Status of JSNS
        and
R&D on mercury target
           J-PARC
    Neutron Source Section
            Leader
        M...
!quot;#$%&'
                              ()*)+!$*$,
                               @AMNCOPQR
                     78'9:;
...
First observation of neutrons at JSNS

        t~9.2ms, l~2.6A, E~12meV
                                    On 30th May 20...
MLF Proton Beam History in FY2008
                                                                                        ...
Proton Beam Transport Facility
! s:TH'Z_HH^kk^_`^`V'kWTUW:n'_`'L8'cT
   o:U'i^UkW'g:TH'km_W'iU_H'TZZ:j:UTW_U'm^W'H:UZ[U'WT...
Target station at JSNS

              Target station




                                                           Irradi...
JSNS Mercury Target System
Hg target : Cross-flow type, Multi wall vessel
           Hg leak detectors (Electric circuit, ...
JSNS Mercury Target Vessel
         Heavy water
                         Cross flow type
                         Length 2...
JSNS PM pump
Optimization of duct design
FEM analysis on pressure, Lorentz force & Hg flow
Inner wall :3mm
Outer wall :5 m...
Maintenance in Hot Cell
                              Dose Estimation
• Several maintenance ! Done by hands-on
    – Longe...
Maintenance in Hot Cell
                Measurement and Future Entry
                                              Variati...
First observation of vibarational signal
  related to pressure waves at target
Laser Doppler Vibrometer           Measured...
Pressure dynamic                                          Hg
                            Mercury target



response in mer...
What is cavitation bubbles
        in mercury
R&D on mitigation technology




       Violently bubble collapsing
Off-line test on pitting damage by MIMTM




  Inventory : 5 L
  Stagnant
  Flow : 0.3m/s
         +Bubble ca.0.1%
Off-beam test by MIMTM


                                    Isolate pits



       103
                   104

          ...
Fatigue strength degradation by pitting damage
                                                       Kolsterise As receiv...
Lifetime estimation of target vessel
taking account of pitting and irradiation damages   Pitting damage




              ...
Pitting damage reduces lifetime of target
                                                                        The life...
Damage dependency on flowing condition

                           Ae/A0=0.1                                              ...
Effect of flowing on bubble collapse behavior




 Micro-jet impact angle is inclined,
 because the growth behavior
 affec...
Effect of micro-jet impact angle
        on pit formation
Micro-jet impact angle determined by cavitation bubble collapsin...
Flowing improves lifetime ?
                                                                                              ...
Mechanisms of bubbling mitigation
                                                        3 mechanisms for each region
   ...
Pressure reduced by micro-gas-bubbles


       Normalized peak pressure, P v/Ps
                                          ...
Bubblers applicable to target
         to mitigate the pressure waves
         Venturi, Needle, Swirl bubblers were invest...
Bubble distribution in target vessel
 vNumerical simulation
    Spherical bubble
    Homogeneous bubble size distribution
...
Improvement in target system
    Gas supplying system         Compact target
                                  to reduce w...
Summary
vAt MLF in J-PARC, the first proton beam was injected into
   mercury target to yield neutrons on 30th May 2008.
v...
Bubble distribution in Hg flowing
                                                                                Hg
     ...
Pressure wave mitigation
          by A & B mechanisms
                                                               0.6 ...
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ESS-Bilbao Initiative Workshop. Status of JSNS and R&D on mercury target.

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Status of JSNS and R&D on mercury target
Masatoshi Futakawa (J-Parc)

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ESS-Bilbao Initiative Workshop. Status of JSNS and R&D on mercury target.

  1. 1. Status of JSNS and R&D on mercury target J-PARC Neutron Source Section Leader M. Futakawa
  2. 2. !quot;#$%&' ()*)+!$*$, @AMNCOPQR 78'9:; <=6>?>= 8 'H 78 L'9:; <=6>?>= -./01 (23456, @AIJCEFGK @AB8CDEFG
  3. 3. First observation of neutrons at JSNS t~9.2ms, l~2.6A, E~12meV On 30th May 2008 Cong ra tu l a tio n ! STUV:W'XL8YI8ZH TOF result shows the design of our neutron source is appropriate.
  4. 4. MLF Proton Beam History in FY2008 (As of Feb. 19, 2009) RFQ became instable 20 kW Beam 20 kW 20 kW Begin user Birth of neutron beam program First beam at 25Hz 20kW beam delivery Resume at 5kW Birth of 100kWeuiv. beam delivery muon beam Begin user program 100 kW equivalent for short period Resume Resume at 181 MeV at 5 kW AC power supply fault at RCS RFQ conditioning Technical problem in LH2 cryogenic system at MLF RUN19 in Oct. was dedicated to RFQ conditioning
  5. 5. Proton Beam Transport Facility ! s:TH'Z_HH^kk^_`^`V'kWTUW:n'_`'L8'cT o:U'i^UkW'g:TH'km_W'iU_H'TZZ:j:UTW_U'm^W'H:UZ[U'WTUV:W WmU_[Vm'I8b'HTV`:Wk'_o:U'LItquot;H'j_`V'g:TH'j^`: ! s:TH'hU_i^j:'T`n'h_k^W^_`'_`'WTUV:W kH__Wm'hU_i^j:u'`_'W^jW g:TH'hU_i^j:'_`'WTUV:W :]WUTZW^_` 'i^UkW'T'i:l'Wm_[kT`n'km_Wk'_gk:Uo:n l^Wm'TZW^oTW^_`'i_^j'kW[Zp'_`'WTUV:W H:UZ[UW iU_`W''(I8'HH+n^oqr TUV:W ^`a:ZW^_` hU_W_`'g:TH'j^`: IbI'c:;'de L'9:;'df
  6. 6. Target station at JSNS Target station Irradiated components handling Mercury target room Proton beam window Beam duct Target trolley
  7. 7. JSNS Mercury Target System Hg target : Cross-flow type, Multi wall vessel Hg leak detectors (Electric circuit, Gas monitoring) All components of circulation system on target trolley: EM pump, Compact heat exchanger, Surge tank, etc. Hot cell : Hands-on maintenance Vibration measuring system due to pressure wave Length 12 m Height 4m Width 2.6 m Weight 315 ton
  8. 8. JSNS Mercury Target Vessel Heavy water Cross flow type Length 2 m Mercury Weight 1.4 ton Hg flow velocity 0.7 m/s Hg inventory 1.5 m3 Mercury Flow vanes
  9. 9. JSNS PM pump Optimization of duct design FEM analysis on pressure, Lorentz force & Hg flow Inner wall :3mm Outer wall :5 mm with ribs 90kW-Motor Magnets 50 m3/h 1820 mm 0.2 MPa Mercury duct 840 mm
  10. 10. Maintenance in Hot Cell Dose Estimation • Several maintenance ! Done by hands-on – Longer than 10 years interval • Dose estimation – Considering residual Hg in piping and valves after Hg drain – Less than 100 µSv/h at > 12 m • 203Hg mainly contributes to the dose. • Hot cell entry is possible. Estimation in the Hot cell dose Hands-on maintenance area Handling Target vessel Device of 100 µSv/h exchange truck MRA In-cell filter
  11. 11. Maintenance in Hot Cell Measurement and Future Entry Variation of the counting rates • Separation products selectively during Hg drain adhere to the piping. – 188Ir, 185Os was strongly observed unexpectedly. – Dose rates for 188Ir, 185Os were increased during Hg drain. – Dose rate after drain is higher than before that. • Our dose estimation was so much underestimated. • Hot cell entry in future ! Additional Shield Additional shield of iron with 20 cm thickness will be prepared.
  12. 12. First observation of vibarational signal related to pressure waves at target Laser Doppler Vibrometer Measured vibration 0.8TP Range : ±0.1m/s 0.4TP Accuracy : 5x10-7 m/s < 300kHz Laser beam Inner plug Mirror assembly A Mirror assembly B Micro-multi -prism Target
  13. 13. Pressure dynamic Hg Mercury target response in mercury Flow guide Proton beam
  14. 14. What is cavitation bubbles in mercury
  15. 15. R&D on mitigation technology Violently bubble collapsing
  16. 16. Off-line test on pitting damage by MIMTM Inventory : 5 L Stagnant Flow : 0.3m/s +Bubble ca.0.1%
  17. 17. Off-beam test by MIMTM Isolate pits 103 104 Crack Combined pits 105 Pitting formation 106 107 20µm Futakawa, at al; J. Nucl. Sci. Tech. 40(2003) 895-904
  18. 18. Fatigue strength degradation by pitting damage Kolsterise As received Kolsterise 4e7 Kolsterise 1e8 1600 316LN20%CW As received 316LN20%CW 5e7 w/o pits 1400 Bending stress, MPa 1200 1000 with pits after 4e7 0.7 !f 800 0.6 !f 600 0.3 !f 400 Cracks 2 3 4 5 6 7 8 9 10 10 10 10 10 10 10 10 4E7 25µm Number of cycles to failure, N f 1E8 Futakawa, at al; Nucl Mat. 356(2006) 168-177
  19. 19. Lifetime estimation of target vessel taking account of pitting and irradiation damages Pitting damage Radiation damage
  20. 20. Pitting damage reduces lifetime of target The lifetime at 10 % failure probability under 1 MW will be reduced to ca 30 hrs by pitting damage: fatigue and radiation damages. 300 hrs for 0.8 MW, 2400 hrs for 0.6 MW. Beam profile 2500 hr at 25 Hz 10000 10000 100 Time to 5 dpa Failure probability P , % Pitting damage 8000 8000 Time to 10 % Pf , h f 75 Time to 5 dpa, h 6000 6000 50 4000 4000 25 2000 2000 0 0 0 0.33 0.45 0.6 0.8 1 0.33 0.45 0.6 0.8 1 Power, MW Power, MW Futakawa, at al ; NIM Vol 562(2006), 676-679
  21. 21. Damage dependency on flowing condition Ae/A0=0.1 Ae/A0=0.04 Ae/A0=0.02 250!m 0 0 0 -5 -5 -5 Depth, mm Depth, mm Depth, mm -10 -10 -10 -15 -15 -15 Stagnant_1 Flow_1 Flow+bubble_1 -20 Stagnant_2 -20 Flow_2 -20 Flow+bubble_2 Stagnant_3 Flow_3 Flow+bubble_3 Stagnant_4 Flow_4 Flow+bubble_4 Stagnant_5 Flow_5 Flow+bublle_5 -25 -25 -25 0 50 100 150 200 250 0 50 100 150 200 250 0 50 100 150 200 250 Distance, µm Distance, µm Distance, µm 5000 cycles, Flow velocity 0.3 m/s, Gas/Hg 10-3
  22. 22. Effect of flowing on bubble collapse behavior Micro-jet impact angle is inclined, because the growth behavior affected by the flowing. Tanaka, et al, CAV2006 (2006)
  23. 23. Effect of micro-jet impact angle on pit formation Micro-jet impact angle determined by cavitation bubble collapsing behavior that is affected by mercury flowing condition. Pit depth is affected by jet-angle. Almost 1/5 at 45 degree.
  24. 24. Flowing improves lifetime ? Flowing decreases the failure probability due to the pitting damage, so that, increase the Beam profile lifetime of target. 2500 hr at 25 Hz 10000 100 10000 Failure probability P , % Time to 5 dpa Stagnant Stagnant 8000 8000 f Flowing Time to 10 % Pf , h 75 Flowing Time to 5 dpa, h 6000 6000 50 4000 4000 25 2000 2000 0 0 0 0.33 0.45 0.6 0.8 1 0.33 0.45 0.6 0.8 1 Power, MW Power, MW
  25. 25. Mechanisms of bubbling mitigation 3 mechanisms for each region Center of thermal shock : A B Absorption C A Propagation path : B Attenuation Negative pressure field : C Suppression Bubble<50 µm C B A Contraction Thermal diffusion Thermal Pressure Kinetic Thermal expansion wave energy energy Absorption of the thermal Suppression against cavitation Attenuation of the pressure expansion of mercury due to the bubble by compressive waves due to the thermal contraction of micro bubbles pressure emitted from gas- dissipation of kinetic energy bubble expansion. Absorption Attenuation Suppression
  26. 26. Pressure reduced by micro-gas-bubbles Normalized peak pressure, P v/Ps Single phase !=0.05% 100 !=0.10% !=0.30% !=0.50% !=1.00% 10-1 10-2 Ps=25MPa 10-3 0.1 1 10 100 1000 Bubble radius, µm Expected pressure reduction by absorption and attenuation Okita et al., CAV2006 (2006); J Fluid Sci Technol 3 (2008) 116
  27. 27. Bubblers applicable to target to mitigate the pressure waves Venturi, Needle, Swirl bubblers were investigated in mercury He gas supply Venturi Needle Venturi Swirl Bubbles < 50 µm, that is most effective to reduce pressure waves, is successfully generated by using in swirl bubbler.
  28. 28. Bubble distribution in target vessel vNumerical simulation Spherical bubble Homogeneous bubble size distribution Assumed bubble size distribution Bubble distribution is very dependent on the position of bubbler, which is affected by flow pattern. vExperiment in water and mercury Curving flow channel effect Bubble coalescence effect Verification of conventional codes; Star-CD, Fluent, etc. Water loop test at JAEA Mercury loop test at TTF
  29. 29. Improvement in target system Gas supplying system Compact target to reduce waste volume to control gas pressure and install bubblers and flow rate Bubbler Gas supply unit
  30. 30. Summary vAt MLF in J-PARC, the first proton beam was injected into mercury target to yield neutrons on 30th May 2008. vIn mercury target for pulsed spallation neutron sources, the cavitation damage induced by pressure waves is a top issue to increase power level to MW-class. vOne of prospective techniques to mitigate pressure waves is to inject micro-bubbles into the mercury. vSwirl bubbler can generate bubbles <50 µm in mercury, that is expected to effectively mitigate pressure waves. vCollaboration with SNS is important. Mockup tests of target vessel with bubblers will be carried out using TTF loop to evaluate bubbles’ distribution in target vessel.
  31. 31. Bubble distribution in Hg flowing Hg Mercury target A By FLUENT Flow guide B Proton beam 1m/s 5 mm C 0.5 mm D Bubbling position dependency on distribution: 0.05 mm B+D positions for bubbles to reach around window and max. peak position. Rising effect on bubble distribution
  32. 32. Pressure wave mitigation by A & B mechanisms 0.6 W/O Bubbling Bubbling 0.4 Velocity, m/s 0.2 0 Proton -0.2 beam -0.4 Hg loop -0.6 0 0.2 0.4 0.6 0.8 1.0 with bubbler Time, ms SNS/JSNS collaboration on pressure wave issue 2005 WNR test for bubble mitigation technology On-beam test was carried out by using WNR facility to investigate the bubbling effect on the pressure waves caused by proton beam injection. The displacement velocity measured by a Laser Doppler Vibrometer L.D.V. was reduced by bubbling.

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