Late 2015, the ITER Organization created the Beryllium Management Committee to prepare the rules and best-practice guidelines for the safe handling of beryllium, which has been chosen as armour material for the plasma-facing components of the vacuum vessel. Rene Raffray, the ITER Blanket Section Leader and new committee Chairman speaks to Newsline about the scope of the group's work and about beryllium itself.
An example of a first wall semi-prototype, clad with 10-mm-thick beryllium tiles. This prototype was manufactured by Areva, one of European Domestic Agency suppliers. Other semi-prototypes have been manufactured and tested in Russia and China.
As Chairman of the recently established ITER Beryllium Management Committee, can you tell us more about its scope and responsibilities?
The key objective of the committee is to ensure the sound establishment of a beryllium safety program at the ITER Organization in order to deliver the safe working environment demanded by all stakeholders. Representatives from a wide array of ITER units are participating (Legal Affairs, Health & Safety, Operation Management, Assembly, Human Resources, Radiological Monitoring, Buildings), as well as technical responsible officers and the Domestic Agencies that are involved in the procurement of beryllium components.
As part of the initial effort, the committee is establishing a full suite of documents to describe how beryllium will be handled safely at ITER, including a communication statement for the general public, a policy for the management of beryllium, legal requirements, a beryllium management program (or code of practice), and a medical monitoring and surveillance program.
The work requires interacting with colleagues from the areas of Buildings and Safety to better understand the space requirements required for the storage or the inspection testing of beryllium-bearing components, the building schedule and the associated regulations to help the project make informed decisions on how best to proceed. A mechanism is also under development to identify all the staff positions that will be involved in the management of beryllium components and the specific needs for training or medical surveillance.
These actions will take some time to be completed. In the meantime, we are developing an interim set of guidelines for staff members presently visiting facilities where beryllium components are manufactured or handled.
Which components of the ITER machine will contain beryllium and what are the particularities of this chemical element?
The blanket is the component that will make the most use of beryllium due to the compatibility of this element with the plasma as well as its good thermal and mechanical properties. The 440 first wall panels will be covered with 8-10 mm of beryllium armour, for a total of approximately 12 tonnes of beryllium distributed over a surface area of about 700 m2.
Other ITER components will also employ beryllium, albeit on a much lower scale. For example, the Faraday screens of the ion cyclotron heating and current drive system use about 40 kg of beryllium; diagnostics will need a small amount of beryllium for windows and first-wall samples; and the Test Blanket Modules use about 100-200 kg of beryllium inside the modules to act as a neutron multiplier in order to enhance the tritium breeding in the test module. Beryllium oxide is also used as insulation in some components.
Rene Raffray, the ITER Blanket Section Leader chairs the committee that was recently established to prepare the rules and best-practice guidelines for the safe handling of beryllium.
We are not going to use or implement any components containing beryllium soon. So why is it important to plan for beryllium handling now?
It's true that components containing beryllium won't be on site for a number of years. However, the procurement of these components is already underway, including the fabrication and testing of full-scale prototypes at the Domestic Agencies, so we are faced with the possibility of ITER staff members visiting facilities where beryllium components are manufactured or handled. Clear procedures are being established to make sure that this is done safely.
Tell us more about beryllium itself. Why does it need to be treated with care?
Beryllium is used in industry in three main forms: beryllium metal, beryllium alloys and beryllium oxide. Applications range from the aerospace and nuclear industries to use in electrical control gear and switchboards.
Beryllium is classified as a potential carcinogenic. Although in block form the material does not present much risk, the inhalation of beryllium dust can cause severe respiratory problems. Dust can result when microscopic residue surface particles on the beryllium are released into the air due to transport, handling and/or assembly activities.
From a licensing point of view, the French regulator has requested that special attention be paid to this toxic material and it is clear that the beryllium issue must be considered by the ITER Organization as one of the highest risks for the workers, the public and the environment. There is an airborne concentration limit above which specific control measures are necessary; thus, all industries manufacturing or employing beryllium components must set up procedures in order to satisfy safety requirements. The closest comparable situation to ITER is the JET tokamak, which has beryllium-armoured walls and a beryllium code of practice that has been developed and improved over many years. We have been interacting closely with the health experts there and have a number of dedicated contracts to benefit as much as possible from their experience and expertise.
Beryllium is used in applications ranging from the aerospace and nuclear industries to electrical control gear and switchboards. The closest comparable situation to ITER is the JET tokamak, which has beryllium-armoured walls and a beryllium code of practice that has been developed and improved over many years.
Where will we source the beryllium for ITER components?
The ITER Organization is procuring its beryllium components from the Domestic Agencies—for example, the blanket first wall will be procured by Europe, Russia and China. It is up to these Domestic Agencies to select material suppliers according to ITER Organization specifications. At this stage, beryllium materials from the China, Russia and the US have been qualified according to the ITER specifications.
What has JET's experience taught us about the behaviour of beryllium in tokamaks?
Beryllium's low atomic number makes it compatible with plasma operation because it reduces the radiative effect in case of plasma contamination by armour erosion which—for material with a higher atomic number—could otherwise rapidly cool down and quench the plasma. It also presents relatively good thermal and mechanical properties.
Because of these characteristics, it has been used for the protection of internal components in various magnetic fusion devices (most importantly in JET). For a device as large as ITER, however, a number of issues still have to be considered: heat load limits arising from temperature and stress constraints under steady state conditions, armour lifetime (including the effects of sputtering erosion as well as vaporization and loss of melt during disruption events), tritium inventory and permeation, and a potential beryllium/steam reaction.
Fabrication is also an important factor in the overall assessment of beryllium as armour for plasma-facing components. For ITER applications key issues have been addressed through analytical studies as well as an R&D program on the manufacturing and testing of small-scale mockups under ITER-relevant conditions.
What safety measures will be put in place for the handling of beryllium?
Appropriate measures, systems and actions will be implemented to protect workers and prevent any exposure to operators and to the public. The primary measures focus on minimizing work with beryllium wherever possible and on the continuous monitoring of the airborne concentration in beryllium areas.
Other protective measures include extensive use of risk assessment, health monitoring, controls (such as warning signs, protective clothing, and respiratory protection), education and training. The effectiveness of the system we put into place will be regularly measured by the Health and Safety Division against key performance indicators. Independent audits by experts in beryllium will ensure compliance and the continuous improvement of the system.
