1. Baseline Design for Braidwood
Victor Guarino
Group Leader - Mechanical Engineer
Argonne National Laboratory
High Energy Physics division
Victor Guarino
Mechanical Support Group
High Energy Physics - ANL

2. BaselineWork Accomplished
Written 50 page detailed design report.
Defined detector Parameters
Identified and evaluated industry standards for designing and fabricating Acrylic structures.
Defined detector Assembly procedures.
Performed detector Structural Analysis
Performed structural analysis for detector Support Structure
Defined and costed required Facilities and worked on site location.
Technology Transfer trip with Reynolds Polymer Technology.
Victor Guarino
HEP-ANL

3. Detector Parameters Three Volumes
Inner volume 0.1% Gadolinium – 3.8m Dia.
Middle Volume – no Gadolinium – 4.8m Dia.
Outer Volume – Mineral oil without scint. or Gadolinium – 6.5m Dia.
Victor Guarino
HEP-ANL

4. Detector Design
Outer steel sphere will be constructed in two halves joined with a flange to permit access if needed to PMTs.
6 vertical and 3 horizontal straps will support each inner sphere.
All spheres will be simultaneously filled to reduce forces on internal support structure.
Victor Guarino
HEP-ANL

5. Designing With Acrylic
Laminated Glass
Scratch resistant
High strength and stiffness
Very brittle
Low impact strength
Acrylic
Soft and scratches easily
Potential to yellow in UV light
Higher impact strength than glass
Polycarbonate
Cast Acrylic is the material of choice
Commonly used for large structures
Only material allowed in PVHO
Stronger than Polycarbonate and does not have the brittleness of glass
Victor Guarino
HEP-ANL

6. Designing With Acrylic Fracture Mechanics
Acrylic structures can fail at stresses lower than yield in a brittle manner due to unstable crack propagation.
Design to a leak before failure criteria.
Design stress of ~507psi is calculated on textbook values of fracture toughness.
ASME PVHO -1,2 standards provide additional guidelines for maximum crack size and inspection.
Cracks may develop during service due to chemical attack, thermal gradients, and fatigue. This may be a significant problem with pseudocumene.
Victor Guarino
HEP-ANL

7. Detector Assembly
Inner acrylic sphere will be completely assembled off-site.
Half spheres of middle acrylic sphere will be assembled off-site.
Top half of middle sphere will be attached to inner sphere and then this assembly attached to bottom half sphere.
Top half of outer steel sphere will be attached to middle sphere and then this assembly attached to bottom half sphere.
Victor Guarino
HEP-ANL

8. Detector Assembly
Victor Guarino
HEP-ANL

9. Detector Assembly
Victor Guarino
HEP-ANL

10. Detector Assembly
Victor Guarino
HEP-ANL

11. Detector Assembly Acrylic joints are a potential problem
SNO had many problems
Shrinkage during bonding caused deformation and internal stresses – potential source of future crazing.
Thinner walls (8-12mm) should minimize this problem.
Bonded joints need to be polished on the inside and outside. This is not possible on all of the joints. What is the optical quality of joints not polished on the inside?
A possible 2” wide band not polished on the inside on the equator of the middle sphere.
Victor Guarino
HEP-ANL

12. Detector Structural Analysis
Three Loading Scenarios examined
Empty and being moved
During filling process
Full and being moved.
Calculations performed:
Sphere thicknesses based on supporting the entire weight of the liquid.
Internal support structure of spheres supporting only the weight of the spheres.
External support structure of detector to minimize deflections and induced stresses in spheres.
Victor Guarino
HEP-ANL

13. Detector Structural Analysis
Sphere thicknesses:
Inner Acrylic Sphere 10mm
Middle Acrylic Sphere 14mm
Outer steel sphere 6mm
6 vertical and 3 horizontal straps will be used to locate inner spheres
No straps on the bottom of the sphere because it is felt that the sphere self weight is enough to insure that they do not float.
Victor Guarino
HEP-ANL

14. Detector Structural Analysis
Victor Guarino
HEP-ANL

15. Detector Support Structure
Victor Guarino
HEP-ANL

16. Facilities Near/Far Detector Buildings: $300k for surface building
300 tons overhead crane 40’ x 60’ travel and 550’ lift capacity
At the far detector site there will be office space in a trailer.
Utilities, lighting, Heat in each building
$300k for surface building
$1.4M for crane
~$15k for trailer for office space
Victor Guarino
HEP-ANL

17. Braidwood Near Detector Site
Victor Guarino
HEP-ANL

18. Comments from trip to Reynolds Polymer
800 psi design stress for acrylic
Based on year tests done by Navy
No crazing found in flexural loaded samples with 810 psi tensile stresses
Bonds are design at 85% of this value
Standard bond requires access to both sides of joint.
Making two separate hemispheres allows full access
Special well joint then needed for assembling full sphere
2” wide area of poor transparency
Inner sphere could avoid this by having large enough chimney for person access (>18” ID )
Chimney design requires carefully designed ring to reduce stress concentrations
Curved Acrylic pieces less than 1” thick are formed from stock cast sheet sizes.
Surface flaws are repairable.
Standard design guarantee from Reynolds is 10 years
We must conduct tests to check compatibility of scintillator solution
Grand Sasso rejected Acrylic after identifying chemical compatibility problems
Maximum piece size for the detector is a trade off between shipping costs and on-site bonding effort.
Need to sample acrylic for background radiation.
Reynolds can provide samples of bonded joints to test light transmission.
Victor Guarino
HEP-ANL

19. Conclusion
We need to begin immediately the pseudocumene/acrylic compatibility.
Preliminary Baseline Design has been completed. Trip to Reynolds confirmed basic design/assembly of acrylic spheres.
More R&D is needed on acrylic sphere construction/bonding and cost estimating.
Outer steel sphere construction/geometry needs additional thought.
Detailed design and the development of an R&D plan will be completed in the near term.
Victor Guarino
HEP-ANL