**LANSCE Isotope Production Facility---**

**Shield Wall Evaluation**

**Kenneth A. Van Riper**

**White Rock Science Report 99--11**

**November 30, 1999**

![](media/image1.png){width="5.833333333333333in"
height="4.888194444444444in"}

Tracks of neutrons and photons resulting from a beam spill in the
existing LANSCE beam tunnel. The IPF construction area is at the top
right.

# Summary

We have carried out Monte Carlo radiation transport calculations for the
LANSCE IPF to investigate the shielding provided by various concrete
structures and the tuff outside of those structures. The thickness of
tuff outside the main tunnel is sufficient to limit the dose equivalent
rate (DER) to less than 1 mrem/hour for a 10 amp beam spill in the main
tunnel and to much less than 25 rem/hour for a 1500 amp spill. The base
of the shield wall, at tunnel level, also provides adequate protection.
There are regions near the cut out for the existing electrical duct
where the DER in the shield surface could be as high as 10 mrem/hour.
Enhancement of the shielding by the concrete in the duct and additional
poured concrete could ameliorate concerns in this area. An operational
phase model in which a 500 amp beam is directed at a 20" long RSS beam
plug results in a DER in the upstream end of the IPF tunnel of 35
mrem/hour.

# Introduction

The Isotope Production Facility (IPF) project will build a new beam line
on the north side of the existing LANSCE accelerator building at Los
Alamos National Laboratory. One part of this construction, to be carried
out during a scheduled beam outage, will involve building a shield wall
between the existing accelerator tunnel and the new beam tunnel. This
wall will serve two purposes. The first will be to provide radiation
shielding to protect construction workers involved in building the new
facility, which will require construction activities while the
accelerator is operating. The second will be to allow for personnel
access into the new tunnel at times when the accelerator is providing
beam for delivery to other experimental areas.

We have made radiation transport calculations to evaluate the
effectiveness of the proposed shield wall during both the construction
and operation phases. For the construction phase, we consider beam
spills at three locations in the mean beam line and examine the
attenuation of the Dose Equivalent Rate (DER) in the concrete walls and
tuff surrounding the beam tunnel as well as in the shielding wall. For
the operation phase, we assume a 500-microampere beam spill on the last
RSS beam plug, immediately in front of the beam line hole in the shield
wall.

# Calculation Models

## MCNPX Code

All calculations were made with the Monte Carlo transport code MCNPX
from LANL group XTM. We used the latest version, MCNPX2.1.5, which was
released on May 21, 1999. MCNPX transports protons, neutrons, photons,
and other particles simultaneously. A number of evaluated data files
provide accurate neutron cross sections for neutron energies up to 150
MeV. The calculations were run on a Silicon Graphics Inc. INDY
workstation running IRIX 6.5.

The MCNPX distribution comes with approximately 30 test problems
designed to verify proper installation and operation of the code. Our
installation exactly duplicated the results of all the test problems. As
a further check, we used MCNPX2.1.5 on a model we had previously
calculated in the IPF design phase. That model calculates the transport
of radiation from a beam spill in the IPF target room up a vertical
access shaft and through a 2 foot plug at the top of the shaft.

The previous calculation used LAHET2.83 and MCNP4B. LAHET calculated the
transport of protons, high-energy ( 20 MeV) neutrons, and a number of
nuclear particles. A log of events was written to a history file that
was processed to obtain tallies for the high-energy neutron contribution
to the DER and a low energy neutron and photon source for MCNP.
Transport of those particles by MCNP yielded the remainder of the
neutron DER and the photon DER.

For both neutrons and photons in the MCNPX2.1.5 results, F4 volume
tallies in the air spaces surrounding the spill are 2% larger than in
the previous run.  Elsewhere, tallies were from 0% to 7% larger than in
the previous run.  There is a suggestion of more attenuation through the
concrete, by a few %, in the MCNPX run, but the statistics rule out a
definite statement (we used 1/2 the number of histories in the MCNPX run
as in the LAHET--MCNP model).

As a final check, we wrote a surface source file with MCNPX at selected
surfaces in a model of a 110 MeV beam spill (described below), and then
used that file as a source in both MCNPX2.1.5 and MCNP4B to look at
neutron and photon penetration into concrete and tuff. The results
agreed within their statistical uncertainties.

The small differences we saw between MCNPX2.1.5 and MCNP4B are not
unexpected because of the more accurate neutron cross sections and
improved charged particle (proton) transport in the former. We consider
MCNPX2.1.5 to be performing properly and an appropriate code to use for
the IPF shielding studies.

We used MCNPX to transport protons, neutrons, and photons. In runs that
read a surface source file, protons were omitted. A test run with pion
transport enabled produced the same results as a run without pions. We
neglected pions for the models reported here.

## Materials

The major materials are tuff (Pajarito Plateau soil), ordinary concrete
(4000 psi mix), and air. The beam line is made of SS--304 stainless
steel and contains a vacuum at 1.510^-12^ atom b^-1^ cm^-1^. The beam
obstruction for the 110 MeV spill and the RSS beam plug are made of
copper of natural isotopic composition.

The concrete and tuff compositions are based on those given in LANL
memorandum ESH--12:99--100 from Russ Durrer to Richard Heaton. This
document specifies the elemental composition, not the isotopic
composition. For most elements, there is only a single naturally
occurring isotope or an MCNPX cross section table is available for the
natural isotopic composition of the element. We divided the given
fractions for Hydrogen and Oxygen into ^1^H, ^2^H, ^16^O, and ^17^O
based on the natural abundance of these isotopes. We increased the ^16^O
fraction by 0..000080286 and 0.0000105203 for tuff and concrete,
respectively, to cause the fractions of all isotopes to sum to unity.

Table 1 through Table 5 list the compositions of the materials. Table 6
gives their densities.

  ---------------- ----------- ----------------------- -------------------
  Element          A           Weight Fraction         MCNPX ZAID

  Hydrogen         1           0.0066489               1001

  Hydrogen         2           1.01410^-6^            1002

  Oxygen           16          0.5178777860            8016

  Oxygen           17          0.0002023               8017

  Sodium           23          0.0280                  11023

  Aluminum         27          0.0594                  13027

  Silicon          nat         0.344                   14000

  Potassium        nat         0.0337                  19000

  Iron             54          0.01017                 26054
  ---------------- ----------- ----------------------- -------------------

Table 1---Tuff composition by weight fraction.

  ---------------- --------- ------------------------- --------------------
  Element          A         Weight Fraction           MCNPX ZAID

  Hydrogen         1         0.0035794415              1001

  Hydrogen         2         0.0000005584              1002

  Oxygen           16        0.4947570990              8016

  Oxygen           17        0.0001934211              8017

  Sodium           23        0.00938                   11023

  Magnesium        nat       0.00561                   12000

  Aluminum         27        0.03356                   13027

  Silicon          nat       0.33525                   14000

  Phosphorus       31        0.00028                   15031

  Sulfur           nat       0.00175                   16000

  Potassium        nat       0.01154                   19000

  Calcium          nat       0.08607                   20000

  Titanium         nat       0.0014                    22000

  Manganese        55        0.00021                   25055

  Iron             nat       0.01641948                26000
  ---------------- --------- ------------------------- --------------------

Table 2---Concrete composition by weight fraction.

  ----------- ------ ------------------ ------------------- ---------------
  Element     A      Fraction for Air   Fraction for Vacuum MCNPX ZAID

  Hydrogen    1      1.7596710-10      1.2033410-7        1001

  Hydrogen    2      2.6399210-14      3.6077910-11       1002

  Helium      3      1.5054510-16      6.2981910-13       2003

  Helium      4      1.0753210-10      5.9702810-7        2004

  Carbon      12     5.9874410-9       1.7342110-1        6012

  Carbon      13     6.6594710-11      2.0901410-3        6013

  Nitrogen    14     3.1937410-5       6.2034610-1        7014

  Nitrogen    15     1.1860710-7       2.4678410-3        7015

  Oxygen      16     8.6119110-6       1.9104710-1        8016

  Sulfur      32     1.3430110-13                          16032

  Argon       nat    1.9172410-7       1.0623810-2        18000

  Krypton     78     8.1851710-14      8.8468810-9        36078

  Krypton     80     5.2618910-13      5.8329610-8        36080

  Krypton     82     2.7127910-12      3.0823610-7        36082

  Krypton     83     2.6894110-12      3.0931310-7        36083

  Krypton     84     1.3330210-11      1.5515610-6        36084

  Krypton     86     4.0458110-12      4.8213010-7        36086

  Xenon       nat    1.7939910-12      3.2671910-7        54000
  ----------- ------ ------------------ ------------------- ---------------

Table 3---Air and Vacuum composition by number fraction.

  ------------- --- ----------- ---------- -------------------- ------- ------------------------
  Element       A               Weight                          MCNPX   
                                Fraction                        ZAID    

  Copper            nat                    1.0                          29000
  ------------- --- ----------- ---------- -------------------- ------- ------------------------

Table 4---Copper composition

  ---------------- ----------- ---------------------- --------------------
  Element          A           Number Fraction        MCNPX ZAID

  Carbon           12          3.1512910-4           6012

  Carbon           13          3.5050010-6           6013

  Silicon          nat         1.7033410-3           14000

  Phosphorus       31          6.9502710-5           15031

  Sulfur           32          4.4759110-5           16032

  Chromium         nat         1.7481010-2           24000

  Manganese        55          1.7415710-3           25055

  Iron             nat         5.8118410-2           26000

  Nickel           nat         8.1514510-3           28000
  ---------------- ----------- ---------------------- --------------------

Table 5---Stainless Steel composition by number fraction.

  ---------------------- ------------------------ ------------------------
  Material               Mass Density             Number Density

                         g cm-3                   atom b-1 cm-1

  Concrete               2.34                     

  Tuff                   1.69                     

  Stainless Steel        (7.944)                  8.7628710-2

  Air                    (9.87240010-4)          4.0866010-5

  Vacuum                                          1.510-12

  Copper                 8.89                     
  ---------------------- ------------------------ ------------------------

Table 6---Material densities (values in parentheses were not used in
model).

## Dose Response Functions

MCNPX surface (F2) and volume (F4) tallies are stored internally in
units of particles cm^-2^. Dose response functions convert from these
units to a DER in rem/hour.

For neutrons (Table 7), we used values from NCRP--38[^1], also known as
ANSI/ANS-6.1.1-1977 (kindly supplied by Jeffrey Bull). The photon
response function (Table 8) is also from ANSI/ANS-6.1.1-1997 (also
supplied by Bull).

  ----------- ----------- ----------- ----------- ----------- --------------
  Energy      (rem        Energy      (rem        Energy      (rem hr^-1^) /
  (MeV)       hr^-1^) /   (MeV)       hr^-1^) /   (MeV)       (n cm^-2^
              (n cm^-2^               (n cm^-2^               s^-1^)
              s^-1^)                  s^-1^)                  

  2.510-8    3.6710-6   0.5         9.2610-5   20.0        2.2710-4

  10-7        3.6710-6   1.0         1.3210-4   40\.        2.49710-4

  10-6        4.4610-6   2.5         1.2510-4   60\.        2.2710-4

  10-5        4.5410-6   5.0         1.5610-4   100\.       1.7835810-4

  10-4        4.1810-6   7.0         1.4710-4   200\.       1.92110-4

  10-3        3.7610-6   10.0        1.4710-4   300\.       2.2710-4

  10-2        3.5610-6   14.0        2.0810-4   400\.       2.49710-4

  10-1        2.1710-5                                       
  ----------- ----------- ----------- ----------- ----------- --------------

Table 7---Neutron dose response function

  -------- ----------- -------- ----------- -------- ----------- -------- -----------
  Energy   (rem        Energy   (rem        Energy   (rem        Energy   (rem
  (MeV)    hr^-1^) /   (MeV)    hr^-1^) /   (MeV)    hr^-1^) /   (MeV)    hr^-1^) /
           ( cm^-2^            ( cm^-2^            ( cm^-2^            ( cm^-2^
           s^-1^)               s^-1^)               s^-1^)               s^-1^)

  0.01     3.9610-6   0.4      9.8510-7   1.8      2.9910-6   5.35     6.0110-6

  0.03     5.8210-7   0.45     1.0810-6   2.2      3.4210-6   5.75     6.3710-6

  0.05     2.9010-7   0.5      1.1710-6   2.6      3.8210-6   6.25     6.7410-6

  0.07     2.5810-7   0.55     1.2710-6   2.8      4.0110-6   6.75     7.1110-6

  0.1      2.8310-7   0.6      1.3610-6   3.25     4.4110-6   7.5      7.6610-6

  0.15     3.7910-7   0.65     1.4410-6   3.75     4.8310-6   9        8.7710-6

  0.2      5.0110-7   0.7      1.5210-6   4.25     5.2310-6   11       1.0310-5

  0.25     6.3110-7   0.8      1.6810-6   4.75     5.6010-6   13       1.1810-5

  0.3      7.5910-7   1        1.9810-6   5.0      5.8010-6   15       1.3310-5

  0.35     8.7810-7   1.4      2.5110-6                                 
  -------- ----------- -------- ----------- -------- ----------- -------- -----------

Table 8---Photon dose response function

## Variance Reduction

Deep penetration models are a difficult problem for Monte Carlo
transport. We need to tally radiation levels at the level of a millirem
or less from the attenuation of a megarem source. In an analog Monte
Carlo model, in which there is no variance reduction, one particle in
approximately 10^9^ would contribute to the tally. Such a model would
require an unreasonable long computation time.

We use the technique of importance splitting to concentrate the
population of neutrons and photons in cells that contribute the tallies.
(Splitting was not applied to protons.) Each cell is assigned an
*importance* value. When a particle enters a cell with twice the
importance as the cell it has left, the particle is split into two
particles, each with ½ the original particle weight. Going the other
way, ½ of the particles, on average, are terminated while preserving the
total weight of particles. A careful adjustment of importances with
depth into absorbing layers of tuff and concrete will increase the
particle concentration enough to balance the particles lost by
absorption and ensure that sufficient particles arrive at the tally to
achieve good statistics. If the importance does not increase greatly
enough with depth, the particle population will fall off and few, if
any, will reach the tally. On the other hand, when the importance
function grows too rapidly with depth, the particle population will
increase exponentially as will the computer time required to follow
those particles.

In a good Monte Carlo model, the importances should be matched so that
they vary by not more than a factor of two from cell to cell. Because of
the complex geometry of the full IPF model, described, below, we were
unable to construct a global importance function that would provide for
optimum transport through the tuff opposite the 110 MeV beam spill and
through the shield wall while maintaining good importance matching. We
instead made several calculations modeling different shielding regions.

Point detectors are a variance reduction technique that uses attenuation
along a ray to estimate the tally at the detector. Following each
collision of a Monte Carlo particle, the detector tally is incremented
by the weight the Monte Carlo particle would contribute if it were to
travel in a straight line to the detector attenuated by the material in
between. We used several point detectors in the excavated area of the
full IPF model. The use of the point detectors increased the calculation
time by hundreds of percent and did not provide tallies with good
statistics. Because of these limitations, we did not use them in
subsequent calculations.

![](media/image2.wmf){width="5.996527777777778in"
height="5.788888888888889in"}

Figure 1---Floor plan of the complete IPF model showing the location of
beam spills (red circles) and surfaces on which the flux was saved to a
surface source file.

## Tally Results

For most models, we present tables of the DER at various positions
through the model. In addition to the total DER, we also give the
neutron and photon components. The Monte Carlo accuracy is given by the
*Relative Error* (RE). The MCNP manual characterizes tallies with REs as
"generally reliable", those with REs between 0.2 and 0.5 as within a
"factor of a few", and any with a larger error as "garbage".

Because we used a computer program to process the results for the
Tables, most tally values carry more digits than are significant. In
most cases, 2 or 3 significant digits would be appropriate. The Tables
should be viewed with this proviso in mind.

# Construction Phase

## Full IPF Model

Construction of the IPF will require excavation of an area beyond the
existing beam line stubout. A number of drilled concrete piers will
provide shoring and support additional shoring. Following excavation,
the shield wall will be built at the end of the stubout. We constructed
a model of the IPF construction phase (Figure 1, Figure 2 shows more
detail in the stubout and shield wall) consisting of a portion of the
existing LANSCE tunnel and beam line, existing stubout, shield wall,
concrete piers, and surrounding tuff. The excavated area extends from
the top of the model, coincident with the top of the piers, to the
bottom of the tunnel floor level.

The shield wall and tuff layers must provide sufficient shielding so
that the DER in the excavated area is less than 1 mrem/hour for a 10
amp beam spill and less than 25 rem/hour for a 1500 amp spill. Because
the results scale with beam current, the 1 mrem/hour limit is the more
stringent. The results below, in mrem/hour for a 10 amp spill, are,
when multiplied by 0.15, the DER in rem/hour for a 1500 amp spill.

We assumed the area labeled *Back Filled* in Figure 1 would be filled
with soil, to at least to the level of the top of the lower shield,
following construction of the shield wall. We did not include two piers
that will be drilled directly adjacent to the external stubout end wall
and fully incorporated in the shield. We assume the spaces between the
existing wall and piers will be filled with concrete in this and other
shield models.

Because of the difficulties in achieving good variance reduction as
described above and hence obtaining meaningful tallies, we did not
pursue calculations using the full model. Instead, we did a number of
calculations focusing on specific regions.

## Beam Spills

The (draft) *Isotope Production Facility (IPF) Radiological Summary*
describes the two worst case beam spills in the existing beam line
during operations while IPF construction is ongoing:

> **5.1 Source Terms for the Construction Phase**
>
> The construction phase of the project applies up to the point at which
> installation of beam line components in the new portion of the lower
> level of the facility begins. At this point the construction of the
> lower facility is completed and the penetrations in the shield wall
> have been opened to allow installation of the beam pipe. Thus, the
> configuration after this point more closely resembles that of the
> completed facility than that during construction.
>
> During the construction phase it is not possible to propagate beam
> into the new beam line, since the kicker magnet will not be activated.
> Therefore, beam spills are limited to the existing beam line.
> Furthermore, because there will be no users of H^+^ beam for the
> immediate future, beam spills will be limited to the H^-^ leg of the
> transition region.
>
> **5.1.1 Beam Spills during Normal Operations.** During tuning
> operations it is customary to deliberately spill small amounts of beam
> until the beam is located and properly steered through the beam line.
> These beam spills can occasionally amount to 10 microamperes of beam
> current. The location of the spill and the direction of the beam at
> that point are important in determining the radiation dose rates, both
> inside and outside the tunnel.
>
> There are two cases that must be considered. The first is beam
> spillage in the transition region (TR), while the second is beam
> spillage in module 5 downstream of the transition region where the
> dirt region between the beam tunnel and the excavated construction
> area will be the thinnest.
>
> **5.1.1.1 Low-Power Beam Spill in the TR Region.** Most of the
> possible beam spill locations in the H^-^ side of the TR are within
> magnet yokes or in regions in which the beam is directed away from the
> north wall of the beam tunnel. However, there is one location at which
> the beam is directed toward the north wall and a magnet failure could
> allow the beam to propagate toward the beam tunnel wall without
> encountering the magnet yoke or any other metallic structure besides
> the beam pipe itself. This constitutes the worst location for such a
> beam spill.
>
> This is the case in which bending magnet BM04 fails, allowing the beam
> to impinge on the beam pipe at an angle of 20 degrees relative to the
> beam line axis. The beam pipe at this location is constructed of
> stainless steel with 0.035 in. walls, oriented at 20 degrees in the
> opposite direction to accommodate H^+^ beam from the opposite side of
> the TR. Most of the beam will pass through the stainless steel beam
> pipe, propagate across the space between the beam line and the wall,
> and then impinge on the concrete wall at a 20 degree angle.
>
> **5.1.1.2 Low-Power Beam Spill Downstream of the TR Region.** This is
> the case of a low-power beam spill within the side coupled linac
> downstream of the TR. In this portion of the accelerator the beam is
> never off axis; a beam spill would always be at a very small angle to
> the beam axis. The side coupled linac is constructed largely of
> copper. The energy of the beam will increase gradually with increasing
> distance from the TR. Therefore, the worst case will consist of a 10
> microampere beam spill on a stopping length of copper at beam line
> center. The incidence angle of the beam will be zero degrees with
> respect to the tunnel axis, and the beam energy will be 110 MeV.
>
> **5.1.2 Worst-Case Design Basis Beam Spills.** The worst-case design
> basis accident consists of a full-power beam spill at a location
> chosen to result in the maximum dose rate outside of the shielded
> area. In this analysis a full-power beam spill corresponds to 1.5
> milliamperes of beam current, which is the maximum current that the
> accelerator is capable of delivering.
>
> There are two cases that must be considered. The first is beam
> spillage in the transition region, while the second is beam spillage
> in module 5 downstream of the transition region where the dirt region
> between the beam tunnel and the excavated construction area will be
> the thinnest.

![](media/image3.wmf){width="5.767361111111111in"
height="8.176388888888889in"}

Figure 2---Detail of the floor plan of the complete IPF model showing
relevant dimensions.

The document goes on to describe the same locations for the worst case
high power spills as for the lower power spills. The Monte Carlo
analysis is independent of the beam power. An overall multiplier
converts the per proton results to reflect the beam current.

We refer to the spill in the TR region resulting from failure of the
BM04 magnet as the *100 MeV* spill and the spill further downstream as
the *110 MeV* spill. The locations of both spills are shown in Figure 1,
and that of the 100 MeV spill in Figure 2. In the 100 MeV case, most of
the spill radiation is generated when the beam strikes the concrete
wall. Radiation from the beam striking a metal target may have a harder
spectrum and be more penetrating. To assess such effects, we considered
a 100 MeV *on-axis* spill onto a stainless steel plug in the beam line
centered between the stubout walls.

For all spills, we modeled the beam tube as a 6 inch OD stainless steel
tube (SS--304) with wall thickness 0.035" containing vacuum.

### 110 MeV Beam Spill

We choose the location of the 110 MeV spill opposite the smallest
thickness of tuff. This thickness is about 16 ½ feet. Because we did not
model penetration in the full IPF model, that the maximum dose rate
occurs a bit further downstream does not matter. The 17.375' dimension
in Figure 1 marks the position of the start of a copper beam obstruction
that simulates the spill. The obstruction downstream of the spill
location is a solid cylinder the same diameter as the beam line. A
pencil beam of 110 MeV protons at the center of the beam line impinged
upon the obstruction. We viewed the tracks of particles from several
histories to verify the placement of the beam.

(The figure on the cover of this document does *not* represent this
spill. The spill in this figure is further upstream, and a photon beam
was substituted for the proton beam.)

![](media/image4.png){width="2.8694444444444445in"
height="2.922222222222222in"}![](media/image5.png){width="2.922222222222222in"
height="2.96875in"}

Figure 3---Particle tracks used to verify the placement of the 20 100
MeV beam spill.

### 100 MeV Beam Spill

The location of the 100 MeV spill was determined from measurements on a
blue print showing the location of the H^-^ line and the magnets. A
pencil beam of 100 MeV protons was directed 20 from the beam axis in
the same vertical plane. To verify the beam placement, we substituted a
photon beam for the proton beam to eliminate deflection of the beam by
the beam tube wall and examined the tracks of Monte Carlo particles with
the Sabrina graphics code. Figure 3 shows the tracks from one such
history. The angle between the beam and the beam tube in the left panel
is 20. The view in the right panel is nearly down the axis of the beam
tube. That the primary beam (orange) may not appear horizontal is an
optical illusion.

## Surface Source Write Runs

For both beam spills, we calculated the radiation in a model consisting
of the tunnel and stubout walls, floor, ceiling, beam tube, and interior
air and wrote a *surface source file* of neutrons and photons crossing
two surfaces. These surfaces are shown as heavy green lines in Figure 1.
All surfaces extend from floor to ceiling. Surface 1 extends for 10 feet
on either side of the 110 MeV spill location. Surface 2 is the interior
of the end wall of the stubout that is also the upstream face of the
shield wall. We made a separate surface source write run, with only the
100 MeV spill, for surface 3 which is the oblique section of tunnel wall
on which the 100 MeV spill impinges. The latter run included only that
interior airspace indicated by the gold cross-hatching in Figure 1.

## Tuff Penetration Model 1

We constructed a simple model, shown in Figure 4, to model the
penetration of radiation into the tunnel wall and tuff opposite the 110
MeV beam spill location. The model extends 10 feet on either side of the
spill location, from the far inner tunnel wall to 20.4 feet into the
tuff on the near IPF side, and from top of the ceiling to the bottom of
the floor. The heavy green line shows the surface corresponding to
surface 1 in the surface source write runs. This file served as the
source.

We made tallies at a number of depths into the tuff; the depth is
measured from the inner wall surface. To account for the forward
streaming effect of the 110 MeV spill, we divided into seven segments
along the beam direction; the *Distance Along Wall* values are the
locations of the midpoints of these segments relative to the spill
location; a positive value is downstream of the spill.

We show here the results from the 110 MeV spill. The DERs resulting from
the 100 MeV spill are much smaller (the rates in the first few tuff
layers are down by a factor of 35, the 100 MeV statistics in deeper
layers are too large for meaningful comparison). The results are given
in mrem/hour for a 10 amp beam current. To obtain rem/hour for a 1.5
milliamp spill, multiply the DERs by 0.15.

Table 9 through Table 15 list the DERs as a function of depth for each
distance. The tables list the neutron and photon contributions the DER
and the Total, and the relative errors for each. Figure 5 shows the
total DER as a function of depth for each distance, while Figure 6 shows
the variation with distance for each depth.

At a depth of 16.3 feet, the largest DER is 0.2 mrem/hour in the segment
5.7 feet downstream of the spill location. The closest distance to the
excavated area, measured from the inner tunnel wall surface to the plane
through the center of the concrete piers (Figure 1), is approximately 16
½ feet. The DER in the excavated area due to a 10 amp 110 MeV beam
spill downstream of the stubout will be less than a mrem/hour. The
concrete piers, for which we do not account, will provide additional
shielding.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 4        | 0.159  | 1        | 0.038  | 66      | 0.113  |
|         | 75.07098 |        | 94.74899 |        | 9.81995 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 78.63010 | 0.325  | 25.12670 | 0.053  | 10      | 0.247  |
|         |          |        |          |        | 3.75680 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 20.29270 | 0.400  | 3.70799  | 0.086  | 2       | 0.339  |
|         |          |        |          |        | 4.00069 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 3.73113  | 0.366  | 0.68704  | 0.119  | 4.41817 | 0.310  |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 1.26475  | 0.329  | 0.13747  | 0.148  | 1.40222 | 0.297  |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 0.37316  | 0.335  | 0.02886  | 0.168  | 0.40203 | 0.311  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 0.10330  | 0.324  | 0.00732  | 0.188  | 0.11062 | 0.302  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 0.06292  | 0.349  | 0.00319  | 0.225  | 0.06611 | 0.333  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 0.03061  | 0.450  | 0.00169  | 0.260  | 0.03230 | 0.427  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.01578  | 0.414  | 0.00083  | 0.288  | 0.01661 | 0.393  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.00904  | 0.421  | 0.00037  | 0.287  | 0.00941 | 0.405  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.00518  | 0.379  | 0.00024  | 0.298  | 0.00543 | 0.362  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.00361  | 0.422  | 0.00013  | 0.325  | 0.00374 | 0.408  |
+---------+----------+--------+----------+--------+---------+--------+

Table 9---Dose Equivalent Rates, as a function of depth from tunnel wall
surface, centered 8.57 feet upstream of the 10 amp 110 MeV beam spill
in tuff penetration model 1.

![](media/image6.wmf){width="5.070138888888889in"
height="8.695833333333333in"}

Figure 4---Tuff penetration model 1 geometry.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 1        | 0.091  | 4        | 0.028  | 19      | 0.071  |
|         | 534.6699 |        | 48.92102 |        | 83.5909 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 2        | 0.145  | 63.25500 | 0.036  | 31      | 0.116  |
|         | 52.04500 |        |          |        | 5.29999 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 61.30920 | 0.193  | 9.55624  | 0.051  | 7       | 0.168  |
|         |          |        |          |        | 0.86544 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 12.38810 | 0.237  | 1.57402  | 0.075  | 1       | 0.211  |
|         |          |        |          |        | 3.96212 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 3.89622  | 0.244  | 0.31290  | 0.097  | 4.20912 | 0.226  |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 1.30094  | 0.297  | 0.07426  | 0.144  | 1.37520 | 0.281  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 0.31203  | 0.330  | 0.01811  | 0.200  | 0.33014 | 0.312  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 0.16512  | 0.350  | 0.00819  | 0.223  | 0.17330 | 0.334  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 0.08779  | 0.311  | 0.00442  | 0.246  | 0.09221 | 0.296  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.04677  | 0.299  | 0.00205  | 0.242  | 0.04882 | 0.286  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.02605  | 0.275  | 0.00113  | 0.229  | 0.02718 | 0.264  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.01635  | 0.300  | 0.00059  | 0.248  | 0.01694 | 0.290  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.00990  | 0.328  | 0.00034  | 0.261  | 0.01023 | 0.317  |
+---------+----------+--------+----------+--------+---------+--------+

Table 10---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 5.71 feet upstream of the 10 amp 110 MeV beam
spill in tuff penetration model 1.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 3        | 0.064  | 8        | 0.022  | 47      | 0.053  |
|         | 898.2199 |        | 05.03406 |        | 03.2539 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 6        | 0.113  | 1        | 0.029  | 72      | 0.096  |
|         | 17.73102 |        | 08.06500 |        | 5.79602 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 1        | 0.155  | 17.90360 | 0.044  | 15      | 0.138  |
|         | 38.60501 |        |          |        | 6.50861 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 30.36850 | 0.179  | 3.01574  | 0.065  | 3       | 0.163  |
|         |          |        |          |        | 3.38424 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 10.12760 | 0.176  | 0.65377  | 0.092  | 1       | 0.166  |
|         |          |        |          |        | 0.78137 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 2.71567  | 0.167  | 0.15046  | 0.106  | 2.86613 | 0.158  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 0.74095  | 0.182  | 0.03863  | 0.131  | 0.77958 | 0.173  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 0.43170  | 0.222  | 0.01852  | 0.139  | 0.45022 | 0.213  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 0.24339  | 0.229  | 0.01060  | 0.171  | 0.25400 | 0.219  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.14672  | 0.242  | 0.00604  | 0.212  | 0.15275 | 0.233  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.08408  | 0.290  | 0.00322  | 0.214  | 0.08730 | 0.280  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.05224  | 0.336  | 0.00182  | 0.256  | 0.05406 | 0.325  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.03074  | 0.351  | 0.00112  | 0.265  | 0.03186 | 0.339  |
+---------+----------+--------+----------+--------+---------+--------+

Table 11---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 2.86 feet upstream of the 10 amp 110 MeV beam
spill in tuff penetration model 1.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 6        | 0.060  | 9        | 0.020  | 76      | 0.052  |
|         | 705.4697 |        | 06.29797 |        | 11.7675 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 1        | 0.086  | 1        | 0.031  | 14      | 0.077  |
|         | 284.4000 |        | 37.84601 |        | 22.2460 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 2        | 0.106  | 23.23630 | 0.045  | 31      | 0.098  |
|         | 91.71399 |        |          |        | 4.95029 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 79.33130 | 0.128  | 5.10123  | 0.070  | 8       | 0.121  |
|         |          |        |          |        | 4.43253 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 20.83480 | 0.161  | 1.13128  | 0.088  | 2       | 0.153  |
|         |          |        |          |        | 1.96608 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 6.26615  | 0.199  | 0.28507  | 0.130  | 6.55122 | 0.191  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 2.03901  | 0.282  | 0.07993  | 0.173  | 2.11894 | 0.271  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 1.30489  | 0.301  | 0.04471  | 0.222  | 1.34960 | 0.291  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 0.72078  | 0.342  | 0.02417  | 0.236  | 0.74495 | 0.331  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.46214  | 0.354  | 0.01386  | 0.265  | 0.47600 | 0.344  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.26296  | 0.347  | 0.00810  | 0.288  | 0.27107 | 0.337  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.15795  | 0.379  | 0.00477  | 0.303  | 0.16272 | 0.368  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.09282  | 0.379  | 0.00283  | 0.318  | 0.09565 | 0.367  |
+---------+----------+--------+----------+--------+---------+--------+

Table 12---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered on the 10 amp 110 MeV beam spill in tuff
penetration model 1.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 9        | 0.055  | 7        | 0.023  | 99      | 0.051  |
|         | 146.9902 |        | 82.92999 |        | 29.9199 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 2        | 0.076  | 1        | 0.034  | 22      | 0.072  |
|         | 126.4199 |        | 41.39499 |        | 67.8149 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 5        | 0.095  | 28.46150 | 0.053  | 55      | 0.090  |
|         | 24.04999 |        |          |        | 2.51147 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 1        | 0.115  | 6.53480  | 0.075  | 15      | 0.110  |
|         | 48.21100 |        |          |        | 4.74580 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 44.19120 | 0.149  | 1.70747  | 0.093  | 4       | 0.143  |
|         |          |        |          |        | 5.89867 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 13.64380 | 0.188  | 0.46263  | 0.130  | 1       | 0.182  |
|         |          |        |          |        | 4.10643 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 4.26194  | 0.212  | 0.14000  | 0.159  | 4.40195 | 0.205  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 2.37945  | 0.237  | 0.07572  | 0.190  | 2.45517 | 0.230  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 1.31890  | 0.247  | 0.04190  | 0.202  | 1.36080 | 0.240  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.74022  | 0.263  | 0.02355  | 0.229  | 0.76377 | 0.255  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.42373  | 0.294  | 0.01317  | 0.241  | 0.43690 | 0.285  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.25874  | 0.306  | 0.00755  | 0.254  | 0.26630 | 0.297  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.14415  | 0.311  | 0.00431  | 0.274  | 0.14846 | 0.302  |
+---------+----------+--------+----------+--------+---------+--------+

Table 13---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 2.86 feet downstream of the 10 amp 110 MeV beam
spill in tuff penetration model 1.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 9        | 0.058  | 5        | 0.029  | 95      | 0.055  |
|         | 014.6992 |        | 73.02197 |        | 87.7207 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 2        | 0.075  | 1        | 0.041  | 23      | 0.071  |
|         | 214.5798 |        | 16.78600 |        | 31.3657 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 5        | 0.090  | 25.85470 | 0.055  | 59      | 0.086  |
|         | 73.69299 |        |          |        | 9.54767 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 1        | 0.102  | 6.63922  | 0.070  | 16      | 0.098  |
|         | 56.57300 |        |          |        | 3.21222 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 45.84890 | 0.113  | 1.77265  | 0.085  | 4       | 0.109  |
|         |          |        |          |        | 7.62155 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 14.38030 | 0.131  | 0.49997  | 0.103  | 1       | 0.127  |
|         |          |        |          |        | 4.88027 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 4.67226  | 0.159  | 0.15648  | 0.122  | 4.82873 | 0.154  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 2.62220  | 0.170  | 0.08394  | 0.138  | 2.70614 | 0.165  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 1.39616  | 0.174  | 0.04536  | 0.147  | 1.44152 | 0.169  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.79244  | 0.185  | 0.02513  | 0.159  | 0.81757 | 0.180  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.45719  | 0.196  | 0.01405  | 0.172  | 0.47124 | 0.190  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.26652  | 0.209  | 0.00806  | 0.183  | 0.27458 | 0.203  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.15573  | 0.225  | 0.00454  | 0.201  | 0.16027 | 0.219  |
+---------+----------+--------+----------+--------+---------+--------+

Table 14---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 5.71 feet downstream of the 10 amp 110 MeV beam
spill in tuff penetration model 1.

+---------+----------+--------+----------+--------+---------+--------+
| **      | **N      |        | **       |        | **      |        |
| Depth** | eutron** |        | Photon** |        | Total** |        |
|         |          |        |          |        |         |        |
| **(     |          |        |          |        |         |        |
| feet)** |          |        |          |        |         |        |
+---------+----------+--------+----------+--------+---------+--------+
|         | **DER    | **RE** | **DER    | **RE** | **DER   | **RE** |
|         | (mr      |        | (mr      |        | (mre    |        |
|         | em/hr)** |        | em/hr)** |        | m/hr)** |        |
+---------+----------+--------+----------+--------+---------+--------+
| 3.76    | 5        | 0.076  | 2        | 0.042  | 59      | 0.073  |
|         | 633.8598 |        | 91.46399 |        | 25.3237 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 5.15    | 1        | 0.089  | 61.33320 | 0.053  | 14      | 0.085  |
|         | 436.3200 |        |          |        | 97.6533 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 6.54    | 3        | 0.100  | 14.53500 | 0.066  | 37      | 0.096  |
|         | 56.63800 |        |          |        | 1.17300 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 7.94    | 1        | 0.112  | 3.83805  | 0.080  | 11      | 0.108  |
|         | 07.36500 |        |          |        | 1.20305 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 9.33    | 33.14850 | 0.118  | 1.10724  | 0.096  | 3       | 0.114  |
|         |          |        |          |        | 4.25574 |        |
+---------+----------+--------+----------+--------+---------+--------+
| 10.72   | 9.69567  | 0.135  | 0.28438  | 0.107  | 9.98005 | 0.131  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.12   | 2.95637  | 0.140  | 0.08944  | 0.126  | 3.04581 | 0.136  |
+---------+----------+--------+----------+--------+---------+--------+
| 12.81   | 1.61854  | 0.144  | 0.04636  | 0.128  | 1.66490 | 0.140  |
+---------+----------+--------+----------+--------+---------+--------+
| 13.51   | 0.86568  | 0.150  | 0.02613  | 0.133  | 0.89181 | 0.146  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.21   | 0.50703  | 0.160  | 0.01484  | 0.140  | 0.52186 | 0.156  |
+---------+----------+--------+----------+--------+---------+--------+
| 14.90   | 0.30426  | 0.166  | 0.00822  | 0.148  | 0.31248 | 0.162  |
+---------+----------+--------+----------+--------+---------+--------+
| 15.60   | 0.17554  | 0.176  | 0.00475  | 0.158  | 0.18028 | 0.171  |
+---------+----------+--------+----------+--------+---------+--------+
| 16.30   | 0.09770  | 0.186  | 0.00263  | 0.166  | 0.10033 | 0.181  |
+---------+----------+--------+----------+--------+---------+--------+

Table 15---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 8.57 feet downstream of the 10 amp 110 MeV beam
spill in tuff penetration model 1.

![](media/image7.wmf){width="5.999305555555556in"
height="4.527777777777778in"}

Figure 5---Total dose equivalent rate as a function of distance from the
tunnel wall surface in tuff penetration model 1 for a 10 amp 110 MeV
beam spill. The various curves represent the DER in 2.86 foot wide
segments perpendicular to the wall.

## Tuff Penetration Model 3

We constructed a simple model, shown in Figure 7, to model the
penetration of radiation into the tunnel wall and tuff beyond the wall
struck by the 100 MeV beam spill. The model extends 6 feet on either
side of the 4 foot long original wall, from the far inner tunnel wall to
16.3 feet into the tuff, and from bottom of the ceiling to the top of
the floor. The heavy green line shows the surface corresponding to
surface 3 in the surface source write run. This file served as the
source for the model.

We made tallies at a number of depths into the tuff; the depth is
measured from the inner wall surface. We divided the tallies into three
segments perpendicular to the wall. The center segment lies beyond the
original wall. The two side segments occupy the adjoining four feet.

We show here the results from the 100 MeV spill. Because the penetration
of the 100 MeV spill is greater than the penetration of the 110 MeV
spill in Model 1, the diminished radiation from the 110 MeV spill at
surface 3, in comparison to surface 1, should result in even less
penetration beyond surface 3.

![](media/image8.wmf){width="5.999305555555556in"
height="4.527777777777778in"}

Figure 6---Total dose equivalent rate as a function of distance,
parallel to the beam line, from the 10 amp 110 MeV beam spill at
several depths into tuff from the tunnel wall surface.

The results are given in mrem/hour for a 10 amp beam current. To obtain
rem/hour for a 1.5 milliamp spill, multiply the DERs by 0.15.

Table 16, Table 17, and Table 18 list the DERs as a function of depth
for each segment. Table 19 is the DER averaged over all three segments.
The tables list the neutron and photon contributions the DER and the
Total, and the relative errors for each. Figure 8 shows the total DER as
a function of depth for each distance.

The average over all segments, which has the best statistics, shows that
the DER is below 0.1 mrem/hour for depths beyond 16 feet. The path
length through tuff and/or concrete from the wall coincident with
surface 3 is at least 19 feet. Tuff penetration at this location is thus
not a concern.

![](media/image9.wmf){width="4.850694444444445in"
height="8.633333333333333in"}

Figure 7---Tuff penetration model 3 geometry.

+--------+------------+------+------------+------+------------+-----+
| **D    | *          |      | **Photon** |      | **Total**  |     |
| epth** | *Neutron** |      |            |      |            |     |
|        |            |      |            |      |            |     |
| **(f   |            |      |            |      |            |     |
| eet)** |            |      |            |      |            |     |
+--------+------------+------+------------+------+------------+-----+
|        | **DER      | **   | **DER      | **   | **DER      | **R |
|        | (          | RE** | (          | RE** | (          | E** |
|        | mrem/hr)** |      | mrem/hr)** |      | mrem/hr)** |     |
+--------+------------+------+------------+------+------------+-----+
| 1.57   | 62         | 0    | 1          | 0    | 64         | 0.  |
|        | 603.500000 | .060 | 663.540039 | .057 | 267.039063 | 059 |
+--------+------------+------+------------+------+------------+-----+
| 3.79   | 13         | 0    | 512.108032 | 0    | 13         | 0.  |
|        | 348.299805 | .066 |            | .056 | 860.408203 | 063 |
+--------+------------+------+------------+------+------------+-----+
| 8.46   | 500.420990 | 0    | 16.413700  | 0    | 516.834717 | 0.  |
|        |            | .119 |            | .097 |            | 115 |
+--------+------------+------+------------+------+------------+-----+
| 10.79  | 59.592800  | 0    | 2.020760   | 0    | 61.613560  | 0.  |
|        |            | .144 |            | .141 |            | 140 |
+--------+------------+------+------------+------+------------+-----+
| 11.96  | 18.340799  | 0    | 0.729458   | 0    | 19.070257  | 0.  |
|        |            | .171 |            | .147 |            | 165 |
+--------+------------+------+------------+------+------------+-----+
| 13.12  | 8.938240   | 0    | 0.324080   | 0    | 9.262320   | 0.  |
|        |            | .233 |            | .201 |            | 225 |
+--------+------------+------+------------+------+------------+-----+
| 14.29  | 2.651570   | 0    | 0.090366   | 0    | 2.741936   | 0.  |
|        |            | .253 |            | .199 |            | 245 |
+--------+------------+------+------------+------+------------+-----+
| 15.46  | 0.960709   | 0    | 0.037371   | 0    | 0.998080   | 0.  |
|        |            | .281 |            | .261 |            | 271 |
+--------+------------+------+------------+------+------------+-----+
| 16.62  | 0.330838   | 0    | 0.011348   | 0    | 0.342186   | 0.  |
|        |            | .418 |            | .255 |            | 405 |
+--------+------------+------+------------+------+------------+-----+
| 17.79  | 0.121133   | 0    | 0.004103   | 0    | 0.125236   | 0.  |
|        |            | .585 |            | .293 |            | 566 |
+--------+------------+------+------------+------+------------+-----+
| 18.96  | 0.039997   | 0    | 0.000673   | 0    | 0.040669   | 0.  |
|        |            | .447 |            | .333 |            | 439 |
+--------+------------+------+------------+------+------------+-----+

Table 16---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 4 feet downstream of the 10 amp 100 MeV beam
spill in tuff penetration model 3.

+--------+------------+------+------------+------+------------+-----+
| **D    | *          |      | **Photon** |      | **Total**  |     |
| epth** | *Neutron** |      |            |      |            |     |
|        |            |      |            |      |            |     |
| **(f   |            |      |            |      |            |     |
| eet)** |            |      |            |      |            |     |
+--------+------------+------+------------+------+------------+-----+
|        | **DER      | **   | **DER      | **   | **DER      | **R |
|        | (          | RE** | (          | RE** | (          | E** |
|        | mrem/hr)** |      | mrem/hr)** |      | mrem/hr)** |     |
+--------+------------+------+------------+------+------------+-----+
| 1.57   | 15         | 0    | 4          | 0    | 15         | 0.  |
|        | 11530.0000 | .012 | 0252.80078 | .013 | 51782.7500 | 012 |
+--------+------------+------+------------+------+------------+-----+
| 3.79   | 90         | 0    | 3          | 0    | 94         | 0.  |
|        | 707.804688 | .028 | 813.489990 | .022 | 521.296875 | 027 |
+--------+------------+------+------------+------+------------+-----+
| 8.46   | 987.098999 | 0    | 34.355099  | 0    | 1          | 0.  |
|        |            | .090 |            | .067 | 021.454102 | 087 |
+--------+------------+------+------------+------+------------+-----+
| 10.79  | 106.161003 | 0    | 3.790810   | 0    | 109.951813 | 0.  |
|        |            | .140 |            | .105 |            | 135 |
+--------+------------+------+------------+------+------------+-----+
| 11.96  | 42.727097  | 0    | 1.213600   | 0    | 43.940697  | 0.  |
|        |            | .161 |            | .124 |            | 156 |
+--------+------------+------+------------+------+------------+-----+
| 13.12  | 14.058400  | 0    | 0.486530   | 0    | 14.544930  | 0.  |
|        |            | .239 |            | .153 |            | 231 |
+--------+------------+------+------------+------+------------+-----+
| 14.29  | 3.088240   | 0    | 0.148678   | 0    | 3.236918   | 0.  |
|        |            | .206 |            | .166 |            | 197 |
+--------+------------+------+------------+------+------------+-----+
| 15.46  | 1.511730   | 0    | 0.055680   | 0    | 1.567410   | 0.  |
|        |            | .266 |            | .227 |            | 256 |
+--------+------------+------+------------+------+------------+-----+
| 16.62  | 0.401269   | 0    | 0.015183   | 0    | 0.416452   | 0.  |
|        |            | .278 |            | .261 |            | 268 |
+--------+------------+------+------------+------+------------+-----+
| 17.79  | 0.123544   | 0    | 0.006437   | 0    | 0.129981   | 0.  |
|        |            | .303 |            | .311 |            | 288 |
+--------+------------+------+------------+------+------------+-----+
| 18.96  | 0.020109   | 0    | 0.000516   | 0    | 0.020625   | 0.  |
|        |            | .381 |            | .446 |            | 371 |
+--------+------------+------+------------+------+------------+-----+

Table 17---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered on the 10 amp 100 MeV beam spill in tuff
penetration model 3.

+--------+------------+------+------------+------+------------+-----+
| **D    | *          |      | **Photon** |      | **Total**  |     |
| epth** | *Neutron** |      |            |      |            |     |
|        |            |      |            |      |            |     |
| **(f   |            |      |            |      |            |     |
| eet)** |            |      |            |      |            |     |
+--------+------------+------+------------+------+------------+-----+
|        | **DER      | **   | **DER      | **   | **DER      | **R |
|        | (          | RE** | (          | RE** | (          | E** |
|        | mrem/hr)** |      | mrem/hr)** |      | mrem/hr)** |     |
+--------+------------+------+------------+------+------------+-----+
| 1.57   | 29         | 0    | 1          | 0    | 30         | 0.  |
|        | 2280.00000 | .026 | 1668.10058 | .023 | 3948.09375 | 025 |
+--------+------------+------+------------+------+------------+-----+
| 3.79   | 25         | 0    | 1          | 0    | 26         | 0.  |
|        | 584.900391 | .047 | 296.989990 | .031 | 881.890625 | 044 |
+--------+------------+------+------------+------+------------+-----+
| 8.46   | 353.237976 | 0    | 13.752199  | 0    | 366.990173 | 0.  |
|        |            | .134 |            | .090 |            | 129 |
+--------+------------+------+------------+------+------------+-----+
| 10.79  | 44.965500  | 0    | 1.877620   | 0    | 46.843121  | 0.  |
|        |            | .158 |            | .152 |            | 152 |
+--------+------------+------+------------+------+------------+-----+
| 11.96  | 18.507900  | 0    | 0.536676   | 0    | 19.044577  | 0.  |
|        |            | .227 |            | .172 |            | 220 |
+--------+------------+------+------------+------+------------+-----+
| 13.12  | 6.410131   | 0    | 0.183219   | 0    | 6.593349   | 0.  |
|        |            | .253 |            | .190 |            | 246 |
+--------+------------+------+------------+------+------------+-----+
| 14.29  | 1.671640   | 0    | 0.055288   | 0    | 1.726928   | 0.  |
|        |            | .250 |            | .240 |            | 242 |
+--------+------------+------+------------+------+------------+-----+
| 15.46  | 0.918801   | 0    | 0.035566   | 0    | 0.954367   | 0.  |
|        |            | .255 |            | .251 |            | 246 |
+--------+------------+------+------------+------+------------+-----+
| 16.62  | 0.244518   | 0    | 0.012233   | 0    | 0.256751   | 0.  |
|        |            | .359 |            | .280 |            | 342 |
+--------+------------+------+------------+------+------------+-----+
| 17.79  | 0.135789   | 0    | 0.002617   | 0    | 0.138406   | 0.  |
|        |            | .435 |            | .319 |            | 426 |
+--------+------------+------+------------+------+------------+-----+
| 18.96  | 0.027684   | 0    | 0.000669   | 0    | 0.028353   | 0.  |
|        |            | .499 |            | .403 |            | 487 |
+--------+------------+------+------------+------+------------+-----+

Table 18---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, centered 4 feet upstream of the 10 amp 100 MeV beam spill
in tuff penetration model 3.

+--------+------------+------+------------+------+------------+-----+
| **D    | *          |      | **Photon** |      | **Total**  |     |
| epth** | *Neutron** |      |            |      |            |     |
|        |            |      |            |      |            |     |
| **(f   |            |      |            |      |            |     |
| eet)** |            |      |            |      |            |     |
+--------+------------+------+------------+------+------------+-----+
|        | **DER      | **   | **DER      | **   | **DER      | **R |
|        | (          | RE** | (          | RE** | (          | E** |
|        | mrem/hr)** |      | mrem/hr)** |      | mrem/hr)** |     |
+--------+------------+------+------------+------+------------+-----+
| 1.57   | 57         | 0    | 1          | 0    | 59         | 0.  |
|        | 767.000000 | .011 | 667.719971 | .011 | 434.718750 | 011 |
+--------+------------+------+------------+------+------------+-----+
| 3.79   | 4          | 0    | 177.287994 | 0    | 4          | 0.  |
|        | 083.949951 | .024 |            | .019 | 261.237793 | 023 |
+--------+------------+------+------------+------+------------+-----+
| 8.46   | 59.865002  | 0    | 2.095640   | 0    | 61.960640  | 0.  |
|        |            | .073 |            | .056 |            | 071 |
+--------+------------+------+------------+------+------------+-----+
| 10.79  | 6.881070   | 0    | 0.250874   | 0    | 7.131944   | 0.  |
|        |            | .101 |            | .088 |            | 098 |
+--------+------------+------+------------+------+------------+-----+
| 11.96  | 2.577680   | 0    | 0.081172   | 0    | 2.658852   | 0.  |
|        |            | .126 |            | .100 |            | 122 |
+--------+------------+------+------------+------+------------+-----+
| 13.12  | 0.964513   | 0    | 0.032629   | 0    | 0.997142   | 0.  |
|        |            | .165 |            | .124 |            | 160 |
+--------+------------+------+------------+------+------------+-----+
| 14.29  | 0.245708   | 0    | 0.009632   | 0    | 0.255340   | 0.  |
|        |            | .163 |            | .144 |            | 157 |
+--------+------------+------+------------+------+------------+-----+
| 15.46  | 0.111350   | 0    | 0.004231   | 0    | 0.115581   | 0.  |
|        |            | .189 |            | .188 |            | 182 |
+--------+------------+------+------------+------+------------+-----+
| 16.62  | 0.032338   | 0    | 0.001280   | 0    | 0.033618   | 0.  |
|        |            | .230 |            | .185 |            | 221 |
+--------+------------+------+------------+------+------------+-----+
| 17.79  | 0.012675   | 0    | 0.000431   | 0    | 0.013106   | 0.  |
|        |            | .291 |            | .250 |            | 282 |
+--------+------------+------+------------+------+------------+-----+
| 18.96  | 0.002987   | 0    | 0.000062   | 0    | 0.003050   | 0.  |
|        |            | .297 |            | .263 |            | 291 |
+--------+------------+------+------------+------+------------+-----+

Table 19---Dose Equivalent Rates, as a function of depth from tunnel
wall surface, averaged over the segments of Table 16, Table 17, and
Table 18 in tuff penetration model 3 for a 10 amp 100 MeV beam spill.

![](media/image10.wmf){width="5.999305555555556in"
height="4.527777777777778in"}

Figure 8---Total dose equivalent rate as a function of distance from the
tunnel wall surface in tuff penetration model 3 for a 10 amp 100 MeV
beam spill. The various curves represent the DER in 4 foot wide segments
perpendicular to the wall.

## Shield Wall Penetration---20° Off Axis Spill

We used a surface source on surface 2, the inside wall of the stubout
end from floor to ceiling and wall to wall, to investigate penetration
of the beam spill radiation through the shield wall. Figure 9 shows a
vertical cut through the shield wall. Figure 10 and Figure 12 are
horizontal cuts through the thicker lower portion of the shield. Figure
13 and Figure 14 are horizontal cuts through the middle and upper
shield, respectively. The middle shield contains a cut out to
accommodate electrical utility ducts. The figures represent the extent
of the construction phase shield wall model. There are no penetrations
of the shield in this model.

We show here the results from the 100 MeV spill. The penetration from
the more distant 110 MeV spill is lower (the rates in the first few
shield layers are lower by factors from 66 to 137, the 110 MeV
statistics further into the shield are too large for meaningful
comparisons). The results are given in mrem/hour for a 10 amp beam
current. To obtain rem/hour for a 1.5 milliamp spill, multiply the DERs
by 0.15.

We made tallies in a number of cells throughout the shield and on the
outside surfaces of the middle and upper shields. The figures show the
location of the tallied cells and surfaces. The divisions through the
shield represent importance layers as well as cell boundaries.

We made tallies over several vertical segmentations of the cells in the
lower shield. These cells are shown in Figure 10. Segment A (see Figure
9) from floor to ceiling contains the largest DER. Table 20 gives the
results for this segment. Table 21 lists the tally results for segment B
between the floor surface and shield bottom, and Table 22 for segment C,
the upper 1 foot of the lower shield.

Figure 11 plots the DER in the middle portion of segment A as a function
of distance from the upstream wall (Figure 10 shows a typical distance).
The total DER is nearly a straight line given by log~10~ DER = -0.4
*d* + 5.38, where *d* is the distance into the shield in feet. The total
DER decreases by a factor of 10 for every 2.5 feet of concrete.

The DER at the downstream face of the shield is 0.33 mrem/hour for a 10
amp beam spill, a factor of 3 below the desired limit of 1 mrem/hour.
The corresponding DER for a 1500 amp spill is 0.05 rem/hour, much below
the desired 25 rem/hour. The cells in the left side \[marked (L)\] of
the shield are adjacent to the region marked in Figure 1 as "Back
Filled". The large DER in these cells shows the importance of filling
this region with soil following construction of the shield wall.

We introduced additional vertical importance splitting to improve the
statistics at the junction of the lower and middle shields. To focus on
the radiation levels at the uncovered top of the lower shield, we
introduced a layer of cells extending 6.86 inches below the top surface
(extent D in Figure 9). Figure 12 shows the cells in this layer in which
tallies were taken along with the total DER in those cells. Table 23
lists the tallies.

Table 24 lists tallies in those cells in the middle shield that are
shown, along with the total DER, in Figure 13. Table 25 lists tallies in
those cells in the upper shield that are shown in Figure 14. Table 26
gives tallies on the outer surfaces of the middle and upper shields.

![](media/image11.wmf){width="4.101388888888889in"
height="8.238888888888889in"}

Figure 9---Cross section of the shield wall showing vertical dimensions,
the vertical extent of cell tallies, and locations of surface tallies.

![](media/image12.wmf){width="5.9944444444444445in"
height="5.205555555555556in"}

Figure 10---Cut through the lower shield showing the cells in which
tallies were taken.

The DER near the junction of the lower and middle shields is a concern.
Several cells near the surface have rates of several mrem/hour, larger
than the desired limit of 1 mrem/hour for a a 10 amp beam spill. The
DER in the air outside of and near these surfaces will also have a
higher DER. This region will be occupied by utility duct enclosed in
concrete. If the DER decreases an order of magnitude for every 2.5 feet
of concrete, as it does through the center of the shield, 2 ½ feet of
concrete in the duct and in additional concrete should provide adequate
shielding. Note also that we did not account for radiation entering the
shield through the tunnel ceiling; we have thus underestimated the DER
somewhat in this region.

The DERs in the left cells in the middle shield, adjacent to the back
filled region, are 1 mrem/hour or less. If possible, the back filling
should extend to at least the top of the middle shield.

+----+--------+-----------+-----+----------+-----+-----------+-----+
| ** | **Di   | **        |     | **       |     | **Total** |     |
| Ce | stance | Neutron** |     | Photon** |     |           |     |
| ll | into   |           |     |          |     |           |     |
| ** | Shield |           |     |          |     |           |     |
|    | (f     |           |     |          |     |           |     |
|    | eet)** |           |     |          |     |           |     |
+----+--------+-----------+-----+----------+-----+-----------+-----+
|    |        | **DER**   | **R | **DER    | **R | **DER**   | **R |
|    |        |           | E** | (mr      | E** |           | E** |
|    |        | **(m      |     | em/hr)** |     | **(m      |     |
|    |        | rem/hr)** |     |          |     | rem/hr)** |     |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 1.79   | 44        | 0.  | 14       | 0.  | 46        | 0.  |
| 38 |        | 815.89844 | 029 | 70.85010 | 022 | 286.75000 | 028 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 2.37   | 22        | 0.  | 7        | 0.  | 23        | 0.  |
| 37 |        | 538.20117 | 035 | 48.43201 | 025 | 286.63281 | 033 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 3.53   | 5         | 0.  | 1        | 0.  | 5         | 0.  |
| 35 |        | 724.86035 | 046 | 84.61700 | 034 | 909.47754 | 044 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 4.68   | 1         | 0.  | 47.01390 | 0.  | 1         | 0.  |
| 33 |        | 468.78003 | 056 |          | 044 | 515.79395 | 054 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 5.84   | 399.88000 | 0.  | 11.99160 | 0.  | 411.87161 | 0.  |
| 31 |        |           | 067 |          | 055 |           | 065 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.00   | 110.73300 | 0.  | 3.28302  | 0.  | 114.01602 | 0.  |
| 29 |        |           | 075 |          | 065 |           | 073 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.58   | 58.56370  | 0.  | 1.75701  | 0.  | 60.32071  | 0.  |
| 28 |        |           | 080 |          | 070 |           | 078 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.16   | 31.02850  | 0.  | 0.92975  | 0.  | 31.95825  | 0.  |
| 27 |        |           | 086 |          | 074 |           | 083 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.73   | 16.60890  | 0.  | 0.48671  | 0.  | 17.09561  | 0.  |
| 26 |        |           | 090 |          | 079 |           | 088 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 9.31   | 8.70516   | 0.  | 0.25791  | 0.  | 8.96307   | 0.  |
| 25 |        |           | 095 |          | 085 |           | 092 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 9.89   | 4.54024   | 0.  | 0.13460  | 0.  | 4.67484   | 0.  |
| 24 |        |           | 101 |          | 090 |           | 098 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 10.47  | 2.42756   | 0.  | 0.07088  | 0.  | 2.49844   | 0.  |
| 23 |        |           | 104 |          | 094 |           | 101 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 11.05  | 1.27236   | 0.  | 0.03755  | 0.  | 1.30991   | 0.  |
| 22 |        |           | 107 |          | 098 |           | 104 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 11.63  | 0.68281   | 0.  | 0.01942  | 0.  | 0.70223   | 0.  |
| 21 |        |           | 112 |          | 103 |           | 109 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 12.25  | 0.32200   | 0.  | 0.00874  | 0.  | 0.33074   | 0.  |
| 61 |        |           | 116 |          | 106 |           | 113 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
|    |        |           |     |          |     |           |     |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 2.37   | 2         | 0.  | 96.39690 | 0.  | 2         | 0.  |
| 17 | (L)    | 356.19995 | 144 |          | 086 | 452.59692 | 139 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 2.37   | 3         | 0.  | 1        | 0.  | 3         | 0.  |
| 57 | (R)    | 706.89990 | 103 | 25.75800 | 071 | 832.65796 | 100 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 4.68   | 191.14301 | 0.  | 6.13977  | 0.  | 197.28278 | 0.  |
| 13 | (L)    |           | 205 |          | 146 |           | 198 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 4.68   | 629.92902 | 0.  | 17.67370 | 0.  | 647.60272 | 0.  |
| 53 | (R)    |           | 126 |          | 097 |           | 122 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.00   | 17.10410  | 0.  | 0.46077  | 0.  | 17.56487  | 0.  |
| 09 | (L)    |           | 198 |          | 170 |           | 193 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.00   | 67.21740  | 0.  | 1.89022  | 0.  | 69.10762  | 0.  |
| 49 | (R)    |           | 133 |          | 119 |           | 129 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.73   | 2.43558   | 0.  | 0.07532  | 0.  | 2.51090   | 0.  |
| 06 | (L)    |           | 208 |          | 199 |           | 202 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.73   | 10.12600  | 0.  | 0.29078  | 0.  | 10.41678  | 0.  |
| 46 | (R)    |           | 146 |          | 130 |           | 142 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 10     | 0.31475   | 0.  | 0.01046  | 0.  | 0.32521   | 0.  |
| 03 | .47(L) |           | 207 |          | 201 |           | 201 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 10     | 1.51269   | 0.  | 0.04428  | 0.  | 1.55697   | 0.  |
| 43 | .47(R) |           | 158 |          | 141 |           | 154 |
+----+--------+-----------+-----+----------+-----+-----------+-----+

Table 20---Dose Equivalent Rates between tunnel floor and ceiling levels
(tally segment A) in selected shield cells due to a 10 amp 100 MeV 20
off axis beam spill.

![](media/image13.wmf){width="5.999305555555556in"
height="4.527777777777778in"}

Figure 11---Total dose equivalent rate and the neutron and photon
components as a function of distance from the upstream shield surface
due to the 100 MeV 20 off axis beam spill.

+----+--------+-----------+-----+----------+-----+-----------+-----+
| ** | **Di   | **        |     | **       |     | **Total** |     |
| Ce | stance | Neutron** |     | Photon** |     |           |     |
| ll | into   |           |     |          |     |           |     |
| ** | Shield |           |     |          |     |           |     |
|    | (f     |           |     |          |     |           |     |
|    | eet)** |           |     |          |     |           |     |
+----+--------+-----------+-----+----------+-----+-----------+-----+
|    |        | **DER**   | **R | **DER    | **R | **DER**   | **R |
|    |        |           | E** | (mr      | E** |           | E** |
|    |        | **(m      |     | em/hr)** |     | **(m      |     |
|    |        | rem/hr)** |     |          |     | rem/hr)** |     |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 1.79   | 5         | 0.  | 1        | 0.  | 5         | 0.  |
| 38 |        | 347.75000 | 141 | 61.10001 | 104 | 508.85010 | 137 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 2.37   | 3         | 0.  | 97.66900 | 0.  | 3         | 0.  |
| 37 |        | 015.91016 | 131 |          | 103 | 113.57910 | 127 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 3.53   | 1         | 0.  | 32.96410 | 0.  | 1         | 0.  |
| 35 |        | 029.64001 | 147 |          | 110 | 062.60413 | 142 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 4.68   | 284.33200 | 0.  | 9.17338  | 0.  | 293.50537 | 0.  |
| 33 |        |           | 146 |          | 117 |           | 141 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 5.84   | 94.86420  | 0.  | 2.72827  | 0.  | 97.59247  | 0.  |
| 31 |        |           | 166 |          | 131 |           | 161 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.00   | 29.23910  | 0.  | 0.83274  | 0.  | 30.07184  | 0.  |
| 29 |        |           | 187 |          | 153 |           | 182 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.58   | 15.17160  | 0.  | 0.46799  | 0.  | 15.63959  | 0.  |
| 28 |        |           | 195 |          | 170 |           | 189 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.16   | 8.44214   | 0.  | 0.26407  | 0.  | 8.70621   | 0.  |
| 27 |        |           | 200 |          | 169 |           | 194 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.73   | 4.32029   | 0.  | 0.13358  | 0.  | 4.45387   | 0.  |
| 26 |        |           | 206 |          | 182 |           | 200 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 9.31   | 2.45833   | 0.  | 0.06995  | 0.  | 2.52828   | 0.  |
| 25 |        |           | 207 |          | 185 |           | 202 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 9.89   | 1.23390   | 0.  | 0.03711  | 0.  | 1.27101   | 0.  |
| 24 |        |           | 211 |          | 181 |           | 205 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 10.47  | 0.66030   | 0.  | 0.02009  | 0.  | 0.68039   | 0.  |
| 23 |        |           | 215 |          | 191 |           | 209 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 11.05  | 0.33988   | 0.  | 0.01026  | 0.  | 0.35014   | 0.  |
| 22 |        |           | 225 |          | 200 |           | 218 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 11.63  | 0.18232   | 0.  | 0.00532  | 0.  | 0.18764   | 0.  |
| 21 |        |           | 236 |          | 202 |           | 229 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 12.25  | 0.08649   | 0.  | 0.00264  | 0.  | 0.08913   | 0.  |
| 61 |        |           | 230 |          | 211 |           | 224 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
|    |        |           |     |          |     |           |     |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 2.37   | 141.65500 | 0.  | 6.01589  | 0.  | 147.67088 | 0.  |
| 17 | (L)    |           | 388 |          | 377 |           | 373 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 2.37   | 702.02600 | 0.  | 21.04760 | 0.  | 723.07361 | 0.  |
| 57 | (R)    |           | 437 |          | 286 |           | 424 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 4.68   | 5.88512   | 0.  | 0.77114  | 0.  | 6.65626   | 0.  |
| 13 | (L)    |           | 496 |          | 349 |           | 440 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 4.68   | 122.58800 | 0.  | 3.39148  | 0.  | 125.97948 | 0.  |
| 53 | (R)    |           | 389 |          | 259 |           | 379 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.00   | 3.52392   | 0.  | 0.08299  | 0.  | 3.60691   | 0.  |
| 09 | (L)    |           | 579 |          | 522 |           | 565 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 7.00   | 11.84650  | 0.  | 0.37471  | 0.  | 12.22121  | 0.  |
| 49 | (R)    |           | 329 |          | 249 |           | 319 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.73   | 0.56617   | 0.  | 0.01596  | 0.  | 0.58213   | 0.  |
| 06 | (L)    |           | 590 |          | 487 |           | 574 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 8.73   | 2.20574   | 0.  | 0.07183  | 0.  | 2.27757   | 0.  |
| 46 | (R)    |           | 302 |          | 264 |           | 293 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 10     | 0.12999   | 0.  | 0.00297  | 0.  | 0.13296   | 0.  |
| 03 | .47(L) |           | 451 |          | 436 |           | 441 |
+----+--------+-----------+-----+----------+-----+-----------+-----+
| 2  | 10     | 0.35034   | 0.  | 0.01017  | 0.  | 0.36051   | 0.  |
| 43 | .47(R) |           | 280 |          | 259 |           | 272 |
+----+--------+-----------+-----+----------+-----+-----------+-----+

Table 21---Dose Equivalent Rates in between tunnel floor level and
shield bottom (tally segment B) in selected shield cells due to a 10
amp 100 MeV 20 off axis beam spill.

+----+--------+----------+-----+----------+------+----------+-----+
| ** | **Di   | **N      |     | **       |      | *        |     |
| Ce | stance | eutron** |     | Photon** |      | *Total** |     |
| ll | into   |          |     |          |      |          |     |
| ** | Shield |          |     |          |      |          |     |
|    | (f     |          |     |          |      |          |     |
|    | eet)** |          |     |          |      |          |     |
+----+--------+----------+-----+----------+------+----------+-----+
|    |        | **DER**  | **R | **DER    | **   | **DER**  | **R |
|    |        |          | E** | (mr      | RE** |          | E** |
|    |        | **(mr    |     | em/hr)** |      | **(mr    |     |
|    |        | em/hr)** |     |          |      | em/hr)** |     |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 1.79   | 73       | 0.  | 2        | 0    | 76       | 0.  |
| 38 |        | 87.31982 | 136 | 74.22702 | .097 | 61.54688 | 131 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 2.37   | 48       | 0.  | 1        | 0    | 49       | 0.  |
| 37 |        | 02.93018 | 145 | 55.06200 | .099 | 57.99219 | 141 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 3.53   | 16       | 0.  | 45.99120 | 0    | 16       | 0.  |
| 35 |        | 40.00000 | 183 |          | .134 | 85.99121 | 178 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 4.68   | 3        | 0.  | 13.74660 | 0    | 3        | 0.  |
| 33 |        | 62.43402 | 187 |          | .156 | 76.18063 | 180 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 5.84   | 1        | 0.  | 3.37775  | 0    | 1        | 0.  |
| 31 |        | 05.21700 | 188 |          | .157 | 08.59474 | 182 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 7.00   | 33.37060 | 0.  | 0.89742  | 0    | 34.26802 | 0.  |
| 29 |        |          | 202 |          | .169 |          | 197 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 7.58   | 16.60000 | 0.  | 0.48772  | 0    | 17.08772 | 0.  |
| 28 |        |          | 218 |          | .178 |          | 212 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 8.16   | 8.42734  | 0.  | 0.25867  | 0    | 8.68601  | 0.  |
| 27 |        |          | 216 |          | .180 |          | 210 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 8.73   | 4.55360  | 0.  | 0.13858  | 0    | 4.69218  | 0.  |
| 26 |        |          | 196 |          | .183 |          | 190 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 9.31   | 2.27254  | 0.  | 0.06899  | 0    | 2.34153  | 0.  |
| 25 |        |          | 199 |          | .176 |          | 193 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 9.89   | 1.22882  | 0.  | 0.03685  | 0    | 1.26567  | 0.  |
| 24 |        |          | 211 |          | .183 |          | 205 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 10.47  | 0.63113  | 0.  | 0.02041  | 0    | 0.65154  | 0.  |
| 23 |        |          | 213 |          | .190 |          | 207 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 11.05  | 0.33983  | 0.  | 0.00987  | 0    | 0.34970  | 0.  |
| 22 |        |          | 215 |          | .204 |          | 209 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 11.63  | 0.16681  | 0.  | 0.00513  | 0    | 0.17194  | 0.  |
| 21 |        |          | 218 |          | .189 |          | 211 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 12.25  | 0.08091  | 0.  | 0.00255  | 0    | 0.08346  | 0.  |
| 61 |        |          | 213 |          | .194 |          | 206 |
+----+--------+----------+-----+----------+------+----------+-----+
|    |        |          |     |          |      |          |     |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 2.37   | 1        | 0.  | 8.00375  | 0    | 1        | 0.  |
| 17 | (L)    | 28.12500 | 805 |          | .453 | 36.12875 | 758 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 2.37   | 11       | 0.  | 28.64730 | 0    | 11       | 0.  |
| 57 | (R)    | 34.13000 | 523 |          | .310 | 62.77734 | 510 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 4.68   | 33.15750 | 0.  | 1.87862  | 0    | 35.03612 | 0.  |
| 13 | (L)    |          | 452 |          | .358 |          | 429 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 4.68   | 50.36780 | 0.  | 2.84597  | 0    | 53.21377 | 0.  |
| 53 | (R)    |          | 353 |          | .329 |          | 334 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 7.00   | 6.72232  | 0.  | 0.21969  | 0    | 6.94201  | 0.  |
| 09 | (L)    |          | 515 |          | .368 |          | 499 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 7.00   | 5.51645  | 0.  | 0.22711  | 0    | 5.74356  | 0.  |
| 49 | (R)    |          | 420 |          | .261 |          | 404 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 8.73   | 1.27703  | 0.  | 0.04084  | 0    | 1.31787  | 0.  |
| 06 | (L)    |          | 442 |          | .387 |          | 429 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 8.73   | 2.05112  | 0.  | 0.05698  | 0    | 2.10810  | 0.  |
| 46 | (R)    |          | 650 |          | .366 |          | 633 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 10     | 0.19186  | 0.  | 0.00704  | 0    | 0.19890  | 0.  |
| 03 | .47(L) |          | 517 |          | .478 |          | 499 |
+----+--------+----------+-----+----------+------+----------+-----+
| 2  | 10     | 0.29114  | 0.  | 0.00921  | 0    | 0.30035  | 0.  |
| 43 | .47(R) |          | 624 |          | .488 |          | 605 |
+----+--------+----------+-----+----------+------+----------+-----+

Table 22---Dose Equivalent Rates between tunnel ceiling level and 1 foot
below the top of the lower shield (tally segment C) in selected shield
cells due to a 10 amp 100 MeV 20 off axis beam spill.

+-------+------------+------+----------+------+-------------+------+
| **C   | *          |      | **       |      | **Total**   |      |
| ell** | *Neutron** |      | Photon** |      |             |      |
+-------+------------+------+----------+------+-------------+------+
|       | **DER**    | **   | **DER    | **   | **DER**     | **   |
|       |            | RE** | (mr      | RE** |             | RE** |
|       | **(        |      | em/hr)** |      | **          |      |
|       | mrem/hr)** |      |          |      | (mrem/hr)** |      |
+-------+------------+------+----------+------+-------------+------+
| 8230  | 8.22440    | 0    | 0.26743  | 0    | 8.49183     | 0    |
|       |            | .212 |          | .173 |             | .205 |
+-------+------------+------+----------+------+-------------+------+
| 8229  | 4.66552    | 0    | 0.13841  | 0    | 4.80393     | 0    |
|       |            | .228 |          | .174 |             | .222 |
+-------+------------+------+----------+------+-------------+------+
| 8228  | 2.51312    | 0    | 0.07126  | 0    | 2.58438     | 0    |
|       |            | .228 |          | .183 |             | .222 |
+-------+------------+------+----------+------+-------------+------+
| 8227  | 1.40419    | 0    | 0.03875  | 0    | 1.44294     | 0    |
|       |            | .239 |          | .196 |             | .232 |
+-------+------------+------+----------+------+-------------+------+
| 8226  | 0.82247    | 0    | 0.02063  | 0    | 0.84309     | 0    |
|       |            | .238 |          | .196 |             | .232 |
+-------+------------+------+----------+------+-------------+------+
| 8224  | 0.24109    | 0    | 0.00628  | 0    | 0.24737     | 0    |
|       |            | .256 |          | .215 |             | .249 |
+-------+------------+------+----------+------+-------------+------+
| 8213  | 1.29375    | 0    | 0.11245  | 0    | 1.40620     | 0    |
|       |            | .454 |          | .399 |             | .419 |
+-------+------------+------+----------+------+-------------+------+
| 8212  | 1.34652    | 0    | 0.06322  | 0    | 1.40974     | 0    |
|       |            | .423 |          | .382 |             | .405 |
+-------+------------+------+----------+------+-------------+------+
| 8211  | 0.79562    | 0    | 0.04899  | 0    | 0.84461     | 0    |
|       |            | .366 |          | .307 |             | .346 |
+-------+------------+------+----------+------+-------------+------+
| 8210  | 0.52623    | 0    | 0.01991  | 0    | 0.54613     | 0    |
|       |            | .344 |          | .306 |             | .332 |
+-------+------------+------+----------+------+-------------+------+
| 8208  | 0.35612    | 0    | 0.01226  | 0    | 0.36838     | 0    |
|       |            | .318 |          | .286 |             | .308 |
+-------+------------+------+----------+------+-------------+------+
| 8250  | 2.22854    | 0    | 0.08236  | 0    | 2.31090     | 0    |
|       |            | .368 |          | .306 |             | .355 |
+-------+------------+------+----------+------+-------------+------+
| 8249  | 1.20733    | 0    | 0.04623  | 0    | 1.25356     | 0    |
|       |            | .332 |          | .294 |             | .320 |
+-------+------------+------+----------+------+-------------+------+
| 8248  | 0.75018    | 0    | 0.02019  | 0    | 0.77037     | 0    |
|       |            | .365 |          | .276 |             | .356 |
+-------+------------+------+----------+------+-------------+------+
| 8247  | 0.41686    | 0    | 0.01097  | 0    | 0.42782     | 0    |
|       |            | .320 |          | .261 |             | .312 |
+-------+------------+------+----------+------+-------------+------+
| 8246  | 0.23836    | 0    | 0.00653  | 0    | 0.24489     | 0    |
|       |            | .281 |          | .248 |             | .274 |
+-------+------------+------+----------+------+-------------+------+
| 8244  | 0.08394    | 0    | 0.00233  | 0    | 0.08626     | 0    |
|       |            | .339 |          | .275 |             | .330 |
+-------+------------+------+----------+------+-------------+------+

Table 23---Dose Equivalent Rates in selected cells in the upper 6.86
inches of the lower shield (tally segment D) due to a 10 amp 100 MeV
20 off axis beam spill.

![](media/image14.wmf){width="5.999305555555556in"
height="5.152083333333334in"}

Figure 12---Cut through the upper layer of the lower shield showing the
cells (red) in which tallies were taken and the total DER (blue) in
those cells due to a 10 amp 100 MeV beam spill. The dashed green line
is the position of the middle shield surface.

+-------+------------+------+----------+------+-------------+------+
| **C   | *          |      | **       |      | **Total**   |      |
| ell** | *Neutron** |      | Photon** |      |             |      |
+-------+------------+------+----------+------+-------------+------+
|       | **DER**    | **   | **DER    | **   | **DER**     | **   |
|       |            | RE** | (mr      | RE** |             | RE** |
|       | **(        |      | em/hr)** |      | **          |      |
|       | mrem/hr)** |      |          |      | (mrem/hr)** |      |
+-------+------------+------+----------+------+-------------+------+
| 300   | 0.61646    | 0    | 0.01911  | 0    | 0.63557     | 0    |
|       |            | .380 |          | .348 |             | .380 |
+-------+------------+------+----------+------+-------------+------+
| 301   | 0.33647    | 0    | 0.01328  | 0    | 0.34975     | 0    |
|       |            | .401 |          | .341 |             | .386 |
+-------+------------+------+----------+------+-------------+------+
| 302   | 0.39662    | 0    | 0.01376  | 0    | 0.41038     | 0    |
|       |            | .447 |          | .367 |             | .432 |
+-------+------------+------+----------+------+-------------+------+
| 305   | 0.98863    | 0    | 0.05443  | 0    | 1.04306     | 0    |
|       |            | .625 |          | .428 |             | .625 |
+-------+------------+------+----------+------+-------------+------+
| 307   | 0.31794    | 0    | 0.02014  | 0    | 0.33808     | 0    |
|       |            | .954 |          | .416 |             | .954 |
+-------+------------+------+----------+------+-------------+------+
| 310   | 1.08391    | 0    | 0.02863  | 0    | 1.11254     | 0    |
|       |            | .228 |          | .198 |             | .222 |
+-------+------------+------+----------+------+-------------+------+
| 311   | 1.83730    | 0    | 0.05309  | 0    | 1.89039     | 0    |
|       |            | .208 |          | .185 |             | .202 |
+-------+------------+------+----------+------+-------------+------+
| 321   | 0.51771    | 0    | 0.01669  | 0    | 0.53440     | 0    |
|       |            | .364 |          | .331 |             | .352 |
+-------+------------+------+----------+------+-------------+------+
| 320   | 0.24900    | 0    | 0.00860  | 0    | 0.25760     | 0    |
|       |            | .339 |          | .323 |             | .328 |
+-------+------------+------+----------+------+-------------+------+
| 312   | 2.57405    | 0    | 0.08474  | 0    | 2.65879     | 0    |
|       |            | .192 |          | .172 |             | .186 |
+-------+------------+------+----------+------+-------------+------+
| 322   | 0.98064    | 0    | 0.02946  | 0    | 1.01009     | 0    |
|       |            | .340 |          | .305 |             | .331 |
+-------+------------+------+----------+------+-------------+------+
| 316   | 9.86515    | 0    | 0.35011  | 0    | 10.21526    | 0    |
|       |            | .208 |          | .183 |             | .201 |
+-------+------------+------+----------+------+-------------+------+
| 326   | 3.75090    | 0    | 0.18012  | 0    | 3.93102     | 0    |
|       |            | .373 |          | .315 |             | .356 |
+-------+------------+------+----------+------+-------------+------+
| 319   | 15.64020   | 0    | 0.75239  | 0    | 16.39259    | 0    |
|       |            | .305 |          | .264 |             | .305 |
+-------+------------+------+----------+------+-------------+------+
| 329   | 4.66611    | 0    | 0.28139  | 0    | 4.94750     | 0    |
|       |            | .591 |          | .372 |             | .558 |
+-------+------------+------+----------+------+-------------+------+

Table 24---Dose Equivalent Rates in selected cells in the middle shield
due to a 10 amp 100 MeV 20 off axis beam spill.

![](media/image15.wmf){width="5.688888888888889in"
height="4.590972222222222in"}

Figure 13---Cut through the middle shield showing cells (red) in which
and surfaces (magenta) on which tallies were taken. The blue numbers are
the total DER in the tallied cells due to a 10 amp 100 MeV beam spill.
Dimensions describing the duct cut out are in green, and the outline of
the lower shield below is shown in gold.

![](media/image16.wmf){width="5.996527777777778in"
height="3.1847222222222222in"}

Figure 14---Cut through the upper shield showing cells in which and
surfaces on which tallies were taken.

+-------+------------+------+----------+------+-------------+------+
| **C   | *          |      | **       |      | **Total**   |      |
| ell** | *Neutron** |      | Photon** |      |             |      |
+-------+------------+------+----------+------+-------------+------+
|       | **DER**    | **   | **DER    | **   | **DER**     | **   |
|       |            | RE** | (mr      | RE** |             | RE** |
|       | **(        |      | em/hr)** |      | **          |      |
|       | mrem/hr)** |      |          |      | (mrem/hr)** |      |
+-------+------------+------+----------+------+-------------+------+
| 330   | 0.00000    | 0    | 0.00003  | 1    | 0.00003     | 1    |
|       |            | .000 |          | .000 |             | .000 |
+-------+------------+------+----------+------+-------------+------+
| 340   | 0.00374    | 0    | 0.00011  | 0    | 0.00385     | 0    |
|       |            | .618 |          | .319 |             | .600 |
+-------+------------+------+----------+------+-------------+------+
| 350   | 0.00268    | 0    | 0.00003  | 0    | 0.00271     | 0    |
|       |            | .767 |          | .491 |             | .759 |
+-------+------------+------+----------+------+-------------+------+
| 342   | 0.01253    | 0    | 0.00056  | 0    | 0.01310     | 0    |
|       |            | .306 |          | .269 |             | .293 |
+-------+------------+------+----------+------+-------------+------+
| 344   | 0.01242    | 0    | 0.00104  | 0    | 0.01345     | 0    |
|       |            | .538 |          | .372 |             | .497 |
+-------+------------+------+----------+------+-------------+------+
| 346   | 0.05329    | 0    | 0.00166  | 0    | 0.05495     | 0    |
|       |            | .487 |          | .427 |             | .472 |
+-------+------------+------+----------+------+-------------+------+
| 349   | 0.30476    | 0    | 0.01796  | 0    | 0.32272     | 0    |
|       |            | .766 |          | .707 |             | .725 |
+-------+------------+------+----------+------+-------------+------+

Table 25---Dose Equivalent Rates in selected cells in the upper shield
due to a 10 amp 100 MeV 20 off axis beam spill.

+------------------+---------+-----+---------+-----+---------+-----+
| **Surface**      | **Ne    |     | **P     |     | **      |     |
|                  | utron** |     | hoton** |     | Total** |     |
+------------------+---------+-----+---------+-----+---------+-----+
|                  | **DER** | **R | **DER   | **R | **DER** | **R |
|                  |         | E** | (mre    | E** |         | E** |
|                  | **(mre  |     | m/hr)** |     | **(mre  |     |
|                  | m/hr)** |     |         |     | m/hr)** |     |
+------------------+---------+-----+---------+-----+---------+-----+
| X                | 0.00132 | 0.  | 0.00005 | 0.  | 0.00138 | 0.  |
|                  |         | 399 |         | 324 |         | 384 |
| Upper Shield     |         |     |         |     |         |     |
| Face             |         |     |         |     |         |     |
+------------------+---------+-----+---------+-----+---------+-----+
| Z                | 0.49793 | 0.  | 0.01309 | 0.  | 0.51102 | 0.  |
|                  |         | 228 |         | 200 |         | 222 |
| Lower Shield     |         |     |         |     |         |     |
| Face             |         |     |         |     |         |     |
+------------------+---------+-----+---------+-----+---------+-----+
| Y                | 0.15231 | 0.  | 0.00473 | 0.  | 0.15705 | 0.  |
|                  |         | 274 |         | 236 |         | 266 |
| Lower Shield     |         |     |         |     |         |     |
| Cutout           |         |     |         |     |         |     |
+------------------+---------+-----+---------+-----+---------+-----+

Table 26---Dose Equivalent Rates on outer surfaces of the middle and
upper shields due to a 10 amp 100 MeV 20 off axis beam spill.

## Shield Wall Penetration---On Axis Spill

A second beam spill in the 100 MeV region was modeled by the beam
impinging on a stainless steel plug in the beam line. The plug spans the
full diameter of the beam tube and is two inches thick. The upstream
face of the plug at the beam tube center is equidistant between the
planes of the stubout walls. A pencil beam of 100 MeV protons struck the
center of the plug. The spill and shield penetration were calculated in
a single run without intervening surface source read and write. The
shield model is the same as described above for the 20° spill. The
remainder of the model is as shown in Figure 1 with the following
exceptions: The concrete piers were not included, the model was
terminated at the downstream surface of the shield, the left dimension
of 42.5' changes to 8.9', and the right dimension of 71.6' changes to
19.12'. External tuff was included from the levels of the shield top to
shield bottom.

Table 27 shows the results, scaled to a 10 amp current, through the
center section of the shield between the tunnel floor and ceiling. The
right-hand column is the ratio of the total DER for this spill to that
for the 100 MeV 20 off axis beam spill. The DERs for this spill are
lower, by as much as a factor of 0.2 at the upstream face of the shield.
The results in other volumes of the shield and in the middle and upper
shields are similar.

+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| **  | **        |     | * |          |      | **Total** |     | **R   |
| Cel | Neutron** |     | * |          |      |           |     | atio: |
| l** |           |     | P |          |      |           |     | Table |
|     |           |     | h |          |      |           |     | 20**  |
|     |           |     | o |          |      |           |     |       |
|     |           |     | t |          |      |           |     |       |
|     |           |     | o |          |      |           |     |       |
|     |           |     | n |          |      |           |     |       |
|     |           |     | * |          |      |           |     |       |
|     |           |     | * |          |      |           |     |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
|     | **DER**   | **R | * |          | **   | **DER**   | **R |       |
|     |           | E** | * |          | RE** |           | E** |       |
|     | **(m      |     | D |          |      | **(m      |     |       |
|     | rem/hr)** |     | E |          |      | rem/hr)** |     |       |
|     |           |     | R |          |      |           |     |       |
|     |           |     | ( |          |      |           |     |       |
|     |           |     | m |          |      |           |     |       |
|     |           |     | r |          |      |           |     |       |
|     |           |     | e |          |      |           |     |       |
|     |           |     | m |          |      |           |     |       |
|     |           |     | / |          |      |           |     |       |
|     |           |     | h |          |      |           |     |       |
|     |           |     | r |          |      |           |     |       |
|     |           |     | ) |          |      |           |     |       |
|     |           |     | * |          |      |           |     |       |
|     |           |     | * |          |      |           |     |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 238 | 33        | 0.  |   | 16       | 0    | 35        | 0.  | 0.764 |
|     | 758.79688 | 016 |   | 08.48999 | .010 | 367.28516 | 015 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 237 | 14        | 0.  |   | 7        | 0    | 15        | 0.  | 0.658 |
|     | 624.39941 | 021 |   | 06.12500 | .012 | 330.52441 | 020 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 235 | 2         | 0.  |   | 1        | 0    | 3         | 0.  | 0.520 |
|     | 939.31006 | 031 |   | 31.26500 | .019 | 070.57495 | 030 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 233 | 662.24298 | 0.  |   | 26.67110 | 0    | 688.91406 | 0.  | 0.454 |
|     |           | 042 |   |          | .028 |           | 041 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 231 | 159.44701 | 0.  |   | 5.76628  | 0    | 165.21329 | 0.  | 0.401 |
|     |           | 056 |   |          | .040 |           | 054 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 229 | 38.50370  | 0.  |   | 1.35106  | 0    | 39.85476  | 0.  | 0.350 |
|     |           | 070 |   |          | .054 |           | 068 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 228 | 19.12440  | 0.  |   | 0.66665  | 0    | 19.79104  | 0.  | 0.328 |
|     |           | 075 |   |          | .062 |           | 072 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 227 | 9.29796   | 0.  |   | 0.32204  | 0    | 9.62000   | 0.  | 0.301 |
|     |           | 083 |   |          | .067 |           | 080 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 226 | 4.55473   | 0.  |   | 0.15646  | 0    | 4.71119   | 0.  | 0.276 |
|     |           | 089 |   |          | .073 |           | 086 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 225 | 2.23230   | 0.  |   | 0.07658  | 0    | 2.30888   | 0.  | 0.258 |
|     |           | 097 |   |          | .082 |           | 094 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 224 | 1.10469   | 0.  |   | 0.03752  | 0    | 1.14221   | 0.  | 0.244 |
|     |           | 103 |   |          | .090 |           | 100 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 223 | 0.54200   | 0.  |   | 0.01847  | 0    | 0.56047   | 0.  | 0.224 |
|     |           | 113 |   |          | .097 |           | 109 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 222 | 0.26573   | 0.  |   | 0.00912  | 0    | 0.27485   | 0.  | 0.210 |
|     |           | 128 |   |          | .106 |           | 124 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 221 | 0.13541   | 0.  |   | 0.00441  | 0    | 0.13982   | 0.  | 0.199 |
|     |           | 141 |   |          | .116 |           | 136 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+
| 261 | 0.06047   | 0.  |   | 0.00189  | 0    | 0.06236   | 0.  | 0.189 |
|     |           | 151 |   |          | .126 |           | 146 |       |
+-----+-----------+-----+---+----------+------+-----------+-----+-------+

Table 27---Dose Equivalent Rates between tunnel floor and ceiling levels
(tally segment A) in selected shield cells due to a 10 amp 100 MeV on
axis beam spill.

The lower DERs result from a smaller high-energy neutron flux at the
downstream shield face. The ratio of neutron fluxes in the 100 MeV 20
off axis beam spill to the fluxes in this model increases from 1.1 at
0.01 MeV to 1.3 at 40 MeV and then to 11 at 95 MeV. The fluxes are
nearly equal below 0.01 MeV.

# Operation Phase---Beam Spill on RSS Beam Plug

Once completed, personnel access to the IPF tunnel can be permitted when
the LANSCE main beam is on if the Radiation Safety System (RSS) beam
plug is in place and if the dose within the IPF tunnel resulting from a
beam spill on the RSS plug does not result in large doses in the tunnel.
To assess the DER from such a spill, we constructed an RSS model as
shown in Figure 15, Figure 16, and Figure 17. The model includes a
section of the LANSCE main tunnel, the shield wall with penetrations, a
foot-long section of the IPF tunnel, and a section of the IPF branch
beam line and RSS plug. The main beam line is not included.

The beam line is a 4 inch OD cylinder with wall thickness 0.065 inches.
The interior is vacuum upstream of the plug, and air downstream of the
plug through the shield. In most operational scenarios, the interior
will be vacuum for the entire length of the beam line; our substitution
of air for the vacuum should not increase the DERs significantly. The
solid copper plug is 4.5 inches OD coaxial with the beam line and 20
inches long. The downstream face of the plug is coincident with the
upstream face of the shield wall.

In addition to the beam tube, the shield wall is penetrated by 18 4 inch
diameter utility ducts filled with air. The ducts contain two 45 bends
to prevent direct shine of radiation.

We directed a 100 MeV proton pencil beam, located at the center of the
beam tube, onto the RSS plug. We used particle tracks to verify correct
placement of the beam. We assume a current of 500 amp and give the
results in rem/hour.

Table 28 gives the DERs in several positions in the IPF tunnel. The DER
in the lower volume opposite the beam line is larger than in the upper
volume opposite the ducts. We also made tallies through the beam line
and through two of the ducts. Duct 1 was chosen because it is closest to
the beam line, duct 18 because it is furthest away. Table 29, Table 30,
and Table 31 give the tallies in the beam line, duct 1, and duct 18,
respectively. Figure 18 plots the total DER, together with the neutron
and photon contributions, as a function of depth into the shield for the
beam line and duct 1.

+------------------+---------+-----+---------+-----+---------+-----+
| **Cell**         | **Ne    |     | **P     |     | **      |     |
|                  | utron** |     | hoton** |     | Total** |     |
+------------------+---------+-----+---------+-----+---------+-----+
|                  | **DER** | **R | **DER   | **R | **DER** | **R |
|                  |         | E** | (re     | E** |         | E** |
|                  | **(re   |     | m/hr)** |     | **(re   |     |
|                  | m/hr)** |     |         |     | m/hr)** |     |
+------------------+---------+-----+---------+-----+---------+-----+
| 20 Shield Recess | 0.03378 | 0.  | 0.00084 | 0.  | 0.03461 | 0.  |
|                  |         | 090 |         | 077 |         | 087 |
+------------------+---------+-----+---------+-----+---------+-----+
| 14 Lower         | 0.02788 | 0.  | 0.00067 | 0.  | 0.02855 | 0.  |
|                  |         | 101 |         | 091 |         | 099 |
+------------------+---------+-----+---------+-----+---------+-----+
| 15 Upper         | 0.00554 | 0.  | 0.00013 | 0.  | 0.00567 | 0.  |
|                  |         | 060 |         | 051 |         | 058 |
+------------------+---------+-----+---------+-----+---------+-----+

Table 28---Dose Equivalent Rates in air volumes downstream of the shield
due to a spill on the RSS beam plug.

![](media/image17.wmf){width="4.218055555555556in"
height="8.599305555555556in"}

Figure 15---Floor plan of the RSS beam spill model.

![](media/image18.wmf){width="6.079166666666667in"
height="6.852083333333334in"}

Figure 16---Vertical cut through the shield wall in the RSS beam spill
model showing the beam line, RSS beam plug, utility ducts, and air
volumes downstream of the shield in which tallies were taken.

![](media/image19.wmf){width="5.43125in" height="8.223611111111111in"}

Figure 17---The upstream face of the shield showing the beam and utility
duct penetrations. The middle box represents the tunnel walls, floor,
and ceiling.

+--------+------------+------+----------+------+-------------+------+
| **Di   | *          |      | **       |      | **Total**   |      |
| stance | *Neutron** |      | Photon** |      |             |      |
| into   |            |      |          |      |             |      |
| Shield |            |      |          |      |             |      |
| (f     |            |      |          |      |             |      |
| eet)** |            |      |          |      |             |      |
+--------+------------+------+----------+------+-------------+------+
|        | **DER**    | **   | **DER    | **   | **DER**     | **   |
|        |            | RE** | (r       | RE** |             | RE** |
|        | **         |      | em/hr)** |      | *           |      |
|        | (rem/hr)** |      |          |      | *(rem/hr)** |      |
+--------+------------+------+----------+------+-------------+------+
| 0.38   | 33         | 0    | 85       | 0    | 3           | 0    |
|        | 6491.00000 | .027 | 67.79980 | .027 | 45058.81250 | .026 |
+--------+------------+------+----------+------+-------------+------+
| 1.79   | 8          | 0    | 36       | 0    | 89168.71875 | 0    |
|        | 5518.89844 | .041 | 49.82007 | .027 |             | .039 |
+--------+------------+------+----------+------+-------------+------+
| 2.95   | 1          | 0    | 8        | 0    | 20644.12500 | 0    |
|        | 9772.69922 | .079 | 71.42499 | .035 |             | .076 |
+--------+------------+------+----------+------+-------------+------+
| 4.10   | 5164.00000 | 0    | 1        | 0    | 5360.99707  | 0    |
|        |            | .088 | 96.99699 | .062 |             | .085 |
+--------+------------+------+----------+------+-------------+------+
| 5.26   | 1388.63000 | 0    | 53.83270 | 0    | 1442.46265  | 0    |
|        |            | .178 |          | .185 |             | .172 |
+--------+------------+------+----------+------+-------------+------+
| 6.42   | 316.23099  | 0    | 11.01260 | 0    | 327.24359   | 0    |
|        |            | .118 |          | .084 |             | .114 |
+--------+------------+------+----------+------+-------------+------+
| 7.58   | 87.55380   | 0    | 3.02916  | 0    | 90.58296    | 0    |
|        |            | .136 |          | .100 |             | .132 |
+--------+------------+------+----------+------+-------------+------+
| 8.73   | 23.28090   | 0    | 1.08462  | 0    | 24.36552    | 0    |
|        |            | .176 |          | .219 |             | .168 |
+--------+------------+------+----------+------+-------------+------+
| 9.89   | 9.81087    | 0    | 0.74802  | 0    | 10.55889    | 0    |
|        |            | .326 |          | .354 |             | .304 |
+--------+------------+------+----------+------+-------------+------+
| 10.47  | 7.04965    | 0    | 0.27855  | 0    | 7.32820     | 0    |
|        |            | .444 |          | .426 |             | .428 |
+--------+------------+------+----------+------+-------------+------+
| 11.05  | 4.31898    | 0    | 0.12766  | 0    | 4.44664     | 0    |
|        |            | .522 |          | .438 |             | .507 |
+--------+------------+------+----------+------+-------------+------+
| 11.96  | 3.04762    | 0    | 0.07775  | 0    | 3.12537     | 0    |
|        |            | .701 |          | .682 |             | .684 |
+--------+------------+------+----------+------+-------------+------+

Table 29---Dose Equivalent Rates in the beam tube through the shield due
to a spill on the RSS beam plug.

+--------+-----------+------+----------+------+-------------+------+
| **Di   | **        |      | **       |      | **Total**   |      |
| stance | Neutron** |      | Photon** |      |             |      |
| into   |           |      |          |      |             |      |
| Shield |           |      |          |      |             |      |
| (f     |           |      |          |      |             |      |
| eet)** |           |      |          |      |             |      |
+--------+-----------+------+----------+------+-------------+------+
|        | **DER**   | **   | **DER    | **   | **DER**     | **   |
|        |           | RE** | (r       | RE** |             | RE** |
|        | **(       |      | em/hr)** |      | *           |      |
|        | rem/hr)** |      |          |      | *(rem/hr)** |      |
+--------+-----------+------+----------+------+-------------+------+
| 0.38   | 68        | 0    | 17       | 0    | 69871.79688 | 0    |
|        | 137.89844 | .059 | 33.90002 | .056 |             | .058 |
+--------+-----------+------+----------+------+-------------+------+
| 1.13   | 11        | 0    | 8        | 0    | 12770.91699 | 0    |
|        | 905.00000 | .090 | 65.91699 | .061 |             | .084 |
+--------+-----------+------+----------+------+-------------+------+
| 1.79   | 3         | 0    | 3        | 0    | 3744.97021  | 0    |
|        | 390.12012 | .137 | 54.85001 | .082 |             | .124 |
+--------+-----------+------+----------+------+-------------+------+
| 2.37   | 1         | 0    | 1        | 0    | 1277.22400  | 0    |
|        | 093.26001 | .136 | 83.96400 | .098 |             | .117 |
+--------+-----------+------+----------+------+-------------+------+
| 2.95   | 434.57401 | 0    | 81.07970 | 0    | 515.65369   | 0    |
|        |           | .153 |          | .132 |             | .130 |
+--------+-----------+------+----------+------+-------------+------+
| 3.53   | 170.80299 | 0    | 36.74250 | 0    | 207.54550   | 0    |
|        |           | .158 |          | .179 |             | .134 |
+--------+-----------+------+----------+------+-------------+------+
| 4.10   | 126.60200 | 0    | 16.34040 | 0    | 142.94240   | 0    |
|        |           | .226 |          | .157 |             | .201 |
+--------+-----------+------+----------+------+-------------+------+
| 4.68   | 53.89640  | 0    | 7.13070  | 0    | 61.02710    | 0    |
|        |           | .217 |          | .159 |             | .193 |
+--------+-----------+------+----------+------+-------------+------+
| 8.73   | 3.37653   | 0    | 0.10446  | 0    | 3.48098     | 0    |
|        |           | .130 |          | .102 |             | .126 |
+--------+-----------+------+----------+------+-------------+------+
| 9.31   | 1.99927   | 0    | 0.06047  | 0    | 2.05974     | 0    |
|        |           | .118 |          | .101 |             | .115 |
+--------+-----------+------+----------+------+-------------+------+
| 9.89   | 0.97404   | 0    | 0.03438  | 0    | 1.00842     | 0    |
|        |           | .113 |          | .101 |             | .109 |
+--------+-----------+------+----------+------+-------------+------+
| 10.47  | 0.48524   | 0    | 0.01799  | 0    | 0.50323     | 0    |
|        |           | .115 |          | .085 |             | .111 |
+--------+-----------+------+----------+------+-------------+------+
| 11.05  | 0.25831   | 0    | 0.00896  | 0    | 0.26727     | 0    |
|        |           | .109 |          | .110 |             | .105 |
+--------+-----------+------+----------+------+-------------+------+
| 12.59  | 0.06696   | 0    | 0.00221  | 0    | 0.06917     | 0    |
|        |           | .115 |          | .078 |             | .111 |
+--------+-----------+------+----------+------+-------------+------+

Table 30---Dose Equivalent Rates through utility duct 1 due to a spill
on the RSS beam plug.

![](media/image20.wmf){width="5.999305555555556in"
height="4.527777777777778in"}

Figure 18---Total dose equivalent rate, along with the neutron and
photon components, as a function of the distance from the upstream
shield face, in the beam line and utility duct 1.

+--------+------------+------+----------+------+-------------+------+
| **Di   | *          |      | **       |      | **Total**   |      |
| stance | *Neutron** |      | Photon** |      |             |      |
| into   |            |      |          |      |             |      |
| Shield |            |      |          |      |             |      |
| (f     |            |      |          |      |             |      |
| eet)** |            |      |          |      |             |      |
+--------+------------+------+----------+------+-------------+------+
|        | **DER**    | **   | **DER    | **   | **DER**     | **   |
|        |            | RE** | (mr      | RE** |             | RE** |
|        | **(        |      | em/hr)** |      | **          |      |
|        | mrem/hr)** |      |          |      | (mrem/hr)** |      |
+--------+------------+------+----------+------+-------------+------+
| 0.38   | 4          | 0    | 13       | 0    | 43605.07031 | 0    |
|        | 2268.10156 | .065 | 36.96997 | .066 |             | .063 |
+--------+------------+------+----------+------+-------------+------+
| 1.13   | 8118.45996 | 0    | 6        | 0    | 8739.87305  | 0    |
|        |            | .105 | 21.41302 | .073 |             | .097 |
+--------+------------+------+----------+------+-------------+------+
| 1.79   | 2325.00000 | 0    | 2        | 0    | 2553.00098  | 0    |
|        |            | .128 | 28.00101 | .089 |             | .116 |
+--------+------------+------+----------+------+-------------+------+
| 2.37   | 763.13397  | 0    | 1        | 0    | 880.17096   | 0    |
|        |            | .195 | 17.03700 | .099 |             | .169 |
+--------+------------+------+----------+------+-------------+------+
| 2.95   | 247.36400  | 0    | 40.69220 | 0    | 288.05621   | 0    |
|        |            | .203 |          | .119 |             | .175 |
+--------+------------+------+----------+------+-------------+------+
| 3.53   | 96.78970   | 0    | 19.31830 | 0    | 116.10800   | 0    |
|        |            | .314 |          | .156 |             | .263 |
+--------+------------+------+----------+------+-------------+------+
| 4.10   | 27.60450   | 0    | 8.49309  | 0    | 36.09759    | 0    |
|        |            | .308 |          | .163 |             | .238 |
+--------+------------+------+----------+------+-------------+------+
| 4.68   | 11.47510   | 0    | 3.63528  | 0    | 15.11038    | 0    |
|        |            | .275 |          | .269 |             | .218 |
+--------+------------+------+----------+------+-------------+------+
| 8.73   | 0.12879    | 0    | 0.00528  | 0    | 0.13407     | 0    |
|        |            | .198 |          | .280 |             | .190 |
+--------+------------+------+----------+------+-------------+------+
| 9.31   | 0.35488    | 0    | 0.01722  | 0    | 0.37211     | 0    |
|        |            | .214 |          | .165 |             | .204 |
+--------+------------+------+----------+------+-------------+------+
| 9.89   | 0.22771    | 0    | 0.00929  | 0    | 0.23700     | 0    |
|        |            | .159 |          | .199 |             | .153 |
+--------+------------+------+----------+------+-------------+------+
| 10.47  | 0.12879    | 0    | 0.00528  | 0    | 0.13407     | 0    |
|        |            | .198 |          | .280 |             | .190 |
+--------+------------+------+----------+------+-------------+------+
| 11.05  | 0.04617    | 0    | 0.00420  | 0    | 0.05037     | 0    |
|        |            | .168 |          | .335 |             | .156 |
+--------+------------+------+----------+------+-------------+------+
| 12.59  | 0.01781    | 0    | 0.00084  | 0    | 0.01865     | 0    |
|        |            | .147 |          | .157 |             | .140 |
+--------+------------+------+----------+------+-------------+------+

Table 31---Dose Equivalent Rates through utility duct 18 due to a spill
on the RSS beam plug.

[^1]: NCRP Scientific Committee 4 on Heavy Particles ,k H. H. Rossi,
    chairman, *Protection against neutron radiation*, NCRP-38, National
    Council on Radiation Protection and Measurements (January 1971).