Air activation inside and around the SPS beam dump

M. BaudinH. Vincke

DGS-RP-AS

Content

• Irradiation and ventilation parameters

• Dose given to personnel entering ECX5 due to airborne radioactivity

– Air activation with a closed dump

– Air activation with a vented dump

• Conclusions and dose given to the environment

Irradiation and ventilation parameters

Irradiation and ventilation parameters

• 3 scenarios used for calculations– 10 years of operation, with 2E18 protons.s-1 per year spread equally

over 365 days (6.4E10 p.s-1)

– 1 day with 5E12 p.s-1 (most pessimistic case)

– 1 h with 1.5E12 p.s-1 (realistic pessimistic case)

• Venting rates:– Closed dump: 20000 m3.h-1 in the hall outside dump shielding;

– Vented dump: 0.1 m3.h-1 in the dump shielding, 20000 m3.h-1 outside.

• All results presented in these slides only account for the dose induced by activated air and not by the residual material activation.

With a closed dump

Air activation with a closed dump

Air activation with a closed dump

Activation is dominated by 14C activation triggered dose rate will not decay within thousands of years

Air activation with a closed dump

With a vented dump

Air activation with a vented dump

Due to the ventilation of the dump the activation will vanish completely within a few days

inhaling

Air activation with a vented dump

Air activation with a vented dump

Due to the ventilation of the dump the activation will vanish completely within a week (time can be reduced by increasing ventilation speed)

Air activation with a vented dump

Air activation with a vented dump

Conclusions: normal operation over long term

Closed core Vented core

• Considering the normal operations over 10 years, 6.4E10 p.s-1, the vented core appears to be mandatory:– Almost identical dose rates outside of shielding– Dose rates more than 100 times lower inside

shielding with 0.1 m3.h-1 venting.

Conclusions: normal operation over long term

Conclusions: intense operation over 1 day

Closed core Vented core

• An extreme scenario that shows air activation can be an issue even with ventilation

• Increased venting rate or longer cooling times might be considered in such a case

• However, the stress conditions (1.5E12 s-1 over 1 hour) used in the thermal studies of the dump give satisfactory results for air activation

• General comment: In order to reduce airborne radioactivity production air volume inside dump should be as low as possible.

Conclusions: intense operation over 1 day

Doses given to the environment

Doses given to the environment

2 air volumes considered between dump and shielding with a factor of ~2.5

• Small: 2.71 m3 inside:– Closed core: 3.98E-2 µSv.year-1

– Vented core: 0.557 µSv.year-1

• Large: 7.43 m3 inside:– Closed core: 4.12E-2 µSv.year-1

– Vented core: 1.20 µSv.year-1

Doses released to the environment are acceptable, but the inside air volume should be kept to a minimum.