Fourth Set of EPA Completeness Comment 1

ENCLOSURE

FOURTH SET OF EPA COMPLETENESS COMMENTS FOR CRA 2014

4-C-1. Waste Incompatibilities and Gas Generation. The WIPP Technical Assessment Team 

investigated the mechanisms and chemical reactions that resulted in the breach of at least one 

waste drum and release of waste material in the WIPP on February 14, 2014 (SRNL 2015). This 

report identified the presence of chemically incompatible contents in LANL Drum 68660 from 

waste stream LA-MIN02-V.001 as the cause of the release; the drum contents included nitrate 

salt residues, organic sorbent (SWheat Scoop® kitty litter), and neutralizing agent 

(triethanolamine or TEA), which represents a mixture of fuels and oxidizers. This mixture and 

the configuration of materials in the drum supported chemical reaction, thermal runaway, gas 

build-up and eventual venting of radioactive materials and hot matter (SRNL 2015). 

The WIPP performance assessment currently includes only microbial gas generation via 

degradation of CPR and anoxic corrosion of steel as significant gas generation mechanisms. 

Screening of chemical gas generation FEPs (CRA-2014 Appendix SCR Section SCR-6.5.1) did 

not consider gas generation caused by chemical incompatibility such as occurred in Drum 68660. 

Please provide a detailed assessment of whether the contents of other drums from the LAMIN02-V.001 waste stream could have similar chemical incompatibilities that may cause gas 

generation sufficient to affect performance assessment. Also, if the SWheat Scoop® kitty litter 

was used in any other waste streams that have been emplaced in the WIPP, the DOE should 

discuss the potential effects on performance assessment of possible gas generation from these 

waste streams in its response to the Agency.

SRNL (Savannah River National Laboratory). 2015. Waste Isolation Pilot Plant Technical 

Assessment Team Report. SRNL-RP-2014-01198, Revision 0.

Wallace, T.C. 2014. Understanding the “What” and the “Why” of February 14, 2014. Los 

Alamos National Laboratory, LA-UR-14-2701. 

4-C-2. Reassessment of Inundated Anoxic Steel Corrosion Rate Data. 

a. Experimental Data Used As Inputs For Parameter CORRMCO2 –The DOE needs to 

justify the values it has adopted for the parameter CORRMCO2 given the range of

existing data. In the CRA-2014 PA the parameter CORRMCO2 has a range, distribution 

and median value that was modified from what was adopted in the CCA. The 

modification was based on experimental corrosion data under inundated conditions, at 1 

atm and 0 ppm CO2, as reported in Roselle (2013). Repository brines are predicted to be 

in equilibrium with CO2 gas concentrations of 3.2 ppm CO2 (10-5.5 atm, Brush and 

Domski 2013) which is above 0 ppm CO2. Additional corrosion experiments were 

performed by Roselle at CO2 concentrations of 350 ppm, 1500 ppm and 3500 ppm, with 
Fourth Set of EPA Completeness Comment 2

and without organic ligands, and for partially and fully immersed coupons. This range 

includes the predicted CO2 gas concentrations of 3.2 ppm. The corrosion rates determined 

by Roselle (2013) for experiments at 0 and 350 ppm CO2 concentrations are summarized 

in the figure below. The collective results from these experiments indicate corrosion does 

occur above 0 ppm and up to 350 ppm CO2 and corroborate relevant data that indicates 

corrosion will occur at CO2 concentrations above 0 ppm.

Please provide a justification for why the experimental corrosion data gathered from 

experiments above 0 ppm CO2 concentrations were not included in the development of 

the parameter CORRMCO2. 

b. Justify the Distribution of Parameter CORRMCO2 – In previous WIPP PAs, the 

lower limit of the steel corrosion rate was set equal to 0 m/sec, and, accordingly, the 

lower limit of the sampled range for CORRMCO2 should be 0 m/s. This lower limit is 

consistent with passivation of the steel surface by H2S observed and reported in Telander 

and Westerman (1997). Telander and Westerman (1993, 1997) reported the results of 

anoxic corrosion experiments at H2 and N2 pressures up to 127 atm, which are applicable 

given the expected hydrostatic pressures anticipated in the WIPP repository. Based on an 

experiment with a N2 pressure of 10 atm, Telander and Westerman (1997) recommended 

a corrosion rate of 2.25 × 10-14 m/s using results from the final 12 months of a 24-month 

experiment. EPA (1998) noted the effects of increased pressure on the steel corrosion rate 

in the experiments by Telander and Westerman (1993, 1997) and directed that the upper 

limit for CORRMCO2 used in the CCA PAVT should be increased to 3.17 × 10-14 m/s 

0

5

10

15

20

25

30

Observations

Corrosion Rate, m/s

Roselle (2013) Steel Corrosion Rate Data

0 ppm 350 ppm
Fourth Set of EPA Completeness Comment 3

(see Table Parameter CORRMCO2). Retaining this upper limit encompasses most, but 

not all, of the corrosion rate data measured by Roselle (2013) and includes consideration 

of the results reported by Telander and Westerman (1993, 1997).

The Roselle (2013) anoxic corrosion experiments with 0 ppm and 350 ppm CO2

concentrations bracket anticipated CO2 gas phase concentrations. It appears that the 350 

ppm CO2 corrosion data should have been included in the reassessment of the 

CORRMCO2 parameter because the experimental data indicate that steel corrosion rate 

will occur up to 350 ppm CO2. However, the 350 ppm CO2 corrosion data were not 

included in establishing the parameter valuation.

Please update the range, median and distribution for the CORRMCO2 parameter that 

reflects this experimental data. 

Please provide justification as to why a uniform distribution for parameter CORRMCO2 

was not adopted in the CRA-2014 PA. 

Table Parameter CORRMCO2 (m/s)

WIPP PA Distribution Minimum Maximum Median

CCA PA Uniform 0.0 1.59 × 10-14 7.94 × 10-15

CCA PAVT 

CRA-2004 PA and PABC

CRA-2009 PA and PABC

Uniform 0.0 3.17 × 10-14 1.58 × 10-14

CRA-2014 PA Student-t 3.29 × 10-16 1.84 × 10-14 6.06 × 10-15

Brush, L.H., and P.S. Domski. 2013. Prediction of Baseline Actinide Solubilities for the WIPP 

CRA-2014 PA. Sandia National Laboratories, ERMS 559138.

EPA. 1998. Technical Support Document for Section 194.23: Parameter Justification Report.

Docket No. A-93-02 V-B-14.

Roselle, G.T. 2013. Determination of Corrosion Rates from Iron/Lead Corrosion Experiments to 

be Used for Gas Generation Calculations. Sandia National Laboratories, ERMS 559077.

Telander, M.R., and R.E. Westerman. 1993. Hydrogen Generation by Metal Corrosion in 

Simulated Waste Isolation Pilot Plant Environments: Progress Report for the Period November 

1989 Through December 1992. Prepared by Pacific Northwest National Laboratory for Sandia 

National Laboratory, SAND92-7347.

Telander, M.R., and R.E. Westerman. 1997. Hydrogen Generation by Metal Corrosion in 

Simulated Waste Isolation Pilot Plant Environments. Prepared by Pacific Northwest National 

Laboratory for Sandia National Laboratory, SAND96-2538.
Fourth Set of EPA Completeness Comment 4

4-C-3. Humid Steel Corrosion Rates. Roselle (2013) states that steel coupons hung in a humid 

environment exhibited essentially no corrosion regardless of CO2 concentration. This statement 

contradicts the experimental data (reported in Roselle, 2013) conducted under humid 

experimental conditions, where samples were tested at 0 and 350 ppm CO2. These experiments 

indicate corrosion does occur under humid conditions, with a mean corrosion rate of 3.0 × 10-16

m/s and median rate or 1.1 × 10-16 m/s, both positive values. The provided histogram of the 

corrosion rate data, obtained with gas phase CO2 concentrations of 0 ppm and 350 ppm—which 

bracket anticipated repository conditions—demonstrates that the humid corrosion rate could be 

greater than zero. 

Please justify why the DOE does not use the available and WIPP-relevant data in the derivation 

of corrosion rates that indicate corrosion will occur under humid conditions.

Roselle, G.T. 2013. Determination of Corrosion Rates from Iron/Lead Corrosion Experiments to 

be Used for Gas Generation Calculations. Sandia National Laboratories, ERMS 559077.

4-C-4. Steel Surface Area per Unit Volume in the Repository. The anoxic steel gas generation 

rate due to corrosion is proportional to the steel surface area per unit volume, Ds, (Appendix PA 

Equation PA.67) in the repository. The parameter Ds is defined by the following equation and 

inputs: 

Ds = Adnd/VR (Appendix PA equation PA.75), 

Where, 

0

1

2

3

4

5

6

Observations

Corrosion Rate, m/s

Humid Iron Corrosion Tests, 0 and 350 ppm CO2
Fourth Set of EPA Completeness Comment 5

Ad - is the surface area of steel associated with a waste disposal drum 

(REFCON:ASDRUM, m2/drum), 

VR - is the initial volume of a single room in the repository (REFCON:VROOM, 

m3), and 

nd, - is the ideal number of waste drums that can be close-packed into a single

room (REFCON:DRROOM). 

The input value for Ad used in the above equation (equation PA.75) has not changed since the 

CCA PAVT (Kicker and Herrick 2013), even though acceptance of significant quantities of 

AMWTP compressed waste since 2004 is likely to have increased the value for Ds. In addition 

the input nd has not changed since the CCA, when it was based on calculations performed before 

waste placement began (Kicker and Herrick 2013). Steel surface area per unit repository volume 

is important to both gas generation through anoxic corrosion and the repository water balance. 

Therefore, please update the calculation to account for the increased steel surface area that is 

representative of current and projected repository conditions. This calculation should include a 

reevaluation of the input Ad based on currently available data and include the amounts of 

compressed waste in the repository. 

Please provide evidence that the calculation includes an update to the input value for nd that is 

consistent with actual waste placement practices. 

Kicker, D.C, and C.G. Herrick. 2013. Parameter Summary Report for the Compliance 

Recertification Application, Rev. 0. Sandia National Laboratories, ERMS 560298.

4-C-5. Steel Sulfidation Rate. The rate of gas production by sulfidation of iron in steel is 

determined by the rate of H2S production through microbial degradation of cellulose and the 

stoichiometric coefficient for gas generation by sulfidation of steel (Appendix PA, equation 

PA.68). This formulation includes the assumption that all H2S produced by microbial 

degradation of cellulose will instantaneously react to produce iron sulfide. Please provide the 

basis for this assumption, particularly in light of the Telander and Westerman (1997) 

experimental data that shows H2S formed a passivating layer on steel and essentially halted steel 

corrosion.

4-C-6. Effects of Green Rust Formation on Gas Generation Stoichiometry. The 

stoichiometric coefficient used in PA for gas generation due to steel corrosion (STOIFX) has 

been maintained at its historical value of 1. This parameter value of “1” assumes no green rust 

will form on steel. The assumption is contradicted in Appendix SOTERM Section 2.3.4 of the 

CRA-2014, which includes the following statement: 

Roselle (Roselle 2013) states that green rust is the most likely corrosion product in 

experiments with low atmospheric CO2 concentrations (< 350 ppm).
Fourth Set of EPA Completeness Comment 6

Roselle (2013 Section 4.3) then contradicts the above statement stating current experiments 

indicate no evidence that corrosion products will occur on steel under WIPP-relevant conditions. 

He further claims results from recent experiments are similar to what was observed in the earlier 

Telander and Westerman (1993) corrosion investigations [Fe(OH)2]. However, corrosion 

products have been reported by Roselle (2013) in WIPP related experiments and contradicts 

Roselle’s own assumption reported in Roselle, 2013 Section 4.3. Archeological evidence 

indicates corrosion products will occur under harsh anaerobic conditions. Réguer et al. (2007) 

and Rémazeilles et al. (2009) indicate long term corrosion products have formed on iron artifacts 

under anaerobic conditions and saline conditions. This is further corroboration that corrosion 

products, such as green rust, could form on WIPP steel. Production of corrosion products could 

result in a higher value of STOIFX, as demonstrated in the following equation: 

6Fe + CO2 + 15H2O = Fe6(OH)12CO3•2H2O + 7 H2

Given the contradictions, the DOE should discuss why a value of “1” should be used for the 

parameter STOIFX. In this discussion, the DOE needs to address all available data, including the 

solids characterization results from the iron corrosion experiments performed by Roselle 

(Roselle 2009, 2010, 2011a, 2011b) and analogue data that indicate corrosion occurs in 

anaerobic and saline high chloride media (e.g., Réguer et al. 2007, Rémazeilles et al. 2009) in the 

development of the parameter STOIFX.

Réguer, S., P. Dillman and F. Mirambet. 2007. Buried iron archaeological artefacts: corrosion 

mechanisms related to the presence of Cl-containing phases. Corrosion Science 49:2726-2744. 

Rémazeilles, C., D. Neff, F. Kergourlay, E. Foy, E. Conforto, S. Réguer, P. Refait and P. 

Dillmann. 2009. Mechanisms of long-term anaerobic corrosion of iron archaeological artefacts in 

seawater. Corrosion Science 51:2932-2041.

Roselle, G.T. 2009. Iron and Lead Corrosion in WIPP-Relevant Conditions: Six Month Results. 

Milestone report, October 7, 2009, Sandia National Laboratories, ERMS 546084. 

Roselle, G.T. 2010. Iron and Lead Corrosion in WIPP-Relevant Conditions: 12 Month Results. 

Milestone report, October 14, 2010, Sandia National Laboratories, ERMS 554383. 

Roselle, G.T. 2011a. Iron and Lead Corrosion in WIPP-Relevant Conditions: 18 Month Results. 

Milestone report, May 3, 2011, Sandia National Laboratories, ERMS 555246. 

Roselle, G.T. 2011b. Iron and Lead Corrosion in WIPP-Relevant Conditions: 24 Month Results. 

Milestone report, January 5, 2011, Sandia National Laboratories, ERMS 554715. 

Roselle, G.T. 2013. Determination of Corrosion Rates from Iron/Lead Corrosion Experiments to 

be Used for Gas Generation Calculations. Sandia National Laboratories, ERMS 559077.
Fourth Set of EPA Completeness Comment 7

Telander, M.R., and R.E. Westerman. 1993. Hydrogen Generation by Metal Corrosion in 

Simulated Waste Isolation Pilot Plant Environments: Progress Report for the Period November 

1989 Through December 1992. Prepared by Pacific Northwest National Laboratory for Sandia 

National Laboratory, SAND92-7347.

4-(14)15-1 Plan View of the Repository with Updated Dimensions. The repository layout has 

changed since the 2009 recertification. Please provide a plan view of the repository design. This 

should include the dimensions and locations of the repository and should provide the dimensions 

of the current and planned excavated areas and the run-of-mine salt panel closure system. 

4-23-1 Volume of Repository Operations and Experimental Areas. Please clarify the planned 

excavated volume of the repository operations and experimental areas, accounting for past and

current activities and excavations for planned experimental activities in the underground.

On August 11, 2011, the DOE submitted to the EPA a Planned Change Notice to initiate mining 

activities for a ‘contingently funded’ Salt Disposal Investigations (SDI) project in the WIPP 

underground. The planned SDI test required increasing the repository footprint in the 

experimental area by mining an additional 61,000 m3. On June 20, 2012, the DOE notified the 

EPA that an alternative to the SDI had been developed entitled the Salt Defense Disposal 

Investigations (SDDI). The SDDI test plans to mine 31,000 m3in the experimental area, 

approximately half of the SDI design. Verbal communication between Department and Agency 

staff indicated the SDI test was cancelled due to funding issues. 

The modeled experimental volume area in the CRA 2014 has been increased to reflect the 

“contingently funded” SDI volume of 61,000 m3and not 31,000 m3volume, reflective of the 

SDDI test. The volume of excavation that the DOE is actually planning for the testing is unclear. 

U.S. Department of Energy (DOE), 2011. Notification of Intent to Begin the Salt Disposal 

Investigations. Letter from Edward Ziemianski to Jonathan Edwards dated August 11, 2011. 

Carlsbad, New Mexico.

U.S. Department of Energy (DOE), 2012. Notification of Revisions to the Salt Disposal 

Investigations Testing Concepts. Letter from Jose R. Franco to Jonathan Edwards dated June 20, 

2012. Carlsbad, New Mexico.