# Supplemental Information for Creation of Radionuclide Source Terms

This appendix presents supplemental and background information
pertaining to preparation of a source term for Phase III of the Savannah
River Site (SRS) dose reconstruction project. This appendix is composed
of five sections:

-   **Section C.1:** Summary of Phase II Screening Analysis.

-   **Section C.2:** Phase III Assumptions for Partitioning Mixed
    Isotopic Activity.

-   **Section C.3:** Phase III Adjustment Factors for Surface Water
    Transport.

-   **Section C.4:** Comparison of Phase II and Phase III Source Terms
    for Air Release.

-   **Section C.5:** Comparison of Phase II and Phase III Source Terms
    for Water Release.

Appendix B lists the source term used for Phase III. This appendix
contains tables of the annual quantities of radionuclides that were
released into air and surface water during the 39 years of production of
nuclear materials at the SRS (i.e., 1954 through 1992).

Annual quantities of 16 radionuclides released into the air are provided
in terms of 4 virtual sources. Appendix A discusses the derivation of
these four virtual sources. The four virtual sources consist of releases
to air from the following groups of SRS facilities:

1.  A-Area, M-Area, Savannah River Laboratory (SRL).

2.  F-Canyon, H-Canyon, H-Tritium Stack, F&H Seepage Basins.

3.  C-Reactor; K-Reactor; L-Reactor; Reactor Seepage Basin release
    attributable to C-, K-, and L-Reactors; D-Area; CMX-TNX.

4.  P-Reactor, R-Reactor, Reactor Seepage Basin release attributable to
    P- and R-Reactors.

Two additional tables in Appendix B list the radionuclides released into
surface water. One table lists the annual concentrations (units of
picocuries per milliliter, or pCi/mL) of 22 radionuclides discharged
into the Savannah River from all SRS surface-water sources. The second
table lists annual concentrations (pCi/mL) of three radionuclides
discharged into the Lower Three Runs Creek.

The Phase III derivation of the source term is addressed in [Chapter
5](../Chapter_05_Ready%20for%20CDC%20031405.doc) for release of
radionuclides to air, and in [Chapter
7](../Chapter_07_Ready%20for%20CDC%20031405.doc) for release of
radionuclides to surface water.

## Summary of Phase II Screening Analysis

This appendix section summarizes the screening analysis that was
performed for Phase II of the SRS Dose Reconstruction Project. A master
list of radionuclides that had been released into the air and surface
water was identified from SRS records, interviews, and workshops. In
addition, estimates were made of the average annual radionuclide release
rates. However, the master list of radionuclides was too large for
efficient analysis, and a screening assessment was performed to identify
smaller lists of key radionuclides that were the dominant contributors
to radiation dose and cancer risk. This screening assessment was
performed using a two-step method recommended by the National Council on
Radiation Protection and Measurements (NCRP) (1,2). This two-step method
featured, for both air and water, 1) a screening considering the
summation of six exposure pathways, and 2) a screening considering each
of the exposure pathways plus the sum total of all six pathways (1,2,3).

### Screening Calculations

To apply both steps of the NCRP method, it was first necessary to
determine the concentration of the radionuclide of interest in the
transporting medium (air or water). The concentration in air was
estimated by a simple dilution equation (3):

C~a~ = f Q/V (Eqn. C1-1)

Where:

> C~a~ = The atmospheric concentration of the radionuclide (becquerels
> per cubic meter \[Bq/m3\]).
>
> Q = The release rate from the facility (becquerels per second
> \[Bq/s\]).
>
> V = The volumetric flow rate of the exhaust vent (cubic meters per
> second \[m^3^/s\]).
>
> f = The fraction of time the wind blows toward the receptor
> (dimensionless).

The release rate, Q, for each radionuclide was based in Phase II on
estimates of the quantity released during a one-year period. An average
annual release was used that was calculated from compilations of SRS
references. Conservative assumptions were made concerning the flow rate
from the exhaust vent (0.3 cubic meter per second) and the fraction of
time the wind blew toward a receptor (25 percent) (3). In effect, it was
assumed for Phase II that all radionuclides were released into the air
from a single SRS stack.

The concentration in surface water was estimated as (3):

C~w~ = Wo/ Qo (Eqn. C1-2)

Where:

> C~w~ = The radionuclide concentration in the receiving surface water
> (Bq/m^3^).
>
> Qo = The flow rate of an effluent discharge at the point of release
> (m^3^/s).
>
> Wo = The radionuclide release rate at the point of release (Bq/s).

The volume of contaminated water released to all site streams was
assumed to be 7.7x10^+09^ m^3^ per year, based on site reports (3).

After the concentration of each radionuclide (i) in air or water (C~a~
~or~ ~w~) was determined, the screening value (SV~i~) for each
radionuclide was determined as (3):

SV~i~ = C ~i(a~ ~or~ ~w)~ SF~i(a~ ~or~ ~w)~ (Eqn. C1-3)

Where:

> SV~i~ = The screening value for radionuclide (i) (sievert \[Sv\] or
> millirem \[mrem\]).
>
> C ~i(a~ ~or~ ~w)~ = The concentration of radionuclide (i) in air or
> water (Bq/m^3^).
>
> SF~i(a~ ~or~ ~w)~ = The screening factor for radionuclide (i) in air
> or water (Sv per Bq/m^3^).

The screening factors were those provided in Tables B-1 and C-1 of NCRP
Report No. 123 (2) for air and surface water. For Step One of the
screening assessment, the screening factor was a term representing the
sum of the effective doses received from a set of exposure pathways
associated with radionuclides released to air or to surface water. The
following six exposure pathways were for release to air (3):

-   Inhalation of contamination in air.

-   Inhalation of contamination resuspended from soil.

-   Immersion in a plume of air.

-   Eating produce after deposition of radionuclides on the ground
    (including plant surfaces).

-   Eating meat after deposition of the radionuclides on the ground
    (including plant surfaces).

-   Drinking milk from local cows after deposition of radionuclides on
    the ground (including plant surfaces.)

The following six exposure pathways were for release to surface water
(3):

-   Drinking from the surface water.

-   Eating fish caught in the surface water.

-   Drinking milk produced on land that had been irrigated with the
    surface water.

-   Eating produce produced on land that had been irrigated with the
    surface water.

-   Eating meat produced on land that had been irrigated with the
    surface water.

-   External exposure to radionuclides deposited from the surface water
    to the ground (e.g., as from irrigation).

Table C-1 lists some of the Phase II assumptions that were used in these
exposure pathway assessments (3).

Table C‑1 Selected Assumptions Used in Screening Assessments

  ------------------- ---------------------------- ----------------------
  Exposure Pathway    Selected Parameters          Assumed Value

  Inhalation          Breathing rate               8,000 m^3^/y

                      Resuspension factor          2x10^-8^ m^-1^

  External exposure   Annual exposure to           8,000 h/y
                      contaminated ground surface  

  Ingestion           Vegetables, fruit, and grain 100 kg/y
                      consumption                  

                      Water consumption            800 L/y

                      Fish consumption             20 kg/y

                      Milk consumption             300 L/y

                      Soil ingestion               0.25 g/d

  Source: Phase II                                 
  (3).                                             
  ------------------- ---------------------------- ----------------------

For Step Two of the screening assessment, two sets of screening factors
were considered for air and for water. Each set represented the
effective dose received from each of the six exposure pathways as well
as the sum of the effective dose from all six of the exposure pathways
(3).

The product of the average concentration of each radionuclide with the
screening factor for that radionuclide was a term called the *screening
value* (units of Sv). In Step One, a single screening value for release
to air and a single screening value for release to water were calculated
for each radionuclide. In Step Two, seven screening values were
calculated for air and seven screening values were calculated for water
for each radionuclide representing each of the applicable exposure
pathways plus their respective summations. Both screening steps included
the following significant simplifications:

-   Releases were averaged over 36 years (from 1954 to 1989).

-   Concentrations at the point of release were used rather than
    concentrations plausibly at the locations of individuals.

-   Standard human behavior patterns (e.g., consumption rates of foods)
    were assumed.

-   Adult rather than age-dependent dose conversion factors were used
    (3).

For these and other reasons, the screening values thus calculated were
not plausible representations of doses to actual humans. Rather, the
screening values were highly conservative estimates meant only to
identify those radionuclides that should be considered in further
analyses.[^1]

### Screening Results for Step One of the Phase II Screening Analysis

After the calculations described in Section C.1.1 were performed, total
screening values were determined for air and water. The total screening
values are the sums of the screening values determined for each
radionuclide. Each radionuclide was ranked in importance for air and
surface-water pathways by dividing the screening value determined for
each radionuclide by the total screening value (for air or for water)
and multiplying by 100 (percent). Those radionuclides that contributed
more than 0.1 percent of the total screening values for air or for water
were identified as key radionuclides for further analysis. Table C-2 and
C-3 document the results of Step One of the Phase II screening analysis
for release to air and water, respectively (3).[^2]

Table C‑2 Results from Step One of Phase II Screening Assessment for Air

+---------------+---------+------------+----------+---------+--------+
| Radionuclide  | Es      | Con        | All      | Sc      | P      |
|               | timated | centration | Pathways | reening | ercent |
|               | Annual  | at Point   | S        | Value   | of     |
|               | Air     | of Release | creening | (Sv/y)  | Total  |
|               | Release | (B         | Factor   |         | Scr    |
|               | (Bq/y)  | q/m^3^)^†^ | (Sv/y)   |         | eening |
|               |         |            |          |         | Value  |
|               |         |            |          |         | (%)    |
+===============+=========+============+==========+=========+========+
| ^241^Am       | 2.07x   | 2.         | 1.00     | 5.48    | 0.15   |
|               | 10^+08^ | 19x10^+01^ |          |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^41^Ar        | 6.58x   | 6.         | 1.50     | 2.61x   | 7.12   |
|               | 10^+15^ | 95x10^+08^ | x10^-06^ | 10^+02^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^82^Br        | 4.11x   | 4.35       | 2.30     | 2.50x   | \<0.01 |
|               | 10^+07^ |            | x10^-04^ | 10^-04^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^14^C         | 3.08x   | 3.         | 2.60     | 2.12x   | 0.58   |
|               | 10^+12^ | 26x10^+05^ | x10^-04^ | 10^+01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^1            | 4.34x   | 4.         | 5.20     | 5.96x   | 0.02   |
| 41,144^Ce^\*^ | 10^+09^ | 58x10^+02^ | x10^-03^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^134^Cs       | 4.73x   | 5.00       | 1.30     | 1.60x   | \<0.01 |
|               | 10^+07^ |            | x10^-01^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^137^Cs       | 3.60x   | 3.         | 2.20     | 2.09x   | 0.57   |
|               | 10^+09^ | 80x10^+02^ | x10^-01^ | 10^+01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^60^Co        | 9.25x   | 9.78       | 1.70     | 4.10x   | 0.01   |
|               | 10^+07^ |            | x10^-01^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^242^Cm       | 2.36x   | 2.         | 4.00     | 2.46x   | \<0.01 |
|               | 10^+06^ | 50x10^-01^ | x10^-02^ | 10^-03^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^244^Cm       | 9.20x   | 9.72       | 5.40     | 1.29    | 0.04   |
|               | 10^+07^ |            | x10^-01^ |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^154^Eu       | 2.41x   | 2.54       | 4.20     | 2.63x   | \<0.01 |
|               | 10^+07^ |            | x10^-07^ | 10^-07^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^155^Eu       | 6.03x   | 6.         | 1.70     | 2.67x   | \<0.01 |
|               | 10^+06^ | 37x10^-01^ | x10^-08^ | 10^-09^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^3^H          | 2.52x   | 2.         | 1.90     | 1.25x   | 34.05  |
|               | 10^+16^ | 66x10^+09^ | x10^-06^ | 10^+03^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^129^I        | 5.86x   | 6.         | 5.60     | 8.54x   | 2.33   |
|               | 10^+09^ | 19x10^+02^ | x10^-01^ | 10^+01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^131^I        | 2.57x   | 2.         | 2.80     | 1.87x   | 51.20  |
|               | 10^+12^ | 68x10^+05^ | x10^-02^ | 10^+03^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^133^I        | 3.70x   | 3.         | 2.20     | 2.12x   | \<0.01 |
|               | 10^+08^ | 85x10^+01^ | x10^-04^ | 10^-03^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^135^I        | 4.81x   | 5.         | 2.50     | 3.13x   | \<0.01 |
|               | 10^+09^ | 01x10^+02^ | x10^-05^ | 10^-03^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^85^Kr        | 1.54x   | 1.         | 2.80     | 1.14    | 0.03   |
|               | 10^+16^ | 63x10^+09^ | x10^-09^ |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^85m^Kr       | 1.54x   | 1.         | 2.00     | 8.15x   | 0.02   |
|               | 10^+14^ | 63x10^+07^ | x10^-07^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^87^Kr        | 2.57x   | 2.         | 1.00     | 6.79x   | 0.02   |
|               | 10^+13^ | 72x10^+06^ | x10^-06^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^88^Kr        | 1.03x   | 1.         | 5.40     | 1.47    | 0.04   |
|               | 10^+13^ | 09x10^+06^ | x10^-06^ |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^99^Mo        | 2.36x   | 2.         | 2.30     | 1.42x   | \<0.01 |
|               | 10^+10^ | 46x10^+03^ | x10^-04^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^95^Nb        | 1.13x   | 1.         | 1.20     | 3.53x   | \<0.01 |
|               | 10^+09^ | 18x10^+02^ | x10^-03^ | 10^-02^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^185^Os       | 1.85x   | 1.         | 2.80     | 1.35x   | \<0.01 |
|               | 10^+06^ | 93x10^-01^ | x10^-03^ | 10^-04^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^2            | 3.60x   | 3.         | 1.00     | 9.51x   | 2.60   |
| 39,240^Pu^\*^ | 10^+09^ | 80x10^+02^ |          | 10^+01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^238^Pu       | 1.03x   | 1.         | 8.90     | 2.42x   | 0.66   |
|               | 10^+09^ | 09x10^+02^ | x10^-01^ | 10^+01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^103,106^Ru   | 1.75x   | 1.         | 9.60     | 4.43x   | 0.01   |
| ^\*^          | 10^+09^ | 85x10^+02^ | x10^-03^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^125^Sb       | 2.14x   | 2.23       | 1.00     | 5.57x   | \<0.01 |
|               | 10^+07^ |            | x10^-08^ | 10^-09^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^75^Se        | 1.95x   | 2.         | 1.40     | 7.12x   | \<0.01 |
|               | 10^+05^ | 03x10^-02^ | x10^-02^ | 10^-05^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^89,90^Sr     | 1.58x   | 1.         | 1.90     | 7.95    | 0.22   |
|               | 10^+09^ | 67x10^+02^ | x10^-01^ |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^99^Tc        | 1.04x   | 1.         | 1.30     | 3.56x   | \<0.01 |
|               | 10^+11^ | 10x10^+04^ | x10^-11^ | 10^-08^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^             | 1.03x   | 1.         | 3.40     | 9.23    | 0.25   |
| 235,238^U^\*^ | 10^+09^ | 09x10^+02^ | x10^-01^ |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^131m^Xe      | 1.13x   | 1.         | 1.10     | 3.29x   | \<0.01 |
|               | 10^+13^ | 19x10^+06^ | x10^-08^ | 10^-03^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^133^Xe       | 5.14x   | 5.         | 4.30     | 5.84x   | 0.02   |
|               | 10^+14^ | 43x10^+07^ | x10^-08^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| ^135^Xe       | 2.06x   | 2.         | 3.00     | 1.63    | 0.04   |
|               | 10^+14^ | 17x10^+07^ | x10^-07^ |         |        |
+---------------+---------+------------+----------+---------+--------+
| ^95^Zr,       | 3.25x   | 3.         | 4.10     | 3.52x   | 0.01   |
| ^95^Nb^\*^    | 10^+09^ | 43x10^+02^ | x10^-03^ | 10^-01^ |        |
+---------------+---------+------------+----------+---------+--------+
| Total annual  |         |            |          | 3.66x   | 100    |
| screening     |         |            |          | 10^+03^ |        |
| value from    |         |            |          |         |        |
| radionuclides |         |            |          |         |        |
| released to   |         |            |          |         |        |
| air:          |         |            |          |         |        |
+---------------+---------+------------+----------+---------+--------+
| \*^141,144^Ce |         |            |          |         |        |
| screened as   |         |            |          |         |        |
| ^144^Ce;      |         |            |          |         |        |
| ^239,240^Pu   |         |            |          |         |        |
| screened as   |         |            |          |         |        |
| ^239^Pu;      |         |            |          |         |        |
| ^103,106^Ru   |         |            |          |         |        |
| screened as   |         |            |          |         |        |
| ^106^Ru;      |         |            |          |         |        |
| ^235,238^U    |         |            |          |         |        |
| screened as   |         |            |          |         |        |
| ^235^U;       |         |            |          |         |        |
| ^95^Zr,       |         |            |          |         |        |
| ^95^Nb        |         |            |          |         |        |
| screened as   |         |            |          |         |        |
| ^95^Zr.       |         |            |          |         |        |
|               |         |            |          |         |        |
| **^†^**Before |         |            |          |         |        |
| m             |         |            |          |         |        |
| ultiplication |         |            |          |         |        |
| by the 0.25   |         |            |          |         |        |
| wind          |         |            |          |         |        |
| direction     |         |            |          |         |        |
| frequency     |         |            |          |         |        |
| factor.       |         |            |          |         |        |
|               |         |            |          |         |        |
| Source: Phase |         |            |          |         |        |
| II (3).       |         |            |          |         |        |
+---------------+---------+------------+----------+---------+--------+

Table C‑3 Results from Step One of Phase II Screening Assessment for
Surface Water

+----------------+-----------+-----------+----------+--------+-------+
| Radionuclide   | Estimated | Estimated | S        | Est    | Pe    |
|                | Annual    | Conc      | creening | imated | rcent |
|                | Surface   | entration | Factor   | Scr    | of    |
|                | Water     | at Point  | for      | eening | Total |
|                | Release   | of        | Surface  | Value  | Scre  |
|                | (Bq)      | Release   | Water    | (Sv/y) | ening |
|                |           | (Bq/m^3^) | Pathway\ |        | Value |
|                |           |           | (Sv per  |        |       |
|                |           |           | Bq/m^3^) |        |       |
+================+===========+===========+==========+========+=======+
| ^241^Am        | 1.0       | 1.3       | 2.00     | 2.67x1 | 7     |
|                | 3x10^+07^ | 3x10^-03^ | x10^-06^ | 0^-09^ | .0x10 |
|                |           |           |          |        | ^-04^ |
+----------------+-----------+-----------+----------+--------+-------+
| ^140^Ba,       | 2.2       | 2.9       | 9.50     | 2.79x1 | 0.07  |
| ^140^La^\*^    | 6x10^+11^ | 4x10^+01^ | x10^-09^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^              | 7.1       | 9.3       | 3.70     | 3.46x1 | 0.91  |
| 141,144^Ce^\*^ | 9x10^+11^ | 4x10^+01^ | x10^-08^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^244^Cm        | 8.2       | 1.0       | 9.00     | 9.61x1 | 0.03  |
|                | 2x10^+08^ | 7x10^-01^ | x10^-07^ | 0^-08^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^134^Cs        | 1.3       | 1.80      | 1.10     | 1.98x1 | 0.52  |
|                | 9x10^+10^ |           | x10^-06^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^137^Cs        | 2.0       | 2.6       | 1.10     | 2.86x1 | 75.23 |
|                | 0x10^+12^ | 0x10^+02^ | x10^-06^ | 0^-04^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^58^Co         | 2.8       | 3.6       | 1.80     | 6.56x1 | 1     |
|                | 1x10^+09^ | 4x10^-01^ | x10^-08^ | 0^-09^ | .7x10 |
|                |           |           |          |        | ^-03^ |
+----------------+-----------+-----------+----------+--------+-------+
| ^60^Co         | 8.6       | 1.1       | 6.10     | 6.84x1 | 1.80  |
|                | 3x10^+10^ | 2x10^+01^ | x10^-07^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^51^Cr         | 5.1       | 6.6       | 3.70     | 2.47x1 | 0.06  |
|                | 4x10^+12^ | 7x10^+02^ | x10^-10^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^3^H           | 1.5       | 2.0       | 1.40     | 2.80x1 | 0.74  |
|                | 4x10^+15^ | 0x10^+05^ | x10^-11^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^131^I         | 3.1       | 4.0       | 8.60     | 3.48x1 | 0.91  |
|                | 1x10^+11^ | 4x10^+01^ | x10^-08^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^129^I         | 1.2       | 1.6       | 1.40     | 2.24x1 | 0.06  |
|                | 3x10^+09^ | 0x10^-01^ | x10^-06^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^239^NP        | 1.4       | 1.9       | 1.20     | 2.31x1 | 0.06  |
|                | 8x10^+12^ | 2x10^+02^ | x10^-09^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^32^P          | 2.0       | 2.6       | 8.20     | 2.15x1 | 5.64  |
|                | 1x10^+11^ | 2x10^+01^ | x10^-07^ | 0^-05^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^              | 8.2       | 1.07      | 1.70     | 1.82x1 | 0.48  |
| 239,240^Pu^\*^ | 2x10^+09^ |           | x10^-06^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^238^Pu        | 4.1       | 5.3       | 1.50     | 8.01x1 | 0.21  |
|                | 1x10^+09^ | 4x10^-01^ | x10^-06^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^103,106^Ru    | 1.8       | 2.4       | 2.20     | 5.29x1 | 1.39  |
| ^\*^           | 5x10^+12^ | 0x10^+02^ | x10^-08^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^              | 2.4       | 3.20      | 1.20     | 3.84x1 | 0.01  |
| 124,125^Sb^\*^ | 7x10^+10^ |           | x10^-08^ | 0^-08^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^89,90^Sr ^\*^ | 6.3       | 8.2       | 4.30     | 3.56x1 | 9.35  |
|                | 7x10^+11^ | 8x10^+01^ | x10^-07^ | 0^-05^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^35^S          | 1.8       | 2.3       | 1.10     | 2.57x1 | 0.68  |
|                | 0x10^+12^ | 4x10^+02^ | x10^-08^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^99^Tc         | 5.4       | 7.07      | 6.90     | 4.88x1 | 0.13  |
|                | 5x10^+10^ |           | x10^-08^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^232^Th        | 2.0       | 2.6       | 8.90     | 2.38x1 | 0.06  |
|                | 6x10^+08^ | 7x10^-02^ | x10^-06^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| U^\*^          | 4.3       | 5.61      | 3.90     | 2.19x1 | 0.57  |
|                | 2x10^+10^ |           | x10^-07^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^91^Y          | 1.2       | 1.6       | 8.20     | 1.31x1 | 0.03  |
|                | 3x10^+11^ | 0x10^+01^ | x10^-09^ | 0^-07^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^65^Zn         | 1.5       | 2.0       | 1.30     | 2.60x1 | 0.68  |
|                | 4x10^+11^ | 0x10^+01^ | x10^-07^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| ^95^Zr, ^95^Nb | 1.4       | 1.9       | 7.40     | 1.43x1 | 0.38  |
| ^\*^           | 9x10^+11^ | 4x10^+01^ | x10^-08^ | 0^-06^ |       |
+----------------+-----------+-----------+----------+--------+-------+
| Total          |           |           |          | 3.81x1 | 100   |
| screening      |           |           |          | 0^-04^ |       |
| value from     |           |           |          |        |       |
| radionuclides  |           |           |          |        |       |
| released to    |           |           |          |        |       |
| surface water  |           |           |          |        |       |
+----------------+-----------+-----------+----------+--------+-------+
| \*^140^Ba and  |           |           |          |        |       |
| ^140^La were   |           |           |          |        |       |
| screened as    |           |           |          |        |       |
| ^140^Ba;       |           |           |          |        |       |
| ^141,144^Ce as |           |           |          |        |       |
| ^144^Ce;       |           |           |          |        |       |
| ^239,240^Pu as |           |           |          |        |       |
| ^239^Pu;       |           |           |          |        |       |
| ^103,106^Ru as |           |           |          |        |       |
| ^106^Ru;       |           |           |          |        |       |
| ^124,125^Sb as |           |           |          |        |       |
| ^125^Sb;       |           |           |          |        |       |
| ^89,90^Sr as   |           |           |          |        |       |
| ^90^Sr;        |           |           |          |        |       |
| uranium as     |           |           |          |        |       |
| ^235^U and     |           |           |          |        |       |
| ^238^U; and    |           |           |          |        |       |
| ^95^Zr, ^95^Nb |           |           |          |        |       |
| as ^95^Zr.     |           |           |          |        |       |
|                |           |           |          |        |       |
| Source: Phase  |           |           |          |        |       |
| II             |           |           |          |        |       |
| Rad            |           |           |          |        |       |
| -Screening.xls |           |           |          |        |       |
| Excel          |           |           |          |        |       |
| spreadsheet    |           |           |          |        |       |
| (3).           |           |           |          |        |       |
+----------------+-----------+-----------+----------+--------+-------+

From Table C-2, ^131^I and ^3^H contributed about 51 and 34 percent,
respectively, of the total screening value; ^41^Ar contributed about 7
percent; and ^129^I and ^239,240^Pu each contributed between 2 and 3
percent of the total screening value. From Table C-3, ^137^Cs and ^90^Sr
contributed about 75 and 9 percent of the total screening value,
respectively.

Through this process, the Phase II study identified the following key
radionuclides for release to air pathways: ^241^Am, ^41^Ar, ^14^C,
^137^Cs, ^3^H, ^129^I, ^131^I, ^238^Pu, ^239,240^Pu, ^103,106^Ru,
^89,90^Sr and U (3). The key radionuclides for release to water pathways
were ^137^Cs, ^60^Co, ^3^H, ^129^I, ^131^I, ^32^P, ^238^Pu, ^239,240^Pu,
^89^Sr, ^90^Sr, ^35^S, ^99^Tc, U, ^91^Y, ^65^Zn, and ^95^Zr, ^95^Nb (3).

### Screening Results for Step Two of the Phase II Screening Analysis

In Step Two of the Phase II screening assessment, a smaller list of
radionuclides was identified for release to air and water by a process,
summarized in Table C-4 and Table C-5 (from Phase II), that determined
the relative importance of the above key radionuclides by exposure
pathway. The percent contribution of each radionuclide to the total
screening value for each exposure pathway was the basis for ranking the
radionuclides. The radionuclides that ranked among the top three for at
least two of the seven exposure pathways were selected for detailed
source term development in the Phase II study. These radionuclides are
shown in **bold** in Tables C-4 and C-5.

Table C‑4 Results of Phase II Screening Analysis for Air Release
Screening Pathways\*

<table style="width:100%;">
<colgroup>
<col style="width: 24%" />
<col style="width: 7%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 3%" />
<col style="width: 9%" />
<col style="width: 1%" />
<col style="width: 7%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 9%" />
<col style="width: 0%" />
<col style="width: 9%" />
</colgroup>
<tbody>
<tr class="odd">
<td rowspan="2">Radionuclide<sup>†</sup></td>
<td rowspan="2"><p>All</p>
<p>Path-ways</p></td>
<td rowspan="2">Inha-lation</td>
<td colspan="6">Ingestion</td>
<td colspan="2" rowspan="2">Ground Contami-nation</td>
<td colspan="2" rowspan="2">Plume Immer-sion</td>
<td colspan="2" rowspan="2">No. of Path-ways<sup>‡</sup></td>
</tr>
<tr class="even">
<td colspan="3">Milk</td>
<td colspan="2">Produce</td>
<td>Meat</td>
</tr>
<tr class="odd">
<td><sup>241</sup>Am</td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td>0</td>
</tr>
<tr class="even">
<td><strong><sup>41</sup>Ar</strong></td>
<td><strong>X</strong></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"></td>
<td colspan="2"><strong>X</strong></td>
<td><strong>2</strong></td>
</tr>
<tr class="odd">
<td><sup>14</sup>C</td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td>0</td>
</tr>
<tr class="even">
<td><sup>137</sup>Cs</td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2">X</td>
<td colspan="2"></td>
<td>1</td>
</tr>
<tr class="odd">
<td><strong><sup>3</sup>H</strong></td>
<td><strong>X</strong></td>
<td colspan="2"><strong>X</strong></td>
<td><strong>X</strong></td>
<td colspan="2"><strong>X</strong></td>
<td colspan="3"><strong>X</strong></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td><strong>5</strong></td>
</tr>
<tr class="even">
<td><strong><sup>129</sup>I</strong></td>
<td><strong>X</strong></td>
<td colspan="2"></td>
<td><strong>X</strong></td>
<td colspan="2"></td>
<td colspan="3"><strong>X</strong></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td><strong>3</strong></td>
</tr>
<tr class="odd">
<td><strong><sup>131</sup>I</strong></td>
<td><strong>X</strong></td>
<td colspan="2"><strong>X</strong></td>
<td><strong>X</strong></td>
<td colspan="2"><strong>X</strong></td>
<td colspan="3"><strong>X</strong></td>
<td colspan="2"><strong>X</strong></td>
<td colspan="2"></td>
<td><strong>6</strong></td>
</tr>
<tr class="even">
<td><strong><sup>239,240</sup>Pu</strong></td>
<td><strong>X</strong></td>
<td colspan="2"><strong>X</strong></td>
<td></td>
<td colspan="2"><strong>X</strong></td>
<td colspan="3"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td><strong>3</strong></td>
</tr>
<tr class="odd">
<td><sup>238</sup>Pu</td>
<td></td>
<td colspan="2">X</td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td>1</td>
</tr>
<tr class="even">
<td><sup>103,106</sup>Ru</td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2">X</td>
<td colspan="2"></td>
<td>1</td>
</tr>
<tr class="odd">
<td><sup>89,90</sup>Sr</td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td>0</td>
</tr>
<tr class="even">
<td><strong>U</strong></td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"><strong>X</strong></td>
<td colspan="2"></td>
<td><strong>1<sup>§</sup></strong></td>
</tr>
<tr class="odd">
<td colspan="15"><p>*Results of Step Two in the Phase II screening
analysis. The radionuclides that ranked among the top three for at least
two of the seven exposure pathways were selected for detailed source
term development.</p>
<p><sup>†</sup>The radionuclides identified in the Step One of the Phase
II screening analysis that contributed greater than 0.1 percent of the
screening value for all exposure pathways.</p>
<p><sup>‡</sup>Number of times that a particular radionuclide ranked
high in at least two air exposure pathways.</p>
<p><sup>§</sup>Uranium was included in the detailed source development
in the Phase II study because of its concentrated use in the M-Area and
its potential chemical toxicity.</p>
<p>Source: Phase II (3).</p></td>
</tr>
</tbody>
</table>

On the other hand, although ^134^Cs, ^103,106^Ru, and ^141,144^Ce were
not included in the Phase II list of key radionuclides for surface water
pathways, it appears that they should have been included. The screening
value for these three radionuclides exceeded the 0.1-percent criterion
used for Step One of the Phase II screening assessment.

From this assessment, Table C-6 lists the radionuclides considered for
Phase III. Radionuclides cited in Phase II as aggregated quantities were
separated into separate isotopes using the assumptions and procedures
outlined in Section C.2 of this appendix.

Table C‑5 Results of Phase II Screening Analysis for Water Release
Screening Pathways\*

+-------------+--------+-----+----+----+------+----+--------+---------+
| Radi        | All    | Ing |    |    |      |    | Ground | Number  |
| onuclide^†^ | Pa     | est |    |    |      |    | Co     | of      |
|             | thways | ion |    |    |      |    | ntamin | Path    |
|             |        |     |    |    |      |    | -ation | ways^‡^ |
+-------------+--------+-----+----+----+------+----+--------+---------+
|             |        | Wa  | Fi | Mi | Pro  | Me |        |         |
|             |        | ter | sh | lk | duce | at |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^137^Cs     | **X**  | **  | *  | *  | *    | *  | **X**  | **7**   |
|             |        | X** | *X | *X | *X** | *X |        |         |
|             |        |     | ** | ** |      | ** |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| **^60^Co**  | **X**  |     |    |    |      |    | **X**  | **2**   |
+-------------+--------+-----+----+----+------+----+--------+---------+
| **^3^H**    | **X**  | **  |    |    |      |    |        | **2**   |
|             |        | X** |    |    |      |    |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^129^I      |        |     |    |    |      |    |        | 0       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| **^131^I**  | **X**  |     |    | *  |      |    |        | **2**   |
|             |        |     |    | *X |      |    |        |         |
|             |        |     |    | ** |      |    |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| **^32^P**   | **X**  | **  | *  |    |      |    |        | **3**   |
|             |        | X** | *X |    |      |    |        |         |
|             |        |     | ** |    |      |    |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^239,240^Pu |        |     |    |    |      |    |        | 0       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^238^Pu     |        |     |    |    |      |    |        | 0       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^89,90^Sr   | **X**  | **  | *  | *  | *    | *  |        | **6**   |
|             |        | X** | *X | *X | *X** | *X |        |         |
|             |        |     | ** | ** |      | ** |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^35^S       |        |     |    |    |      | X  |        | 1       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^99^Tc      |        |     |    |    | X    |    |        | 1       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| **U**       |        |     |    |    |      |    | **X**  | *       |
|             |        |     |    |    |      |    |        | *1^§^** |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^91^Y       |        |     |    |    |      |    |        | 0       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^65^Zn      | X      |     |    |    |      |    |        | 1       |
+-------------+--------+-----+----+----+------+----+--------+---------+
| ^95^Zr,     |        |     |    |    |      |    |        | 0       |
|             |        |     |    |    |      |    |        |         |
| ^95^Nb      |        |     |    |    |      |    |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+
| \*Results   |        |     |    |    |      |    |        |         |
| of Step Two |        |     |    |    |      |    |        |         |
| in the      |        |     |    |    |      |    |        |         |
| Phase II    |        |     |    |    |      |    |        |         |
| screening   |        |     |    |    |      |    |        |         |
| analysis.   |        |     |    |    |      |    |        |         |
| The         |        |     |    |    |      |    |        |         |
| ra          |        |     |    |    |      |    |        |         |
| dionuclides |        |     |    |    |      |    |        |         |
| that ranked |        |     |    |    |      |    |        |         |
| among the   |        |     |    |    |      |    |        |         |
| top three   |        |     |    |    |      |    |        |         |
| for at      |        |     |    |    |      |    |        |         |
| least two   |        |     |    |    |      |    |        |         |
| of the      |        |     |    |    |      |    |        |         |
| seven       |        |     |    |    |      |    |        |         |
| exposure    |        |     |    |    |      |    |        |         |
| pathways    |        |     |    |    |      |    |        |         |
| were        |        |     |    |    |      |    |        |         |
| selected    |        |     |    |    |      |    |        |         |
| for         |        |     |    |    |      |    |        |         |
| detailed    |        |     |    |    |      |    |        |         |
| source term |        |     |    |    |      |    |        |         |
| d           |        |     |    |    |      |    |        |         |
| evelopment. |        |     |    |    |      |    |        |         |
|             |        |     |    |    |      |    |        |         |
| **^†^**The  |        |     |    |    |      |    |        |         |
| ra          |        |     |    |    |      |    |        |         |
| dionuclides |        |     |    |    |      |    |        |         |
| identified  |        |     |    |    |      |    |        |         |
| in the Step |        |     |    |    |      |    |        |         |
| One of the  |        |     |    |    |      |    |        |         |
| Phase II    |        |     |    |    |      |    |        |         |
| screening   |        |     |    |    |      |    |        |         |
| analysis    |        |     |    |    |      |    |        |         |
| that        |        |     |    |    |      |    |        |         |
| contributed |        |     |    |    |      |    |        |         |
| greater     |        |     |    |    |      |    |        |         |
| than 0.1%   |        |     |    |    |      |    |        |         |
| of to the   |        |     |    |    |      |    |        |         |
| screening   |        |     |    |    |      |    |        |         |
| value for   |        |     |    |    |      |    |        |         |
| all         |        |     |    |    |      |    |        |         |
| exposure    |        |     |    |    |      |    |        |         |
| pathways.   |        |     |    |    |      |    |        |         |
|             |        |     |    |    |      |    |        |         |
| **          |        |     |    |    |      |    |        |         |
| ^‡^**Number |        |     |    |    |      |    |        |         |
| of times    |        |     |    |    |      |    |        |         |
| that a      |        |     |    |    |      |    |        |         |
| particular  |        |     |    |    |      |    |        |         |
| r           |        |     |    |    |      |    |        |         |
| adionuclide |        |     |    |    |      |    |        |         |
| ranked high |        |     |    |    |      |    |        |         |
| in at least |        |     |    |    |      |    |        |         |
| two surface |        |     |    |    |      |    |        |         |
| water       |        |     |    |    |      |    |        |         |
| exposure    |        |     |    |    |      |    |        |         |
| pathways.   |        |     |    |    |      |    |        |         |
|             |        |     |    |    |      |    |        |         |
| ^§^Uranium  |        |     |    |    |      |    |        |         |
| was         |        |     |    |    |      |    |        |         |
| included in |        |     |    |    |      |    |        |         |
| the         |        |     |    |    |      |    |        |         |
| detailed    |        |     |    |    |      |    |        |         |
| source      |        |     |    |    |      |    |        |         |
| development |        |     |    |    |      |    |        |         |
| in the      |        |     |    |    |      |    |        |         |
| Phase II    |        |     |    |    |      |    |        |         |
| study       |        |     |    |    |      |    |        |         |
| because of  |        |     |    |    |      |    |        |         |
| its         |        |     |    |    |      |    |        |         |
| c           |        |     |    |    |      |    |        |         |
| oncentrated |        |     |    |    |      |    |        |         |
| use in the  |        |     |    |    |      |    |        |         |
| M-Area and  |        |     |    |    |      |    |        |         |
| its         |        |     |    |    |      |    |        |         |
| potential   |        |     |    |    |      |    |        |         |
| chemical    |        |     |    |    |      |    |        |         |
| toxicity.   |        |     |    |    |      |    |        |         |
|             |        |     |    |    |      |    |        |         |
| Source:     |        |     |    |    |      |    |        |         |
| Phase II    |        |     |    |    |      |    |        |         |
| (3).        |        |     |    |    |      |    |        |         |
+-------------+--------+-----+----+----+------+----+--------+---------+

Table C‑6 Radionuclides Considered for Phase III

  ----------------- ----------------- ------------------ ----------------
  Released to the                     Released to        
  Air                                 Surface Water      

  ^3^H              ^131^I            ^3^H               ^129^I

  ^14^C             ^134,\ 137^Cs     ^32^P              ^131^I

  ^41^Ar            U                 ^35^S              ^134^Cs

  ^89,90^Sr         ^238^Pu           ^60^Co             ^137^Cs

  ^103,106^Ru       ^239,240^Pu       ^65^Zn             ^141,\ 144^Cr

  ^129^I            ^241^Am           ^95^Zr, ^95^Nb     U

                                      ^99^Tc             ^238^Pu

                                      ^103,106^Ru        ^239,240^Pu
  ----------------- ----------------- ------------------ ----------------

### Phase III Analysis of Phase II Screening Assessment

The Phase II screening assessment was reviewed for Phase III. For the
air pathways, although ^103,106^Ru was included in the list of key
radionuclides, it did not appear to actually meet the 0.1 percent
screening value criterion for Step One of the screening assessment. Its
screening value was only 0.012 percent of the total (3).

For the surface water pathways, although ^91^Y was included in the list
of key radionuclides, it did not appear to actually meet the 0.1 percent
screening value criterion for Step One of the screening assessment. Its
screening value was only 0.03 percent of the total (3). Similarly,
^129^I had a screening value of 0.05 percent, which was smaller than the
0.1 percent criterion set forth in Phase II.[^3]

## Phase III Assumptions for Partitioning Mixed Isotopic Activity 

This appendix section addresses the assumptions and procedures used in
Phase III to partition radionuclide activities reported[^4] as
aggregated quantities into individual isotopes. Partitioning assumptions
and procedures are discussed herein for:

-   ^89,90^Sr.

-   ^95^Zr, ^95^Nb.

-   ^134,\ 137^Cs.

-   U.

-   Pu.

-   ^241,243^Am.

-   Unidentified alpha and unidentified beta-gamma activity.

### ^89,90^Sr 

^89^Sr and ^90^Sr are shown as an aggregated constituent (^89,90^Sr) for
liquid released from SRL to seepage basins, liquid released from D-Area
to streams, liquid released to seepage basins in the Central Shops, and
atmospheric releases from the F- and H-Areas (4).

^89^Sr and ^90^Sr are fission products generated from the bombardment of
^235^U, ^238^U, and ^239^Pu with neutrons. The number of curies related
to the generation of ^89^Sr and ^90^Sr in the production reactors was
calculated, assuming a typical fuel element composition (5). Table C-2
summarizes the activity associated with each of these strontium isotopes
(5).

Table C‑7 Accumulated Fission Yields of Strontium Isotopes

  ------------------ ----------- -------------- -------------- -------------- -------------- --------------
                                 Activity                                                    
                                 (Curies)                                                    
                                 Remaining at                                                
                                 Various Times                                               
                                 After End of                                                
                                 Irradiation                                                 

  Isotope            Half-Life   0 Seconds      24 Hours       100 Days       200 Days       2 Years
                     or Ratio                                                                

  ^89^Sr             53.21 days  9.080x10^+7^   8.962x10^+7^   2.468x10^+7^   6.707x10^+6^   6.685x10^+3^

  ^90^Sr             28.28 years 2.219x10^+6^   2.219x10^+6^   2.204x10^+6^   2.189x10^+6^   2.113x10^+6^

  ^89^Sr/^90^Sr      Ratio       40.92          40.38          11.20          3.06           0.0032

  ^89^Sr/(^89^Sr +               98%            98%            92%            75%            0.3%
  ^90^Sr):                                                                                   

  Source: Carlton et                                                                         
  al, 1994 (5).                                                                              
  ------------------ ----------- -------------- -------------- -------------- -------------- --------------

The percentages listed in Table C-7 were used to partition ^89,90^Sr
data into ^89^Sr and ^90^Sr for the following situations:

-   [Separations Areas]{.underline}: Fuel and target elements were
    stored in the reactor basins for a nominal period of 200 days after
    completion of irradiation before being processed in F- and H-Areas
    (5). For F- and H-Areas, it was assumed that releases to the
    atmosphere occurred 200 days after completion of irradiation in the
    reactors. ^89,90^Sr atmospheric releases were therefore partitioned
    to 75 percent ^89^Sr and 25 percent ^90^Sr for these releases.

-   [Administration (A) Area]{.underline}: Environmental releases of
    ^89,90^Sr in A-Area were attributed to releases from SRL to the SRL
    seepage basins. SRL conducted research using various forms of
    uranium and plutonium. Strontium isotopes were generated as a
    result. SRL also worked with ^252^Cf for several years, and ^90^Sr
    is a daughter product of this isotope. The proportion of ^89^Sr to
    ^90^Sr could not be determined for SRL operations; therefore, it was
    assumed that all of the environmental releases attributed to
    ^89,90^Sr were ^90^Sr. This assumption was conservative because the
    ingestion effective dose conversion factors used for this study are
    larger for ^90^Sr than they are for ^89^Sr (6). So are the
    inhalation effective dose conversion factors for all lung absorption
    classes (6).

-   [D-Area]{.underline}: D-Area was used to separate light water from
    the heavy water moderator withdrawn from the reactors (6). This
    process was assumed to occur within one year after receipt of the
    moderator from the reactors. The typical delay time between removal
    of the moderator from the reactor and processing in D-Area was
    unclear; therefore, it was conservatively assumed that all of the
    environmental releases attributed to ^89,90^Sr were ^90^Sr. Again,
    ^90^Sr has larger inhalation and ingestion effective dose conversion
    factors than does ^89^Sr (6).

-   [Central Shops]{.underline}: The Central Shops (CS) were used for
    repairing equipment from the reactors and separations areas. Before
    repair, the equipment was cleaned with water that was held for decay
    before discharge to seepage basins. Discharge of the water to
    seepage basins was assumed to occur approximately two years after
    the cleaning water was used and became contaminated with the
    ^89,90^Sr. Table C-7 shows that a delay time of two years resulted
    in decay of ^89^Sr by 13.7 half-lives, or a factor of about 13,000.
    Therefore, the activity (curies) of ^89,90^Sr from Central Shops was
    attributed to ^90^Sr.

### ^95^Zr, ^95^Nb 

^95^Zr and ^95^Nb are fission products. ^95^Nb is also the daughter
product of ^95^Zr. ^95^Zr has a half-life of 64.02 days, and ^95^Nb has
a half-life of 34.98 days. Table C-8 shows that these isotopes are
initially generated as fission products in equal mass amounts (7).

Table C‑8 Accumulated Fission Yields of ^95^Zr and ^95^Nb

  --------------------------------------- ---------------- --------------
  Fission with Neutron Energy             Accumulated      
                                          Yield            

                                          ^95^Zr           ^95^Nb

  ^235^U with 0.0253 eV                   0.06             0.06

  ^235^U with 1.0 MeV                     0.06             0.06

  ^238^U with 1.0 MeV                     0.05             0.05

  ^239^Pu with 0.0253 eV                  0.05             0.05

  ^239^Pu with 1.0 MeV                    0.05             0.05

  Source: KAERI, 2003 (7).                                 
  --------------------------------------- ---------------- --------------

The activity of a radioactive isotope in terms of the number of
radioactive transformations per unit time is given as:

A = λ N (Eqn. C.2-1)

Where:

A = Activity (e.g., disintegrations per second).

λ = Radioactive decay constant (ln 2/half-life).

N = Number of atoms of a radioactive isotope.

Assuming that equal masses of ^95^Zr and ^95^Nb are produced in the
reactors and assuming that the reactors operate with the neutron thermal
energies shown in Table C-8, the initial activity of each isotope is
given by:

A~t\ =\ 0~ = λ N~o~ (Eqn. C.2-2)

Where N~o~ = The number of each isotope produced per fission event.

At any time t greater than 0, equation 2 applies:

> A(t) = λ N~o~ e^-\ λ^ (Egn. C.2-3)

Because the fission yields (the number of atoms emitted) of ^95^Zr and
^95^Nb are equal, their contribution to the gross activity of ^95^Zr,
^95^Nb is calculated to be 35 percent for ^95^Zr and 65 percent for
^95^Nb immediately upon their generation in the reactor (an estimate
based on the half-lives of the isotopes).

The half-life of the daughter is not much smaller than the half-life of
the parent isotope. The time (t~max~) at which the maximum activity of
^95^Nb will occur (based on its production from the decay of ^95^Zr) is
67 days, calculated from the following:

$t\text{max} = \frac{\text{ln}\frac{\lambda\text{Nb}}{\lambda\text{Zr}}}{\lambda\text{Nb} - \lambda Ζr}$
(Eq. C2-4)

After 67 days, the activity of ^95^Nb begins to decline at the same rate
as the decline in the activity of ^95^Zr (this is called transient
equilibrium). This ratio can be calculated by the following (8):

$\frac{A\text{Nb}}{A\text{Zr}} = \frac{\lambda\text{Nb}}{\lambda\text{Nb} - \lambda\text{Zr}} = 2\text{.}2$
(Eq. C2-5)

Based on the decay chain and the calculated ratio after the 67-day
maximum, the ratio of isotopic activity approaches a constant value
where 31 percent of the total activity is due to ^95^Zr and 69 percent
of the activity is due to ^95^Nb. These percentages are appropriate for
operations that would occur after the removal of the fuel and targets
from the reactors. By SRS process area, then, the following isotopic
fractions were used:

+-----------------------------------------------------------------------+
| Reactor areas: 35 percent ^95^Zr 65 percent ^95^Nb                    |
|                                                                       |
| All other areas: 31 percent ^95^Zr 69 percent ^95^Nb                  |
+-----------------------------------------------------------------------+

These assumed values were based on assumptions meant to best reflect
actual operating conditions and environmental releases. In determining
the potential dose to individuals from these same isotopes, Carlton and
Denham used more conservative assumptions that are based on their impact
on dose (9).

### ^134,137^Cs 

Cesium isotopes (^134^Cs and ^137^Cs) were generated at the SRS as
reactor fission products. (Technically, ^134^Cs is an activation product
because it is produced by neutrons interacting with ^133^Cs, which is a
stable fission product.) At times, ^137^Cs was separated from other
fission products for further use as an energy source. Combined
^134,\ 137^Cs is documented in environmental releases reported from
D-Area (4). ^134^Cs has a half-life of 2.06 years while ^137^Cs has a
half-life of 30.1 years. Table C-9 shows the yields of ^134^Cs and
^137^Cs resulting from fission of uranium and plutonium by neutrons of
different energies (7).

Because the yield of ^134^Cs is small compared with that of ^137^Cs,
^137^Cs was expected to contribute nearly all of the activity of
^134,\ 137^Cs. Therefore, the activity measured for ^134,\ 137^Cs was
attributed to ^137^Cs.

Table C‑9 Accumulated Fission Yields of Cesium Isotopes

  ---------------------------------------- ---------------- --------------
  Fissile with Neutron Energy              Accumulated      
                                           Yield            

                                           ^134^Cs          ^137^Cs

  ^235^U with 0.0253 eV                    1x10^-07^        0.06

  ^235^U with 1.0 MeV                      5x10^-07^        0.06

  ^238^U with 1.0 MeV                      3x10^-09^        0.06

  ^239^Pu with 0.0253 eV                   1x10^-05^        0.07

  ^239^Pu with 1.0 MeV                     1x10^-05^        0.07

  Source: KAERI, 2003 (7).                                  
  ---------------------------------------- ---------------- --------------

### Uranium 

The relative abundance of the various uranium isotopes released into air
and water was dependent on a number of factors. The primary factor was
the enrichment. Enrichment increases the relative abundance of the lower
weight isotopes (^234^U and ^235^U) and decreases the proportion of the
higher weight isotopes (^238^U). A second factor was whether the uranium
had been subjected to neutron irradiation in a reactor. Reactor
irradiation would have resulted in the production of ^236^U. While it is
fairly certain that the uranium used at SRS facilities (in particular,
the reactors and separations facilities) was irradiated in reactors,
only limited information exists concerning uranium enrichment levels.
Therefore, the analysis of the isotopic composition of uranium found in
air and water discharges is largely based on general assumptions.

However, due to two key properties of the various uranium isotopes (half
life and dose conversion), changes to the composition would not have a
substantive effect on the results of the SRS dose reconstruction.
Because all of the uranium isotopes have very long half-lives (240,000
years and longer) in comparison to the period being studied (39 years),
radioactive decay could not have had a significant effect on the
relative abundance of the isotopes after they were released. In
addition, inhalation and ingestion effect dose conversion factors for
the four uranium isotopes fall within a \~15 percent range; therefore,
the doses received from equal amounts of the different isotopes would be
about the same (6).

Until the mid-1990s, alpha-emitting radioisotopes were detected using
instrumentation that measured gross alpha activity. This gross alpha
count was attributed to a combination of (primarily) uranium and
plutonium isotopes. The fraction of the gross alpha assigned to each of
these elements varied depending on the facility or process emitting the
alpha radioactivity. In M-Area (where reactor fuel was manufactured),
alpha radioactivity was solely attributed to uranium. When the SRS
conducted dose calculations, assumptions were made about the type of
uranium present (natural, enriched, or depleted), with the corresponding
isotopic fractions used (10). This approach is used below to estimate
the curie fraction of each uranium isotope for the applicable SRS
facilities.

In Cummins et al, "U-Nat" (natural uranium) represents "^235,238^U" (4).
^235^U and ^238^U represent the majority of the mass of naturally
occurring uranium. However, it should not be assumed that all uranium
measured in environmental releases at the SRS was natural uranium.
Despite this nomenclature, uranium actually occurs in three basic forms
in the SRS environment---natural, depleted, and enriched. Natural
uranium is processed to remove ^238^U so that a higher concentration of
^235^U is achieved, thus creating enriched uranium. The enrichment
process creates a byproduct called depleted uranium. Depleted uranium
was either disposed of as a waste or reused in target materials for
producing plutonium isotopes. Evans et al provides approximate isotopic
compositions for each of these waste forms (11). Note that for enriched
uranium, two basic types of fuel were manufactured and used at the
SRS---Type M and Type F. Because it is unclear as to how much Type M
fuel versus Type F fuel was used, Table C-10 shows an average isotopic
composition for enriched fuel assuming the same mass of Type M and Type
F fuel. Note that these compositions include ^234^U and ^236^U. Although
the original data sources only reference ^235^U and ^238^U, it was
assumed for Phase III that these other uranium isotopes were also
present.

Table C‑10 Isotopic Composition of Savannah River Uranium Wastes

+---------------------+-----------+------------+-----------+-----------+
| Isotopic            | Isotope   |            |           |           |
| Composition (Weight |           |            |           |           |
| %)\*                |           |            |           |           |
+---------------------+-----------+------------+-----------+-----------+
|                     | ^234^U    | ^235^U     | ^236^U    | ^238^U    |
+---------------------+-----------+------------+-----------+-----------+
| Natural             | 0.0055    | 0.7200     | N/A^†^    | 99.2745   |
+---------------------+-----------+------------+-----------+-----------+
| Depleted            | N/A^†^    | 0.2        | N/A^†^    | 99.8      |
+---------------------+-----------+------------+-----------+-----------+
| Enriched^‡^         | 1.45      | 81.55      | 9.8       | 7.2       |
+---------------------+-----------+------------+-----------+-----------+
| Half-Life           | 2.        | 7          | 2.        | 4.        |
| (years)^§^          | 45x10^+5^ | .03x10^+8^ | 34x10^+7^ | 47x10^+9^ |
+---------------------+-----------+------------+-----------+-----------+
| ^\*^Evans et al.    |           |            |           |           |
| 1992 (11).          |           |            |           |           |
|                     |           |            |           |           |
| ^†^N/A -- data not  |           |            |           |           |
| available.          |           |            |           |           |
|                     |           |            |           |           |
| ^‡^Average of       |           |            |           |           |
| Isotopic            |           |            |           |           |
| Composition for     |           |            |           |           |
| Type M and Type F   |           |            |           |           |
| fuels.              |           |            |           |           |
|                     |           |            |           |           |
| ^§^KAERI, 2003 (7). |           |            |           |           |
+---------------------+-----------+------------+-----------+-----------+

Using the above weight percentages, the contribution to the activity for
each isotope was calculated using Equation C1-1 and presented in Table
C-11.

Table C‑11 Activity Fraction for Specific Isotopes in Uranium Wastes

  ---------------- ------------- ------------- ------------- -------------
  Activity         Isotope                                   
  Fraction (%)                                               

                   ^234^U        ^235^U        ^236^U        ^238^U

  Natural          49.49         2.25          N/A^\*^       48.26

  Depleted         N/A^\*^       1.27          N/A^\*^       98.73

  Enriched         91.73         1.79          6.45          0.03

  ^\*^N/A -- data                                            
  not available.                                             
  ---------------- ------------- ------------- ------------- -------------

The Phase III radiological assessment takes into account the isotopic
distributions listed in Table C-11 as addressed below for each major
group of SRS facilities.

-   [Reactor Areas]{.underline}: Any release of uranium in the reactor
    areas to streams and seepage basins was assumed to occur after the
    storage of spent fuel (containing enriched uranium) and target
    materials (containing depleted uranium) in spent fuel basins and
    disassembly basins (11). Basin purge water was normally discharged
    to the plant streams and seepage basins along with the reactor
    secondary cooling water. Uranium releases from the reactors to the
    atmosphere occurred due to the venting of "harps" (storage
    containers located underwater in the reactor basin which contained
    failed fuel and target elements) to the reactor stack (9). The ratio
    of enriched to depleted uranium that was used in the production
    reactors is not known and cannot be calculated. Because more
    enriched uranium (on a mass basis) than depleted uranium was
    probably used in the reactors, the activity fractions from Table
    C-11 for enriched uranium were used for environmental releases from
    the reactors.

-   [Separations Areas]{.underline}: Based on Evans et al., the F-Area
    facilities separated ^239^Pu from uranium targets primarily
    comprised of depleted uranium (11). Therefore, activity fractions in
    Table C-11 associated with depleted uranium were used for
    environmental releases from F-Area. In H-Area, ^235^U was recovered
    from enriched fuel. According to Evans et al., enrichment levels in
    H-Area fuel ranged from 1.1 percent to 94 percent ^235^U (11).
    Therefore, the activity fractions in Table C-11 associated with
    enriched uranium were used for environmental releases from H-Area.

-   [M-Area]{.underline}: Reactor fuel and targets were fabricated in
    M-Area. Atmospheric releases of uranium were very small compared to
    the releases from F-Area. These releases were in the form of natural
    and depleted uranium, although it is unclear to what proportion
    these two forms of uranium were released (11). For the purposes of
    Phase III, natural uranium activity fractions from Table C-11 were
    assumed for atmospheric releases because ^234^U is present in
    natural uranium in measurable quantities and is known to have been
    emitted from the SRS. Because depleted uranium has been found in
    stream sediments (11), the activity fractions for depleted uranium
    from Table C-11 were used for all liquid releases.

-   [A-Area (SRL)]{.underline}: SRL worked with all forms of uranium. An
    average of the activity fractions for all three forms of uranium was
    used, assuming that an equal mass of natural, depleted, and enriched
    uranium was released. This assumption resulted in the following
    percentages of uranium isotopic activity: 91.44 percent for ^234^U;
    1.8 percent for ^235^U; 6.4 percent for ^236^U; and 0.36 percent for
    ^238^U.

-   [CMX-TNX]{.underline}: Some natural uranium was used in fuel and
    target development at TNX (11). For this reason, activity fractions
    from Table C-11 for natural uranium were used for releases from
    CMX-TMX.

-   [D-Area]{.underline}: The rework of degraded moderator from reactor
    areas was the most likely source of alpha activity, which is assumed
    to be uranium (11). The moderator most likely contained a mixture of
    uranium isotopes representing both depleted and enriched uranium. To
    be consistent with the assumptions for the reactor areas, activity
    fractions from Table C-11 for enriched uranium were used for
    environmental releases from D-Area.

### Plutonium 

^238^Pu, ^239^Pu, and ^240^Pu were the primary plutonium isotopes of
interest in environmental releases at the SRS. ^239^Pu and ^240^Pu were
often reported as ^239^Pu because these two isotopes were
indistinguishable in alpha spectroscopy measurements (12). All three of
these isotopes were produced by the reactors and were present in F- and
H-Area processes. The most common form of plutonium produced at the SRS
was weapons-grade plutonium. Weapons-grade plutonium had an isotopic
composition similar to that shown in Table C-12.

Table C‑12 Isotopic Composition of Weapons-Grade Plutonium

+-----------------------------+--------+-------+-------+-------+------+
| Mass and Activity Fractions | Plu    |       |       |       |      |
|                             | tonium |       |       |       |      |
|                             | Is     |       |       |       |      |
|                             | otopes |       |       |       |      |
+-----------------------------+--------+-------+-------+-------+------+
|                             | Pu-238 | P     | P     | Pu-   | Pu   |
|                             |        | u-239 | u-240 | 241\* | -242 |
+-----------------------------+--------+-------+-------+-------+------+
| Mass Fraction               | 0      | 0.938 | 0.058 | 0     | 0.0  |
|                             | .00012 |       |       | .0035 | 0022 |
+-----------------------------+--------+-------+-------+-------+------+
| Activity Fraction (using    | 0.0047 | 0     | 0     | 0     | 0.   |
| Equation C.2-1)             |        | .1337 | .0302 | .8313 | 0000 |
+-----------------------------+--------+-------+-------+-------+------+
| \* ^241^Pu plus ^241^Am.    |        |       |       |       |      |
|                             |        |       |       |       |      |
| Source of Mass Fractions:   |        |       |       |       |      |
| Mark, 1993 (13).            |        |       |       |       |      |
+-----------------------------+--------+-------+-------+-------+------+

Two issues that were resolved were the partitioning assumptions for
activity described as combined ^239,240^Pu and activity described as
total plutonium.

Activity described in Phase II as ^239,240^Pu was assumed to be ^239^Pu.
From Table C-12, the activity fraction of ^240^Pu is about 20 percent of
that of ^239^Pu. Also, the inhalation and ingestion effective dose
conversion factors used in this report are similar for ^240^Pu to those
for ^241^Pu (6).

With respect to total plutonium, despite comprising a very small mass
fraction of weapons-grade plutonium, ^241^Pu (plus its daughter product
^241^Am) contributes approximately 83 percent of the activity (Table
C-12). ^241^Am is addressed as a separate constituent; therefore,
^241^Pu is indirectly addressed in the dose assessments. Also, the
ingestion and inhalation dose coefficients for ^241^Pu are much smaller
than those for ^238^Pu, ^239^Pu, and ^240^Pu (6). Because ^239^Pu was
the primary plutonium product at the SRS and has similar ingestion and
inhalation effective dose conversion factors as ^238^Pu and ^240^Pu (6),
all "Total Plutonium" releases to the environment were assumed to be
^239^Pu.

### ^241,243^Am 

^241^Am is a daughter product of ^241^Pu and has a half-life of 432.2
years. ^243^Am has a half-life of 7,370 years. ^241^Am and ^243^Am are
reported as "^241,243^Am" in environmental reports through 1992 because
at that time these two isotopes could not be easily distinguished in
laboratory analyses. In recent years, improved laboratory techniques
allowed for separate measurement of these two isotopes. Based on these
new techniques, it appears that any americium that appeared in SRS
environmental samples was ^241^Am. ^243^Am is used as a tracer in
laboratory analyses but does not appear to be attributable to the
original environmental samples (14).

^241^Am is an unwanted byproduct in the production of plutonium;
however, on occasion, it was isolated and used for medical applications
and well-logging sources. In addition, ^237^Np could be produced through
alpha decay of ^241^Am (15). Very small quantities of ^243^Am could have
been generated as a byproduct of producing medical isotopes; however, as
stated above, these quantities appear to be immeasurable.

For Phase III, ^241,\ 243^Am was assumed to be 100 percent ^241^Am.

### Unidentified Alpha Emitters/Unidentified Beta-Gamma Emitters

Many of the radioactive releases at the SRS were detected using gross
alpha and gross beta-gamma activity measurements. If the isotopes were
known due to process knowledge, then the measurements were assigned to
the isotopes in the environmental release reports. If the isotopes were
not known, then the environmental release reports reflected unidentified
alpha and unidentified beta + gamma measurements (11). The unknown
constituents comprising unidentified alpha and unidentified beta +
gamma measurements were most likely a combination of several isotopes.

The SRS could not assign the unidentified alpha and unidentified
beta-gamma activity measurements to specific isotopes. For this reason,
these unidentified measurements were attributed to single isotopes to
allow for conservative estimates of their dose contribution. Unknown
alpha activity was assigned to ^239^Pu, which has larger dose conversion
factors than the uranium isotopes for many of the exposure pathways (6).
In addition, ^239^Pu is one of the more prevalent plutonium isotopes at
the SRS. Other transuranic isotopes have been produced and used at the
SRS (such as ^237^Np, ^244^Cm and ^252^Cf) that have contributed to the
measurement of unidentified alpha, but these isotopes were primarily
produced during brief periods and have dose conversion factors 100 to
1,000 times smaller than ^239^Pu (6). Therefore, using ^239^Pu for
unidentified alpha values was a conservative assumption.

Many isotopes could contribute to unidentified beta-gamma activity
measurements. For conservatism, unidentified beta-gamma activity was
attributed to ^90^Sr, which was commonly found in environmental releases
throughout the SRS facilities. With a half-life of 28 years, ^90^Sr will
also remain in the environment longer than most of the other beta- and
gamma-emitting isotopes of concern.

## Adjustment Factors for Surface Water Transport to Savannah River

This section describes the method by which the uncertainties and loss
mechanisms associated with transport of radionuclides by surface water
from their points of release to the Savannah River were addressed. The
Phase II Report describes a model for estimates of release of ^3^H,
^90^Sr, and ^137^Cs to the Savannah River based on environmental
monitoring data and other parameters and processes that affect the
transport of the contaminants in surface water. For Phase III of the SRS
dose reconstruction project, the results of the Phase II model for these
three radionuclides were extrapolated to all other radionuclides of
interest.

Using the approach described herein, radionuclide concentrations in the
Savannah River at an appropriate exposure location were determined.
These concentrations were determined considering the discharge of
radionuclides from all major surface water bodies draining the SRS,
including Lower Three Runs Creek. Nonetheless, the approach described
herein was not used to determine possible radiation exposures from
public access to Lower Three Runs Creek. These exposures were determined
by another method as addressed in [Chapter
7](../Chapter_07_Ready%20for%20CDC%20031405.doc) of this report.

### Introduction

Figure C-1 depicts the major facilities releasing radionuclides to
surface water bodies on the SRS site. These facilities include:

-   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 to
reactor and separations areas seepage basins. Radionuclides released
into seepage basins were delayed in transit through ground water before
being released via surface seeps into onsite streams. This delay allowed
for radioactive decay. Surface water releases of radionuclides were
highest in the early to middle 1960's and decreased into the 1980s.

Also, Figure C-1 shows the five major onsite streams that received
radionuclides from SRS facilities. Water from Upper Three Runs Creek,
Fourmile Branch, Pen Branch, and Steel Creek passes through the Savannah
River Swamp before it discharges into the Savannah River. Water from
Lower Three Runs Creek does not pass through the swamp. Finally, Figure
C-1 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 the above 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.

![](media/image1.wmf){width="5.997222222222222in"
height="5.965972222222222in"}

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

Figure C-1 serves to point out the following difficulties inherent in
deriving a radionuclide source term for surface water:

-   Releases to surface water were not dispersed (in the sense that
    releases to air were dispersed) but eventually drained to one of the
    streams that flowed into the Savannah River.

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

-   Radionuclides discharged to streams were not immediately transported
    to locations on the Savannah River where the radionuclides could
    have been contacted by humans. Streams containing radionuclides had
    to flow for several miles before being discharged to the Savannah
    River. On the way, many radionuclides were sorbed into stream and
    swamp sediments, reducing the inventory eventually released offsite.

-   Although radionuclides released to the air could be dispersed to all
    points of the compass by wind vectors, radionuclides released to
    surface waters on the SRS were channeled by streams and rivers. This
    means that radiation exposures could only occur at well-defined
    geographic locations such as publicly accessible locations below
    site discharge points into the Savannah River.

-   Much liquid effluent was discharged over the years to seepage basins
    rather than directly to rivers. Transport of radionuclides through
    the ground water from the seepage basins to site steams was delayed
    through sorption and the usual slow ground-water flow.

-   All but one of the major onsite streams discharging radionuclides to
    the Savannah River passed through the Savannah River Swamp. Due to
    sedimentation processes characteristic of wetlands, many
    radionuclides were deposited into swamp sediments. The swamp,
    however, historically flooded about 20 percent of the time. Flooding
    tended to increase releases from the swamp to the Savannah River.

Because of these considerations, a source term was developed for Phase
III that estimated radionuclide concentrations at an exposure location
downstream of the points of radioactive discharge from all SRS streams.
These concentrations reflect the concentrations that exist **after** the
radionuclides were transported through surface water from the various
points of the SRS site release to the exposure location.[^5]

The starting point for this effort was the Phase II estimates of release
to surface water (3). This reference identified nearly two dozen key
radionuclides that had been released to surface water from SRS
facilities during the years of nuclear material production. Phase II
also developed a model for discharge into the Savannah River for three
of these radionuclides (^3^H, ^137^Cs, and ^90^Sr).

For the Phase III report, the task was to complete the estimates of
release into the Savannah River for all the other key radionuclides that
were identified in Phase II for release to surface water. This task
included the following projects:

-   Reviewing the Phase II information and supplementing its estimates
    of release to surface water for several radionuclides.

-   Partitioning radionuclides reported as aggregated quantities (e.g.,
    combined ^89^Sr and ^90^Sr) into individual isotopes consistent with
    the approach described in Section C.2 of this appendix.

-   Developing a procedure that accounted for the delay experienced by
    all key radionuclides while being transported from their various
    points of release to the Savannah River.

This Phase III procedure used a set of annual adjustment factors that
extended to other radionuclides the Phase II modeled releases of ^3^H,
^90^Sr, and ^137^Cs to the Savannah River. In this way, annual
radionuclide concentrations in the Savannah River were determined for
the 22 radionuclides listed in Table C-13.

Table C‑13 Radionuclides Considered for Savannah River Source Term

  ------------------ ------------------ ------------------- ---------------
  ^144^Ce            ^131^I             ^89^Sr              ^236^U

  ^134^Cs            ^95^Nb             ^90^Sr              ^238^U

  ^137^Cs            ^32^P              ^35^S               ^65^Zn

  ^60^Co             ^238^Pu            ^99^Tc              ^95^Zr

  ^3^H               ^239^Pu            ^234^U              

  ^129^I             ^106^Ru            ^235^U              
  ------------------ ------------------ ------------------- ---------------

### Phase II Modeled Release to Savannah River of ^3^H, ^90^Sr, and ^137^Cs

Chapter 5 of Phase II discusses in detail how 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. In addition to direct releases to onsite streams, waters
were released to seepage basins which held the waste for some period of
time. These waste waters would seep into the soil and eventually reach
the surface at the nearby streams. The southwestern edge of the SRS site
along the Savannah River consists of a wetland, which slows the flow of
water to the Savannah River as well as acts as a sink for dissolved
constituents that are sorbed or taken up by minerals, sediments, plants,
and other biota in the swamp. In addition to these physicochemical means
of reducing the releases to the Savannah River, radioactive decay
affects the concentrations of constituents that would reach the Savannah
River.

As described in Chapter 5 of the Phase II report, a relatively simple
model was used to project 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) (3). 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 (3):

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

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

-   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, when incorporated into the Phase II
model, many of the radionuclide measurement uncertainties increased the
modeled quantities discharged to the Savannah River (3).

The mathematical procedures used to estimate the transport of
radionuclides to the Savannah River considered dissolved radionuclides
as well as the transport of radionuclides attached to suspended and
bottom sediments of various sizes. The dissolved concentration at any
location was found using a mass conservation equation obtained from
Till, 1983 (16):[^6]

Where:

Cx,t = dissolved radionuclide concentration at location x and time t,

Qx,t = flow rate at location x and time t,

λ = radionuclide decay constant

∆x,t = travel time in stream (s)

∆x = change in location (m)

x = distance (m)

t = time (s)

The travel time in the stream (∆x,t) was the time it took the
radionuclide to move from Road A (its last point of measurement) to the
Savannah River. The travel time depended on the flow rate and velocity
of the particular stream, and the distance from Road A to the Savannah
River.[^7] The final activity of the radionuclide entering the Savannah
River was reduced by radioactive decay that occurred during this travel
time.

The flow rate of the dissolved radionuclide (pCi/s) was determined by
multiplying the concentration in water (pCi/m3) by the flow rate of the
water (m3/s) (3).

The concentration of radionuclides attached to sediment (Cp) was
calculated from the dissolved radionuclide concentration and the
distribution coefficient (K~d~) by (3):

Cpx,t = K~d~ Cx,t. (Eq. C.3-2)

Where Cp is in units of pCi/g and the distribution coefficient, K~d~, is
a measure of the amount of radionuclide sorbed on sediment:

  ------------ ----------------------------------- ----------------------
  K~d~ =       amount of radionuclide sorbed on    (Eq. C.3-3)
               sediment                            

               amount of radionuclide left in      
               solution                            
  ------------ ----------------------------------- ----------------------

And the sediment transport rate in water was given as (16):

ST = aQb (Eq. C.3-4)

Where ST is the sediment transport rate (units of g/s), and the
parameters (a and b) are constants estimated for each sediment size
range. For Phase II, it was assumed that a = 0.0004 and b = 3 based on
studies at the SRS (17).

From this, the flow rate of the radionuclide absorbed in transported
sediment (Ci/s) was given as the product of the concentration in
sediment (pCi/g) and the sediment transport rate (g/s). The total flow
rate was the sum of that flow rates for dissolved and suspended
radionuclides, and this sum multiplied by the number of seconds in a
year gave the yearly activity transported to the Savannah River (3).

In addition to these mathematical relationships, the model used to
project the release of these radionuclides to the Savannah River
considered periodic flooding of the Savannah River Swamp and sampling
and measurement uncertainties (3). The Savannah River Swamp flooded
about 20 percent of the time (74 days per year on the average) during
the period from 1958 to 1967. It was assumed that additional releases to
the Savannah River occurred from the swamp when flooding occurred. This
uncertainty was considered a source of bias that increased releases for
radionuclides like cesium and strontium that were retained in the swamp.
Detailed records existed for annual rainfall amounts. For most years,
releases were increased for cesium and strontium by 20 percent (with a
range of 10 to 30 percent). For years having high rainfall (e.g., 1964
and 1971), a value of 40 percent (with a range of 25 to 60 percent) was
assumed. For years having low rainfall, it was assumed that the swamp
flooded only 10 percent of the time (with a range of 5 to 15 percent)
(3).

Uncertainties associated with the release estimates were considered from
analytical errors in the measurement of flow and in sampling and
determination of radionuclide concentrations in water. (Because ^3^H was
not impacted heavily by flow through the Savannah River Swamp, sampling
and analytical uncertainties were the major sources of uncertainty in
the release estimates for ^3^H.) The effluent volume to the site streams
was monitored reasonably well by both the SRS and the USGS (3).
Estimates of error for the routine concentration measurements varied
with the radionuclide, the sample preparation, and the counting
procedure (3).

Table C-14 summarizes the factors that were considered in estimating the
releases of ^3^H, ^137^Cs, and ^90^Sr to site streams and their
discharge to the Savannah River. Several time periods were considered
due to changes in sampling procedures and analytical methods. In
addition, the retention within the swamp varied among the radionuclides
as described above (3).

Table C‑14 Factors Considered in the Uncertainty Estimates for Surface
Water Source Terms for Key Radionuclides

+---------+---------+---------+--------+-----------+--------+--------+
| Radio-  | Time    | M       | Me     | Estimated | Effect |        |
| nuclide | Period  | easured | asured | Me        | of     |        |
|         |         | E       | in     | asurement | Swamp  |        |
|         |         | ffluent | Stream | Un        |        |        |
|         |         | Release | at     | certainty |        |        |
|         |         |         | Road A |           |        |        |
+---------+---------+---------+--------+-----------+--------+--------+
|         |         |         |        |           | K~d~   | Fl     |
|         |         |         |        |           | Values | ooding |
+---------+---------+---------+--------+-----------+--------+--------+
| ^3^H    | 19      | yes     | No     | 50%       | none   | none   |
|         | 54-1957 |         |        |           |        |        |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 40%       | none   | none   |
|         | 58-1959 |         |        |           |        |        |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 25%       | none   | none   |
|         | 60-1973 |         |        |           |        |        |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 15%       | none   | none   |
|         | 74-1992 |         |        |           |        |        |
+---------+---------+---------+--------+-----------+--------+--------+
| ^137^Cs | 19      | no      | No     | 60%       | 10     | 1.1 to |
|         | 54-1958 |         |        |           | ,000\* | 1.4^†^ |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 50%       | 10     | 1.1 to |
|         | 59-1973 |         |        |           | ,000\* | 1.4^†^ |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 25%       | 10     | 1.1 to |
|         | 74-1992 |         |        |           | ,000\* | 1.4^†^ |
+---------+---------+---------+--------+-----------+--------+--------+
| ^90^Sr  | 19      | some    | No     | 60%       | 100\*  | 1.1 to |
|         | 54-1960 |         |        |           |        | 1.4^†^ |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 50%       | 100\*  | 1.1 to |
|         | 61-1973 |         |        |           |        | 1.4^†^ |
+---------+---------+---------+--------+-----------+--------+--------+
|         | 19      | yes     | Yes    | 25%       | 100\*  | 1.1 to |
|         | 74-1992 |         |        |           |        | 1.4^†^ |
+---------+---------+---------+--------+-----------+--------+--------+
| \*The   |         |         |        |           |        |        |
| median  |         |         |        |           |        |        |
| e       |         |         |        |           |        |        |
| stimate |         |         |        |           |        |        |
| is      |         |         |        |           |        |        |
| listed; |         |         |        |           |        |        |
| the     |         |         |        |           |        |        |
| range   |         |         |        |           |        |        |
| of Kd   |         |         |        |           |        |        |
| values  |         |         |        |           |        |        |
| is:     |         |         |        |           |        |        |
| cesium  |         |         |        |           |        |        |
| (50−    |         |         |        |           |        |        |
| 80,000) |         |         |        |           |        |        |
| and     |         |         |        |           |        |        |
| st      |         |         |        |           |        |        |
| rontium |         |         |        |           |        |        |
| (8      |         |         |        |           |        |        |
| −4000). |         |         |        |           |        |        |
|         |         |         |        |           |        |        |
| ^       |         |         |        |           |        |        |
| †^Based |         |         |        |           |        |        |
| on      |         |         |        |           |        |        |
| r       |         |         |        |           |        |        |
| ainfall |         |         |        |           |        |        |
| amounts |         |         |        |           |        |        |
| for     |         |         |        |           |        |        |
| each    |         |         |        |           |        |        |
| year;   |         |         |        |           |        |        |
| in      |         |         |        |           |        |        |
| g       |         |         |        |           |        |        |
| eneral, |         |         |        |           |        |        |
| the     |         |         |        |           |        |        |
| swamp   |         |         |        |           |        |        |
| f       |         |         |        |           |        |        |
| looding |         |         |        |           |        |        |
| o       |         |         |        |           |        |        |
| ccurred |         |         |        |           |        |        |
| about   |         |         |        |           |        |        |
| 20      |         |         |        |           |        |        |
| percent |         |         |        |           |        |        |
| of the  |         |         |        |           |        |        |
| time    |         |         |        |           |        |        |
| each    |         |         |        |           |        |        |
| year    |         |         |        |           |        |        |
| when    |         |         |        |           |        |        |
| the     |         |         |        |           |        |        |
| average |         |         |        |           |        |        |
| r       |         |         |        |           |        |        |
| ainfall |         |         |        |           |        |        |
| was     |         |         |        |           |        |        |
| about   |         |         |        |           |        |        |
| 47      |         |         |        |           |        |        |
| inches. |         |         |        |           |        |        |
| In      |         |         |        |           |        |        |
| 1964,   |         |         |        |           |        |        |
| very    |         |         |        |           |        |        |
| heavy   |         |         |        |           |        |        |
| r       |         |         |        |           |        |        |
| ainfall |         |         |        |           |        |        |
| (73 in) |         |         |        |           |        |        |
| and     |         |         |        |           |        |        |
| ex      |         |         |        |           |        |        |
| tensive |         |         |        |           |        |        |
| f       |         |         |        |           |        |        |
| looding |         |         |        |           |        |        |
| oc      |         |         |        |           |        |        |
| curred; |         |         |        |           |        |        |
| in      |         |         |        |           |        |        |
| 1954,   |         |         |        |           |        |        |
| it was  |         |         |        |           |        |        |
| quite   |         |         |        |           |        |        |
| dry (28 |         |         |        |           |        |        |
| in) and |         |         |        |           |        |        |
| little  |         |         |        |           |        |        |
| swamp   |         |         |        |           |        |        |
| f       |         |         |        |           |        |        |
| looding |         |         |        |           |        |        |
| oc      |         |         |        |           |        |        |
| curred. |         |         |        |           |        |        |
|         |         |         |        |           |        |        |
| Source: |         |         |        |           |        |        |
| Phase   |         |         |        |           |        |        |
| II (3). |         |         |        |           |        |        |
+---------+---------+---------+--------+-----------+--------+--------+

Measurements specific for ^137^Cs and ^90^Sr were not made in early
years. Before circa 1960, only nonvolatile beta activity was measured.
To estimate annual ^137^Cs releases for times when 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 nonvolatile beta activity measurements,
to estimate levels of ^137^Cs activity in site streams at Road A when
^137^Cs-specific measurements were not made. A similar procedure was
used for ^90^Sr. Using this information, a stochastic uncertainty
analysis of the model was performed on the three radionuclides, leading
to a range of values calculated each year for each radionuclide (3).

### Development of Savannah River Source Term for Phase III

#### Challenges 

The development of a mathematical model that accounted for the transport
of radionuclides through onsite surface water bodies until they were
discharged into the Savannah River was considered desirable. However, as
discussed in Section C.3.1., this approach contained numerous challenges
and would have been difficult 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.
Transport of released radionuclides across the SRS into the Savannah
River is neither simple nor direct.

These difficulties were apparent to the preparers of the Phase II report
who created a model that estimated releases of ^3^H, ^90^Sr, and ^137^Cs
into the Savannah River. This model started with monitoring data
measured at onsite sampling points where Road A crossed onsite streams
and projected discharge into the Savannah River considering transport of
radioactive constituents in dissolved and particulate forms, the
retention of radionuclides in the Savannah River Swamp and their release
during heavy floods, and sampling and measurement uncertainties.

The Phase II work led to consideration, for Phase III, of extending the
Phase II model to the other key radionuclides identified in the Phase II
screening assessment. Unfortunately, direct modeling similar to that
performed in the Phase II study was not possible. Because the
concentrations of most radionuclides were below detectable limits at the
Road A intersections, the basis of the Phase II model for the remaining
radionuclides was unavailable.

It was also considered unreasonable to merely assume point-of-release
information (as reported by Cummins et al \[4\] and by annual SRS
environmental reports) as a source term for discharge into the Savannah
River. This approach would have presented concentrations in the Savannah
River that were generally higher than was actually the case. The
approach would have been a conservative one, but it would not have
represented the storage of radionuclides in the swamp and their release
during floods. In addition, this approach would not have represented
measurement uncertainty.

#### Summary of Approach

In light of the challenges discussed above, a modification of the Phase
II modeling approach was used for Phase III to determine annual release
of radionuclides to the Savannah River. This approach was used to
determine annual concentrations of radionuclides in the Savannah River
from all bodies of surface water releasing radionuclides into the river.
The annual concentrations were used to determine the levels of radiation
doses and cancer risks that may have been associated with these
releases.[^8]

For Phase III, the annual concentrations of radionuclides released into
the Savannah River were determined by using annual adjustment factors as
shown in the following equation:

CSri(t) = APORi(t) / VSR(t) AFi(t) (Eqn. C.3-5)

Where:

CSri(t) = Annual concentration of radionuclide i in the Savannah River
at the designated exposure location.

APORi(t) = Activity of radionuclide i annually released into all SRS
streams seepage basins, and containment basins, as determined at the
point of release.

> VSR(t) = Annual volume of Savannah River water flowing through or past
> a designated exposure location on the Savannah River.

AFi(t) = Annual adjustment factor for radionuclide i.

Adjustment factors were developed for each year for three classes of
radionuclides encompassing different ranges of the soil-to-water
distribution coefficient (K~d~). The adjustment factors are the ratio of
the median of the Phase II modeling results for each year, respectively,
for ^3^H, ^90^Sr, and ^137^Cs, to the activity released from SRS
facilities for each year, respectively, for ^3^H, ^90^Sr, and ^137^Cs,
as determined at the points of release. That is, the adjustment factors
were calculated as follows:

  ----------- --------------------------------------- -------------------
  AFi(t) =    Annual median of Phase II modeled       (Eq. C.3-6)
              discharge to Savannah River of ^3^H,    
              ^90^Sr, or ^137^Cs (Ci)                 

              Annual ^3^H, ^90^Sr, or ^137^Cs release 
              at point of release (Ci)                
  ----------- --------------------------------------- -------------------

The adjustment factors thus calculated were used for other radionuclides
having similar K~d~s (i.e., Table C-15):

Table C‑15 Application of Adjustment Factors to Radionuclides

  -------------------------------- --------------------------------------
  Adjustment Factors Determined    Were Applied To:
  For:                             

  ^3^H                             ^3^H, ^35^S, ^99^Tc, ^129^I, ^131^I

  ^90^Sr                           ^32^P, ^60^Co, ^65^Zn, ^89^Sr, ^90^Sr,
                                   ^95^Nb, ^95^Zr, ^106^Ru, ^144^Ce, U

  ^137^Cs                          ^134^Cs, ^137^Cs, ^238^Pu, ^239^Pu
  -------------------------------- --------------------------------------

For equation C.3-5, the annual volume of the Savannah River was
determined using data from the U.S. Geological Survey (USGS). In
equation C.3-5, the annual activity of ^3^H and ^137^Cs that was
released was the same annual activity for these two radionuclides that
was assumed in the denominator of equation C.3-6. Hence, the annual
activity released into the Savannah River was the same for these
radionuclides as that modeled in Phase II. But for ^90^Sr, two different
point-of-release data files were compiled---one for developing the
annual adjustment factors and one for estimating annual discharge of
^90^Sr to the Savannah River (see Section C.4.1).

### Components of Phase III Approach 

This section discusses important components of the Phase III approach to
estimate the annual concentrations of radionuclides in the Savannah
River resulting from production of nuclear materials at the SRS.

Section C.3.4.1 briefly discusses the environmental studies, reports,
and other data used to compile point-of-release activity estimates for
the radionuclides identified in Table C-13. As part of this process, the
activities for radionuclides identified as mixtures of isotopes were
partitioned among specific isotopes.

Section C.3.4.2 provides Phase III estimates of the annual Savannah
River flow rate over the period from 1954 to 1992.

Section C.3.4.3 addresses the use of soil-to-water distribution
coefficients for grouping radionuclides for application of the
adjustment factors.

Section C.3.4.4 calculates and presents the Phase III adjustment
factors.

#### Annual Radionuclide Release at Points of Release

The principal reference used to develop the annual radionuclide
point-of-release data files was Cummins et al (4). This reference was
used for releases during the years 1954 through 1989, while SRS
environmental reports were used for the years 1990 through 1992 (18-20).
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 the following three
categories (4):

-   Category 1 - Direct releases to onsite streams.

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

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

Although one might think that the total release to site streams should
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.[^9] There appear to be at least two reasons for
this choice: (1) 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 (2) the sum of
Categories 1 and 3 should be a conservative estimate of liquid releases
to site streams.

For these reasons, the annual sums of releases from Categories 1 and 3
were chosen as representative of SRS releases to site streams. This has
two implications: (1) the adjustment factors based on modeled releases
of ^3^H, ^90^Sr, and ^137^Cs used the sums of Categories 1 and 3 as the
denominators of the adjustment factors; and (2) these adjustment factors
were applied to the sums of Categories 1 and 3 for radionuclides having
similar K~d~'s.

This decision meant that ^3^H evaporated from seepage and containment
basins was excluded from the point-of-release data file created for ^3^H
released to water. Evaporated ^3^H was included in the Phase III
atmospheric releases ([Chapter
5](../Chapter_05_Ready%20for%20CDC%20031405.doc)).

It also meant that the estimated ^137^Cs desorption from the Fourmile
Creek bed that was reported by Cummins et al (4) 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. Use of
desorption estimates would have caused double counting.

Based on these assumptions, point-of release data files were compiled
for each of the 22 radionuclides considered for release to the Savannah
River. For all radionuclides except ^90^Sr, a single data file was
constructed for each radionuclide. But two data files were constructed
for ^90^Sr: one for developing the annual adjustment factors (Equation
C.3-6) and one for estimating annual discharge of ^90^Sr to the Savannah
River (Equation C.3-5).

There were reasons why two different point-of-release data files were
complied for ^90^Sr. One reason was that the adjustment factor
determined for ^90^Sr was applied to several other radionuclides as
shown in Table C-15. Therefore, it was important to assure that any
assumptions pertaining to the annual release of ^90^Sr were not
overweight projections of other radionuclides that may have similar
K~d~'s but are otherwise dissimilar. Another reason was that much of the
release data for ^90^Sr were given as an aggregated mix of ^89^Sr and
^90^Sr, or as unidentified beta-gamma activity (see below). However,
Phase II modeled releases into the Savannah River based only on
environmental monitoring data for ^90^Sr, and not on mixed ^89,90^Sr
activity or on unidentified beta-gamma activity (3).

The data sets used to develop the two point-of-release data files for
^90^Sr are listed in Table C-16. Each data set consisted of all
indicated activity that was annually released into streams, seepage
basins, and containment basins.

Table C‑16 Data Sets Used for ^90^Sr

  ----------------------------------- -----------------------------------
  ^90^Sr Point-of-Release Data Used   ^90^Sr Point-of-Release Data Used
  to Determine ^90^Sr Discharge to    for Adjustment Factors (Equation
  Savannah River (Equation C.3-5)     C.3-6)

  ^90^Sr data                         ^90^Sr data

  ^90^Sr activity partitioned from    ^90^Sr activity partitioned from
  ^89,90^Sr data                      ^89,90^Sr data

  Unidentified beta-gamma activity    
  ----------------------------------- -----------------------------------

The Phase III assumptions and procedures for partitioning aggregated
radionuclide quantities into individual radionuclides are in Section C.2
of this appendix.

#### Savannah River Flow Rate

Annual flow rates for the Savannah River were obtained from two
sources---the United States Geological Survey (USGS) and Hayes and
Marter (21,22). For the years 1954 through 1969, and for the years 1983
through 1992, the USGS provided flow rates for the Savannah River as
measured at Burtons Ferry Bridge (U.S. Highway 301) near Millhaven,
Georgia (21). This monitoring station is located about 500 feet
downstream of the bridge on U.S. Highway 301 linking Screven County,
Georgia, with Allendale County, South Carolina. Hence, it is downstream
of all surface water discharge points into the Savannah River.

No information was available from the USGS for this monitoring station
for the years 1970 through 1982. For these years, flow rates were
projected from flow rates measured at Augusta, Georgia. The projected
flow rates were obtained from Hayes and Marter (22). These authors
determined a correlation coefficient of 0.98 when data for the Burtons
Ferry Bridge and Augusta monitoring stations were fitted to the
following equation: y = mx + b

Where:

y is the projected flow rate at Burtons Ferry Bridge.

x is the measured flow rate at Augusta.

m and b are coefficients obtained from the regression analysis (m =
1.1486 ± 0.0330 and b = -202 ± 298 (22).

The flow rates assumed for this report are listed in Table C-17 in units
of cubic feet per second (cfs). Also, the Savannah River volumes used
for this report are listed as calculated assuming 365 days per year
(except for 366 days per year every leap year), and as converted to
liters.

Table C‑17 Savannah River Flow Rates and Annual Volumes as Determined
for Burtons Ferry Bridge (U.S. Highway 301)

  ----------- ------ -- --------- -- -------------- ----- ------ -------- ------ --------- -------------- -- --------------
  Year        Leap      Annual       Water Volume         Year            Leap   Annual                      Water Volume
              Year      Mean         (Liter)                              Year   Mean                        (Liter)
                        Value\*                                                  Value\*                     
                        (cfs)                                                    (cfs)                       

  1954                  7,382        6.60x10^+12^         1974                   11,101                      9.93x10^+12^

  1955                  5,974        5.34x10^+12^         1975                   15,408                      1.38x10^+13^

  1956        L         6,309        5.66x10^+12^         1976            L      13,914                      1.25x10^+13^

  1957                  8,312        7.43x10^+12^         1977                   11,646                      1.04x10^+13^

  1958                  11,038       9.87x10^+12^         1978                   10,522                      9.41x10^+12^

  1959                  9,748        8.72x10^+12^         1979                   13,252                      1.18x10^+13^

  1960        L         13,112       1.18x10^+13^         1980            L      13,201                      1.18x10^+13^

  1961                  10,909       9.75x10^+12^         1981                   6,599                       5.90x10^+12^

  1962                  10,580       9.46x10^+12^         1982                   7,169                       6.41x10^+12^

  1963                  11,138       9.96x10^+12^         1983                   12,348                      1.10x10^+13^

  1964        L         20,497       1.84x10^+13^         1984            L      12,759                      1.14x10^+13^

  1965                  12,785       1.14x10^+13^         1985                   7,167                       6.41x10^+12^

  1966                  11,175       9.99x10^+12^         1986                   6,175                       5.52x10^+12^

  1967                  10,573       9.45x10^+12^         1987                   8,955                       8.01x10^+12^

  1968        L         9,624        8.63x10^+12^         1988            L      5,364                       4.81x10^+12^

  1969                  10,945       9.79x10^+12^         1989                   7,966                       7.12x10^+12^

  1970                  8,208        7.34x10^+12^         1990                   11,860                      1.06x10^+13^

  1971                  10,686       9.55x10^+12^         1991                   11,670                      1.04x10^+13^

  1972        L         11,235       1.01x10~+13~         1992            L      11,860                      1.06x10^+13^

  1973                                                           14,431                    1.29x10^+13^      

  \* Flow                                                                                                    
  rate from                                                                                                  
  USGS                                                                                                       
  Station ID:                                                                                                
  02197500.                                                                                                  
  ----------- ------ -- --------- -- -------------- ----- ------ -------- ------ --------- -------------- -- --------------

#### Effect of the Distribution Coefficient, K~d~, On Release Estimates

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 are 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 will be, in part, a
reflection of this retardation phenomenon and its radiological
half-life.

Even though the K~d~ values for all of the radionuclides considered in
this analysis span many orders of magnitude, the radionuclides have been
combined into three groups, based upon their K~d~ (units of milliliters
to grams \[mL/g\]):

1\. K~d~ \< 10.

2\. 10 \< K~d~ \< 1,000.

3\. K~d~ \> 1000.

These groups correspond to the nominal K~d~ values used in the Phase II
modeling: 0, 100, and 10,000 mL/g, respectively. All radionuclides
assigned to a particular group were assigned the same annual adjustment
factor calculated for that group. Table C-18 summarizes the grouping.

Table C‑18 Grouping of Radionuclides According to K~d~ Values

+--------------------+--------------+---------+-----------+----------+
| Radionuclide       | S            |         |           | Ad       |
|                    | oil-to-Water |         |           | justment |
|                    | Distribution |         |           | F        |
|                    | Coefficient, |         |           | actor^‡^ |
|                    | K~d~ (mL/g)  |         |           |          |
+--------------------+--------------+---------+-----------+----------+
|                    | Phase II     | Soil    | Swamp     |          |
|                    | Value        | Value\* | Value^†^  |          |
+--------------------+--------------+---------+-----------+----------+
| ^3^H               | **0**        | 0       |           | ^3^H     |
+--------------------+--------------+---------+-----------+----------+
| ^129,131^I         |              | 1.55    |           | ^3^H     |
+--------------------+--------------+---------+-----------+----------+
| ^99^Tc             |              | 2.49    |           | Hyd      |
|                    |              |         |           | rogent-3 |
+--------------------+--------------+---------+-----------+----------+
| ^35^S              |              | 7.5     |           | ^3^H     |
+--------------------+--------------+---------+-----------+----------+
| ^103,106^Ru        |              | 55      |           | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^60^Co             |              | 60      |           | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^89,90^Sr          | **100**      | 3,040   | 1,676     | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^95^Nb             |              | 160     |           | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^32^P              |              | 173     |           | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^65^Zn             |              | 200     |           | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^141,144^Ce        |              | 490     | 255       | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| ^95^Zr             |              | 600     |           | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| U                  |              | 1,000   | 170       | ^90^Sr   |
+--------------------+--------------+---------+-----------+----------+
| Pu                 |              | 4,100   |           | ^137^Cs  |
+--------------------+--------------+---------+-----------+----------+
| ^134,137^Cs        | **10,000**   | 59      |           | ^137^Cs  |
+--------------------+--------------+---------+-----------+----------+
| \*Source: Kaplan,  |              |         |           |          |
| 2003 (23).         |              |         |           |          |
|                    |              |         |           |          |
| **^†^**Source:     |              |         |           |          |
| Kaplan and Serkiz, |              |         |           |          |
| 2000 (24).         |              |         |           |          |
|                    |              |         |           |          |
| ^‡^The annual      |              |         |           |          |
| adjustment factors |              |         |           |          |
| are listed in      |              |         |           |          |
| Table C-20.        |              |         |           |          |
+--------------------+--------------+---------+-----------+----------+

In reviewing the K~d~'s assumed for Phase II and used to group
radionuclides by annual adjustment factor, the K~d~ assumed for ^90^Sr
appeared to be low compared to other values cited in the literature, and
the K~d~ assumed for ^137^Sc appeared to be high. K~d~ values used for
the Phase II modeling were orders of magnitude different from
site-specific values recently reported by the SRS (23). In the Phase II
modeling, a range of K~d~s having a median value of 10,000 mL/g were
used for cesium, whereas the range of values used for strontium had a
median value of 100 mL/g. Median K~d~s reported by Kaplan et al for
agricultural soils are 59 mL/g for cesium and 3,041 mL/g for strontium,
respectively (23). However, another report by Kaplan reports K~d~ values
that appear to be more appropriate for the swampy soils at issue in the
holdup of radionuclides released from the SRS. For example, a
"reasonably conservative" value cited for the strontium K~d~ in the
swamp was 1,676 mL/g (24). But, without further explanation of and
examination of the Phase II model, it is difficult to characterize the
apparent reversal of cesium and strontium K~d~ values. Other
uncertainties, such as measurement uncertainty and uncertainty in the
release from the swamp during flooding, were also considered in the
estimation of releases for ^3^H, ^90^Sr, and ^137^Cs. These
uncertainties are not the same from one radionuclide to another.

#### Adjustment Factor Development

Adjustment factors were calculated by dividing the median values of the
Phase II release model by the point-of-release inventories discussed in
Sections C.3.3.2 and C.4.2. Table C-19 lists these values and
inventories. Table C-20 lists the resultant adjustment factors.

Note that the adjustment factor initially calculated for ^3^H in year
1954 was 20.8814, which is 3 times larger than the next highest ^3^H
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 ^3^H release to the Savannah River. In 1954, 17,530
curies of ^3^H from D-Area was assumed to be released to a stream (3).
This D-Area release, however, is not documented in Cummins et al (4).

In Phase III, ^3^H release from D-Area was thought to be the only reason
for such a large adjustment factor in 1954. Consequently, the other
radionuclides in this group (i.e. ^129,131^I; ^99^Tc; and ^35^S) should
not be similarly adjusted as this could result in significant
overestimation of their true releases. Another reason for not using such
a large adjustment factor for the ^3^H group in 1954 was that the
functionality of D-Area was heavy water rework, and site effluent
release data (4) did not show that iodine, technetium, and sulfur were
released from that facility in 1954. The factor 1.0 was thus used for
the ^3^H group in 1954 to avoid overestimation of other radionuclide
releases.

Table C‑19 Phase II Median Values and Point of Release Inventories Used
for Adjustment Factors

  --------------------------------------------------------------------------------------------------
  Year     Point of                                     Phase II                      
           Release                                      Median Values                 
           Inventories                                                                
  -------- -------------- -------------- -------------- -------------- -------------- --------------
           ^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^   1.37           8.16x10^-01^   1.32x10^+04^   2.65x10^-01^   1.45x10^-01^

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

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

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

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

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

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

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

  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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  1985     3.40x10^+04^   6.23           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           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 C‑20 Liquid Effluent Adjustment Factors by Radionuclide Group and
Year

  -------------- ------------ --------- --------- ------------ --------- --------- ---------
  Year           Group 1      Group 2   Group 3   Year         Group 1   Group 2   Group 3

                 ^3^H         ^90^Sr    ^137^Cs                ^3^H      ^90^Sr    ^137^Cs

  1954           1.0000^\*^   1.0582    0.7813    1976         0.6346    2.4755    0.0163

  1955           2.2482       0.1773    0.1927    1977         0.8775    1.6271    0.0372

  1956           1.6024       0.0345    0.3224    1978         0.9418    0.3006    0.0101

  1957           0.9645       0.0079    0.0014    1979         0.6284    0.2326    0.0165

  1958           1.0004       0.0527    0.0918    1980         0.8490    3.2573    0.0423

  1959           1.2175       0.0824    0.0867    1981         0.6378    0.4416    0.0412

  1960           1.1465       0.7467    0.1744    1982         0.9787    0.5655    0.0294

  1961           1.0203       0.4284    0.2528    1983         0.7962    1.6370    0.0226

  1962           0.8954       0.6499    0.1871    1984         0.9031    4.5042    0.0200

  1963           1.0024       0.5079    0.1362    1985         0.6496    1.3263    0.0083

  1964           1.0340       0.8037    0.3964    1986         0.4893    2.5464    0.0049

  1965           0.8273       0.4443    0.4223    1987         0.7426    6.3833    0.0128

  1966           0.7190       0.7290    0.5078    1988         1.2619    5.9846    0.0456

  1967           0.8421       0.7171    0.5530    1989         4.4292    15.1968   0.8696

  1968           0.7872       0.5945    0.2933    1990         5.8478    1.2652    0.8899

  1969           0.9703       0.3495    0.2026    1991         2.5013    1.2751    0.9724

  1970           0.6430       0.5361    0.2313    1992         6.4926    1.1252    0.8279

  1971           0.9923       1.2122    0.1611                                     

  1972           0.7686       1.5321    0.0687    **Mean**     1.3325    1.7623    0.2339

  1973           0.7021       2.3023    0.0593    **Median**   0.9589    0.8037    0.0918

  1974           0.9644       4.0233    0.0866    **Max**      6.4926    15.1968   0.9724

  1975           0.9589       1.5961    0.0467    **Min**      0.4893    0.0079    0.0014

  \*Originally                                                                     
  this value was                                                                   
  calculated as                                                                    
  20.8814.                                                                         
  -------------- ------------ --------- --------- ------------ --------- --------- ---------

### Analysis of Adjustment Factor Approach

Clearly, the use of these adjustment factors provided only an
approximate estimate of the loss of contamination during transport from
the point of release to the Savannah River. Because of differences in
the chemistry and the half-lives of each radionuclide, the use of a
K~d~-based adjustment to the releases can result in over-estimation, as
well as underestimation, of the releases to the Savannah River.
Nonetheless, because the Phase II modeling considers environmental
depletion and delay, as well as measurement uncertainty, the ratio of
the modeled annual releases from the site to the recorded annual
releases from all SRS facilities represents the net effect of the
modeled factors. The resultant medians (50th percentile) from the Phase
II model were taken to be a representative means for extrapolating the
Phase II model to the radionuclides that were not modeled explicitly in
Phase II.

To check the decision to extrapolate releases to the Savannah River
using adjustment factors, two large-scale comparisons were made. First,
the Phase II modeled release data were compared to SRS point-of-release
data for the radionuclides ^3^H, ^90^Sr, and ^137^Cs. Second, Savannah
River concentrations as calculated using the Phase III extrapolated
releases were compared against available monitoring information for four
radionuclides.

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

For ^3^H, ^90^Sr, and ^137^Cs, the annual median (50th percentile) of
the Phase II Savannah River release model was compared with the annual
point-of-release estimates for these radionuclides as compiled from
Category 1 and 3 releases documented in Cummins, 1991 (4). Table C-21
summarizes the results of this comparison.

Table C‑21 Comparison of Phase II Median Releases to Savannah River with
SRS Point-of-Release Data (Categories 1 and 3 of Cummins, 1991 \[4\])

+--------------+----------------------------+--------------------------+
| Radionuclide | Range of Median of Model   | Mean, Median of Model to |
|              | to                         |                          |
|              |                            | Point-of-Release Ratios  |
|              | 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 the SRS. With a few exceptions, this was the case.
An example exception is the 1954 ratio of the estimated median release
to the total ^3^H release. (The ratio is 20.881 as noted in Section
C.4.4.) The Phase II report stated that releases were adjusted if it was
believed that reported releases were too low (3). This extremely high
ratio is probably a reflection of such an adjustment because reporting
of releases in the early years of operations was not as accurate as in
later years.

Figure C-2 presents the ratios as a function of time. As depicted on
Figure C-2, the ratios are dramatically higher during the last years of
operations. These later years may reflect that operations in general
were reduced, but there were still releases from the site. In addition,
Figure C-2 shows that the variations in time are significant. This is
due, in part, to the model that increased releases in years having large
spring floods to account for the remobilization of radionuclides stored
in previous years in the sediments and biota of the swamp. For this
reason, annual adjustment factors are preferable to an average
adjustment factor covering all years.

![](media/image2.wmf)

Figure C‑2 Annual Ratios of Phase II Median of Savannah River Release
Model to SRS Point-of-Release Data

#### Comparison of Modeled to Measured Concentrations

It is instructive to compare the modeled and measured concentrations in
the Savannah River. Two sets of modeled radionuclide concentrations were
prepared for ^3^H, ^90^Sr, ^137^Cs, and ^131^I ---the four radionuclides
for which monitoring data in the Savannah River were generally
available. These modeled concentration sets were developed using
calculated concentrations based on the following:

-   Releases to streams and migration from seepage basins.

-   Application of the Phase III model.

These comparisons are not definitive for the following reasons:

-   The measured concentrations are highly variable in time and may not
    be representative of an annual mean value.

-   The measured concentrations were frequently made at or near the
    limits of detection for the instruments used.

-   The limits of detection changed in time.

-   Only a few radionuclides were measurable for a significant portion
    of the 39-year study period.

-   As described in the Phase II report, the modeled releases are
    uncertain because the exact behavior of the sediment, swamp, river,
    streams, and biota has not been precisely modeled and probably
    cannot be precisely modeled.

Nevertheless, the modeled releases provide information that can be used
to judge the efficacy of the Phase III approach for estimating
radionuclide release to the Savannah River.

The first concentration set was comprised essentially of Category 1 and
Category 2 releases as described in Section C.4.1. These releases were
divided by the Savannah River flow (Section C.4.2) as determined at the
Burtons Ferry Bridge downstream of the SRS where Highway 301 crosses the
Savannah River. This concentration set represents essentially no
consideration of holdup in site streams and the Savannah River Swamp
before discharge to the Savannah River (no use of adjustment factors).
The second concentration set consisted of those concentrations for the
four radionuclides that were determined using the Phase III release
model described in Section C.3.3.2.

These modeled concentrations were compared against measured
concentrations in the Savannah River as obtained at the Highway 301
bridge.[^10] These measurements represent annual averages. For the years
1964 through 1992, the concentrations were obtained from SRS
environmental reports (25-49). For the years 1960 through 1963, no
environmental reports were published. For these years, measured water
concentrations were obtained from Health Physics Regional Monitoring
Semiannual Reports or Semiannual Progress Reports (50-55).

Figures C-3 and C-4 present the results of this comparison. For ^3^H
(Figure C-3), the two sets of modeled concentrations generally resulted
in smaller annual concentrations than those measured at U.S. Highway
301. The difference between the modeled and measured concentrations is
especially seen from 1960 through 1975; thereafter, agreement is good.
For many of the years between 1960 through 1975, the Phase III set of
concentrations is slightly larger than the set comprising release to
streams and migration from seepage basins.

For ^90^Sr (Figure C-4), except for the years 1961 and 1962, there
appears to be reasonable consistency between the modeled and measured
sets of concentrations. However, for many years (particularly in the
1960's), the concentrations as used in the Phase III study are larger
than those comprising the set representing release to streams and
migration from seepage basins.

For ^137^Cs (Figure C-5), except for the years 1960 through 1963, and
1978, there appears to be a reasonable level of consistency between the
Phase III model and measured concentrations. Note that the modeled
concentrations considering release to streams and migration from seepage
basins are larger than the Phase III modeled concentrations and measured
concentrations for most of the 1960's.

For ^131^I (Figure C-6), there is little difference between either set
of modeled concentrations. Both modeled sets appear to be reasonably
consistent with measured concentrations.

As discussed above, these comparisons are not definitive. Nonetheless,
these do appear to provide support to the conclusion that the modeling
approach used for the Phase III study was a reasonable way to proceed.

![](media/image3.wmf){width="5.999305555555556in"
height="3.1368055555555556in"}

Figure C‑3 ^3^H Concentrations in Savannah River

![](media/image4.wmf){width="5.997916666666667in"
height="3.2090277777777776in"}

Figure C‑4 ^90^Sr Concentrations in Savannah River

![](media/image5.wmf){width="6.002083333333333in"
height="3.248611111111111in"}

Figure C‑5 ^137^Cs Concentrations in Savannah River

![](media/image6.wmf){width="5.986805555555556in"
height="3.2493055555555554in"}

Figure C‑6 ^131^I Concentrations in Savannah River

## Comparison of Phase II and Phase III Source Terms for Air Release

The purpose of this appendix section is to record the similarities and
differences between the Phase II and Phase III estimates of release of
radionuclides to the air. Where there are significant differences, the
rationale for the differences is stated.

The Phase II report presents data about release to air at several levels
of detail. For example, the total releases for a 36-year period of SRS
operation are considered for the screening analysis described in Chapter
3, while annual releases to air for particular isotopes and facilities
are presented in Chapter 4 (3). In addition, supplementary data are
provided in Excel spreadsheets that are linked to the electronic version
of the report. Some of these spreadsheets provide releases by facility
on a weekly basis.

For Phase III of the SRS Dose Reconstruction Project, annual releases to
air are compiled for 16 radionuclides for a 39-year period of SRS
operation (see Appendix B). The radionuclides are assumed to be released
from four virtual sources as described in Appendix A. For ^3^H and
iodine isotopes, releases are complied according to the assumed chemical
form of these isotopes when released.

Data used as input to the Phase III dose and cancer risk assessment were
checked in accordance with a Quality Assurance Program. However, to
assure an appropriate degree of consistency between the Phase II report
and Phase III assumptions, the total releases for all significant
radionuclides were compared. This comparison was made more difficult by
the large amount of data in the Phase II report and the different ways
in which it was employed. For example, the total releases used in
Chapter 3 of the Phase II report to screen radionuclides were largely
raw releases based on primary sources (e.g., Cummins, 1991\[4\]).
(Section C.1 of this appendix summarizes the Phase II screening
assessment.) In Chapter 4, releases were modified for some radionuclides
to account for errors in instrumentation and problems with undersampling
releases (3). As a result, the total and annual release rates
recommended in Phase II are substantially larger than those given in the
primary references for some radionuclides (e.g., ^131^I, total
plutonium, and uranium) (3).

In the following discussion, the total releases used for the Phase II
screening assessment are compared with the total releases used for Phase
III of the SRS dose reconstruction project. The Phase II information was
obtained from the Rad-screening.xls Excel worksheet which is linked to
the electronic version of the Phase II report. After comparing the
releases, the reasons for significant differences are discussed.

Table C-22 presents the total releases to air over 39 years (1954-1992)
from the four virtual sources considered in Phase III. These total
releases have been summed from annual releases from each virtual source
using the four Excel spreadsheets that were used as input to the dose
and cancer risk assessments performed for Phase III. These spreadsheets
are AB5492A.xls, AG5492B.xls, AO5492.xls, and AQre92A.xls.

Table C-23 presents the total release into the air that was used in the
Phase II screening assessment as well as the total release used for the
Phase III source term. The Phase II totals are over 36 years while the
Phase III totals are over 39 years. Also, many of the radionuclides are
aggregated groups of radionuclides (e.g., ^89,90^Sr). The Phase II
release estimates were provided in terms of these radionuclide groups.
The totals provided in the Phase III column in Table C-23 are the sums
of the activities for the individual isotopes listed in Table C-22
(e.g., the ^89,90^Sr value \[4.7x10^+1^\]in the Phase III column in
Table C-23 is the sum of the ^89^Sr \[1.15\] and ^90^Sr \[4.58x10^+1^\])
values in Table C-22.

Table C‑22 Total 39-Year Release to Air (Ci) for Phase III Assessment by
Virtual Source

+-------------+-------------+---------+----------+---------+----------+
| Rad         | C-, K-, L-  | F- and  | A- &     | P- &    | Total    |
| ionuclide\* | Reactors,   | H-A     | M-Areas  | R-Reac  | from All |
|             | D-Area,     | reas^†^ | & SRL    | tors^†^ | Virtual  |
|             | CMX-TNX^†^  |         |          |         | Sources  |
+-------------+-------------+---------+----------+---------+----------+
| ^241^Am     | 0           | 5.88    | 2.6      | 0       | 5.8      |
|             |             | x10^-3^ | 1x10^-7^ |         | 8x10^-3^ |
+-------------+-------------+---------+----------+---------+----------+
| ^41^Ar      | 3.91x10^+6^ | 0       | 0        | 2.45    | 6.3      |
|             |             |         |          | x10^+6^ | 6x10^+6^ |
+-------------+-------------+---------+----------+---------+----------+
| ^14^C       | 1.12x10^+3^ | 1.24    | 0        | 6.12    | 2.9      |
|             |             | x10^+3^ |          | x10^+2^ | 7x10^+3^ |
+-------------+-------------+---------+----------+---------+----------+
| ^137^Cs     | 5.15x10^-5^ | 3.51    | 2.6      | 7.03    | 3.51     |
|             |             |         | 5x10^-3^ | x10^-6^ |          |
+-------------+-------------+---------+----------+---------+----------+
| ^3^H        | 5.37x10^+6^ | 8.47    | 1.8      | 1.91    | 1.5      |
|             |             | x10^+6^ | 4x10^+4^ | x10^+6^ | 8x10^+7^ |
+-------------+-------------+---------+----------+---------+----------+
| ^3^H-EL     | 0           | 9.35    | 0        | 0       | 9.3      |
|             |             | x10^+6^ |          |         | 5x10^+6^ |
+-------------+-------------+---------+----------+---------+----------+
| ^129^I-E    | 0           | 1.13    | 0        | 0       | 1.13     |
+-------------+-------------+---------+----------+---------+----------+
| ^129^I-O    | 0           | 4.54    | 0        | 0       | 4.54     |
+-------------+-------------+---------+----------+---------+----------+
| ^131^I-E    | 1.78x10^+2^ | 9.30    | 6.36     | 2.02    | 9.6      |
|             |             | x10^+3^ |          | x10^+2^ | 9x10^+3^ |
+-------------+-------------+---------+----------+---------+----------+
| ^131^I-O    | 7.61x10^+1^ | 3.92    | 0        | 8.66    | 3.9      |
|             |             | x10^+4^ |          | x10^+1^ | 4x10^+4^ |
+-------------+-------------+---------+----------+---------+----------+
| ^238^Pu     | 0           | 2.08    | 0        | 0       | 2.08     |
+-------------+-------------+---------+----------+---------+----------+
| ^239^Pu     | 1.57x10^-4^ | 1.32    | 3.4      | 4.63    | 1.3      |
|             |             | x10^+1^ | 0x10^-3^ | x10^-5^ | 2x10^+1^ |
+-------------+-------------+---------+----------+---------+----------+
| ^106^Ru     | 2.03x10^-5^ | 1.58    | 0        | 1.02    | 1.5      |
|             |             | x10^+2^ |          | x10^-5^ | 8x10^+2^ |
+-------------+-------------+---------+----------+---------+----------+
| ^89^Sr      | 0           | 1.15    | 0        | 0       | 1.15     |
+-------------+-------------+---------+----------+---------+----------+
| ^90^Sr      | 9.33x10^-2^ | 4.4     | 1.25     | 9.28    | 4.5      |
|             |             | x10^+1^ |          | x10^-2^ | 8x10^+1^ |
+-------------+-------------+---------+----------+---------+----------+
| ^234^U      | 0           | 1.13    | 1.5      | 0       | 1.13     |
|             |             |         | 9x10^-4^ |         |          |
+-------------+-------------+---------+----------+---------+----------+
| ^235^U      | 0           | 5.09    | 7.2      | 0       | 5.1      |
|             |             | x10^-2^ | 3x10^-6^ |         | 0x10^-2^ |
+-------------+-------------+---------+----------+---------+----------+
| ^236^U      | 0           | 7.93    | 0        | 0       | 7.9      |
|             |             | x10^-2^ |          |         | 3x10^-2^ |
+-------------+-------------+---------+----------+---------+----------+
| ^238^U      | 0           | 2.25    | 1        | 0       | 2.25     |
|             |             |         | .55x10-4 |         |          |
+-------------+-------------+---------+----------+---------+----------+
| \*^3^H      |             |         |          |         |          |
| means       |             |         |          |         |          |
| tritium     |             |         |          |         |          |
| released in |             |         |          |         |          |
| an oxide    |             |         |          |         |          |
| form as in  |             |         |          |         |          |
| evaporated  |             |         |          |         |          |
| water,      |             |         |          |         |          |
| while       |             |         |          |         |          |
| ^3^H-EL     |             |         |          |         |          |
| means       |             |         |          |         |          |
| tritium     |             |         |          |         |          |
| released in |             |         |          |         |          |
| an          |             |         |          |         |          |
| elemental   |             |         |          |         |          |
| form.       |             |         |          |         |          |
| Similarly   |             |         |          |         |          |
| ^129^I-E    |             |         |          |         |          |
| and         |             |         |          |         |          |
| ^131^I-E    |             |         |          |         |          |
| mean iodine |             |         |          |         |          |
| isotopes    |             |         |          |         |          |
| released in |             |         |          |         |          |
| an          |             |         |          |         |          |
| elemental   |             |         |          |         |          |
| form, while |             |         |          |         |          |
| ^129^I-O    |             |         |          |         |          |
| and         |             |         |          |         |          |
| ^131^I-O    |             |         |          |         |          |
| mean iodine |             |         |          |         |          |
| released in |             |         |          |         |          |
| an organic  |             |         |          |         |          |
| form.       |             |         |          |         |          |
|             |             |         |          |         |          |
| **^†        |             |         |          |         |          |
| ^**Includes |             |         |          |         |          |
| evaporated  |             |         |          |         |          |
| ^3^H from   |             |         |          |         |          |
| reactor and |             |         |          |         |          |
| separations |             |         |          |         |          |
| areas       |             |         |          |         |          |
| seepage     |             |         |          |         |          |
| b           |             |         |          |         |          |
| asins---see |             |         |          |         |          |
| Appendix A. |             |         |          |         |          |
+-------------+-------------+---------+----------+---------+----------+

In addition, the Phase II totals listed in Table C-23 are those obtained
from the Excel spreadsheet supporting the Phase II screening assessment
(Rad-screening.xls). The values in this spreadsheet do not in all cases
match those provided in Table 3A-2a of the Phase II report (3).

Table C-23 lists the numerical difference between the Phase III values
and Phase II values as well as the percent difference (determined as:
(Phase III -- Phase II) x 100 / Phase III). An X marking the Note column
means that further discussion is provided below.

Table C‑23 Comparison of 39-Year Phase III Total Releases (Ci) to
36-Year Phase II Releases Used for Phase II Screening Assessment (Ci)

  ---------------- ------------- ------------- ------------- -------------- ------
  Radionuclide     Phase III     Phase II      Difference    Percent        Note
                   Total from    Total Used    (Phase III -- Difference     
                   All Virtual   for Screening Phase II)     (Phase III     
                   Sources       Assessment                  --Phase II) x  
                                                             100/Phase III  

  ^241^Am          5.88x10^-3^   0             \+            \+ 100         X
                                               5.88x10^-3^                  

  ^41^Ar           6.36x10^+6^   6.40x10^+6^   \-            \- 0.638       
                                               4.00x10^+4^                  

  ^14^C            2.97x10^+3^   3.00x10^+3^   \-            \- 0.901       
                                               3.00x10^+1^                  

  ^137^Cs          3.51          3.50          \+            \+ 0.316       
                                               1.00x10^-2^                  

  ^3^H             2.51x10^+7^   2.45x10^+7^   \+            \+ 2.44        
                                               6.00x10^+5^                  

  ^129^I           5.67          5.70          \-            \- 0.448       X
                                               3.00x10^-2^                  

  ^131^I           4.91x10^+4^   2.50x10^+3^   \+            \+ 94.9        X
                                               4.66x10^+4^                  

  ^238^Pu          2.08          1.00          \+ 1.08       \+ 51.8        X

  ^239^Pu          1.32x10^+1^   3.5           \+ 9.70       73.6           X

  ^103,106^Ru ^\*^ 1.58x10+2     1.70          \+            98.9           X
                                               1.56x10^+2^                  

  ^89,90^Sr ^\*^   4.70x10+1     1.54          \+            96.7           X
                                               4.55x10^+1^                  

  U^\*^            3.51          1.00          \+ 2.51       71.5           X

  \*In the Phase                                                            
  II study,                                                                 
  ^103,106^Ru was                                                           
  screened                                                                  
  assuming that                                                             
  all activity was                                                          
  ^106^Ru.                                                                  
  ^89,90^Sr                                                                 
  activity was                                                              
  screened                                                                  
  assuming that                                                             
  all activity was                                                          
  ^90^Sr, and                                                               
  uranium activity                                                          
  was screened                                                              
  assuming that                                                             
  all activity was                                                          
  ^235^U. For                                                               
  Phase III,                                                                
  activity                                                                  
  reported as                                                               
  uranium was                                                               
  partitioned                                                               
  among the                                                                 
  uranium isotopes                                                          
  (^234^U, ^235^U,                                                          
  ^236^U, and                                                               
  ^238^U) as                                                                
  discussed in                                                              
  Section C.2 of                                                            
  this appendix.                                                            
  ---------------- ------------- ------------- ------------- -------------- ------

[^241^Am]{.underline}

The Excel spreadsheet summarizing the Phase II screening assessment
(rad_screening.xls) is confusing regarding the analysis of ^241^Am. This
spreadsheet contains several separate tables. In the Level 1 screening
table, there is no value placed in the column with the heading
"Atmospheric Release Rate from SRS," "Ci/36 y." Table C-23 reflects this
entry of zero. However, the next column in the Level 1 screening table
with the heading "Ci/y" contains the value 5.60x10^-03^, which is
converted in the next column to 2.07x10^+08^ Bq/y. This value is then
combined with a hypothetical flow rate from a stack to calculate a
concentration and then a screening value of 5.48 Sv. In the Level 2
screening table, the atmospheric release rate is given as 2.1x10^+09^
Bq/y with a corresponding screening value of 5.5 Sv. Thus, even though
the Level 2 screening release rate is a factor of 10 larger, the
screening value is the same. Because the air screening factor provided
in NCRP Report No. 123 (p. 97 of NCRP 1996 \[2\]) is 1.0 for ^241^Am for
all air release pathways, the values in the Level 1 screening table are
regarded as being consistent although the values in the Level 2
screening table have an anomalous release rate.

It appears to be more than a coincidence that the value (5.60x10^-03^
Ci) listed for Ci/y in the Level 1 screening table is only slightly
smaller than the total Phase III value over 39 years (5.88x10^-03^ Ci).
(Because the Level 1 screening was for only 36 years, we would expect
that value to be slightly smaller.) In any event, the total ^241^Am
activity assumed in the Phase III source term is consistent with data
from various site reports, including Cummins 1991 (4) and Carlton 1997
(9).

It is also interesting to note that if one divides the total Phase III
^241^Am release (5.88x10^-03^ Ci) by 39 years, one arrives at an average
release rate of approximately 1.51x10^-04^ Ci/y. This release rate is
smaller by a factor of about 37 than the value stated in the Phase II
Level 1 screening table (5.60x10^-03^). Assuming this smaller release
rate, the Level 1 screening value would also have been reduced by a
factor of 37 (i.e., 0.15 Sv). This screening value would not have
exceeded 0.1 percent of the total screening value as summed over all
radionuclides. This value of 0.1 percent was the criterion used in Phase
II to determine key radionuclides for further analysis.

[^131^I and ^129^I]{.underline}

The Phase III value is about 20 times larger for ^131^I than the Phase
II screening assessment value. The reason for this is that after
performing the screening assessment, the Phase II study further
investigated releases of ^131^I from SRS facilities. In Chapter 4-2 of
the Phase II report, it is argued that iodine releases were
underestimated due to limitations of the sampling and detection
equipment (3). A model to account for these uncertainties was
constructed and the results were quantified in a supplemental Excel
spreadsheet linked to the Phase II report
(Revised_I-131_Releases(F,H).xls). Median values (50^th^ percentile)
from these increased estimates of ^131^I releases sum to over 48,000 Ci
from the F- and H-Separations areas. These increased releases were then
added to the modified ^131^I releases from the reactors (Phase II
supplemental spreadsheet Est_I-131_Releases\_(Reactors).xls). For Phase
III, annual ^131^I release rates were used that were consistent with the
modified annual release rates developed in Chapter 4-2 of Phase II
rather than the annual release rates used in the Phase II screening
assessment. This accounts for the almost 20-fold increase in ^131^I
releases used for the Phase III calculations.

It is also interesting to note the following statement from p. 4.2-18 of
the Phase II report:

> The revised estimates of ^131^I releases have been criticized by SRS
> staff (56) because they found good agreement between environmental
> concentrations predicted using the originally reported release
> estimates for 1956 and contemporary environmental measurements. They
> also cited similar comparisons made in an earlier plant report (57).
> As was discussed above, in the 1950s, both the effluent and
> environmental concentrations of ^137^I were estimated using sampling
> media that were not highly reliable. Uncertainties in meteorological
> modeling, even for flat terrain, are on the order of a factor of 3-4
> without consideration of plume depletion. In view of the quality of
> both sets of measurements and the uncertainties involved, the
> comparisons between predicted and measured concentrations in 1956 are
> not conclusive. When Reinig made comparisons in 1959, he had no
> knowledge of the unreliability of the sampling systems.

Furthermore, it is interesting to note that the Phase II report made no
similar adjustment to the ^129^I releases, although it is expected that
some of the same instrumentation and sampling issues would have applied
to that isotope. Given the limited description of the model used in the
Phase II report, it is not clear whether the large difference in decay
constant between ^131^I (half-life is 8.04 d) and ^129^I (half-life is
1.57x10^+7^ y) accounts for the application of the correction only to
^131^I. For Phase III, the total ^129^I releases are consistent with
those recorded by the site and listed in the Phase II screening
assessment.

[^238^Pu, ^239^Pu, ^235,238^U]{.underline}

Phase III values for plutonium and uranium isotopes are larger than
comparable values from the Phase II screening assessment. After the
Phase II screening assessment was performed, plutonium and uranium
isotopes were adjusted from the screening values used in the Phase II
report based on considerations articulated in Chapter 4-4 of Phase II.
(The Phase II report accounted for uncertainties such as transmission
line losses, filter efficiencies, and acute accidental releases.) The
adjusted Phase II estimates of release of plutonium and uranium from the
F- and H-Separations areas are provided in a Phase II supplemental Excel
spreadsheet (Estimated_Source_Term.xls). These estimates are listed as
5^th^, 50^th^, and 95^th^ percentile values. The 50^th^ percentile of
the sum of total plutonium (^238^Pu and ^239^Pu) released from F- and
H-Areas over 36 years was 15.2 Ci. The 50^th^ percentile of the sum of
total uranium released from F- and H-Areas over 36 years was 3.48 Ci.

The median (50^th^ percentile) values from a Phase II supplemental Excel
spreadsheet (Estimated_Source_Term.xls) were used as the bases for Phase
III assessments of plutonium and uranium releases from the F- and
H-Separation Areas. To this plutonium and uranium activity (which
covered 1954 through 1989) was added small quantities of plutonium and
uranium reported in SRS environmental reports for the years 1990 through
1992 (18-20). These releases were then partitioned into appropriate
plutonium and uranium isotopes according to the isotopic partitioning
considerations delineated in Section C.2 of this appendix. In addition,
about 0.08 Ci of unidentified alpha activity was assumed to be ^239^Pu.

[^103,106^Ru]{.underline}

The Excel spreadsheet linked to the electronic version of Phase II
(Rad-Screening.xls) shows that the total release over 36 years as
apparently used for ^103,106^Ru was different for Steps One and Two of
the Phase II screening assessment. For Step One of the assessment (Air
Step-1 on the spreadsheet), releases over 36 years were given as 1.7 Ci
(about 6.3x10^+10^ Bq). But for Step Two of the screening assessment
(Air Step-2 on the spreadsheet), the release rate for ^103,106^Ru is
given as 1.6x10^+11^ Bq/y. If this value is multiplied by 36 (the number
of years used by Phase II for screening) and divided by 3.7x10^+10^ to
convert to Ci, the value is 155.7 Ci. This value is much larger than the
1.7 Ci listed in the Air Step-1 table on the worksheet. Furthermore,
another Phase II Excel spreadsheet linked to Chapter 4-2 of Phase II
(Ann_B-G_Part_Releases.xls) lists ^103,106^Ru releases for F- and
H-Canyons. The sum of these F- and H-Canyon releases is 158 Ci, which is
consistent with the Air Step-2 table on the Rad-Screening.xls worksheet.
Finally, Figure 4.2-15 of the Phase II report shows the time history of
ruthenium releases. The values shown in that graph are clearly
inconsistent with 1.7 Ci released. Therefore, if the entry from the Air
Step-2 table equal to 158 Ci is used to represent the Phase II value, it
will match up well with the Phase III release values.

[^89,90^Sr]{.underline}

The value compiled for ^89^Sr plus ^90^Sr for use in the Phase III dose
reconstruction is similar to the 1.5 Ci used in the Phase II screening
evaluation. However, as discussed in Section C.2 of this appendix,
unidentified beta-gamma activity for Phase III was assumed to be ^90^Sr.
This activity was added to reported releases of ^90^Sr and to ^90^Sr
activity determined from partitioning activity reported as ^89,90^Sr in
SRS reports. The additional ^90^Sr activity resulting from adding the
unidentified beta-gamma activity was about 45 Ci over the period of
consideration.

## Comparison of Phase II and Phase III Source Terms for Water Releases

The purpose of this appendix section is to record the similarities and
differences between the Phase II and Phase III estimates of release of
radionuclides to surface water. Where there are significant differences,
the rationale for the differences is stated.

The Phase II report presents data on releases at several levels of
detail. For example, total releases for a 36-year period of operation
were considered for the screening analysis described in Chapter 3;
annual values for a particular isotope and facility were presented in
Chapter 5 (3). In addition, some of the spreadsheets in the
supplementary data provided releases by facility on a weekly or monthly
basis (3). Because of the approach adopted for the Phase III dose
reconstruction, the liquid releases to two receiving bodies of water are
compiled by radionuclide. The two bodies of water represent locations
for exposure to water released radionuclides for receptors in various
receptor groups (scenarios).

The data used as input to Phase III of the SRS Dose Reconstruction
Project was checked as part of a Quality Assurance Program. However, to
assure appropriate agreement between the Phase II and Phase III reports,
the total releases for all significant radionuclides were compared.

### Background

A relatively simple model was used in Phase II to estimate the releases
to the Savannah River for ^3^H, ^90^Sr, and ^137^Cs. Because it was
necessary to consider more radionuclides than the three that had been
modeled in Phase II, a means to extend those considerations to
additional radionuclides was sought. Direct modeling similar to that
performed in Phase II was not possible because most of the
concentrations of most radionuclides were below detectable limits at the
Road A intersections. For this reason, the basis for the Phase II
modeling was unavailable. Therefore, for Phase III, the Phase II
modeling results for the three radionuclides were extrapolated to the
additional radionuclides. Adjustment factors were developed for each
year for three classes of radionuclides encompassing different ranges of
K~d~. These adjustment factors are the ratio of: (1) the median of the
Phase II modeling results for each year, respectively, for ^3^H, ^90^Sr,
and ^137^Cs to (2) the annual activity released from SRS facilities into
surface water, respectively, for ^3^H, ^90^Sr, and ^137^Cs as determined
at the point of release.

Liquid releases from the site were placed into the following three
categories (4):

-   Category 1 - Direct releases to onsite streams.

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

-   Category 3 - Direct releases to seepage basins.

For Phase III, the annual sum of the Categories 1 and 3 releases were
chosen as being representative of SRS releases to site streams. This had
two implications: (1) the adjustment factors based on modeled releases
of ^3^H, ^90^Sr, and ^137^Cs used the sum of Categories 1 and 3 as the
denominator of the adjustment factor, and (2) these adjustment factors
were applied to the sum of Categories 1 and 3 for radionuclides having
similar K~d~s. Although these annual liquid releases for Categories 1
and 3 were derived from fundamental data (e.g., Cummins, 1991 \[4\]),
they are consistent with the Phase II report.

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

Because of the approach adopted for Phase III of the SRS Dose
Reconstruction Project, the releases to streams, seepage basins, and
containment basins were compiled by radionuclide as point-of-release
estimates. Two desirable checks place the Phase III analysis in context:
(1) comparison of the point-of-release estimates used in Phase III to
the screening values used in Phase II, and (2) comparison of the
extrapolated releases used in Phase III to the screening assessment
values used in Phase II. Table C-24 makes these comparisons.

Table C‑24 Comparison of Phase III Releases with Phase II Screening
Assumptions

  ------------------------------------------------------------------------------------------------------------------------------------------------------
  **Releases from                   **Sum of 36-year                                                 **Sum of                             
  Phase II                          Releases from                                                    36-year                              
  Water-Step 1                      Cummins Data -                                                   Phase III                            
  Screening**                       Basis for Phase                                                  Releases                             
                                    III                                                              to                                   
                                    Point-of-Release                                                 Savannah                             
                                    Estimates**                                                      River**                              
  ------------------ -------------- ------------------ -------------- ----------- ------ ----------- ---------- -------------- ---------- --------------
  **Radionuclide**   **Surface                         **Cat. 1+Cat.  **Ratio,           **Eval.**              **Phase III               **Ratio, Phase
                     Water Release                     3 Unless       Screening                                 Release to                III River
                     from SRS                          Otherwise      to Phase                                  River (Ci/36              Release to
                     (Ci/36 yr)**                      Noted (Ci/36   III Basis**                               yr)**                     Screening**
                                                       yr)**                                                                              

  Am-241             1.00E-02                                                                                                             

  Ba, La-140         2.20E+02                                                                                                             

  ^141,144^Ce        7.00x10^+02^                      7.08x10^+02^   0.99                                      4.58x10^+02^              6.54x10^-01^

  Cm-244             8.00E-01                                                                                                             

  ^134^Cs            1.35x10^+01^                      1.35x10^+01^   1.00                                      2.87                      2.13x10^-01^

  ^137^Cs            1.95x10^+03^                      1.95x10^+03^   1.00                                      2.57x10^+02^              1.32x10^-01^

  Co-58              2.73E+00                                                                                                             

  ^60^Co             8.40x10^+01^                      8.42x10^+01^   1.00                                      5.40x10^+01^              6.43x10^-01^

  Cr-51              5.00E+03                                                                                                             

  ^3^H               1.50x10^+06^                      1.53x10^+06^   0.98               \*                     1.73x10^+06^              1.16

  ^131^I             3.03x10^+02^                      3.02x10^+02^   1.00               \*                     2.88x10^+02^              9.50x10^-01^

  ^129^I             1.20                              3.00           see note           \*                     2.71                      2.26

  Np-239             1.44E+03                                                                                                             

  ^32^P              1.96x10^+02^                      1.96x10^+02^   1.00                                      1.29x10^+02^              6.60x10^-01^

  ^239,240^Pu        8.00                              7.9            1.01                                      2.95                      3.69x10^-01^

  ^238^Pu            4.00                              4.0            0.98                                      7.08x10^-01^              1.77x10^-01^

  ^103,106^Ru        1.80x10^+03^                      1.80x10^+03^   1.00                                      1.30x10^+03^              7.25x10^-01^

  Sb-124,125         2.40E+01                                                                                                             

  ^89,90^Sr          6.20x10^+02^                      7.11x10^+02^   0.87               \*                     4.60x10^+02^              7.42x10^-01^

  ^35^S              1.75x10^+03^                      1.75x10^+03^   1.00                                      1.53x10^+03^              8.77x10^-01^

  ^99^Tc             5.30x10^+01^                      5.30x10^+01^   1.00                                      5.47x10^+01^              1.03

  Th-232             2.00E-01                                                                                                             

  ^235,238^U         4.20x10^+01^                      4.15x10^+01^   1.01                                      1.19x10^+01^              2.83x10^-01^

  Y-91               1.20E+02                                                                                                             

  ^65^Zn             1.50x10^+02^                      1.50x10^+02^   1.00                                      9.64x10^+01^              6.43x10^-01^

  ^95^Zr, ^95^Nb     1.45x10^+02^                      9.64x10^+02^   0.15               \*                     8.23x10^+02^              5.67

                                                                                                                               Average    
                                                                                                                               Ratio      

  ^3^H Group:                                                                                                                  1.28E+00   
  ^129^I, ^131^I,                                                                                                                         
  ^99^Tc, ^35^S                                                                                                                           

  Strontium Group:                                                                                                             6.21E-01   
  ^103,\ 106^Ru,                                                                                                                          
  ^60^Co, ^89,90^Sr,                                                                                                                      
  ^95^Nb, ^95^Zr,                                                                                                                         
  ^32^P, ^65^Zn,                                                                                                                          
  ^141,\ 144^Ce, U                                                                                                                        

  Cesium Group:                                                                                                                2.23E-01   
  ^134,\ 137^Cs, Pu                                                                                                                       
  ------------------------------------------------------------------------------------------------------------------------------------------------------

#### Comparison of the Phase III Point-of-Release Estimates to Phase II Screening Values

The Table C-24 column headed "Eval." compares the unadjusted Phase III
values to the Phase II screening values. A star notation indicates that
an explanation is warranted.

[^3^H]{.underline}

For ^3^H, the Phase II study states that both stream and seepage basins
were included as the source of releases to the surface water pathway in
the screening assessment (3). It appears from the data presented in the
Phase II report that seepage basin data for ^3^H (and ^131^I) were not
included in the screening assessment. This is indicated by the good
agreement between the stream-only source terms. (The Phase III
point-of-release 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). This appears to be appropriate because
of the eight-day half-life of ^131^I. Any substantial holdup duration
would have caused the seepage basin inventory to decay away. The Phase
III point-of-release data file only includes releases to streams and not
to seepage basins for this isotope.

[^129^I]{.underline}

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 percent of that inventory was released from the
basin to the stream (3 Ci \* 0.4 = 1.2 Ci) (3). Because Phase III
modifies all of the other radionuclide inventories using an adjustment
factor, the 3-Ci assumption was used.

[^89,90^Sr]{.underline}

Although the Phase II screening value and the Phase III base value are
different by about 15 percent, this appears to be due to an addition
error 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 ^89,90^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), which 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 of Phase III Savannah River Releases to Screening Values 

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). Table C-24 presents the average ratios
for the three groups of radionuclides (^3^H, ^90^Sr, and ^137^Cs
groups).

The radionuclides scaled to ^3^H have, on average, increased values
compared with the screening assessment inventories (+28 percent). The
strontium-scaled nuclides have, on average, 62.1 percent of the
screening value. The cesium-scaled nuclides have, on average, about 20
percent 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. Because 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.

## References

1\. National Council on Radiation Protection and Measurements (NCRP).
Screening techniques for determining compliance with environmental
standards, releases of radionuclides to the atmosphere. NCRP Commentary
No. 3. Bethesda, Maryland. 1989.

2\. National Council on Radiation Protection and Measurements (NCRP).
Screening models for releases of radionuclides to air, surface water,
and ground water. NCRP Report No. 123. Bethesda, Maryland. 1996.

3\. Risk Assessment Corporation (RAC). Savannah River Site environmental
dose reconstruction project---phase II: source term calculation and
ingestion pathway dose retrieval evaluation of materials released from
the Savannah River Site*.* RAC Report No. 1-CDC-SRS-1999-Final. April
30, 2001.

4\. Cummins CL, Hetrick CS, and Martin DK. Radioactive releases from the
Savannah River Plant 1954-1989, environmental protection department
summary*.* WSRC-RP-91-684. 1991.

5\. Carlton WH, Evans AG, Geary LA, Murphy CE, Strom RN. Assessment of
strontium in the Savannah River Site environment. WSRC-RP-92-984. May 6,
1994.

6\. U.S. Environmental Protection Agency. Federal Guidance Report 13
cancer risk coefficients for environmental exposure to radionuclides: CD
supplement. EPA 402-C-99-001, Rev. 1. Oak Ridge National Laboratory and
U.S. EPA. April 2002.

7\. Korea Atomic Energy Research Institute. Table of nuclides
\[online\]. 2000-2002. \[cited 2003 Jan 10\]. Available from URL:
[*http://www2.bnl.gov/ton/*](http://www2.bnl.gov/ton/).

8\. Hankins O. Selected readings for NE 301. Fall 1988.

9\. Carlton WH and Denham M. Assessment of selected fission products in
the Savannah River Site environment. WSRC-TR-96-0220. April 1997.

10\. Hefner JD. \[personal communication\] 2003 Jan 21.

11\. Evans AG, Bauer LR, Haselow JS, Hayes DW, Martin HL, McDowell WL,
et al. Uranium in the Savannah River Site environment. WSRC-RP-92-315,
Rev. 0. December 9, 1992.

12\. Carlton WH, Evans AG, Geary LA, Murphy CE, Pinder JE, Strom RN.
Assessment of plutonium in the Savannah River Site environment.
WSRC-RP-92-879, Rev. 1. 1994.

13\. Mark JC. Explosive properties of reactor-grade plutonium. Science&
Global Security, Vol. 4, pp. 111-128. Gordon and Breach Science
Publishers. 1993.

14\. Hefner JD. \[personal communication\] 2003 Feb 12

15\. Carlton WH. Assessment of neptunium, americium, and curium in the
Savannah River Site environment. WSRC-TR-97-00266. December 1997.

16\. Till JE and Meyer HR (eds.). Radiological assessment -- a textbook
on environmental dose analysis. NUREG/CR-3332. ORNL-5958. U.S. Nuclear
Regulatory Commission. Washington, D.C. September 1983.

17\. Ruby CH, Reinhart PJ, Reel CL. Sedimentation and erosion trends of
the Savannah River plant reactor discharge creeks final report.
RPI/R/81-22. Research Planning Institute, Inc. Columbia, South Carolina.
1981.

18\. Cummins CL, Martin DK, Todd JL. Savannah River Site environmental
report (U). WSRC-IM-91-28. Westinghouse Savannah River Company,
Environmental Monitoring Section. Savannah River Site, Aiken, South
Carolina. 1991.

19\. Arnett MW, Karapatakis LK, Mamatey AR, Todd JL. Savannah River Site
environmental report for 1991 (U). WSRC-TR-92-186. Westinghouse Savannah
River Company, Environmental Monitoring Section. Savannah River Site,
Aiken, South Carolina. 1992.

20\. Arnett MW, Karapatakis LK, Mamatey AR. Savannah River Site
environmental report for 1992. WSRC-TR-93-075. Westinghouse Savannah
River Company, Environmental Monitoring Section. Savannah River Site,
Aiken, South Carolina. 1993.

21\. United States Geologic Survey. USGS flow rate at highway 301.

22\. Hayes DW and Marter WL. Historical flow rates for dose
calculations. SRL-ETS-91057. Westinghouse Savannah River Company,
Savannah River Laboratory. June 10, 1991.

23\. Kaplan DI. K~d~ values (mL/g) for SRS soils. \[personal
communication\] 2003 Mar 25.

24\. Kaplan DI, Serkiz SM. In-situ K~d~ values and geochemical behavior
for inorganic and organic constituents of concern at TNX Outfall Delta.
WSRC-TR-99-00488. Westinghouse Savannah River Company. 2000.

25\. Ashley C. Environmental monitoring at the Savannah River Plant,
annual report---1964. DPST-65-302. Savannah River Laboratory. E.I.
Dupont de Nemours & Co. Aiken, South Carolina. June 15, 1965.

26\. 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.

27\. 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.

28\. 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.

29\. Ashley C. Environmental monitoring at the Savannah River Plant,
annual report---1968. DPST-69-302. Savannah River Laboratory. E.I.
Dupont de Nemours & Co. Aiken, South Carolina. June 1969.

30\. Ashley C. Environmental monitoring at the Savannah River Plant,
annual report---1969. DPST-70-302. Savannah River Laboratory. E.I.
Dupont de Nemours & Co. Aiken, South Carolina. May 1970.

31\. Ashley C. Environmental monitoring at the Savannah River Plant,
annual report---1970. DPST-71-302. Savannah River Laboratory. E.I.
Dupont de Nemours & Co. Aiken, South Carolina. 1971.

32\. Ashley C. Environmental monitoring at the Savannah River Plant,
annual report---1971. DPST 72-302. Savannah River Plant. E.I. Dupont de
Nemours & Co. Aiken, South Carolina. September 1972.

33\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1972. DPSPU 73-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. 1973.

34\. Ashley C, Zeigler, CC. Environmental monitoring at the Savannah
River Plant, annual report---1973. DPSPU 74-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. 1974.

35\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1974. DPSPU 75-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. August 1975.

36\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1975. DPSPU 76-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. 1976.

37\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1976. DPSPU 77-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. March 1978.

38\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1977. DPSPU 78-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. December 1978.

39\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1978. DPSPU 79-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. January 1981.

40\. Ashley C, Zeigler CC, Culp PA, Smith DL. Environmental monitoring
at the Savannah River Plant, annual report---1979. DPSPU 80-302.
Savannah River Plant. E.I. Dupont de Nemours & Co. Aiken, South
Carolina. November 1982.

41\. Zeigler CC. Environmental monitoring at the Savannah River Plant,
annual report---1980. DPSPU 81-302. Savannah River Plant. E.I. Dupont de
Nemours & Co. Aiken, South Carolina. 1983.

42\. Ashley C, Zeigler CC. Environmental monitoring at the Savannah
River Plant, annual report---1981. DPSPU 82-302. Savannah River Plant.
E.I. Dupont de Nemours & Co. Aiken, South Carolina. April 1984.

43\. Ashley C, Padezanin PC, Zeigler CC. Environmental monitoring at the
Savannah River Plant, annual report---1982. DPSPU 83-302. Savannah River
Plant. E.I. Dupont de Nemours & Co. Aiken, South Carolina. June 1984.

44\. DOE, 1985.

45\. Zeigler, 1986.

46\. Zeigler, 1987.

47\. Zeigler, 1988.

48\. Davis HA, Martin DK, Todd JL. Savannah River Site environmental
report for 1988 (U). WSRC-RP-89-59-1. Westinghouse Savannah River
Company. Aiken, South Carolina. 1989.

49\. Cummins CL, Martin DK, Todd JL. Savannah River Site environmental
report for 1989 (U). WSRC-IM-90-60. Westinghouse Savannah River Company.
Aiken, South Carolina. 1990.

50\. E.I. du Pont de Nemours & Company. Health physics regional
monitoring, semiannual report, January through June 1960. DPSPU
60-25-26. Savannah River Plant. October 1960.

51\. E.I. du Pont de Nemours & Company. Health physics regional
monitoring, semiannual report, July through December 1960. DPSPU
61-25-4. Savannah River Plant. 1961.

52\. E.I. du Pont de Nemours & Company. Health physics regional
monitoring, semiannual report, January through June 1961. DPSPU 62-25-2.
Savannah River Plant. February 1962.

53\. E.I. du Pont de Nemours & Company. Health physics regional
monitoring, semiannual report, July through December 1961. DPSPU
62-25-9. Savannah River Plant. May 1962.

54\. E.I. du Pont de Nemours & Company. Health physics environmental
monitoring, semiannual report, July through December 1962. DPSP
63-25-10. Savannah River Plant. June 1963.

55\. E.I. du Pont de Nemours & Company. Health physics regional
monitoring, annual report, 1963. DPSPU 64-11-12. Savannah River Plant.
June 1964.

56\. Heffner JD. Comments on CDC's final draft report on phase II of the
Savannah River Site dose reconstruction project (U)*.* ESH-EMS-99-0461.
May 11, 1999.

57\. Reinig WC. Technical bases for Savannah River Plant radioactive
waste release standards. SRS Phase II Database HAG1994090212. July 1,
1999.

[^1]: The report describing the NCRP screening method notes: "The
    assumptions and methods incorporated into all of the screening
    procedures presented in this Report are such that actual doses
    should not be underestimated by more than one order of magnitude. In
    most situations, the actual dose will be significantly less than the
    values calculated for screening" (1).

[^2]: The results in these tables were obtained from an Excel
    spreadsheet (Rad-Screening.xls) that is linked to the electronic
    version of the Phase II report. For both air and water, the results
    of Step One of the screening assessment as presented in this Excel
    spreadsheet are somewhat different from those results presented in
    Tables 3A-2a and 3A-3a of Chapter 3 of the Phase II report (3).

[^3]: The bases for the release estimates could not be determined for
    Phase III. The Phase III source term (0.358 Ci) was significantly
    smaller than that used in the Phase II report (1.20 Ci). Even
    assuming the larger source term, ^129^I did not pass the 0.01
    percent screening criterion used in the Phase II report.

[^4]: Aggregated quantities were reported in the Phase II report (3) and
    various SRS references.

[^5]: This approach is different from that used for release of
    radionuclides to air. Annual radionuclide quantities released from
    four groups of SRS facilities were determined as discussed in
    [Chapter 5](../Chapter_05_Ready%20for%20CDC%20031405.doc). (These
    annual releases are listed in [Appendix
    B](../Appendix_B_ready%20for%20CDC%20031405.doc) as the source term
    for radionuclides released to air.) Then, the transport of these
    radionuclides by wind to exposure locations around the SRS site was
    estimated using a Gaussian plume model as discussed in [Chapter
    6](../Chapter_06_ready%20for%20CDC%20031405.doc). The output of the
    Gaussian plume model was the concentrations of radionuclides
    annually existing in air and deposited onto the ground at these
    exposure locations.

[^6]: Terminology for this discussion is from Phase II.

[^7]: For example, this distance was 12 km for Fourmile Branch.

[^8]: Five exposure pathways were considered in Phase III for release of
    radionuclides to surface water: 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.

[^9]: Exceptions are ^3^H and ^131^I, where only release to streams was
    considered for the screening assessment.

[^10]: SRS environmental reports refer to this monitoring location as
    the River-10 location. This location is at Savannah River mile 120.