ML23319A203
| ML23319A203 | |
| Person / Time | |
|---|---|
| Site: | 07000925 |
| Issue date: | 11/15/2023 |
| From: | Lux J Environmental Properties Management |
| To: | Miller R, James Smith Document Control Desk, Office of Nuclear Material Safety and Safeguards, State of OK, Dept of Environmental Quality (DEQ) |
| References | |
| Download: ML23319A203 (6) | |
Text
Page 1 of 6 November 15, 2023 Mr. James Smith U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Ms. Rachel Miller Oklahoma Department of Environmental Quality 707 North Robinson Oklahoma City, OK 73101 Re: Docket No. 07000925; License No. SNM-928 Cimarron Environmental Response Trust Response to November 1, 2023, Request for Additional Information Related to Nuclear Criticality Safety
Dear Recipients:
Solely as Trustee for the Cimarron Environmental Response Trust (CERT), Environmental Properties Management LLC (EPM) submits herein our response to a request for additional information (RAIs) issued by the U. S. Nuclear Regulatory Commission (NRC) on November 1, 2023.
NRC RAI NCSA-1:
Section 5.4.3.1.7.2 (2) of NUREG-1520, Standard Review Plan for Fuel Cycle Facilities License Applications, states that the applicant should commit to providing the technical basis that demonstrates (a) subcriticality under normal and credible abnormal conditions and (b) compliance with the double-contingency principle.
Section 5.4.3.1.7.2 (1)(a) of NUREG-1520, Standard Review Plan for Fuel Cycle Facilities License Applications, states that the applicant should commit to nuclear criticality safety limits being established based on analyses assuming optimum or the most reactive credible values of parameters (e.g., the most reactive conditions physically possible or bounding values limited by regulatory requirements) unless specified controls are implemented to limit parameters to a particular range of values. If less than optimum values are used, and corresponding controls are not identified, the basis will be justified in the criticality safety evaluation.
In the application dated October 2022, (ADAMS Accession No. ML22286A244), the Cimarron Environmental Response Trust, in Appendix N, stated that the relationship between the groundwater concentration of uranium and the uranium concentration of the resin used for analytical purposes is based on tests that were conducted using the selected resin material and using actual groundwater samples from the site as documented in the uranium loading study.
Page 2 of 6
- a. Provide the uranium loading study, including test data.
- b. Provide a justification for the use of the uranium loading study test data for analytical purposes, including the methodology for applying the test data, that demonstrates the assumed values for uranium concentration represent the most reactive credible values under normal and credible abnormal conditions.
EPM RESPONSE:
Provision of Uranium Loading Study, Including Test Data In 2012, EPM retained Clean Harbors to conduct treatability tests to design an ion exchange treatment system for groundwater at the Cimarron site. Clean Harbors selected DOWEX 1 resin for the tests to evaluate the capability of the resin. There were two treatment trains, one for Burial Area #1 (BA1) groundwater and one for Western Alluvial Area (WAA) groundwater.
Each treatment train consisted of five columns of resin through which groundwater would flow sequentially.
Tests were conducted using groundwater from Monitor Well 02W32 in BA1 and from Monitor Well T-62 in the WAA. These monitor wells were chosen because they contained high concentrations of uranium for the BA1 and WAA, and because they were screened in permeable material that would consistently provide sufficient groundwater for testing. The uranium concentration in groundwater from 02W32 varied from 4,300 to 5,110 micrograms per liter
(µg/L). The uranium concentration in groundwater from T-62 varied from 151 to 295 µg/L.
The results of these treatability tests were reported in the March 13, 2014, Treatability Study Report (ML19095B798). Those tests showed that the DOWEX 1 resin was effective in removing uranium from the groundwater, but it also showed that calcium and magnesium in the groundwater were capable of producing scale that would clog the resin and adversely impact the treatment process.
In 2015, EPM retained Kurion to conduct treatability tests to evaluate several ion exchange resins, to evaluate methods to prevent the production of scale in the treatment system, and to use the test results in designing a uranium treatment system. In a letter dated November 12, 2015 (ML15328020), EPM submitted 2015 Groundwater Treatability Tests (ML19095B790).
Treatability tests were also conducted to evaluate biodenitrification processes (to follow the removal of uranium from groundwater).
Kurion conducted treatability tests using groundwater from three monitor wells that contained uranium concentrations at a relatively high concentration (from Monitor Well TMW-13 in BA1),
low concentration (from Monitor Well T-70R in the WAA), and very low concentration (from Monitor Well T-54 in the WAA).
Data obtained during the 2015 treatability tests provided the information needed to determine the relationship between the concentration of uranium in influent groundwater and the absorption
Page 3 of 6 capacity of the resin. As the concentration of uranium in influent groundwater decreases over time, the concentration of uranium that the resin can absorb also decreases, so the initial uranium concentrations in the influent will result in the highest uranium concentrations in resin throughout the groundwater remediation process.
Data obtained during the 2015 treatability tests provided the information needed to adjust the pH of the influent groundwater by adding hydrochloric acid to prevent scale production.
Provision of the Justification for Using the Uranium Loading Study Test Data for Analytical Purposes Data obtained from the Clean Harbor treatability tests was used to demonstrate the capability of one particular resin to remove uranium from site groundwater, but it also demonstrated the potential for other ions (e.g., calcium and magnesium) to adversely impact the effectiveness of uranium removal by ion exchange.
Data obtained from the Kurion treatability tests defined the relationship between the concentration of uranium in influent to the resin vessel and the absorption capacity of the resin.
This information proved to be valuable in demonstrating the need for collection of in-process treatment system monitoring samples on a weekly basis throughout the first several batches of resin to enable operators of the treatment system to remove a resin vessel from the system before it reaches the fissile exemption concentration of 1 gram (g) of U-235 per 2 kilograms (kg) of non-fissile material.
Methodology for Applying the Test Data Data obtained from treatability testing was not used to determine either the anticipated concentration or the anticipated enrichment of uranium in influent to any of the ion exchange treatment systems. It was only used to determine the anticipated concentration of uranium that would be adsorbed to ion exchange resin based on the anticipated concentration of uranium in the influent groundwater.
The introduction to Appendix N, Criticality and Uranium Loading Calculations, in Facility Decommissioning Plan - Rev 3 (the D-Plan) states:
A series of calculations were performed based on the assumption that the administrative controls to maintain the safe mass limit for the processing operations and the concentration limit for packaged waste are not effective. The calculations, assuming a uranium enrichment of 7.33% and utilizing an Upper Safety Limit (USL) of [keff plus 3 sigma] <0.9, demonstrate that the maximum allowable safe fissile concentration is 8 g U-235/kg Resin. This Appendix describes the basis for these input values, presents the calculations performed, and explains why the maximum allowable safe fissile concentration cannot be attained.
Page 4 of 6 Treatability test data was not used to assign an enrichment for uranium in the calculations provided in Appendix N. Appendix N assumed a U-235 enrichment of 7.33% for influent to the ion exchange resin. This was based on the maximum enrichment measured plus 2 sigma (95%
Upper Confidence Level (UCL)) for the highest single historic measurement of any well that will feed the three treatment trains. (Page 2 of Appendix N)
Demonstration that Assumed Uranium Concentrations Represent the Most Reactive Credible Values Under Normal and Credible Abnormal Conditions Normal Conditions The process for determining the anticipated enrichment of uranium in the BA1 and WAA treatment systems is described in the Basis of Design (BOD) presented as Appendix K to the D-Plan. Section 3 of the BOD describes the process of determining representative concentrations for the groundwater in each monitor well. This process yields values for uranium concentrations at the 95% upper confidence level.
The concentration of uranium in influent to each treatment system was calculated by determining the uranium concentration at each extraction component (Section 8 of the BOD). The uranium concentration for each component is multiplied by the design flow rate for each component to obtain the mass of uranium it will contribute. The sum of the mass of uranium for all extraction components is then divided by the flow rate of all masses combined to determine the concentration of uranium in the influent.
The calculated uranium concentrations for influent groundwater are 1,215 µg/L for the BA1 treatment system and 159 µg/L for the WAA treatment system. Due to the use of 95% upper confidence values for all concentrations, the calculated influent concentrations should be considered the maximum values for normal conditions.
On September 9, 2022, EPM submitted a Technical Memorandum entitled Determination of Conservative U-235 Enrichment Levels for Groundwater at Cimarron Site (ML22273A083).
This technical memorandum calculated the U-235 enrichment level for groundwater in various areas of the Cimarron site.
The calculated U-235 enrichment value for groundwater in BA1 was 1.3%. The U-235 enrichment for WAA groundwater was 2.75%. These enrichment values, calculated at the 95%
upper confidence level, should be considered maximum values for normal conditions.
Section 8.3.2 of the D-Plan states that, based on the projected maximum influent concentration of 1,215 µg/L uranium, the lead vessel in the BA1 treatment system will not contain more than 356 g of U-235.
The calculated uranium concentrations and enrichment values for influent provided above represent the maximum values for normal conditions.
Page 5 of 6 Credible Abnormal Conditions As discussed above, Appendix N evaluated the potential for nuclear criticality by assuming a maximum value for U-235 enrichment and determining the concentration of uranium in resin that would yield an effective multiplication factor (Keff) of 0.9. Appendix N assumed a U-235 enrichment of 7.33% for influent to the ion exchange resin. This was based on the maximum enrichment measured plus 2 sigma (95% Upper Confidence Level (UCL)) for the highest single historic measurement of any well that will feed the three treatment trains. (Page 2 of Appendix N) The criticality and uranium loading calculations determined that a concentration of 8 g of U-235 per kg of resin would be required to achieve a Keff of 0.9.
Calculated values for uranium loading in resin vessels is based upon the design criterion of 760 kg of resin in a vessel; 8 g of U-235 per kg of resin would yield a total of over 5,900 g of U-235 in the resin vessel. There is no credible scenario in which 5,900 g of U-235 can physically be accumulated within a single resin vessel when processing groundwater. As stated in Section 8.3.2 of the D-Plan, the total mass of U-235 in both treatment trains combined is not expected to exceed 800 grams at any given time. The maximum U-235 loading occurs during the first two years of operations; the combined total mass of U-235 in both trains combined will drop to approximately 500 grams by year three and less than 300 grams by the end of treatment operations.
Table 17, Uranium Loading Capacities for the Three Different Groundwater Sources (in the 2015 Groundwater Treatability Tests), shows that even if groundwater from only a single well yielding an influent concentration of 4,500 µg/L uranium were treated in an ion exchange system, the Upper Bound Uranium Loading Capacity concentration is 196 milligrams of uranium per g of resin (196 g per kg). In 760 kg of resin, this would yield 149 kg of uranium. At 1.3% enrichment, the resin vessel would contain approximately 1,900 grams of U-235. This is less than one-third of the 5,900 g of U-235 that would be required to achieve a Keff of 0.9.
The most extreme credible abnormal condition would be based on the following assumptions:
The resin vessel is filled with resin to its maximum capacity, which is slightly less than 1,100 kg of resin.
Groundwater from only a single well yielding an influent concentration of 4,500 µg/L uranium is treated in an ion exchange system, The ion exchange resin adsorbs the Upper Bound Uranium Loading Capacity concentration of 196 milligrams of uranium per g of resin (196 g per kg).
In 1,100 kg of resin, 8 g of U-235 per kg of resin would yield a total of over 8,500 g of U-235 in the resin vessel. At the Upper Bound Uranium Loading Capacity of 196 g/kg, 1,100 kg of resin would adsorb approximately 216 kg of uranium. At 1.3% enrichment, the resin vessel would contain approximately 2,800 grams of U-235. This is also less than one-third of the 8,500 g of U-235 that would be required to achieve a Keff of 0.9.
Page 6 of 6 Conclusion This response references reports that contain the analytical data obtained during two treatability tests and how that data can be used to determine the relationship between influent concentration and absorption capacity for the proposed ion exchange resin. These reports were previously submitted to and docketed by the NRC.
This response emphasizes that data other than treatability test data was used to calculate the uranium concentration and U-235 enrichment for BA1 and WAA groundwater influent at a 95%
upper confidence level. These values represent the maximum credible normal operating scenario; actual influent concentrations and enrichment are not expected to be this high.
Finally, this response explains how neither a credible normal condition nor a credible abnormal condition could result in an accumulation of fissile material that would approach a Keff value of 0.9 and generate a nuclear criticality concern.
If clarification or additional information is needed, please notify us as soon as possible to minimize any potential delay in the issuance of an amended license.
Sincerely, Jeff Lux Project Manager cc: (electronic copies only)
Stephanie Anderson and Linda Gersey, NRC Region IV Paul Davis, Keisha Cornelius, Pam Dizikes, David Cates, and Jonathan Reid, DEQ NRC Public Document Room vcpsubmittals@deq.ok.gov