Radiation Protection aspects

for SHIPDoris Forkel-Wirth, Stefan Roesler,

Helmut Vincke, Heinz Vincke

CERN Radiation Protection Group

1st SHIP workshop, 10-12 June 2014

Universität Zürich

2

Content

• General info

• Radiation issues at the SPS extraction area and in TDC2

• Required shielding around SHIP target

• Residual dose rate of the SHIP target

• Dose rate in detector hall (only passive shielding)

• Activation of muon shielding

3

General info • Similar number of protons on target than CNGS

(but SHIP facility is close to surface) o 4×1019 pot/year

o in total (in 5 years) ~2×1020 pot

• RP design is done for 7×1013 protons (400 GeV) per pulse (every 8.4 s) i.e. 530kW !

• Main Radiation Protection issues of SHIP, o Beam losses in the SPS accelerator and extraction area towards SHIP

o High prompt dose around SHIP target sufficient shielding is needed

o High residual dose rate after beam stop only remote handling possible in target area

o Air activation reduce air volume to a minimum, use He (or vacuum) in target area

o Target station is located close to surface environmental impact due to possible activation of soil and ground water.

4

RP aspects for the SPS machine

• Beam losses will cause:1. Air activation2. Residual dose rate increase3. Dose to equipment (magnets, cables, etc..)

• “Estimated beam losses from high intensity beam (7×1013 protons per extraction) are about a factor 7 higher than for CNGS beams“ .(Quotation from collimator LIU review minutes)

• Already at nominal beam intensity the dose levels will be a factor 3-6 higher than in previous years. Without mitigation, this could lead to dose levels of 12 mSv/hr after a month of cool-down.

• Ways to reduce beam losses have to be investgated.

5

Beam extraction area TT20

……. high dose rate levels at work places will be present to personnel during installation/modification of beam line elements.

Courtesy: B. Goddard

H*(10) at first splitter region … about 10 months after beam stop. Dose rate at 40cm of the element (unit : µSv/h)

Dose rate on contact of the element (unit : µSv/h)

6

Beam extraction area TT20

A careful planning of these activities combined with an optimized work and dose planning will be essential.

Work needs approval from CERNs ALARA committee.

The concrete wall of TDC2 tunnel and the soil close to TDC2 tunnel are activated.

The CE workers need to be classified as Radiation Worker, have to receive all required safety trainings and need to be individually monitored.

In order to quantify the amount of activation as well as the lateral distribution (volume) of activated soil it is advised to take soil samples close to the TDC2 area.

Removal of existing beam line components has to be foreseen before civil engineering work in TDC2 can start.

A waiting time has to be respected before beam line equipment can be removed.

SHIP provides an opportunity to improve the present situation at high beam loss points.

Benefits of radiation decay in TDC2

PMI 25

Date Dose rate at PMI 25 [mSv/h]

03/12/2012 BS + 2h 2.98

04/12/2012 BS + 24h 0.63

04/12/2012 BS + 30h 0.56

18/12/2012 BS + 15 days

0.11

18/04/2013 BS + 136 days

0.06

21/07/2013 BS + 230 days

0.046

30/09/2013 BS + 301 days

0.041

In red marked zone: ~1mSv/h (at 40cm distance) after 10 months of cool down time.

8

o FLUKA MC code has been used to estimate the shielding requirments

o No gaps or feedthroughs (for services like cooling) in the shielding; will decrease the efficiency of the target shielding.

Shielding around SHIP target

Mu

on

sh

ield

An absorber downstream of the last primary beam tunnel element might be needed to shield the beam line elements and to reduce their activation.

Uni

ts in

m

Side view Front view

9

Residual dose rate around the SHIP target

Residual dose rate (in uSv/h) at the SHIP target after one operational year and different cooling times as a function of radial distance from the target center

Residual dose rate (in uSv/h) around the SHIP target after one operational year at ultimate intensity and 1 month of cooling time.

Target exchange will be a very delicate and demanding

intervention…… and further studies and optimisation of such an intervention are necessary.

Remote handling only!

10

Radiation level in detector hall

Detector hall will be classified as a Radiation Area (during beam operation)

~ 1

0 u

Sv/

h

~ 4 - 5 uSv/h

concrete

leadtungsten

dete

ctor

hall

SHIP target

moraine

~ 1 uSv/h

11

Activation of tungsten muon shield

Isotope production in tungsten shield

Ambient dose equivalent in the tungsten shielding as a function of cooling time (after 180 days of operation, averaged (0<r<20cm)

Muon shield will become slightly activated especially the

upstream part

12

Summary & conclusion• The performance of the ZS septa magnet and the induced radioactivity in the SPS

extraction region requires further studies. Ways to reduce beam losses have to be investgated.

• Work in TDC2 requires a detailed work and dose planning. It will be an ALARA level 3 intervention which requires prior approval from the ALARA committee.

• Concrete in TDC2 and soil close to TDC2/TCC2 tunnel are activated. Soil samples close to extraction area would be needed to quantify the activation level of the soil.

• Target shielding design – massive iron/concrete shielding needed.

• Detector hall will be classified as a Radiation Area

• Muon shielding will become slightly activated.

• Some other RP studies (like production of radioactive waste, waste disposal, dismantling of the facility, etc. ) and environmental issues (releases of radioactivity via air or water pathways, activation of soil, etc.) are not studied yet. This will however be needed at a later stage of the project.

Spare slides

CERN’s Area Classification