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Contents

1 INTRODUCTION ...................................................................................................... 4

2 METHODOLOGY ..................................................................................................... 5

2.1 Code Version .................................................................................................................... 6

2.2 Random Seed in the CCDFGF Control Files ................................................................... 6

2.3 Run Control ...................................................................................................................... 6

3 ANALYSIS AND RESULTS ..................................................................................... 7

3.1 Cuttings and Cavings Normalized Releases..................................................................... 7

3.2 Spallings Normalized Releases ...................................................................................... 12

3.3 Normalized Direct Brine Releases ................................................................................. 17

3.4 Normalized Transport Releases to the Culebra .............................................................. 22

3.5 Total Normalized Releases ............................................................................................. 24

4 SUMMARY ............................................................................................................. 28

5 REFERENCES ....................................................................................................... 29

 

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List of Figures 

Figure 3-1: PC3R PA Replicate 1 Cuttings and Cavings Normalized Releases ............................................................ 8 

Figure 3-2: PCS-2012 PA Replicate 2 Cuttings and Cavings Normalized Releases ..................................................... 8 

Figure 3-3: PCS-2012 PA Replicate 3 Cuttings and Cavings Normalized Releases ..................................................... 9 

Figure 3-4: PCS-2012 PA Mean and Quantile CCDFs for Cuttings and Cavings Normalized Releases, Replicates 1-3

 ....................................................................................................................................................................................... 9 

Figure 3-5: PCS-2012 PA Confidence Limits on Overall Mean for Cuttings and Cavings Normalized Releases ...... 10 

Figure 3-6: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Cuttings and Cavings Releases . 10 

Figure 3-7: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Cuttings and Cavings Volumes . 11 

Figure 3-8: PCS-2012 PA Replicate 1 Spallings Normalized Releases ...................................................................... 13 

Figure 3-9: PCS-2012 PA Replicate 2 Spallings Normalized Releases ...................................................................... 13 

Figure 3-10: PCS-2012 PA Replicate 3 Spallings Normalized Releases ..................................................................... 14 

Figure 3-11: PCS-2012 PA Mean and Quantile CCDFs for Spallings Normalized Releases, Replicates 1-3 ............. 14 

Figure 3-12: PCS-2012 PA Confidence Limits on Overall Mean for Spallings Normalized Releases ....................... 15 

Figure 3-13: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Spallings Releases ................... 15 

Figure 3-14: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Spallings Volumes ...................................... 16 

Figure 3-15: PCS-2012 PA Replicate 1 Normalized Direct Brine Releases ................................................................ 18 

Figure 3-16: PCS-2012 PA Replicate 2 Normalized Direct Brine Releases ................................................................ 18 

Figure 3-17: PCS-2012 PA Replicate 3 Normalized Direct Brine Releases ................................................................ 19 

Figure 3-18: PCS-2012 PA Mean and Quantile CCDFs for Normalized Direct Brine Releases, Replicates 1-3 ........ 19 

Figure 3-19: PCS-2012 PA Confidence Limits on Overall Mean for Normalized Direct Brine Releases .................. 20 

Figure 3-20: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Direct Brine Releases .............. 20 

Figure 3-21: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Direct Brine Volumes ................................. 21 

Figure 3-22: PCS-2012 PA and PABC-2009 Replicate Means for Normalized Transport Releases to the Culebra ... 23 

Figure 3-23: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Transport Releases to the Culebra .............. 23 

Figure 3-24: PCS-2012 PA Replicate 1 Total Normalized Releases ........................................................................... 25 

Figure 3-25: PCS-2012 PA Replicate 2 Total Normalized Releases ........................................................................... 25 

Figure 3-26: PCS-2012 PA Replicate 3 Total Normalized Releases ........................................................................... 26 

Figure 3-27: PCS-2012 PA Mean and Quantile CCDFs for Total Normalized Releases, Replicates 1-3 ................... 26 

Figure 3-28: PCS-2012 PA Confidence Limits on Overall Mean for Total Normalized Releases .............................. 27 

Figure 3-29: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Total Normalized Releases ......................... 27 

Figure 3-30: PCS-2012 PA Primary Components Contributing to Total Releases ..................................................... 28

List of Tables 

Table 1: PCS-2012 PA and PABC-2009 Statistics on the Overall Mean for Total Normalized Releases in EPA Units 

at Probabilities of 0.1 and 0.001 .................................................................................................................................. 24 

 

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1 INTRODUCTION 

The Waste Isolation Pilot Plant (WIPP), located in southeastern New Mexico, has been 

developed by the U.S. Department of Energy (DOE) for the geologic (deep underground) 

disposal of transuranic (TRU) waste. Containment of TRU waste at the WIPP is regulated by the 

U.S. Environmental Protection Agency (EPA) according to the regulations set forth in Title 40 of 

the Code of Federal Regulations (CFR), Part 191. The DOE demonstrates compliance with the 

containment requirements according to the Certification Criteria in Title 40 CFR Part 194 by 

means of performance assessment (PA) calculations performed by Sandia National Laboratories 

(SNL). WIPP PA calculations estimate the probability and consequence of potential 

radionuclide releases from the repository to the accessible environment for a regulatory period of 

10,000 years after facility closure. The models used in PA are maintained and updated with new 

information as part of an ongoing process. Improved information regarding important WIPP 

features, events, and processes typically results in refinements and modifications to PA models 

and the parameters used in them. Planned changes to the repository and/or the components 

therein also result in updates to WIPP PA models. WIPP PA models are used to support the 

repository recertification process that occurs at five-year intervals following the receipt of the 

first waste shipment at the site in 1999. 

Waste panel closures comprise a repository feature that has been represented in WIPP PA since 

the original Compliance Certification Application (CCA) of 1996. Panel closures are included in 

WIPP PA models principally because they are a part of the disposal system, not because they 

play a substantive role in inhibiting the release of radionuclides to the outside environment. The 

DOE stated in the CCA (DOE 1996) that “The panel closure system was not designed or 

intended to support long-term repository performance.” The 1998 rulemaking that certified 

WIPP to receive transuranic waste placed conditions on the panel closure design to be 

implemented in the repository. The mandated design consists of a concrete block wall, an open 

drift section, and a concrete monolith, and was termed the “Option D” panel closure. Following 

the selection of the Option D design in 1998, the engineering of the panel closure has been reassessed, and a revised design has been established that is simpler, cheaper, and easier to 

construct. The revised panel closure design, termed the Run-of-Mine Panel Closure System 

(ROMPCS), is comprised of 100 feet of ROM salt with barriers at each end. The ROM salt is 

generated from ongoing mining operations at the WIPP and may be compacted and/or moistened 

as it is emplaced in a panel entry. The barriers consist of ventilation bulkheads, similar to those 

currently used in the panels as room closures. 

The DOE has submitted a planned change request (PCR) to the EPA requesting that EPA modify 

Condition 1 of the Final Certification Rulemaking for 40 CFR Part 194 (EPA, 1998) for the 

WIPP. The PCR submitted to EPA requests that Condition 1 be changed, and that the ROMPCS 

design be approved for use in all panels (DOE, 2011). In support of this rulemaking change, a 

performance assessment has been completed that incorporates the ROMPCS design into the 

current PA baseline established by the 2009 Performance Assessment Baseline Calculation 

(PABC-2009) (Clayton et al., 2010). The name given to this new panel closure PA is PCS-2012, 

and the plan for its execution is detailed in AP-161 (Camphouse 2012a). PCS-2012 PA results 

are compared to those obtained in the PABC-2009 as a means to quantify potential impacts due 

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to the panel closure redesign. This analysis package consists of the CCDFGF component of the 

PCS-2012 PA. 

2 METHODOLOGY 

The performance assessment methodology accommodates both aleatory (i.e. stochastic) and 

epistemic (i.e. subjective) uncertainty in its constituent models. Aleatory uncertainty pertains to 

unknowable future events such as intrusion times and locations that may affect repository 

performance. It is accounted for by the generation of random sequences of future events. 

Epistemic uncertainty concerns parameter values that are assumed to be constants and the 

constants’ true values are uncertain due to a lack of knowledge about the system. An example of 

a parameter with epistemic uncertainty is the permeability of a material. Epistemic uncertainty is 

accounted for by sampling of parameter values from assigned distributions. One set of sampled 

values required to run a WIPP PA calculation is termed a vector. The performance assessment 

models are executed for three replicates of 100 vectors, each vector being a realization resulting 

from a particular set of parameter values. A sample size of 10,000 possible sequences of future 

events is used in the calculations to estimate an exceedance probability of 0.001 (Helton et al. 

1998). The releases for each of 10,000 possible sequences of future events are tabulated for each 

of the 300 vectors, totaling 3,000,000 possible sequences. 

For a random variable, the complementary cumulative distribution function (CCDF) provides the 

probability of the variable being greater than a particular value. By regulation, performance 

assessment results are presented as a distribution of CCDFs of releases (U.S. EPA 1996). Each 

individual CCDF summarizes the likelihood of releases across all futures for one vector of 

parameter values. The uncertainty in parameter values results in a distribution of CCDFs. 

Releases are quantified in terms of “EPA units”. Releases in EPA units result from a 

normalization by radionuclide and the total inventory. For each radionuclide, the ratio of its 

10,000 year cumulative release (in curies) to its release limit is calculated. The sum of these 

ratios is calculated across the set of radionuclides and normalized by the transuranic inventory 

(in curies) of α-emitters with half-lives greater than 20 years. Mathematically, the formula used 

to calculate releases in terms of EPA units is of the form 

ܴ ൌ	

ݏ݅݁ݎݑܿ	଺10 ൈ 1

௜ܳ෍ ܥ

௜ ௜ܮ

where R is the normalized release in EPA units. Quantity Qi is the 10,000 year cumulative 

release (in curies) of radionuclide i. Quantity Li is the release limit for radionuclide i, and C is 

the total transuranic inventory (in curies) of α-emitters with half-lives greater than 20 years. 

Mean and quantile CCDFs are calculated to compare the distributions of CCDFs among 

replicates and to demonstrate sufficiency of sample size. At each value of normalized release R

on the horizontal axis, the CCDFs for a single replicate define 100 values of probability. 

Forming the arithmetic mean of these 100 probabilities yields the mean probability that the 

release exceeds R. The curve defined by the mean probabilities for each value of R is the mean 

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CCDF. The 10th and 90th quantile CCDFs for a particular replicate are determined from the 

sorted order of the 100 CCDFs found for that replicate. 

The overall mean CCDF is computed as the arithmetic mean of the three mean CCDFs from each 

replicate. Confidence limits are computed about the overall mean CCDF using the Student’s tdistribution, the mean CCDFs from each replicate, and the standard error based on the three 

replicate means. Confidence limits as they are implemented in PA are defined vertically about 

the mean, rather than horizontally. An artifact of this convention is that lower confidence limits 

can sometimes assume negative values, which cannot be plotted on a logarithmic scale. When 

this occurs, the resulting lower confidence curve appears incomplete. 

CCDF curves and statistics are generated using the CCDFGF_Analysis database utility. A 

description of this utility can be found in Kirchner (2010). A DVD containing the data loaded 

into this utility resulting from PCS-2012 PA and PABC-2009 CCDFGF calculations, and 

subsequent SigmaPlot plots, are included as an attachment to this document. 

2.1 Code Version 

PRECCDFGF version 1.01 and CCDFGF version 5.02 were used for the PABC-2009 and the 

PCS-2012. 

2.2 Random Seed in the CCDFGF Control Files 

One of the features that the CCDFGF control file initializes is the random number generator in 

the code. Setting the random number seed in the control file determines the sequence of pseudorandom numbers used by CCDFGF. This sequence of numbers affects several stochastic 

parameters, such as the drilling location, depth, and type of plugging pattern, utilized when 

CCDFGF simulates the drilling of boreholes at the surface of the WIPP repository. 

For the PCS-2012 PA, the same random seeds for CCDFGF were used as in the PABC-2009. 

This was done to allow a vector by vector comparison of the results of the PCS-2012 PA to those 

obtained in the PABC-2009. As the random seeds used to initialize the sampling of the 

epistemic parameters were unchanged in the PCS-2012 PA and the PABC-2009, any differences 

between the analyses can be attributed solely to the changes in parameters and geometry used in 

those calculations. Random seeds used in the PCS-2012 PA calculations are specified in the files 

CCGF_AP161_CONTROL_Rr.inp, where r = 1, 2, 3. These files are located in CMS library 

LIBAP161_CCGF.

2.3 Run Control 

Run control, including code versions used and descriptions of code sequencing used to obtain 

CCDFGF results in the PCS-2012 PA, is documented in Camphouse et al. (2012c). PCS-2012 

PA results generated by code CCDFGF have file names CCGF_AP161_Rr.OUT, where r (the 

replicate number) equals 1, 2, or 3. These files are located in CMS library LIBAP161_CCGF 

under class AP161-0. PABC-2009 results generated by CCDFGF have file names 

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CCGF_PABC09_Rr.OUT, and are located in CMS library LIBPABC09_CCGF under class 

PABC09-0.

3 ANALYSIS AND RESULTS 

Results obtained from PCS-2012 PA calculations are broken out in subsections for each 

component of release. At the conclusion of the subsection for each release component, results 

obtained for the PCS-2012 PA are compared to those found in the PABC-2009. Normalized 

releases for cuttings and cavings are discussed in Subsection 3.1. Spallings releases are 

presented in Subsection 3.2. Results found for direct brine releases are discussed in Subsection 

3.3. New calculations for normalized transport releases through the Culebra were not performed 

as part of the PCS-2012 PA. BRAGFLO scenario S6-BF is used by PA code PANEL to 

determine the radionuclide source term to the Culebra. BRAGFLO scenario S6-BF results 

obtained in the PCS-2012 PA are virtually identical to those calculated in the PABC-2009 

(Camphouse 2012b). Consequently, the radionuclide source term to the Culebra is unaffected by 

the change of the panel closure design from Option D to the ROMPCS. There have been no 

updates to the Culebra flow model, e.g. updated transmissivity fields, since the completion of the 

PABC-2009. As a result, it is reasonable and appropriate to incorporate Culebra transport results 

calculated in the PABC-2009 into the PCS-2012 PA. 

Total normalized releases are shown in Subsection 3.5. 

3.1 Cuttings and Cavings Normalized Releases 

The change in panel closure design from Option D to the ROMPCS has no impact on cuttings 

and cavings releases. PA code CUTTINGS_S calculates cuttings and cavings release volumes, 

as well as spallings volumes. Spallings release volumes are potentially impacted by the panel 

closure redesign, and so are calculated as part of the PCS-2012 PA. As a result, cuttings and 

cavings releases are also calculated, even though they are identical to those obtained in the 

PABC-2009. 

PCS-2012 PA cuttings and cavings releases are presented in this section and subsequently 

compared to results obtained in the PABC-2009. Figure 3-1, Figure 3-2, and Figure 3-3 contain 

PCS-2012 PA cuttings and cavings release CCDFs for replicates 1, 2, and 3, respectively. Mean 

and quantile CCDF distributions for the three replicates are shown together in Figure 3-4. As 

seen in that figure, the mean and quantile CCDFs obtained for the three replicates are nearly 

coincident. Figure 3-5 contains the 95 percent confidence limits about the overall cuttings and 

cavings mean. As is clear in that figure, the confidence limit is very tightly contained about the 

mean at all probabilities. 

For the sake of reference, overall means of cuttings and cavings releases calculated in the PCS2012 PA and the PABC-2009 are plotted simultaneously in Figure 3-6 and Figure 3-7. As seen 

in those figures, cuttings and cavings releases and volumes obtained for both analyses were 

identical as no changes were made to the underlying models or parameters used in their 

calculation for the PCS-2012 PA (Kicker 2012). 

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Figure 3-1: PCS-2012 PA Replicate 1 Cuttings and Cavings Normalized Releases

Figure 3-2: PCS-2012 PA Replicate 2 Cuttings and Cavings Normalized Releases

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Figure 3-3: PCS-2012 PA Replicate 3 Cuttings and Cavings Normalized Releases

Figure 3-4: PCS-2012 PA Mean and Quantile CCDFs for Cuttings and Cavings Normalized Releases, Replicates 1-3 

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Figure 3-5: PCS-2012 PA Confidence Limits on Overall Mean for Cuttings and Cavings Normalized Releases

Figure 3-6: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Cuttings and Cavings Releases 

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Figure 3-7: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Cuttings and Cavings Volumes 

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3.2 Spallings Normalized Releases 

PCS-2012 PA spallings releases are presented in this section and subsequently compared to 

results obtained in the PABC-2009. Figure 3-8, Figure 3-9, and Figure 3-10 contain PCS-2012 

PA CCDFs for spallings releases. Mean and quantile CCDF distributions for the three replicates 

are shown together in Figure 3-11. As seen in that figure, the 10th percentiles for each replicate 

have releases sufficiently small as to not appear at all on the chosen axes. Moreover, the mean 

CCDF for each replicate becomes larger than the 90th percentile as releases increase. The large 

number of vectors with very small spallings releases causes the distribution to be heavily rightskewed. This results in a mean that exceeds the 90th percentile as releases increase. Figure 3-12 

contains the 95 percent confidence limits about the spallings mean. In total, 38 % of the 

replicate 1 vector, 47 % of the replicate 2 vectors and 41 % of the replicate 3 vectors in the PCS2012 PA showed non-zero spallings releases 

To facilitate comparisons of spallings releases calculated in the PCS-2012 PA to those obtained 

in the PABC-2009, overall mean and volume CCDFs obtained in these two analyses are plotted 

simultaneously in Figure 3-13 and Figure 3-14. As seen in those figures, the PCS-2012 PA 

CCDF curves shown in Figure 3-13 and Figure 3-14 show increases in spallings releases and 

volumes when compared to PABC-2009 results. Spallings volumes, and their associated 

releases, are a function of repository pressure. A pressure increase in an intruded waste panel 

typically corresponds to an increase in spallings volumes. As nothing was changed regarding the 

waste inventory used in the PABC-2009 and the PCS-2012 PA, an increase in spallings volume 

results in an associated increase in spallings releases. The ROMPCS design implemented in the 

PCS-2012 PA has slightly lower long-term permeabilities (on average) than the Option D 

closures implemented in the PABC-2009. For intrusion scenarios that involve an encounter with 

a pressurized brine region below the repository, the reduction in closure permeability resulted in 

an increase in pressurization of the waste panel for a period of time following the intrusion. This 

increase in pressure translates directly to increases in PCS-2012 PA spallings volumes and 

releases as compared to the PABC-2009 results. For intrusion scenarios that do not involve an 

encounter with a region of pressurized brine below the repository, the mean average pressure in 

the intruded waste panel was higher in the PCS-2012 PA as compared to the PABC-2009. This 

increase in pressure also yields increases in spallings volumes and their associated releases. 

Increased pressure in repository waste areas is responsible for the increases seen in PCS-2012 

PA spallings volumes and releases as compared to the PABC-2009 results (Kicker 2012). 

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Figure 3-8: PCS-2012 PA Replicate 1 Spallings Normalized Releases 

Figure 3-9: PCS-2012 PA Replicate 2 Spallings Normalized Releases 

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Figure 3-10: PCS-2012 PA Replicate 3 Spallings Normalized Releases 

Figure 3-11: PCS-2012 PA Mean and Quantile CCDFs for Spallings Normalized Releases, Replicates 1-3 

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Figure 3-12: PCS-2012 PA Confidence Limits on Overall Mean for Spallings Normalized Releases

Figure 3-13: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Spallings Releases 

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Figure 3-14: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Spallings Volumes 

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3.3 Normalized Direct Brine Releases 

PCS-2012 PA normalized direct brine releases are presented in this section and subsequently 

compared to results obtained in the PABC-2009. Figure 3-15, Figure 3-16, and Figure 3-17 

contain PCS-2012 PA CCDFs for DBRs. Mean and quantile CCDF distributions for the three 

replicates are shown together in Figure 3-18. Figure 3-19 contains the 95 percent confidence 

limits about the DBR overall mean. As seen in Figure 3-19, the overall mean and its lower/upper 

95% confidence limits are well below acceptable release limits. 

To facilitate comparisons of DBRs calculated in the PCS-2012 PA to those obtained in the 

PABC-2009, overall mean and volume CCDFs obtained in these two analyses are plotted 

together in Figure 3-20 and Figure 3-21. As seen in Figure 3-20, the CCDF curve obtained for 

direct brine releases shows greater mean probabilities in the PCS-2012 PA for the majority of 

release values. 

In the PCS-2012 PA, intrusion scenarios that involve drilling into a pressurized brine region 

underneath the repository exhibited an increase in the average pressure in the intruded waste 

panel when compared to the PABC-2009 results for a period of time following the intrusion 

(Malama 2012). Additionally, an increase in mean waste panel brine saturation was found for 

this type of intrusion (Malama 2012). The combination of an increase in waste panel pressure 

and brine saturation leads to an increase in DBR volumes, as well as a greater number of nonzero brine volume vectors for PCS-2012 PA compared to PABC-2009 (Camphouse 2012b). For 

intrusion scenarios that do not involve drilling into a pressurized brine region underneath the 

repository, there is an increase in mean waste panel pressure accompanied by a small decrease in 

brine saturation for the PCS-2012 PA compared to the PABC-2009 (Malama 2012). This results 

in an increase in maximum DBR volume for the PCS-2012 PA. This increase in pressure of the 

intruded panel as compared to the PABC-2009 impacted the number of DBR realizations used to 

calculate the DBR release tables (Malama 2012). The total number of nonzero DBR volumes 

increased from 2,999 in the PABC-2009 to 3,182 in the PCS-2012 PA, an increase of 183 

realizations with a nonzero DBR volume (Malama 2012). For undisturbed conditions, the longterm mean waste panel pressure and brine pressure also increased from the PABC-2009 to the 

PCS-2012 PA. The is due to the implementation of the ROMPCS design, which allows greater 

brine flow into the waste panel than the Option D design, resulting in greater gas generation and 

thus mean waste panel pressure (Camphouse 2012b). 

However, despite the greater number of nonzero DBR volumes found in the DBR analysis 

(Malama 2012), the number of nonzero DBR release vectors found in the CCDFGF analysis 

remains the same from the PABC-2009 to the PCS-2012 PA. The increase in mean DBR releases 

is due to increased releases in only a few vectors, and is not attributed to an overall increase in 

releases for a majority of vectors (Kirchner 2012). Additional evidence of the influence of a few 

vectors on the DBR volumes is found in Figures 5-1 to 5-10 of the PCS-2012 PA DBR report 

(Malama 2012), which show that the DBR volume distribution skews toward higher volumes 

only for the high end of the distribution. The final result is an increase in mean probabilities for 

the PCS-2012 PA compared to the PABC-2009 for the majority of DBR release values. 

The overall mean CCDF curves for direct brine volumes obtained in the PCS-2012 PA and the 

PABC-2009 are shown together in Figure 3-21. For probabilities less than about 0.1, the mean 

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DBR volume increased, most likely due to the increase in waste panel pressure observed in the 

Salado flow modeling results as compared to the PABC-2009. The increase in the number of 

realizations with a nonzero DBR volume combined with the increase in the maximum DBR 

volumes found in the Salado flow modeling results (Camphouse 2012b) explain the differences 

observed in the CCDF DBR volume curves obtained in the PABC-2009 and the PCS-2012 PA. 

Figure 3-15: PCS-2012 PA Replicate 1 Normalized Direct Brine Releases 

Figure 3-16: PCS-2012 PA Replicate 2 Normalized Direct Brine Releases 

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Figure 3-17: PCS-2012 PA Replicate 3 Normalized Direct Brine Releases 

Figure 3-18: PCS-2012 PA Mean and Quantile CCDFs for Normalized Direct Brine Releases, Replicates 1-3 

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Figure 3-19: PCS-2012 PA Confidence Limits on Overall Mean for Normalized Direct Brine Releases

Figure 3-20: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Normalized Direct Brine Releases 

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Figure 3-21: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Direct Brine Volumes 

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3.4 Normalized Transport Releases to the Culebra 

PCS-2012 PA normalized transport releases to the Culebra are discussed in this section and 

compared to those seen in the PABC-2009. These results are included primarily as a means to 

validate the expectation that the proposed changes to the PCS investigated in the PCS-2012 PA 

have minimal impact on Culebra transport releases. 

Replicate means obtained in the PCS-2012 PA and the PABC-2009 for normalized transport 

releases to the Culebra are shown together in Figure 3-22. As seen in that figure, the means 

obtained in the two analyses for each replicate are identical. Overall means of transport releases 

to the Culebra obtained in the PCS-2012 PA and the PABC-2009 are shown together in Figure 

3-23. As is evident from that figure, there is no difference in the overall mean of transport 

releases to the Culebra obtained in the two analyses. The individual replicate means and the 

overall mean of transport releases to the Culebra are primarily unaffected by the panel closure 

design changes implemented in the PCS-2012 PA. As a result, it is reasonable to conclude that 

normalized transport releases from the Culebra be primarily unchanged as well, since nothing 

was changed in the Culebra transport model from the PABC-2009 to the PCS-2012 PA.

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Figure 3-22: PCS-2012 PA and PABC-2009 Replicate Means for Normalized Transport Releases to the Culebra

Figure 3-23: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Transport Releases to the Culebra 

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3.5 Total Normalized Releases 

Total normalized releases for PCS-2012 PA are presented in this section and subsequently 

compared to results obtained in the PABC-2009. Total releases are calculated by forming the 

summation of releases across each potential release pathway, namely cuttings and cavings 

releases, spallings releases, direct brine releases, and transport releases. PCS-2012 PA CCDFs 

for total releases are presented in Figure 3-24, Figure 3-25, and Figure 3-26 for replicates 1, 2, 

and 3, respectively. Mean and quantile CCDF distributions for the three replicates are shown 

together in Figure 3-27. Figure 3-28 contains the 95 percent confidence limits about the overall 

mean of total releases. As seen in Figure 3-28, the overall mean for normalized total releases 

and its lower/upper 95% confidence limits are well below acceptable release limits. As a result, 

the panel closure design and repository configuration changes investigated in the PCS-2012 PA 

do no result in WIPP non-compliance with the containment requirements of 40 CFR Part 191. 

PCS-2012 PA and PABC-2009 overall mean CCDFs for total releases are shown together in 

Figure 3-29. As seen in that figure, the overall mean CCDFs obtained in the two analyses are 

nearly identical for release values less than approximately 0.1 EPA units. For releases greater 

than 0.1 EPA units, the CCDF curve obtained in the PCS-2012 PA is higher than that found in 

the PABC-2009. This increase corresponds primarily to the differences found for direct brine 

releases between the two analyses as discussed in Section 3.3 and illustrated in Figure 3-20. The 

differences found for spallings may slightly affect the total CCDF curve as well (Section 3.2, 

Figure 3-13). PCS-2012 PA cuttings and cavings results are unchanged from those found in the 

PABC-2009. The panel closure design change investigated in the PCS-2012 PA has an impact 

on the overall mean of total releases from the PABC-2009 to the PCS-2012 PA due to the 

changes in direct brine releases calculated in those analyses (Figure 3-30).

A comparison of the statistics on the overall mean for total normalized releases obtained in the 

PCS-2012 PA and the PABC-2009 can be seen in Table 1. At a probability of 0.1, values 

obtained for mean total releases has increased from 0.09 to 0.10 for the PCS-2012 PA. At a 

probability of 0.001, the increase in DBRs seen at that probability in the PCS-2012 PA results in 

an increase in the mean total release by approximately 0.41 EPA units. An increase is seen in the 

95% confidence limit when compared to the PABC-2009 results, while the 90th percentile 

remains the same. An increase in the mean total release accompanied by no change to the 90th

percentile value is additional evidence that only a few vectors have significantly increased 

releases. 

Probability Analysis Mean Total 

Release 

90th

Percentile 

Lower 

95% CL 

Upper 

95% CL 

Release 

Limit 

0.1 PCS-2012 PA 0.10 0.17 0.10 0.10 1 

PABC-2009 0.09 0.16 0.09 0.10 1 

0.001 PCS-2012 PA 1.51 1.00 0.33 2.81 10 

PABC-2009 1.10 1.00 0.37 1.77 10 

Table 1: PCS-2012 PA and PABC-2009 Statistics on the Overall Mean for Total Normalized Releases in EPA Units at 

Probabilities of 0.1 and 0.001 

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Figure 3-24: PCS-2012 PA Replicate 1 Total Normalized Releases 

Figure 3-25: PCS-2012 PA Replicate 2 Total Normalized Releases 

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Figure 3-26: PCS-2012 PA Replicate 3 Total Normalized Releases 

Figure 3-27: PCS-2012 PA Mean and Quantile CCDFs for Total Normalized Releases, Replicates 1-3 

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Figure 3-28: PCS-2012 PA Confidence Limits on Overall Mean for Total Normalized Releases 

Figure 3-29: PCS-2012 PA and PABC-2009 Overall Mean CCDFs for Total Normalized Releases 

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Figure 3-30: PCS-2012 PA Primary Components Contributing to Total Releases 

4 SUMMARY 

Total normalized releases calculated in the PCS-2012 PA remain below their regulatory limits. 

As a result, the panel closure design and repository configuration changes investigated in the 

PCS-2012 PA do not result in WIPP non-compliance with the containment requirements of 40 

CFR Part 191. Cuttings and cavings releases and direct brine releases are the two primary 

release components contributing to total releases in the PCS-2012 PA. Cuttings and cavings 

releases are identical to those calculated in the PABC-2009. Changes in total releases are 

primarily attributed to changes calculated in direct brine releases from the PABC-2009 to the 

PCS-2012 PA. Increases are observed in PCS-2012 PA spallings releases as compared to the 

PABC-2009, but these differences are comparatively minor and do not have a significant impact 

on the overall total normalized releases found in the PCS-2012 PA. 

 

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5 REFERENCES 

Camphouse, R.C. 2012a. Analysis Plan for the 2012 WIPP Panel Closure System Performance 

Assessment A-161, Revision 0. Sandia National Laboratories, Carlsbad, NM. ERMS 557726. 

Camphouse, R.C. 2012b. Analysis Package for Salado Flow Modeling Done in the AP-161 

(PCS-2012) Performance Assessment. Carlsbad, NM, Sandia National Laboratories. ERMS 

558204 

Camphouse, R.C, D.C. Kicker, T.B. Kirchner, J.J. Long, B. Malama, and T.R. Zeitler. 2012c. 

Summary Report and Run Control for the WIPP Panel Closure System Performance Assessment. 

Carlsbad, NM: Sandia National Laboratories. ERMS 558226. 

Clayton, D.C., Camphouse, R. C., Garner, J. W., Ismail, A. E., Kirchner, T. B., Kuhlman, K. L., 

and Nemer, M. B.. 2010. Summary Report of the CRA-2009 Performance Assessment Baseline 

Calculation. Sandia National Laboratories. Carlsbad, New Mexico, ERMS 553039. 

DOE (U.S. Department of Energy). 1996. Title 40 CFR Part 191 Compliance Certification 

Application for the Waste Isolation Pilot Plant. DOE/CAO-1996-2184. U.S. Department of 

Energy, Waste Isolation Pilot Plant, Carlsbad Area Office. Carlsbad, NM. 

DOE (U.S. Department of Energy), 2011. Panel Closure System Design, Planned Change 

Request to the EPA 40 CFR Part 194 Certification of the Waste Isolation Pilot Plant. U.S. 

Department of Energy, Carlsbad Field Office. Carlsbad, New Mexico. 

EPA (U.S. Environmental Protection Agency). 1998. Criteria for the Certification and 

Re-Certification of the Waste Isolation Pilot Plants Compliance with the 40 CFR Part 191 

Disposal Regulations: Certification Decision; Final Rule, Federal Register, Vol. 63, No. 95, 

pp. 27353-27406. U.S. Environmental Protection Agency, Office of Air and Radiation, 

Washington, D.C. 

Helton, J. et al. 1998. Uncertainty and Sensitivity Analysis Results Obtained in the 1996 

Performance Assessment for the Waste Isolation Pilot Plant. Sandia National Laboratories, 

Albuquerque, NM. SAND98-0365. 

Kicker, D.C. 2012. Analysis Package for Cuttings, Cavings, and Spallings: Panel Closure System 

Performance Assessment (PCS-2012 PA). Sandia National Laboratories, Carlsbad, NM. 

Kirchner, T. 2010. Sensitivity of the CRA-2009 Performance Assessment Baseline Calculation 

Releases to Parameters. Sandia National Laboratories, Carlsbad, NM. ERMS 552960. 

Kirchner, T. 2012. Sensitivity of the AP-161 (PCS-2012) PA Releases to Parameters. Sandia 

National Laboratories, Carlsbad, NM. 

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Malama, B. 2012. Analysis Package for Direct Brine Releases: 2012 Panel Closure System 

Performance Assessment (PCS-2012 PA). Sandia National Laboratories, Carlsbad, NM. ERMS 

558226. 

U.S. Environmental Protection Agency (EPA). 1996. 40 CFR Part 194: Criteria for the 

Certification and Recertification of the Waste Isolation Pilot Plant’s Compliance with the 40 

CFR Part 191 Disposal Regulations; Final Rule. Federal Register, Vol. 61, 5223-5245. 

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