R.Valbuena NBI March 2002 CNGS Decay Pipe Entrance Window Structural and Thermal Analysis A.Benechet, P.Cupial, R.Valbuena CERN-EST-ME

R.Valbuena NBI March 2002 Summary 1.Structure analysis Geometry Material properties Boundary conditions Loading cases Results 2.Thermal analysis Assumptions Material properties Boundary conditions Loading cases Results 3. Thermal and Mechanical Stresses 4.Thermal shock 5.Conclusions

R.Valbuena NBI March Structure Analysis 1.1 Geometry external diameter : 1665 mm internal diameter :1400 mm spherical radius : 1891 mm thickness: 2 mm 1.2 Ti 40 properties Young Modulus105 GPa Yield Strength 280 MPa Ultimate Tensile Strength R m 460 MPa 1.3 Boundary Conditions Fixed in-between flanges

R.Valbuena NBI March Loading cases Case 1: 0.3 MPa test pressure Case 2 : 0.1 MPa service pressure 1.5 Results for Case Analytical : Allowable stress according to French Pressure Vessel Code (CODAP) : For Titanium : under resistance test condition: -under normal service condition : =>The condition is fullfilled

R.Valbuena NBI March FEM Analysis deformations: Von Mises stress: The membrane stress is equal to those computed analytically. The red zone is typical of such spherical shell under pressure (edge bending stress).

R.Valbuena NBI March 2002 The stress in the red zone attains 240 MPa. It is due to the fixed nodes close to the curvature change. Deformation and stress values are comparable with those measured on a prototype with strain gauges:

R.Valbuena NBI March 2002 Equivalent von Mises Stress in MPa on external and internal window faces

R.Valbuena NBI March Result for Load Case 2 : P=0.1 MPa Location of equivalent von Mises Stresses Stress values in MPa Safety Factor wrt UltimateTensile Strength Safety Factor wrt Yield Strength R=715 mm R= 654 mm <R< Conclusions : Good agreement between analytical and FEM results except for fillet zone which has been modeled in a conservative way. The window is safe according to CERN safety rules.

R.Valbuena NBI March Thermal Analysis 2.1 Assumptions  Transient analysis  Run duration 200 days  Initial temperature (materials and air) 15°C 2.2 Material properties :

R.Valbuena NBI March Boundary Conditions: Case 3 : Natural convection : temperatures : Air 15 °C Window 22 °C Free convection coefficient: Case 4 : Natural and forced convections : Pipe diameter 12 mm Water temperature 15 °C Flow rate 10 l/mn Forced convection coefficient:

R.Valbuena NBI March Loading Constant heat Generation: ~30 W in the window ~430 W in the flanges Proton Flux Density : 1 GeV = Joule

R.Valbuena NBI March Results Case 3 (free convection) 1 C A B D A : window B : mating flange C : cooling pipe D : flange E : Concrete Numbers show measuring points location 9 E

R.Valbuena NBI March 2002 Temperature evolution during 10 days of cooling time

R.Valbuena NBI March 2002 Static Stress [MPa] Thermal Stress [MPa] Global Stress [MPa] Safety Coefficient wrt Yield Strength limit Safety Coefficient wrt Ultimate Tensile strength Stresses close to the fillet

R.Valbuena NBI March Case 4 (free and forced convections) Temperature rising time : 4 hours Maximum temperature on window apex : 32°C Good efficiency of the water cooling for the flanges and weak impact on window temperature

R.Valbuena NBI March 2002 Temperature evolution during 2 hours cooling time Window and Flange Temperature profiles

R.Valbuena NBI March Thermal and Mechanical Stresses Static Stress [MPa] Thermal Stress [MPa] Global Stress [MPa] Safety Coefficient wrt Yield Strength Safety Coefficient wrt UltimateTensile Strength

R.Valbuena NBI March CODAP Verification  Test Pressure : P=0.3 MPa Service Pressure : P=0.1 MPa

R.Valbuena NBI March Thermal Shock Full beam on the window : 3.5x10 13 p/pulse => 3.34x10 18 p/s

R.Valbuena NBI March 2002 After 2 pulses with q=2.6x10 12 W/m 3  T = 22 °C

R.Valbuena NBI March 2002 After 1 pulse 10.5  s with q=2.6x10 12 W/m 3  T = 11 °C Dynamic stress negligible

R.Valbuena NBI March Conclusions: Free Convection inefficient in a CONFINED SPACE => Thermal stresses : 40 MPa on the window 230 MPa on decay tube / concrete interface With the cooling system : Temperature stabilised at 32 °C, very low thermal stresses In the event of the beam missing the target, the interlock shall react in less than 1’. The window is safe according to CODAP See Technical Note EST-ME/ EDMS n°323691