# Presentation: 065301

## Radiation shielding studies             for  MTA

- Igor Rakhno
*October 30, 2008*

## Starting approximately in spring 2007, the following shielding issues were studied: 

- Accident on a quad ~17 m upstream of the concrete block
- Accidents around the 12-ft concrete block (and re-routing)
- Accident on the 2nd beam stop upstream the MTA wall
- Vertical penetration (vent) at the upstream corner of MTA hall
- (re-routing)
- Shielding block in the access pit
- Thickness of the shielding above the MTA roof
- Horizontal cryo penetrations in the MTA hall
***There was a lot of minor requests from radiation safety group (Mike Gerardi et al.)****** ***

## Plan view of the Linac – MTA area

## Plan view – MTA

## Accidents around the 12-ft concrete block              (and re-routing)

## Plan view @ beam line elevation

## Calculated dose in the penetrations @ X=370 cm 

-                         **Location**                           **Dose (mrem/pulse)**
- Beam pipe 5 m   US the 12-ft sh.block                             1
- Beam pipe 2.5m US the 12-ft sh.block                             1
- Beam stop itself                                                                 1
- Beam pipe inside the 12-ft sh.block                                25
- Quad 5 m DS the 12-ft sh.block                                    240
-        **Quad 1'   DS the 12-ft sh.block                                   500**

## Re-routing and re-stacking (Pushka’s model) 

## The expected dose rate above the 12-ft shielding block due to the accident is estimated to be less than 1 mrem/pulse.1 pulse = 1.6×1013 protons

- FRCM (*Accident*)
- Maximum dose equivalent                                      Controls
- expected in 1 hour
- _________________________________________________________
- D < 1 mrem                                                              No precautions
- 1 < D < 5 mrem                                                       Signs ‘Controlled Area’.
-                                                                                    No occupancy limits.

## Accident on the 2nd beam stop upstream the MTA wall       (with MTA RF trench extension)

## Geometry model – cross section 

## Geometry model – cross section 

## Plan view (red dots – hypothetical beam loss locations)

## Star density distribution – plan view

## Dose equivalent – cross section

## The expected dose rate above the shielding is estimated to be less than 1 mrem/pulse.1 pulse = 1.6×1013 protons

- FRCM (*Accident*)
- Maximum dose equivalent                                      Controls
- expected in **1 hour**
- _________________________________________________________
- D < 1 mrem                                                              No precautions
- 1 < D < 5 mrem                                                       Signs ‘Controlled Area’.
-                                                                                    No occupancy limits.

## Vertical vent in MTA hall, 20" (elevation view)

## Target – 1-cm copper (10% of interaction length) – re-routing?

## Accident on the 2nd beam stop

## Shielding block in the access pit (cross section)

## Thickness of the shielding above the MTA roof              (recent request from Alan Bross, 1-cm Cu target @ 15 Hz)

## Horizontal cryo penetrations in the MTA hall

## Realistic model

## Realistic model

## Calculated dose attenuation curve for the 12" penetration(dose averaged in vacuum cells) 

- The existing Linac safety envelope is 3.5×1017 p/hr which means rep. rate approximately 6.1 Hz at 1.6×1013 ppp.
- D0 = 2.2×106 mrem/hr for 10% of I.L. @ 1 Hz.
- D0 * 10-8 * 10 * 6.1 = **1.3 mrem/hr **= **6.1×10****-5** **mrem/pulse**.