First ENEL and then SOGIN have carried out a number of activities in the framework of the general decommissioning programs. They are both in-field activities and planning and designing activities. The current situation at the four NPP’s is the following:

Garigliano

• Reactor defuelling and off-site shipment of spent fuel: 1985 — 1987

• Radiological characterisation of plant systems, components and structures: 1990

• Safe Enclosure of Reactor building: 1990 — 1998

• Safe Enclosure of Turbine building: 1994 — 1995

• Treatment of low-level waste and retrieval/conditioning of intermediate — level and high-level waste: 1988 — 1999

• Dismantling and safe enclosure of existing Radwaste system, demolition of Off-gas stack and Safe Enclosure condition to be reached within the year 2003

Latina

• Reactor defuelling and off-site shipment of spent fuel: 1988 — 1991

• Radiological characterisation of plant systems, components and structures: 1992

• Decontamination and dismantling of systems and components: 1992 — 1996

• Decontamination of the spent fuel pool: 1996 — 1999

• Treatment of radioactive waste, dismantling of primary circuit ducts and components and Safe Enclosure condition to be reached within the year 2006

Trino

• Radiological characterisation of plant systems, components and structures: 1992 — 1994

• Reactor defuelling: 1991

• Temporary dry storage of spent fuel at plant site within the year 2003

• Safe Enclosure condition to be reached in the year 2007

Caorso

• Radiological characterisation of plant systems, components and structures: 1992 — 1995

• Reactor defuelling: 1998

• Temporary dry storage of spent fuel at plant site within the year 2004

• Safe Enclosure condition to be reached in the year 2009

Most of the above mentioned decommissioning activities (in particular at Garigliano and Latina sites) were carried out using experience and skill gained by Company personnel during plant operation, in particular:

■ headquarters personnel were involved in the design and licensing activities,

■ plant personnel, who operated the plant, were involved in the activities for plant operation termination and decontamination/dismantling activities.

Engineering and R&D Departments of ENEL were also involved in the development and design of special equipments and tools, used for waste retrieval and decontamination of structures.

After plants shutdown the plant staff were significantly reduced; part of the personnel were transferred to fossil power plants, and retired personnel were not replaced.

8. Conclusions

Some broad conclusions can be drawn from the issues that have been briefly discussed.

The first point is that decommissioning is mainly a management challenge. It is a complex and multi-faceted problem, whose optimum solution requires a multidisciplinary approach. Nuclear experts, therefore, should be highly interested in being involved in it without living this experience as a kind of tedious and dirty job that somebody else has to do.

From a technical standpoint it is a substantially mature technology, which may have, however, important margins of improvement. Application of new advanced technologies may lead to reduced doses to workers and reduced amount of wastes to be disposed, with consequential important economic advantages. It is also clear that the sooner the decommissioning is prepared (even during plant operation) the better it is. We might also say that decommissioning is something that should be addressed as early as in the plant design process, as currently imposed by utility requirements as EUR (European Utility Requirements) for advanced NPP’s. And it should be understood that the proof that decommissioning can be completed in reasonable time and economically may be a prerequisite for building new NPP’s.

From the financial standpoint, decommissioning is also a challenge, because it is a cost intensive activity without any important direct investment return, if we exclude site reuse and returns in terms of image for the utility or the region. Therefore, a correct funding scheme is very important to provide for all necessary funds at the end of the plant operating life.

International consensus and harmonization are needed in several areas. This need has been recognized only recently, in the last years, when a greater number of NPP’s have terminated their service life.

A decision making process transparent both to the politicians and to the public, who deserve the information they want in an activity that is finally for their assurance, is undoubtedly useful.

Finally, let me introduce an example of design of a modular inherently safe reactor, called MARS, developed since 1983 at the University “La Sapienza” of Rome, in which the decommissioning aspects have been taken into account since the beginning.

This design has been aimed at strongly simplifying the plant layout, the components construction and assembling on the site in order to reduce construction times and costs.

This effort has produced, as a parallel significant result, a huge simplification of all decommissioning activities. In particular, the basic design choices of the MARS plant affecting decommissioning are shown in Table 3. These choices produce the results shown in Table 4.

A quick sequence of pictures (figs. 4 to 6) is self-explaining of the decommissioning phases for this reactor.

[1] hmh@theorie3.physik. uni-erlangen. de

[2] mwherman@bnl. gov

[3] RIPL-2 studies focused on incident energies below 20 MeV, a typical limit for standard nuclear data files. However, new applications such as ADS, medical radioisotope production and radiation treatment re­quire reliable data at much higher energies (up to 1.5 GeV in the case of ADS). Most of the parameters available from RIPL-2 cannot be ex­trapolated to such high energies (e. g., temperature dependence of the GDR width). In particular, there should be consistency between statis­tical model calculations at low energies and the intra-nuclear cascade model commonly used at high energies.

[4] Adopted from a combination of Audi et al (1997), Takahashi et al (1973) and US ENDF/B-VI (Dunford, 1992); uncertainties are given in parentheses (for example, 0.13(2) means 0.13 ± 0.02).

Expressed in terms of incremental units of 10 keV starting from zero (first incremental energy step of continuum gamma spectra is from zero to 500 keV, as noted in parentheses).

+ Neutron spectrum adjusted to 0-1794 keV.

* Neutron spectrum adjusted to 0-620 keV.

[5] Croatia owns 50% of the Krsko 676 MWe Westinghouse PWR plant located in Slovenia.

* E, P and DH stand for electricity, process heat and district heating.

[7] Bruce A reactors are currently laid up; it is expected to start up in 2003.

[8]

Unit 1 was taken out of operation in 1988, unit 2 in 1990.

[9] maurizio. cumo@uniroma1.it

[10] 60 years is a limitation existing in the USA. In other countries this condition may last longer up to 100 years and more

[11] If a plant is allowed to sit idle for 30 years, for example, only about 1/50th of its original radioactivity from cobalt-60 will remain; after 50 years, some 1/1,000th will remain.

[12] Important in fusion devices also

[13] Fission products are also often found in nuclear reactors as a result of defects in the fuel cladding

[14] The clearance ‘’is the removal of material from a system of regulatory control provided that the radiological impact of these sources after removal from the system is sufficiently low as not to warrant any further control’’