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Radiation Protection aspects for SHIP

Radiation Protection aspects for SHIP

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Radiation Protection aspects for SHIP

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  1. Radiation Protection aspects for SHIP Doris Forkel-Wirth, Stefan Roesler, Helmut Vincke, Heinz Vincke CERN Radiation Protection Group 1st SHIP workshop, 10-12 June 2014 Universität Zürich

  2. Content • General info • Radiation issues at the SPS extraction area and in TDC2 • Required shielding around SHIP target • Residual dose rate of the SHIP target • Dose rate in detector hall (only passive shielding) • Activation of muon shielding

  3. General info • Similar number of protons on target than CNGS (but SHIP facility is close to surface) • 4×1019 pot/year • in total (in 5 years) ~2×1020 pot • RP design is done for 7×1013 protons (400 GeV) per pulse (every 8.4 s) i.e. 530kW ! • Main Radiation Protection issues of SHIP, • Beam losses in the SPS accelerator and extraction area towards SHIP • High prompt dose around SHIP target  sufficient shielding is needed • High residual dose rate after beam stop  only remote handling possible in target area • Air activation  reduce air volume to a minimum, use He (or vacuum) in target area • Target station is located close to surface  environmental impact due to possible activation of soil and ground water.

  4. RP aspects for the SPS machine • Beam losses will cause: • Air activation • Residual dose rate increase • Dose to equipment (magnets, cables, etc..) • “Estimated beam losses from high intensity beam (7×1013protons per extraction) are about a factor 7 higher than for CNGS beams“ .(Quotation from collimator LIU review minutes) • Already at nominal beam intensity the dose levels will be a factor 3-6 higher than in previous years. Without mitigation, this could lead to dose levels of 12 mSv/hr after a month of cool-down. • Ways to reduce beam losses have to be investgated.

  5. Beam extraction area TT20 Courtesy: B. Goddard Dose rate on contact of the element(unit : µSv/h) H*(10) at first splitter region … about 10 monthsafter beam stop. Dose rate at 40cm of the element (unit : µSv/h) ……. high dose rate levels at work places will be present to personnel during installation/modification of beam line elements.

  6. Beam extraction area TT20 A careful planning of these activities combined with an optimized work and dose planning will be essential. Work needs approval from CERNs ALARA committee. The concrete wall of TDC2 tunnel and the soil close to TDC2 tunnel are activated. The CE workers need to be classified as Radiation Worker, have to receive all required safety trainings and need to be individually monitored. In order to quantify the amount of activation as well as the lateral distribution (volume) of activated soil it is advised to take soil samples close to the TDC2 area. Removalof existing beam line components has to be foreseen before civil engineering work in TDC2 canstart. A waiting time has to berespectedbeforebeam line equipmentcanberemoved. SHIP provides an opportunity to improve the present situation at high beamlosspoints.

  7. Benefitsof radiation decayin TDC2 PMI 25 In red marked zone: ~1mSv/h (at 40cm distance) after 10 months of cool down time.

  8. Shielding around SHIP target Front view Side view • FLUKA MC code has been used to estimate the shielding requirments • No gaps or feedthroughs (for services like cooling) in the shielding; will decrease the efficiency of the target shielding. Units in m Muonshield Anabsorber downstream of the last primary beam tunnel element might be needed to shield the beam line elements and to reduce their activation.

  9. Residual dose rate around the SHIP target Remote handling only! Residual dose rate (in uSv/h) around the SHIP target after one operational year at ultimate intensity and 1 month of cooling time. Target exchange will be a very delicate and demanding intervention …… and further studies and optimisation of such an intervention are necessary. Residual dose rate (in uSv/h) at the SHIP target after one operational year and different cooling times as a function of radial distance from the target center

  10. Radiation level in detector hall Detector hall will be classified as a Radiation Area (during beam operation) moraine concrete tungsten lead detector hall SHIP target ~ 1 uSv/h ~ 4 - 5 uSv/h ~ 10 uSv/h

  11. Activation of tungsten muon shield Isotope production in tungsten shield Muon shield will become slightly activated especially the upstream part Ambient dose equivalent in the tungsten shielding as a function of cooling time (after 180 days of operation, averaged (0<r<20cm)

  12. Summary & conclusion • The performance of the ZS septa magnet and the induced radioactivity in the SPS extraction region requires further studies. Ways to reduce beam losses have to be investgated. • Work in TDC2 requires a detailed work and dose planning. It will be an ALARA level 3 intervention which requires prior approval from the ALARA committee. • Concrete in TDC2 and soil close to TDC2/TCC2 tunnel are activated. Soil samples close to extraction area would be needed to quantify the activation level of the soil. • Target shielding design – massive iron/concrete shielding needed. • Detector hall will be classified as a Radiation Area • Muon shielding will become slightly activated. • Some other RP studies (like production of radioactive waste, waste disposal, dismantling of the facility, etc. ) and environmental issues (releases of radioactivity via air or water pathways, activation of soil, etc.) are not studied yet. This will however be needed at a later stage of the project.

  13. Spare slides

  14. CERN’s Area Classification