# Presentation: 483397

## 
NuMI Primary Beamline
Groundwater Protection
Radiation Safety Coordinator
Nancy Grossman
FNAL
July 13, 2001

*NuMI Primary Beamline*
*Groundwater Protection*
- Radiation Safety Coordinator
*Nancy Grossman*
*FNAL*
- July 13, 2001

## Groundwater Protection

- Hired several groundwater consultants to determine water levels and flow rates around the _unlined_ regions of the NuMI tunnel.
- All water within 10’ of tunnel flows into the tunnel
- 	(within the aquifer region)
- Most water flows in rapidly through the fractures
- Determine an average inflow velocity based on groundwater consultant’s inflow estimates
- Use the Fermilab Concentration Model, modified to allow for water flow
- Fermilab Reports TM1851, TM2092, TM2009 (NuMI).
- Updated to include our latest understanding of groundwater contamination by 22Na and 3H, the only radionuclides of concern (NuMI-B-495)
- Flow dependent residency time of water in the region of the beamline (inflow or outflow) where applicable.
- Irradiation time = residency time of the water in the activation region (not 8 years, lifetime of experiment)
- Normal operation:  time water is in the activation region
- Accident condition: 5 pulses (1.9 sec pulse)

## Groundwater Protection

- Ci is the concentration of activity due to radionuclide *i* in groundwater flowing into the NuMI tunnel (in picoCuries per milliliter), and
- The factor (1/0.037) is the conversion factor used to convert disintegrations per second (dps) to picoCuries, and the term in brackets is the buildup/removal factor, accounting for radionuclide buildup, decay and removal due to inflow.

## Groundwater Protection

- _Parameters Defined:_
*N**p*	is the number of incident protons per second at the source (protons/sec).
*S**avg*	is the average star density per incident proton in a region of unprotected rock close to the source of production (stars/cm3/proton).
*K**i**L**i*is the atoms per star for isotope *i* that is in the water (atoms/star).
- n	is the porosity of the rock formation; that is the ratio of the volume of void in the rock (generally filled with water) to the volume of rock (unitless).
*t**ir*	is the irradiation time (average residency time in activation volume for flowing water).
- i 	is the inverse mean lifetime of radionuclide *i*, measured in units consistent with those of time *t**ir**.*
*r**	*is the radial distance from the tunnel wall that defines the volume over which the star density is averaged to determine* *Savg (99.9% volume, r is about 1-2 meters).
*v*i 	is the flow velocity for radionuclide *i *in water*.*

## Groundwater Protection

- Calculations must be below the regulatory limit including uncertainties (FNAL memo, DOE Environmental Assessment response letter)
- Use uncertainties in _all_ parameters to determine overall uncertainty** **
**Determine effect on results and add in quadrature**
- Calculations are conservative:
- Comparing concentrations in inflow water, which will be pumped to the surface, to groundwater limits
- In “dry” regions, grout less to allow more inflow
- Model includes worst case conditions, most likely will not encounter (haven’t yet!)
**Update flow model to incorporate inflow measurements and geotechnical data obtained during construction**
- Does not include decay during migration to a well
**Water along the unlined beamline tunnel can not get to any well other than the NuMI beamline “well”**
- Does not include dilution & dispersion in transit to a well
- Use Beam Loss Budget System to estimate beam loss (beam loss monitors)
**Bottom Line:**
- _Ensure compliance with monitoring well(s)_

## Groundwater Protection: Primary Beam

- Lined tunnel in glacial till
- Lined tunnel in mixed glacial till/rock (dolomite interface)
- Unlined tunnel in dolomite
- Each case must be treated differently for groundwater contamination concerns.
- Lined tunnel in glacial till (MI extraction region and first ~125’ section of carrier tunnel):
- Standard Fermilab Concentration model
- Activation occurs in soil and water (assume for lifetime of facility)
- Migrates (slowly, ~0.55 cm/year vertical seepage velocity) to the class one groundwater
- Migration taken into account with Rtill (1e-5), decay/dispersion factor in transit to aquifer
- Use an average distance of 10 feet to the aquifer (ranges from 0 to 20 feet)
- Slow migration to aquifer means not such a problem region.

- Groundwater Protection: Primary Beam

## Groundwater Protection: Primary Beam

- Lined carrier tunnel in mixed glacial till/rock
- 	(next ~140’ section of carrier tunnel):
- The flow of water in this region can vary from 4 ft/year to 50 feet/year
-  Depending on the mix of soil and rock.
- The exact location, extent and soil/rock makeup of this section of the carrier tunnel will not be known until the digging starts.
- Standard Fermilab Concentration model with a conservative residency time based on a flow away from the tunnel at 20’/year.
- Velocities estimated by P. Kesich.
- Velocity direction is horizontal and away from the tunnel (P. Kesich)
- _Conservatively_ assume the water flows out of the activation region at 20’/year and then is immediately in the class one groundwater.
- Problem region due to medium migration time (fortunately large aperture):
- Allows long enough residency time to allow contamination
- Due to the variable nature of the region, we can not assume any decay/dilution time in transit to the aquifer.

## Groundwater Protection: Primary Beam

- Unlined tunnel (last 135’ section of carrier tunnel and pretarget hall):
- Water flows in at a rate of 800 feet/year (~2 feet/day)
- Use the “Standard” NuMI Inflow model
- Lower section of carrier tunnel: beam loss rates not as much of a concern here due to high inflow rates and large aperture
- Pretarget: beam loss rates are a concern due to smaller device apertures
- 	(low level DC losses)
- Results:
- Based on average star densities over the 99.9% activation volume
- 	(volume out radially to where star density falls to 0.1% of maximum)

## Groundwater Protection: Primary Beam

- _Preliminary_ MARS14 Primary beamline results, _operational beam losses_:
- For shaded yellow, note: Limit of 1E-6 for a direct primary beam hit in carrier tunnel, this is prevented except for fault modes such as a vacuum pipe collapse or magnet coil failure.

## Groundwater Protection: Primary Beam

- Open apertures and “Autotune”  will help keep beam  nominal and “clean”
- Enable beam extraction to NuMI only when conditions are nominal (Beam Extraction Permit)
- Magnet currents within nominal limits this pulse
- Limit on beam loss last pulse and integrated beam loss (beam loss monitors, Beam Loss Budget System)
- Interlocked radiation detectors
- “Clean” Main Injector beam
- Detailed simulations (MARS14) of the primary beamline and possible accident and DC (continuous) loss conditions have been studied.
- Magnet power supply regulation levels needed to keep losses minimal are obtainable.
- Strong indication that beam loss monitors (BLM) signals closely track groundwater activation levels.
- Plan to test as much of the Extraction Beam Permit System and Beam Loss Budget System as possible in the P150 line starting this year.

## Groundwater Protection: Primary Beam

- _Preliminary_ MARS14 Primary beamline results, _normal operation_:
- Determine worst loss locations for normal operation
- Leads to power supply regulation (and Main Injector beam) requirements
- With presently envisioned power supply regulation:
**All normal (DC) losses in the primary beam region are **_**at least an order of magnitude below**_** what is necessary to meet the groundwater regulations. **
- Main Injector emittance tails and position stability:
_**No beam loss if less than 3 mm horizontal orbit**_** shift (vertical requirements are very loose)**
**Modeled range of emittance and tails:**
- No beam loss if __ 40 emittance with tails
- Expect ~ 20 emittance with tails to 40
- Beam loss monitors look to be very good for tracking groundwater activation.
**Use Beam Loss Budget System to keep track of losses.**

## Groundwater Protection: Primary Beam

- _Preliminary_ MARS14 Primary beamline results, _accident losses_: