November 10, 2015 

MEMORANDUM TO: Doug Mandeville, Acting Chief 

Low Level Waste Branch 

Division of Decommissioning, 

 Uranium Recovery, and Waste Programs 

THRU: Christepher McKenney, Chief /RA/

Performance Assessment Branch 

Division of Decommissioning, 

 Uranium Recovery, and Waste Programs 

FROM: George Alexander, Systems Performance Analyst /RA/

Performance Assessment Branch 

Division of Decommissioning, 

 Uranium Recovery, and Waste Programs 

SUBJECT: TECHNICAL REVIEW OF “TANK 16H SPECIAL ANALYSIS FOR THE 

PERFORMANCE ASSESSMENT FOR THE H-TANK FARM AT THE 

SAVANNAH RIVER SITE”, SRR-CWDA-2014-00106, REV. 1, 

FEBRUARY 2015 (DOCKET NO. PROJ0734) 

The U.S. Nuclear Regulatory Commission (NRC) staff has performed a technical review of the 

subject document prepared by the United States Department of Energy (DOE) to support 

Tank 16H closure at the H-Area Tank Farm Facility (HTF) at the Savannah River Site (SRS). 

This technical review report supports Monitoring Factor 1.1, “Final Inventory and Risk 

Estimates”, as detailed in NRC staff’s plan for monitoring the SRS Tank Farm Facilities 

(Agencywide Documents Access and Management System (ADAMS) Accession No. 

ML15238B403). Additionally, this technical review report evaluates DOE’s effort to address 

technical issues identified in Monitoring Factors 3.1, “Hydraulic Performance of Concrete Vault 

and Annulus (As It Related to Steel Liner Corrosion and Waste Release”, and 3.5 “Vault and 

Annulus Sorption”, through analysis of an “alternate fast zone case”. Another significant change 

to DOE’s HTF performance assessment made in the Tank 16H Special Analysis was an 

increase in the distribution coefficient for iodine, which was evaluated by NRC staff under 

Monitoring Factor 4.1, “Natural Attenuation of Key Radionuclides”. DOE also updated the 

inventory for Tank 16H in this Special Analysis. The evaluation of the Tank 16H inventory 

conducted under Monitoring Factors, 1.2 “Residual Waste Sampling”, and 1.3, “Residual Waste 

Volume” is discussed in more detail under a separate technical review report (ML15301A830). 

Finally, DOE made significant changes to its biosphere model. These changes are described in 

this technical review report but will be evaluated in a separate technical review report under 

Monitoring Factor 6.2 “Model and Parameter Support”. 

CONTACT: George Alexander, NMSS/DUWP 

 (814)297-8385 
The Tank 16H Special Analysis provides useful information on the potential risks associated 

with Tank 16H. However, with regard to DOE’s alternate fast zone case to address technical 

issues identified by NRC staff under Monitoring Factors 3.1 and 3.5, the NRC staff concludes 

that additional information related to the release of radionuclides from the annulus is needed to 

have reasonable assurance that DOE disposal actions at the HTF will meet the performance 

objectives in 10 CFR Part 61, Subpart C. In addition, technical concerns identified in the Tanks 

18 and 19 Special Analysis (ML13100A230) and 5 and 6 Special Analysis (ML13273A299) 

Technical Review Reports are also relevant to the HTF performance assessment and Tank 16H 

Special Analysis and are not repeated in this report. 

With respect to Monitoring Factor 1.1, NRC staff has technical concerns related to DOE’s 

management of inventory uncertainty in the deterministic modeling used to demonstrate 

compliance with the performance objectives in 10 CFR Part 61, Subpart C, as well as 

consideration of inventory uncertainty through use of multipliers in its probabilistic modeling. 

NRC staff will continue to monitor DOE’s inventory development for the purpose of performance 

assessment calculations under Monitoring Factor 1.1, “Final Inventory and Risk Estimates”. 

However, because the probabilistic analysis is not strictly relied on, but rather, informs the 

demonstration of compliance of Tank Farm facilities with the performance objectives in 10 CFR 

Part 61, Subpart C, technical concerns related to development of inventory multipliers can be 

addressed as a longer-term activity under Monitoring Factor 6.2 “Model and Parameter 

Support”. 

With regard to DOE’s change in iodine distribution coefficient, NRC staff concludes that the 

revised values are not adequately supported. Given the potential risk-significance of the iodine 

distribution coefficient to the compliance demonstration for multiple facilities at the SRS, 

including the Saltstone Disposal Facility, NRC staff needs DOE to provide additional information 

to support its selection of distribution coefficient. 

The uncertainty in the performance assessment results based on assumptions made in the 

annular waste release model are expected to be especially risk-significant (i.e., order of 

magnitude or more impact on peak dose from the HTF). The technical issues with respect to 

the iodine distribution coefficient are expected to be less risk-significant (i.e., less than an order 

of magnitude impact on peak dose); however, the risk-significance of this parameter value could 

increase should DOE increase the value of the parameter value or make other changes to its 

model that influence the impact of the distribution coefficient on the results. The risksignificance of other changes to the HTF performance assessment model are discussed in more 

detail in separate technical review reports, as discussed above. 

Enclosure: 

Technical Review of the 

 Tank 16H Special Analysis 
-2- 

The Tank 16H Special Analysis provides useful information on the potential risks associated 

with Tank 16H. However, with regard to DOE’s alternate fast zone case to address technical 

issues identified by NRC staff under Monitoring Factors 3.1 and 3.5, the NRC staff concludes 

that additional information related to the release of radionuclides from the annulus is needed to 

have reasonable assurance that DOE disposal actions at the HTF will meet the performance 

objectives in 10 CFR Part 61, Subpart C. In addition, technical concerns identified in the Tanks 

18 and 19 (ML13100A230) and 5 and 6 Special Analysis (ML13273A299) Technical Review 

Reports are also applicable to the Tank 16H Special Analysis and are not repeated in this 

report. 

With respect to Monitoring Factor 1.1, NRC staff has technical concerns related to DOE’s 

management of inventory uncertainty in the deterministic modeling used to demonstrate 

compliance with the performance objectives in 10 CFR Part 61, Subpart C, as well as 

consideration of inventory uncertainty through use of multipliers in its probabilistic modeling. 

NRC staff will continue to monitor DOE’s inventory development for the purpose of performance 

assessment calculations under Monitoring Factor 1.1, “Final Inventory and Risk Estimates”. 

However, because the probabilistic analysis is not strictly relied on, but rather, informs the 

demonstration of compliance of Tank Farm facilities with the performance objectives in 10 CFR 

Part 61, Subpart C, technical concerns related to development of inventory multipliers can be 

addressed as a longer-term activity under Monitoring Factor 6.2 “Model and Parameter Support” 

With regard to DOE’s change in iodine distribution coefficient, NRC staff concludes that the 

revised values are not adequately supported. Given the potential risk-significance of the iodine 

distribution coefficient to the compliance demonstration for multiple facilities at the SRS, 

including the Saltstone Disposal Facility, NRC staff needs DOE to provide additional information 

to support its selection of distribution coefficient. 

The uncertainty in the performance assessment results based on assumptions made in the 

annular waste release model are expected to be especially risk-significant (i.e., order of 

magnitude or more impact on peak dose from the HTF). The technical issues with respect to 

the iodine distribution coefficient are expected to be less risk-significant (i.e., less than an order 

of magnitude impact on peak dose); however, the risk-significance of this parameter value could 

increase should DOE increase the value of the parameter value or make other changes to its 

model that influence the impact of the distribution coefficient on the results. The risksignificance of other changes to the HTF performance assessment model are discussed in more 

detail in separate technical review reports, as discussed above. 

Enclosure: 

Technical Review of the 

 Tank 16H Special Analysis 

DISTRIBUTION: CBarr CGrossman LParks MFuhrmann DPickett 

ML15301A710 

OFC NMSS:TR DUWP:LA DUWP:PM DUWP:BC NMSS:TR 

NAME GAlexander TMoon JShaffner CMcKenney GAlexander 

DATE 11/03/2015 11/04/2015 11/05/2015 11/10/15 11/10/15 

OFFICIAL RECORD COPY
Technical Review of Special Analysis for Tank 16H 

Date: October 30, 2015 

Reviewers

George Alexander, Systems Performance Analyst, U.S. Nuclear Regulatory Commission 

Cynthia Barr, Sr. Systems Performance Analyst, U.S. Nuclear Regulatory Commission 

Christopher Grossman, Systems Performance Analyst, U.S. Nuclear Regulatory Commission 

Leah Parks, Systems Performance Analyst, U.S. Nuclear Regulatory Commission. 

Primary Document

SRR-CWDA-2014-00106, Revision 1, “Tank 16 Special Analysis for the Performance 

Assessment for the H-Tank Farm at the Savannah River Site”, Savannah River Remediation, 

LLC, Closure and Waste Disposal authority, Aiken, South Carolina, February 2015. 

Summary of Technical Reports

SRR-CWDA-2014-00106, Revision 1, “Tank 16 Special Analysis for the Performance 

Assessment for the H-Tank Farm at the Savannah River Site”, February 2015. 

The Tank 16H Special Analysis updates the H Tank Farm (HTF) Performance Assessment (PA) 

model (SRR-CWDA-2010-00128, Rev. 1), including: (i) an updated inventory, (ii) separation of 

the annulus and sand pad inventories, (iii) updated sorption coefficients for iodine, (iv) a 

sensitivity analysis for annular release, (v) the use of a revised dose methodology, and (vi) a 

correction to the H-Tank Farm model. The results from the Tank 16H Special Analysis show the 

projected peak dose within 100,000 years to be approximately 0.02 mSv/yr (2 mrem/yr) from 

I-129 occurring at around 4,000 years after closure (see Figures 1 and 2). 

Figure 1. 100-Meter MOP Groundwater Pathway Dose within 10,000 Years (SRR-CWDA2014-00106, Revision 1, Figure 6.4-11) 

Enclosure 
- 2 - 

Figure 2. 100-Meter MOP Groundwater Pathway Dose within 100,000 Years for Each 

Sector - Tank 16H Contribution Only (SRR-CWDA-2014-00106, Revision 1, Figure ES-2) 

Inventory

The H-Area Tank Farm Waste Tank Closure Inventory report (SRR-CWDA-2010-00023, 

Revision 4) provides the radiological characterization at the presumed date of closure for use in 

the Performance Assessment model. Revision 4 of this report updates the inventories for Tanks 

16H and 12H to reflect the final inventory determination for Tank 16H and new inventory 

information for Tank 12H. In addition, the annulus and sand pad inventories for Type I and II 

tanks have been updated with final Tank 16H sampling and analysis results and volume 

estimates. This document also provides information regarding inventory multipliers to account 

for uncertainty in projected inventories. The inventory adjustments made in this report are 

incorporated into the HTF modeling in the Tank 16H Special Analysis. 

Of the 54 initial radionuclides remaining following initial screenings, 15 additional radionuclides 

were eliminated from future consideration for Tank 16H based on characterization data. These 

radionuclides are Ac-227, Al- 26, Eu-152, Eu-154, H-3, Pd-107, Pt-193, Ra-228, Se-79, Sm151, Sn-126, Th-229, Th-232, U-232, and U-236. These radionuclides were screened out 

because the activity anticipated to remain after operational closure is not expected to contribute 

to radiological impacts. 

As discussed in more detail in the Tank 16H Inventory technical review report (ML15301A830), 

the volume of Tank 16H was updated to reflect the final volume determination of (1.2m3

) 330 gal 

for the tank floor and (7.2 m3

) 1,910 gallons in the annulus. Also, the residual material volume 

from the equipment in the Tank 16H primary tank, (0.1 m3

) 26.3 gallons, was added to the Tank 

16H floor volume to give a final residual material volume of the Tank 16H floor of approximately 

1.3 m3

 (356 gal). The volume of the primary sand pad is still assumed to be 5 m3 (1,300 gal) 

and the secondary sand pad is still assumed to be 0.1 m3

 (26 gal). Final residual volume 
- 3 - 

estimates for the primary tank and annulus used in Tank 16H Special Analysis (SRR-CWDA2014-00071) versus the HTF PA estimates are shown below in Table 1. Details regarding the 

statistical analysis for the final concentrations assumed for the Tank 16H primary floor and 

annulus are contained in SRNL-STI-2014-00321. The concentrations in the Tank 16H primary 

and secondary sand pads are assumed to be the same as those in the Tank 16H annulus. 

Tables 5.01, 5.03, 5.05, and 5.06 in the Tank 16H Special Analysis provide the final residual 

inventories at final facility closure for the waste tank, annulus, primary, and secondary sand 

pads, respectively. Table 2 provides a summary of the potentially risk-significant increases in 

radionuclide inventories compared to the inventory assumed in the HTF performance 

assessment. 

Table 1. Tank 16H Residual Volume Estimates (gal)* 

Tank 16H HTF PA Tank 16H SA 

Primary Tank 300 330 

Annulus 3,300 1,900 

* To convert gal to m3, multiply by 3.8 x 10-3

Table 2. Potentially risk-significant increases in radionuclide inventories 

Tank 16H Primary Liner Radionuclide Inventory (Ci)* 

Element HTF PA Tank 16H SA Factor 

Increase 

I-129 5.3E-5 1.3E-3 25 

Sr-90 2.2E3 9.4E3 4 

* To convert Ci to Bq, multiply by 3.7 x 1010

Tank 16H Annulus Radionuclide Inventory (Ci) 

Element HTF PA Tank 16H SA Factor 

Increase 

I-129 1.7E-4 7.9E3 46 

Tank 16H Primary Sand Pad Inventory (Ci) 

Element HTF PA Tank 16H SA Factor 

Increase 

I-129 6.9E-5 5.4E-3 78 

Pu-239 1.4E0 3.2E0 2 

Sr-90 3.1E3 6.9E3 2 

Tank 16H Secondary Sand Pad Inventory (Ci) 

Element HTF PA Tank 16H SA Factor 

Increase 

I-129 1.4E-6 1.1E-4 79 

Pu-239 2.9E-2 6.4E-2 2 

Sr-90 6.3E1 1.4E2 2 
- 4 - 

Using the latest sample results from the Bulk Oxalic Acid Cleaning and the preliminary volume 

estimates, DOE adjusted the assigned inventory for Tank 12H. Although final statistical 

analysis of the Tank 12H residual samples had not been completed at the time of this report, the 

updated inventory incorporated knowledge from process samples taken during cleaning. The 

changes are summarized in an Appendix to this TRR. The final inventory for Tank 12H will be 

evaluated by the NRC staff in a separate technical review report. 

To account for uncertainty in the inventory, multipliers between 0.01 and 10 were applied to the 

assigned inventories for each radionuclide in the HTF PA. The radionuclide inventory 

multipliers were modeled with a log uniform distribution to account for a range of values. The 

maximum of the distribution is either 1 (if the radionuclide was not detected and the inventory 

was based on the detection limit) or 10 (if the radionuclide was detected). DOE compares the 

Tank 16H final inventory values to the assigned HTF PA inventory values. For all constituents 

the maximum underestimates are close to a factor of 10. DOE does not apply uncertainty 

factors to the primary or secondary sand pad inventory or ancillary equipment inventory. DOE 

states that the peak dose is driven by the inventory in the primary tank and annulus as opposed 

to the sand pads and there is a lack of data to define the uncertainty in these components. 

Waste Release

In addition to the updated inventories, revisions to the HTF PA model in the Tank 16H Special 

Analysis include: (i) segmentation of the annulus inventories in the PORFLOW transport model, 

(ii) updated Kd values for iodine, (iii) a revised dose calculation methodology, and (iv) new 

sensitivity analyses related to radionuclide release from the annulus and sand pads. 

For the Type I and II tanks, which includes Tank 16H, the bottom half-inch of the 

“ANNULUS_GROUT” was defined as a new distinct material zone “ANN_WASTE”. The 

“ANN_WASTE” zone was assigned the same physical properties as the “CONTAM_ZONE”, 

which is located inside the primary liner, and with Reduced Region II cement Kd values and no 

solubility control. As with the “CONTAM_ZONE” and overlying reducing tank grout, the 

“ANN_WASTE” zone Eh and pH transitions are linked to the overlying “ANNULUS_GROUT”. 

DOE conducted a sensitivity analysis to address NRC staff concerns (see NRC Staff Evaluation 

section of this report) related to the risk associated with preferential pathways and 

contamination located outside of the primary containment in several tank annuli in HTF, 

including Tank 16H. This analysis is referred to as the alternate fast zone (AFZ) submodel, 

which is carried out using the updated HTF GoldSim SRS HTF v1.010 Rad model. The AFZ for 

Type I and II tanks includes several updates, as described in Section 6.4.6.3 in the Tank 16H 

Special Analysis and is summarized below: 

• Groundwater flow into and out of the tank system is through the upgradient and 

downgradient construction seams, respectively. 

• For the Type I tanks, groundwater flows circumferentially around the annulus (see Figure 

6.4-15 in the Tank 16H Special Analysis). 

• For the Type II tanks, groundwater traverses the annulus grout and the primary sand 

layer (see Figure 6.4-16 in the Tank 16H Special Analysis). 

• Flow through the pathway is controlled, in part, by a 1% hydraulic gradient between the 

most upgradient and downgradient portions of the tank system. 
- 5 - 

• Hydraulic conductivities through the pathway are based on the time-dependent hydraulic 

conductivities used for the annulus grout in the HTF PORFLOW base case. 

• The construction joint does not act to limit flow through the preferential pathway. 

• Flow through the preferential pathway is limited by the annulus grout. 

• All cementitious materials, which are subject to sorption, are assumed to be oxidized 

and use the Kd values for Oxidized Region III. 

• The sand pad contamination zones are not assumed to be subject to sorption. 

DOE evaluated the release of Sr-90 and Cs-137 for an HTF Inadvertent Human Intruder (IHI), 

because of the short half-life of these radionuclides relative to the travel time to the 100-m 

boundary. DOE’s AFZ analysis indicated that the release of Sr-90 and Cs-137 from the annulus 

has a negligible impact on doses when compared to the HTF PA Base Case. The AFZ analysis 

also demonstrated that the assumption of a low hydraulic conductivity of the annulus fill grout, 

which is assumed to be 2.1E-9 cm/s from 0 to 5,100 years, allows for the decay of Sr-90 and 

Cs-137 prior to release. DOE also stated that even if a continuous zone of high conductivity 

could occur, the source exposure area would have to be unrealistically large to produce 

significant radionuclide releases. Accordingly, DOE concluded that the HTF PA Base Case 

model provides reasonable assurance of meeting the performance objectives. 

Far-Field Transport

In the Tank 16H Special Analysis, Kd values for iodine in the natural environment were updated 

based on recent observations and research (SRNL-STI-2012-00518). Previously, DOE 

assumed that all of the iodine in the natural environment exists as iodide. However, Otosaka et 

al. (2011) observed that iodine existed in F-Area Seepage Basin wells as iodide (15%), iodate 

(42%), and organo-iodide (43%), including “background” wells that were considered 

representative of the far-field at F-Area. Based on these observations and subsequent 

research, which included laboratory experiments to study the sorption of iodide and iodate, Kd

values for iodine were increased from 0.3 mL/g to 1 mL/g for sandy soils and from 0.9 mL/g to 3 

mL/g for clayey soil1

. 

Revised Dose Methodology 

DOE has revised its dose methodology for all liquid waste performance assessments at SRS 

and documented the approach and parameter values in SRR-CWDA-2013-00058. DOE’s 

approach remains generally consistent with past approaches. The NRC staff plans to develop a 

TRR in the future that documents its review of the revised methodology. The NRC staff’s review 

will follow-up on concerns identified during previous reviews, such as DOE’s basis for drinking 

water consumption rates, selection of plant types and associated transfer factors treatment of 

uncertainty in plant transfer factors, and any significant changes in the revised dose 

methodology from previous PAs, including DOE’s use of per-capita consumption rates and ageand gender-weighting of dose conversion factors. 

 

1

 It is important to note that only the Gordon Confining Unit and backfill are assigned the material property of 

clayey soil in the far-field and near-field models, respectively, and the clayey soil distribution coefficient is 

expected to have minimal impact on transport from H-Area Tank Farm sources to the compliance boundary based 

on previous NRC reviews. 
- 6 - 

NRC Staff Evaluation

Inventory

The updated inventories used in the Tank 16H Special Analysis are an improvement to the 

projected inventories used previously. Nonetheless, post-waste retrieval inventories should still 

be considered estimates, because radionuclide concentrations and waste volumes remaining in 

the tanks after waste retrieval operations are completed are uncertain. Given the final 

inventories of cleaned tanks are uncertain, it is not clear to the NRC staff that inventory 

uncertainty is properly managed for cleaned tanks in deterministic analyses (e.g., the reference 

case volume is expected to have a significant amount of uncertainty associated with it, yet “best 

estimates” of volume that may be biased low are used to determine the residual waste 

inventory). Potential issues with sample representativeness discussed in the Tank 16H 

Inventory technical review report (ML15301A830) may lead to an under-estimate (or overestimate) of residual waste concentrations for key radionuclides in the Tank 16H annulus. DOE 

should consider whether it has appropriately managed volume and sampling and analysis 

uncertainty in the deterministic reference case relied on to demonstrate compliance with the 

performance objectives. 

Table 5.0-1 in the Tank 16H Special Analysis indicates that key radionuclides such as I-129 and 

Sr-90 in the primary liner of Tank 16H were significantly underestimated by factors of 25 and 4, 

respectively. The annular inventory for I-129 is also significantly underestimated by almost a 

factor of 502

. During the July 28-29 Onsite Observation Visit (ML15239A628), NRC staff 

inquired about the cause of this underestimation and the potential for the inventory in other 

tanks to be similarly underestimated. DOE responded that I-129 in the tanks had been 

assumed to be soluble, but appears to be in a less mobile form. DOE indicated that it is unclear 

if the iodine has been present in a less mobile complex, if the cleaning process resulted in a 

less mobile form (e.g., iodate), or if the iodine was taken up by silver or mercury. As discussed 

further in the far-field evaluation section, it is unclear to NRC staff in what chemical form the 

iodine exists in the tank and annulus of Tank 16H and how that chemical form may change 

under grouted conditions. Additionally, it is unclear to NRC staff what chemical form iodine may 

exist in the far-field of H-Tank Farm Facility following release from the engineered system. DOE 

was unable to offer a clear explanation for the underestimation of the inventory of Sr-90 in both 

the primary liner and sand pads of Tank 16H in the July 28-29 Onsite Observation Visit. 

During the July 28-29 Onsite Observation Visit (ML15239A628), NRC also inquired about the 

basis for the revision of the residual waste volume in the Tank 16H annulus from 3,300 gal to 

1,900 gal. DOE discussed that the revised inventory was determined, in part, by marking the 

shaft of an auger tool when the top and bottom of the waste was reached, to estimate the waste 

thickness. As the previous thickness was based primarily on visual observation, DOE indicated 

that it has more confidence in the volume estimates based on measured values. NRC staff 

discusses technical concerns related to DOE’s waste sampling and analysis, and volume 

estimation methods used to develop the final inventory for Tank 16H in a separate technical 

review report (ML15301A830), focused primarily on the more risk-significant annular inventory. 

 

2

 It is important to note that the inventory of I-129 was underestimated by a factor of approximately 80 in the sand 

pads, which suggests that the I-129 concentration in the annulus of Tank 16H was even more grossly 

underestimated than the final inventory, but due to the decrease in the estimated annular waste volume, the 

increase in the I-129 inventory in the annulus was only a factor of about 50. 
- 7 - 

Although the estimate for the residual waste volume in the annulus has been reduced by more 

than 40%, a potentially risk-significant radionuclide inventory nonetheless remains. 

DOE incorporates uncertainty into inventory projections for tanks that have not been cleaned 

through the use of inventory multipliers that range from 0.01 to 10 times the estimated inventory. 

The NRC staff has expressed concern in prior reviews with the use of a minimum inventory 

multiplier of 0.01, while the maximum inventory multiplier is 1 (for undetected radionuclides 

whose inventory is based on the detection limit) or 10 (for detected radionuclides) 

(ML13273A299). NRC staff notes that there were less cases in which radionuclide inventories 

were underestimated by more than a factor of 10 for Tank 16H than for Tanks 5F and 6F, but 

the example of the potentially risk-significant I-129 being underestimated for Tank 16H is an 

indication that the maximum multiplier of 10 may not be high enough to bound uncertainty. 

DOE should continue to compare the assigned PA inventory values and the final determined 

inventory values of operationally closed tanks to gauge the appropriateness of the multipliers. 

When radionuclides are significantly underestimated, DOE should make an effort to understand 

the reason for the underestimation by reviewing past sampling data and historical knowledge in 

order to better inform projected inventories for tanks that have not yet been cleaned. For 

example, DOE should address whether I-129 is potentially underestimated in other tanks that 

are yet to be cleaned. 

Regarding the sand pad inventory for Type II Tanks, NRC staff notes that a lack of data on the 

uncertainty for the sand pads is not a good basis for lack of consideration of inventory 

uncertainty. There is uncertainty surrounding the concentration of the material in the annulus. 

Any waste material that may have migrated from the annulus to the primary and secondary 

sand pads in Tank 16H following the 1960 leakage event was not directly contacted in 

subsequent annulus waste retrieval campaigns, and therefore, may have higher concentrations 

of more soluble materials. Furthermore, the material in the sand pad does not have any silica 

additions from sandblasting. The silica increased the volume of waste in the annulus which may 

have lowered the concentrations of waste materials in the annulus. On the other hand, 

formation of less soluble, sodium aluminum silicate compounds may have increased 

concentrations of certain key radionuclides. Considering all of the tank inspection and cleaning 

activities conducted in the annulus of Tank 16H, it is unclear if the concentrations of individual 

key radionuclides in the annulus relative to the concentrations in the sand pad are higher or 

lower. For example, as described in WSRC-STI-2008-00203, the concentrations in the interior 

of the dehumidification duct (which does not have any silica content) contains more water 

soluble material than the other two samples from outside the duct as might be expected 

because this material would be less accessible to the washing/waste removal done in the 

annulus in the past. 

The secondary sand pad inventory is assumed to be 0.1 m3

 (26 gal) as an estimate of what was 

potentially released into the environment. The NRC staff believes that uncertainty in the 

secondary sand pad inventory should be considered. According to DP-1358, a maximum of 2.6 

m3

 (700 gal) of waste rose above the top of the secondary containment pan of Tank 16H for 

about six hours on September 8, 1960. From this information, the uncertainty should be 

bounded by the maximum amount that rose above the secondary containment pan instead of 

relying on the deterministic value of 0.1 m3

 (26 gal), which represents 10 gallons more than the 

estimated void volume of the vault construction joint that was implicated as the release pathway 

from the Tank 16H annulus to the environment. 
- 8 - 

Still, the deterministic inventories assumed for the primary sand pads in Tanks 14H and 16H are 

likely biased high by the assumption that the entire sand pad pore volume is assumed to be 

saturated with residual material. For Tanks 13H and 15H, DOE assumes that a smaller volume 

(0.378 m3

 (100 gal)) is in the primary sand pad layer because DOE believes the amount of 

material that leaked from the primary tank is limited, and therefore, not much material reached 

the sand pad. The cleaning of Tanks 13H and 15H will not provide additional information on the 

amount of material that leaked from the primary tank into the annulus and then the sand pads, 

because the sand pads are not directly accessible. DOE should address whether the 

deterministic estimates for the sand pads in these tanks reasonably bound the uncertainty given 

that no multipliers are assumed for the sand pads and the volumes are unlikely to change. 

NRC staff will continue to monitor DOE’s parameterization of final radionuclide inventories in 

special analyses under Monitoring Factor 1.1, “Final Inventory and Risk Estimates” listed in 

NRC staff’s plan for monitoring at the Tank Farm Facilities (ML15238B403). NRC will also 

continue to monitor DOE’s basis for concluding that all potentially risk-significant radionuclides 

have been identified and are targeted for analysis under Monitoring Factor 1.2, “Residual Waste 

Sampling.” 

In summary, NRC staff has technical concerns related to DOE’s management of inventory 

uncertainty in the deterministic modeling used to demonstrate compliance with the performance 

objectives in 10 CFR Part 61, Subpart C, as well as consideration of inventory uncertainty 

through use of multipliers in its probabilistic modeling. NRC staff will continue to monitor DOE’s 

inventory development for the purpose of performance assessment calculations under 

Monitoring Factor 1.1, “Final Inventory and Risk Estimates”. However, because the probabilistic 

analysis is not strictly relied on, but rather, informs the demonstration of compliance of Tank 

Farm facilities with the performance objectives in 10 CFR Part 61, Subpart C, technical 

concerns related to development of inventory multipliers can be addressed as a longer-term 

activity under Monitoring Factor 6.2 “Model and Parameter Support” in the NRC staff’s plan for 

monitoring SRS Tank Farm Facilities (ML15238B403). 

Waste Release

In the Tank 16H Special Analysis, DOE redefines the bottom half inch of the previous 

“ANNULUS_GROUT” zone as the “ANN_WASTE” zone; however, DOE indicates the same 

material properties assumed for the “CONTAM_ZONE” are applied to the “ANN_WASTE” 

ZONE, or Reduced Region II3

 sorption (but no solubility control). In the base case analysis, 

chemical transitions in the “ANN_WASTE” zone are dictated by the overlying annulus grout. 

This assumption implies that the annulus waste and overlying grout are well-mixed, which is not 

supported, particularly for waste located in the annulus duct. Additional support is needed for 

the base case assumption that annular grout will represent a significant barrier to key 

radionuclide release from the annulus. 

DOE simulated an alternate fast zone conceptual model as reported in the Tank 16H Special 

Analysis to address NRC staff’s TER recommendations related to the risk associated with the 

Tank 16H annulus and sand pads. However, the AFZ sensitivity analysis that was conducted in 

the Tank 16H Special Analysis does not adequately address the concerns raised in NRC staff’s 

Technical Evaluation Report (TER) for the HTF (ML14094A496). Namely, in Sections 4.2.9.3 

and 4.2.9.4 of the HTF TER, NRC staff states the following: 

 

3

 In the alternate fast zone analysis, DOE assumes oxidized region III conditions for the cementitious materials. 
- 9 - 

• “The NRC staff is concerned that risk from the radionuclide inventories outside of the 

primary liners is not adequately accounted for in DOE’s analyses. The NRC staff 

recommends that DOE conduct a more comprehensive analysis of the potential release 

of radionuclides from the annuli and sand pads in the Type I and Type II tanks. 

Implementation of this recommendation is necessary for the NRC staff to have 

reasonable assurance that the performance objectives in 10 CFR Part 61, Subpart C 

can be met. Dose projections from the potential release of the radionuclides in the 

annuli and sand pads are likely to be very sensitive to several key assumptions, which 

should be well supported. These assumptions include, but are not limited to (1) the 

assumed release scenario; (2) the chemical composition of the infiltrating water; (3) the 

volumetric flow rate through grouted tanks, including shrinkage gaps and cracks; and (4) 

the solubility of the annulus and sand pad waste. If the possibility of rise and fall of the 

water table in the vicinity of the Type I and II tanks cannot be excluded, DOE should 

evaluate a scenario where water drains from any gaps in the annulus and sand pad

regions.” 

• “Grouting of the tanks and annuli will help limit the presence of preferential pathways; 

however, grout shrinkage and degradation are likely to result in preferential pathways.” 

• “Grouting of the tanks and annuli will help limit the presence of preferential pathways 

and the hydraulic head associated with the fully and partially submerged tanks; however, 

grouting will not necessarily eliminate flow. Because of the activity of key short lived 

(e.g., Cs-137, Sr-90) and long-lived radionuclides (e.g., Pu-239) in the annulus and sand 

pads and the high solubility of this waste (Section 3.4.2.2; SRR-CWDA-2010-00128, 

Rev. 1) even minimal flow through the grouted annuli and sand pads could result in a 

significant dose.” 

The AFZ analysis implemented by DOE does not address all of NRC staff’s TER 

recommendations made during consultation. Namely, DOE (i) did not evaluate the impact of 

shrinkage gaps and cracks in the grouted annulus, but instead assumed that the annular grout 

constituted a barrier to flow, thereby effectively eliminating the impact of preferential flow 

through the annulus, (ii) did not evaluate the impact of rise and fall of the water table, which 

NRC staff thinks could result in the greatest risk associated with waste in the annulus and sand 

pads, and (iii) did not evaluate long-lived radionuclides (e.g., Np-237, Pu-239). 

The assumption that the annulus grout is a significant flow barrier is problematic in this 

sensitivity case. NRC staff intended for DOE to run a case with a preferential pathway through 

the entire tank system, and not simulate a low conductivity grout that restricts flow in the 

preferential pathway through the annulus. Unless it can be demonstrated that shrinkage or 

cracking will not occur in the grout annulus, NRC staff continues to recommend that DOE 

evaluate radionuclide release from the annulus and sand pads with a continuous preferential 

pathway. Secondly, DOE assumes that the fast pathway is saturated with a 1% hydraulic 

gradient between the most upgradient and downgradient portions of the tank system (see 

Figure 3, Scenario 1). In the July 28-29, 2015, Onsite Observation Visit (ML15239A628), NRC 

staff reiterated their concern of the risk associated with the potential rise and fall of the water 

table. NRC staff thinks that the rise and fall of the water table is likely to be more risk significant 

for radionuclide release from the annulus than under a saturated flow condition. A rise and fall 

of the water table could be simulated with a unit hydraulic gradient (versus 0.01) and likely 

corresponds to a greater volume of water contacting the residual waste in the annulus (see 
- 10 - 

Figure 3, Scenarios 2a and 2b). If the possibility of this scenario cannot be excluded, it should 

be evaluated by DOE. In addition, the basis for the 1% hydraulic gradient to represent the 

potential across the resistive engineered barrier is not clear. If DOE relies on the AFZ analysis 

with the 1% hydraulic gradient, additional information should be provided to support this value. 

Lastly, the inventories of long-lived radionuclides (e.g., Pu-239, Np-237) are potentially risk 

significant and should be included in the AFZ analysis. Based on these limitations of the AFZ 

analysis, NRC staff concludes that DOE’s Tank 16H Special Analysis does not adequately 

evaluate the potential risk associated with the Tank 16H annulus and sand pads. To address 

this technical issue, DOE could run additional simulations that consider the essential elements 

listed in the bullets above (e.g., consideration of shrinkage gaps, rise and fall of the water table, 

and long-lived radionuclides). 

NRC staff concerns related to DOE’s 10 CFR 61.41 compliance demonstration for the H-Tank 

Farm are also relevant to 10 CFR 61.42 compliance demonstration, because of the groundwater 

pathway (see Sections 4.2.16 and 4.2.17 of the NRC staff’s HTF TER, ML14094A514). Further, 

NRC staff continues to have concerns with the disproportionate risk that short-lived 

radionuclides (e.g., Sr-90, Cs-137) may pose for inadvertent intruders at the 1-m boundary. 

Related to the AFZ analysis, DOE discussed that even if a continuous zone of high conductivity 

could occur, an unrealistically large source area would have to be exposed for significant 

radionuclide release. NRC staff agrees that source contact area could be limited in the vadose 

zone. However, it is unclear to NRC staff that the residual annulus waste in Tank 16H would 

not be significantly contacted during saturated or partially saturated conditions. 

DOE added the capability to import diffusion data in the updated GoldSim model; however, DOE 

does not appear to use PORFLOW inputs or otherwise consider diffusion in the alternate fast 

zone model implemented in GoldSim (e.g., SRR-CWDA-2014-00060 indicates that no diffusion 

data were imported from PORFLOW and no results from PORFLOW were used in the alternate 

fast zone calculations). Comparisons against PORFLOW simulations showed that the alternate 

fast zone model oftentimes under-predicted the release due to the lack of consideration of 

diffusion through the wall. If diffusion could be an important transport mechanism controlling the 

release of radioactivity from the engineered system, DOE should consider diffusive transport 

through the engineered materials. 

During the July 28-29, 2015, Onsite Observation Visit (ML15239A628), NRC inquired as to the 

adequacy of the GoldSim model in accurately simulating the impact of preferential pathways 

through the engineered system without additional PORFLOW analysis and abstraction. DOE 

responded that PORFLOW simulations helped inform the GoldSim model, although PORFLOW 

information was not directly used in the GoldSim calculations. The GoldSim model relied on 

spreadsheet calculations for flow fields. DOE should consider whether a more complex model 

is needed to evaluate the impact of alternative conceptual models for annular waste release. 
- 10 - 

 

Figure 3. Water movement through grouted tank system under constant and fluctuating 

water table scenarios (adapted from SRR-CWDA-2014-00106)
- 11 - 

Far-Field Transport

The revised sediment Kd values4

 for iodine are based on field observations and recent 

experimental data. The observations from the F-Area Seepage Basins show that iodine exists 

in the subsurface as iodate and organo-iodine, in addition to iodide. The NRC staff agrees that 

the potential exists for I-129 released from the tank farms to be converted from iodide to iodate 

and organo-iodide. However, NRC staff have several concerns related to the level of support 

for the revised Kd values related to: (i) the stability of iodate, (ii) the use of a composite Kd value 

to represent multiple iodine species, (iii) an apparent disconnect between pH, speciation, and 

sorption, (iv) the spatial and temporal variability of field conditions, (v) representativeness of FArea Seepage Basin aquifer sediments to the SRS Tank Farm far-field environments, and (vi) 

chemical form of iodine expected to be released from the tanks. 

• Figure 8 in SRNL-STI-2012-00518 shows the measured Kd values for iodide and iodate 

at weeks 8 and 12. Although the iodide appears to be stable, the Kd values for iodate 

decrease significantly between weeks 8 and 12, which is consistent with iodate gradually 

converting to iodide. Additional information is needed to evaluate the conditions under 

which more strongly sorbing iodate and organo-iodine species are stable in the far-field 

at the SRS Tank Farm Facilities. 

• In SRNL-STI-2012-00518, the authors calculate a composite Kd value to represent 

different species of iodine as a model simplification because the PA modeling currently 

considers only a single iodine Kd value. If the mechanisms of iodine sorption are not well 

understood or well represented in the performance assessment model, there is a 

potential to significantly under-estimate the dose associated with iodine through use of a 

composite Kd. NRC staff previously identified issues associated with plutonium Kd

averaging (see Appendix E of the SRS Tank Farm Facilities Monitoring PlanML15238B403). While the impact of Kd averaging may be minimal for the relatively low 

values of distribution coefficient selected for use in the Tank 16H Special Analysis for 

iodine, the impact of Kd averaging should be evaluated to support the approach used in 

the Tank 16H SA. 

• In SRNL-STI-2012-00518, the authors discuss that iodate is favored under more neutral 

and basic environments (e.g., pH>6) versus more acidic environments (e.g., pH<4) and 

that elevated iodate concentrations are consistent with increased sorption. However, the 

sorption of both iodide and iodate decreases significantly starting at pH 4 and tends 

towards zero as the pH approaches 6.75. Accordingly, the pH condition that support the 

stability of iodate might only narrowly intersect with the pH environment where the 

sorption of iodine species is non-negligible. For example, the background pH in nonimpacted SRS groundwater is approximately 5-6, and iodine release from the grouted 

tank system is expected to occur in a pH that ranges from 9 to 11. 

• Table 2 from Otosaka et al. (2011) and summarized again in Table 8 of SRNL-STI-2012-

00518, shows that the speciation of iodine between the three “background” wells for the 

F-Area Seepage Basins is highly variable. It is unclear to NRC staff how spatial and 

temporal variability in chemical conditions in the engineered and natural system at the Fand H-Area Tank Farms, may influence the speciation, and therefore sorption, of iodine. 

The speciation of iodine appears to very sensitive to a complex series of interdependent 

 

4

 The revised iodine Kd values result in approximately a factor of two decrease in the projected dose due to I-129. 
- 12 - 

variables: pH, Eh, presence of organic matter and microbial activity. Additional support 

should be provided for the spatial and temporal stability of iodate under field conditions, 

including the influence of cementitious materials on aquifer pH. 

• As indicated in SRNL-STI-2012-00518, the clay content of SRS soils is important to 

iodate sorption because it has organic matter and the mechanism for sorption is the 

binding to the organic matter. It is unclear if the “background” wells at the F-Area 

Seepage Basin are similar in composition to the soils in the far-field environments of Fand H-Area with respect to clay content. 

• SRNL-STI-2012-00518 indicates that once iodide was added to the SRS subsurface 

sediment (“North Borrow” sediments), negligible amounts of iodate were formed. 

Additionally, due to the very low sediment organic matter concentrations, little organoiodine was observed in the aqueous phase. The experiments in SRNL-STI-2012-00518 

do not appear to be consistent with the observations at the “background” wells at F-Area 

Seepage Basin reported in Otosaka et al. (2011). Additional information is needed to 

better understand the conditions where more strongly sorbing forms of iodine are stable 

in the environs of the Tank Farm Facilities. Additionally, the chemical form of iodine in 

the tank waste may be an important factor with respect to the speciation of iodine in the 

natural system once released from the engineered system. Additional information is 

needed on the chemical forms of iodine expected in the residual tank waste at the time 

of closure and how this chemical form may change over time. 

Kaplan et al. (2011) discusses that only under extremely oxidizing conditions should iodine exist 

as iodate in the terrestrial environment. While the field data reported in Otosaka et al. (2011) 

show significant fractions of iodate present at less than extremely oxidizing conditions, oxidation 

of iodide to iodate raises a potential concern. If the environmental conditions are sufficiently 

oxidizing to result in the formation of iodate, NRC staff are concerned that other redox-sensitive 

radionuclides (e.g., Pu) could be transported more quickly in the environment than assumed in 

the FTF and HTF PAs. DOE discussed during the Onsite Observation Visit (ML15239A628) 

that they are working on an update to a site-wide Kd report, which will also include data from the 

lysimeter study. NRC staff review of the updated Kd report will be conducted under Monitoring 

Factor 4.1, “Natural Attenuation of Key Radionuclides.”

During the July 28-29, 2015, Onsite Observation Visit (ML15239A628), NRC staff commented 

that the conceptual model for the different configurations is not clear in the probabilistic model 

(i.e., it was not clear if the conceptual models defined in deterministic modeling were preserved 

in the probabilistic modeling). For example, the probabilistic models vary (i) Case, (ii) cement 

degradation times, and (iii) steel liner failure times. In the deterministic modeling, DOE 

assumes that in certain Cases (e.g., Cases C and E that include a preferential pathway and the 

cement degradation times are relatively prolonged, similar to the base or reference case), flow 

occurs primarily through the preferential pathway and not the overlying reducing tank grout, 

leading to faster chemical transitions (e.g., faster transition from reducing to oxidizing conditions 

that can lead to higher solubility of key radionuclides). Because both the (i) Case and (ii) the 

cement degradation times vary in the probabilistic model, the underlying conceptual models 

defined in the deterministic modeling are ambiguous. NRC staff asked DOE to clarify what 

material controlled the chemistry of the contaminated zone in the probabilistic model. DOE took 

NRC’s question as a follow-up action from the July 28-29 Onsite Observation Visit. Following 
- 13 - 

the onsite observation, DOE provided a written response in SRR-CWDA-2015-00117. DOE 

responded that the flow rates through the materials, pore volume of the materials, and number 

of pore volumes to transition from reducing to oxidizing conditions and lower pH (based on 

geochemical modeling), determine the chemical state for the various materials (or segments), 

including the contaminated zone. NRC staff understood this response to mean that the 

overlying tank grout did not control the chemistry of the contaminated zone. This response is 

inconsistent with NRC staff’s understanding of what was done for the deterministic modeling in 

the H-Tank Farm PA and the probabilistic modeling in the F-Tank Farm PA. For example, an 

assumption was made in the F-Tank Farm PA that the chemistry of the contaminated zone was 

controlled by the overlying grout for all cases except for Case G, which was run in response to 

an NRC request for additional information. Additionally, in the HTF performance assessment 

(deterministic model), the selection of Case (e.g., Case A-E) determines whether the chemical 

transition is controlled by the overlying tank grout (Cases A, B, and D) or whether the chemical 

transitions are rapid due to flow that occurs primarily through the preferential pathway (Cases C 

and E where limited groundwater conditioning via interaction with the reducing tank grout 

occurs). NRC staff plan to discuss this technical issue further with DOE in a subsequent 

teleconference or a future onsite observation visit. 

Furthermore, because there is limited basis or support for the assigned probabilistic parameter 

distributions, the full range of plausible parameter space may not have been evaluated in the 

probabilistic analysis. Solubility, for example, is constrained to non-risk-significant values for 

most key radionuclides, although potentially risk-significant values for plutonium were observed 

in Tank 18 residual waste (ML12272A082). DOE has not demonstrated that the relatively high 

solubility plutonium phase(s) will be converted to a low solubility phase(s) under grouted 

conditions. DOE did evaluate in a deterministic sensitivity analysis (e.g., risk-significant Pu 

solubility was evaluated in the Tanks 18 and 19 Special Analysis for what was described as a 

“conservative Eh”), but this risk-significant solubility was not evaluated in the probabilistic 

assessment. Accordingly, it is difficult to draw conclusions from the probabilistic assessment. 

Figures 5.3-1 through 5.3-4 in SRR-CWDA-2014-00060 provide results for the “all cases” and 

base case probabilistic models for either 1000 or 10,000 years. The results of the analyses 

reveal that Sr-90 is one of the key radionuclides contributing the largest doses in the analyses 

particularly over shorter evaluation periods. Although the mean doses are less than 1 mrem/yr, 

the results seem to indicate that for some realizations, Sr-90 dose can be risk-significant, and 

that short-lived radionuclides can drive the dose results. NRC staff plans to investigate these 

realizations in more detail and will discuss with DOE in a future teleconference or onsite 

observation. 

Revised Dose Methodology 

NRC staff will evaluate DOE’s revised dose methodology in a future technical review report. 

Follow-up Actions

NRC staff will continue to monitor DOE’s parameterization of final radionuclide inventories in 

special analyses under Monitoring Factor 1.1, “Final Inventory and Risk Estimates” listed in 

NRC staff’s plan for monitoring at the Tank Farm Facilities (ML15238B403). 

Under Monitoring Factor 3.1, “Hydraulic Performance of Concrete Vault and Annulus (As It 

Relates to Steel Liner Corrosion and Waste Release” and Monitoring Factor 3.5, “Vault and 

Annulus Sorption”, NRC staff will continue to monitor DOE’s analysis of the potential release of 
- 14 - 

radionuclides from the annulus and sand pads, including: (i) a continuous preferential pathway, 

(ii) a fluctuating water table, and (iii) long-lived radionuclides. NRC staff will also evaluate 

DOE’s implicit assumption that the annulus waste and overlying grout is well-mixed. 

Although not specifically listed under Monitoring Factor 4.1, “Natural Attenuation of Key 

Radionuclides,” NRC staff will monitor DOE’s development of information to support the sorption 

of iodine in the natural environment based on its risk significance. 

Open Issues

There are no Open Issues. 

Conclusions

As a result of the review of several DOE documents that support the Tank 16H Special Analysis 

and discussions with DOE during the July 28-29 Onsite Observation Visit, the NRC staff 

concludes that the Tank 16H Special Analysis provides useful information on the potential risks 

associated with Tank 16H. However, the NRC staff also concludes that additional information 

related to the release of radionuclides from the annulus is needed to have reasonable 

assurance that DOE disposal actions at the HTF will meet the performance objectives in 10 

CFR Part 61, Subpart C. To reach these conclusions, the NRC staff focused on a number of 

areas listed in the SRS Tank Farms Monitoring Plan (ML15238B403) related to Monitoring 

Factor 1.1, “Final Inventory and Risk Estimates”, Monitoring Factor 3.1, “Hydraulic Performance 

of Concrete Vault and Annulus (As It Related to Steel Liner Corrosion and Waste Release)”, 

Monitoring Factor 3.5, “Vault and Annulus Sorption”, and Monitoring Factor 4.1, “Natural 

Attenuation of Key Radionuclides” as detailed in NRC staff’s plan for monitoring the SRS Tank 

Farm Facilities. 

With respect to Monitoring Factor 1.1, NRC staff has technical concerns related to DOE’s 

management of inventory uncertainty in the deterministic modeling used to demonstrate 

compliance with the performance objectives in 10 CFR Part 61, Subpart C, as well as 

consideration of inventory uncertainty through use of multipliers in its probabilistic modeling. 

NRC staff will continue to monitor DOE’s inventory development for the purpose of performance 

assessment calculations under Monitoring Factor 1.1, “Final Inventory and Risk Estimates”. 

However, because the probabilistic analysis is not strictly relied on, but rather, informs the 

demonstration of compliance of Tank Farm facilities with the performance objectives in 10 CFR 

Part 61, Subpart C, technical concerns related to development of inventory multipliers can be 

addressed as a longer-term activity under Monitoring Factor 6.2 “Model and Parameter 

Support”. 

With regard to DOE’s change in iodine distribution coefficient, NRC staff concludes that the 

revised values are not adequately supported. Given the potential risk-significance of the iodine 

distribution coefficient to the compliance demonstration for multiple facilities at the SRS, 

including the Saltstone Disposal Facility, NRC staff needss DOE to provide additional 

information to support its selection of distribution coefficient. 

The uncertainty in the performance assessment results based on assumptions made in the 

annular waste release model are expected to be especially risk-significant (i.e., order of 

magnitude or more impact on peak dose from the HTF). The technical issues with respect to 

the iodine distribution coefficient are expected to be less risk-significant (i.e., less than an order 

of magnitude impact on peak dose); however, the risk-significance of this parameter value could 
- 15 - 

increase should DOE increase the value of the parameter value or make other changes to its 

model that influence the impact of the distribution coefficient on the results. The risksignificance of other changes to the HTF performance assessment model are discussed in more 

detail in separate technical review reports, as discussed above. 

Finally, technical concerns identified in the Tanks 18 and 19 Special Analysis (ML13100A230) 

and 5 and 6 Special Analysis (ML13273A299) Technical Review Reports are also relevant to 

the HTF performance assessment and Tank 16H Special Analysis and have not been repeated 

in this report. 

 
- 16 - 

References

DOE-STD-1196-2011, DOE Standard Derived Concentration Technical Standard, U.S. 

Department of Energy, Washington, DC, April 2011. 

DP-1358, Poe, W.L. “Leakage From Waste Tank 16, Amount, Fate, and Impact.” DP-1358. 

Aiken, South Carolina: E.I. du Pont de Nemours and Company and Savannah River Laboratory. 

November 1974. 

EPA-600-R-090-052F, Exposure Factors Handbook, 2011 Edition, U.S. Environmental 

Protection Agency, Washington DC, September 2011. 

Kaplan, D. I., Roberts, K. A., Schwehr, K. A., Lilley, M. S., Brinkmeyer, R., Denham, M. E., 

Diprete, D., Li, H. P., Powell, B. A., Xu, C., Yeager, C. M., Zhang, S. J., and Santschi, P. 

H. (2011). Evaluation of a radioiodine plume increasing in concentration at the Savannah 

River Site. Environmental Science & Technology 45, 489-495. 

ML12272A082. Technical Review: Waste Release and Solubility Related 

Documents Prepared by United States Department of Energy to Support Final Basis for 

Section 3116 Determination for the F-Area Tank Farm Facility at Savannah River Site.

Memorandum to Janelle Jesse. ADAMS Accession No. ML12272A082. Rockville, Maryland: 

U.S. Nuclear Regulatory Commission. May 31, 2013. 

ML13100A230. Technical Review of Tank 18 and 19 Special Analysis for the Performance 

Assessment for the F-Tank Farm at the Savannah River Site. Memorandum to Gregory Suber. 

ADAMS Accession No. ML13100A230. Rockville, Maryland: U.S. Nuclear Regulatory 

Commission. October 17, 2012. 

ML13273A299. Technical Review of Tanks 5 and 6 Special Analysis at F-Tank Farm 

Facility, Savannah River Site. Memorandum to Gregory Suber. ADAMS Accession No. 

ML13273A299. Rockville, Maryland: U.S. Nuclear Regulatory Commission. October 4, 2013. 

ML15238B403. U.S. Nuclear Regulatory Commission Plan for Monitoring Disposal Actions 

Taken by the U.S. Department of Energy at the Savannah River Site F-Area and H-Area Tank 

Farm Facilities in Accordance With the National Defense Authorization Act for Fiscal Year 2005. 

Washington, DC: U.S. Nuclear Regulatory Commission. October 2015. 

ML15239A628. The U.S. Nuclear Regulatory Commission July 28-29, 2015 Onsite Observation 

Visit Report for the Savannah River Site Combined F and H-Tank Farm Closure. Memorandum 

to Jean Ridley. ADAMS Accession No. ML15239A628. Rockville, Maryland: U.S. Nuclear 

Regulatory Commission. October 2015. 

ML15301A830. Technical Review of Final Inventory Documentation for Tank 16H at Savannah 

River Site. Memorandum to Douglas Mandeville. ADAMS Accession No. ML15301A830. 

Rockville, Maryland: U.S. Nuclear Regulatory Commission. October 30, 2015. 

Otosaka, S., Schwehr, K. A., Kaplan, D. I., Roberts, D. A., Zhang, S., Xu, C., Li, H.P., Ho, Y.F., 

Brinkmeyer, R., Yeager, C. M., and Santschi, P. H. (2011). Transformation and Transport 

Processes of I-127 and I-129 Species in an Acidic Groundwater Plume at the Savannah River 

Site. The Science of the Total Environment 409, 3857-3865. 
- 17 - 

SRR-CWDA-2010-00128, Performance Assessment for the H-Area Tank Farm at the Savannah 

River Site, Savannah River Site, Aiken, SC, Rev. 1, November 2012. 

SRR-CWDA-2013-00058, Dose Calculation Methodology for Liquid Waste Performance 

Assessments at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, July 2014. 

SRR-CWDA-2014-00060, Updates to the H-Area Tank Farm Stochastic Fate and Transport 

Model, Savannah River Site, Aiken, SC, Rev. 0, January 2015. 

SRR-CWDA-2014-00071, Tank 16 Inventory Determination, Savannah River Site, Aiken, SC, 

Rev. 0, October 23, 2014. 

SRR-CWDA-2015-00117, Follow-up Information for Action Item 12 from the U.S. Nuclear 

Regulatory Commission F and H Area Tank Farms Onsite Observation Visit on July 28-29, 

2015. Savannah River Remediation, Savannah River Site, Aiken, SC, September 1, 2015. 

SRNL-STI-2012-00518, Kaplan, D.I., Radioiodine Geochemistry in the SRS Subsurface 

Environment, Savannah River Site, Aiken, SC, Rev. 0, May 2013. 

SRNL-STI-2014-00612, Flach, G.P. and Taylor, G.A., H-Area Tank Farm Tank 16 Special 

Analysis Model Support, Savannah River Site, Aiken, SC, Rev. 0, December 23, 2014. 

WSRC-STI-2008-00203, Rev. 0, Hay, M.S. “Characterization of Samples from Tank 16H 

Annulus.” WSRC-STI-2008-00203, Rev. 0. Aiken, South Carolina: Savannah River 

National Laboratory. 2008. 

 
- 18 - 

Appendix: Summary of Changes to Tank 12H Inventory in the Tank 16H SA 

The H-Area Tank Farm Waste Tank Closure Inventory report (SRR-CWDA-2010-00023, 

Revision 4) provides the radiological characterization at the presumed date of closure for use in 

the Performance Assessment model. In addition to including final inventories for Tank 16H, 

Revision 4 of this report updates the inventories for Tank 12H based on new inventory 

information for Tank 12H. Although final statistical analysis of the Tank 12H residual samples 

had not been completed at the time of this report, the updated inventory incorporated 

knowledge from process samples taken during cleaning. 

The Tank 12H inventory adjustments are based on Tank 12H heel material that will not be seen 

in the Type I and II tanks. Therefore, the inventory in Tank 12H is treated independently and is 

not part of the Type I and II tank grouping.

Of the original 54 radionuclides, the following 19 radionuclides have been screened out of future 

consideration for Tank 12H because the curies anticipated to remain after operational closure 

are not expected to contribute to radiological impacts: Ac-227, Al-26, Cf-249, Cf-251, Cl-36, Cm247, Cm-248, Co-60, Eu-152, Eu-154, H-3, K-40, Pd-107, Pt-193, Pu-242, Pu-244, Se-79, Sm151, and U-236. 

The residual volume of the Tank 12H tank floor is adjusted to be 5.7 m3

 (1,500 gal). Also an 

estimated 1.5 m3

 (400 gal) of additional material is encrusted on the vertical cooling coils. The 

annulus is assigned a volume of 0.1 m3

 (25 gal) of dried salt material. 

Radionuclides of interest which were increased include the following: 

• Cs-137 was increased from 790 Ci to 2,500 curies to account for the material expected 

to remain after BOAC. 

• I-129 was increased from 2.8E-04 Ci to 2.6E-02 Ci. DOE expects this to account for any 

additional I-129 in the Cooling Coil External Scale Material Inventory. 

• Np-237 was increased from 0.21 Ci to 0.72 Ci. 

• Pu-238 was increased from 6,500 Ci to 9,820 Ci. 

• Pu-239 was increased from 80 Ci to 394 Ci. 

• Pu-240 was increased from 50 Ci to 394 Ci. 

• Pu-241 was increased from 760 Ci to 2,460 Ci 

• Sr-90 was increased from 14,000 Ci to 130,000 Ci to account for material expected to 

remain after BOAC. 

• Tc-99 was increased from 8.1 Ci to 12 curies to account for potential Tc-99 in the 

Cooling Coil External Scale Material Inventory. 

• Th-232 was increased from 0.029 Ci to 0.055 Ci. 

• U-232 was increased from the 2.10E-03 Ci to 2.10E-02 Ci. 

• U-233 was increased from 0.59 Ci to 3.3 Ci. 

• U-234 was increased from 0.096 Ci to 1.68 Ci. 

• U-238 was increased from 0.029 Ci to 0.184 Ci.