# Release of Radionuclides to Water and Transport to an Exposure Location

This chapter summarizes the Phase III work to estimate the release of
radionuclides from the Savannah River Site (SRS) facilities to surface
water and their transport by water to locations where hypothetical
receptors could be exposed. This work resulted in estimates of the
annual concentrations of twenty-two radionuclides at two exposure
locations: one in the Savannah River and one in Lower Three Runs Creek.
[Appendix B](../Appendix_B_ready%20for%20CDC%20031405.doc) lists these
annual estimated radionuclide concentrations. This analysis provides the
starting point for estimating dose resulting from liquid releases of
radionuclides from the SRS. The concentrations of radionuclides in water
developed by the methods discussed here are used as input to aquatic
food chain transport modeling described in [Chapter
8](../Chapter_08_ready%20for%20CDC%20031405.doc), and external and
internal exposure models discussed in [Chapter
9](../Chapter_09_ready%20for%20CDC%20031405.doc).[^1]

## Overview of the Problem and Solution

The required end points for considering water releases of radionuclides
from SRS facilities are the annual concentrations produced by those
releases at locations where receptors might be exposed. These annual
concentrations depended on three factors: (1) the exposure locations;
(2) the annual radionuclide releases to water from the SRS facilities;
and (3) the physical and chemical processes affecting the migration of
the radionuclides from the points of release to the exposure locations.

In order to estimate doses from radionuclide releases to water, the
GENII[^2] code allows the user the flexibility to: (1) specify
radionuclide releases to water and the water flow rate for the receiving
body of water or (2) specify the radionuclide concentrations. The second
option was selected for this study because, as discussed in the
following, the estimation of radionuclide concentrations is too complex
to perform except external to the GENII code.

### Exposure Locations

The scenarios ([Chapter
3](../Chapter_03_ready%20for%20CDC%20031405.doc)) outline exposure to
radionuclides through various activities, including fishing, hunting,
and boating in the SRS vicinity. In order to assess dose from these
exposures, it is essential to know the concentrations of radionuclides
at the exposure locations. The two locations chosen to represent
exposure to water releases from the SRS are:

-   The Savannah River below the point of confluence with Lower Three
    Runs Creek and

-   Lower Three Runs Creek at Martin, S.C.

These locations are shown in Figure 7-1.

For this study, the radionuclide concentrations in surface waters are
considered to be dependent on liquid releases of radionuclides from SRS
facilities to on-site streams and seepage basins. In fact, some
radionuclide concentrations in surface waters may have resulted from the
deposition of air borne radionuclides onto the surface waters or the
land surfaces they drained. These concentrations (and the doses that
result from them) are expected to be small compared to the
concentrations induced by water releases from SRS facilities.
Consequently, exposures of receptors to bodies of water not
hydrologically downstream of the SRS were assumed to have negligible
radionuclide concentrations and were not modeled.

![](media/image1.wmf){width="5.874305555555556in"
height="4.770833333333333in"}

Figure 7‑1 Major SRS Sources of Release to Surface Water

### Sources of Release to SRS Surface Waters

Figure 7-1 depicts the major facilities releasing radionuclides to
surface water bodies on the SRS site:

-   The C-, P-, K-, L-, and R-Reactor areas

-   The H- and F-Separations areas

-   The A-Area

-   The M-Area

-   The D-Area and CMS-TNX

-   The Central Shops (CS) Area

The reactor areas were the sources of most radionuclides released to
surface water. Releases from the reactor and separations areas included
radionuclides discharged directly to onsite streams as well as
radionuclides discharged into seepage basins located in reactor and
separations areas. Radionuclides released into seepage basins could leak
to underlying sediments and then be carried by groundwater to onsite
streams. Surface water releases of radionuclides were highest in the
early to middle 1960s and decreased into the 1980s.

### Migration of Radionuclides in SRS Surface Waters

As shown in Figure 7-1, there are five major onsite streams that
received radionuclides from SRS facilities. Waters from Upper Three Runs
Creek, Fourmile Branch, Pen Branch, and Steel Creek pass through a
low-lying wetland area adjacent to the Savannah River and the SRS, the
Savannah River Swamp, before they discharge into the Savannah River.
Water from Lower Three Runs Creek does not pass through the swamp.
Figure 7-1 also shows Road A which passes through the SRS from the
southeast to the northwest. Road A is significant because environmental
monitoring stations are located where Road A crosses these five SRS
streams. These Road A monitoring stations are the final points on the
SRS site of routine stream monitoring before discharge of the stream
water to the Savannah River.

Figure 7-1 illustrates some of the geographic features of the SRS that
require consideration while deriving radionuclide concentrations for
human contact from surface water. For example:

-   Releases to surface water were channeled by way of drainage to one
    or more of the streams that flowed into the Savannah River. Because
    of this, radiation exposures could only occur in well-defined
    geographic locations -- i.e., at accessible locations below site
    discharge points in the Savannah River or along Lower Three Runs
    Creek.

-   Each stream flowing offsite contained the contribution of more than
    one SRS facility or Area.

-   Much liquid effluent was discharged over the years to seepage basins
    rather than directly to onsite streams. A portion of the
    radionuclides was eliminated by radioactive decay, which was a major
    purpose of the seepage basins. Some portion of the volatile and
    gaseous radionuclides discharged into seepage basins entered the
    atmosphere, essentially becoming part of the air source term. A
    portion of the radionuclides in the seepage basins seeped into the
    soil and entered the groundwater system. Some of this material then
    seeped into surface streams, where their transportation
    characteristics were affected by other processes, such as sorption
    on sediments or migration.

-   Some of the radionuclides discharged to onsite streams were not
    immediately transported to locations where the radionuclides could
    have been contacted by members of the public. (Except for Lower
    Three Runs Creek, it was assumed that contamination in SRS streams
    was not accessible by members of the public.) Streams containing
    radionuclides had to flow for several miles before being discharged
    to the Savannah River. Through this process many radionuclides may
    have been sorbed onto stream and swamp sediments, reducing the
    inventory eventually released offsite.

-   All but one of the major onsite streams discharging radionuclides to
    the Savannah River passed through the Savannah River Swamp. Because
    of sedimentation processes characteristic of wetlands, radionuclides
    were likely deposited into swamp sediments. The swamp, however,
    historically flooded about 20% of the time. Flooding would tend to
    re-suspend contaminated sediments and re-dissolve sorbed
    radionuclides; in this way radionuclides released at earlier times
    could increase radionuclide content in the Savannah River above that
    attributed to the site radionuclide releases during a given year.

### Summary of Approaches to Estimating Concentrations

Because of these considerations, annual radionuclide concentrations in
water at the two exposure locations specified by the Phase III scenarios
were estimated by modeling performed outside the GENII computer code.
These concentration estimates needed to reflect the complex processes
governing radionuclide migration from the release facility to the
exposure location; these processes include radioactive decay, surface
water transport, sorption on sediments, groundwater transport, sorption
on soil, and uptake by biota

Different approaches were used in developing concentration estimates for
the Savannah River exposure location and the Lower Three Runs Creek
exposure location, because the physical situations for release and
transport to these exposure locations were different and the information
available to make estimates was different.

As shown in Figure 7-2, the procedure for developing concentration
estimates began with the initial, common starting point: those
radionuclides identified in Phase II as important for estimating doses.
However, as described in the following, different modeling approaches
were used for concentration estimates in the Savannah River and those in
Lower Three Runs Creek at Martin.

![](media/image2.wmf){width="5.834722222222222in"
height="6.767361111111111in"}

Figure 7‑2 Approaches to Estimating Radionuclide Concentrations in Water
at Exposure Locations

These procedural steps for developing the source term are briefly
described in the following list. Then each subsection that follows
discusses these steps in more detail.

**Common Steps:**

1\. START: List of important radionuclides from Phase II, Level 1
screening analysis;

2\. Refine list of radionuclides. Two isotopes of uranium were added to
refine the treatment of health effects. ^91^Y was deleted because it
fell below the requirement for inclusion.

**Savannah River Steps:**

S-3. Attempt a simple model: estimate annual concentrations in the
Savannah River by dividing annual release rate by the annual flow rate.
This did not provide acceptable results when compared to measured
concentrations in the river.

S-4. .Phase the II model; develop scaling factors for all radionuclides
based on K~D~. Phase II modeled radionuclide releases to the Savannah
River for three important radionuclides based on several factors
influencing transport from the point of release to the river. Adjustment
factors were derived based on these modeled releases and tabulations of
annual amounts of radionuclides released at the point-of-release. These
adjustment factors were to be applied to each remaining radionuclide not
modeled in Phase II, depending on its geochemical K~D~.

S-5. Complete and correct the release data base; release data for some
years not compiled in the Phase II report and files were supplied from
other sources. Corrections for unidentified alpha emitters and
unidentified beta-gamma emitters were added. Other minor anomalies were
corrected.

S-6. Apply adjustment factors; the adjustment factors based on the Phase
II modeling were used to estimate annual concentrations from the
tabulated values of annual releases. In order to calculate
concentrations, incorporate data on annual flow rates in the Savannah
River.

S-7. END: Concentrations by year and radionuclide in the Savannah River.

**Lower Three Runs Creek Steps:**

L-3. START: Attempt a simple model; estimate annual concentrations in
Lower Three Runs Creek by dividing annual release rate by the annual
flow rate. This did not provide acceptable results when compared to
measured concentrations in the river.

L-4. Use measured concentrations for three radionuclides, ^137^Cs,
^90^Sr, ^3^H; there were in adequate or no measurements for the
remaining nuclides of interest;

L-5. Complete the concentration data base for ^137^Cs, ^90^Sr, and ^3^H,
for instances where measured concentration data was unavailable.

L-6. END: Concentrations for ^137^Cs, ^90^Sr, and ^3^H by year and
radionuclide in Lower Three Runs Creek.

## Identify Important Radionuclides Based on Phase II 

Phase II of the SRS Dose Reconstruction Project identified the
radionuclides that were released to the surface water from SRS,
performed a screening assessment to identify a smaller group of
radionuclides to be addressed in more detail, and estimated radionuclide
quantities released into water over much of the time period of nuclear
material production. This information was used as the starting point for
estimating the water concentrations of radionuclides at the exposure
locations of interest.

### Phase II Screening Assessment

The Phase II screening assessment started with a master list of
radionuclides that had been reported as released into surface water from
SRS facilities. Preliminary estimates of their yearly average release
rates were made for a 36-year period. A screening assessment was
performed to identify a smaller list of key radionuclides that were the
dominant contributors to radiation dose and cancer risk (Phase II). This
screening assessment was performed using a two-step method recommended
by the National Council on Radiation Protection and Measurements (NCRP).

The initial screening analysis conservatively assumed that all
radionuclides were discharged into a single body of surface water with a
fixed flow rate. Using the NCRP methodology referenced above, estimated
36-year average releases (representing 1954-1989), and an average
dilution flow rate of 7.7 x 109 m^3^/y of water, the total effective
doses were estimated for each radionuclide. A total dose was estimated
by summing the incremental doses from each radionuclide. A screening
factor was computed for each radionuclide equal to the ratio of the
incremental dose from each radionuclide to the total dose. Those
radionuclides that contributed at least 0.1% to the screening factor
were given further consideration in estimation of the source term. The
radionuclides that Phase II identified as meeting this criterion were
^137^Cs, ^60^Co, ^3^H, ^131^I, ^32^P, ^238^Pu, ^239^Pu, ^240^Pu, ^89^Sr,
^90^Sr, ^35^S, ^99^Tc, uranium, ^91^Y, ^65^Zn, ^95^Zr, and ^95^Nb. A
summary of the Level 1, Phase II screening results is presented in Table
7-1. A second, Level -2 screening, which ranked radionuclides according
to their relative importance by exposure pathway, was also performed.
Seven radionuclides identified in this fashion were: ^3^H, ^137^Cs,
^90^Sr, ^60^Co, ^32^P, ^131^I, and uranium.

Note that although ^91^Y was included as significant based on the Level
1 Phase II screening analysis, the numerical analysis in Phase II does
not appear to support its inclusion based either on the Level 1 or Level
2 screening criteria; its screening value was only 0.0345% of the total
screening value, which is below the 0.1% screening value criterion for
Level 1 screening. Neither did it rank among the top three radionuclides
for any exposure scenario considered in the Level 2 screening analysis.

### Modify List of Radionuclides and Properties

As shown in Figure 7-2, the second generic step in defining the source
term for liquid releases was to modify the list of radionuclides
identified as important in Phase II. The initial list of important
radionuclides resulting from the Phase II Level 1 screening analysis was
modified in several ways:

1\. Some groups of radionuclides were partitioned into separate
isotopes. This was done to provide a more refined treatment of dose
modeling. By treating isotopes individually, health effects coefficients
specific to those isotopes could be used in the dose modeling. If
isotopes were aggregated by element, as in the Phase II screening
analyses, a single coefficient (related to the isotope with the greatest
health effects) would characterize all the isotopes of the element,
possibly greatly overestimating doses and risks. Table 7-2 shows the 22
isotopes modeled for liquid releases in Phase III.

> a\. Each member of the mother-daughter pair, ^95^Nb and ^95^Zr, was
> modeled as a separate isotope to account for the slight differences in
> health effects.
>
> b\. ^134^Cs and ^137^Cs were modeled as separate isotopes; furthermore
> the Level 1 screening value for ^134^Cs, 0.52%, exceeded the criterion
> for retention.
>
> c\. ^89^Sr and ^90^Sr were modeled separately.

2\. Because the releases of Ruthenium were relatively small, all
releases were modeled as ^106^Ru.

3\. ^129^I was included for Phase III even though, like ^91^Y, its
screening value did not meet the 0.1% criterion (its screening value was
0.06%). ^129^I was included for three reasons: (a) it has similar
chemical and physical properties as ^131^I, which was identified as a
key radionuclide; (b) there were concerns about possible health effect
after it concentrates in the thyroid; and (c) although the liquid
release of ^129^I is not as well monitored as ^131^I (Kantelo 1993), its
long half-life (\~1.7x10+07 years) is orders of magnitude longer than
that of ^131^I (\~8.04 days), thus making it much longer lasting in the
environment. This long half-life could be a differential factor for some
scenarios and exposure pathways.

4\. One radionuclide, ^240^Pu was dropped from consideration. The data
upon which the Phase II estimates of releases were based did not list
^240^Pu releases separately, but always combined with other isotopes.
Furthermore, the health effects coefficients for ^239^Pu and ^240^Pu are
very close, so modeling ^240^Pu as ^239^Pu will have little effect on
the dose estimates. Since there appeared to be no basis and no
motivation for differentiating these two isotopes, separate
consideration of ^240^Pu was dropped.

5\. It was considered appropriate to include as releases radioactivity
measured as unidentified alpha or unidentified beta-gamma activity.
Although the SRS had recorded releases of such material over the years
of site operation, an explicit treatment in Phase II was not apparent.
Therefore two additional categories were added for these types of
releases. However, to provide bounding estimates of their health
effects, the unidentified alpha activity was added to the releases for
^239^Pu and the unidentified beta-gamma activity was added to the
releases for ^90^Sr. These two classes are indicated in Table 7-2 to
indicate that these activities were compiled and tracked separately.

The general approach for partitioning aggregate quantities of
radionuclides is summarized in Table 7-3. (See [Appendix
C](../Appendix_C%20-Ready%20for%20CDC_031405.doc) for details.) Unlike
the analysis of releases to air, there was no need to refine the
treatment of certain radionuclides by defining their chemical form; this
is because all radionuclides were either dissolved or suspended in
water, which dominated the chemistry. For example, tritium would be
present as tritiated water.

Table 7‑3 Partitioning Assumptions for Radionuclides Released to Surface
Water

  -------------- ------------ -------------------------------------------
  Constituent    SRS Area     Isotopic Distribution by Activity

  ^89^Sr, ^90^Sr F&H Areas    75% ^89^Sr; 25% ^90^Sr

                 A Area       100% ^90^Sr

                 D Area       100% ^90^Sr

                 Central      100% ^90^Sr
                 Shops        

  ^95^Nb, ^95^Zr All areas    65% ^95^Nb; 35% ^95^Zr

  ^134^Cs,       D Area       100% ^137^Cs
  ^137^Cs                     

  Uranium        Reactor      91.73% ^234^U; 1.79% ^235^U; 6.45% ^236^U;
                 Areas        0.03% ^238^U

                 F Area       1.27% ^235^U; 98.73% ^238^U

                 H Area       91.73% ^234^U; 1.79% ^235^U; 6.45% ^236^U;
                              0.03% ^238^U

                 M Area       1.27% ^235^U; 98.73% ^238^U

                 A Area (SRL) 91.44% ^234^U; 1.8% ^235^U; 6.4% ^236^U;
                              0.36% ^238^U

                 CMX/TNX      49.49% ^234^U; 2.25% ^235^U; 48.26% ^238^U

                 D Area       91.73% ^234^U; 1.79% ^235^U; 6.45% ^236^U;
                              0.03% ^238^U

  Total          All Areas    100% ^239^Pu
  plutonium                   

  Unidentified   All Areas    100% ^239^Pu
  alpha                       

  Unidentified   All Areas    100% ^90^Sr
  beta-gamma                  
  -------------- ------------ -------------------------------------------

## Modeling Releases and Concentrations for the Savannah River

### A Simple Model (Step S-3)

As a first step in estimating radionuclide concentrations in the
Savannah River, a simple model based on conservation of mass was
evaluated (Step 3 in Figure 7-2). Recall that the point of interest on
the Savannah River was located below the confluence with Lower Three
Runs Creek; actually, the point of interest is very close to the USGS
flow monitoring station at river mile 120 (RM-118.8 in later years) at
highway 301 (also designated in various SRS reports as station 10A or
R-10). Because the location of interest is downriver from the points
where site streams drain into the Savannah River, one can reasonably
assume that all liquid releases exiting the site boundary must pass
through this point. Since the river flow is measured very close to this
point, one can construct a simple mathematical model based on
conservation of mass for the average radionuclide concentration at this
location:

C~ij~ = R~ij~/Q~j~ (7-1)

Where,

C~ij~ is the concentration of radionuclide i in year j (Bq/m^3^);

R~ij~ is the quantity of radionuclide i released from the SRS to water
in year j (Bq/y);

Q~j~ is the flow rate of water past the location for year j (m^3^/y)

![](media/image3.wmf){width="6.555555555555555in"
height="4.055555555555555in"}However, as described in Section 7.1.3, the
migration of radionuclides from their point of release on the SRS to
this location of interest in the Savannah River is not direct or simple.
Nevertheless, to test a simple approximation, the quantities of
radionuclides released from the facility were assumed to be equal to the
quantities ending up in the river, for any given year. Figure 7-3 and
Figure 7-4 compare radionuclide concentrations computed according to
this simple model to measured concentrations at this location.
Comparisons are shown for tritium in Figure 7-3 and ^137^cesium in
Figure 7-4. Measured concentrations at this location were not apparent
for years prior to 1960. Two different estimates of flow rate were used
to compute the calculated concentrations. In one case the "USGS Actual
Flow Rate" was used for each year of the calculation, in full accord
with equation (7-1). In the other case, the "39-year Average Flow Rate"
was used; i.e., the flow rate was a fixed value (9.49 billion cubic
meters) for all years. Note that the measured and calculated
concentrations do not agree very well. For tritium, measured values in
early years are higher than calculated values; in later years, the peaks
and dips do not correspond in time very well. For cesium, early measured
values are higher than calculated concentrations, but in middle years
calculated values are higher than measured values.

Figure 7‑3 ^3^H Concentration in Savannah River (pCi/L)

Figure 7‑4 ^137^Cs Concentration in Savannah River Water (pCi/L)

![](media/image4.wmf){width="6.64375in"
height="3.813888888888889in"}Because of this lack of agreement with
measured concentrations, use of this simple modeling approach was
abandoned. However, this presented the problem of exactly how this
necessary input for the dose reconstruction (i.e., radionuclide
concentrations in the Savannah River) would be obtained. Although there
were measured concentrations for a few radionuclides (^3^H, ^137^Cs,
^131^I, ^90^Sr, and others), this was not a suitable solution because:

-   The goal of the dose reconstruction was to represent doses from the
    set of 22 radionuclides selected (Table 7-2) and there were no
    measured values for most of these;

-   The measured concentrations were frequently near detection limits
    for the instruments used, so the accuracy of the measurements was
    questionable; in some cases, the detection limit (or half the
    detection limit) was listed as the measured value;

-   Consistent measurements of concentrations were not available during
    some of the important early years of site operation, when releases
    were known to be large;

-   The estimates of average annual measured concentrations were based
    on periodic samples that were subject to substantial uncertainties:

    -   the possibility that major releases were not effectively or
        consistently sampled and

    -   the possibility that the turbulent, unsteady flow in the river
        steered contaminated water toward or away from the sampling
        locations.

### Adapt the Phase II Water Transport Model for Savannah River Concentrations (Step S-4)

In order to overcome the difficulties encountered with a simple model of
radionuclide concentrations in the Savannah River, the model developed
in Phase II for a few radionuclides was adapted and extended for Phase
III. This is shown as Step 4 in Figure 7-2.

#### Phase II Water Transport Model

Section 7.1.3 of this report and Chapter 5 of Phase II discuss why the
accounting of releases to the surface water pathway ***at the point of
release*** is not an accurate estimate of the actual releases from the
SRS site to the Savannah River. Chapter 5 of the Phase II report
describes how a relatively simple model was used to estimate the release
to the Savannah River of ^3^H, ^90^Sr, and ^137^Cs, based on
concentrations of these constituents measured at the sampling stations
along Road A, the sampling point closest to the river (Phase II). These
three radionuclides were identified in Phase II as important possible
contributors to either offsite release or dose and had been monitored
extensively during the years of nuclear material production.

The Phase II model explicitly considers the following factors:

1\. Transport of radionuclides through surface water as dissolved and
suspended constituents.

2\. Release of previously retained radionuclides by periodic flooding of
the Savannah River Swamp.

3\. Measurement uncertainty.

The effects of the various physical and chemical interactions of
released radionuclides with the soil, biota, and other features of the
SRS generally decreased the modeled radionuclide quantities reaching the
Savannah River. On the other hand, many of the radionuclide measurement
uncertainties, when incorporated into the Phase II model, increased the
modeled quantities discharged to the Savannah River.

The SRS Swamp was observed to flood about 20% of the time (74 days per
year on the average) from 1958 to 1967. It was assumed that additional
releases to the Savannah River from the swamp occurred when there was
flooding. This uncertainty was considered a source of bias that
increased releases of radionuclides such as cesium and strontium that
were retained in the swamp. For most years, releases were increased for
cesium and strontium by 20% (with a range of 10%-30%). For years with
very high rainfall amounts like 1964 and 1971, a value of 40% (with a
range of 25%- 60%) was assumed. For years with low rainfall, it was
assumed that the swamp flooded only about 10% of the time (with a range
of 5%-15%) (Phase II). (Detailed records existed for annual rainfall).
Uncertainties associated with the release estimates were considered to
originate from analytical errors in measurement of flow and in sampling
and analysis of radionuclide concentrations in the water. Because
tritium was not impacted heavily by flow through the SRS swamp, sampling
and analytical uncertainties were the major sources of uncertainty in
the release estimates for tritium. The effluent volume to the site
streams was monitored reasonably well by both the Site and the USGS
(Phase II). Estimates of error for the routine concentration
measurements varied with the radionuclide, the sample preparation and
with the counting procedure (Phase II).

Measurements of effluent releases and concentrations for ^137^Cs and
^90^Sr at the Road A monitoring locations specific were not made in
early years. Prior to 1960, only nonvolatile beta activity was measured.
To estimate annual ^137^Cs releases for times when ^137^Cs specific
measurements were not made, a ratio was calculated of ^137^Cs to
nonvolatile beta activity when both measurements were made at the same
time and location. This ratio was used along with the nonvolatile beta
activity measurements to estimate levels of ^137^Cs activity in the site
streams at the Road A monitoring locations for years when ^137^Cs
-specific measurements were not made. A similar procedure was used for
^90^Sr.

#### Adaptation of Phase II Model for Savannah River Concentrations

A mathematical model of the transport of individual radionuclides to the
Savannah River, similar to that used in Phase II, would require
significant resources to develop and validate. The complex nature of
radionuclide transport by surface water at the SRS requires
consideration of the loss mechanisms, time delays, and uncertainties
that influence radionuclide concentrations reaching the Savannah River.
Because each chemical species has unique aqueous transport properties,
developing a model that would accommodate the variations in
chemical-physical transport was beyond the scope of Phase III.

However, Phase II had modeled the quantities of three specific
radionuclides (^3^H, ^90^Sr, ^137^Cs) released into the Savannah River,
taking into account the complex phenomena and issues governing their
migration. The release quantities estimated by the Phase II model are
different from the facility releases (point of release quantities)
compiled in Phase II and in the SRS historical data. These differences
represent the effect of the phenomena causing radionuclide decay,
storage, and release, during migration in site streams, from seepage
basins, and through the Savannah River swamp and measurement
uncertainty. A quantitative measure representing these phenomena is just
the ratio of the modeled release activity to the facility release
activity:

F~jk~ = R~Mjk~/R~Fjk~ (7-2)

Where,

> F~jk~ is the factor representing the effects of radionuclide migration
> for year j and modeled radionuclide k;

R~Mjk~ is the modeled release of radionuclide k for year j;

R~Fjk~ is the facility release of radionuclide k for year j tabulated
from site data.

Note that the index "k" is used to denote the radionuclide here, rather
than the index "i" used in equation (7-1), because "k" refers only to
one of the three radionuclides (^3^H, ^90^Sr, ^137^Cs) modeled in Phase
II, while "i" refers to any radionuclide.

The fundamental assumption made to extend these results of Phase II
modeling to the analysis in Phase III is that the distribution
coefficient (K~D~ -- a measure of the degree to which a particular
radionuclide is sorbed to soil, sediment, and some biota) of a
radionuclide would be the primary factor affecting the influence of the
site, as represented by the factor, F~jk~. Using this assumption, one
could extend the modeling of the three radionuclides performed in Phase
II to the entire suite of radionuclides modeled in Phase III. As will be
described in more detail, this extension was based on three categories
of K~D~ into which the Phase III radionuclides were binned. A more
precise rendering was not considered warranted given the extent of other
uncertainties.

As stated in Section 7.3.2.1, other factors incorporated into the Phase
II model were periodic flooding of the Savannah River swamp and
uncertainties in measuring the quantities of released radionuclides.
Clearly, K~D~ does not encompass these factors. However, the factors
representing river flooding were tied to precipitation records and were
adjusted from year to year; similarly, the factors representing
measurement uncertainty were adjusted annually, with larger
uncertainties in earlier years. Thus, the annual variations in the
factor defined by equation (7-2) should incorporate these other facets
of the Phase II model. However, some of the uncertainties related to
measuring tritium in environmental samples are unique to tritium. This
may mean that factors developed for tritium, if applied to other
radionuclides, may overestimate the degree of measurement uncertainty.

A complication in applying equation (7-2) is that R~mjk~, the modeled
release of radionuclide k for year j, is a random variable, not a single
value, because the model used in Phase II was probabilistic. However,
the median value of the distribution was chosen as a measure of the
central tendency of these quantities.

The remaining steps needed to estimate releases of any radionuclide of
interest to the Savannah River, based on the factors defined by equation
(7-2) are:

1\. Determine the annual radionuclide water releases for each
radionuclide from SRS facilities, for the three modeled radionuclides,
R~Fjk~, and for all other radionuclides, R~Fij~;

2\. Compute the ratios, F~jk~, indicated by equation (7-2);

3\. Bin the radionuclides by K~D~ group;

4\. Apply the ratios for each group of radionuclides to annual releases
from facilities, thereby obtaining adjusted annual releases by
radionuclide. However, the release data base needed to be completed and
corrected before applying the adjustment factors (discussed in Section
7.3.3), so this aspect is discussed in Section 7.3.4.

##### Annual Radionuclide Release at Points of Release

The principal reference used to develop the annual radionuclide
point-of-release data files, (i.e. files containing R~Fjk~, the facility
release of radionuclide k for year j tabulated from site data) was
Cummins et al (Cummins 1991a). To develop the data files, a guiding
decision had to be made about the specific releases to be included.

Liquid releases from the site can be placed into three categories:

1\. Category 1 - Direct releases to onsite streams

2\. Category 2 - Migration from seepage basins into onsite streams

3\. Category 3 - Direct releases to seepage and containment basins.

Although the total release to site streams could be the sum of
Categories 1 and 2, the Phase II report generally used the sum of
Categories 1 and 3 to represent the liquid source terms in the screening
assessment. There appear to be at least two reasons for this choice:

\(A\) because migration from the seepage basins is distributed in time
and space, measurements of concentrations immediately downstream of the
seepage basins may under-represent the total flux from the seepage
basins to the streams; and

\(B\) the sum of Categories 1 and 3 should be a conservative estimate of
liquid releases to site streams.

Exceptions are ^3^H and ^131^I, where only direct releases to streams
(Category 1) were considered for the screening assessment.

For these reasons, the annual sums of releases from Categories 1 and 3
were chosen as representative of SRS releases to site streams. This
meant that tritium evaporated from seepage and containment basins was
excluded from the point-of-release data file created for tritium.
Evaporated tritium was included in the Phase III atmospheric releases
(Chapter 5). It also meant that the estimated ^137^Cs desorption from
the Four Mile Creek bed that was reported by Cummins et al (Cummins
1991a) was not included in the data files. The activity reported in this
desorption was already included in the Category 1 and 3 releases as
described above. Including these desorption estimates would have caused
double counting.

##### Adjustment Factor Development

Adjustment factors were calculated according to equation (7-2) by
dividing the median values of radionuclide release computed by the Phase
II release model for each of three modeled radionuclides by the
radionuclide releases for these radionuclides from all facilities. These
modeled and tabulated releases are listed in Table 7-4. The resultant
adjustment factors are listed in Table 7-5.

Table 7‑4 Tabulated Releases from Facilities and Median Value of Modeled
Releases Used for Adjustment Factors (Ci)

  --------------------------------------------------------------------------------------------------
           Tabulated                                    Median Value                  
           Releases from                                of Modeled                    
           Facilities                                   Releases                      
  -------- -------------- -------------- -------------- -------------- -------------- --------------
  Year     ^3^H           ^137^Cs        ^90^Sr         ^3^H           ^137^Cs        ^90^Sr

  1954     3.66x10^+02^   1.80x10^-01^   3.90x10^-02^   7.64x10^+03^   1.41x10^-01^   4.13x10^-02^

  1955     5.87x10^+03^   1.37x10^0^     8.16x10^-01^   1.32x10^+04^   2.65x10^-01^   1.45x10^-01^

  1956     9.39x10^+03^   3.43 x10^0^    1.04x10^+01^   1.50x10^+04^   1.11 x10^0^    3.60x10^-01^

  1957     2.24x10^+04^   8.40x10^+02^   1.96x10^+02^   2.16x10^+04^   1.16 x10^0^    1.54 x10^0^

  1958     2.88x10^+04^   1.04x10^+02^   1.58x10^+01^   2.88x10^+04^   9.51 x10^0^    8.30x10^-01^

  1959     5.17x10^+04^   4.14x10^+01^   2.18x10^+01^   6.29x10^+04^   3.59 x10^0^    1.80 x10^0^

  1960     6.09x10^+04^   4.36x10^+01^   2.36x10^+01^   6.98x10^+04^   7.60 x10^0^    1.76x10^+01^

  1961     8.11x10^+04^   4.06x10^+01^   9.85 x10^0^    8.28x10^+04^   1.03x10^+01^   4.22 x10^0^

  1962     7.23x10^+04^   1.03x10^+02^   1.04x10^+01^   6.47x10^+04^   1.92x10^+01^   6.78 x10^0^

  1963     9.66x10^+04^   1.23x10^+02^   2.10x10^+01^   9.69x10^+04^   1.68x10^+01^   1.07x10^+01^

  1964     1.17x10^+05^   1.30x10^+02^   1.41x10^+01^   1.21x10^+05^   5.15x10^+01^   1.13x10^+01^

  1965     1.28x10^+05^   5.56x10^+01^   1.17x10^+01^   1.06x10^+05^   2.35x10^+01^   5.22 x10^0^

  1966     1.33x10^+05^   5.36x10^+01^   6.12 x10^0^    9.56x10^+04^   2.72x10^+01^   4.46 x10^0^

  1967     1.04x10^+05^   6.87x10^+01^   6.72 x10^0^    8.75x10^+04^   3.80x10^+01^   4.82 x10^0^

  1968     1.07x10^+05^   7.08x10^+01^   9.19 x10^0^    8.39x10^+04^   2.08x10^+01^   5.46 x10^0^

  1969     7.88x10^+04^   5.14x10^+01^   1.02x10^+01^   7.64x10^+04^   1.04x10^+01^   3.58 x10^0^

  1970     6.61x10^+04^   4.43x10^+01^   7.26 x10^0^    4.25x10^+04^   1.02x10^+01^   3.89 x10^0^

  1971     4.47x10^+04^   1.05x10^+01^   3.14 x10^0^    4.44x10^+04^   1.69 x10^0^    3.81 x10^0^

  1972     6.09x10^+04^   9.14 x10^0^    1.25 x10^0^    4.68x10^+04^   6.28x10^-01^   1.92 x10^0^

  1973     8.69x10^+04^   7.48 x10^0^    9.01x10^-01^   6.10x10^+04^   4.44x10^-01^   2.07 x10^0^

  1974     5.61x10^+04^   8.09 x10^0^    4.27x10^-01^   5.41x10^+04^   7.01x10^-01^   1.72 x10^0^

  1975     5.15x10^+04^   7.75 x10^0^    9.12x10^-01^   4.93x10^+04^   3.61x10^-01^   1.46 x10^0^

  1976     7.32x10^+04^   8.94 x10^0^    4.76x10^-01^   4.64x10^+04^   1.46x10^-01^   1.18 x10^0^

  1977     4.59x10^+04^   6.58 x10^0^    5.55x10^-01^   4.03x10^+04^   2.45x10^-01^   9.04x10^-01^

  1978     3.76x10^+04^   1.04x10^+01^   2.06 x10^0^    3.55x10^+04^   1.04x10^-01^   6.20x10^-01^

  1979     4.52x10^+04^   6.27 x10^0^    2.68 x10^0^    2.84x10^+04^   1.04x10^-01^   6.24x10^-01^

  1980     3.54x10^+04^   1.83 x10^0^    1.55x10^-01^   3.00x10^+04^   7.72x10^-02^   5.05x10^-01^

  1981     3.94x10^+04^   2.81 x10^0^    1.04 x10^0^    2.51x10^+04^   1.16x10^-01^   4.61x10^-01^

  1982     3.15x10^+04^   2.85 x10^0^    6.98x10^-01^   3.08x10^+04^   8.36x10^-02^   3.95x10^-01^

  1983     4.06x10^+04^   3.43 x10^0^    2.35x10^-01^   3.24x10^+04^   7.74x10^-02^   3.84x10^-01^

  1984     3.58x10^+04^   6.13 x10^0^    9.44x10^-02^   3.23x10^+04^   1.22x10^-01^   4.25x10^-01^

  1985     3.40x10^+04^   6.23 x10^0^    1.70x10^-01^   2.21x10^+04^   5.14x10^-02^   2.25x10^-01^

  1986     4.52x10^+04^   1.13x10^+01^   1.28x10^-01^   2.21x10^+04^   5.51x10^-02^   3.26x10^-01^

  1987     2.75x10^+04^   1.54x10^+01^   5.69x10^-02^   2.04x10^+04^   1.98x10^-01^   3.63x10^-01^

  1988     1.44x10^+04^   6.39 x10^0^    4.40x10^-02^   1.82x10^+04^   2.92x10^-01^   2.63x10^-01^

  1989     3.97x10^+03^   2.10x10^-01^   1.68x10^-02^   1.76x10^+04^   1.82x10^-01^   2.56x10^-01^

  1990     2.62x10^+03^   4.83x10^-02^   4.28x10^-01^   1.53x10^+04^   4.29x10^-02^   5.41x10^-01^

  1991     1.06x10^+04^   2.64x10^-02^   8.91x10^-02^   2.64x10^+04^   2.57x10^-02^   1.14x10^-01^

  1992     2.00x10^+03^   1.02x10^-01^   7.86x10^-01^   1.30x10^+04^   8.46x10^-02^   8.84x10^-01^
  --------------------------------------------------------------------------------------------------

Table 7‑5 Adjustment Factors by Radionuclide Group and Year

+--------+--------+--------+-------+-------+--------+--------+--------+
| Year   | Group  | Group  | Group | Year  | Group  | Group  | Group  |
|        | 1      | 2      | 3     |       | 1      | 2      | 3      |
+--------+--------+--------+-------+-------+--------+--------+--------+
|        | ^3^H   | ^90^Sr | ^1    |       | ^3^H   | ^90^Sr | ^      |
|        |        |        | 37^Cs |       |        |        | 137^Cs |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1954   | 1.00   | 1.0582 | 0     | 1976  | 0.6346 | 2.4755 | 0.0163 |
|        | 00^\*^ |        | .7813 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1955   | 2.2482 | 0.1773 | 0     | 1977  | 0.8775 | 1.6271 | 0.0372 |
|        |        |        | .1927 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1956   | 1.6024 | 0.0345 | 0     | 1978  | 0.9418 | 0.3006 | 0.0101 |
|        |        |        | .3224 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1957   | 0.9645 | 0.0079 | 0     | 1979  | 0.6284 | 0.2326 | 0.0165 |
|        |        |        | .0014 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1958   | 1.0004 | 0.0527 | 0     | 1980  | 0.8490 | 3.2573 | 0.0423 |
|        |        |        | .0918 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1959   | 1.2175 | 0.0824 | 0     | 1981  | 0.6378 | 0.4416 | 0.0412 |
|        |        |        | .0867 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1960   | 1.1465 | 0.7467 | 0     | 1982  | 0.9787 | 0.5655 | 0.0294 |
|        |        |        | .1744 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1961   | 1.0203 | 0.4284 | 0     | 1983  | 0.7962 | 1.6370 | 0.0226 |
|        |        |        | .2528 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1962   | 0.8954 | 0.6499 | 0     | 1984  | 0.9031 | 4.5042 | 0.0200 |
|        |        |        | .1871 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1963   | 1.0024 | 0.5079 | 0     | 1985  | 0.6496 | 1.3263 | 0.0083 |
|        |        |        | .1362 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1964   | 1.0340 | 0.8037 | 0     | 1986  | 0.4893 | 2.5464 | 0.0049 |
|        |        |        | .3964 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1965   | 0.8273 | 0.4443 | 0     | 1987  | 0.7426 | 6.3833 | 0.0128 |
|        |        |        | .4223 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1966   | 0.7190 | 0.7290 | 0     | 1988  | 1.2619 | 5.9846 | 0.0456 |
|        |        |        | .5078 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1967   | 0.8421 | 0.7171 | 0     | 1989  | 4.4292 | 1      | 0.8696 |
|        |        |        | .5530 |       |        | 5.1968 |        |
|        |        |        |       | 1990  |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1968   | 0.7872 | 0.5945 | 0     |       | 5.8478 | 1.2652 | 0.8899 |
|        |        |        | .2933 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1969   | 0.9703 | 0.3495 | 0     | 1991  | 2.5013 | 1.2751 | 0.9724 |
|        |        |        | .2026 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1970   | 0.6430 | 0.5361 | 0     | 1992  | 6.4926 | 1.1252 | 0.8279 |
|        |        |        | .2313 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1971   | 0.9923 | 1.2122 | 0     |       |        |        |        |
|        |        |        | .1611 |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1972   | 0.7686 | 1.5321 | 0     | **M   | 1.3325 | 1.7623 | 0.2339 |
|        |        |        | .0687 | ean** |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1973   | 0.7021 | 2.3023 | 0     | **Med | 0.9589 | 0.8037 | 0.0918 |
|        |        |        | .0593 | ian** |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1974   | 0.9644 | 4.0233 | 0     | **    | 6.4926 | 1      | 0.9724 |
|        |        |        | .0866 | Max** |        | 5.1968 |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| 1975   | 0.9589 | 1.5961 | 0     | **    | 0.4893 | 0.0079 | 0.0014 |
|        |        |        | .0467 | Min** |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+
| \*Orig |        |        |       |       |        |        |        |
| inally |        |        |       |       |        |        |        |
| this   |        |        |       |       |        |        |        |
| value  |        |        |       |       |        |        |        |
| was    |        |        |       |       |        |        |        |
| calc   |        |        |       |       |        |        |        |
| ulated |        |        |       |       |        |        |        |
| as     |        |        |       |       |        |        |        |
| 20     |        |        |       |       |        |        |        |
| .8814. |        |        |       |       |        |        |        |
+--------+--------+--------+-------+-------+--------+--------+--------+

Note that the adjustment factor initially calculated for tritium in year
1954 was 20.8814, which is three times larger than the next highest
tritium adjustment factor and about 20 times larger than the median
value of all adjustment factors over 39 years. This large factor was
calculated because of the inclusion of estimated releases from D-Area in
the Phase II modeling of tritium release to the Savannah River. In Phase
II, 17,530 curies of tritium from D-Area was assumed to be released
surface waters in 1954 (Phase II). This D-Area release, however, is not
documented in Cummins et al (Cummins 1991a). For Phase III, it was
reasoned that if tritium release from D-Area were the only reason for
such a large adjustment factor in 1954, the other radionuclides in this
group (i.e. ^129^I, I^131^, ^99^Tc, and ^35^S) should not be similarly
adjusted lest the true releases of these radionuclides be significantly
overestimated. Another reason for not using such a large adjustment
factor for the tritium group in 1954 was that the functionality of
D-Area was heavy water rework, and site effluent release data (Cummins
1991a) does not show iodine, technetium, and sulfur being released from
that facility in 1954. The factor 1.0 was thus used for the tritium
group in 1954 to avoid overestimation of other radionuclide releases.

##### Binning Radionuclides by Distribution Coefficient, K~D~

As stated above, the adjustment factors developed in the previous
section are to be applied according to the geochemical characteristics
of the released radionuclides as indicated by the distribution
coefficient. The soil-to-water distribution coefficient K~D~ is a
measure of the partitioning between solid and liquid phases that a
radionuclide experiences as it passes through environmental media. As
radioactive contaminants move through the soils, sediments, and the
swamp at the SRS site, they will be attracted to various surfaces. This
attraction results in a delay (retardation) of the transport of the
contaminant through the system relative to the flow of water. The amount
of a particular radionuclide that will reach the Savannah River is
expected to depend on this retardation phenomenon and the radiological
half-life of the radionuclide.

The K~D~ values of the radionuclides considered in this analysis span
many orders of magnitude. However, to simplify the analysis, the
radionuclides have been divided into only three groups:

> \(1\) K~D~ [\<]{.underline} 10
>
> \(2\) 10 ≤ K~D~ ≤ 1000
>
> \(3\) K~D~ \> 1000

These groups correspond to the nominal K~D~ values used in the Phase II
modeling of water releases: 0, 100, and 10,000, respectively for ^3^H,
^90^Sr, and ^137^Cs. All radionuclides analyzed in Phase III were
assigned to a particular group and were assigned the same annual
adjustment factor calculated for that group. The group assigned to each
radionuclide is stated in Table 7-6. Table 7-6 also provides the K~D~
value(s) used to determine the group assigned to each radionuclide. Note
that the "Adjustment Factor Group" in the last column in Table 7-6
corresponds to the index "k" in equation (7-2).

Table 7‑6 Grouping of Radionuclides According to K~D~ Values

+-----------+--------------+-----------+-------------+--------------+
| Rad       | S            |           |             | Adjustment   |
| ionuclide | oil-to-Water |           |             | Factor Group |
|           | Distribution |           |             |              |
|           | Coefficient, |           |             |              |
|           | K~D~         |           |             |              |
+===========+==============+===========+=============+==============+
|           | **Phase II   | **Soil    | **Swamp     |              |
|           | Value**      | Value\*** | Value^†^**  |              |
+-----------+--------------+-----------+-------------+--------------+
| ^3^H      | > **0**      | > 0       |             | > ^3^H       |
+-----------+--------------+-----------+-------------+--------------+
| ^129^I,   |              | > 1.55    |             | > ^3^H       |
| ^131^I    |              |           |             |              |
+-----------+--------------+-----------+-------------+--------------+
| ^99^Tc    |              | > 2.49    |             | > ^3^H       |
+-----------+--------------+-----------+-------------+--------------+
| ^35^S     |              | > 7.5     |             | > ^3^H       |
+-----------+--------------+-----------+-------------+--------------+
| ^103^Ru,  |              | > 55      |             | > ^90^Sr     |
| ^106^Ru   |              |           |             |              |
+-----------+--------------+-----------+-------------+--------------+
| ^60^Co    |              | > 60      |             | > ^90^Sr     |
+-----------+--------------+-----------+-------------+--------------+
| ^89^Sr,   | > **100**    | > 3040    | > 1676      | > ^90^Sr     |
| ^90^Sr    |              |           |             |              |
+-----------+--------------+-----------+-------------+--------------+
| ^95^Nb    |              | > 160     |             | > ^90^Sr     |
+-----------+--------------+-----------+-------------+--------------+
| ^32^P     |              | > 173     |             | > ^90^Sr     |
+-----------+--------------+-----------+-------------+--------------+
| ^65^Zn    |              | > 200     |             | > ^90^Sr     |
+-----------+--------------+-----------+-------------+--------------+
| ^141^Ce,  |              | > 490     | > 255       | > ^90^Sr     |
| ^144^Ce   |              |           |             |              |
+-----------+--------------+-----------+-------------+--------------+
| ^95^Zr    |              | > 600     |             | > ^90^Sr     |
+-----------+--------------+-----------+-------------+--------------+
| U         |              | > 1000    | > 170       | > ^90^Sr     |
+-----------+--------------+-----------+-------------+--------------+
| Pu        |              | > 4100    |             | > ^137^Cs    |
+-----------+--------------+-----------+-------------+--------------+
| ^134^Cs,  | > **10,000** | > 59      |             | > ^137^Cs    |
| ^137^Cs   |              |           |             |              |
+-----------+--------------+-----------+-------------+--------------+
| \*Source: |              |           |             |              |
| Kaplan et |              |           |             |              |
| al.,      |              |           |             |              |
| 2003.     |              |           |             |              |
|           |              |           |             |              |
| **^†^     |              |           |             |              |
| **Source: |              |           |             |              |
| Kaplan    |              |           |             |              |
| and       |              |           |             |              |
| Serkiz,   |              |           |             |              |
| 2000.     |              |           |             |              |
+-----------+--------------+-----------+-------------+--------------+

It should be noted that the K~D~'s used in Phase II are orders of
magnitude different from those reported in recent SRS literature
(Kaplan, 2003). In the Phase II modeling, a range of K~D~'s having a
median value of 10,000 were used for cesium, whereas the range of values
used for strontium had a median value of 100. Median K~D~'s reported by
Kaplan et al for agricultural soils are 59 for cesium and 3041 for
strontium (Kaplan 2003). Another report by Kaplan gives a K~D~ value of
1676 for ^90^Sr in the swampy soils (Kaplan and Serkiz, 2000).

### Completion and Correction of the Release Data Base (Step S-5)

The data base describing liquid releases from various SRS facilities was
compiled in electronic format largely from SRS tabulations (Cummins,
1991a). This initial set of data was completed and corrected as follows:

1\. Data for releases in the years 1990-1992 were added by examining the
appropriate Site Environmental Reports (Cummins, 1990; Cummins, 1991b;
Arnett, 1992; Arnett, 1993).

2\. Releases categorized as unidentified beta-gamma activity were added
to the ^90^Sr releases on an annual basis.

3\. Releases categorized as unidentified alpha activity were added to
the ^239^Pu releases on an annual basis.

4\. Releases of ^131^I (half-life of 8.04 days) into seepage basins were
not included because it was assumed the activity would substantially
decay before the iodine could migrate from the seepage basins to the
surface streams; i.e., for ^131^I only category 1 releases were
included.

5\. The Phase II report and SRS reports indicate a total release of 3 Ci
of ^129^I for the period from 1955-89. This 3 Ci release was apportioned
evenly over these years, since no more defined information was
available. As with other radionuclides, releases for 1990-1992 were
obtained from SRS Environmental Reports.

6\. Conflicting values for releases of ^90^Sr from the L-reactor were
obtained from the Cummins report for 1989, depending upon whether
radionuclides were summed by facility or radionuclide indexes. What
appear to be two spurious entries for ^90^Sr releases from the L-reactor
in 1989 were not included.

### Apply Adjustment Factors and Compute Concentrations for Savannah River (Step S-6) 

The completion and correction of facility release data described in the
preceding section resulted in a tabulation of the quantity of
contaminants released by year and radionuclide for the 22 radionuclides
listed in Table 7-2. These corrected facility release quantities are
used to derive the estimated releases by year and radionuclide to the
Savannah River, as follows:

R^R^~ij~ = R^CF^~ij~·F~jk~ (7-3)

Where,

R^R^~ij~ is the release to the Savannah [R]{.underline}iver of
radionuclide i and year j;

> R^CF^~ij~ is the [C]{.underline}orrected [F]{.underline}acility
> releases of radionuclide i and year j estimated according to the
> procedure in Section 7.3.3

F~jk~ is the adjustment factor computed according to equation (7-2).

Note that the correction factor, F~jk~, depends upon the both the year j
and the radionuclide group k; for each radionuclide i the correction
factor group is indicated in Table 7-6. When the radionuclide release
being adjusted in equation (7-3) was one of those modeled in Phase II
(i.e., ^137^Cs, ^90^Sr, or ^3^H), the computed release to the river,
R^R^~ij~, is just the modeled release from Phase II for each year.
However, this is not entirely the case for ^90^Sr. Because the corrected
facility release for ^90^Sr included unidentified beta-gamma activity,
the computed releases to the river, R^R^~ij~, is higher than the
releases modeled in Phase II.

Error: Reference source not found shows the yearly activity estimated by
the procedure described above for release of tritium to the Savannah
River from the SRS. This graph is consistent with the median (50th
percentile) of the Phase II model discussed in Section 7.2.3 Releases
rise to a peak in 1964 and then decrease. Figure 7-5 shows the yearly
activity estimated in Phase III for release of ^137^Cs and ^90^Sr to
surface water on the SRS site. Somewhat like tritium, releases of
^137^Cs rise to a rough peak in 1964, and then decrease, although a
second, smaller peak is seen in 1967. The large peak for ^90^Sr in 1967
reflects the release into the K-Area containment basin of over 100
curies of unidentified beta-gamma activity during that year.

Once the radionuclide releases to the Savannah River have been obtained
by the procedure described above, the concentrations of the
radionuclides in the river can be easily computed by a variant of
equation (7-1):

C~ij~ = R^R^~ij~/Q~j~ (7-4)

These concentrations were computed in this fashion, tabulated in a
spreadsheet, and input to the GENII code. Concentrations in the Savannah
River for various radionuclides computed in the manner described above
are shown in Figure 7-5. Note the peaks in activity seen for ^32^P,
^137^Cs, and ^90^Sr in the years 1966 and 1967. [Chapter
11](../Chapter_11_ready%20for%20CDC%20031405.doc) discusses how the
peaks caused high doses in receptors exposed to the contaminants
released to the water through fish ingestion.

In order to compute the concentrations indicated in equation (7-4) the
annual flow rates, Q~j~, for the Savannah River were required. Annual
flow rates for the Savannah River were derived in two ways:

1\. For the years 1954 through 1969 and for the years 1983 through 1992,
flow rates for the Savannah River as measured at Burtons Ferry Bridge
(Highway 301) near Millhaven, Georgia, were obtained from the USGS
\[USGS 2003c\]. This monitoring station is located about 500 feet
downstream of the bridge on U.S. Highway 301 linking Screven County, GA,
with Allendale County, SC. Hence, it is downstream of all surface water
discharge points into the Savannah River from SRS.

2\. No information was available from USGS for this monitoring station
for the years 1970 through 1982. For these years, flow rates were
projected from flow rates measured at Augusta, GA. The projected flow
rates were derived using a relationship from \[Hayes & Marter\]. This
reference reports a strong linear relationship (r = 0.98) between the
flows at the Burtons Ferry Bridge and Augusta monitoring stations:
Flow~BFB~ = 1.15 Flow~AUG~ + 202.

The flow rates derived for this report are listed in Table 7-7 in units
of cubic feet per second (cfs). Table 7-7 also presents the Savannah
River volumes (liters) calculated for Phase III assuming 365 days per
year (except for 366 days per year every leap year).

![](media/image5.wmf){width="5.831944444444445in"
height="3.4868055555555557in"}

Figure 7‑5 Tritium Release to Savannah River (Ci/y)

![](media/image6.wmf){width="5.847222222222222in" height="3.5125in"}

Figure 7‑6 ^137^Cesium and ^90^Strontium Release to Savannah River (Ci/y

![](media/image7.wmf){width="4.955555555555556in"
height="3.027083333333333in"}

> Figure 7‑5 Estimated Concentrations of Selected Radionuclides in
> Savannah River (pCi/mL

Table 7‑7 Savannah River Flow Rates and Annual Volumes as Determined for
Burtons Ferry Bridge (Highway 301)

+----+----+----------+------------+---+-----+-----------+------------+
| Ye | Le | Annual   | Water      | Y | L   | Annual    | Water      |
| ar | ap | Mean     | Volume     | e | eap | Mean      | Volume     |
|    | Ye | Value\*  | (Liter)    | a | Y   | Value\*   | (Liter)    |
|    | ar | (cfs)    |            | r | ear | (cfs)     |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 7,382  | > 6.       | 1 |     | > 11,101  | > 9.       |
| 54 |    |          | 60x10^+12^ | 9 |     |           | 93x10^+12^ |
|    |    |          |            | 7 |     |           |            |
|    |    |          |            | 4 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 5,974  | > 5.       | 1 |     | > 15,408  | > 1.       |
| 55 |    |          | 34x10^+12^ | 9 |     |           | 38x10^+13^ |
|    |    |          |            | 7 |     |           |            |
|    |    |          |            | 5 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 | L  | > 6,309  | > 5.       | 1 | L   | > 13,914  | > 1.       |
| 56 |    |          | 66x10^+12^ | 9 |     |           | 25x10^+13^ |
|    |    |          |            | 7 |     |           |            |
|    |    |          |            | 6 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 8,312  | > 7.       | 1 |     | > 11,646  | > 1.       |
| 57 |    |          | 43x10^+12^ | 9 |     |           | 04x10^+13^ |
|    |    |          |            | 7 |     |           |            |
|    |    |          |            | 7 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 11,038 | > 9.       | 1 |     | > 10,522  | > 9.       |
| 58 |    |          | 87x10^+12^ | 9 |     |           | 41x10^+12^ |
|    |    |          |            | 7 |     |           |            |
|    |    |          |            | 8 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 9,748  | > 8.       | 1 |     | > 13,252  | > 1.       |
| 59 |    |          | 72x10^+12^ | 9 |     |           | 18x10^+13^ |
|    |    |          |            | 7 |     |           |            |
|    |    |          |            | 9 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 | L  | > 13,112 | > 1.       | 1 | L   | > 13,201  | > 1.       |
| 60 |    |          | 18x10^+13^ | 9 |     |           | 18x10^+13^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 0 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 10,909 | > 9.       | 1 |     | > 6,599   | > 5.       |
| 61 |    |          | 75x10^+12^ | 9 |     |           | 90x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 1 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 10,580 | > 9.       | 1 |     | > 7,169   | > 6.       |
| 62 |    |          | 46x10^+12^ | 9 |     |           | 41x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 2 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 11,138 | > 9.       | 1 |     | > 12,348  | > 1.       |
| 63 |    |          | 96x10^+12^ | 9 |     |           | 10x10^+13^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 3 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 | L  | > 20,497 | > 1.       | 1 | L   | > 12,759  | > 1.       |
| 64 |    |          | 84x10^+13^ | 9 |     |           | 14x10^+13^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 4 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 12,785 | > 1.       | 1 |     | > 7,167   | > 6.       |
| 65 |    |          | 14x10^+13^ | 9 |     |           | 41x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 5 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 11,175 | > 9.       | 1 |     | > 6,175   | > 5.       |
| 66 |    |          | 99x10^+12^ | 9 |     |           | 52x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 6 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 10,573 | > 9.       | 1 |     | > 8,955   | > 8.       |
| 67 |    |          | 45x10^+12^ | 9 |     |           | 01x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 7 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 | L  | > 9,624  | > 8.       | 1 | L   | > 5,364   | > 4.       |
| 68 |    |          | 63x10^+12^ | 9 |     |           | 81x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 8 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 10,945 | > 9.       | 1 |     | > 7,966   | > 7.       |
| 69 |    |          | 79x10^+12^ | 9 |     |           | 12x10^+12^ |
|    |    |          |            | 8 |     |           |            |
|    |    |          |            | 9 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 8,208  | > 7.       | 1 |     | > 11,860  | > 1.       |
| 70 |    |          | 34x10^+12^ | 9 |     |           | 06x10^+13^ |
|    |    |          |            | 9 |     |           |            |
|    |    |          |            | 0 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 10,686 | > 9.       | 1 |     | > 11,670  | > 1.       |
| 71 |    |          | 55x10^+12^ | 9 |     |           | 04x10^+13^ |
|    |    |          |            | 9 |     |           |            |
|    |    |          |            | 1 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 | L  | > 11,235 | > 1.       | 1 | L   | > 11,860  | > 1.       |
| 72 |    |          | 01x10^+13^ | 9 |     |           | 06x10^+13^ |
|    |    |          |            | 9 |     |           |            |
|    |    |          |            | 2 |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| 19 |    | > 14,431 | > 1.       |   |     |           |            |
| 73 |    |          | 29x10^+13^ |   |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+
| \* |    |          |            |   |     |           |            |
| Fl |    |          |            |   |     |           |            |
| ow |    |          |            |   |     |           |            |
| Ra |    |          |            |   |     |           |            |
| te |    |          |            |   |     |           |            |
| Fr |    |          |            |   |     |           |            |
| om |    |          |            |   |     |           |            |
| US |    |          |            |   |     |           |            |
| GS |    |          |            |   |     |           |            |
| S  |    |          |            |   |     |           |            |
| ta |    |          |            |   |     |           |            |
| ti |    |          |            |   |     |           |            |
| on |    |          |            |   |     |           |            |
| I  |    |          |            |   |     |           |            |
| D: |    |          |            |   |     |           |            |
| 02 |    |          |            |   |     |           |            |
| 19 |    |          |            |   |     |           |            |
| 75 |    |          |            |   |     |           |            |
| 00 |    |          |            |   |     |           |            |
+----+----+----------+------------+---+-----+-----------+------------+

### Comparison of Phase II Release Estimates and Phase III Source Terms

Because the estimates for concentrations in the Savannah River were
based on water releases from the entire SRS, a comparison of the Phase
II and Phase III bases is discussed here. The data used as input to
Phase III of the SRS Dose Reconstruction Project were checked as part of
a Quality Assurance Program. However, to assure appropriate agreement
between the Phase II and Phase III analyses, the total releases for all
significant radionuclides were compared.

#### Comparison of Phase II Modeled Releases to SRS Point-of-Release Data

For ^3^H, ^90^Sr, and ^137^Cs, the annual medians (50^th^ percentile) of
the Phase II Savannah River release model are compared with the annual
point-of-release estimates for these radionuclides as compiled from
Category 1 and 3 releases documented in Cummins 1991a. The results of
this comparison are summarized in Table 7-8.

Table 7‑8 Comparison of Phase II Median Releases to Savannah River with
SRS Point-of-Release

+-------------+-------------------------------+-----------------------+
| R           | Range of Median of Model to   | Mean, Median of Model |
| adionuclide | Point-of-Release Ratios       | to Point-of- Release  |
|             |                               | Ratios                |
+-------------+-------------------------------+-----------------------+
| ^3^H        | > 0.379 -- 20.881             | > 1.228\*             |
+-------------+-------------------------------+-----------------------+
| ^90^Sr      | > 0.008 -- 6.383              | > 1.379               |
+-------------+-------------------------------+-----------------------+
| ^137^Cs     | > 0.001 -- 0.972              | > 0.234               |
+-------------+-------------------------------+-----------------------+
| \*This      |                               |                       |
| ratio does  |                               |                       |
| not include |                               |                       |
| 1954        |                               |                       |
| estimates   |                               |                       |
| for ^3^H.   |                               |                       |
+-------------+-------------------------------+-----------------------+

It was expected that the median values estimated by the Phase II surface
water model should be approximately equal to or smaller than the total
releases reported by SRS. With a few exceptions, this was the case. An
example exception is the 1954 ratio of the estimated median release to
the total tritium release. The ratio is 20.881, as noted in Section
7.4.6. The Phase II report stated that releases were adjusted if it was
believed that reported releases were too low. This extremely high ratio
is probably a reflection of such an adjustment, since reporting of
releases in the early years of operations was not as accurate as in
later years.

The ratios as a function of time are presented in Figure 7-6. Note that
the ratios are dramatically higher during the last years of operations.
The late years may reflect that operational releases from facilities in
general were reduced, but there were still releases of residual
radioactivity from the site. In particular the releases for ^90^Sr were
elevated because unidentified beta-gamma activity was added to the
^90^Sr inventory. Note that the variations in time are significant. This
is due, in part, to the model that increased releases in years with
large spring floods to account for the remobilization of radionuclides
stored in previous years in the sediments and biota of the swamp. For
these reasons, annual adjustment factors were used for Phase III rather
than an average adjustment factor covering all years.

![](media/image8.wmf){width="6.166666666666667in"
height="3.627083333333333in"}

Figure 7‑6 Annual Ratios of Phase II Median of Savannah River Release
Model to SRS Point-of-Release Data.

#### Comparison of Phase III Releases with Phase II Screening Assumptions

Because of the approach adopted for Phase III, the releases to streams,
seepage basins, and containment basins were compiled by radionuclide as
point-of-release estimates, as discussed in Section 7.3.2.2.1. There are
two comparisons of Phase III release estimates and Phase II release
estimates that help to place the Phase III analysis in context:

1\. the sum of Phase III releases for each radionuclide and all
facilities over 36 years compared to the sum of 36-year, overall site
releases for each radionuclide used in the Phase II screening analysis;
and

2\. the sum (36 years and all facilities) of the extrapolated releases
used in Phase III compared to sum of 36-year, overall site releases for
each radionuclide used in the Phase II screening analysis.

Table 7-9 shows these comparisons.

Table 7‑9 Comparison of Phase III Releases with Phase II Screening
Assumptions

+-------+------------+------------+---------+---+--------+----------+
| Rel   |            | Sum of     |         |   | Sum of |          |
| eases |            | 36-year    |         |   | 3      |          |
| from  |            | Releases   |         |   | 6-year |          |
| Phase |            | from       |         |   | Phase  |          |
| II    |            | Cummins    |         |   | III    |          |
|       |            | Data -     |         |   | Re     |          |
| W     |            | Basis for  |         |   | leases |          |
| ater- |            | Phase III  |         |   | to     |          |
| Level |            | Point-     |         |   | Sa     |          |
| 1     |            | of-Release |         |   | vannah |          |
| Scre  |            | Estimates  |         |   | River  |          |
| ening |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| R     | Surface    | Cat.       | Ratio,  | C | Phase  | Ratio,   |
| adio- | Water      | 1+Cat. 3   | Sc      | h | III    | Phase    |
|       | Release    | Unless     | reening | e | R      | III      |
| nu    | from SRS   | Otherwise  | to      | c | elease | River    |
| clide | (Ci/36 yr) | Noted      | Phase   | k | to     | Release  |
|       |            | (Ci/36 yr) | III     |   | River  | to       |
|       |            |            | Basis   |   |        | S        |
|       |            |            |         |   | (Ci/36 | creening |
|       |            |            |         |   | yr)    |          |
+-------+------------+------------+---------+---+--------+----------+
| ^2    | > 1.00E-02 | >          | >       |   | >      | >        |
| 41^Am |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^14   | > 2.20E+02 | >          | >       |   | >      | >        |
| 0^Ba, |            |            |         |   |        |          |
| ^1    |            |            |         |   |        |          |
| 40^La |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^14   | > 7.       | > 7.       | > 0.99  |   | >      | > 6.54   |
| 1^Ce, | 00x10^+02^ | 08x10^+02^ |         |   | 4.58x1 | x10^-01^ |
| ^1    |            |            |         |   | 0^+02^ |          |
| 44^Ce |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^2    | > 8.00E-01 | >          | >       |   | >      | >        |
| 44^Cm |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^1    | > 1.       | > 1.       | > 1.00  |   | > 2.87 | > 2.13   |
| 34^Cs | 35x10^+01^ | 35x10^+01^ |         |   |        | x10^-01^ |
+-------+------------+------------+---------+---+--------+----------+
| ^1    | > 1.       | > 1.       | > 1.00  |   | >      | > 1.32   |
| 37^Cs | 95x10^+03^ | 95x10^+03^ |         |   | 2.57x1 | x10^-01^ |
|       |            |            |         |   | 0^+02^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 2.73E+00 | >          | >       |   | >      | >        |
| 58^Co |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 8.       | > 8.       | > 1.00  |   | >      | > 6.43   |
| 60^Co | 40x10^+01^ | 42x10^+01^ |         |   | 5.40x1 | x10^-01^ |
|       |            |            |         |   | 0^+01^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 5.00E+03 | >          | >       |   | >      | >        |
| 51^Cr |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^3^H  | > 1.       | > 1.       | > 0.98  |   | >      | > 1.16   |
|       | 50x10^+06^ | 53x10^+06^ |         | \ | 1.73x1 |          |
|       |            |            |         | * | 0^+06^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 3.       | > 3.       | > 1.00  |   | >      | > 9.50   |
| 131^I | 03x10^+02^ | 02x10^+02^ |         | \ | 2.88x1 | x10^-01^ |
|       |            |            |         | * | 0^+02^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 1.20     | > 3.00     | > see   |   | > 2.71 | > 2.26   |
| 129^I |            |            | > note  | \ |        |          |
|       |            |            |         | * |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^2    | > 1.44E+03 | >          | >       |   | >      | >        |
| 39^Np |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^32^P | > 1.       | > 1.       | > 1.00  |   | >      | > 6.60   |
|       | 96x10^+02^ | 96x10^+02^ |         |   | 1.29x1 | x10^-01^ |
|       |            |            |         |   | 0^+02^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^23   | > 8.00     | > 7.9      | > 1.01  |   | > 2.95 | > 3.69   |
| 9^Pu, |            |            |         |   |        | x10^-01^ |
| ^2    |            |            |         |   |        |          |
| 40^Pu |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^2    | > 4.00     | > 4.0      | > 0.98  |   | >      | > 1.77   |
| 38^Pu |            |            |         |   | 7.08x1 | x10^-01^ |
|       |            |            |         |   | 0^-01^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^10   | > 1.       | > 1.       | > 1.00  |   | >      | > 7.25   |
| 3^Ru, | 80x10^+03^ | 80x10^+03^ |         |   | 1.30x1 | x10^-01^ |
| ^1    |            |            |         |   | 0^+03^ |          |
| 06^Ru |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^12   | > 2.40E+01 | >          | >       |   | >      | >        |
| 4^Sb, |            |            |         |   |        |          |
| ^1    |            |            |         |   |        |          |
| 25^Sb |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^8    | > 6.       | > 7.       | > 0.87  |   | >      | > 7.42   |
| 9^Sr, | 20x10^+02^ | 11x10^+02^ |         | \ | 4.60x1 | x10^-01^ |
| ^     |            |            |         | * | 0^+02^ |          |
| 90^Sr |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^35^S | > 1.       | > 1.       | > 1.00  |   | >      | > 8.77   |
|       | 75x10^+03^ | 75x10^+03^ |         |   | 1.53x1 | x10^-01^ |
|       |            |            |         |   | 0^+03^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 5.       | > 5.       | > 1.00  |   | >      | > 1.03   |
| 99^Tc | 30x10^+01^ | 30x10^+01^ |         |   | 5.47x1 |          |
|       |            |            |         |   | 0^+01^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^2    | > 2.00E-01 | >          | >       |   | >      | >        |
| 32^Th |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^2    | > 4.       | > 4.       | > 1.01  |   | >      | > 2.83   |
| 35^U, | 20x10^+01^ | 15x10^+01^ |         |   | 1.19x1 | x10^-01^ |
| ^     |            |            |         |   | 0^+01^ |          |
| 238^U |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| ^91^Y | > 1.20E+02 | >          | >       |   | >      | >        |
+-------+------------+------------+---------+---+--------+----------+
| ^     | > 1.       | > 1.       | > 1.00  |   | >      | > 6.43   |
| 65^Zn | 50x10^+02^ | 50x10^+02^ |         |   | 9.64x1 | x10^-01^ |
|       |            |            |         |   | 0^+01^ |          |
+-------+------------+------------+---------+---+--------+----------+
| ^9    | 1.         | > 9.       | > 0.15  |   | >      | > 5.67   |
| 5^Zr, | 45x10^+02^ | 64x10^+02^ |         | \ | 8.23x1 |          |
| ^     |            |            |         | * | 0^+02^ |          |
| 95^Nb |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
|       |            |            |         |   |        | *        |
|       |            |            |         |   |        | *Average |
|       |            |            |         |   |        | Ratio**  |
+-------+------------+------------+---------+---+--------+----------+
| Tr    |            |            |         |   |        | >        |
| itium |            |            |         |   |        | 1.28E+00 |
| G     |            |            |         |   |        |          |
| roup: |            |            |         |   |        |          |
| ^1    |            |            |         |   |        |          |
| 29^I, |            |            |         |   |        |          |
| ^1    |            |            |         |   |        |          |
| 31^I, |            |            |         |   |        |          |
| ^9    |            |            |         |   |        |          |
| 9^Tc, |            |            |         |   |        |          |
| ^35^S |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| Stro  |            |            |         |   |        | >        |
| ntium |            |            |         |   |        | 6.21E-01 |
| G     |            |            |         |   |        |          |
| roup: |            |            |         |   |        |          |
| ^10   |            |            |         |   |        |          |
| 3^Ru, |            |            |         |   |        |          |
| ^10   |            |            |         |   |        |          |
| 6^Ru, |            |            |         |   |        |          |
| ^6    |            |            |         |   |        |          |
| 0^Co, |            |            |         |   |        |          |
| ^8    |            |            |         |   |        |          |
| 9^Sr, |            |            |         |   |        |          |
| ^9    |            |            |         |   |        |          |
| 0^Sr, |            |            |         |   |        |          |
| ^9    |            |            |         |   |        |          |
| 5^Nb, |            |            |         |   |        |          |
| ^9    |            |            |         |   |        |          |
| 5^Zr, |            |            |         |   |        |          |
| ^     |            |            |         |   |        |          |
| 32^P, |            |            |         |   |        |          |
| ^6    |            |            |         |   |        |          |
| 5^Zn, |            |            |         |   |        |          |
| ^14   |            |            |         |   |        |          |
| 1^Ce, |            |            |         |   |        |          |
| ^14   |            |            |         |   |        |          |
| 4^Ce, |            |            |         |   |        |          |
| Ur    |            |            |         |   |        |          |
| anium |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+
| C     |            |            |         |   |        | >        |
| esium |            |            |         |   |        | 2.23E-01 |
| G     |            |            |         |   |        |          |
| roup: |            |            |         |   |        |          |
| ^13   |            |            |         |   |        |          |
| 4^Cs, |            |            |         |   |        |          |
| ^13   |            |            |         |   |        |          |
| 7^Cs, |            |            |         |   |        |          |
| Pluto |            |            |         |   |        |          |
| nium  |            |            |         |   |        |          |
+-------+------------+------------+---------+---+--------+----------+

**Comparison 1.** The Table 7-9 column headed "Check" compares the
unadjusted Phase III values to the Phase II screening values. A star
notation indicates that an explanation is warranted. These explanations
are provided below.

> ***^3^H.*** For tritium, the Phase II study states that both streams
> and seepage basins were included as the source of releases to the
> surface water pathway in the screening assessment. It appears from the
> data presented in the Phase II report that seepage basin data for ^3^H
> (and ^131^I) was not included in the screening assessment. This is
> indicated by the good agreement between the stream-only source terms.
> (Phase III estimates releases to streams, seepage basins, and
> containment basins.)
>
> ***^131^I.*** The entry from the Phase II screening assessment is
> Category 1 release only; i.e., release to streams only. This appears
> to be appropriate because of the short, 8-day half-life of ^131^I. Any
> substantial holdup duration would cause the seepage basin inventory to
> decay away. The Phase III point-of-release data file only includes
> releases to streams.
>
> ***^129^I.*** In the Phase II report, the 1.2 Ci entry for ^129^I in
> the table for the screening calculation was obtained by assuming that
> 3 Ci entered the seepage basin and 40% of that inventory was released
> from the basin to the stream (3 Ci \* 0.4 = 1.2 Ci). Because Phase III
> modifies all of the other radionuclide inventories using an adjustment
> factor, 3 Ci was used.
>
> ***^89^Sr, ^90^Sr.*** Although the Phase II screening value and the
> Phase III base value are different by about 15%, this appears to be
> due to an addition problem in the Phase II report. The screening
> spreadsheet value should have been about 720 Ci, based on the note in
> the spreadsheet indicating how the entry was obtained. However, this
> difference is not important. When ^89^Sr, ^90^Sr releases are applied
> in the dose reconstruction, unidentified beta-gamma releases were
> added to the ^90^Sr inventory in the amount of 218.88 Ci (before
> multiplication by the adjustment factor for ^90^Sr), this dwarfs any
> differences between the Phase III basis and screening values.
>
> ***^95^Zr, ^95^Nb.*** The Phase II report stated that all estimates of
> reported releases of ^95^Zr, ^95^Nb, and ^95^Zr, ^95^Nb were combined
> to ensure a conservative approach. However, the value used in the
> Phase II screening seems to match only the total of ^95^Zr and ^95^Nb.

**Comparison 2.** The adjustment factors, applied on the basis of K~D~,
are reflected in the ratios of the Savannah River releases (Phase III)
to the screening assessment releases (Phase II). Average ratios for
three groups of radionuclides (^3^H, ^90^Sr, and ^137^Cs groups) are
given in Table 7-9.

The radionuclides scaled to ^3^H have, on average, increased values
compared with the screening assessment inventories (+28%). The Sr scaled
nuclides have, on average, 62.1% of the screening value. The Cs-scaled
nuclides have, on average, about 20% of the screening values. This is
due to hold-up in the environment, based on use of different K~D~
values. These values compare, in general, with the adjustment factor
values for each scaling group averaged over all the years, which are
respectively: 0.749, 0.711, and 0.232. Since the ratio for each nuclide
depends on applying the annual adjustment factor for the group to the
annual releases for the radionuclide, the sum of the products depends
upon the release history of the radionuclide. This accounts for the
variability of the ratios within each group.

## Modeling Concentrations for Lower Three Runs Creek 

Unlike other streams draining the Savannah River Site, Lower Three Runs
Creek can be routinely accessed by members of the public. Hence
concentrations in the creek needed to be estimated so that potential
exposures, in accordance with the scenario specifications, could be
assessed.

### A Simple Model for Lower Three Runs Creek (Step L-3)

Similar to the approach described in Section 7.3.1 annual concentration
estimates of three radionuclides (^3^H, ^90^Sr, and ^137^Cs) for the
exposure location at Martin, SC, were computed by finding the ratio of
(1) the annual release of each of these radionuclides into Lower Three
Runs Creek and (2) the corresponding annual flow rates of Lower Three
Runs Creek as determined from USGS monitoring stations. These calculated
concentrations were then compared with concentrations of these nuclides
as measured over the years at Martin, SC.

Annual flow rates for Lower Three Runs Creek at Martin, SC, were not
available for the years 1954 through 1992, although they were available
for the years 1998 through 2001. To estimate the flow rate at Martin for
the time period of interest, the flow rate was estimated by ratio from
the flow rate at a nearby location on the creek. The process for doing
so is described in \[ATL 2003\].

Calculated Lower Three Runs Creek concentrations of ^3^H, ^90^Sr, and
^137^Cs are compared with directly measured concentrations in Figure
7-7, Figure 7-8, and Figure 7-9. This comparison shows that
concentrations in Lower Three Runs Creek based on release inventories
and flow rates disagreed with measured concentrations. This disagreement
was particularly evident for the case for ^3^H and ^137^Cs during the
early years of site operation. Par pond was built on Lower Three Runs
Creek in the 1960s and the dam would have affected flow rates and the
discharge of radionuclides to areas below the dam.

![](media/image9.wmf){width="6.41875in" height="3.926388888888889in"}

Figure 7‑7 Comparison of Calculated to Measured Concentrations of ^3^H
in Lower Three Runs Creek

![](media/image10.wmf){width="6.263194444444444in"
height="3.8243055555555556in"}

![](media/image11.wmf){width="6.211111111111111in"
height="3.821527777777778in"}Figure 7‑8 Comparison of Calculated to
Measured Concentrations of ^137^Cs in Lower Three Runs Creek

Figure 7‑9 Comparison of Calculated to Measured Concentrations of ^90^Sr
in Lower Three Runs Creek

### Use Available Measured Concentrations (Step L-4)

Because the concentrations estimated with a simple model did not agree
with measurements, for Phase III the measured concentrations (at Martin,
when possible) were used for three critical radionuclides (^137^Cs,
^90^Sr, and ^3^H) to estimate doses at Martin from releases to Lower
Three Runs Creek. This change was especially important for early years
when concentrations in the creek were high, but the estimates based on
release inventories gave excessively high concentrations.

Short of developing a physically-based model similar to that used in
Phase II for releases into the Savannah River, there was no practical
alternative to estimating concentrations from SRS releases in Lower
Three Runs Creek. Although releases through Lower Three Runs Creek would
be expected to experience the same types of loss mechanisms
(sedimentation, decay, and sorption or uptake), as other site streams,
the influence of these processes was thought to be smaller than for
other streams mainly because Lower Three Runs Creek does not pass
through the Savannah River Swamp.

The choice of using actual measured concentration in the river had the
following advantages:

1\. The inventory of radionuclides initially entered into the Lower
Three Runs Creek from the site and the annual flow rates in Lower Three
Runs Creek became non-important because radionuclide concentrations were
obtained directly from the actual measured concentrations in the
monitoring reports.

2\. The transport mechanisms were reflected in the measured
concentrations. Sediment retention, radionuclide decay, biota uptake,
periodic flooding, absorption and dilution only influenced how the
radionuclides were transported in the creek. The focus in Phase III is
to assess the exposures to these radionuclides in the river. Thus the
result of radionuclide transport was the most important issue.

3\. These three radionuclides (^137^Cs, ^90^Sr, and ^3^H), identified as
important in the Phase II Level 1screening, were measured on a regular
basis for most of the operational years.

The disadvantages include:

1\. Not all of the radionuclides of interest (radionuclides that passed
the Level 1 Screening criteria) were routinely measured.

2\. Contributions from runoff of land-deposited SRS radionuclide
releases to air and discharges from non-SRS sources, if present in any
significant fashion, could not be effectively distinguished or separated
from liquid releases to Lower Three Runs Creek from the SRS.

### Complete Data Base for Measured Concentrations (Step L-5)

Annual data for ^3^H, ^90^Sr, and ^137^Cs were compiled from a variety
of sources to make the surface water source term for Lower Three Runs
Creek.

#### ^137^Cesium and ^90^Strontium

Average annual Lower Three Runs Creek concentrations were determined for
^137^Cs, and ^90^Sr using a variety of references. For the years 1964
through 1992, annual average concentrations were determined using data
published in SRS environmental reports \[Ashley 1965, Ashley 1966,
Ashley 1967, Ashley 1968, Ashley 1969, Ashley 1970, Ashley 1971, Ashley
1972, Ashley and Zeigler 1973, Ashley and Zeigler 1974, Ashley and
Zeigler 1975, Ashley and Zeigler 1976, Ashley and Zeigler 1978a, Ashley
and Zeigler 1978b, Ashley and Zeigler 1981, Ashley 1982, Zeigler 1983,
Ashley and Zeigler 1984, Ashley 1984, DOE 1985, Zeigler 1986, Zeigler
1987, Zeigler 1988, Davis 1989, Cummins 1990\]. For the years 1954
through 1963, no environmental reports were published. For these years,
measured water concentrations in Lower Three Run Creek for nonvolatile
beta, radiostrontium, and radiocesium were obtained from Health Physics
Regional Monitoring Semiannual Reports or Semiannual Progress Reports
\[Horton 1954, Horton 1955, Alexander and Horton 1956, Horton and
Mealing 1956, Horton and Mealing 1957, Mealing 1957, Mealing and Horton
1957, Mealing 1958, Harvey 1959a, Harvey 1959b, Dupont 1959, Dupont
1960a, Dupont 1960b, Dupont 1961, Dupont 1962a, Dupont 1962b, Dupont
1963, Dupont 1964\]. In these references, measured nonvolatile beta
concentrations are available from 1954 to 1963 while radiostrontium and
radiocesium concentrations are only available from the second half year
of 1958 through 1963. Measured average concentrations in Lower Three Run
Creek at Martin were cited from these semiannual reports except for the
first half year of 1954, when no sampling location is specified.

From the second half year of 1958 to 1962, measured nonvolatile beta,
radiostrontium, and radiocesium concentrations provided the basis to
calculate average values of the ratios of the concentrations of
radiostrontium and radiocesium to the concentrations of nonvolatile beta
activity in Lower Three Runs Creek at Martin. These average values are
presented in Table 7-10. The average value of the ratio of
radiostrontium to non-volatile beta over the period 1958 through 1962 is
0.25. The average value of the ratio of radiocesium to non-volatile beta
over this time period was 0.30.

Table 7‑10 Ratio of Radiostrontium and Radiocesium to Nonvolatile\
Beta Activity in LTRC at Martin

  -------------- ---------- ------- ---------------- ------------ ------------- ---------
  Date           Location   NVB\*   Radiostrontium   Strontium-   Radiocesium   Cesium-

                            ( pCi/L ( pCi/L )        NVB Ratio    ( pCi/L )     NVB Ratio
                            )                                                   

  Jul-Dec 1958   Martin     130     28               0.22         38            0.29

  Jan-Jun 1959   Martin     74      16               0.22         19            0.26

  Jul-Dec 1959   Martin     49      11               0.22         16            0.33

  Jan-Jun 1960   Martin     20      6                0.30         8             0.40

  Jul-Dec 1960   Martin     40      9                0.23         12            0.30

  Jan-Jun 1961   Martin     24      8                0.33         8             0.33

  Jul-Dec 1961   Martin     27      5                0.19         7             0.26

  Jan-Jun 1962   Martin     50      11               0.22         11            0.22

  Jul-Dec 1962   Martin     30      9                0.30         10            0.33

  Mean           Martin                              0.25                       0.30

  Standard       Martin                              0.05                       0.05
  Deviation                                                                     

  \*NVB-                                                                        
  Non-volatile                                                                  
  beta.                                                                         
  -------------- ---------- ------- ---------------- ------------ ------------- ---------

These ratios were used to scale average annual concentrations of ^90^Sr
and ^137^Cs from average annual nonvolatile beta concentrations for the
years 1954 through 1957 when radiostrontium and radiocesium data were
not reported. The ratios were also used for 1958 because ^90^Sr and
^137^Cs data was not reported for the first half of this year. This
scaling approach is the same approach used in Phase II to determine
^137^Cs and ^90^Sr concentrations for some years in SRS streams (see
Chapter 5, p. 5-49, of Phase II).

#### Tritium

Average annual Lower Three Runs Creek concentrations were determined for
tritium for the years 1964 through 1992 using data published in SRS
environmental reports \[Ashley

1965, Ashley 1966, Ashley 1967, Ashley 1968, Ashley 1969, Ashley 1970,
Ashley 1971, Ashley 1972, Ashley and Zeigler 1973, Ashley and Zeigler
1974, Ashley and Zeigler 1975, Ashley and Zeigler 1976, Ashley and
Zeigler 1978a, Ashley and Zeigler 1978b, Ashley and Zeigler 1981, Ashley
1982, Zeigler 1983, Ashley and Zeigler 1984, Ashley 1984, DOE 1985,
Zeigler 1986, Zeigler 1987, Zeigler 1988, Davis 1989, Cummins 1990\].
For the second half of 1958 through 1963, measured tritium
concentrations in Lower Three Run Creek were obtained from Health
Physics Regional Monitoring Semiannual Reports and Semiannual Progress
Reports \[Horton 1954, Horton 1955, Alexander and Horton 1956, Horton
and Mealing 1956, Horton and Mealing 1957, Mealing 1957, Mealing and
Horton 1957, Mealing 1958, Harvey 1959a, Harvey 1959b, Dupont 1959,
Dupont 1960a, Dupont 1960b, Dupont 1961, Dupont 1962a, Dupont 1962b,
Dupont 1963, Dupont 1964\]. Measured average concentrations in Lower
Three Run Creek at Martin were cited from these semiannual reports
except for the first half year of 1954, when no sampling location is
specified.

From 1954 to 1957, tritium releases were monitored in facility effluents
but not in Lower Three Runs Creek. For these years, tritium
concentrations were estimated using information in the Phase II report.
The tritium activity discharged to Lower Three Runs Creek accounted for
approximately 5% of the total tritium entering on-site streams. This is
based on weekly measured values from 1959-1967 in the streams at the
last onsite location before the streams emptied into the Savannah River.
A documented annual creek flow rate from 1954 to 1958 could not be
located. As a result, the flow rates for these years were estimated as
discussed in [Appendix S](../Appendix_S_Revised_03_11_05_WvM.doc).

#### Interpretation of Monitoring Data in Lower Three Runs Creek

Monitoring data were used in the following manner:

If the concentration of a radionuclide of interest (i.e. tritium,
cesium, or strontium) was reported, it was included directly. The
reported concentration was used directly if the result was reported as
an annual average. When concentration data was provided on a semi-annual
basis, the average for the first and second half of the year was taken
to represent the annual average concentration. The average was used
because the environmental monitoring report only shows the average for
the monitored period, although sometimes the number of samples taken was
also reported as well as maximum and minimum concentrations for the
period.

If the environmental report or other reference showed "ND", "\<MDA",
"Below Detection Limit", or "Below Sensitivity," one half of the
reported detection limit or sensitivity was used for the indicated
period of time. Detection limits or sensitivity are generally listed in
every year's environmental report for different analytical
instrumentation, analytical parameters, and sample matrices. When a
detection limit or sensitivity is referenced for a particular water
sample, the detection limit or sensitivity of the corresponding
analytical procedure for the particular radionuclide (i.e. tritium,
radiocesium, or strontium) was used.

## References

1.  Alexander and Horton 1956. Alexander, J.M. and J.H. Horton.
    Semi-Annual Progress Report, January through June 1955. DPSP
    56-25-13. E.I. du Pont de Nemours & Company. Savannah River Plant. 5
    April 1956.

2.  Arnett 1992. M.W. Arnett, L.K. Karapatakis, A.R. Mamatey, and J.L.
    Todd. Savannah River Site Environmental Report for 1991 (U).
    WSRC-TR-92-186. Westinghouse Savannah River Company, Environmental
    Monitoring Section. Savannah River Site, Aiken, SC. 1992.

3.  Arnett 1993. M.W. Arnett, L.K. Karapatakis, A.R. Mamatey. Savannah
    River Site Environmental Report for 1992. WSRC-TR-93-075.
    Westinghouse Savannah River Company, Environmental Monitoring
    Section. Savannah River Site, Aiken, SC. 1993.

4.  Ashley 1965. Ashley, C. Environmental Monitoring, Annual
    Report, 1964. DPST-65-302. Savannah River Laboratory. E.I. Dupont de
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5.  Ashley 1966. Ashley, C. Environmental Monitoring at the Savannah
    River Plant, Annual Report -- 1965. DPST-66-302. Savannah River
    Laboratory. E.I. Dupont de Nemours & Co. Aiken, South Carolina.
    August 1966.

6.  Ashley 1967. Ashley, C. Environmental Monitoring at the Savannah
    River Plant, Annual Report -- 1966. DPST-67-302. Savannah River
    Laboratory. E.I. Dupont de Nemours & Co. Aiken, South Carolina.
    1967.

7.  Ashley 1968. Ashley, C. Environmental Monitoring at the Savannah
    River Plant, Annual Report -- 1967. DPST-68-302. Savannah River
    Laboratory. E.I. Dupont de Nemours & Co. Aiken, South Carolina.
    1968.

8.  Ashley 1969. Ashley, C. Environmental Monitoring at the Savannah
    River Plant, Annual Report -- 1968. DPST-69-302. Savannah River
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9.  Ashley 1970. Ashley, C. Environmental Monitoring at the Savannah
    River Plant, Annual Report -- 1969. DPST-70-302. Savannah River
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10. Ashley 1971. Ashley, C. Environmental Monitoring at the Savannah
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11. Ashley 1972. Ashley, C. Environmental Monitoring at the Savannah
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12. Ashley 1982. Ashley, C., C.C. Zeigler, P.A. Culp, and D.L. Smith.
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13. Ashley 1984. Ashley, C., P.C. Padezanin, C.C. Zeigler. Environmental
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24. Cummins 1991a. Cummins CL, Hetrick CS, and Martin DK, 1991.
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25. Cummins 1991b. C.L. Cummins, D.K. Martin, J.L. Todd. Savannah River
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26. Environmental Monitoring Section. Savannah River Site, Aiken, SC.
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28. DOE 1985. U.S. Department of Energy. Savannah River Plant
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29. Dupont 1959. E.I. du Pont de Nemours & Company. Health Physics
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37. Epting 1974. Epting, C.D. Memo to J.S. Murdock. Subject: Tritium
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38. Evans 1992. Evans, A.G., L.R. Bauer, J.S. Haselow, D.W. Hayes, H.L.
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54. USGS 2003c. United States Geologic Survey. USGS Flow Rate at HWY301.

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56. Zeigler 1986. Zeigler, C.C., I.B. Lawrimore, E.M. Heath, and J.E.
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57. Zeigler 1987. Zeigler, C.C., E.M. Heath, Laurie B.Taus, and J.L.
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    Nemours & Co. Aiken, South Carolina. 1987.

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[^1]: For Phase III the exposure pathways dependent on water releases of
    radionuclides include: consumption of fish taken from contaminated
    river or creek water, external exposure while occupying the
    shoreline of the contaminated river or creek, external exposure from
    swimming in the river, inadvertent ingestion of water while swimming
    in the river, and external exposure from boating on the river

[^2]: All references to GENII in this chapter refer to version 2 of
    GENII.