JPARC-ν Decay Volume
M.Sakuda (KEK)
11 November 2003
In collaboration withA.Ichikawa, E.Kusano, Y.Yamada, T.Kobayashi, H.Noumi,M.Takasaki, T.Ishida, Y.Hayato, Y.Oyama, T.Suzuki, T.Miura
1. Decay Volumez

Requirements

zDesign

2. Construction Status
3. Summary and schedule1. Decay Volume (DV)
Requirements
 0.8MW of energy loss in DV region
3NBT@4MW operation.
zRadiation safety regulation
zCooling
zMechanical stability
110m
 Tight schedule
Construction of 3NBT tunnel will
begin from JFY2004. A part of DVbeneath 3NBT, 30m long, must becompleted in May, 2005.
280m Near Detector
SKPrimary Proton
beamline
Target Station
Decay
Volumeµ pit

50GeV PS

Heat Generated at Decay Region (4MW)
Collimator

suppresses particles effectively.

Decay Volume
10m(20cmt) 16mmt

Z=0Target Station

Steel plate (Pipe)

Concrete

Design of Decay Region1) Mechanical shape•(square) box is cheaper than Ο (cylinder) by 20-30%.

•16mm-thick steel is strong enough to endure the weight of 2m
concrete during the construction and the thermal stress (later).

•One plate is 4mx2m wide, welded with ribs embedded inconcrete. In addition, anchors every 4.5m pitch.

2) 5.0-5.9m thick concrete and 6m of soil surrounding the iron box isneeded for radiation safety regulation <5mSv/h. (Oyama’s report)
3) Filled with Helium•

About 7% more flux than air.

•Less Tritium rate by a factor 1/3 than air. (<30Bq/cc)

4) Cooling under 4MW for Iron <60deg, Concrete <120deg•

20 Plate-Coils (S=6.7cm2) with 1.2m/sec water flow

Design of Decay Region
1.5m x 1.9m at the entrance

Decay Pipe

Top View

Side View

114m

3.0m x 5.4m at the end

Decay Volume common with SK/HK
ハイパーカミオカンデの候補地

Beam View
DV center

0.784°

3°3°2°2°

SKHK
0.02°

SK
1.51°

3.11 ° (OAB2 ° beam axis )3.64 ° (OAB2.5 °)4.16 ° (OAB3 °)Best )Fit 3.43 °(OAB2.3 ° Beam Axis)~10km

Decay Volume
HK2°3°

2. Construction of Decay Volume- Iron Plates (16mmt) with PlateCoils •Production in 2002-2003• 71.4m(/110m) plates purchased.

Platecoils (1cmtx6.5cmw)

Platecoils
welded oniron plate(continued)
Complete
Pressure test

２００３年３月

Platecoil for Water Cooling System•Many industrial applications-Cheap and reliable• Welded on the inside wall ofdecay pipe
- Area 6.7cm2 ,1.2m/sec

Joint
Decay pipe

Experimental
Instrument

Beer Vessel

Chemical Plant

Arrangement of Watercooling Pipes (platecoils)
inside DV iron plates
Cross section

TopSideBottomÆBeam direction

Thermal analysis for 4MW beams•FEM analysis for
4MW beam with 40
water-cooling platecoils SteelConcrete•Realistic condition(1/2 year 100%, 1/2year0%)x30year.
Input water =30degC
Max temperature•Plate <60degC•Concrete <120degC
ÆOK.

SoilThermal
Conductivity(kcal/m･hr･℃)

Density(kg/m3)Specific heat(kcal/kg･℃)

44.2
1.4
0.46

7860.
2300.
1890.

0.113
0.21
0.21

Mechanical Analysis
Young modulus 19600kgf/mm2,
Poisson ratio 0.3，
Linear expansion coefficient 0.00001153 １/℃
Anchor··4mRibs•~4m x 1.8m steel welded with steel ribs
(H channels) at every corner. In addition,anchors are welded every 0.45m.
No Buckling happens below 70 °C.
1.8m
Mechanical Specifications are decided.

Design for Water Circulation System-A first draft-

Utility room
At Beam Dump

Utility room
At Target Station

Heat exchange
Heat exchanger
Buffer tank(10m3x3)
Decay
VolumeDisposal
15Bq/cc
Buffer tank
Dilution tank(10m3x3)

Summary• FY2003:Design of the decay volume (Z=10-110m) with 4MW beam condition
complete.
• FY2002-2003: Iron plates with platecoils (for 71m long) purchased.
• FY2003:• Civil engineering design of Decay Region is being done.
• Details of the installation (Spec Document for installation of DV) must be
decided within FY2003. Schedule and budget is very tight.
•Construction of 3NBT line will begin in FY2004. DV beneath 3NBT tunnel,
30m (70m) long, must be completed in May, 2005.

•Tasks•Spec document for the DV installation (FY2004)•Design of Collimators+Iron plates(10m-long 20cm-thick)•Design Vacuum system+Window and Endplate•Design of water circulation system•How to protect iron plates from rusting with seawater permeating nearby

Decay Volume Schedule
2002

2003

2004 20052006

2007 2008

DesignIronplatesProduction

DV crossing 3NBT
70m(30m)
DV Remainder
40m(80m)

Installation

Installation2009Disposal Scenario of Radioactive WaterY.Oyama•After 20days operation, all radioactive water is transferred to a DP
tank in the disposal system. The cooling system for decay volumeconsiders this scheme.
•They are mixed with fresh water in the dilution tank.
•After measurement of radioactivity in the dilution tank, the water
can be disposed. It takes 1 or 2 days for the measurement.

Arrangement of Iron Plates on DV