Status Report by the n_TOF Technical Coordinator P. Cennini AB-ATB on behalf of the n_TOF Team The n_TOF Facility Where are we standing Resume of the previous EPR Old Target removal and Investigation Pitting corrosion mechanism study Solution studied for the New Target Design Feasibility Conclusions Second n_TOF External Panel Review, CERN, 14 February 2008 The n_TOF Facility Neutron production by spallation on Pb using a 20 GeV/c proton beam Energy eV to 250 MeV Neutron Flux: 6.2105 n/cm2/7x10 12 p Flight path: m Duty Cycle: < 1 % Energy Resolution: 0.02 % at 1 keV 0.2 % at 1MeV Intrinsic in-beam Contamination: Gammas 10%, 1 % at 100 MeV Outside-beam Contamination: 700 m 3 /h) Complex structure needed to distribute the air flux Tantalum purchasing (cost & time) Completely new design (no acquired experience) Moderation (solid?, liquid?) New Target Design: Residual dose rates [mSv/h] for the Ta cylinder air cooled. proton beam Lead Volume = 100 l, Density = ~1130 kg Moderator (5 cm) Water IN Water OUT Water distribution structure Existing Pool (Containment Vessel) L=35 cm Quick locks Tap New Target Design: Cylindrical Lead Target, water cooled New Pressurized Vessel Air IN Pb (casted) Water Tank (Storage) Shielding =60 cm New Target Design: Pb Target =60 cm Residual Dose rate Strategy to restart the Facility in 2008 Considering that: The acquired experience with the old target is showing the ability of lead to work without serious mechanical damages over a large number of cycles (~5.2x10 19 p). The mechanism of the pitting corrosion has been studied and understood. By building a new Cooling Circuit the safety requirements suggested by the External Panel could be implemented in agreement with the CERN Safety Rules. The use of lead presents clear advantages in terms of reduced residual dose and self shielding. The delivery in 2008 is mandatory The installation via the shaft of a new lead target cooled by pressurized water in the volume defined by the existing Pool is the solution under study Summary of the Envisaged improvements Design criteria for the Facility up-grade: The use of a pressurized water cooling circuit The double containment in the whole cooling circuit The infrastructure to collect the contaminated water The water flow control on the proton impact area The continuous monitoring and control of the water chemistry The proton beam optimization (enlargement of the beam impact crossection) The use of a Pb alloy to boost the mechanical characteristics Reduction of the target total mass (lead and supports) Items discussed in the following presentations Feasibility: Installation via the shaft Feasibility Detailed Pit Survey Measurments Feasibility: View of the existing Pool Second containment for the new Target Assembly Third containment for the new Target Assembly Feasibility: Pit lay-out The Cooling Station is equipped with a closed Retention Vessel. The piping between the Cooling Station and the New target Vessel is double-wall. Any water leak in the Pit is collected in the old Pool via the Envelope (funnel). The water collected in the Pool goes by gravity in an external accessible closed vessel. In terms of dose rate and accessibility, the access to the connecting area in the pit during the installation and the decommissioning phase is possible. Quick connections Pump Heat Exchanger Main Water Tank (in the Cooling Station) Water Tank (in the Service Gallery) Normal Working Condition Replacement 90% of the water (without Target removal) Emptying of the Target Container (Decommissioning) Cooling Station Scheme for Cooling water replacement and Decommissioning Shielding Tap (remotely operated) Air Lifting Air Compressor Feasibility: Time-Scale For the Cooling and Ventilation the project phase consists on the choice of standard elements based on the specifications defined by the Target Assembly study. This phase is short compared to the installation of the various elements requiring hardware interventions and civil engineering works on the field. A delay of 6 months for the project and installation seems possible. For the Target Assembly the situation is opposite, in fact the design phase is requiring many simulations for the neutronics, thermal behavior, material fatigue, mechanics... Due to short installation time needed, 3 months design plus 4 months construction seems possible. Main items considered to evaluate the time-scale: 1.The Target Cooling & Target Area Ventilation 2.The Target Assembly Assuming a start in a well defined direction end of February 2008, the possibility to have a target ready 1st October 2008 is certainly challenging but (hopefully) realistic. An important combined effort has been done during the last months to evaluate the status of the old Pb target. Its status is well understood and a consensus on the mechanism responsible for the target present situation has been reached between CERN and the Collaboration. CERN and the Collaboration are preparing an action plan to have a new target ready for running in A complete and detailed engineering study is in progress. The FLUKA simulations for the new geometry is in progress. The Safety File preparation is in progress. A HAZOP will be organized to show that the Facility can cope with a range of accident conditions. Conclusions