Linac and Booster Radiation Shielding Status, Plans and Constraints

Linac and Booster Radiation Shielding Status, Plans and Constraints

Linac and Booster Radiation Shielding Status, Plans and Constraints

John E. Anderson Jr.John E. Anderson Jr.

Proton Source Meeting

December 7, 2010

Outline

• Shielding Assessment Beam Intensity Limits• MCR Operational Intensity Limits• Linac SA Intensity Limits• Booster SA Intensity Limits• Booster Reassessment Efforts• Booster Operational Issues

Proton Source Meeting December 7, 2010 2

Shielding Assessment Intensity Limits

• Operating Intensity Limits– Beam intensity limit based on the FRCM

• Accelerator Safety Envelope (ASE) Intensity Limits– DOE approved beam intensity limit– May or may not be equal to the Operating Intensity

Limit (Currently is for Linac and Booster)– Based on a 10 mrem accident to a member of the

public or an untrained worker– Exceeding limit reported to

Head Office of Science


Shielding Assessment Intensity Limits

• Both Operating and ASE Intensity Limits are defined in Appendix A of the laboratory Safety Assessment Document

• Limits are approved by– Fermilab Director– DOE Fermi Site Office Manager


Main Control Room Operational Limits

• Beam Permit– Based on ASE– Approved by Division Head

• Operational Limit– Some % less than Beam Permit– Generally 5-10% less

• Warning Limit– Some % less than Operational Limit– Generally 5-10% less


1993 Linac Shielding Assessment

• Operating and ASE Intensity Limits– 3.54 E17 protons / hour

– MCR Operational Limit• 3.34 E17 protons / hour ~-5%

– MCR Warning Limit• 3.185 E17 protons / hour ~-5%

– Current limits exceed future programmatic needs

– No plans to do anything further

– Continue to monitor Linac tech area offices


1998 Booster Shielding Assessment

• Operating and ASE Intensity Limits– 1.8 E17 protons / hour

– MCR Operational Limit• 1.22 E17 protons / hour ~-30%

– MCR Warning Limit• 1.09 E17 protons / hour ~-10%

– Can raise the MCR warning limit to~1.5 E17 protons / hour



• “Nowhere around the Booster ring is there sufficient shielding to prevent FRCM limits from being exceeded under DC accident conditions at the intensities required to meet current programmatic goals (1.35E17 protons / hour).”

• References 1991 Booster Assessment beam loss measurements at penetrations to determine current Operational Limits of1.8 E17 protons / hour



• Assessment shows losses limited to long and short strait locations

• Assessment based on studies to determine shower max locations

• 51 interlocked detectors placed approximately at shower max locations



• Issues– Machine modifications may change loss locations thus

invalidating the assessment• Correction element upgrades• Machine realignment• Collimators at L6 and L7• Others?

– With machine modifications since 1998, is the current assessment still valid?

– Limited information available about penetration dose rates and studies.


Booster Shielding Assessment Efforts

• Current reassessment efforts– Assessing for 2.0 E17 protons / hour

• Roger Dixon Guidance

– Converting Booster to Incremental Shielding Assessment Methodology

• Being done to identify all penetrations, problem areas, and allow for intensity scaling

– Expect assessment to be complete in January 2011• Will need to find mitigations for problem areas


Booster Shielding Assessment Efforts

– Labyrinth and penetration spreadsheets created• 7 labyrinths and 190 penetrations• 182 penetrations fail at 2E17 protons / hour• MARS models of penetrations filled with poly also fail

– Can a point loss be created under a penetration?• Need technical justification if used

– Can ropes and signs be used to barrier front of penetrations?

• Limits access to equipment– Can sand be used to fill penetrations vs. poly?

• Penetrations pass • Passive control


Booster Tower West Operational Issues

• Booster L6 area collimators

• Routinely measure rates in the Booster Tower West Stairwell and upstairs offices BTW-201 & 202

• Need to identify source and better shield the area


Booster Tower West Operational Issues


Linac and Booster Radiation Shielding Status, Plans and Constraints

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