UCN Phase 2 Design Status

September 10, 2002

Design Components

• Bulk Shielding

• Target Crypt

• Cryogenic Insert

• Target Insert

• UCN Port

• Beam Window

• Cooling System

• Radioactive Effluents

Bulk Shielding Design

• To include steel and concrete around the moderated target sufficient to maintain dose rates for 10 μA below:– 0.1 mrem/h on the experiment floor– 100 mrem/h above the shielding– 5 mrem/h in corridor to Line B tunnel

• Anticipate target will normally be operated at less than 5 μA

Bulk Shielding Design Continued

• Provided 4.5 feet of steel and 3 feet concrete above target crypt, dose rates locally on the order of 10’s of mrem/h above the shielding for 10 μA

• Dose rates on the experiment area floor average ~0.08 mrem/h for 10 μA primarily due to scattering from roof, walls, air, and ground

Bulk Shielding Design Continued

• Preliminary calculations of bulk shielding dose rates conservatively based on assumptions that proton beam completely interacts in tungsten but that the tungsten provides no shielding

• Target crypt is assumed to be filled with graphite

Target Crypt Design

• Crypt will be lined with aluminum and filled with graphite

• Include a 6-foot graphite beam stop

• Tungsten target will be centered in a 27-inch cube of beryllium

• Above the target a 13-inch diameter penetration will receive the cryogenic insert

Target Crypt Design Continued

• Crypt will receive target insert from the side

• Beam stop cooling is being included in the design and coolant lines will be routed to system components to be installed on top of bulk shielding

Cryogenic Insert Design

• Will be inserted into the target crypt from the top

• Lower end will contain a 4 cm thick liquid deuterium region, not to be credited in the shielding design

• Above the deuterium to an elevation above the UCN port will be a vacuum chamber

Cryogenic Insert Design Continued

• Height of the vacuum chamber is yet to be determined but will be based on trade-offs between experiment impact and plug shielding requirements

• A 3-inch penetration will be required for service and instrumentation lines

• Insert design will include shielding above the vacuum chamber but additional shielding may be necessary above the insert

Target Insert Design

• No engineering drawings have been drafted but design is expected to include:– Consist of shielding equivalent to the bulk– Include at least one step to minimize streaming– Have small diameter penetrations will multiple bends

for target coolant lines– Coolant lines to be routed to cooling system

components installed on top of bulk shielding– Will facilitate remote removal and transfer of target to

a shielded cask

UCN Port

• Will lie in a 6-inch square penetration in the bulk shielding, 4 feet above the beamline elevation, with two 45° bends

• Outer pipe will have an external diameter of 4 inches

• Plan to line penetration around the UCN pipe to minimize radiation streaming

Beam Window

• Mates with hole in the target crypt wall

• Includes cooling lines that will be routed to system components installed on top of bulk shielding

• Will be removable with beam line through bulk shielding by retracting into the Line B tunnel

Cooling System

• Design only in conceptual stages

• Evaluating use of a helium gas primary loop for the beam window, target, and beamstop

• Plan to installed cooling system components on top of the bulk shielding at the south end

Radioactive Effluents

• Target crypt void space is minimal and to further minimize air activation:– Plan to provide a helium gas supply to the

target crypt with an exhaust into the Line B tunnel

– Plan to install a sealed, helium filled beamline segment between the beam window and the target

Radioactive Effluents Continued

• Target crypt will include a drain in the bottom with piping to the a Line B radioactive waste drain, regardless of whether or not all primary coolants are helium