THE NEUTRON FACTORY IS CLOSING – FOR GOOD

SWEDEN An entire epoch of the Swedish nuclear power industry is being dismantled bit by bit. But the reactors in Studsvik, a purely research facility, will continue to be of great importance even when their parts are stored in well-sealed containers: the experience gained in its decommissioning process will be used when dismantling Vattenfall’s power-generating reactors at Ringhals in Sweden within a few years.

The country road that winds its way through the pretty forest landscape of Sörmland ends at the Studsvik power plant. After going through security, a visitor will not find it difficult to work out the reason for the street names: Atomic Street, Reactor Street, Uranium Street, Isotope Street, Gamma Street.

Roland Caftemo began working on Studsvik’s two research reactors back in 1978: R2 and the freely suspended R2-0 that hung down from a transverse gantry in the reactor pool. He is now a project engineer at AB Svafo, a company tasked with decommissioning nuclear plants and owned by the companies behind the nuclear power plants at Forsmark, Ringhals and Oskarshamn. Caftemo is responsible for coordination with the subcontractor Areva, who is carrying out the actual physical decommissioning of the Studsvik reactors.

Retro control room
When Caftemo shows us round the reactor hall, the nuclear fuel is long gone. The frame of the R2-0 reactor lies sawn into pieces on the floor, and high up on the pool edge, four staff are working with something that resembles gigantic fishing rods down in the water. The rods are up to nine metres long and equipped with tools at their ends, such as pliers, hooks, spanners, wrenches or Allen keys necessary to carry out tasks at the pool bottom. Most of the fishing rod tools were tailor-made at the plant.

Entering the reactor’s unmanned control room is like taking a trip back in time to the 1960s. “The colour is a genuine Asea green and many of the instruments are originals,” says Caftemo and points to the control unit for the six rods that were used to control the nuclear reaction process.

Neutron production
In a nuclear reactor, energy is produced by the splitting of atomic nuclei in a process called fission. In this process, uranium nuclei are split by allowing neutrons to collide with the atoms. When an atomic nucleus is split, large amounts of heat energy are released as well as two or three new neutrons – which then split new atomic nuclei in a chain reaction.

In a power-generating nuclear power plant, the heat is used to generate electricity with the aid of steam turbines. But the purpose of the R2 reactor was never to generate electricity, rather it was to produce as many neutrons as possible, among other things for the neutron scattering measurements carried out by researchers from Uppsala University’s neutron research laboratory.

The Studsvik reactors went into operation in 1960. They were used for civil research, and gradually also for commercial purposes, up to 16 June 2005 when they were shut down.

No more than about 100 employees ever worked on the reactors, which were run in operating cycles of three weeks. “One of the things that made it so interesting to work here was that the operating staff had so many different things to do,” Caftemo says. “One day you worked in the control room, the next day you carried out experiments or entered different systems to carry out tasks.”

Heavy work
AB Svafo began the actual decommissioning, or the physical segmentation of the Studsvik reactors in March 2015. The company had taken over the nuclear permits for the plant five years previously.

“The biggest source of concern during the first stage was to remove the two support legs for the reactor tank. They weighed 1,200 kilograms each and the job took several weeks. The actual waste handling also took a lot of time and work to complete. The most important thing was safety at all times,” says Caftemo.

AB Svafo developed a handling system specifically for Studsvik whereby the radioactive waste is placed in cassettes made of stainless steel. The cassettes are square boxes about 800 millimetres in width, height and length, and weigh approximately 230 kilograms each.

The steel containers are laid into moulds – rather like concrete boxes with lids – that are in turn placed into a 15-tonne radiation protection shell before being transported for intermediate storage in a rock shelter in the Studsvik region.

“Before the parts are placed in the cassettes, they are sawn into pieces, measured, weighed and marked. It’s very important to be able to trace which parts are stored in each cassette,” explains Caftemo.

AB Svafo estimates that it will ultimately store 23 cassettes containing reactor parts from Studsvik in Sweden’s final repository at Forsmark when it is ready. This may seem surprisingly few.

“Many of the parts were not at all as radioactive as we had thought when we started the decommissioning.”

A WORTHY BURIAL
Stage two of the process of decommissioning the Studsvik reactors will begin in 2016. The pool will then be dismantled.

The decommissioning is scheduled for final completion in 2019. An application for radiologically safe classification will then be submitted to the Swedish Radiation Safety Authority, and if that is approved the buildings can be demolished. This classification means that an object no longer needs to be monitored for radiation safety. A precondition is that the content of radioactive substances is so low that it may be regarded as harmless.

Caftemo will retire as soon as the decommissioning is completed:
“I want the burial of this plant to be worthy. It feels good to have stayed behind and been involved in the whole process.”

Studsvik research power plant is merely one of a series
The decommissioning of four of Vattenfall’s commercial reactors – two in Sweden and two in Germany – will begin in the next few years. But the first in line is Vattenfall’s Ågesta plant, Sweden’s first commercial nuclear power plant located just to the south of Stockholm. Ågesta produced district heat and electricity for the central Farsta district in southern Stockholm between 1964 and 1974. All the fuel and heavy water was removed after its closing, and what remains is low and medium radioactive demolition waste.

Actual demolition of Ågesta is expected to start in 2020 under the management of AB Svafo.

In the same year, Ringhals 1 will be taken out of operation. The electricity generation by Ringhals 2 will cease in 2019.

A key pilot project
Kjell Westerberg, the project manager at AB Svafo, responsible for the Swedish decommissioning programme within Vattenfall, explains that the Studsvik reactors will act as an important example for future projects.

“Studsvik involves all aspects of the demolition of commercial reactors, so we see it as a pilot project and an important part of our preparations.”

Vattenfall has set up the Business Unit Nuclear Decommissioning to handle the decommissioning and dismantling of the Group’s Swedish and German nuclear plants. The BU will plan projects, carry out cost estimates and demolish the plants.

“AB Svafo is the core of the Swedish part of the BU, whereas a local organisation in Germany will be tasked with planning the dismantling of Krümmel and Brunsbüttel,” says Westerberg.

Competence development is a term that Westerberg often returns to during the interview about future decommissioning projects:

“There is a lot of competence out in the plants, and we must ensure that it is used. At the same time we must see to it that it is continuously developed. Therefore, we will review the future competence needs together with Ringhals, and Ringhals personnel will also have the opportunity to come here to study and be involved in the work in Studsvik.”

Close cooperation
AB Svafo is now working closely with the STURE (Safe and Secure Phase-Out of Reactors 1 and 2) project at Ringhals during the planning stage and before decommissioning the reactors. “The aim is to obtain approval on the basis of the Environment and Nuclear Activities Act for the decommissioning when the shutdown operations are completed, which should be eighteen months after the reactors have been taken out of operation,” says Westerberg.

In the decades to come, the decommissioning of nuclear reactors will be a topical area of expertise in Sweden and Germany.

“This is an exciting and very multifaceted sector. Much of the competence is already available but we must ensure that it is developed, both by us and our subcontractors. There are major safety benefits as well as a lot of money to be saved by working efficiently. Of course, safety always has priority,” Westerberg underlines.

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