Air activation inside and around the SPS beam dump M. Baudin H. 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

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: m 3.h -1 in the hall outside dump shielding; – Vented dump: 0.1 m 3.h -1 in the dump shielding, m 3.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

Activation is dominated by 14 C  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

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

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 m 3.h -1 venting. Conclusions: normal operation over long term

Conclusions: intense operation over 1 day Closed coreVented 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

2 air volumes considered between dump and shielding with a factor of ~2.5 Small: 2.71 m 3 inside: – Closed core: 3.98E-2 µSv.year -1 – Vented core: µSv.year -1 Large: 7.43 m 3 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.