TEMPERATURE AND STRESS IN ALCATOR C-MOD DUE TO THE DIVERTOR UPGRADE

Transcription

1 THERMAL ANALYSIS TO CALCULATE THE VESSEL TEMPERATURE AND STRESS IN ALCATOR C-MOD DUE TO THE DIVERTOR UPGRADE Han Zhang 1, Peter H. Titus 1, Robert Ellis 1, Soren Harrison 1,2, Rui Vieira 2 1 Princeton Plasma Physics Laboratory, Princeton, NJ, hzhang@pppl.gov 2 Massachusetts Institute of Technology Plasma Science and Fusion Center, Cambridge MA * This work is supported by US DOE Contract No. DE-AC02-09CH11466.

2 Outline Introduction of the model Steady state analysis with outer divertor at 600 C Transient analysis Conclusions

3 2D thermal model of Alcator C MOD cryopump LN2 shield shelf Existing Outer Divertor MSE shield Port Inner divertor dome Outer divertor A frame EF1 heat shield Thermal shield More details, please see: SOREN HARRISON et al., Motivation for the C Mod Outer Divertor Upgrade, TOFE2012 Longer pulse length: up to 4 seconds for full power, 9MW hot divertor at 600 C

4 From Ref 3 (PETER TITUS et al., Alcator C-Mod Inner Divertor Upgrade Design and Analysis, SOFE2002): The Inner Divertor is Sensitive to the Thermal Differential Between the Gridle and the Vessel Wall. The Inner Divertor After the Girdle Reinforcement Displaced Shape with 100 K delta T between Girdle and Vessel. The faceted bending of the shell relieves the stud loads

5 D B E Radiative surfaces (/AUX12). A Outer surfaces of the vessel with cryo cooling. G Emis=0.2~0.4 K J H

6 Lower half Lower half radiation surfaces

7 Steady state analysis with outer divertor at 600 C (emis=0.4) ( C) ( C)

8 Temperature ( C) ( C) Almost 400 C Outer divertor Tiles Thermal shield A frame

9 Totally 22.8 KW W W W Totally 22.8 KW 249.7W W W W W W W

10 heater data from Lihua Zhou, MIT Power (kw) of vessel heaters Nov /18/2012 Serial # Location Location on Power for symbol Location name plots full scale 1 A top Inner wall, top Approximate power on plots Approximate % (kw) in use* right panel, #3 from top right ihpanel, #4 B 2 A bottom Inner wall, bottom from top A B+E EF and EF1 top right panel, #1 from top B EF1 top 1.75 E EF top Vessel centerline 1.75 kw? C 19.8 kw B+E 7 kw kw 8 kw D 3.6 kw 3 kw E 12 kw? 4 C Vertical port, top 5 D Cutout, top 6 F Horizontal port 7 G Outer wall left panel, #1 from top left panel, #3 from top left panel, #5 from top right panel, #5 from top H+K EF and EF1 bottom right panel, #2 from top H EF bottom K EF1 bottom I Vertical port, bottom left panel, #2 from top left panel, 10 J Cutout, bottom #4 from top Sum of line 1,2,3,,9, Electrical power monitor (kw): 55 Note: "*" is duty-cycle during machine operation. A 11.5 kw 4 kw H+K K kw? kw 6 kw J 3.6 kw 3 kw I 19.8 kw 7 kw H 12 kw? G Legend: Location symbol Full scale power (kw) On use power (kw) kw 20 kw F 13 kw 6 kw

11 Sint (Pa)

12 Sint (Pa) 65 C 1 10 C 25 C 2 ss 304 yield = 40 ksi (275 Mpa) Hand estimation of the stress at this point: L=0.0817m, thickness=0.013m, E=2e11, thermal expansion coefficient=1.7e 5, temperature difference delta T=(65 10), bending stress=137.7 Mpa; Hoop stress=190.3 Mpa. This stress is mainly due to the temperature difference of area 1 and 2. If in reality, the wall temp can be controlled to be more uniform, either providing more cooling to the EF1 pocket to lower the temperature of its top, or heating the vessel floor slightly to reduce the temperature difference between the two areas, the stress here should be reduced.

13 The thermal stress at the corner was reduced to 233 MPa by heating the floor. A. Temperature B. Thermal stress ( C) (Pa)

14 Transient analysis: temperature evaluation points Inner wall heat loss 11.5KW/2.823m^2/200K wall temp (wall_t1) MSE temp Outer wall heat loss 1.4KW/2.61m^2/200K wall temp (wall_t2) wall temp (wall_t3) Nose temp Back plate temp EF1 heat loss 1.6KW/0.77m^2/200K EF heat loss 3.6KW/2.75m^2/200K Case 1: Emis=0.4/0.2, long pulse, 8MW, 4s, 1200s cooling; Case 2: Emis=0.4, hot div, 8MW, 3s, 1200s cooling

15 Emis=0.4, long pulse, 8MW, 4s, 1200s cooling Nose temp ( C) Emis=0.2, long pulse, 8MW, 4s, 1200s cooling 1727 Nose temp ( C) MSE temp ( C) 767 MSE temp ( C)

16 Emis=0.4, long pulse, 8MW, 4s, 1200s cooling Back plate temp ( C) Emis=0.2, long pulse, 8MW, 4s, 1200s cooling 927 Back plate temp ( C) Wall temp ( C) Wall_t Wall_t2 152 Wall_t Wall temp ( C) Wall_t1 Wall_t2 Wall_t3

17 Emis=0.4, hot div, 8MW, 3s, 1200s cooling Nose temp ( C) Emis=0.2, hot div, 8MW, 3s, 1200s cooling Nose temp ( C) MSE temp ( C) 767 MSE temp ( C)

18 Emis=0.4, hot div, 8MW, 3s, 1200s cooling Emis=0.2, hot div, 8MW, 3s, 1200s cooling Back plate temp ( C) Back plate temp ( C) Wall temp ( C) 207 Wall temp ( C) Wall_t1 Wall_t2 Wall_t Wall_t1 Wall_t2 Wall_t

19 Conclusions 1. Results show that the differential temperature between inner divertor girdle structure and inner vessel wall is ~70 C so that the stress on the studs will be within allowable stress levels. 2. Heat loads on vessel inner and outer walls, EF and EF1 pockets and thermal shields are read out and comparable to existing data. 3. the model was used to calculate stresses based on these thermal results. Initially, the peak stress of 333 MPa occurred at the EF1 pocket, which exceeds the allowable stress. This stress was reduced by making the EF1 pocket and floor temperatures more uniform, by either providing more cooling to the EF1 pocket to lower the temperature of its top, or heating the vessel floor slightly to reduce the temperature difference between the two areas. A run with heatingof the vessel floor shows that this stress can be reduced to 233 MPa. 4. Transient analysis with 8 MW of plasma power, for both long pulse and hot divertor scenarios, shows that the vessel and component temperatures are within allowable values. 5. When combined with plasma energy deposition, the outer divertor can be heated to 600 C within thirty minutes. Hot divertor will expand 6~7 mm radially and 1 mm vertically, which will be tolerated by the A frame supports. 6. This model was also used to simulate a variety of scenarios, including faulted operational conditions, like loss of cryo cooling and loss of vacuum pressure resulting from a window breaking.

20