ML20012D635
| ML20012D635 | |
| Person / Time | |
|---|---|
| Issue date: | 03/06/1990 |
| From: | Mark Thaggard NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Thomas Nicholson NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| REF-WM-3 NUDOCS 9003280160 | |
| Download: ML20012D635 (5) | |
Text
l e-MAR 0 61990 v
MEMORANDUM FOR:
Thomas J. Nicholson, S$nior Hydrogeologist Waste Management Branch Division of Engineerir.g, RES FROM:
Mark Thaggard, Hydrologist 1
Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS
SUBJECT:
PNL's DRAFT REPORT ON THE DEVELOPMENT OF AN INFILTRATION EVALUATION METHODOLOGY I have completed my review of PNL's draf t report dated January 1990.. Enclosed are my comments on the report.
In reviewing the report, my primary ain was to look at the report and the methodology in terms of their application; it was not my general intentions to verify the validity of the technical 1
information contained in the report.
hithough I was not reviewing the report for grammatical accuracy, I could not help but notice that there are a large number of grammatical and typographical-e errors in this draft of the report.
Please let me know if you have-any questions-or if you would like to address my comments in greater details.
Mark Thaggard, Hydrologist Technical B::anch St@'g Di Divisjon of Low-Level Waste Management 5
g6 and Decommissioning, NMSS
Enclosure:
Review Comments
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e REVIEW COMMENT 8 ON.PNL's DRAFT IEN REPORT DATED JANUARY 1990 OVERALL COMMENTS ON THE REPORT AND METHODOLOGY Hy primary concern is with the application of the IEM.
- It. appears that PNL's primary intent was to develop the methodology; they either assumed that it would bra easy _
to apply'or they gave very.little thought to its application.
In terms of utilizing the IEM, I am concerned with 1) understanding and utilizing some of the analytical equations and 2) understanding the coupling of-the components of the IEM.
1.
Analytical Ecuations k
The equations developed in the section on methods
. of assessing. hydraulic properties and the section on the' stochastic suodeling approach will be difficult'to' apply without referring to some of the references cited.. This may hinder the use of methodology if some of the references are not readily available.
1 As an example, in the section on methods of assessing' hydraulic properties, PNL cites a number of ways'of determining the unsaturated hydraulic conductivity as a function of water content, and ways of. developing the soil-water retention curve;
.however, most of their equations contain undefined parameters,'which will require the user to review the original reference in order to determine reasonable. parameters to use. PNL should develop the equations in this section further and define all parameters in the equations.
I had considerable difficulty in understanding how the' equations of the stochastic modeling approach
- had been applied. With the use of the cited references it might have been easier to understand how the probability density functions had been developed and how the range of expected saturation and. flux had been derived. However, I did not have these references available. With just the information provided in the IEM document, I
believe that it would be very difficult for.someone to apply.the IEM stochastic modeling approach for another site, using a different data set. PNL should include some example calculations used to develop some of their plots.
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Couclina of Components
-_Information in the report on hou the various components.of the IEM are coupled is very sketchy.
It is difficult to understand how the one-and two-dimensional models are interfaced during a numerical simulation.
In the report, it-appears that the authors applied both the one-and two-dimensional models to model the same area.
SPECIFIC COMMENTS In addition to overall comments stated above, I have a few specific comments on certain parts of the report.
- These comments are listed under the heading found in the report for clarity.
2.1 Climate Data Generation Studies 1.
It is difficult to understand what type of climatic dets is needed;
.i.e.,
whether the authors are indicating that only precipitation data or both precipitation and solar radiation data are needed.
In this section of the report, the authors indicate a climate simulation model which generates precipitation, solar radiation, and temperature is needed; however, in later sections of the report when the authors refer to climatic. data, they refer only to precipitation.
Solar radiation and temperature data are normally used to calculate potential evapotranspiration; however, evapotranspiration is treated separately in another section of the report.
2.
It is difficult to ascertain how much existing climatic data are needed to get reasonable predictions from the WGEN model.
In the authors' simulations,-it appears that one year of rainfall data were used to generate ten years of predicted data; however, from the authors' January 22, 1990 presentation, it was my understanding that considerably more data than this were required.
If a long period of data is needed in i
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4 order to get reasonable predictions, I question the availability of such data given the usual remote locations-involved.
2.3.2 Model Selection 1.
One of the references cited by the authors (van Genuchten, 1980),
states that the Brooks and Corey.
equations are effected'by bubbling pressures; however, the authors make no mention of considering bubbling pressures in selecting the models to be used.
If the authors considers this to be unimportant, it should be stated.
L 2.
The authors discussion on the selection of the appropriate soil-water retention equation needs further clarification.
The authors describe the differences between the curves produced by each equation (note:-example plots of the curves would be helpful); however, it is difficult to. understand why.or.when l
one equation should be used as opposed to the'other.
This is an important issue since the authors indicate that prediction of the unsaturated conductivity is more sensitive to.the. choice.of equation used to describe the soil-water retention curve than the choice of the-conductivity model.
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.5.1 closed Form Analytic Annroach 1.
The authors develops a lot of equations in this section.
A glossary of the variables would be very helpful.
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2.
The labelling for. figures 5.4 through 5.18 needs improvement.
The authors are attempting to compare three variables, which require some
-figures to be continued over three plots; however, it is not. clear how the third variable is changed from one plot to the next, s
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5.6' Evaluation of Infiltration into a Waste Discosal-Unit Usina Numerical Codes Li 1.
One result from the' authors' simulations show that the barrier can become completely' saturated within a fairly short timeframe under some' circumstances; however, it is difficult to conclude whether this resulted~because of the high saturated conductivity, the omission
~ 1 of evapotranspiration, or the rainfall distribution used.
Although the authors indicate the importanceLof including
=evapotranspiration as part of the IEM, they omitted it-in their numerical simulations.
In my opinion, such.an~important parameter
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needs to be-included.
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