Radiation Protection aspects of the Switch-Yard operation

V. Donate, G. Dumont, Joachim Vollaire

on behalf of DGS-RP

Outline RP measurements Operational aspects Additional monitoring Conclusions

2 EDMS 1319151PS-CSAP 10/10/2013

RP measurements

EDMS 1319151PS-CSAP 10/10/20133

Objective: Assess the maximum dose rate in the accessible part of the PS in case of beam loss in the BTM line and BHZ10 failure

Measurements

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PATP501(RAMSES monitor) installed in the area

Losses created by BE-OP (EN-STI had moved the stopper in the beam path)

Residual dose rate in the area

EDMS 1319151PS-CSAP 10/10/2013

1st losses

Scan

2nd losses2 intensities

Monitor

out of the PS

First beam loss created

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3 pulses to the stopper (1.14e13 ppp) Rescaling: 3.3e13 ppp and 3000

pulses/h Pos. 1: 340 mSv/h / 0.11 mSv per pulse Pos. 2: 155 mSv/h / 0.05 mSv per pulse Pos.3 : 700 mSv/h / 0.23 mSv per pulse

Pos. 1

Pos. 3

Pos. 2

(Pos. 3 not accessible with beam)

EDMS 1319151PS-CSAP 10/10/2013

Stopper

Pos. 1

Pos. 3

Pos. 2

Scanning for worst configuration

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Selected configuration : BHZ10 off + BTM.QNO.5 off (BTP in)

Rescaling: 3.3e13 ppp and 3000 pulses/h Pos. 1: 1.97 mSv/h / 0.7 mSv per pulse Pos. 2: 710 mSv/h / 0.23 mSv per pulse Pos.3 : 4.2 mSv/h / 1.4 mSv per pulse

(Pos. 3 not accessible with beam)

Even for this worst case, for losses limitedto a few pulses (interlock) the dose is relatively low

(to be put in perspective with residual dose rate levels)

EDMS 1319151PS-CSAP 10/10/2013

Operational considerations

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Alarm thresholds to be set according to residual dose rate when access is granted in the PS (RPO / piquet)

Short access, the dose rate decrease quickly Status of “Porte secteur inter-zone” during

technical stops and shutdown (left open ?) Loss of flexibility in access to different areas (higher

exposure…)

18/09/2012

Survey (mSv/h @ 40 cm)

06/11/201226/06/2012

EDMS 1319151PS-CSAP 10/10/2013

Missing RP monitor

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Risks associated to a loss of the Linac2(4) beam (LTB)

Possible exposure of personnel in the center of the ring or SS12 area

Measurements done with full beam loss in the LTB line leads to 800 mSv/h at the center of the ring

One single monitor would protect both areas (alarm panel at both locations)

EDMS 1319151PS-CSAP 10/10/2013

Monitor

Missing RP monitor

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PATP501 paid on R2L budget anticipating the creation of this new operational mode

RP monitoring not ready to allow Switchyard operation with PS access.

Currently missing 45 kCHF to ensure proper monitoring of accessible areas in Switchyard mode (two areas currently uncovered in case of beam losses in the LTB line) !

EDMS 1319151PS-CSAP 10/10/2013

Conclusions

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Beam losses in the BTM line leads to limited exposure of personnel in the PS ring area (interlock SIL2)

Operational procedure to be developed (to define the alarm thresholds for the PATP501 monitor) Problem of induced radioactivity…. which will decrease with

time (need to adapt the alarm threshold)…. Status of doors to be agreed upon (EN / BE / RP….) for

different periods (shutdown, TS…) RP is missing 45 kCHF to install the necessary

monitoring for the switchyard operation mode…. As part of the PS ventilation commissioning study air

flow between the PSB and PS (smoke test ?) to see if activated air could come from the PSB

EDMS 1319151PS-CSAP 10/10/2013