The global picture today

Research reactors play a significant role in the field of nuclear science and technology. Since early prototypes were designed and put into operation in the 1940s, the number of research reactors worldwide has increased rapidly as a result of developments in the nuclear industry in general and nuclear power programmes in particular. Research reactors have also contributed substantially in the area of non-power applications such as radioisotope production in nuclear medicine, agriculture and industry; neutron beam research; neutron activation analysis; material development and neutron radiography; and training. Several hundred research reactors have been built and operated worldwide [2].

The picture has changed considerably over the past 5–10 years with the reduced demand for many of the aforementioned programmes [6], maturity of the nuclear industry, increased competitiveness of the radioisotope market, increased competition for R&D funds, escalating operation and maintenance costs of ageing reactors, or changes in regulatory and/or government policy [7].

A number of examples are given in Section 5.2. The number of redundant reactors has gradually increased to the point that the number of shut down/

decommissioned reactors now far exceeds that of operational ones. This trend has been clearly visible for a number of years and there are no signs of its reversal. This inevitably calls for more attention to be given to

decontamination and dismantling of these older research reactors. Over 70 research reactors operating today are already 40 years old and will become likely candidates for decommissioning in the near term. Many of these reactors are located in Member States where appropriate decommissioning experience may not be readily available. It should also be noted that research reactors are situated in a large number of countries, making their decommissioning a real international issue.

About 830 research reactors have been constructed worldwide to date, with some 20 more under construction or planned. Of these, about 290 are in operation and about 520 are shut down and at various stages of decommis-sioning. Approximately 25% of research reactors currently in operation around the world are over 40 years old. There are also several dozen research reactors that have not yet completed the decommissioning process (Table 1).

The attached CD-ROM presents a detailed list of research reactors and gives the current status of each. The extent of decommissioning activities is expected to increase as more nuclear installations are taken out of service and fully dismantled.

The IAEA also monitors the progress of developments in decommissioning. For example, in 1998 it and consultants reviewed developments and produced a working document entitled Internal Report on Priorities for the IAEA Programme on Decontamination and Decommissioning of Nuclear Installations. In 2000 the IAEA conducted an internal performance, planning and assessment study (PPAS) on research reactors and low energy accelerators. The results of both working documents are reflected in this report.

One important consequence of the growth in decommissioning activities has been the experience gained from the decommissioning of larger nuclear facilities [8, 9]. Such projects include the total dismantling of large prototype facilities, which provided an opportunity to demonstrate that decommissioning could be performed in a safe and cost effective manner and also resulted in the further development and optimization of decommissioning techniques. In some cases, novel first use techniques have now become routine.

Following closure of a research reactor the overall decommissioning task is to remove the facility from regulatory control, which usually includes dismantling and the removal and disposal of all radioactive materials. As one example, Fig. 1 shows the Nestor reactor, Winfrith, UK, before and after total dismantling. Generally, the objective is to restore the facility or nuclear site to a condition suitable for unrestricted use. In cases where the plan for a site involves the remaining presence of radioactive materials above site clearance levels, the end state condition will be one of restricted use or in special cases in situ disposal (entombment). Recent examples of entombment or restricted use

FIG. 1. The NESTOR reactor, Winfrith, UK (a) before and (b) after decommissioning.

(a)

(b)

include, respectively, the RG-1M reactor in the Russian Federation [10] and the FR-2 reactor in Germany [11], which is currently being used as a museum (Fig. 2).

The IAEA previously defined three stages of decommissioning as the basis for assessing strategies. In recent years the IAEA has recommended a revised approach, based on the following definition of decommissioning: “the administrative and technical actions taken to allow the removal of some or all of the regulatory control from a facility” [12].

In this context, the IAEA now recommends three generic strategies or pathways, immediate dismantling, safe enclosure, and entombment, as further discussed in Section 6 [12]. Variations are possible, normally resulting from a combination of the above-mentioned strategies. The large decommissioning programme of the former USSR offers examples of typical decommissioning strategies for reactors as follows [10]:

offices/

labs

service building reactor building

ventilation plant fuel storage

building

Buildings being retained during SE

© Research Centre Karlsruhe

FIG. 2. The FR-2 reactor at the Research Centre Karlsruhe, buildings in safe enclosure (SE).

(a) The 2.5 MW(th) heavy water research reactor TVR. This was partially dismantled and portions of the site have been classified for ‘restricted use’

(Fig. 3).

(b) The 3 MW(th) heterogeneous WWR-2 reactor. This was dismantled 10 years after shutdown. The reactor building was demolished and the active liquid wastes, some of the solid waste and the irradiated reactor fuel were placed in suitable on-site storage facilities.

(c) Two training reactor facilities, VM-A and VM-4, situated at Paldiski (Estonia). These were placed in a condition of safe enclosure with three radiation protection barriers: a hermetically sealed primary coolant system; a hermetically sealed reactor compartment; and additional enclosures specifically constructed to withstand certain external events and impacts. These reactors do not require any maintenance, active control or power supplies. Periodic radiation measurements inside the shelter and routine air sampling are carried out through special penetrations in the walls of the enclosures

(d) The AM uranium–graphite water cooled reactor in Obninsk. This reactor was put into a substantial period of surveillance and maintenance in April 2002 [10, 13].

FIG. 3. The TVR reactor, Moscow: basement after dismantling of the cooling circuit.

Another feature of the worldwide scene has been the creation and expansion of a commercial market for decommissioning, which includes a multitude of contractors, specialist companies, consulting companies and other decommissioning oriented firms. This is in contrast to the mainly in-house strategic and technological approach prevailing in most countries in the 1980s and early 1990s. However, it should be noted that the current socioeconomic situation in many Member States does not yet allow full development of a competitive decommissioning market and the in-house approach remains a requirement or necessity due to such factors as loss of jobs and the costs of imported, proprietary technologies [14].

More recently, major advances have been made in decommissioning technologies, such as in electronics, computing and remote operations, which have contributed to significant improvements in decontamination and dismantling techniques. At the same time the regulatory environment has evolved, often requiring a more detailed assessment of proposals, stakeholder involvement and increased requirements for environmental impact considerations prior to the granting of approval for decommissioning activities.

Also, there tends to be more detailed scrutiny of many individual decontamination and dismantling tasks.

Consensus is that more needs to be done to address the problem of the growing number of research reactors coming to the end of their operational lives and the large number of extended shut down, but not decommissioned, reactors, in order to ensure safe decommissioning. In many cases [15] these shut down facilities were essentially put into a ‘do nothing’ strategy. Major concerns in these cases include the perceived lack of attention to decommissioning by operating organizations, regulatory bodies and decision makers, the lack of funding and infrastructures, inadequate management, potential understaffing and the inadequate exchange of information between national stakeholders or IAEA Member States. Recent developments have focused on the need to definitively plan for decommissioning activities to follow shutdown operations in a timely fashion. A recent example is the shutdown and planned decommissioning of AECL’s Whiteshell Laboratory, where emphasis was placed on completing a detailed environmental assessment and developing, planning and scheduling the decommissioning in parallel with facility shutdown operations [16]. In parallel with early planning for decommissioning, a growing percentage of research reactors today opt for immediate rather than deferred dismantling.