JAERI-Conf 95-015

3-2 TECHNICAL ISSUES RELATING TO THE RECYCLE OF CONTAMINATED SCRAP METAL

by

Stephen Warren, U.S.Department of Energy, Office of Environmental Restoration (EM-43), Quince Orchard, 19901 Germantown Road, Germantown, MD 20784

Donald E. Clark, Westinghouse Hanford Co., 601 Williams Blvd., Suite 2A, Richland, WA 99352

ABSTRACT

A review was made of the literature on melting of radioactive metals that was published in the 1980s and 1990s with attention to the resultant partitioning of radioactivities. Various factors influencing the transfer of radionuclides from the melted ingot phase to other phases such as the slag layer need to be considered both in optimizing the partitioning of radioactivities and in assessing the radiation exposures received by workers. Important technical issues relating to the recycle of radioactive scrap metal (RSM) have been identified and will be discussed in this presentation. Of particular interest is the modeling of radiation doses resulting from operations involving RSM and with recycled materials resulting from the melting of RSM, with emphasis on radioactively contaminated ferrous metals. Such doses result from exposure to the radioactively contaminated metals as well as secondary wastes (i.e., slag, dust, and aerosols/filter media) produced as byproducts of the melting operations.

Summary and Conclusions

The reported results for partitioning of radioactivities that are achievable by melting of contaminated ferrous metals have been reviewed. The resultant redistribution and stabilization of radioactivities is important for possible recycling of these materials. For dose calculations of the various recycling options, it is essential to have credible partitioning data for each treatment scenario. Such data exist for only a few radionuclides (e.g., of the elements uranium, plutonium, and cobalt); the need for new or additional data has been identified.

There are a variety of contaminated metals some of which require treatment with different slags and different melting processes. Control of thermochemistry of such processes is essential. Optimal sizing of melting heats is also required for cost-effectiveness.

In general, most of the reported melting work was not done under controlled conditions and no useful thermodynamic data were obtained. There is a need for such data on contaminants in iron and various slags. At the very least, the partition ratios for key radionuclides in given slags must be determined.

- 135- JAERI-Cont 95-015

Data on microscopic distribution and speciation of radionuclides are lacking. Also, the effects of subsequent treatments (e.g., rolling, milling, welding) on radioactivity remaining in the remelted metals have not been investigated.

Pretreatment methods applied to radioactively contaminated metals prior to melting should include decontamination of surfaces, segregation according to base metal, segregation according to radionuclide contaminant chemistry, and size reduction/compaction as required for furnace loading.

Studies culminating in the design of an integrated process for feed pretreatment/preparation and control of gaseous effluents should be initiated. These studies must include attention to mechanical methods capable of operation within containment to assure adherence to the as- low-as-reasonably-achievable (ALARA) principle of radiological safety.

The key issues to be addressed in implementing a recycle program of any magnitude for radioactively contami'-ated metals include the following:

establishment of a credible database concerning materials to be recycled, including chemical and radioactive characteristics

determination of radioactive partitioning between the metal and slag phases

assured operability of the process, subject to widely varying feed chemistry and conditions

demonstrated ability to seal the candidate process to prevent the release of hazardous species

effective modeling of radiation exposures to workers throughout the recycling process

An integrated program for recycling radioactively contaminated metals is being developed which will focus resources and address these issues in the near future.

Introduction

In the United States (U.S.), very large quantities of radioactively contaminated metals have been generated as by-products of nuclear weapon materials production and the associated research and development activities at federal sites operated by the U.S. Department of Energy (DOE). When no longer available or useful for intended purposes, or when they are the result of decommissioning of facilities, such metals are referred to as radioactive scrap metal (RSM). In addition to the RSM produced at DOE sites, significant quantities of RSM have arisen or will be generated in the future from activities in the private sector including nuclear power production. For economic and safety reasons, the recycling and reuse of RSM

- 136- JAERl-Conf 95-015 is now receiving serious consideration by U.S. nuclear managers in their planning for waste management, facility and site decommissioning, and environmental remediation activities.

In the case of some radioactively contaminated metals, where only the contamination of accessible surfaces has occurred, decontamination or removal of radioactivity by chemical or mechanical methods is readily achievable. Within the restrictions of existing regulations, such decontaminated materials may then be reused or recycled into other products. However, where volumetric or persistent contamination and inaccessible surfaces are involved, melting is recognized as a desirable option that can effect volume reduction; production of useful product sizes, shapes, and volumes; homogeni2ation of radioactivities; reduced radiation exposures; and partitioning of radioactivities, including an effective removal of radionuclides for certain RSM.

Over the past two decades or so, many studies and demonstration tests of the melting of radioactively contaminated metals have been conducted and reported on, particularly in the U. S. Germany, France, United Kingdom, and Japan. Worcester and co-workers (Worcester. 1993) reported that they had identified nearly 300 publications related to the application of melting to RSM. A summary of large-scale melting programs for ferrous RSM is given in Table 1. The present review is focused on the reported work with melting of ferrous metals, and especially on the results obtained for partitioning of radioactivities.

Table 1. Summaiy of Large-Scale Mejong Programs for Radioactively Contaminated Ferrous Metals'

Reference/Country Type/Size of Furnace (Ion) Total Weight Melted (ton)

GomerfWyUK Induction/0.5 1 diluted to 24, Arc/5 and 160 then rediluttd 300 Basic Oi

Menon (!990ySweden Induction/1.6 210

Peulue(1992VFrancc Arc/16 2.800

Sappok (1992yGermany Induction/22 2.200 35 2.80O

Mies (199iyGermany Induction/22 600 35

ThomaOMOyGtrmatty lnduction/2.2 160

Nakamara(I992)/Japan Inducu'on/Oj 5

Maub(1975yusA Arc/10 29,200

Large, SEC (I993J/USA Induction/20 2.200

Echols, SEG(l993yUS A Induction/20 2.740

Larsen(t965)/USA Induction/0 8 80

1 Adapted from Worcester < 1993).

- 137 - JAERl-Conf 95-015

The radioactive contaminants include fission and activation products, transuranic and uranium nuclides, and radioactive daughters. From a DOE perspective and considering the principal facilities involved in environmental cleanup operations, important radionuclides include the following elements: hydrogen, carbon, manganese, iron, cobalt, nickel, zinc, strontium, cesium, technetium, cerium, zirconium, ruthenium, tellurium, uranium, plutonium, and americium.

For considering the viability of melting RSM for recycling, the potential radiation doses that would be received by workers and others exposed to the scrap, primary and secondary wastes, and the final products (if radioactive) must be known. An early study of radiation exposures resulting from recycle of smelted radioactive metals was reported by O'Donnell and co­ workers (O'Donnell, 1978). Their generic methodology provides a framework that is applicable with modification to the melting of RSM. The dose calculations needed for recycling decision making will be accomplished through computer modeling and use of reported partitioning ratios for the radionuclides of interest. Radiological safety concerns could then be addressed through development of appropriate specifications for the recycled RSM. This review is intended to assess the present state of understanding and to identify data needs that should be addressed to evaluate the recycling of RSM for containers.

Melting of Radioactive Scrap Metal CRSM')

The melting of RSM for recycling into containers involves heating the metal to a molten state and permitting phase separation to occur. Depending on the thermochemical conditions, during the melting process, radioactivities will be redistributed in the melt, the insoluble (oxide) slag, the ceramic lining, dust, and vapor phase, as well as on other accessible surfaces. On cooling and separation from the other phases, the metal ingot is available for manufacture of the recycled metal products (e.g., a waste container). The ingot will contain lower concentrations (if any) of the initially present radionuclides since they would be homogeneously distributed throughout the metallic mass and would serve to attenuate any remaining radiation. The slag is the residue of the smelting procedure (typically, a few weight-percent of the total) and may contain larger or smaller concentrations of the nuclides than those present initially in the RSM, depending on the ability of the slagging process to remove small quantities of the radioactive contamination. The slag residue is characterized by having a homogeneously distributed radioactivity and attenuated radiation fields. Other radioactively contaminated products of the smelting would include the dust generated by the process, the refractory lining and other surfaces associated with the smelter, vapors (e.g., tritiated water), aerosols, scrubber liquors, and filter media. These materials, which typically constitute only 1-2 weight-percent of the total, would have to be disposed of as secondary wastes.

Several excellent reviews of melting of radioactive metals have been published (Worcester, 1993; Mautz, 1975; Reimann, 1991). A number of laboratory scale and large scale melt consolidation programs for RSM have been conducted over the past thirty years or so. A large degree of success has been achieved by the melting of radioactively contaminated ferrous metals for reducing concentrations of lanthanides, actinides, and most other fission products that are easily oxidized. On the other hand, melting to remove troublesome

- 138 - JAERl-Conf 95-015 transition elements from stainless steels, such as cobalt and technetium, has met with little success.

The technological community has selected two technologies for melting of ferrous RSM, coreless induction and electric arc furnace (EAF) melting. There are advantages and disadvantages for these technologies both of which are widely used in the steelmaking industry.

The induction melting technique is accounting for increasing tonnages of steel in the U.S. as improvements in solid-state frequency converters have increased operating efficiencies of the smaller units and as environmental standards have become more stringent. A coreless induction furnace contains a crucible or refractory lining surrounded by a water-cooled power coil through which electrical energy is applied. Very rapid heating and high melting rates are attainable with this design. Also, the induction currents stir the bath vigorously, which assures more uniform composition and temperature. Furnace capacities may range from a few pounds to 75 tons or more, with higher frequencies being required for the smaller furnaces. The main factors favoring coreless induction are the following: it offers better melt agitation; it offers easier fume control; and it allows rapid heatup. Also, an induction furnace reportedly produces only 20 percent as much effluent dust as an EAF of similar capacity (Reimann, 1991). This reduction of effluent dust can be a major factor in furnace selection for the melting of RSM.

Most of the stainless steel in the U.S. is produced by the three-phase direct EAF process. The EAF process also accounts for about one-third of the total U.S. raw steel production. The geometry of the furnace is such that it contains a large diameter, shallow melt with a large surface area which facilitates charging of scrap and the evolution of gases. The large surface area also contributes to increased bath oxidation. Larger arc furnaces have internal diameters of 30 feet or more and capacities of over 350 tons. Advantages of the EAF process include the following: it provides lower cost as heat sizes increase; it accommodates larger scrap section sizes; it allows for easier modification of melt composition; and it provides a greater margin of reliability and safety because of the absence of the water-cooled induction coil.

A modified melting technology, electroslag refining, has also been used to melt uranium and plutonium contaminated RSM (Ochiai, 1983; Uda, 1987). In this method, contaminated metal generally is melted in a molten slag in a mold by Joule heat generated with large amounts of electrical current and then gradually solidified in the same mold. For selected applications, success in partitioning of radioactivity between the metal and slag has been reported for this technology.

Successful melting of RSM requires fundamental understanding of the metallurgical and thermodynamic phenomena that undergird the process. Each type of metal or alloy requires a different treatment. Also, the crucible or refractory lining and slag composition, as well as the melting and pouring practice, must be specified. The slag chemistry selected for preferential removal of contaminants is achieved by small additions of fluxing agents, whereas the viscosity of the slag at operating temperature is controlled by the use of

- 139- JAERI-Conf 95-015 surfactants and diluents. Deslagging may be performed either manually or automatically with the aid of a flux trap during pouring; best results usually are obtained with the trap.

Many factors can influence the removal by slag of radionuclides from molten metal, including chemical stabilities of the radionuclides and their compounds, rates of compound formation, ease of entrainment of impurity compounds in the slag, and transportability of the compounds to the slag. An excellent discussion of the thermodynamic basis for removal of contaminants by melting has been given by Copeland and co-workers (Copeland, 1978). The Gibbs free energies of formation can be used as a guide for predicting removal of radionuclides during smelting. Figures 1 and 2 show the free energies of formation as functions of temperature for the oxides of groups VII and Vm and for Group V and the actinides, respectively. Elements for which the free energy of formation of the oxide is more negative than that for iron (c.f., - 57 kcal/gram-atom of oxygen for iron oxide at 300 degrees Kelvin) can be separated from steel by oxidation and partitioning into the slag layer under conditions of melt refining. Thus, smelting is effective in removing uranium from iron (as shown in Figures 1 and 2, the free energies of formation of the oxides of uranium and iron range from -124 and -57 kcal/gram- atom of oxygen, respectively).

Slagging agents (e.g., silica sand, lime, and magnesia) are usually added to the scrap metal during melting. The weight of added ingredients is typically about ten percent of the charge (scrap) weight, although lesser quantities may be used. Thus, if a radionuclide is removed completely from the scrap metal and is entrained in the slag, the concentration of the radionuclide in slag will be at least ten times the concentration in the original metal. The use of slags and experience with the various chemical and metallurgical factors affecting the partitioning of impurities between molten metals and slags has been reviewed by G. A. Reimann (Reimann, 1991).

Slags are classified as "acid" or "basic" according to the silicate degree or the basicity, depending on the slag's ability to react with the refractories as well as its ability to refine the underlying metal by selectively removing impurities. Slags high in silica are acid slags, while those high in metal oxides (e.g., CaO) are basic slags. These terms are rooted in observations of similarities in the behavior of aqueous solutions and oxide melts. In chemical terminology, an acid is generally considered to be any species that may accept an electron pair, while a base is any species that may donate an electron pair.

The effect of slag basicity on the residual uranium concentration of a mild steel ingot while other conditions were held constant (melt temperature of 1650°C; 30 minutes of melting; and a sample contamination level of 500 ppm) is shown in Figure 3. These results indicated a maximum decontamination effect around a basicity of 1.5 and were interpreted in terms of ionic interactions at the interface between the molten metal and the slag (Abe, 1985).

Published Results for Partitioning of Radionuclides by Meltine of Radioactively Contaminated Ferrous Metals

Over the past couple of decades, a considerable amount of work has been reported that could be applicable to campaigns for the partitioning of radionuclides by the melting of RSM.

- 140- JAERI-Conf 95-015

^M&>1 J? o"°V*

c c ° s. — >^ E ° v.

o >« o

iii

v — o O

300 500 1000 (.500 2000 2500 Temperofure (*K)

Figure 1. Free Energies of Formation for Oxides or Elements of Groups VII and VIII (Adapted from Copeland, 1978).

- 141- JAERI-Conf 95-015

L-VC2-

c e o a N'sO •- o — >N O X E ° o _ U. o -70

C I \- ;; o — c = UJ X -90 a) o it °

-110

-ieo

-140

300 500 1000 1500 2000 2500 Temperature (*K)

Figure 2. Free Energies of Formation for Oxides or Elements of Groups V and of the Activities (Adapted from Copeland, 1978).

- 142- JAERI-Conf 95-015

1I I FLUX

O Si02—CaO—Al203

A Si02—CaO—Al203—CaF2

• SiOg—CaO—AIP3—NiO

E ex a. 6 S c o ° \ O N _0 0 v

o \ / c

A • -2 10

1 0.5 1.0 1.5 2.0 2.5 3.0

Slag Basicity (-)

Figure 3. Effect of slag basicity (CaO+Nio or CaF2/Si02+Al203) on uranium concentration in a mild steel ignot (Abe, 1985).

- 143- JAERI-Conf 95-015

Pertinent radionuclides for which results have been published include tritium, cobalt, cesium, uranium, and plutonium.

One problem that is encountered when reviewing the RSM melting literature is failure of authors to provide sufficient details on testing conditions or to use consistent terminology when reporting experimental results. Some authors report partitioning results in terms of a decontamination factor (DF) which is defined as "amount" (mass) of impurity in the slag divided by "amount" (mass) of impurity in the metal ingot at equilibrium, as shown for impurity i in (1) below:

(1) DFj = mass; in slag/mass; in metal ingot

This is also commonly referred to as the partition coefficient, lambda.

Other authors report the reduction factor (RF) which is defined as the initial concentration of impurity i in the metal to its final concentration in the metal, as shown in (2) below:

(2) RFj = initial concentration in metal/final concentration in metal

A scientifically acceptable set of terms should be used by all workers in the field so that results could be readily interpreted in the context of underlying thermodynamic/kinetic descriptions.

A discussion of the theoretical basis for partitioning of impurities between slag and molten metal was given by Copeland and co-workers (Copeland, 1978). Based on thermodynamic data and using several assumptions, they calculated partition ratios for several elements in iron melts at 1530°C. Their results are given for four elements of interest in Table 2. Due to uncertainties in the calculations, these results can be taken only as order-of-magnitude numbers but the relative values are significant. The results predict that uranium and plutonium impurities should be readily separable from iron and steels by melting with slag, while cobalt and technetium impurities would tend to remain in the metal ingot.

Table 2. Partition Ratios for Oxide Slags Tor Several Contaminant in Iron Melts at 1530°c1

Uranium io'i

Plutonium 108

Cobalt 10-5

Technetium I0"8

'Partition ratio is defined as mass of conlaminant in the slag divided by the mass of contaminant in melt at equilibrium. Results of calculations by Copeland and co-workers (Copeland. 1978).

- 144 - JAERI-Cont" 95-015

The expected behavior of tritium during melting of ferrous metals is to escape as an aerosol. Tritium may be present in either the oxide layer or be incorporated into the metallic lattice of contaminated metals. On melting stainless steel containing tritium, it was observed that tritiated water was quantitatively transferred to liquid nitrogen traps (Shenker, 1986).

Cobalt-60 is a principal activity in steelwork from decommissioned nuclear power plants. Its behavior in melting of radioactively contaminated steel was studied by several groups in the first Commission of European Communities (CEC) program on decommissioning (CEC, 1986). The findings of several groups was that cobalt partitioned almost entirely to the steel, which is consistent with general experience and the thermodynamic properties of cobalt in steelmaking. However, some investigators reported that, in induction furnaces, 25 percent or more of the cobalt-60 was present in the slag under some circumstances. Testing by British Steel (Harvey, 1990) confirmed that cobalt-60 could be present in the slag initially but that its concentration tended to decrease with time and the transient presence of cobalt-60 was likely to be dependent on slag viscosity. For the viscous or semi-solid slag found in the induction furnace, metallic globules might be retained until the end of the process. However, in the arc furnace and basic oxygen steelmaking vessel, slags are fluid so that residence times of metallic globules would be short and cobalt-60 should not normally be found in the slag.

The behavior of cobalt-60 in basic oxygen steelmaking was investigated in the United Kingdom (Harvey, 1990). Steel plates containing cobalt-60 were included in the raw materials and the oxygen blowing process was performed in the normal way. Cobalt-60 was found to remain with the steel, demonstrating that even under powerfully oxidizing non- equilibrium conditions the formation of cobalt oxide is not favored. Kinetic factors apparently do not outweigh thermodynamic factors and this process could be used to melt steel contaminated with cobalt-60 with confidence that the slag and fume would not become secondary wastes.

The reported experiences with cobalt-60 emphasize that practical considerations are important in the melting of ferrous RSM. The precise separation of slag from the steel is generally not possible. Rather, the physical actions involved in pouring the steel from the furnace will inevitably result in some mixing of the steel and the slag. And, therefore, the steel produced from the process will contain some traces of slag, and the slag will contain some traces of the steel. Because of these problems, there are practical limits to the retention of radioactivity in the steel ingots.

Cesium radionuclides are another main contaminant in steel from decommissioning. Its behavior in RSM melting is dependent on the particular conditions (Harvey, 1990). Cesium can be partially absorbed by an acidic slag, but very little is absorbed by a basic slag. These characteristics are evident in the arc furnace, but in the induction furnace where the slag is not fully melted the results tend to be erratic.

Over 30,000 tons of uranium contaminated steel were melt-slag processed up to the mid- 1970s. Uranium concentration varied but was generally less than 10 parts per thousand. Residual uranium concentrations were about 15-45 percent of the starting concentrations. Approximately 2.5 kg of plutonium contaminated steel was melt-slag processed in small

- 145 - JAERl-Conf 95-015 batches (less than about 200 g per batch). Residual plutonium content varied but reduction factors of up to 200 were achieved. Important details (e.g., slag chemistry, starting contaminant concentration, furnace design, operating parameters) necessary to assure reproducibility and to establish process capability limits are generally lacking in the referenced documentation. Using various slags, reduction factors of uranium in ferrous metals of 1,000 or more have been reported (Uda, 1982; Heshmatpour, 1981a), and similar results have been reported for plutonium in ferrous metals (1981b).

Based on our review of the literature, it appears that melting conditions can be established to effect the separation of H-3; C-14; Sr-90; Cs-134,137; Zn-65; U-235,238; and Pu-239. Radionuclides expected to remain in the melt include Mn-54; Ni-63; Co-60; and Fe-55. In general, major contaminants can be separated into four groups (Bechtold, 1993): 1) elements that remain in the melt, 2) elements that form high-temperature intermetallics in metal and slag (e.g., Ce-144), 3) elements that oxidize and partition to the slag (e.g., Sr-90; U-235,238), and 4) elements that vaporize and report to the off-gas system (e.g., Cs-134,137; Zn-65).

Partitioning and Other Data Needed for Deciding Recycling Options for Radioactively Contaminated Ferrous Metals

Our review of the literature on this subject has led to the conclusion that certain gaps remain concerning our knowledge of partitioning of radioactivity when melting ferrous RSM. The existing data base on RSM at DOE sites, including projected values for decommissioning of facilities and the environmental remediation of sites, is incomplete. The present effort should be supplemented by a more comprehensive review based on revisions in the DOE's data base on RSM.

An understanding of the redistribution and stabilization of radioactivities in RSM and slags during melting is important for the possible recycle of contaminated materials. For dose calculations of the various recycling options, it is essential to have credible and applicable partitioning data for each treatment scenario. Such data exits only in sketchy form and only for a few radionuclides (e.g., of the elements uranium, plutonium, and cobalt). There is need for additional data on most of the key radionuclides in DOE's inventory of RSM, including data on partitioning, speciation, and applicable chemistries, and such data need to be obtained under controlled conditions so that thermodynamic/kinetic predictions can be made. The acquisition of thermodynamic data will permit optimization of the candidate processes.

In a recycling program of national scale, there will be a large variety of contaminated metals some of which will require treatment with different slags and different melting processes. It will be essential to control the thermochemistry of such processes and the effects of the chemical makeup of feed materials are crucial in this regard. Also, the optimal sizing of melting heats to minimize radionuclide characterization and analytical costs while casting the material into suitable forms for recycling will be required in order for the program to be cost- effective.

Data on the microscopic distribution and speciation of radionuclides in RSM are lacking. Furthermore, the effects of subsequent treatments after melting (such as the rolling, milling,

- 146- JAERl-Conf 95-015 and welding processes associated with manufacture of new items) on the radioactivities remaining in the purified metals have not been studied at all.

RSM will require pretreatment, some of which could be extensive, prior to melting. These may include chemical/physical decontamination of surfaces, segregation according to base metal, segregation according to radionuclide contaminant chemistry and other properties, and size reduction/compaction and sorting as required for furnace loading.

Studies culminating in the design of an integrated process for feed pretreatment/preparation and control of gaseous effluents should be initiated. These studies must include attention to mechanical methods capable of operation within containment to assure that there is adherence to the as-low-as-reasonably-achievable (ALARA) principle of radiological and worker safety.

The key issues to be addressed in implementing a recycle program of any magnitude RSM include the following:

establishment of a credible database on DOE's inventory of RSM (current and projected), including chemical, physical, and radioactive characteristics

determination of radioactive partitioning between the metal and slag phases under controlled conditions

operability of the candidate process, subject to widely varying feed chemistry and conditions and environmental protection requirements

effective modeling of radiation exposures to workers and others throughout the recycling process

While many reports on the melting of RSM and subsequent partitioning of radioactivities have been published, most of the reported work was not done under controlled conditions and no useful thermodynamic data were obtained. These is a need for such data on the expected contaminants in ferrous metals and various slags which would be used in melting campaigns. At the very least, the partition ratios for key radionuclides in given slags must be determined. A credible and comprehensive data set will be required if a large-scale recycling program for ferrous RSM is to be implemented.

Along with the needed thermochemistry studies, it would be desirable to construct a pilot facility equipped with the appropriate gas cleaning and handling system to demonstrate the candidate processes. The system of choice would probably consist of an inductive heating furnace equipped with a gas tight system.

- 147- JAERI-Conf 95-015

References

M. Abe, T. Uba, and H. Iba, "A Melt Refining Method for Uranium Contaminated Steels and Copper," pp. 375- 379 in Volume 3 of the Proceedings of the Symposium on Waste Management at Tucson. Arizona. March 24-28. .1985. Roy G. Post, Editor, 1985.

T. E. Bechtold (Editor), Winco Metal Recycle Annual Report FY 1993. Westinghouse Idaho Nuclear Company, Inc., Idaho Falls, Idaho, December 1993.

CEC Report, "Melting and Recycling of Radioactive Metals from Decommissioning of Nuclear Installations," Proceedings of a Commission of European Communities Workshop. Karlsruhe, Federal Republic of Germany. May 27-28. 1986 [referenced by Harvey, 1990}, 1986.

G. L. Copeland, R. L. Hecstand, and R. S. Matccr, "Volume Reduction of Low-Level Contaminated Mew! Waste by Melting - Selection of Method and Conceptual Plan," ORNL/TM-6388, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1978.

R. Echols, SEG, Oak Ridge, Tennessee [referenced by Worcester (1993)], 1993.

C. R. Gomer and J. T. Lamblcy, "Melting of Contaminated Steel Scrap Arising in the Dismantling of Nuclear Power Plants," EUR-10188, Commission of the European Communities, 1985.

D. S. Harvey, "Melting of Contaminated Steel Scrap from Decommissioning," pp. 473-481 in Decommissioning of Nuclear Installations, Proceedings of the 1989 International Conference. Brussels. Belgium. October 24-27. 1989. Elsevier Applied Science, Barking, United Kingdom, 1990.

B. Heshmatpour and G. Copeland, "The Effects of Slag Composition and Process Variables on Decontamination of Metallic Wastes by Melt Refining," ORNL/TM-7501, Oak Ridge National Laboratory, Oak Ridge, Tennessee, January 1981a.

B. Heshmatpour, G. Copeland, and R. Heestand, "Decontamination of Transuranic Waste Metal by Melt Refining," ORNL/TM-7951, Oak Ridge National Laboratory, Oak Ridge, Tennessee, December 1981 b.

D. Large, SEG, Oak Ridge, Tennessee [referenced by Worcester (1993)], 1993.

M. M. Larsen, J. N. Davis, and J. A. Logan, "Sizing and Melting Development Activities Using Contaminated Metal at the Waste Experimental Reduction Facility," EGG-2411, Idaho National Engineering Laboratory, Idaho Falls, Idaho, February 1985.

E. W. Mautz, G. G. Briggs, W. E. Shaw, and J. H. Cavendish, "Uranium Decontamination of Common Melals by Smelting: A Review (Handbook)," NSA3204, National Lead Company of Ohio, Cincinnati, Ohio, February 1975.

S. Menon, G. Hernborg, and L. Anderson, "Melting of Low-Level Contaminated Steels," Decommissioning Nuclear Installations - 1990. Studsvik AB, Sweden, 1990.

H. P. Mies and W. Stang. "Decommissioning of Nuclear Power Plant Gundremmingen Unit A," Kcrnkraftwerkc Gundremmingen Betricbsgesellschaft, Germany, 1991.

H. Nakamura and K. Fujiki, "Radioactive Metal Melting Test at Japan Atomic Energy Research Institute," Japan Atomic Energy Research Institute, Tokai-mura, Naga-kun, Ibaraki-kcn, Japan, 1992.

A. Ochiai, K. Kitagawa, Y. Sawada, S. Izuhara, and K. Ohtsuka, "Treatment of Plutonium-Contaminated Metallic Waste by the Electro-Slag Melting Method," pp. 177-190 in Conditioning of Radioactive Wastes for Storage and

- 148- JAERI-Conf 95-015

Disposal. Proceedings of an International Svmposium.Utrecht. Netherlands. June 21-25. 19S2. IAEA-SM-261/20, 1983.

F. R. O'Donnell, S. J. Cotter, D. C. Kocher, E. L. Etnier, and A. P. Watson, "Potential Radiation Dose to Man from Recycle of Metals Reclaimed from a Decommissioned Nuclear Power Plant," ORNL/NUREG/TM-215, Oak Ridge National Laboratory, Oak Ridge, Tennessee, December 1978.

J. Peulve, "Treatment of Dismantled Materials by Fusion," Techno-992-022 [referenced by Worcester (1993)], 1992.

G. A. Reimann, "Technical Assessment of Processes to Enable Recycling of Low-Level Contaminated Metal Waste," EGG-MS-9879, Idaho National Engineering Laboratory, Idaho Falls, Idaho, October 1991.

E. Schenker, W. Francioni, and G. Ullrich, "Laboratory Scale Melting of Contaminated Metallic Scrap," Proceedings of Commission of European Communities Workshop on Melting and Recycling of Radioactive Metals from Decommissioning of Nuclear Installations. May 27-28. 1986. Karlsruhe, Federal Republic of Germany, 1986.

T. Uda, Y. Ozawa, and H. Iba, "Melting of Uranium-Contaminated Metal Cylinders by Electroslag Refining," pp. 328-337 in Nuclear Technology. Volume 79, December 1987.

S. A. Worcester, L. G. Twidwell, D. J. Paolini, and T. A. Weldon,"Decontamination of Metals by Melt Refining/Slagging - An Annotated Bibliography, WINCO-1138, Westinghouse Idaho Nuclear Company, Inc., Idaho Falls, Idaho, July 1993.

- 149-