3^ton-85 is, of course, the fact that it is a chemically inert gas. As such it has the following highly unique properties which should be of very practical benefit in certain specialty polymerization and polymer modification applications:

(1) Krypton-85 will uniformly fill any confined volume. (2) Krypton-85 will uniformly reach all exposed surfaces of a complex shape. This is especially important with convoluted or baffled surfaces. (3) Absorption into some surfaces to effect desirable results at controlled depths is possible. (4) As a gas, krypton-85 can be pressurized to control the effective radiation dose at surfaces. (5) Krypton-85 can be uniformly dissolved in liquids or solids to effect polymerizations throughout a reaction mixture. (6) Krypton-85 forms clathrate compounds with such chemicals as urea and can be absorbed on charcoal. Similar complexes with specially designed molecular sieves should also be possible. (These capabilities should offer unique reaction possibilities.)

These unique features of krypton-85 were used as the basis for formulating new potentially useful concepts for beneficial uses of krypton-85. 51

Conclusions

In conclusion, a number of unique applications can be envisioned for using krypton-85 to promote polymerization reactions. In-depth analysis of the unique properties of krypton-85 vis-a-vis the concepts already formulated, incorporating a wider range of polymer technology than was possible during this program, should provide many additional new concepts. At any rate it appears that krypton-85 can be utilized for polymerization, probably in its enriched form. Referring to the properties listed in the above section, one can identify specific applications as enumerated below.

Concepts Based on Property 1

(1) Use krypton-85 contained in thin-wall tubes as a fixed energy source to replace or complement UV or electron-beam sources for industrial curing processes. A material useful as a container for the krypton-85 which would allow penetration of the electrons would need to be identified. This may be a difficult goal to achieve.

(2) Polymerize gaseous monomers such as ethylene to obtain high-purity polymers for electrical applications requiring especially low dielectric loss. Property 4 would also be important in this concept.

Concepts Based on Property 2

(1) Solvent free liquid polymer coatings (UV curable paints and inks, fusible powder coatings) can be cured in normally inaccessible areas without the use of heat, UV or electron beam guns. This could be particularly important where pigmented coatings, such as automotive paints, are involved. Formulations based on commercially available UV or electron beam curable vehicles should be usable. 52

Cross link (i.e., surface barrier) or graft to the interior surfaces of hollow fibers. Such fibers are the heart of the favored designs for kidney dialysis machines and in reverse osmosis devices for desalination of seawater. Properties 3 and 4 could also play a key role in studies in this area. The key to successful dialysis in these machines is a properly structured surface layer on the dialysis membrane for rejection of such chemicals as urea or NaCl while allowing free passage of water. Carefully controlled cross linking and/or grafting reactions on the inaccessible inner surfaces of the hollow fibers is a necessity. Kr3rpton-85 offers the possibility of accomplishing desirable reactions on preformed bundles of hollow fibers, thus being a very efficient process.

Similarly, the outside of polymeric or polymer coated glass optical fibers (light pipes) could be very uniformly cross-linked or grafted. Carefully controlled refractive index increase at the surface is required for efficient light transmission. The proper modifications of the surface might be done very efficiently using krypton-85. Success­ ful modifications here could be very important in energy or information transfer applications. For example, laser transmission over long distance with controlled light energy loss is the key to optical trans­ mission systems based on this principle. Again Properties 3 and 4 could also be very important in achieving the desired surface modifications.

The surface or entire cross section of fibers traveling through a krypton-85-filled chamber could be cross linked or grafted to effect desirable changes (e.g., strength, strength at elevated temperature, reduce static charge problem, etc). This idea would appear to be applicable right at the spinnerette of a fiber-forming operation. The many multifilaments coming out could immediately enter a krypton-85 filled chaniber and could then be twisted into yam. Again Properties 3 and 4 might be applicable. 53

Concepts Based on Properties 5 and 6

(1) Krypton-85, complexed or absorbed as described in Property Number 6, should be usable as a unique, flexible radiation source when dispersed in liquid media, or as a fluidized bed. The latter idea has particular attraction as a possible way to use gaseous krypton-85 in a more controlled manner, yet possibly still making use of fluidity properties to uniformly cross link or graft onto polymer surfaces of irregularly shaped objects. 54

Nondestructive Testing

The properties of krypton-85 in the gaseous form, as well as in the kryptonates, makes the isotope well suited for several nondestructive testing applications as well as related sensing applications (that are not truly nondestructive testing). Thus faij krypton-85 in gaseous form has been (and is being) used in the following applications

• Weight gauges • Thickness gauges • Leak detection • Fluid flow tracing • Flow detection • Miscellaneous.

In kryptonate (krj^ton-impregnated materials) form, the radio­ isotope has been demonstrated effective in flow detection and thermal mapping applications. References 36 through 47 provide detailed descriptions of various nondestructive testing applications using krypton-85.

Gaufiing

Krypton-85 in the unenriched form (/^4 to 6 percent) as well as in its enriched form (up to 40 percent) is particularly well suited for weight and thickness gauges. The krypton-85 provides a uniform, stable, long-term source of 3 energy for accurate thickness and weight measure­ ments. The kr3T)ton-85 sealed source is also unaffected by extremes in temperature or humidity and, of course, is fully self-contained. Most applications involve use In manufacturing process control and make use of two classes of gauges: a transmission type and a back- scatter type. The transmission gauge uses a radioisotope sealed source and detector combination with the material to be measured (weight or thickness) running between the source and detector. Variances in the material are recorded by the variance in radiation intensity as seen by 55 the detector and the detector then sends a signal to the process equipment for appropriate action (or no action). Transmission gauging systems are typically employed in the paper, plastics, and rubber industry with sealed sources containing from 500 millicuries to a few curies of krypton-85 (per source). There are also beta energy backscatter gauges which have been reported in the literature.' ' In this configuration the reflectance of the beta energy is measured, indicating such things as surface hardness. Industry acceptance is, however, unsubstantiated. It is difficult to say just what the total consumption of krypton-85 for these gauges is, since the data is proprietary to the respective gauge vendors; however, it is probably safe to say that this particularly beneficial use of krypton-85 demands several thousand curies per year.

Leak Detection and Fluid Flow Tracing

Krypton-85 gas used as a media in leak and flow detection has seen limited use, mostly as a part of research programs. However, the electronics industry has used krypton-85 quite heavily^ ' in guaranteeing the integrity of hermetically sealed components. Cost and sensitivity are probably the most important advantages for these krypton-85 processes. The cost of the krypton-85 (unenriched) is of particular advantage as opposed to the cost of a mass spectrometer system. The sensitivity of the process (using kr3T)ton-85) is probably unparalleled. The leak detection procedure involves "soaking" a batch of com­ ponents in krypton-85 at 100 to 120 psi for 2 to 16 hours. ' During the period, the leaky components are partially filled with the kr3T)ton-85 gas. Following the pressurization, the krypton-85 gas is pumped back into a containment reservoir (for later use). The partial vacuum created during the pumping-off operation tends to clean the exteriors of the components. An intermediate helium leak detection method can then be used to reject components with larger leaks (since the pimiping-off operation will remove 56 most of the krypton-85 from components with large leaks). Finally, inspection of the components involves using a scintillation counter to screen out defective components. It is again difficult to estimate the total consumption of krypton-85 in leak detection. The process allows recovery of nearly all of the original gas, and so the particular process really requires only an Initial investment of krypton-85 gas. The use of krypton-85 as a tracer to observe fluid flow and fluid mixing has not been widely reported. This lack of literature references may be due to lack of experimentation or lack of good results. Yet there do seem to be potentially beneficial uses for the krypton-85 gas. In fluid flow measuring applications, the krypton-85 could be used to indicate choking through a network or even leaks. In fluid mixing operations, the radioisotope could be used to indicate the rate and degree of mixing as well as the location of "true" mixing within a given confluence.

Flaw Detection and Thermal Mapping

Nondestructive testing using kryptonated (krypton-impregnated materials) has received wide attention in the past.^^'»^°»^^) At least one kryptonation process is presently being used. The general process is useful in detection of material flaws. The kryptonation process involves impregnation of a given material with krypton-85. Since krypton-85 is an inert gas, its incorporation into the host material crystal lattice will not physically or chemically affect the host material. However, the gas (krypton) will be released by physical or chemical action on the host crystal lattice, thus permitting its application as a tracer atom to study various parameters affecting the crystal lattice itself. Krypton-85 can be forced into a material crystal lattice via two methods (39'): (1) ion bombardment and (2) pressurization. In general, whatever the method, all kryptonates can be characterized as having the same properties. First, they can be prepared at various levels of activity 57 with the penetration depth simply controlled via the specific experimental technique used. Second, the kryptonates are very stable with time at room temperature. Third, any process (chemical or physical) that disturbs the host material will result in some loss of activity. And last, a given fractional loss of krypton-85 in a krjrptonate occurs upon heating of the host material at constant temperature. Some disagreement exists, however, as to whether the outgassing krypton from the host material does, in fact, obey the classical diffusion laws.^ y^^6) Kryptonation techniques have been investigated for use in determining material surface conditions, i.e., wear patterns and flaw detection. The process is quite sensitive, and probably for that reason has enjoyed limited acceptance. Kryptonation of turbine blades for thermal mapping has, at least at one facility, been proven very successful. The process has been implemented to verify the conditions of materials in gas turbine power plants which have experienced overtemperature excursions. The power plant materials (the turbine blades, primarily) are subjected to krypton-85 impregnation. Following the kryptonation the materials are djmamlcally rotated and thermally stressed. This process then causes release of the krypton-85 which is, in tuim, measured via counting techniques which yields a quantitative measure of the material conditions. The reported results of the "thermal mapping" kryptonation (46 47) application * ' show that the materials exhibiting a low level of krypton-85 containment are most likely to yield short-term overtemperature indications. Sensitivity of the mapping technique can be controlled through the Impregnat ion parame ters.

Miscellaneous Applications

Krypton-85 has also been applied to various other sensing type applications. These include (1) chemical sensors for the detection of (37) (37) hydrogen , (2) gamma communications ', (3) propellant level (38) indicator , (4) a passive device for determining relative rotation, (5) an atmospheric tracer in defining puff dimensions and transport 58 speed' ', (6) a helicopter lift indicator ' \ (7) a detection method for automobile-exhaust pollutants'-(US') '' , and (8) a lightning rod. Most of these applications are one-of-a-kind or only experimental in nature; yet they are worthy of note.

Conclusions

Indeed, krypton-85 has already been identified as a very important component in a number of nondestructive testing applications. Many of these applications have been well developed, especially the sealed source gauging, while a few of the others are one-of-a-kind operations. However, as a general statement,nondestructive testing applications consume a relatively small (a few thousand curies per year) portion of the total available inventory of krypton-85. 59

Biomedical Applications

The use of radioactive gases, including krypton-85, to monitor the flow of biological fluids, has been the subject of many research investiga­ tions during the past 15 years. ~ Three conclusions can be drawn from the published literature in this technology: (1) there is a paucity of information concerning the toxicity and dosage of krypton-85 in model studies, (2) the work on monitoring biological fluids using radioactive -gases continues to be of an experimental nature, and (3) scarcity of informa­ tion concerning the consumption of krypton-85 suggests that the consumption from krypton-85 sources will only be a very minor draw upon the total supply. Nevertheless, the potentially beneficial use of (or particular lack of using) krypton is assessed below. Except for minor differences in the solubilities of krypton-85 and xenon-133, for which little or no quantitative data exist, it would seem that the xenon-133 would be the better choice of isotopes because of its much shorter half-life (22.4 hours).^ Toxicity data for krypton-85 is confined to preliminary investiga­ tions with inhaled krypton-85 in animals. It is probably because of lack of data that many more experiments have not been performed or that other chemicals and Isotopes have been used (for which more data exist) in the place of krypton-85 and xenon-133. Retention in body organs (animals) has not been fully qualified, although several investigators have reported quantitative values from a few specific experiments. Low solubility of krypton-85 in tissue and blood have been reported, yet full assessment (at least as reported in the literature) seems incomplete. It does appear from reading the literature that the various investigators agree that the lung is a very efficient filter and that the lungs and airways must be considered the critical organ receiving the highest exposure from in­ advertent release of krypton-85. Reference 59, for instance, reports that for short-term exposure of 1 minute and long-term exposure of several hours to a cloud of krypton-85, the absorbed dose by tissue represented about 1 percent of the dose received from external radiation (gamma and bremsstrahlung). 60

Conclusions

In regards to body fluids, krypton-85 has been used in measuring (1) cerebral blood flow, (2) cutaneous blood flow, (3) muscle blood flow, (4) renal blood flow, (5) nitral blood flow, and (6) intestinal blood flow. In all cases, the work was experimental in nature and quite limited in scope. Even if krypton-85 was used on a broad scale as a "routine" clinical fluid-tracer method, only small quantities would be consumed. Furthermore, in many of the literature references, xenon-133 appears to work as well as the kr5T)ton-85.

( 61

Waste Treatment

Reactions initiated by ionizing radiation from various isotopes have been employed or proposed for the treatment of wastes from human activity and from manufacturing. This application of process radiation has vast potential, yet is one of the most controversial because of con­ flicting reports in the literature. Radionuclide sources producing high levels of beta O) or gamma (y), notably cobalt-60 and cesium-137, have been used or proposed for such operations. The scale of demonstration operations has been limited to pilot facilities. Other processes have been limited to bench-scale or laboratory-scale levels wherein the proof-of-principle was demonstrated. Typical studies relating to wastewater treatment employing ionizing radiation have been complied in reviews on process radiation f78-92^ development. ^ ' Primarily, these reviews relate to sewage treatment by radiation to promote improved sedimentation, conversion of organic materials resistant to bacterial attack to those that are, and the destruction of bacteria. Treatment of industrial waste waters (by ionizing radiation) from cotton-textile-finishing mills, Kraft-paper mill^ and wool mills at high oxygen or air pressures was demonstrated to be effective for the reduction of biological oxygen demand (BOD), chemical oxygen demand (COD), and removal of colorants and dyes. The evaluation of the effectiveness of the processes was based on the reduction of these para­ meters and the improved characteristics of the wastewater that result. Disinfection of pathogenic microorganisms in sewage and improved sedimenta­ tion are added benefits obtained by the use of ionization radiation in sewage treatment. Besides the degradation of biologically refractory organic substances, such as phenol, parathion, phenylmercuric acetate, etc., radiation has been demonstrated to be effective in the destruction of cyanide ion in electroplating wastes and enhancing the removal of iron from acid mine drainage by limestone neutralization. 62

The economics related to such concepts have also been considered, especially for sewage treatment plants in the mi11ion-gallon-per-day capacity range. Figure 19 shows the quantity of cobalt-60 that could be purchased for different treatment costs (the price of cobalt-60 in 1969 was about $0.35/Ci, a more optimistic price then was $0.10/C1.^ ^ The radionuclides cobalt-60 and cesium-137 served as the radiation sources in these operations. The radiation characteristics of the two are such that they provide P and y radiation. The average energy of the P is such that the half-depth of penetration in water is 4 cm or less. Therefore, it is the gamma radiation with ability to penetrate materials that provides the energy for chemical change through bond scission (homolytic splitting) or ionization. Krypton-85 radiation characteristics are similar to those of cobalt-60 and cesiiun-137. It is a good beta emitter; however, the gamma is of low yield, 0.41 percent, and does not provide the high yield apparently required for large-scale operations using shield sources. In another limiting sense, the density of the confined gas cannot approach those of the metals (e.g., at standard temperature and pressure the atom con- "19 3 centration for krypton is about 3 x 10 atoms/cm, while for cesium it is 21 22 3 8 X 10 and for cobalt it is 9 x 10 atoms/cm ). In addition, isotopic concentration of krjrpton-SS of 6 percent can be obtained easily, while 45 percent can be obtained only with great difficulty (reference cited earlier). Krypton-85 has properties, however, that make it attractive as a radiation source. For one, the radiation level at the interface between the container for the gas and the reaction media can be controlled by the pressure or concentration of krypton-85 in the container system. This provides an easy means of modulating the amount of radiation being received by the medium. Another property is that it is essentially chemically inert. As such, it might be used as an internal radiation source wherein it is intimately mixed with a gaseous media. In aqueous systems, it exhibits low

( 63

0 0.20 0.40 0.60 0.80 1.00 ALLOWABLE TREATMENT COST, $/lO' QOl

FIGURE 19. QUANTITY OF COBALT-60 THAT CAN BE AFFORDED FOR DIFFERENT TREATMENT COSTS FOR A 1-MGD TREATMENT PLANT

> 64 solubility which is directly temperature dependent. However, with ice it forms hydrates of the general formula Kr«6H20 that have a dissociation pressure of 14.5 atmosphere at 0 C. Its solubility in organic solvents such as freons is known; for other solvent systems it is not known. These properties of krypton-85 suggest that it could be incorpora into reaction media. When used with a gas mixture that yields a condensed phase product, batch reactions are possible if the krypton-85 can be recovered efficiently. Direction treatment of liquids is also possible by sparging and recycling of the kr3T)ton-85 followed by a stripping opera­ tion to assure removal of the gas from the liquid. When used with liquids,

(1) The krypton-85 must not be soluble or at least the solubility should be temperature dependent for ease of recovery (2) If the krypton-85 is soluble, it must be readily removed and recoverable (3) Provisions for recovery and reuse would be mandatory (4) Leakproof gas handling system and storage would be mandatory because of the hazard and the relatively high cost/Ci.

Specific Applications

Reports on the use of krypton-85 for waste disposal or waste desensitization have not been found. Potential applications developed herein are related either to the unique characteristics of the use of a nonreactive radioactive gas or to unusual requirements for specific waste disposal or waste treatment objectives.

Military Unique Waste Disposal or Waste Treatments. The demilitarization programs under way in the Department of Defense pose some unique disposal and treatment problems. Biological- and chemical- warfare agents in particular are hazardous materials requiring specialized treatment and disposal techniques. In addition to these, many other 65 materials that are by-products of manufacturing operation or detoxification treatments are often encountered as fluid waste% either as contaminated or off-grade materials or as pollutants in wastewater from the processing operation.

Germ Warfare Agents. Krypton-85 may provide a unique method for the destruction of pathogenic bacterial agents that are being removed from the military arsenal. As a gas it could be introduced into containers holding these agents, effect the "kill", and then be recovered for reuse. The process could employ the recent findings on the synergistic effect of the addition of heat as well as radiation on the extent and rate of microbiological kills. Thermoradiation sterilization as it is called combines the dry heat and ionizing radiation in a way which results in greater microbial inactivation than the additive effects would imply.^ ^ Replacement of a fixed radiation source such as cobalt-60 by krypton-85 could provide even greater utility and could shorten the processing time considerably due to the intimate contact between the radioactive source and the organism than could be possible with cobalt-60. Thermoradiation processing reduces the propensity for mutant formation present when radiation is used alone.^ ^ Similar synergism was observed for the treatment of sewage sludge but the utility of krypton in such operations seems doubtful because of the large (92) volumes of wastes that could be encountered.

Chemical-Warfare Agents. The nitrogen and sulfur mustards and the nerve gases GB and VX are presently being destroyed as part of the overall demilitarization program. Concentrated streams are being incinerated, chemically treated (aqueous oxidation^ or hydrolyzed. Treatment of con­ taminated aqueous streams is possible in areas where ionizing radiation might be applied. In general, the approach would be to treat these aqueous waste streams to convert the biologically refractory organic materials to substances more readily attacked by microorganisms. 66

GB and VX. In the process of destroying GB, as currently practiced, the agent is hydrolyzed by strong caustic soda solution and the resulting brine is spray dried. In the exothermic hydrolysis step, the fluorine atom is very rapidly hydrolyzed off,but the resulting isopropyl ester of methyl phosphonic acid sodiim salt (SIM) is very resistant to hydrolysis and remains in the brine along with sodium fluoride and excess sodium hydroxide. There is considerable evidence that small amounts of GB are re-formed in the spray dryer. Studies have shown that treatment of SIM with hydro­ fluoric acid will produce GB. An alternative being considered is to chemically destroy the SIM in aqueous solution by oxidation. It is known that the combined effect of oxygen and ionising radiation is capable of altering organic constituents through the aqueous oxidation route. Destroying SIM in this manner eliminates the possibility of GB reformation. Thus, a krypton-85 - O2 mixture could be recirculated through the brine to provide in situ activation and reagent. Unfortunately, a calculation estimating the quantity of kr3T)ton-85 necessary to destroy all SIM present in a typical day's waste stream equaled 10 grams of krypton containing 6 percent krypton-85, see Appendix c. Q This equals approximately 10 curies of krypton-85, a quantity too large to be practical. V2^ being more resistant to hydrolysis reaction with caustic sod^ could possibly be destroyed by simultaneous treatment with ionizing radiation from krypton-85 passed through the media.

Persistent Organics in Wastewater. Certain organic compounds such as phenols and various pesticides are resistant to microbial attack in aqueous systems. Also, in TNT manufacture, trace amounts of nitrated toluenes or their hydrolysis products (red water) are not amenable to conventional wastewater treatment and find their way into surface waters. In such cases, irradiation of the wastewaters in the presence of air or oxygen has been known to alter compounds such as phenols and render them suitable to microbial attack. ^'°''^°>

{ 67

It is well known that krypton-85 will form clathrates .with phenol- or quinol-type compounds under suitable conditions of high krypton pressures. This attraction of such molecules for krypton even in aqueous systems might provide the means of irradiation in close proximity to these molecules. Even if the conditions for clathrate compound formation are not attained, the very fact that these compounds would tend to form suggests some attraction of these compounds for krypton-85. With simultaneous treatment with air or 02, and krypton-85 supplying the radiation, rapid conversion of such J J ^ui (78,80,84,87,89) ^ x u^ u compounds is possible. ^ > > > > >' xhe use of high gas pressures would augment the solubility of both gases and enhance the desired reactions. ' To estimate the quantity of krypton-85 necessary to destroy 500 ppm refractory molecules in a waste stream flowing at 1 million gallons per day, a rough calculation was made. Referring to the Appendix C, it is estimated that 10 grams of krypton (6 percent krypton-85) or 10 curies of krypton-85 is required for this destruction. Although an order of magnitude less than the requirements for SIM destruction, this needed krypton quantity is also too large to be practical.

Conclusions

Krypton-85, because of its low-yield gamma radiation, is a rather poor source for irradiation suitable for chemical processing. Because of this low gamma level, the bremsstrahlung effects are very narked and could serve as an alternative, but lower, energy source of gansna radiation. The limited quantities of krypton-85 and its relatively high cost per curie, combined with the problems of confining and handling a gas, suggest that its application to waste treatment may be restricted. The use of krypton-85 at the 6, 25, and 45 percent levels in mixtures with other gases such as oxygen will require extensive review and study. Many questions remain unanswered. For example: Will the potential for ozone formation require separation of the two gases prior to storage - Will the concentration be limited by an equilibrium established between 68 the rate of ozone formation and the rate of its decomposition? The most viable use for krj^ton-SS would be in the dry sterilization treatment of germ-warfare materials and related areas. It also shows promise where controlled or modulated irradiation levels are needed. 69

Environmental Control of Submersibles

Environmental control of submersibles was investigated, addressing mainly the use of krypton-85 heat source applications. The following specific applications were addressed:

• Submersible environmental control system (ECS) • Personnel-transfer capsule (PTC) ECS gas heater (He'02 to 1500 feet of seawater) • Wet suit diver heating system • Dry suit or unisuit diver heating system • Submersible battery heater.

The various identified topics are briefly discussed below.

Submersible Environmental Control System

Experiments conducted with a personnel transfer capsule at 1 (93) atmosphere indicate about 200 watts per F may be needed to heat an uninsulated steel chamber such as a submersible hull. For a 50 degree temperature rise (40 F water temperature to 90 F breathing gas tempera­ ture) , as much as 3,000 watts may be required. If krypton-85 power density is assumed to be 0.56 watts per gram (fully enriched krypton), about 33 kg-moles of the pure isotope would be required. This requirement is clearly not a practical consideration. In the first plac% present enrichment procedures cannot give that purity of krypton-85 in that quantity. And, even if one considers 45 percent enriched krypton-85, that means at least 6 kilograms would be required. Finally, even if one could consider obtaining the gas, one would have to consider shielding the krypton-85, an item that would add considerable weight to the submersible. 70

Personnel Transfer Capsule Environmental Control Gas Heater

Test results of Reference 93 indicate that an uninsulated personnel-transfer capsule may require as much as 27,000 watts to maintain an internal temperature of 90 F when submerged in water at 40 F. Such a heat load would require too large an inventory of kr3^ton-85. However, experiments ^ ^^ and calculations indicate that the heat required for breathing gas to personnel-transfer capsule or recompression-chamber occupants is not excessive and may be within krypton-85 capacities. The gas heater ^ ^ worked well with a heat input of about 320 watts and the calculated heat requirement for an emergency fly-away recompression chamber could be as low as about 2400 watts. Reference 95 indicates that the heating load of a large deep-diving chamber complex could be as much as 7600 watts, which would be excessive for krypton-85.

Wet Suit or Dry Suit Diver Heating System

Heat sources delivering about 1 kilowatt ^ ^ have been identified as necessary to keep a wet suit diver warm. Although, this heating requirement could be met using kr3T)ton-85, the shielding required for the 1 kilowatt of krypton-85 would be large and the concept (krypton-85 heater for a wet suit) does not qualify as a good one. As for a dry suit diver, it is unlikely that he would require much if any external heat as he is normally wearing thermal underwear in a dry suit.

Submersible Battery Heaters

Reference 97 indicates the feasibility of using radioisotopes to heat silver-zinc batteries to increase their efficiencies at low temperatures. Since silver-zinc batteries are commonly used in sub­ mersibles, the possibility of heating submersible batteries was investigated. Generally, submersible batteries are high-drain applications where heat is actually generated in the silver-zinc cells from their use and, therefore. 71 external heating should not be required. However, where silver-zjLnc batteries are used in cold waters, then some heating requirements may exist. Those regions have not been identified, however.

Conclusions

Krypton-85 heaters for submersibles appear to be either unattractive from the standpoint of cost and quantity or altogether impractical because of the high thermal inventory required. 72

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(31) Beremand, D. G., et al., "Experimental Performance Characteristics of Three Identical Brayton Rotating Units", Proceedings of the Fifth Inter­ society Energy Conversion Engineering Conference (ANS): Energy, No. 70, p 4-18 and 4-26 (1970).

(32) Pouchat, W. D., and Daniels, A., "Nuclear Artificial Heart Bench Model", Ninth Intersociety Energy Conversion Engineering Conference Proceedings (ASME), August 26-30, 1974, pp 782-790.

(33) Martini, W. R., "Unconventional Stirling Engines for the Artificial Heart Application", Ninth Intersociety Energy Conversion Engineering Conference Proceedings (ASME), August 26-30, 1974, pp 791-798.

(34) Boretz, J. E., et al., "Turbine Organic Rankine Engine System for Artificial Heart Application", Ninth Intersociety Energy Conversion Engineering Conference Proceedings (ASME), August 26-30, 1974, pp 813-823.

(35) Feibush, A. M., "Research on Applications of Krypton-85 and Other Radio­ active Isotopes", NYO-2906-1 (September, 1964).

(36) Stone, E. W., George, J.H.B., and Beutner, H. P., "Isotopes in Industry", NYO-3337-16 (September, 1965).

(37) Figueroa, C. G., "Krypton Potential in Aerospace", Proceedings of the Second International Symposium on Nucleonics in Aerospace, Columbus, Ohio (July, 1967).

(38) Polluck, E. M., Fujita, M., and Kuser, H. C, "Isotropic Propellant Level Indicator", Ibid.

(39) "Kryptonate Inspection of Embrittled Structures", Contract N0O-156-68-C-0348, Final Report to Naval Air Systems Command, Washington, D.C. by Industrial Nucleonics Corporation, Columbus, Ohio (February, 1968).

(40) Balek, "Application of Inert Radioactive Gases in the Study of Solids", Materials Science, 4 (1969), pp 919-927.

(41) Tiner, N. A., and Asunnaa, S. K., "Microautoradiography of Kryptonated Aluminum Alloys", Materials Research and Standards, JJO, NO. 4 (April, 1970).

(42) Murgatroyd, John L., "Leak Rate Determination Using Krypton-85", IEEE Transactions on Instrumentation and Measurement, IM-21. No. 1 (February, 1972).

(43) Wisnieff, S. F., and Bardach, H., "Radioactive Krypton Simplifies Temperature Mapping of Turbine Blades", SAE Journal, 74, No. 8 (August, 1966), pp 56-59.

(44) Nickola, P. W., Ludwick, J.oP., and Ransdell, Jr., J. V., "Atmospheric Tracer Technique Employing Kr and Use of this Technique in Defining Puff Dimensions and Transport Speed", Isotopes and Radiation Technology, 9, No, 1 (Fall, 1971). 75

(45) Gerrard, Martha, and Lafferty, Jr., R. H., "Kryptonate-Based Instrument for Detecting Automobile-Exhaust Pollutants", Isotopes and Radiation Technology, 8, No. 4 (Summer, 1971).

(46) Bruton, W. A., and Packer, L. L., "Radioactive Temperature Indicator Research and Development", Contract No. NNO-156-69-C-0595, Final Report to Naval Air Systems Command, by United Aircraft Corporation, East Hartford, Connecticut (July, 1970).

(47) Packer, L., and Woody, B., "Radioactive Temperature Indicator Research and Development", Contract No. NOO-156-71-C-0816, Report to the Naval Air Systems Command by United Aircraft Corporation, East Hartford, Connecticut (March, 1972).

(48) Private communication with L. L. Packer, United Aircraft Corporation, East Hartford, Connecticut.

(49) Gerrard, Martha, "Recent DID Radiometric-Technique Developments", Isotopes and Radiation Technology, Vol 9, No. 1 (Fall, 1971).

(50) Ballou, J. E., and Cannon, W, C, "Preliminary Investigation with Inhaled S^Kr in the Rat and Beagle Dog", BNWL-1850 (PTl) (August, 1974), pp 76-77.

(51) Morken, D. A., "Biological Effects of the Radioactive Noble Gases", UR-3490-383 (1973).

(52) Fontenelle, A., and Bergeron, M., "Radloautographic Studies of Krypton- 85 Clearance from Rat Incisor Pulp and Surrounding Tissue", Arch. Oral Biology, 18, No. 9 (September, 1973), pp 1069-1076.

(53) Oldendorf, W. H., "Radioisotopic Methods for Cerebral Blood Flow Determina­ tion", American Lecture Series, No. 771, pp 27-53 (1970).

(54) Fiechi, Cesare, "Cerebral Blood Flow in Neurological and Neurosurgical Patients", AmericJan Lecture Series, No. 771 (1970), pp 55-75.

(55) Wagner, H. N,, "Radioactive Gases for Studies of the Brain", Central Nervous System Investigation with Radionuclides, pp 125-135, A. J. Gilson, editor, Springfield, Illinois; C. C. Thomas, Publisher (1971).

(56) Reinmuth, 0. M., "Inhalation and Intravenous Methods for Measurement of Cerebral Blood Flow", Ibid.

(57) Lessen, N. A., et al., "Blood Flow Studied by Freely Diffusible Radio­ active Indicators: Diagnostic Application in Peripheral Arterial Disease" (Bispebjerg Hospital, Copenhagen), Strahlentherapie, Stonderbaende 65 (1967), pp 145-152.

(58) Gruenfield, J. P., Bankir, L., and Funck-Brentano, J. L., "Study of Renal Blood Flow in the Nonanesthetized Rabbit Using ^^Kr" (Hospital Necker, Paris), Rev. Eur. Etud. Clinical Biology, 17, No. 4 (April, 1972), pp 399-405 (in French). 76

(59) Whitton, J. T., "Calculations of Whole Body Dose from Absorption of an Inhaled Noble Gas", Health Physics, 23, No. 4 (October, 1972), pp 573-575.

(60) Lyngborg, Kjeld, Lindeneg, Ole, and Mellemgaard, Kresten, "New Quantita­ tive Method for Determination of Mitral Regurgitation by Continuous In­ fusion of an Inert Gas ( Kr) in Aqueous Solution" (Rigshospitalet, Copenhagen), Verk. Deut. Ges. Kreislaufforsch, 31 (1965), pp 285-288 (in German). 85 (61) Sejrsen, Per, "Diffusion Processes Invalidating the Intraarterial Kr Beta-Particle Clearance Method for Measurement of Skin Blood Flow in Man", Circulation Research, 21 (September, 1967), pp 281-295. 85 (62) Lenaers, A., et al., "Measurement of Cerebral Blood Flow by Kr", CONF-660121 (1967). (63) Lundgren, Ove, "Studies of Blood Flow Distribution and Countercurrent Exchange in the Small Intestine", Acta Physiology Scand., Suppl. 303, University of Gothenburg, Sweden (1967), p 42.

(64) Haeggendal, Egil, Johan, Nils, and Norbaeck, Bergt, "On the Components of "Kr Clearance Curves from the Brain of the Dog", Acta Physiology Scand., Suppl. 258, University of Gateborg, Sweden (1966), pp 5-25.

(65) Lundgren, 0., and Kampp, M., "Washout of Intraarterially Injected "•'Kr from the Intestine of the Cat", Experimentia, 22 (1966), pp 268-270.

(66) Ladefoged, J., "The Significance of Recirculation for the Detejnnination of Intrarenal Blood Flow Distribution from Krypton-85 and Xenon-133", Clin. Lab. Invest., 16 (1964), pp 479-480.

(67) Degner, W., Hegewald, H., and Thormann, T,, "Krypton-85 Irradiator with Special Reference to the Radiation Protection Problem in Dermatology", Radiobiol. Radiother., 3 (1962), pp 621-623 (in German),

(68) Holyman, G. B., et al., "Measurement of Muscle Blood Flow in the Human Forearm with Radioactive Krypton and Xenon", Circulation, 30 (July, 1964), pp 27-34.

(69) Cleempoel, H., et al., "Use of Dissolved Kr-85 in the Study of Pulmonary and Bronchial Shunts", CONF-640808-1 (1964).

(70) Hollenberg, Milton, "Hepatic Blood Flow Measured by the Portal Venous and Hepatic Arterial Routes with Krypton-85", CONF-650112-1 (1965).

(71) Lessen, N, A., and Klec, A., "Cerebral Blood Flow Determined by Satura­ tion and Desaturation with Krypton-85: An Evaluation of the Validity of the Inert Gas Method of Kety and Schmidt", Circulation Research, 16 (1965), pp 26-32.

(72) Alexander, S, C, et al., "Krypton-85 and Nitrous Oxide Uptake of the Human Brain During Anesthesia", Anesthesia, 25^ (January-February, 1964), pp 37-42. 77

Wagner, Jr., H. N., "Regional Blood Flow Measurements with Krypton-85 and Xenon-133", TID-7678 (1964), pp 189-212.

Donato, L., et al., "Quantitative Radiocardiography II. Technic and Analysis of Curves", Circulation, 26 (August, 1962), pp 183-188.

Lewis, M. L., et al., "Quantitative Radiocardiography III. Results and Validation of Theory and Method", Circulation, 26 (August, 1962), pp 189-199.

Lassen, N. A., "Assessment of Tissue Radiation Dose in Clinical Use of Radioactive Inert Gases with Examples of Absorbed Doses from H, °^Kr, and 133xe", Minerva Nucl., 8 (July-August, 1964), pp 211-217.

Handbook of Chemistry and Phvsics. Charles D. Hodgeman, editor. The Chemical Rubber Publishing Company, Cleveland, Ohio, 42nd edition (1961). Ballantlne, "Potential Role of Radiation in Waste-Water Treatment", Isotopes and Radiation Technology, 8, No. 4 (1971), p 415.

Steinberg, Meyer, and Beller, Morris, "High Energy Radiation Synthesis of Ozone for Water Treatment", Ibid., p 420.

Gerrard, Martha, "Sewage and Waste-Water Processing with Isotopic Radiation: Survey of the Literature", Ibid., p 429.

Gerrard, Martha, "Conceptual Design of an Irradiation Test Facility for Waste Water and Sewage Sludge", Ibid., p 435.

Mann, Leland A., "Biological-Gamma Radiation System for Sewage Processing", Ibid., p 439.

Mytelka, A. J., "Radiation Treatment of Industrial Waste Waters on Economic Analysis", Ibid., p 444.

Campbell, Lome A., "Gamma Irradiation as a Pretreatment to Chemical Precipitation in the Purification of Domestic Sewage", Ibid., p 449.

Vajdic, A. H., "Gamma Irradiation of Waters and Waste Waters for Dis­ infection PuiTJOses", Ibid., p 451.

Andrews, R. H., and Fielding, M. B., "Gamma Irradiation of Raw Sewage for Sedimentation Purposes", Ibid., p 452.

Comption, D.M.J., "Destruction of Organic Substances in Waste Water by Ionizing Radiation", Ibid., p 453.

Case, F. N., Kau, D. L., Smiley, D. E., and Garrison, A. W., "Radia­ tion-Induced Oxidation of Process Effluents at High Pressure", Iso­ topes and Radiation Technology, 9, No. 1 (1971), p 101.

Encyclopedia of Chemical Technology. Kirk-Othmer, Vol. 10, 2nd edition (1971), p 888. 78

(90) Sivinski H. D., and Reynolds, M. C, "Synergistic Characteristics of Thermoradlatlon Sterilization" Life Sciences and Space Research X. Akademic-Verlag, Berlin (1972), p 33.

(91) Dillon, R. T., and Conley, M. B., "Rates of Mutant Production in Bacillus Subtilis by Dry Heat and Gamma Irradiation: A Preliminary Report", Sand 75-0037, Sandla Laboratories, Albuquerque, New Mexico 87115 (April, 1975).

(92) Sivinski, H. D., "Treatment of Sewage with Combination of Heat and Ionizing Radiation (Thermoradlatlon)", lAEA-SM-194/303, IAEA Symposium on the Use of High Level Radiation in Waste Treatment - Status and Prospects, Munich, Germany (March 17-21, 1975).

(93) "Experimental Determination of Heat Requirements for the Mark I PTC", Battelle,Colimibus Laboratories Task Report to U.S. Navy, Supervisor of Diving, Septeniber 8, 1969.

(94) "Development of an Experimental Breathing Gas Heater", Battelle, Columbus Laboratories, Task Report to the Navy, Supervisor of Diving, September 24, 1969.

(95) "Preliminary ECS Performance Specification" prepared by Battelle, Columbus Laboratories, for proposed Canadian Navy Diving Chamber Complex.

(96) Proceedings from Committee Meeting on Diver Heating. LCdr Majendie, Chairman, held at the U.S. Navy Experimental Diving Unit, February, 1969.

(97) Levy, I. M., and Bustard, T. S., "A Radioisotope Heater for a Silver-Zinc Battery", Nucleonics in Aerospace, New York, Plenum Press (1968), pp 200-207.

(98) Matheson Gas Data Book, Matheson Company, 4th edition (1966) p 313.

(99) Handbook of Chemistry and Physics, Charles D. Hodgeman, editor. The Chemical Rubber Publishing Company, Cleveland, Ohio, 42nd edition (1961).

(100) Arnold, E. D., Handbook of Shielding Requirements and Radiation Character­ istics of Isotonic Power Sources for Terrestrial. Marine, and Space Applications. ORNL 3576 (April, 1964).

(101) National Bureau of Standards Certificate Standard Reference Material 4935-C, Radioactivity Standard, Kr3rpton-85, National Bureau of Standards (March 29, 1974). APPENDIX A

SELECTED PHYSICAL PROPERTIES OF KRYPTON-85

> TABLE 1. SELECTED PHYSICAL PROPERTIES OF KRYPTON-85

Physical Properties

Melting Point at STP^ ^ -157.1 C Boiling Point at STpC98) -152.9 C Critical Temperature(98) 63.8 C Critical Pressure (98) 54.3 atm ,gs^ (798.2 psia) Heat of Vaporization at Boiling Point'' -' 2310 cal/mole Density (gas)(99) 3.708 x 10-3 g/cm^ Density (liquid)(100) 2.16 g/cm3

Radioactive Properties

Half Life(101) 10.75 years Decay Characteristics ^^^^ P 0.67 Mev max 0.249 Mev avg riOO^ Y 0.514 (0.41%) Fission Yield from U-235<>1"") 0 3^^ Heat Generation Rate (^) 60 w/mole (fully enriched Yi^P) 0.7 w/g Heat Generation Rate ' ^ 0.56 w/g Specific Activity'(^^) 390 Ci/g

1.5 Ci/cm^ (STP)

Maximum Permissible Biospheric Concentrations

(For submersion in a hemispherical infinite cloud)^ ^ 3 x 10"' tiCi/ml

(a) Calculated by the authors. APPENDIX B

THE NUCLEAR POWER INDUSTRY

^ APPENDIX B

THE NUCLEAR POWER INDUSTRY

U.S. Commercial Power Reactor Characteristics 1960 - 1990

Appendix B Includes several figures and tables which provide more insight into the production of fission products from U.S. commercial power reactors. Figures B-1 and B-2 show the projected growth of commercial nuclear power plants over the next 15 years while Tables B-1 through B-6 give projected kr3rpton-85 and stable krjrpton isotope yields. Legend • Pressurized water reactors X Boil ling-water reactors • o High-temperature gas reactors O Liquid-metal fast breeder reactors •

•

• ~

— •

• X X X • • X

• X

X

• X X • X

X X • o o • o . ^ f o 1 o ^ ° 1 1965 0 1971 0 1975 , 1980 1985 Year ^^ FIGURE B-1. PROJECTED CUMULATIVE NUMBER OF U.S. NUaEAR POWER PTJ^NTS^ ^ IN OPERATION Legend • Pressurized water reactors ^ X Boilling-water reactors • o High-temperature gas reactors O Liquid-metal fast breeder reactors *

X X X X

X

X

• X X

» o ° f> • f s 1965 1970 1975 1980 1985 Year FIGURE B-2. PROJECTED CUMULATIVE NUCLEAR POWER PLANT CAPACITY (ELECTRICAL)^^^^ No cnr-ecHons made for reactors out of service. B-4

TABLE B-1. QUALIFYING CONDITIONS FOR THE CALCULATED FISSION GAS KRYPTON-85 YIELDS REPORTED IN TABLES B-2 THROUGH B-6

Conditions are direct quotations from BNI"7L-716.

Data were generated by the ISOPRO Computer Program at Battelle's Pacific Northwest Laboratories(2^)

Conditions: 1. Installed nuclear capacity and ijsotope production and availability are always stated as of the end of the year shown.

2. Yearly capacity additions startup at mid-year.

3. Nuclear power plant life is 30 years.

4. Nuclear power plant capacity factors are 85 percent for 15 years.

5. Light water reactors are 67 percent Roll's and 33 percent BWR's after 1971. Contract commitments and operating reactors are used for prior years.

6. One year between reactor discharge and recovery of any Isotope. Recovery corrected for decay losses.

7. 98 percent recovery of plutonium and uranium.

8. 90 percent recovery of all other by-products.

9. Pu-238 formed by CM-242 decay, except for first year prior to separations, is available with the Cm-244. B-5

TABLE B-2. CUMULATIVE AVAILABILITY OF KRYPTON-85 AND STABLE KRYPTON FROM LIGHT WATER REACTORS FUELED WITH SLIGHTLY ENRICHED URANIUM WITHOUT PLUTONIUM OR URANIUM RECYCLE

Production Values Reflect only Decay Losses. Results Computed by ISOPRO Computer Program.

— Year Kr-85 Stable Kr End ing Production, kg Production, kg

1960 0.0 0.0 1966 1.0 16,2 1969 1.0 39.9 1970 2.0 52.1 1971 5,0 71.1 1972 9.0 128.2 1973 17,0 242.5 1974 27,0 453.6 1975 36,0 787.1 1976 43,0 1,223.7 1977 54,0 1,758.3 1978 65,0 2,416.6 1979 75,0 3,210.9 1980 87,0 4,134.0 1981 103.0 5,197.2 1982 133.0 6,457.7 1983 149.0 8,077.4 1984 166.0 9,894.6 1985 194.0 11,912.5 1986 223.0 14,258.2 1987 245.0 16,950.2 1988 277.0 19,892.5 1989 311.0 23,212.4 1990 338.0 26,937.1 B-6

TABLE B-3. CUMULATIVE AVAILABILITY OF KRYPTON-85 AND STABLE KRYPTON FROM LIGHT WATER REACTORS WITH 50 PERCENT U-236 PRODUCTION RECYCLED

Production values reflect target irradiation process losses and decay losses. Results computed by ISOPRO computer program.

Year Kr-85 Stable Kr Ending Production, kg Production, kg

1960 0.0 0.0 1966 1,0 16.2 1969 2.0 39.9 1970 3,0 52.1 1971 4,0 71.3 1972 8.0 129.1 1973 16,0 245,2 1974 29.0 459.9 1975 51.0 798.8 1976 78.0 1,242.7 1977 110.0 1,774.4 1978 147.0 2,417.2 1979 191.0 3,181.9 1980 241.0 4,083.9 1981 299.0 5,152.1 1982 368.0 6,420.3 1983 456.0 8,023.6 1984 552.0 9,830.1 1985 658.0 11,852.4 1986 780.0 14,189.6 1987 921.0 16,894.0 1988 1,073.0 19,892.3 1989 1,273.0 23,252.2 1990 1,422.0 26,900.5 B-7

TABLE B-4, CUMULATIVE AVAILABILITY OF KRYPTON-85 AND STABLE KRYPTON FROM LIGHT-WATER REACTORS FUELED WITH SLIGHTLY ENRICHED URANIUM WITH PLUTONIUM RECYCLED

Production values reflect no losses except for radio­ active decay.

Results computed by ISOPRO computer program.

Year Kr-85 Stable Kr Ending Production, kg Production, kg

1960 0.0 0.0 1966 1.0 16.2 1969 2.0 39.9 1970 3.0 52.1 1971 4,0 71.1 1972 8,0 128.2 1973 15.0 242.5 1974 29.0 453.6 1975 50.0 787.1 1976 77.0 1,222.2 1977 108.0 1,753.7 1978 145.0 2,387.2 1979 188.0 3,135.4 1980 235.0 4,002.4 1981 289.0 4,996.2 1982 352.0 6,166.6 1983 432.0 7,642.6 1984 520.0 9,305.4 1985 616.0 11,142.6 1986 725.0 13,260.6 1987 849.0 15,674.6 1988 981.0 18,305.4 1989 1,125.0 21,223.3 1990 1,285.0 24,489.1 B-8

TABLE B-5. CUMULATIVE AVAILABILITY OF KRYPTON-85 AND STABLE KRYPTON FROM LIGHT^ATER REACTORS FUELED WIlTi SLIGHTLY ENRICHED URANIUM WITH PLUTONIUM AND 50 PERCENT OF U-236 RECYCLED

Production values reflect no losses except for radio­ active decay.

Results computed by ISOPRO computer program.

Year Kr-85 Stable Kr Ending Production, kg Production, kg

1960 0,0 0.0 1966 2,0 25.8 1969 4,0 27.9 1970 5,0 79.2 1971 9.0 143.4 1972 18,0 272.5 1973 35,0 511.0 1974 60,0 887.5 1975 93,0 1,379.6 1976 130.0 1,966.5 1977 172.0 2,658.1 1978 221.0 3,463.2 1979 278.0 4,403.1 1980 340.0 5,509.1 1981 416.0 6,827.4 1982 510.0 8,469.2 1983 614.0 10,296.9 1984 727.0 12,343.6 1985 857.0 14,693.7 1986 1,006.0 17,401.8 1987 1.164.0 20,360.4 1988 1,338.0 23,651.3 1989 1,522.0 27,205.2 1990 1,721.0 31,116.3 B-9

TABLE B-6. CUMULATIVE AVAILABILITY OF KRYPTON-85 AND STABLE KRYPTON FROM LIGHT-WATER REACTORS WITH 50 PERCENT U-236 RECYCLE AND MAXIMUM FAST BREEDER REACTOR ADDITIONS BEGINNING IN 1980

Values reflect target irradiation process losses as well as radioactive decay losses.

Results computed by ISOPRO computer program.

Year Kr-85 Stable Kr Ending Production, kg Production, kg

1960 0.0 0.0 1966 1.0 16.2 1969 2.0 39.9 1970 3.0 52.1 1971 4.0 71.3 1972 8.0 129.1 1973 16.0 245.2 1974 29.0 459.9 1975 51.0 798.8 1976 78.0 1,242.7 1977 110.0 1,774.4 1978 147.0 2,417.2 1979 191.0 3,181.9 1980 241.0 4,083.9 1981 299.0 5,152.1 1982 367.0 6,415.0 1983 454.0 8,011.0 1984 548.0 9,784.4 1985 651.0 11,757.0 1986 767.0 14,021.9 1987 898.0 16,605.5 1988 1,038.0 19,436.6 1989 1,190.0 22,582.2 1990 1,344.0 25,909.7

^ APPENDIX C

QUANTITATIVE ESTIMATION OF KRYPTON~85 QUANTITIES REQUIRED TO DESTROY REFRACTORY MOLECULES

• APPENDIX C

QUANTITATIVE ESTIMATION OF KRYPTON-85 QUANTITIES REQUIRED TO DESTROY REFRACTORY MOLECULES

Three cases are evaluated here; (1) the quantity of kr3rpton-85 needed to destroy SIM as produced at Rocky Mountain Arsenal, (2) the quantity to destroy refractory molecules in a tjT>ical waste stream, and (3) a rule of thumb relating the quantity of krjT)ton-85 needed to destroy a given quantity of refractory substance in 1-day irradiation. In all cases the krypton gas is assumed to be 6 percent enriched with krypton-85 and intimately mixed with the substance being treated.

Case 1

Assuming a molecular weight of 138 for SIM and a waste-stream rate of 26,000 1/day with a SIM concentration of 420 g/1,* the necessary destruction rate of the SIM molecule is 79,000 g-moles/day or 4.76 x 10^8 molecules/day. Assuming a G value of 10 (i.e., 10 SIM molecules destroyed for every 100 ev of energy absorbed), the destroying radiation must deposit 29 into the SIM stream 4.76 x 10 ev/day. Krypton at 6 percent krypton-85 enrichment produces 2.13 x 10 29 . 11 Mev/sec-g. Therefore, 4.76 x 10 f 2.13 x 10 , with proper conversion of units, yields 2.58 x 10 g krypton containing krypton-85 enriched at 6 percent. This quantity, 28.6 tons of krypton, is in excess of that practical for SIM destruction at RMA.

Case 2

Assume a waste stream containing 500 ppm (500 mg/1) and flowing at a rate of 1 million gallons per day. Assuming the refractory molecule

*Flnal Report to Edgewood Arsenal on "Treatment of Brine Resulting from Hydrolysis of GB and Alternatives", May 13, 1975. C-2 to have a molecular weight of 150 yields the required destruction rate of 1.26 X 10 g-mole/day or 7.6 x 10 molecules/day. Assuming G = 10, radiation energy absorption must equal 28 11 mergy 7.6 X 10 ev/day. Using the value of 2.13 x 10 Mev/sec-g for energy 6 production from krypton (6 percent enriched with krjrpton-SS), 4.12 x 10 g of kr}T)ton is required for destruction.

Case 3

Assuming the existence of a general waste stream containing refractory molecules of molecular weight 150, and a radiation source of krypton containing krypton-85 at 6 percent enrichment, destruction requirements dictate that approximately 2 g of krypton is required to destroy each gram of refractory molecule for 1 day's irradiation.