European Spallation Source ERIC Target Helium Cooling

Transcription

1 European Spallation Source ERIC Target Helium Cooling Ulf Odén (Per Nilsson) Target System Work Package Manager 18 October, 2017

2 European Spallation Source ERIC Target Helium Cooling Application European Spallation Source ERIC Target System Limits of Use Constraints: Spallation Material Tungsten max 500 C Cooling Media Helium C 11 bar Main Radiation Effects (unmitigated/mitigated) Pipe rupture - workers 250 / 2.8 msv - public 0.05 / 0.05 msv After 5 h helium flow in ETHEL After 10 h After 25 h LOCA - workers 579Sv / 0 msv - public TBD / 0.05 msv Research Details No tungsten oxide erosion in lab with Target System operation conditions Major Issues and Challenges First of its kind tungsten spallation source/helium cooling facility Coolant Processing and Handling Helium 11 bar 3 kg/s Achievement No tungsten oxide erosion within the Target System conditions R&D Needs Design of helium filter equipment 2 Oral or Poster: Ulf odén, European Spallation Source ERIC Target Helium Cooling.

3 Outline ESS overview Hazard Analysis Accident Analysis Report: Loss of confinement in Target He system Loss of target wheel cooling during beam on target ETHEL Test set up Results Conclusions Inventory Calculations Particles Planned activities TOAST (Tungsten Oxidization AeroSol Transport) 3

4 Neutron Production Target Instruments Superconducting Proton Accelerator 4

5 February

6 Target, Monolith walls 6

7 Journey to deliver the world s leading facility for research using neutrons 2025 ESS Construction Phase Complete 2009 Decision to Site ESS in Lund 2014 Construction Starts on Green Field Site ESS Starts User Program ESS Design Update Phase Complete Machine Ready for 1 st Beam on Target European Design of ESS Completed

8 Key features of the ESS Target Station Moderator and reflector monolith vessel Target Safety System Monitors target coolant flow, pressure and temperature, monolith pressure, & target wheel rotation Prohibit beam on target if parameters are outside specified limits Helium cooling of target material Mass flow 3 kg/s Pressure 11 bar Temperature inlet/outlet 40 C/240 C target wheel Rotating solid tungsten target 36 sectors Mass, total 11 tonnes, whereof 3 tonnes of W Rotates 23.3 rpm, synchronized with pulsed proton beam 14 Hz Maximum Tungsten temperature 500 C Moderators 1 st MR plug offering: Cold, 30 mm high, liquid H 2 moderators, 17 K Thermal, 30 mm high, H 2 O moderator, 300 K 8

9 WP2 Target Systems First of helium cooled tungsten target Target System Tungsten Bricks in Cassette 36 sectors 3 tonnes of tungsten Rotates 23.3 rpm, synchronized with pulsed proton beam 14 Hz Maximum Tungsten temperature 500 C 9

10 WP2 Target Systems Mass flow 3 kg/s Pressure 11 bar Temperature inlet/outlet 40 C/240 C 10

11 Hazard Analysis Loss of confinement (pipe rupture) Release: 6 seconds 30 kg He / 0.1 g particles Mitigation: Classified pipe system (H3) Evacuation alarm (2 min) Loss of Target Wheel Cooling Release : 10 seconds 30 kg He / 0.1 g particles 9hr 11 kg molten tungsten /130 kg moderator water 150 g Beryllium Mitigation: Target Safety System He high temp/low flow&pressure Controlled release to stack Unmitigated dose Workers Public Mitigated dose Workers Public Unmitigated dose Workers Public Mitigated dose Workers Public 250 msv 0.05 msv 2.8 msv 0.05 msv 579 Sv TBD* msv 0 msv 0.05 msv *experiments and calculations not finalized but the need of mitigation expected 11

12 Hazard Analysis Data Total amount of particles after 1 year is 10g 10g tungsten oxides = 1500 GBq Pipe rupture will release 1% of total filter particle inventory (DOE HANDBOOK AIRBORNE RELEASE FRACTIONS/RATES AND RESPIRABLE FRACTIONS FOR NONREACTOR NUCLEAR FACILITIES) Top 10 radioactive isotopes: Sb117, Sb118, Sb119, Yb169, Ta182, W181, W185, W187, Re186, Re % of helium gas => 1000 GBq 12

13 Conservatism is 10 g of particles a conservative estimation? Confirmed by: Erosion test (ETHEL) Tungsten oxide calculations 13

14 ETHEL Loop and Components EDD Responsible: Per Nilsson Quartz Microfibre Stainless, welded + few Swagelok 6 kw ~2l, versatile 10 bar, 450C (316L) 7 mm Quartz Grafex EXP seals VTUG 60 3 g/s at 6 bar to 10 bar Air cooled Speed control Water cooling 14

15 ETHEL vessel Shear stress on the sample surface is <100Pa. The helium nozzle projection can be seen as thin lines. 15

16 ETHEL (ESS ) EDD Responsible: Per Nilsson Two samples pre oxidised at 500 C in He % O 2 for 1 h Helium jet of > 100 m/s at 9 bar and > 200 C was blown perpendicularly onto tungsten samples at above 300 C After 5 h helium flow in ETHEL After 10 h After 25 h 16 SEM pictures

17 Maximum oxide formation (ESS ) EDD Responsible: Yong Joong Lee Calculated maximum tungsten oxide production with an oxygen impurity level of 5 ppm Refilling rate 1 g/h (compensating the system leakage) Assuming that all oxygen in the He system is used for oxidation of the tungsten surface => <10g/y of tungsten oxides 17

18 TOAST Tungsten Oxidation AreoSol Transport Moderator and reflector monolith vessel target wheel 18

19 TOAST Tungsten Oxidation AreoSol Transport ESS needs to improve the basis for the tungsten aerosol release fractions. Only a few release fractions found in literature are based on tungsten data. 19

20 TOAST Tungsten Oxidation AreoSol Transport Draft setup Trap/ Constriction 2*1 m 1.5 Measurement Filter Flanges Outside Aerosol Measurements Pipe 1m 1.5 Water cooler Window Sample Box Filter Pressurized air 20

21 Box sketches Outlet to test piping Window cool/clean Air inlet Tungsten sample 21

22 Tests Cases (examples) Results Velocity: 0.5, 5 m/s Mass remaining in solid Humidity: Air, Steam Mass on filter Cooling: No, Water Size distribution Reproduce: 2 => 16 tests 22

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