Advanced and/or special treatment technologies

Even though it may be too early to speculate about the perspectives of innovative nuclear systems anticipated for the future, the Group participating in the technical meeting did agree that such contingencies of spent fuel management should be covered as a future possibility in

view of the growing interest attracted to the global energy and environmental issues. It was noted that IAEA should keep abreast of the new development in innovative nuclear systems, to determine if the recommended spent fuel tracking procedures are adequate.

2.2.5.1. Refabrication

Even though there has not yet been any industrial refabrication of spent fuel from a power reactor for reuse in another reactor, research activities have been conducted on lab scale, a representative case being the DUPIC project intended for reuse of spent fuel from PWR in CANDU reactors without separation of sensitive materials like plutonium. The basic rationale of the DUPIC fuel cycle is that the typical remnant fissile contents of spent PWR fuel (approximately double those of natural uranium) can be reused with doubling burnup in a CANDU reactor, which is designed to be fuelled with natural uranium. Another example is the AIROX concept which had been tested on laboratory scale in the mid-sixties at Atomics International in the USA, with a view to reuse spent LWR fuel in LWRs by adding enriched uranium to the depleted spent fuel. From a technological point of view, the DUPIC (or the AIROX, for that matter) fuel cycle concept bears some interesting features that are anticipated from innovative fuel cycle options. All the fuel fabrication processes are remotely conducted in shielded hot cell facility [15].

The concept of the DUPIC fuel cycle is illustrated in Figure 4. The identity of spent PWR fuel is destroyed by the DUPIC process and a new “fresh” fuel is regenerated for reuse in CANDU reactors (of CANFLEX type).

FIG. 4. Schematic diagram of DUPIC fuel fabrication process.

The DUPIC fuel cycle is an extreme case representing the complexity of spent fuel data requirement due to the complexity of fuel contents to be processed. With a view to resolve the disparity in spent PWR fuel burnup to come up with a homogeneous compositions in CANDU fuel to be refabricated, a study on algorithm for optimal combination of different burnups was conducted [16].

2.2.5.2. PBMR (pebble-bed modular reactor)

The technology for pebble-bed modular reactor (PBMR) is attracting industrial attention as one of the major reactor models for innovative nuclear systems to be deployed in the future.

Because of the technical features of PBMR fuel in a bulk of hard spheres in pebble form, the management of spent PBMR fuel and its data management call for special considerations [17].

In the particular case of PBMR, tracking information of its fuel in pebble form is considered to be a challenge. The pebble form fuel is neither amenable to handle nor identifiable as a unique item in accounting for safeguards and this issue is being looked at by IAEA.

2.2.5.3. Partitioning and transmutation

As the first step in the transmutation process is partitioning, a process similar to reprocessing, the spent fuel data requirements for both activities should be similar. However, the tracking requirements for a transmutation reactor are much greater than for a power reactor. In a power reactor, the main concern is what happens to the uranium, plutonium, and thorium isotopes in the fresh fuel. In a transmutation reactor, one has to track the disposition of all the radioactive isotopes that are transmuted.

With the development of particle accelerator technologies in 1980s and 1990s there is an increasing interest in determining if these technologies can fulfill some basic nuclear missions. One of them is the transmutation of long lived nuclides in spent fuel and high level waste streams to short or medium lived radionuclides or stable isotopes (projects like, MICANET – EU, ATW-USA, Omega-Japan, …) [18]. The reduction of radiotoxicity by transmutation of minor actinides can be shown as Figure 5.

The objectives of transmutation and partitioning technologies may be very different, but it is possible to distinguish several approaches discussed in different countries [19].

From the point of view of spent fuel data management systems, the future transmutation and partitioning technologies are treated similarly to the spent fuel conditioning or reprocessing technologies — the operator of the transmutation and partitioning facility must define the type of data needed to perform a safe and efficient spent fuel transmutation.

Additional data may be required for the disposal of generated radioactive waste; for which data would be generated by the operator of the transmutation and partitioning facility.

Additional data might further be needed, depending on the number of independent installations involved in the transmutation and partitioning. However to be consistent with the statements in previous sections of this publication, the spent fuel data management is followed only up to the steps of transmutation and partitioning process, since this technology usually requires mechanical and chemical destruction of spent fuel assemblies (see Figure 6 for a case of electrorefining process for actinide partitioning⁸).

8 For recent trends on this subject, see Global Nuclear Energy Partnership website(www.gnep.energy.gov).

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Pu and Am recycling in PWR – Cm disposed Pu recycling in FNR

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Pu and Am recycling in PWR – Cm disposed Pu recycling in FNR

Pu and MA recycling in FNR

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Pu and Am recycling in PWR – Cm disposed Pu recycling in FNR

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Pu and Am recycling in PWR – Cm disposed Pu recycling in FNR

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FIG. 5. Reduction of radiotoxicity by transmutation of minor actinides.

FIG. 6. Illustrative flow diagram of actinide partitioning systemby electrorefining process.