WASTE MANAGEMENT ASPECTS OF LOW ACTIVATION MATERIALS

Transcription

1 WASTE MANAGEMENT ASPECTS OF LOW ACTIVATION MATERIALS E.T. Cheng P. Rocco 1, M. Zucchetti 1,2 Y. Seki, T. Tabara 3 TSI Research, Inc. 1 European Commission - JRC JAERI 225 Stevens Avenue Institute for Advanced Materials Mukouyama Solana Beach, CA T.P.800, I Naka-machi, Naka-gun USA Ispra (VA), Italy Ibaraki-ken , Japan 2 Polytechnic of Torino, Energetics Department, C.so Duca degli Abruzzi 24, I Torino, Italy 3 Sumitomo Atomic Energy Industries, Ltd., , Ryogoku, Sumidaku, Tokyo, 130 Japan ABSTRACT Low activation materials are attractive for the development of fusion power plants because of their advantages in environmental and safety concerns. The waste management aspects of fusion power plants constructed using candidate low activation materials, namely vanadium alloy and RAFS were reviewed. The objective of this review is to (1) understand the present tendency of waste management strategies being developed in the U.S., European Union and Japan, (2) identify consensus and discrepancies in determining these strategies, and (3) recommend joint effort in establishing an high quality and internationally acceptable strategy. I. INTRODUCTION Low activation materials are attractive for the development of fusion power plants because of their advantages in environmental and safety concerns. These advantages include elimination or reduction of the quantity of high level waste to be disposed of as geologic disposal waste, possible reuse of the reactor materials after recycling, and enhancing simple and safe management of radioactive materials from fusion power plants. Management of the discharged first wall and blanket components has been one of the important considerations motivating the development of low activation fusion materials. 1 The issues in handling fusion waste materials include: (1) transportation of discharged components to a permanent storage or recycling site, (2) burial disposal of waste materials, and (3) recycling of decommissioned materials if practical. Note that transportation of discharged reactor components without a radiation shield will require a limiting contact dose rate of 2 msv/h. 2 Previous studies show that it is not likely that within the lifetime of the power plant the contact dose rate of the first wall and blanket components would drop below the limiting value. 3 A gamma radiation shield is therefore needed if these discharged components are to be transported outside of the plant site within the lifetime of the power plant. Development of low activation structural materials has recently narrowed down to two metallic alloys, namely the reduced activation ferritic steel (RAFS), or low activation martensitic steel (LAMS), and vanadium alloy, and a ceramic composite, SiC. These low activation materials are generally to be handled as near-surface waste after discharge from power reactors, despite the fact that whether the near-surface disposal is an acceptable option depends entirely on the region that sites the power reactors. Impurities have been identified as an important factor for the low activation materials to qualify as near-surface disposal waste. 1 Efforts were recently devoted in establishing the concentration limits of natural elements in the low activation materials. 3 Recycle of used reactor materials, particularly hands-on process, appears to be more attractive than the burial disposal, although the perfect situation is to allow all materials to be freely reusable without restriction. 3-5 Impurities again play an important role in determining the extent that the used materials can be recycled. Cooling time is another factor. 3 In this paper, we examine the waste management aspects of fusion power plants constructed using candidate low activation materials, namely vanadium alloy and RAFS. The objectives of this review are to (1) understand the current tendency of the waste management strategies being developed in the U.S., E.U. (European Union) and Japan, (2) identify consensus and discrepancies in determining these strategies, and (3) recommend joint effort in establishing an high quality and internationally acceptable strategy. ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 1

2 Table I Tendency of Waste Management Strategy in the U.S., E.U., and Japan with respect to Fusion Power Plant Development Country Geologic Disposal Near-surface Burial Materials Recycling Clearance (Freely Releasable) /Region Disposal U.S. Avoided the need for geologic disposal Strongly encouraged Proposed application with rules (Below Regulatory Concern) Highly recommended 10CFR61 Class C Fetter SALs (0.6 msv/h>d>10 psv/h) b (D<25 µsv/h HOR; D<10 msv/h RHR) D > 0.6 msv/h a (D<0.1 msv/y or 10 psv/h) EU Reduced quantity Generally not acceptable Highly recommended Proposed application with rules Possibly substituted D <10 µsv/h HOR Derived from the proposed by recycling D <10 msv/h - RHR IAEA Clearance Index Japan Avoided the need for Highly recommended Strongly encouraged Applied with rules geologic disposal LLW and MLW Nuclear Safety Commission a. The contact dose rate from a gamma-emitting radionuclide (such as Nb94) is about 0.6 msv/h when its concentration is at the specific activity limit for 10CFR61 Class C waste. b. The contact dose rate of 10 psv/h is equivalent to 0.1 msv/y. The organization of this paper is as follows. Section II reviews the recent studies relevant to waste management strategies in the U.S., E.U. and Japan. An illustrative analysis using two power plant models is given in Sec. III for a proposed E.U. strategy. Section IV discusses the issues and consistencies relevant to applicability and regulatory values. Finally, conclusions and recommendations are presented in Sec. V. II. WASTE MANAGEMENT STRATEGIES Based on our understanding from the various power plant studies and assessments, 3-9 we have summarized in Table I the waste management strategies being developed in the U.S., E.U. and Japan. Limiting values of gamma dose rate or its equivalent are also shown when available. A. U.S. Strategy The U.S. strategy tends to emphasize the near-surface burial disposal and eliminate the need for geologic disposal. Materials recycling, particularly hands-on, is also strongly encouraged. The concept of freely releasable materials is already established (below regulatory concern), although it has not been yet officially adopted by law. 10,11 The concept of below regulatory concern should be taken into consideration since a large part of the plant will fall into that category after decommissioning. The guideline used for near-surface waste disposal is the regulations determined by the United State Nuclear Regulatory Commission, 10CFR Since a majority of radioactive materials generated in fusion contain radionuclides with relatively long half-lives such as Nb94 (half-life 2.03x10 4 y), a waste classification of Class C should be considered. Under the USNRC 10CFR61 regulations, the site for near-surface disposal of radioactive waste, which is buried below 5 m and within approximately 30 m of the earth s surface, has to maintain institutional control for 100 years and intruder barriers effective for 500 years. The Class C waste has to be stable, maintaining gross physical properties for 300 y. The nearsurface disposal is guided by a given set of specific activity limits (SAL) for the concerned radionuclides. These SALs are determined based on a given methodology taking into account the direct gamma exposure from gamma emitting radionuclides, and inhalation and ingestion of beta emitting radionuclides. Corrosion of waste materials and migration of the corroded radioactive material to the surface of the disposal site are important considerations for the beta emitting radionuclides. The ultimate goal of the near-surface disposal is to assure acceptable public health and safety after 500 years under the following annual dose limits: 0.25 msv/y whole body, 0.75 msv/y thyroid, and 0.25 msv/y any other organ of the member of the public. 12 Note that the annual whole body dose limit of 0.25 msv/y is a factor of 4 lower than the effective dose limit recommended by the 1990 ICRP. 13 The safety objectives of the 10CFR61 near-surface disposal of radioactive materials are (1) protection of the general population from release of radioactivity, (2) protection of individuals from inadvertent intrusion, (3) protection of individuals during operation, and (4) ensurance of stability of the site after closure. 12 The current 10CFR61 regulations provide the SALs for radionuclides generated in a fission power plant. These radionuclides are limited to C14, Ni59, Ni63, Sr90, Nb94, Tc99, I129, Cs137, alpha emitters, and actinides. A ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 2

3 complete set of SALs, including all existing radionuclides with half-lives greater than 5 y, has been evaluated by Fetter et al. 14 based on 10CFR61 methodology. The 10CFR61 and Fetter evaluations agree remarkably when the annual intruder dose above the earth s surface is due to the external exposure from the gamma-emitting radionuclides such as Nb94. However, if the intruder dose is dominated by internal radiation, i.e., by inhalation and ingestion of beta(and alpha)-emitting radionuclides such as Ni63, the difference between 10CFR61 and Fetter evaluations can be large. This is because the 10CFR61 SALs were based on a worst case waste form, while for the majority of fusion wastes the radionuclides would be embedded in metal. The reduction due to the added stability of metal waste can be much greater. The NRC decided not to develop separate regulations for activated metal waste because such wastes currently represent a small fraction of the total waste stream. 14 Since fusion would generate a significant amount of activated metal waste, the NRC position must be reevaluated. B. A PROPOSED EUROPEAN UNION STRATEGY The long-term action on safety and environment of the European Fusion Technology Programme is SEAFP- 2 (Safety and Environmental Assessment of Fusion Power, Phase 2), which continues activities of previous actions SEAFP 15 and SEAL. 16 The SEAFP-2 study investigates two major safety items: a) containment, to minimize release in worst accidents, b) waste management, to minimize repository volumes and hazards. There were two studies completed concerning waste management. One assessed the implications of disposal of fusion waste disposal in existing or planned repository for fission waste. 17 The other, which is particularly attractive for fusion reactor designs adopting low activation materials, analysed the feasibility of recycle for the irradiated in-vessel materials and of clearance for the exvessel materials. The present strategy envisages an interim storage of the activated material for 50 years at the reactor site, then depending on the residual radioactivity, materials may be: a) recycled, i.e. re-used in the nuclear industry, b) cleared, i.e. declassified to non-active waste (NAW) and released from the regulatory control, c) disposed of as radioactive waste if conditions for a) and b) are not fulfilled. Radiological feasibility of recycling is assumed to depend on the contact dose rate D of the waste. Also, it is not defined whether recycling includes purification of noxious nuclides or residual radioactivity remains as it is and the new pieces are handled by remote operation. It is assumed: (a) D-limit for recycling is 10 msv/h, beyond which waste has to be disposed of as fission waste, (b) Recycling by remote handling (RHR) is feasible in the range 10 µsv/h < D < 10 msv/h, with different grades of shielding precautions. Hands-on recycling (HOR) is feasible for D not greater than 10 µsv/h, in compliance with the 1990 ICRP Recommendations. 13 In this way the annual dose (40 hours per week, 50 weeks) to workers will be 20 msv, a reduced value in comparison to the old 50 msv which is due to 25 µsv/h. Noted that the same D limits were assumed in SEAL, 16 whereas in SEAFP 15 D limits for RHR and HOR were 20 msv/h and 25 µsv/h respectively, and (c) Waste arising from ex-vessel zones may be cleared if the specific activity is sufficiently low. Table II Clearance levels L c adopted in SEAFP-2 analyses Nuclide Half Life, y L c, Bq/kg Nuclide Half Life, y L c, Bq/kg H E5 Ag min 6E2 Be E6 4E3 Ni E5 C E4 Nb-93m E4 Al E5 4E2 Nb E4 3E2 Si E3 Mo E3 9E3 Cl E5 3E4 Tc E5 3E3 K E9 1E3 Ag-108m 127 6E2 Ca E5 7E4 Ag-110m E2 Mn E6 6E4 Sn-119m E3 Fe E4 Sb-125m E3 Co E2 Ir E3 ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 3

4 Ni E4 3E4 Ir-192m 241 1E3 Nb E3 Kr E3 Ar E5 Ar E5 Bi E5 3E2 Po E2 SEAFP analyses 15 took 400 Bq/kg as a limit for clearance, same value as the limit for Very Low Level Waste of the British Regulation, 18 disregarding the waste composition. However, some natural substances (e.g. concrete, fertilizers) may have activities ranging between 1,000 and 4,000 Bq/kg. In the present analyses, the feasibility of clearance is evaluated taking into account the potential hazard of each nuclide contributing to the specific radioactivity of the waste. Unconditional clearance levels of nuclides, i.e. activity limits allowing clearance of a waste containing this nuclide as only contaminant, may be mostly found in an IAEA proposal, 19 where they are derived from safety analyses of waste repositories. Levels of nuclides not directly given may be evaluated with a fitting formula, which takes into account the potential hazard: gamma and/or beta energy of the emission, limits of intake by inhalation and ingestion. Clearance levels as defined previously were adopted in SEAL, whereas that used in SEAFP-2, have been further reduced by safety factors, namely: a) clearance levels smaller than 1,000 Bq/kg remain unchanged, b) those between 1,000 Bq/kg and 10,000 Bq/kg are reduced to 1,000 Bq/kg, c) those greater than 10,000 are reduced by a factor 10. Table II shows the clearance levels for the most important nuclides in fusion activated materials. 20 C. JAPANESE STRATEGY The tendency in Japan is to adopt the shallow-land (nearsurface) concrete pit burial disposal if the subject fusion waste can qualify as low level waste (LLW) as defined by the Nuclear Safety Commission (NSC) for the fission waste (HLW is referring only to fission waste). 5 Limiting concentrations for fusion relevant radionuclides were derived using the methodology employed by the NSC for the fission waste assuming an upper dose limit of 0.1 msv/y. Radioactive waste is also classified as medium level waste (MLW). MLW is the waste that does not qualify as LLW because one or more of the radionuclides exceed the derived limiting concentrations for LLW. The disposal of MLW is, however, similar to that of LLW although it requires a depth more than 50 m below the surface. It is noted that only LLW waste disposal is actually put to practice at present and the above mentioned disposal method for MLW is being proposed at this time for any fusion waste which can not qualify as LLW. The clearance level of waste is also under consideration recently in Japan. The waste from the two plant models, PM-1 and PM-2 of SEAFP-2 described below, has been evaluated using the LLW criteria in Japan. The results showed that about 67 wt% of the waste from PM-1 and 76 wt% from PM-2 qualified as the LLW. III. ILLUSTRATION AN EUROPEAN UNION ANALYSIS The recycling and clearance concepts described previously have been applied to two SEAFP-2 plant models (PMs), PM-1 and PM-2. Each PM is a 3,000 MW(th) tokamak and has a unique design for the blanket-divertor systems but is assumed to be identical for all other components. PM-1 and PM-2 have in-vessel structural materials and breeder-coolant systems made, respectively, with: V-4Cr- 4Ti and Li 2 O-helium (PM-1), and low-activation martensitic steel (LAM) and Pb17Li-water (PM-2). Their features are tabulated in Table III. They are fully described in Ref. 21 including detailed elemental compositions of all materials. Activation levels are determined from those evaluated in Refs. 22 and 23, using FISPACT, 24 with 1-D neutron fluxes as inputs, a mean neutron wall Loading of 2 MW/m 2 and continuous irradiation of 5 years, 25 years, 15 months for in-vessel-, ex-vessel-zones and divertor respectively. Table III Components and materials of PM-1 and PM-2 Component PM-1 PM-2 In-vessel structures Breeder/blanket coolant Divertor Shield Vacuum vessel V-4Cr-4Ti Li 2 O ceramic pebble bed/ helium Be armor V-4Cr-4Ti heat sink Helium coolant AISI % water Low-Act. Martensitic Steel Pb-17Li/water Be armor Copper heat sink Water coolant AISI 316, water, lead, boron carbide ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 4

5 Toroidal field coils AISI 316 structure Nb-Sn superconductors Copper conductors Helium coolant Glass and epoxy insulator lowest in percent due to the large weight of the Pb-17Li breeder, which should be recycled). The inboard shield, with its high radioactivity and relevant volume, is a critical component, due to its long exposure (25 years). As shown below, substitution of AISI-316 with a low activation steel, such as OPTSTAB, could be a proper solution. Table IV summarises the results for SEAFP-2 power plants. It is seen that PM-2 shows the most favourable behaviour. All in-vessel materials are recyclable, even the LAM first wall steel and the Pb-17Li breeder. Conversely, although using a vanadium alloy commonly considered a low-activation material, PM-1 obtains worse results. The first wall and the inboard shield materials, V-4Cr-4Ti and AISI 316 respectively, are not recyclable. They are 1,850 tonnes of High-Level waste, 3.2% of the total. The long term activation of the vanadium alloy is almost entirely due to the presence of Bi-207 and Bi-208. As shown below, if those nuclides were reduced limiting the parent element bismuth, the performance of the vanadium alloy would improve dramatically. Note that no in-vessel material can be hands-on recycled or cleared. Results may be summarised below: (a) PM-2 - no material has contact dose rates beyond the recycling limit, twothirds (66 wt%) of materials can be recycled, one-third (34 wt%) can be cleared, (b) PM-1 - about one half (52 wt%) of materials can be recycled, nearly one half (45 wt%) can be cleared, however about 3 wt% has to be disposed of as high level waste, and (c) PM-1 results may be improved as seen in PM-1 (Opt.). The long term radioactivity of a V-4Cr- 4Ti alloy may be made fold lower than that of the reference alloy with a reduction of the impurities, in particular bismuth. Similarly, AISI 316 adopted in the shield and vacuum vessel could be advantageously substituted with OPTSTAB. In this way, no material has to be disposed of and both fractions of recyclable and clearable materials increase. Table IV Disposal, recycling and clearance of waste (in units of metric tons) arising from PM-1 and PM-2, and from a material-optimised version of PM-1 Waste Management Option PM 1 & wt% Disposal 1, % Recycling (RHR + HOR) Clearance (NAW) Total activated waste (operation + decommission) 29, % 25, % 57, % PM 2 & wt% , % 26, % 77, % PM - 1 (Opt.) & wt% 30, % 26, % 57, % The outboard toroidal field coils and also the gamma shield can be declassified to NAW in both models. In PM- 2, part of the inboard magnets and of the outboard vessel can also be cleared. This is due to the better shielding capabilities of the PM-2 blanket, an effect which was also found before in the feasibility of recycling for the inboard shield material in this reactor. For PM-2, the quantity of material which can be cleared is the highest (it is the IV. DISCUSSIONS The clearance levels adopted in the SEAFP-2 study are generally more than one order of magnitude higher than the U.S. beyond regulatory control regulations (<0.1 msv/y), as shown in Table V for several important radionuclides. Impurities play a very important role in determining the waste category. This is again demonstrated in the E.U. analysis. All first wall and blanket materials discharged from PM-1 (optimized) and PM-2 may qualify for remotehandling recycling (<10 msv/h) because the demand for the impurity level is modest. The impurities identified in the SEAFP-2 study are far above the levels required for near-surface burial according to the U.S. regulations (<0.6 msv/h) and the more attractive hands-on recycling (<10 µsv/h). This is illustrated in Table VI. As seen in Table VI, the activity levels compatible with hands-on recycling can only be achieved by a very low level of impurities, such as 2 wppm for Ag and 0.7 wppm for Tb. The activities of some radionuclides, however, cannot be reduced properly by acting on the concentration of parent nuclides, either because the levels required are below the detection or technological limits, or because the parent nuclides are components of the alloy. In these cases, ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 5

6 activity level suitable for hands-on recycling or beyond regulatory control could be attained by diluting the noxious radionuclides when reprocessing the irradiated materials to remove the decay products. The elemental dilution could be achieved by adding stable isotopes of the same element and then extract the stable isotopes + the noxious nuclides. 11,20 It may be shown that the secondary waste stream would be tiny and easily managed. Table V Comparison of Proposed IAEA + SEAFP-2 Clearance Levels and U.S. Beyond Regulatory Control Regulations Isotope U.S. BRC ( 0.1 msv/y) Clearance Level (IAEA Proposal + SEAFP-2) Dose Rate Ratio Ci/m 3 Bq/kg Ci/m 3 Dose rate (msv/y) (IAEA/U.S.) Al x10-6 4x x Nb x10-6 3x x Ag108m 3.53x10-6 6x x Bi x10-6 3x x Table VI Comparison of Concentration Limits and Impurities in SEAFP2 V-4Cr-4Ti Structural Materials (wppm) Element V-4Cr-4Ti RHR# HOR# NSB# Ag Al 200 7, Bi * 0.02* 2 Cd N/A 1, Co N/A 1,000* 1* 1.9w/o Cu w/o* 16 7w/o Dy N/A Er N/A Eu N/A 0.4* * 350 Hf * 0.75* N/L Ho N/A Ir N/A Mo 50 1, N 200 N/L N/L 180 Nb Ni 1.2 3w/o* 30* 1.5w/o Os N/A 2, Pd N/A Pt N/A 9w/o Re N/A 31w/o 310 3,200 Si 500 N/L 1.6w/o N/L Ta w/o* 550 N/L Tb N/A Ti 4w/o N/L 1,400* N/L W w/o 280 N/L Zr w/o 690 2,800 RHR:Remote handling recycling; HOR:Hands-on recycling; NSB:Near-surface burial. # Limiting concentrations were 1/10 of those derived in Ref. 25 to account for the collective effect of all existing impurities. *Higher concentration limits are possible with longer cooling time. V. CONCLUSIONS AND RECOMMENDATIONS We have examined the recent waste management tendencies for future fusion power plants in the U.S., E.U. and Japan. Illustration and comparison of waste quantities and management strategies were made using two power plant models developed under an EU study. Discrepancies in concentration limits with respect to regulatory issues were found and discussed. Several conclusions and recommendations are given below as a result of this review: - Clearance or beyond regulatory control will significantly reduce the quantity of materials to be recycled or buried. However, a consistent and internationally acceptable set of limiting concentrations for all long-lived radionuclides should be developed. - Reuse of activated reactor components after recycling should be encouraged over burial disposal. Hands-on recycling is preferred if impurities can be controlled. - Near-surface burial disposal is ideal for waste involving only shorter-lived radionuclides with half-lives shorter than a few hundred years. The regulation of 10CFR61 ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 6

7 Class C involving long-lived radionuclides such as Nb94 (half-life 20,000 y) should be re-examined. - Geologic disposal involving tiny quantity of concentrated radioactive materials is perhaps an unavoidable waste management option. It is needed to facilitate the use of exotic materials for the successful and safe operation of the power plant. It may also be needed to dispose the tiny amount of radioactive material encountered during recycling. Finally, to accurately assess the waste management strategy for a fusion power plant, we believe it is essential that the accurate activation characteristics of all reactor materials are provided. Factors important for obtaining the activation characteristics include (1) complete elemental compositions of all reactor materials, (2) accurate description and modeling of the reactor configuration, and (3) reliable nuclear database for neutron transport and activation calculations. ACKNOWLEDGEMENTS PM-1 and PM-2 activation data were derived from analyses done by R. Forrest and C. Forty, UKAEA Fusion, Culham, UK. Component weights were evaluated by K. Broden and M. Lindberg, Studsvik Radwaste, Sweden. We were grateful for the suggestions of the reviewers, particularly in correcting issues associated with regulations in the U.S. Part of this work was supported (for TSI Research) by the U.S. Department of Energy, Office of Fusion Energy Sciences, Grant No.: DE-FG03-92ER REFERENCES 1. R. Conn, et al., Lower Activation Materials and magnetic Fusion Reactors, Nuclear Technology/Fusion, 5, 291 (1984). 2. Code of Federal Regulations, Title 10 Energy, 10CFR20, Standards for Protection Against Radiation, U.S. Federal Register, Revised January 1, E.T. Cheng, Concentration Limits of Natural Elements in Low Activation Materials, ICFRM-8, Sendai, Oct. 1997, to be published in J. Nucl. Materials. 4. P. Rocco and M. Zucchetti, Advanced Management Concepts for Fusion Waste, ibid. 5. Y. Seki, T. Tabara, et al., Impact of Low Activation Materials on Fusion Reactor Design, ibid. Also see Y. Seki, T. Tabara, et al., Composition Adjustment of Low Activation Materials for Shallow-land Disposal, IAEA- TCM Fusion Power Plant Design, March 1998, Culham, U.K. 6. E.T. Cheng, et al., Materials Recycling Considerations for D-T Fusion Reactors, Fusion Technology, 21, 2001 (1992); also see references cited in this paper. 7. T.J. Dolan and G.J. Butterworth, Vanadium Recycling, Fusion Technology, 26, 1014 (1994). 8. P. Rocco and M. Zucchetti, ITER Waste management: The Recycling and Clearance Option, Fusion Technology, 30, 1550 (1996). 9. F. Najmabadi and the ARIES Team, Assessment of Options for Attractive Commercial and Demonstration Tokamak Fusion Power Plants, Fusion Technology, 30, 1286 (1996). 10. Below Regulatory Concern: Policy Statement, U.S. Federal Register, vol. 55, no. 128, July 3, M.D. Lowenthal, Radioactive Waste from Nuclear Fusion: An Assessment of ITER Waste management and Decommissioning Hazards, Ph.D. dissertation, University of California, Berkeley (1996). 12. Code of Federal Regulations, Title 10: Energy, Part 61 Licensing Requirements for Land Disposal of Radioactive Waste (Nuclear Regulatory Commission), the Office of the Federal Register National Archives and records Administration, Revised as of January 1, ICRP Recommendations, ICRP Publication 60, Annals of the ICRP, Vol.21, No.1-3, S. Fetter, et al., Long-term Radioactive Waste from Fusion Reactors: Part II, Fusion Engineering and Design, 13, 239 (1990). 15. J.Raeder et al. (ed), Report of the SEAFP Project, European Commission, DG XII, EURFUBRU XII-217(95), W.Gulden, J.Raeder, I.Cook, SEAFP and SEAL: Safety and Environmental Aspects, Proc. ISFNT-4, Tokyo, M.Lindberg, K.Brodén, Repository Analysis for Waste from SEAFP 2 Models - Interim Report, SEAFP-2 Task 4.3, Studsvik Report RW-97 n. 6618, December Radioactive Substances Act, United Kingdom, Clearance Levels for Radionuclides in Solid Materials: Application of Exemption Principles, Interim Report for Comment, IAEA TECDOC-855, Vienna, January P.Rocco, M.Zucchetti, Recycling and Clearance Possibilities - Part two, JRC-Ispra Report, T.N.No. I , ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 7

8 21. N.P.Taylor, I.Cook, Description of Plant Models, Blankets and Structural Materials, UKAEA Fusion- Culham Report, SEAFP2/5.1/UKAEA/1 (Rev.0), C.B.A. Forty, Activation Analyses of In-Vessel Components, UKAEA Fusion-Culham Report, SEAFP2/4.1/UKAEA/1 (Rev.0), C.B.A. Forty, Activation Analyses of Ex-Vessel Components, UKAEA Fusion-Culham Report, SEAFP2/4.1/UKAEA/2 (Rev.0), R.A. Forrest, J-Ch. Sublet, FISPACT-97: User Manual, UKAEA Fusion-Culham Report, UKAEA FUS 358, E.T. Cheng, Waste Management Aspect of Low Activation Materials, IAEA-TCM Fusion Power Plant Design, March 1998, Culham, U.K. ANS98-CHENG-ROCCO- ZUCCHTTI-SEKI-TABARA -FINAL 8