First generation systems studies on P&T as a new
waste management issue were initiated in the 1970's in different OECD/NEA
Member countries:
- In
1973, the Japan Atomic Energy Industry Forum published a report titled
"A closed system for radioactivity" [1]. This report
pointed out the importance of R&D for P&T of long-lived nuclides as
long-term efforts. JAERI started the development of the partitioning
process for high-level liquid waste and the design study of a transmutation
system in mid 1970s.
- In
the United States, many individual researchers and small groups were
conducting studies related to P&T since Steinberg's seminal work in
1964 [2]. Oak Ridge National Laboratory investigated
P&T during the 1970s from a theoretical and assessment perspective [3-4].
Claiborne [5] demonstrated in 1972 the neutron-physical
feasibility of transmuting "by-product actinides" in LWRs. Work at Argonne
on pyrochemical separations technology already began in 1952 when it
was recognized that low-decontamination pyrochemical methods were ideally
suited to the reprocessing of the metal alloy breeder reactor fuels
that were under consideration at that time. The EBR-II reactor began
operation with highly-enriched metallic uranium fuel in 1964, and a
pyrochemical reprocessing method was put into place shortly thereafter
for demonstration of closure of the breeder fuel cycle [6,
7]. Because the fuel was limited to rather low burnup
at that time due to fuel swelling, a pyrochemical process was developed
that permitted the processing of fuel with very short cooling times.
The EBR-II reprocessing operation continued until early 1969, when the
demonstration of fuel cycle closure was deemed complete. These developments
of pyrochemical reprocessing methods remain of high value in future
P&T-schemes [8, 9].
- Simultaneously,
the German Research Centre of Karlsruhe, the CEA in France and the European
Commission at the Joint Research Centre of Ispra [10-11]
started a comprehensive theoretical and experimental R&D programme.
In France, the Castaing Commission [12] conducted
a general investigation in 1981-82 on the different approaches possible
in the fuel cycle and included the P&T option as a mandatory route for
further R&D. The studies were conducted during about ten years and were
summarised in overview reports which showed the complexity of the issue
and the discrepancy between the waste management "risk" approach on
long-term disposal and the P&T-approach aiming at the reduction of the
radiotoxic inventory by recycling long-lived nuclides into fission reactors.
Three
major "final assessment" reports were published in the late 1970s and
early 1980s, which led to following conclusions:
- The
conclusions of the EC programmes on P&T in 1977 and 1983 [10-11]
were that the impossibility of total actinide recycling and the impact
of the process flowsheets complexity on waste streams were the main
limitation of the potential benefits from the proposed P&T scenarios
for long-term hazard reduction. Partitioning would become worthwhile
as a HLW management scheme if advanced fuel cycles such as recycling
of plutonium and MAs through FBRs and LWRs were implemented, provided
that the loss factors for fuel isotopes could be kept very low (<5e-4).
Transmutation of MAs was considered theoretically feasible from the
point of view of neutron physics and fuel cycle technology but it was
not obvious whether the potential long-term risk reduction for the waste
disposal site compensates the increase in short-term risks for the workers
and the environment.
- Taking
into account the potential long-term hazard associated with the disposal
of spent fuel, the Castaing report (France) in 1982 concluded that it
was worthwhile to investigate the benefits of advanced reprocessing
techniques with separation and conditioning of Pu and MAs for intermediate
storage and tentatively for destruction by neutron irradiation. This
long-term programme is to be conducted simultaneously with investigations
of the waste disposal technology in experimental underground facilities.
- The
ORNL studies in 1977 and 1980 [3-4]
concluded that there were no cost or safety incentives P&T of actinides
for waste management purposes since the long-term risk is mainly associated
with long-lived fission products Tc-99 and I-129 and not with the actinides.
The reduction of the radiotoxic inventory of waste is theoretically
possible but needs the development of advanced partitioning methods
and the use of other types of reactors than the available LWRs.
The
period of active investigation on P&T starting in early 1970s was terminated
around 1982-1983 as no international consensus was obtained on the benefits
of P&T as an alternative or complementary waste management option.
1980s
During
the 1980s, a growing awareness of the inherent difficulties in creating
and licensing large nuclear waste repositories, and growing delays in
the R&D projects, particularly in the development of underground pilot
repository facilities, led the international community to reconsider the
potential benefits of P&T as a complementary waste management option and
these resulted in second generation system studies. This renewed interest
was also based on technological developments in several fields making
the P&T option seemingly more feasible.
In
October 1988, the Japanese government by way of the Atomic Energy Commission
(AEC) launched the ambitious "OMEGA" R&D programme [13].
The R&D programmes were stimulated by the collaborative efforts of JAERI
and the former PNC (now JNC). In the public sector, CRIEPI has also been
carrying out R&D on this subject.
The
"OMEGA" programme is proceeded in two steps: the phase-I was intended
to cover a period up to about 1996, and the phase-II to about 2000. The
basic studies and tests were to be conducted in the phase-I, and engineering
tests of technologies or demonstration of concepts are planned in the
phase II. After 2000, pilot facilities would be built to demonstrate the
P&T technology. Following items are being studied:
- Physical
and chemical properties of MAs and FPs.
- Partitioning
of radioactive elements from high-level liquid waste by reprocessing
process and recovery of useful metals.
- Nuclear
and fuel property data of MAs.
- System
design studies.
- Reactor
fuel and accelerator target.
-
Development of high power accelerator for transmutation.
Start of NEA involvement
It
was during this second era of P&T activities that the NEA became involved
in studying this subject. In 1988, next to launching the "OMEGA" programme,
the Japanese government also invited the international community, through
the OECD/NEA, to participate in the assessment of a broad range of P&T
developments.
This
initiative was the starting point of a world-wide renewal of interest
and work in the P&T field. Large scale R&D programmes are still being
conducted in Japan (JAERI, JNC, CRIEPI) and in France (CEA) in co-operation
with several European countries under sponsorship of the European Commission.
Important experimental programmes were conducted in the United States
at the Argonne National Laboratory (ANL).
As
a result of this increasing interest, the need was felt to re-examine
the validity of the P&T option in the light of the more recent results.
In France, a National Evaluation Commission was appointed in 1993 in order
to supervise the R&D activities in the field of radioactive waste management.
Reports were issued [14-15-16]
in 1995, 1996 and 1997. In the field of P&T, the following recommendations
were made:
- Priority
should be given to separation of Am-Cm from rare earths followed by
Am/Cm separation.
-
Among the fission products priority should be given to Cs and Tc.
-
On the subject of transmutation a distinction should be made between
short-term projects based on transmutation in present PWRs and long-term
R&D on future reactor systems e.g. fast reactors and accelerator-driven
transmutation.
-
Two options (partitioning-transmutation and partitioning-conditioning)
should be studied at the same level of priority and a priority listing
of the critical radionuclides should be made for each option.
-
The separation processes DIAMEX and SESAME should be demonstrated as
soon as possible in the hot facility ATALANTE.
-
Accelerator driven transmutation is a new venture, which should be studied
on the national level within a co-ordinated CEA-CNRS-EDF R&D effort
(GEDEON).
In
Japan, the ongoing "OMEGA" project covered the activities on P&T where
comparable national evaluation and assessment reports have not been openly
published. However, the Japanese evaluations and assessments have been
included in the OECD/NEA activities and publications as part of the NEA
assessment studies.
A
series of American reports was published in the meantime. On the basis
of the ORNL retrospective assessment of P&T [17],
the Electric Power Research Institute (EPRI) started a detailed evaluation
programme [18] on the concept of transuranic burning
using liquid metal reactors (LMR) and included, in their overview, the
waste management consequences resulting from "alternative spent fuel separation
processes". A study of the impact of P&T on the disposal of high-level
waste was prepared by Lawrence Livermore National Laboratories [19]
and the main conclusions of these US reports were:
- The
toxicity of high-level waste during the first thousand years cannot
be reduced by transmutation since the cross-sections of the isotopes
Sr-90, Cs-137, H-3 and Kr-85 are too small.
-
The cost of alternative reprocessing in order to reduce the actinide
content to a level below 100 nCi/g (3 700 Bq/g) is very high and requires
the construction of advanced aqueous reprocessing facilities and/or
the development and construction of pyrochemical reprocessing units.
-
The use of LMRs for burning plutonium and actinides would require the
construction of an aqueous reprocessing capacity of ~2 000 tHM/year
and the deployment of 30 GWe LMR capacity creating a cost penalty of
$0.5 billions to $2 billions per year.
- The
decentralised structure of the US electricity production, the absence
of economic incentive for reprocessing and the changes in the regulatory
requirements (NRC and EPA) for disposal facilities would make the acceptance
of P&T as a waste management scenario very improbable under the then
present economic conditions.
1990s
The
most recent published and most comprehensive national assessment report
on P&T was issued in 1996 by the National Academy of Science of the US
under the chairmanship of N.C. Rasmussen [20]. The
report covers all aspects of the problem from an American point of view.
The principal recommendations listed in the report are: · None of the
P&T system concepts reviewed eliminates the need for geological disposal.
· The current policy of the "once-through-cycle" should be continued.
· Fuel retrievability should be extended to ~100 years. · R&D should be
conducted on selected topics of P&T.
Since
the beginning of the 1990s, an emerging interest has been oriented towards
renewed P&T technologies, e.g. accelerator-driven systems (ADS) and pyrochemical
partitioning, which induced new R&D activities in several OECD/NEA Member
countries. Especially ADS has been the attraction pole for many new researchers
in the field and new international collaborations are being set-up in
this domain. Those OECD/NEA Member countries conducted in addition studies
on the P&T potential and giving overviews of national and international
R&D activities in this field. This growing community of researchers in
different OECD/NEA Member countries (in Europe about 250 researchers)
published multiple reports on P&T during the past five years, where an
overview of all these is out of the scope of this note.
The
IAEA assessment report on P&T in 1995 [21] investigated
the technical feasibility and the radiological impact. Conclusions indicated
that partitioning is indeed feasible but considerable R&D would be required
to implement a realistic flowsheet operable at industrial scale. The reduction
in long-term risks achievable by P&T of actinides is less than expected
and long-lived FPs which are not amenable to any form of P&T, also contribute
to the very long-term risk. All in all, the implementation of P&T would
be an immense undertaking, involving a large proportion of a country's
nuclear power program, but providing at best a rather small reduction
in potential long-term radiological hazard. The IAEA undertook several
complementary activities with respect to OECD/NEA's work (see following
section):
- A
survey of research activities related to P&T in non-OECD countries was
undertaken upon recommendation by a Technical Committee Meeting and
the report was published in 1997 [22].
-
Participants of a Special Scientific Programme on 'Use of High energy
Accelerators for Transmutation of Actinides and Power Production' held
in Vienna in 1994, in conjunction with the 38th IAEA General Conference
recommended the IAEA to prepare a status report on ADS. The general
purpose of the status report was to provide an overview of ongoing development
activities, different concepts being developed and their status, as
well as typical development trends in this area and to evaluate the
potential of this system for power production, Pu burning and transmutation
of minor actinides and fission products. The document [23]
includes the individual contributions by the experts from six countries
and two international organisations.
-
Other activities involve Co-ordinated Research Projects (CRP) on the
potential of Th-based fuel cycles to constrain Pu and to reduce long-term
waste toxicities examining the different fuel cycle options in which
Pu can be recycled with Th to get rid of the Pu, or replace the Pu with
materials that are less unacceptable to the public.
-
A Technical Committee Meeting was organised on the feasibility and motivation
for hybrid concepts for nuclear energy generation and transmutation
where programmes and concepts on ADS development were presented [24].
The
European Commission was partly supporting research work on partitioning
and transmutation of radioactive waste under the Fourth Framework Programme
(1994-1998). This work included nine research projects.
- Five
strategy studies are evaluating the capabilities of various burners
and fuel cycles to limit the production and even destroy the stock of
actinides (plutonium and minor actinides).
- Two
experimental projects are aiming at developing techniques for the chemical
separation of actinides and two others are dealing with the investigation
of transmutation of americium and long-lived fission products.
Within
the Fifth Framework Programme (1998-2002), strategy studies on P&T are
foreseen to investigate its benefits and compare different methods such
as critical and sub-critical systems taking into account the whole fuel
cycle. New efficient and selective processes will be developed for the
separation of the critical long-lived radionuclides form high level and
medium level waste. Basic nuclear data essential for transmutation and
the development of ADS will be measured and computed. The radiation damage
induced by spallation reactions in materials will be investigated. It
is foreseen to develop and test fuels and targets for actinide and long-lived
fission product incineration. The preliminary study of an ADS is also
considered in the programme with supporting research work on sub-critical
mock-ups, safety, coolants, the confinement of the accelerator/reactor
window and high power accelerators. Finally, new specific matrices could
be also developed for the conditioning of long-lived radionuclides, which
cannot be transmuted.
The
European Commission (EC) published in 1997 a report on the perspectives
and the deemed costs of P&T [25]. Main conclusions
in this report were the potential reduction of waste radiotoxicity by
a factor of 40 to 100 compared with the open fuel cycle scenario and depending
on the moment considered in the cooling period. Recycling the FPs was
reported not to entail any gain on their radiotoxicity where neptunium
recycling results in a gain after roughly one million years of decay.
Nevertheless, in terms of residual radiotoxicity, recycling these elements
may be an advantage because of their mobility in a geological repository
environment. For the first level of P&T, based on technologies derived
from existing techniques, the cost supplement over recycling plutonium
alone was estimated at about one-third of the fuel cycle cost. Partitioning
and fuel fabrication accounting roughly equal fractions of this cost supplement.
At the second level, where P&T is implemented based on completely new
technologies and aiming at complete separation of the MAs and some FPs,
the partitioning involves an additional cost estimated at half the cost
of the conventional fuel cycle operations.
References
[1]
JAIF, "A Closed System of Radioactivity", Atoms in Japan, August 1973
Supplement, (1973).
[2]
M. Steinberg, G. Wotsak, and B. Manowitz, "Neutron Burning of Long-Lived
Fission Products for Waste Disposal", BNL-8558 (September 1964).
[3]
A.G. Croff, et al., "A Preliminary Assessment of Partitioning and Transmutation
as a Radioactive Waste Management Concept", ORNL/TM-5808 (September 1977).
[4]
A.G. Croff and J.O. Blomeke, "Actinide Partitioning-Transmutation Program
Final Report. I. Overall Assessment", ORNL-5566 (1980).
[5]
J.C. Claiborne, "Neutron Induced Transmutation of High-Level Radioactive
Waste", ORNL-TM-3964 (1972).
[6]
C.E. Stevenson, 'The EBR-II Fuel Cycle Story', American Nuclear Society
(1987).
[7]
L. Burris et al, 'The Melt Refining of Irriadiated Uranium: Application
to EBR-II Fast Reactor Fuel: I. Introduction', Nuclear Science and Engineering,
6, 493 (1959).
[8]
J.J. Laidler, J.E. Battles, W.E. Miller, J.P. Ackerman, E.L. Carls, 'Development
of Pyroprocessing Technology', Progress in Nuclear Energy 31, p.131 (1997).
[9]
J.J. Laidler, 'Use of Pyroprocessing in the Preparation of Spent Fuel
for Transmutation', AIP Conference Proceedings 346 (Proceedings, International
Conference on Accelerator-Driven Transmutation Technologies and Applications,
Las Vegas), p. 627, (July 1994).
[10]
H.A.C. McKay, et al., "The Separation and Recycling of Actinides. A Review
of the State-of-the-Art", EUR-5801, European Commission (1977).
[11]
Commission of the European Communities, "Assessment Studies on Nuclear
Transmutation of By-product Actinide, Final Report", Joint Research Centre
at Ispra, SA/1-05-03-83-13 (1983).
[12]
Conseil Supérieur de la Sureté Nucléaire, Rapport de la Commission CASTAING,
Rapport du Groupe de Travail sur la Gestion de Combustibles Irradiés,
Paris, (December 1981-November 1982)
[13]
T. Inoue, et al., "Development of Partitioning and Transmutation Technology
for Long-Lived Nuclides", Nuclear Technology, 93 206 (1991).
[14]
Commission Nationale d'Évaluation Relative aux Recherches sur la Gestion
des Déchets Radioactifs, Rapport d'Évaluation n° 1, (Juin 1995), Edited
by B. Tissot president, Quai A. Citroën, 39-41, 75015-Paris.
[15]
Commission Nationale d'Évaluation Relative aux Recherches sur la Gestion
des Déchets Radioactifs, Rapport d'Évaluation n°2, (Juin 1996), Edited
by B. Tissot president, Quai A. Citroën, 39-41, 75015-Paris.
[16]
Commission Nationale d'Évaluation Relative aux Recherches sur la Gestion
des Déchets Radioactifs, Rapport d'Évaluation n° 3, (Septembre 1997),
Edited by B. Tissot president, Quai A. Citroën, 39-41, 75015-Paris.
[17]
C.W. Forsberg, A.G. Croffand, D.C. Kocher, "Historical Perspective - Economic
Analysis and Regulatory Analysis of the Impacts of Waste Partitioning
and Transmutation on the Disposal of Radioactive Wastes", ORNL-TM-11650
(1990).
[18]
EPRI 1991. a) R.E. Wilems and J.G. Dana, "The Effects of Transuranic Separation
on Waste Disposal", EPRI-NP-7263 (1991). b) C. Newman, "International
Programs Related to the Transmutation of Transuranics", EPRI-NP-7265 (1991).
c) J.E. Gingold, et al., "The Cost of Processing Irradiated Fuel from
Light-Water Reactors: An Independent Assessment", EPRI-NP-7264 (1991).
d) E. Rodwell, et al., "An Evaluation of the Concept of Transuranic Burning
Using Liquid Metal Reactors", EPRI-NP-7261 (1991). e) M.L. Thompson, et
al., "Projected Waste Packages Resulting from Alternative Spent Fuel Separation
Processes", EPRI-NP-7262 (1991).
[19]
Ramspott, et al., "Impacts of New Developments in Partitioning and Transmutation
on the Disposal of High-Level Nuclear Waste in a Mined Geologic Repository",
UCRL Report ID-109203 (March 1992).
[20]
"Nuclear Wastes. Technologies for Separations and Transmutation", National
Research Council: Committee on Separations and Transmutation Systems,
National Academy Press Washington D.C. (USA), ISBN-0-309-05226-2, (1996).
[21]
IAEA, "Safety and Environmental Aspects of Partitioning and Transmutation
of Actinides and Fission Products", IAEA-TECDOC-783 (1995).
[22]
IAEA, "Status Report on Actinide and Fission Product Transmutation Studies",
IAEA-TECDOC-948, Vienna, (1997).
[23]
IAEA, "Accelerator Driven Systems; Energy Generation and Transmutation
of Nuclear Waste", IAEA-TECDOC-985, Vienna, (1997).
[24]
IAEA, "Technical Committee Meeting on Feasibility and Motivation for Hybrid
Concepts for Nuclear Energy Generation and Transmutation", CIEMAT, Madrid,
Spain, 17-19 September (1997) (to be published).
[25]
EC, "Perspectives and Cost of Partitioning and Transmutation of Long-Lived
Radionuclides", EUR-17485 EN, (1997).
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