NUMI Nu MI Decay Pipe Nu MI Decay

NUMI Nu. MI Decay Pipe Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 1 2 m diameter 677 m long 3/8 inch = 0. 95 cm thick Welded stiffener rings to meet vacuum code Water cooled by 12 plastic-coated copper pipes embedded in concrete

NUMI Decay Volume Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 2 • Vacuum is the default (~1 torr adequate) – helium fill is the backup if a significant leak develops • Entrance window 1. 5 mm thick stainless steel, 1 meter diameter welded to thicker material that extends to 2 meter diameter. – Designed to meet the requirements of the ASME Pressure Vessel Code • No shutter • Alignment tolerance is pair of circles, 97. 155 cm and 100. 965 cm radii – Alignment is achieved by utilization of a GPS network on the surface, transferred underground by sight-risers, geo-theodolite, etc.

NUMI Radiation Shielding Design Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 3 • Decay pipe – surrounded by poured concrete shielding (Tunnel Boring Machine was 6. 55 m in diameter) – Space for a 112 cm width walkway on one side is provided. – Pipe and tunnel centers are offset as needed to shield groundwater. (The limit on concentration of radio-nuclides in groundwater at the tunnel walls depends on the amount of water inflow) • Walkway – residual gamma activity 2 m. Sv/hr (30 day activation, 1 day cool-down) • Hadron Absorber – Design goal is residual gamma activity < 1 m. Sv/hr on the walkway side

NUMI Sample Decay Pipe / Shielding Cross Section Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 4 Target hall to absorber secondary access Decay pipe concrete radiation shielding, density 2. 1 g/cm 3 Relative centers vary along length

NUMI Energy Deposition, Cooling Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 5 • Decay region power deposition – 63 k. W in 1 cm thick steel decay pipe – 52 k. W in shielding concrete – Peak deposition in the steel is ~360 W/m (~ 50 m from target hall) – Drops to 20 W/m (at ~610 m) – Heat is removed by twelve copper water-cooling pipes, limiting decay pipe temperature to ~ 50 deg C • Absorber core – 8 modules of aluminum with dual water-cooling paths • 30. 5 x 129. 5 cm 3 each • 8 k. W peak power in one module (normal beam conditions) – followed by 10 plates of steel, each 23. 2 cm thick. • Total power in Absorber region: 60 k. W (nearly entire 400 k. W beam power in accident condition)

NUMI Absorber / Cavern Cross Section Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 6 Steel blocks Absorber core beam west Concrete blocks Steel block dimensions are 132 x 66 cm 3 Egress path

NUMI Absorber Core Nu. MI Decay Volume / Absorber Jim Hylen (FNAL) NBI 02 March 15, 2002 Page 7 Steel slabs Aluminum slabs 1. 3 m Two water lines from each Al. block run back through holes in other blocks.