DUNE FSD Cryostat SoW.pdf

STATEMENT OF WORK

Cryostat order for the Full-Scale Demonstrator Test Stand at SLAC

Jan 2021

DUNE FSD Cryostat

1. Background SLAC National Laboratory (SLAC) is a DOE Federally Funded Research and Development Center. The Lab has been tasked to build a test facility for full scale cryogenic detectors in liquid Argon to support the international project DUNE, Deep Underground Neutrino Experiment, a leading-edge, international experiment for neutrino science and proton decay studies.

2. Scope/Task A double wall vacuum insulated cryostat is required to test full scale Time Projection Detectors in Liquid Argon at a slightly above atmospheric pressure. This test stand is intended to support high voltage research needed to retire risks associated with the primary DUNE ND-LAr system. The TPC will be immersed in liquid Argon in order to simulate environmental conditions expected in the full system.

3. Description/Requirements The FSD Cryotank is a double wall vacuum insulated vessel, 170“ tall and 74” wide. The inner vessel,146” tall and 65” wide, will be filled with research grade purity Liquid Argon at the stable temperature in the range 87 K to 93 K.

The cryostat has a flask design with an open mouth on the top, closed by nested lids not part of this scope. The bottom is closed by a standard ASME flange dished head (SD-

TYPE.

The top flange is 1” thick and has a double groove for ½” standard Parker o’ring. The tolerances and the surface finish of the groove must be done according to Parker requirements listed in the reference [7]

The thicknesses of the side wall of the inner and outer vessel are expected to be 0.125” and 0.25” respectively. We expect the thickness of the end dish to be 0.125”. The vendor should propose thicker walls if the value proposed are not deemed sufficient to achieve the required MAWP per ASME.

A drain port of 1” ID with a vacuum jacket OD 1.48” is welded at the bottom. The VJ starts at the outer vessel. The inner pipe of the drain port has a bellow to strain relief the inner form the outer vessel. The bottom of the cryostat is completed by an apron welded to anti-seismic brackets.

The Maximum Allowed Working Pressure of the top of the inner vessel must be +10 psig at 87 K. The cryostat must be able to stand also 15 psi negative pressure when evacuated for leak testing or prior to the transfer of the Liquid Argon. When filled with LAr at 87K , the liquid column height is 160” and the hydrostatic pressure at the bottom is 550 mbarg.

The MAWP value must be certified according to ASME BPVC.VIII.1– UG-99 or UG-100

The vacuum gap must be insulated by MLI insulation, 20 layers/cm or better, The Inner and outer vessel will be spaced by G10 structural rings or made with a material with equivalent or lower thermal conductivity

A pump-out port on the vacuum vessel, for the vacuum pumping of the insulation gap is required. The pumping will be done periodically only for the maintenance of an adequate vacuum insulation.

The inner vessel surface and the drain port must clean according to current standard of cryogenic vessel made in Stainless Steel and that are pumped to High Vacuum : steam or high-pressure cleaners with the addition of special cleaning agents.

All the vessels need to be done with Stainless Steel 304 or compatible with the temperature and pressure requirements. In addition, the following requirements need to be considered:

1. The fabrication and handling of the components shall be designed according to ASME BPVC.VIII – Division 1

2. All welding in accordance with ASME BPVC.VIII – Division 1. Seal welds must be vacuum tight with a leak rate to be less than 10-6 cc/s of Helium gas.

3. Any deviation from these specifications shall be submitted to SLAC for approval.

4. Vacuum test to be performed after final machining. Parts must be cleaned and dry before test.

5. Inner and outer vessel do not require additional surface finish beyond standard hot-rolled available from the base material

6. Parker O-Ring handbook ORD5700

4. Additional Scope A full circular thin lid (0.125”) bolted to the top flange, protecting the Inner vessel from contamination during the transport and the installation at SLAC. The lid does not have pressure requirements. Once closed by the protection lid, the pressure inside the inner vessel must be always equalized with the external atmospheric pressure and protected by a pressure relieve device set at few psig

5. Conclusion The key requirements are:

Inner vessel diameter 65” Inner vessel depth 146” Inner Vessel total height 170” MAWP at the top of the dewar of 700 mbarg at 87K Hydrostatic pressure at the bottom of 550 mbarg at 87 K (assuming liquid level at

4 m, LAr density at 87K 1’400 kg/m3) Total pressure at the bottom is 1250 mbarg at 87 K.

For all the other dimensions, the vendor is encouraged to propose technical options that meet or exceed the requirement according to the status of the art of the pressure vessel construction

Deliverables

Qt.y 1, Double wall vessel as per drawing sa002 and requirement in chap.5

Qt.y 1, Cover Lid OD74” x 0.125” thick

Results of the pressure test or structural analysys showing compliance with ASME code

Welds and material certifications

Technical contact:

Marco Oriunno SLAC National Accelerator Lab 2575 Sand Hill Rd MS 96 Menlo Park, CA 94025, U.S.A.

Email :

oriunno@slac.stanford.edu Phone: +1.(650).926.4318