EIS-0113_Section_11 - Hanford Site

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APPENDIX P RELEASE MODELS AND RADIONUCLIDE INVENTORIES FOR SUBSURFACE
SOURCES
0-1 Has any waste site monitoring experience (Appendix V) been used
a) to calibrate contaminant movement in the saturatedzone, or General Co mm ents
b) to quantify contaminant transport parameters in-the vadose
zone?
This appendix concerns the rate at which radionuclides are released
from the waste and become available for trans port to the aquifer. The rate
0.2 Given the preliminary judgements that recharge rates at Hanford of release predicted depends upon the form of the waste as well as the
under existing dry conditions are between 0.5 and 5 cm/yr, how can manner in which it is stored. The rate of release predicted also is
the DEIS selection of 0.5 cm/yr--the low of this range--be affected by physical and chemical constants and assumptions made as to the
construed as conservative for the drier climate Scenario? appropriate mechanisms. Once released from their original location, the
radionuclides are transported to the aquifer by recharge water moving
0.3 In view of results of simulations p re sented in Appendix M, how can downward. The three models utilized in Appendix 0 are:
5 cm/yr be construed as a conservative estimate of annual recharge
at Hanford under a wetter climate?
1. adsorption-controlled release,
2.- solubility controlled release, and
0-4 Section 0.4.11 describes the unit hydraulic gradient model used
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3. dissolution-controlled release.
for hand calculating vertical g ro undwater travel times, in the
vadose zone. Use of this model requi re s estimating or determining In addition, diffusion-controlled release is modeled to account for the
three sail parameters:. the saturated moisture content, saturated horizontal movement of radionuclides under a protective harrier. This i
hydraulic conductivity, and "b" value, the latter depending in followed by a discussion of the release model(s) that art applied to each
.turn on the precise relationship between soil moisture content and waste form: Numerous tables summarize the results of the release
capillary water potential. calculations and the data upon which they are based. -
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3.5.2.9
3.5.2.17
a) How were each of the required soil parameters characterized Our analysis of this Appendix suggests that radionuclides may travel
under spatially and temporally varying conditions? faster than shown in this Appendix.
b) Has an adequate range of soil conditions been investigated to Errors or Uncertainties
be able re to confidently ascertain what a"censervative" soil
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moistu characterization is?
The discussion in Section P.1..4 of Appendix P, on diffusion-controlled
release th protective barrier, depends upon the assumption that the
c) Were travel times in the vadose zone computed. by assuming a barrier done, will be 100 percent successful in eliminating infiltration, In the
range of soil moisture contents? If not, which specific soil first . paragraph of Section P.1.4 it is stated that tha analysis is
moisture characteristic data were used to obtain Ks and b predicated on "our professional judament' that the barrier will eliminate
values?
advection as viable or dominant Sache ism far the transport of
- ` radionuclides and chemicals in the soils beneath the barrier. Such a
0-5 What specific range of hydraulic conductivities was considered in conclusion appears unsubstantiated given the doubts about the efficacy of
the vertical averaging of hydraulic conductivity? the protective barrier that were raised in the co mm ents provided previously
on Appendix M.
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0- 6 How were depth zones weighted, and what range of average values
was used in the analysis?
- - One of the principal assumptions madeon page is that the vertical
distance from the bottom of the was" c to the water star
a uniform
0oei 4c
i using more-conservative retardation factors-and diffusion
1 5 meters. ofO the w the reported hart50 vertical istance for is tankst
coefficcients affect travel times, first arrival, and peak le percent of the waste) is less than se meters, m and It is
concentrations for the various release scenarios? less under other plausile scenarios see more detailed discussion fn our
review of i eendfx p, this chapter). We understand
the hat the
transport path
0-B What was