Radiation Protection for Mini-BooNE & NuMI 18 March, 2002

1. Radiation Protection for Mini-BooNE & NuMI 18 March, 2002 Mini-BooNE inputs from Peter Kasper & Craig Moore NuMI inputs from Nancy Grossman

2. MiniBooNE Primary Beam • Primary Beam Momentum- 8.9 GeV/c. beam from FNAL Booster. • Spill length 1.6 microseconds. • Intensity - 5x1012 ppp Rep rate 15 Hz (5 Hz Beam) 2x107 seconds/yr. ∫ Protons = 5 x 1020 p/year. –this annual flux is > than the sum of all previous Booster operation over 30 years. – main obstacles being addressed for achieving proton flux goals are Booster radiation problems both above the machine & in the tunnel.

3. Rad Monitor Readings (normalized totripsetting) AFTER Shielding Upgrade

4. Normalized Rad. Monitor Readings vs. Booster Intensity

5. Path to Meeting Booster Flux Goals for MiniBooNE • Further improvements to external Booster shielding very expensive & not considered worthwhile. • Current level of shielding makes component activation in Booster tunnel the ultimate limit. • for current operating conditions (6e15 p/hr at ~ 4.5e12 p/cycle) contact levels of > several Rem exist at hottest locations and > 0.1 Rem on RF cavities. Scaling up by x 20 for BooNE is not viable. • Remediation plans include: • new orbit control system. • collimation system to move losses to lower energy and to well shielded areas.

6. Schematic Layout of MiniBooNE Beamline

7. MiniBooNE Beamline & Targeting Radiation Safety Four Main Types of Concerns: • Ground Water Activation - Not a problem due to clay soil ~ impervious to water flow. • Air Activation - Hold air to allow short lived isotopes to decay, restrict access. • Prompt Radiation- Dirt + Radiation Monitors (to begin with). • Residual Radiation - Loss Monitors at specific potential loss points + 5 Total Loss Monitors. Remediation efforts: • increase beam transport apertures. • utilize an Electronic Berm to help remediate all four concerns. (sense 2% loss averaged over several pulses or >6% over 1 pulse.). • implement an Autotune program for reliable operation of this almost continuous beam.

8. NuMI Radiation Protection • Regions • MI/Extraction • Pre-target Region • Target Hall • Decay Tunnel • Hadron Absorber • Mitigation • Passive shielding • Interlocked radiation detectors • Beam permit system • Administrative Controls • Radiological Areas • Prompt radiation • Residual activation of enclosures and components • Airborne activation • Groundwater activation • Designs are reviewed in accordance with Chapter 8 of the Fermilab Radiological Control Manual (FRCM).

9. NuMI Radiation ProtectionOverview Schematic

10. NuMI Radiation Protection Overview • Groundwater protection drives: $$$ • Primary beamline allowable losses • Target Hall shielding (top excluded) • Decay pipe shielding • Bottom & 1 Side of Hadron Absorber shielding • Residual Activation drives : $ • Primary beamline allowable losses • Top of Target Hall shielding plus Top & Side of Hadron Absorber shielding • Air Activation drives : • Target Hall chase must be “sealed” at some level and radioactive air contained • Ventilation rate through the Target Hall above the shielding and through the Decay Tunnel must be relatively low to allow decay in transit to the vent. • Prompt Radiation: • Not much of a concern due to beamline deep underground and access limited to support rooms and MINOS cavern.

11. Prompt Radiation Labyrinth and penetration exit dose rates based on MARS source terms and standard attenuation curves.

12. Groundwater ProtectionRegulations Ø Limits for drinking water supplies and for Illinois “Class 1” groundwater resources (water that potentially could be drinking water) are the same. Ø The “point” of the regulation is to protect the resource from which the drinking water originates. Ø3H (12.3 year half-life) and 22Na (2.67 year half-life). Ø  Note surface water limits are 100 times higher for 3H and 25 times higher for 22Na. Ø  For mixtures of radionuclides, a weighted sum is used. The annual average concentrations must be below the limits.

13. Groundwater Protection: NuMI Primary Beam • Shielding not a practical choice thru most of primary transport. Require fractional operational losses along NuMI primary beam to be below 10-4 (10-6 in the lined carrier tunnel interface region, where geometry provides some shield). • Detailed simulations (MARS14) of the primary beamline and possible accident and DC (continuous) loss conditions have been studied. • Solution approach discussed in primary beam presentation. Considerable attention to primary design, installation, commissioning and operation required. • Solutions are founded well by significant prior experience. • Rigorous beam permit system provides groundwater protection. All other measures are to enable smooth high intensity operation.

14. Groundwater Protection: NuMISecondary Bean (Unlined Tunnels) • Water flows into the tunnel rapidly, thus not highly activated and is released to the surface waters. • NuMI, in discussions with FNAL and DOE Fermi, was given the charge to keep the levels of the water flowing into the tunnel (within the aquifer region) to below groundwater limits, including uncertainties and taking credit for water flow. Have monitoring wells.

15. Airborne Activation Regulations: Annual Dose < 10 mrem (all FNAL) at site boundary. Radionuclides of concern are: • 11C, 13N,41Ar (although 7Be, 3H, 15O were also calculated). • 11C, 13N are produced by spallation reactions. • 41Ar is produced by thermal neutron capture, thus hard to predict amount, assume 2.5% based on measurements at FNAL. Goal for NuMI is < 45 Ci/year (~2.5 mrem/year, or 1/4 site limit). Majority of the air activation occurs inside the Target Pile. • Closed system at negative pressure relative to the air outside the shield. • Calculations based on re-circulation and 1000 cfm ventilation, ~20 Ci/year. • Can adjust ventilation rate as needed to reach this.

16. Residual Activation • MARS14 Residuals: 30 days irradiation, 1 day cool down @2E13protons/sec

17. Prompt Radiation Levels are only a concern in the Power Supply Area (beam on occupancy) at Target Hall level. Groundwater calculations incorporate water flow, resulting in the main concern being in the lined regions of NuMI where water can not flow rapidly into the tunnel. Considerable shielding. Primary beam losses must be kept very low. Open apertures, improved optics, current/voltage limits, beam monitoring and permit system. Air Activation levels result in enclosing the Target Chase and re-circulating the air. Residual Dose rate calculations using MARS14 have been well-benchmarked with good results. Extensive modeling of the NuMI Target Hall using MARS 14. Include cracks in the models. Believe have “good” predictions for residual dose rate levels. NuMI Radiation Protection Summary