Rad safety and activation L. Zanini Group Leader Neutronics ESS Bunker CDR 16 October 2018

Scope Calculations done by E. Klinkby and L. Zanini. MCNP+CINDER’90 The scope of the activation calculation is to determine the contribution of roof and wall to the dose rate in the bunker. The total dose rate in the bunker has contribution from beamline components, as well as from bunker floor and monolith structures. An assessment of the overall dose rate from all the contributions should be done separately. Dose rates from components inside the bunker were previously calculated [ESS-0087597]. The following new information has been calculated. Dose rate levels inside the bunker from roof and wall for possible access inside the bunker. Dose rate on the bunker floor from active roof blocks when the roof is opened for access.

Calculation of activation of wall and roof must consider the following aspects Both short and long sectors must be considered. Activation over long term irradiations is of interest. It is not realistic to consider a long-term irradiation of the wall without anything in the bunker. The presence of beamlines must be taken into account CSPEC: geometry with curved guide TBL: geometry with straight guide Calculations have been performed with and without a boron absorbing layer inside the vacuum pipe. A layer of 5 mm of mirrobor (a neutron shield material by Mirrotron containing 80% B4C) was used as example. Additional use of boron layers (in walls and roof) has not yet been investigated

Reference configuration choice (1) Neutron maps on short and long sector walls (no guide, no reflection card in MCNP) CSPEC TBL

Reference configuration choice (2) Neutron maps (all energies) on long sector walls without and with guide No guide Straight guide n/cm2/s Peak value 5 108 n/cm2/s

Dose rate from wall activation, without and with guide mSv/h No beamline Straight guide ~50 mSv/h at 1 m ~5 mSv/h at 1 m

Roof activation long sector from CSPEC beamline Gamma dose rate (10 years irradiation, 1 day cooling) Only activation of roof and wall has been calculated. Dose rate levels are at the level of 10s of mSv/h, which is acceptable as in most cases work is done remotely 1 day cooling

Roof activation long sector from CSPEC beamline Gamma dose rate (10 years irradiation, 3 day cooling) Only activation of roof and wall has been calculated. Dose rate levels are at the level of 10s of mSv/h, which is acceptable as in most cases work is done remotely 3 days cooling

Dose rate from extracted of roof block laying on bunker roof - 1 day cooling

Wall long sector: Comparison with and without mirrobor inside vacuum pipe (note different scale) 5 mm mirrobor in vacuum pipe, 3 days cooling With mirrobor

Wall short sector Test Beam Line, with mirrobor inside vacuum pipe. Dose rate after 3 days cooling.

Conclusions Dose rates from the roof are at the level of 10 mSv/h after 1 and 3 days decay. Dose rate from a roof block removed and placed on the bunker floor are at the level of 1 mSv/h or less at 1 m from the block, 1 day after shutdown Dose rates from a realistic irradiation condition of the wall, i.e., with a beamline in place, going through the bunker, are comparable to the dose rates for the roof, for the short sector wall, and lower for the long sector wall. Results are in ESS-0416081 Calculations should be repeated with added impurities from heavy concrete samples.

Addendum Dose rate at roof after removal of NBPI (K. Batkov ESS-0061869). Calculated 15 mSv/h on top of roof after 14 days cooling . 15 mSv/h