Lead shutter for the IFMIF LIPAc accelerator

Abstract

The International Fusion Materials Irradiation Facility (IFMIF) aims to provide an accelerator-based, D-Li neutron source to produce high energy neutrons at sufficient intensity and irradiation volume for DEMO (Demonstration Fusion Power Plant) materials qualification. As part of the Broader Approach agreement between Japan and EURATOM, the goal of the IFMIF/EVEDA project is to work on the engineering design of IFMIF and to validate the main technological challenges which, among a wide diversity of hardware includes the LIPAc (Linear IFMIF Prototype Accelerator), a 125 mA continuous wave deuteron accelerator up to 9 MeV mainly designed and manufactured in Europe.

The LIPAc beam is stopped in a copper cone involving a high production of neutron and gamma radiation and activation of its surface. A lead shutter has been designed to shield against the gamma radiation coming from the copper cone through the beam tube when the beam is off, in order to allow access inside the accelerator vault. The lead shutter is located in a multipurpose chamber that also contains a scraper and two vacuum ports. The function of the scraper is to protect the last part of the beam tube in case of abnormal beams.

The requirements imposed on the lead shutter chamber include the motion of the lead shutter to locate it in open (beam on) and closed position (beam off), resistance to the radiation environment, vacuum and leak tightness, alignment capabilities of the scraper and leak tightness of its cooling circuit. In this article the radioprotection calculations demonstrating the shutter performance are presented and the mechanical system of the lead shutter and the layout of the different elements contained in the chamber are described, along with their functions