ML20055E049

Response to Comments on U.S. DOE, WVDP Air Study

ML20055E049
Person / Time
Site:	West Valley Demonstration Project
Issue date:	02/19/2020
From:	Bower B US Dept of Energy, West Valley Demonstration Project
To:	Amy Snyder NRC/NMSS/DDUWP/MDB
References
Download: ML20055E049 (21)

Text

Department of Energy West Valley Demonstration Project 10282 Rock Springs Road West Valley, NY 14171-9799 February 19, 2020 Amy Snyder, Senior Project Manager Materials Decommissioning Branch Division of Decommissioning, Uranium Recovery, and Waste Programs

. Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Two White Flint North 11545 Rockville Pike Rockville, MD 20852-:2738

SUBJECT:

Response to Comments on U.S. Department of Energy West Valley Demonstration Project (DOE-WVDP) Final "Study" Document: "Vitrification Facility Air Emissions During Open.;.Air Demolition, Measured vs. Predicted," WVDP-579, Rev. 0 (Docket No. 05000201 (POOM-032))

REFERENCE:

Letter (381880), A. M. Snyder to B. C. Bower, "Comments on U.S. Department of Energy West Valley Demonstration ProjectFinal 'Study' Document:

'Vitrification Facility Air Emissions During Open-Air Demolition, Measured vs..

Predicted,' WVDP-579, Rev. 0 (Docket No. 05000201 (POOM-032)), dated December 4, 2019

Dear Ms. Snyder:

DOE-WVDP would like to thank the U.S. Nuclear Regulatory Commission for their December 4, 2019, correspondence (Reference) providing comments on the Vitrification Facility alternate method validation study report (WVDP-579, Rev. 0). Please find the responses to those comments enclosed. We look forward to further discussion during your next visit to the WVDP.

If you have any questions please contact Moira N. Maloney of my staff at (716) 942-4255.

Sincerely,

&c_~~..

(. ~an C. Bower, Director West Valley Demonstration Project

Enclosure:

Responses to NRC Staff Comments on the Vitrification Building Demolition.

Validation cc: See Page 2 JTD:382233 - 454.2.2

Ms. Amy Snyder

- cc: T. D. Dogal, CHBWV, WV-lOPLEX, w/enc.

J. R. Fox, CHBWV, WV-PL6, w/enc, D. P. Klenk, CHBWV, WV-PL6, w/enc.

A. F. Steiner, CHBWV, WV-PL6, w/enc.

R. E. Steiner, CHBWV, WV-PL6, e/enc.

K. R. Whitham, CHBWV, WV-PL6, w/enc.

J. D. Williams, CHBWV, AC-BUS, w/enc.

M. N. Maloney, DOE-WVDP,AC-DOE, w/enc.

P. J. Bembia, NYSERDA, AC-NYS, w/enc.

JTD:382233 - 454.2.2 February 19, 2020

DEPARTMENT OF ENERGY (DOE)

WEST VALLEY DEMONSTRATION PROJECT (WVDP)

Responses to NRC Staff Comments on the Vitrification Building Demolition Validation Comment Number Page No, Section or Paragraph No.

Comments General Background Information in Support of these Comments:

Response

Date: February 13, 2020 The "Vitrification Facility Air Emissions during Open-Air Demolition, Measured vs. Predicted" validation study presented in WVDP-579, Rev. 0 was an exercise that the US EPA required WVDP perform before the alternative methodology (AM) presented in WVDP-579, Appendix F, "Methodology for Radionuclide Source Term Calculations for Air Emissions from Demolition Activities," could be used to estimate emissions from the Main Plant Process Building (MPPB) demolition. The AM was prepared in anticipation of demolition of the Vitrification Facility (VF) with conservative emission factors before*

EPA required that the WVDP perform a validation study. The primary concern when the AM was being developed was the appropriate emission factors used to predict VF emissions during hydraulic hammering. Although there was some experience throughout the DOE complex with this method, the data available on which to base an emission factor was limited. At the time, this demolition methodology was thought to be very aggressive. Therefore, the AM selected very conservative factors. The fact that the hydraulic hammering emission factor used in the AM was indeed conservative was borne out in the results of the validation study. Consequently, for future emissions predictions from hydraulic hammering, it was recommended that the hydraulic hammering emissions factor be modified to be less conservative.

Once EPA imposed the requirement that a validation study be performed during the VF demolition as a condition of use of the AM for other facilities at the WVDP, a Test Plan for the validation study was developed that was reviewed and approved by EPA (included as Appendix E ir;i the Validation Study Document). The location of the samplers, a proposed statistical test, the use of AERMOD, and the analysis to be performed were all contained in the Test Plan and agreed upon by EPA and DOE. The EPA and DOE also discussed the methods used to arrive at the Material at Risk (MAR), which was taken from the WVDP Characterization Database. An exemptiqn calculation for VF demolition was subsequently prepared based on the MAR in the Characterization Database and the AM emissions factors, which was submitted to EPA.

1

r

,Page No;-

Comment' Number

.Comments AERMOD allows source emissions to be input on an hourly basis in an "hourly emission file." AERMOD calculates hourly concentrations based on the*

hourly meteorological data and the source emission files. The use of "hourly emission files" for open air demolition allows incorporating multiple emission sources occurring in the same day (such as demolition emissions during hydraulic hammering, emissions associated with waste loading, and emissions from stationary debris piles). -

For the AERMOD input for the VF validation study, each activity was treated as a separate source and each source had its own hourly emission file. For example:

emissions from hydraulic hammering might have_ occurred between the hours of 0800 and 1200, emissions from waste loading might have occurred between 1300 and 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />, and emissions from the pile might have occurred from 0000 to 2400 hours0.0278 days <br />0.667 hours <br />0.00397 weeks <br />9.132e-4 months <br />, during all 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the day.

Three hourly emissions files would be created for this day, one for each activity as follows:

hammering would have emissions from 0800 to 1200 and would be zero for the other hours, waste loading would have emissions from 1300 to 1500 and would be zero for the other hours, and the pile would have emissions from 0000 to 2400 (for every hour) based on the quantity of material in the pile for any given hour, with no periods of zero emissions during the day.

Hourly emission files were built for every day of the validation study.

For each hourly emissions file, AERMOD computes an hourly concentration file with predicted concentrations at fixed distances downwind based on the meteorological conditions for each hour_ of the day. AERMOD sums these concentrations to generate an hour-by-hour areal distribution of the plume.

2

Comment Number Page No, Section or Paragraph No.

Comments

Response

1.

Selection of radionuclides for the validation modeling and sampling approach: The U.S. Nuclear Regulatory Commission (NRC) staff has _technical questions regarding the type of analytical measurements and sampling methods used.

1.a.1 Page 1 1.a.2 Page 1 What is the basis for the list of radionuclides selected for the AERMOD1 validation study?

Footnote 1 : The AERMOD air dispersion model was developed by the American Meteorological Society/Environmental Protection Agency Regulatory Model Improvement Committee (AERMIC) Model.

Please explain why Tc-99 and 1-129 were not considered in the validation study (e.g., low risk significance or lack of data on air concentrations for these radionuclides).

3 West Valley Demonstration Project (WVDP) maintains a characterization database that contains the radionuclide contamination levels remaining in the various rooms and spaces throughout the facility. The radionuclide list and associated concentrations used in the validation study were taken directly from the characterization database. For the validation study, there were no additions or deletions to the radionuclides listed in the characterization database.

The list of radionuclides in the database was determined based on laboratory analysis of waste material removed from the s ecific s aces and rooms.

Tc-99 and 1-129 were not analyzed for in the samples collected to determine the MAR for the VF and MPPB and are therefore not included in the WVDP facility characterization database. As noted above, (see response to question 1.a.1 ), the list of radionuclides used for the validation study was not modified from the list included in the WVDP facility characterization database.

Since the validation study was used to demonstrate the validity of the emission factors based on measured radioactivity during demolition and was not used to predict the total VF emissions (the VF exemption calculation was used for this purpose), it is only necessary that a realistic source term be included. The source term used was in concentrations of gross beta and gross alpha.

. Comment Page No, *

• Section or

• Number Paragraph No.

1.b.1

• Page 1 1.b.2

• Page 1 1.c

. Page 1 Comments.

How are the physical (gas versus particulate) and chemical forms of the constituents considered in the modeling and monitoring?

Does using gross measurements and particulate sampling methods limit the usefulness of the sampling data? For example, does the measurement of particulates only leave out significant releases of gaseous radioactive material that should be considered in the model validation?

Why is it appropriate to compare a measured weekly average concentration to a source-emissions estimate that occurs in discrete intervals during the week?

4

• ** **Respcinse* *.

The validation study was designed to validate emission factors associated with particulate emissions. To our knowledge, other than hot cutting, which is disc1,Jssed

. later, there were no gaseous emissions associated with the VF demolition. If there were gaseous chemical forms, 100% of the gas would be released and there would not be a need to do a validation study, as the emission factor would be 1 or 100%.

As stated in the response to question 1.b.1, there are no gaseous emissions. If there were gaseous chemical forms, 100% of the gas would be released. There would be no need to perform a validation study, as the emission factor would the 1 or 100%.

The validation study was designed to validate emission factors associated with particulate emissions. Gross measurements and particulate sampling are appropriate methods for validation of particulate emission factors.

AERMOD applies the meteorological conditions for each hour to the hourly emission estimates to provide an hourly concentration value for the source term, as discussed inthe background section above.

The hourly emission files were built for every day of the validation study. Therefore there is sufficient data to evaluate the modeled hourly source concentrations for each week against the m*easured weekly averages as long as the user is aware of what these data represent.

The contamination levels in the VF were low. Based on estimated emission rates from pre-demo modelling, it was determined that a weekly collection period would be required to obtain samples that provide acceptable

• detection limits Ci/ml.

Comment Number Page No, Section or Paragraph No.

1.c Page 1 (continued)

(continued)

Comments

Response

It was recognized that both daily and weekly samples would include emissions produced by multiple demolition activities. The lower detection limits from a weekly sample were selected as the basis for the study.

As previously stated, demolition activities are a mixture of discrete activities, (hydraulic hammer, mechanical shearing or waste loading) and continuous emission sources (debris piles). In practice, there are few times when only one of those activities is occurring at any one time, especially if there is a debris pile. To better account for the overlapping emission sources, hourly emission files were used. See the general background section for a description of how hourly emission files were produced and used.

2.

Validation study methodology: It is unclear to the NRC staff how the study methodology and rationale support significant changes to model parameters.

2.a Page 1 Only two discrete air sampling locations were used in the validation study (see Figure 2). Comparisons of modeled to monitored concentrations could be misleading if the comparisons are focused on a small area that does not provide complete information on the overall goodness of fit of the model to observed concentrations 2

• Although the validation study has many assumptions and limitations, significant changes were made to the model and model parameters based on the results of the study.

5 The only changes that were made to the alternative method as a result of the validation study were modification of the emissions faGtors for hydraulic hammering and hot cutting. The shearing, waste pile and loading emission files were not modified. The model itself was not modified.

'Page No, Comment Number Section or

• Paragraph No.

Comments*

2.a Page 1 (continued)

(continued) 6

':Response

• The alternative method was prepared with an assumption that the method could be approved for use without any validation. It was assumed that emissions from hydraulic hammering would be significantly greater than hydraulic shearing. Therefore, conservative factors were selected for hydraulic hammering. The results of the validation study for hydraulic hammering show that the original factors were indeed conservative and overestimated emissions._

Several reports prepared for demolition activities performed at the Hanford site indicated that a good emission factor for hydraulic hammering was around 5.0E-05 Ci released per Ci processed. Computing the source term (ST} as = (MAR)x(DR)x(ARF)x(RF)x(LPF},

-values for DR = 0.5, ARF = 0.001, RF= 1 and LPF =

0.1 were selected by Hanford for hydraulic hammering.

To be conservative, for West Valley the hydraulic hammering emission factor was initially set to 1.0E-03 Ci released per Ci processed. However, based on the results of the validation study, it was determined that a more realistic emission factor for hydraulic hammering was 1.0E-05, using values similar to those used at Hanford with DR = 0.1 (as compared to 0.5 at Hanford),

ARF = 0.001, RF= 1 and LPF = 0.1.

The recommended change to the hydraulic hammering emission factor was based on measured emissions during VF demolition. The originally proposed conservative emission factor for hydraulic hammering was developed before VF demolition assuming no validation study would be required. The change in the emissions factor for hot cutting is discussed in more -

detail under questions 5a, b and c.

Comment Number 2.a Page No, Section or

• Paragraph No.

Page 1 (continued)

(continued) 2.b.1 Page 1 2.b.2 Page i 2.c.1 Page 1 Comments*

Footnote 2 : Air concentrations could be quite disparate in two discret'3 locations but be generally consistent considering the overall distribution of activity. Air concentrations could also be very similar (e.g., close to background) in two discrete locations but otherwise be quite different considering higher concentrations in the centerline of the plume.

The Vitrification Facility arid Main Plant Process Building Decommissioning and Demolition Plans discuss the use of low volume air samplers and real time air monitors at the demolition site boundary during demolition, as well as a breathing zone air sampler in the cab of the excavator(s).

Were these.air samplers and monitors oriented in multiple compass directions surrounding the Vitrification Facility (VF)?

Was air sampling data from other sampling locations (other than ANVDEM01 and ANVDEM02) evaluated as ari additional check on the goodness of fit of the modeled air concentrations to actual measurements and to assess uncertainty in the model given limitations of the validation

• study?

Would it be worthwhile to compare worker exposures based on bioassay monitoring to the exposures based on modeling estimates?

7

Response

The location of the air samplers was negotiated with EPA during development of the Test Plan (included as Appendix E in the Validation Study Document). The locations were based on the expected plume pathways using a 5 year meteorological file. As AERMOD calculates the emissions on an hourly basis; covering all compass directions is not a requirement. Three primary criteria were used for selection of sample locations:

1) being in the primary project plume pathway,

2) being outside the MPPB building wake zones, and

3) obtaining a sample with the lowest possible detection limits.

Yes, during VF demolition, additional samplers were located at numerous locations and compass directions for personnel protection purposes. The same approach is planned for MPPB demolition.

No, only the ANVDEM01 and ANVDEM02 samplers that were established for the validation study were used in the validation study. However, separate from the validation study, off-site ambient air sampling data was evaluated (as noted in comment 5a below).

There were no positive bioassay results attributed to VF demolition.

Page No, Comment --

'Section or -----

Number : -Paragraph No.

2.d.1 Page2 Comments While the Main Plant Process Building is located to the SSE of the Vitrification Facility, Figure 4 shows that the wind is blowing roughly from the direction of air sampler ANVDEM01 towards the SSE quite frequently. Additionally, low wind conditions near building/structures could also lead to relatively high concentrations close to the source. NRC staff believe it is reasonable that air sampling stations were located to the north of the Vitrification Facility given the wind patterns shown in Figure 4; however, a discussion of modeled versus actual concentrations using additional (more complete) air sampling data around the Vitrification Facility would provide more confidence in the AERMOD modeling results and its ability to estimate "plume" distributions and assess dose during demolition activities. Plots of the differential between mod.eled plume distributions and actual data, if available for these other air sampling stations, would be very informative in assessing the predictive performance of the AERMOD air dispersion code.

As part of the development of the Test Plan, the WVDP and the EPA determined the modeling methodology to be used in the validation study. Differential concentrations at ANVDEM01 and ANVDEM02 (modeled versus predicted) were generated at ANVDEM01 and ANVDEM02. Differential plots are therefore not available for other air samplers (i.e.,

monitors and samplers for worker protection and off-site samplers) as they were not part of the EPA approved Test Plan. There are several issues with using them for validation, such as higher detection limits, and many were located in building wake zones.

3.

Selection of background concentrations:

3.a Page2 Table 4 and Figure 5 show that during the baseline period, the ANVDEM01 and ANVDEM02 demolition sampler results were consistently less than the 16 sampler results for every -

-compass location for gross alpha (and consistently higher for gross beta). How does the Department of Energy (DOE) ensure that these systematic differences do not negatively affect the model validation study? For example, the AF03 background concentrations were added to AERMOD modeled values for comparison against demolition sampler data which could make it appear that the modeled values were too high for alp~a and too low for beta.

8 The location of the background sampler (AF03) was negotiated with EPA. Figure 5 presents the measured gross alpha values with the background sampler error banq showing the uncertainty in the measurement.

Some of the sample results for the ANVDEMO samplers are above and some are below the background sampler. The ANVDEM01 and ANVDEM02 measured values are within the error bands of the AF03 sampler in 19 of the 24 samples.

For those instances where the ANVDEMO sampler results are within the error bands, the results are statistically the same.

Comment Number Page No, Section or Paragraph No.

Comments

4.

Uncertainty in air concentrations from hydraulic hammering:

4.a Page2 4.b Page 2.

4.c Page 2 Air concentrations at two sampling locations in the validation study were significantly overestimated by°AERMOD in weeks that hydraulic hammering demolition activities occurred. The fact that the modeled versus actual concentrations were similar for some types of activities3 and orders of magnitude differ!=)nt for other activities (e.g., hydraulic hammering),

suggests there is significant uncertainty in the modeling/validation. Based on the results of this validation study, DOE contractors recommended a two order of magnitude reduction in the Air Release Fraction (ARF) for hydrgi.ulic hammering, which would lead to a similar reduction in the source term and dose. To help justify the reduction in source term for hydraulic hammering using the ARF, DOE should comment on the basis for the hydraulic hammering ARF values in DOE-HDBK-3010-94 (DOE, 1994) and explain the differences between the West Valley demolition project data and other studies upon which the ARF values are based.

Footnote 3

For shearing, the modeled and measured values were close to background and any added radioactivity f ram shearing activities appeared to be within the "noise": Thus, the modeled and measured concentrations were similar, but it is unclear if the sampling data are useful for validating the AERMOD modeling results.

Are there any plans to update the DOE handbook and other documents supporting modeled parameters based upon the West Valley study?

What other factors may have played into the large differences between modeled and actual results (e.g.; model/parameter uncertainties including inventory, lack of consideration of

9.

Response

All of the ARF values selected were within the range of factors given in DOE-HDBK-3010-94. In an effort to not underestimate the impacts of the demolition activities, conservative factors were selected.

The DOE handbook does not contain factors that are specific to hydraulic hammering. As discussed in the Alternative Method document, the ARFs are from falling object impact testing on horizontal surfaces. Prior to having data from hydraulic hammering, a bounding value of ARF of 1 E-2, as suggested in the DOE handbook was selected. While the median value in the handbook for all test results is 4E-04, a value of 1 E-03 was selected in the modified alternative method emission factor development.

Emissions for shearing were low, which was predicted by the AERMOD modeling runs. In fact, the validation study shows that emissions for both demolition methods (hammering and shearing) are negligible compared to pile emissions. There were nine weeks when shearing occurred. Of those nine weeks, five had emissions that were deemed statistically significant.

What can be said is that during those nine weeks the modelled emissions did not underestimate the actual emissions.

There are no plans at this time to update the DOE handbook. This would be a DOE-HQ decision, not a WVDP decision.

The primary difference was due to the selection of conservative emission factors during preparation of the Alternative Method.

• Comment

.Page:No, Bection or*.

Number**.. Paragraph No.

• 4.. c Page2 (continued}

(continued}

Comments deposition, debris pile source term contributions, treatment of low wind conditions, building/structure wake effects)?

Footnote 4

Deposition could lead to higher concentrations closer to the source.

5.

Uncertainty in air concentrations from "hot cutting":

5.a Page3 Air concentrations for beta emitters at both (on-site) sampling locations in the validation study were underestimated by AERMOD for "hot cutting" activities. While DOE attempted to adjust modeling parameters (i.e., physical state factor) to.

better align the modeled and actual air concentrations, limited data is available to ensure that modeling is reasonably conservative for "hot cutting" activities.

Given the limited data set (two weeks of data at each of the two on-site samplers) and uncertainty associated with the measurements (e.g., only gross measurements of particulate activity on filters collected weekly at two discrete sampling locations is measured), it is unclear that sufficient information is available to adjust model parameters to ensure decommissioning and demolition constraints will be sufficiently protective. Most.of the underestimate of gross beta is thought to be associated with relatively high volatility radionuclide$ such as Cs-137.

Was any thought given to comparing Cs-137 ( or other radionuclide) concentrations to model results (although the sampling strategy may not be conducive to validating air concentration results for volatile radionuclides in gaseous form)?

10 J

.~*

.As previously discussed, these conservative values were selected based on the fact that very little data was available for hydraulic hammering emissions and the thought that the method might be approved without the need for a validation study.

Although comparison of isotopic results was not part of the Test Plan (which as noted, involved modeled and measured gross alpha and gross beta results at the on-site demolition samplers only), an evaluation of Cs-137 emissions was performed outside the study. Since the model comparisons to measured concentrations at the off ssite samplers were not part of the validation study, these comparisons were not included in the validation study report.

Cs-137 was the isotope selected for evaluation (outside the study) because Cs-137 was the only radionuclide detected at an off-site sampler during the VF demolition process and it was only detected during the hot cutting operations. Cs-137 was detected on the filters collected at off-site sampling locations AF15 and AF16 during hot cutting.

The Cs-137 concentration on the AF16 high volume sample collected on 7/31/18 was 9.44E-15 µCi/ml. The predicted Cs-137 concentration at the AF16 location from the hot cutting emissions performed during the sample period using AERMOD and the revised alternative method emission factors to:r hot cutting was 6.14E-15 µCi/ml.

Comment Number 5.a Page No, Section or Paragraph Nb.

Page 3 (continued)

(continued) 5.b Page 3 5.c Page 3 Comments Are other parameters besides the physical state factor available to adjust the modeling (e.g., Appendix Fnotes that 1 percent of the inventory is assumed to be vaporized)?

What other information (e.g., from other sites and projects) is available to select parameters and simulate radionuclide release from these types of "hot cutting" activities?

11 Response.

Similarly, the Cs-137 concentration on the AF16 high volume sample collected on 8/14/18 was 7.01 E-16

µCi/ml. The predicted value using AERMOD and the revised alternative method was 7.08E-16 µCi/ml.

For the hot-cutting emission factor, the adjustment of physical state factors in the alternative method was made to address the fact that it appears that the original factors underestimated emission of beta emitters. The change will increase predicted emissions of beta emitters. There were no changes made for alpha emitters. These factors will be used for any hot cutting planned for the MPPB demolition.

Duririg development of the alternative method, other methods were.discussed with EPA. The problem with the. other methods is that the chemical compounds being cut or heated must be known. Therefore, the physical state factor was the parameter EPA agreed to adjust.

To our knowledge, no other data is available from other sites or projects that estimate air emissions from hot cutting.

• Other sites have been successful at estimating emission rates using the vapor pressure of a chemical compound being heated. However, these methods have not been extended to metal cutting where the metal is vaporized. The vapor pressure method used for heating material is also limited to applications where physical ventilation systems including ducts, filters and exhaust.fans are included in the source. These physical pieces of equipment would allow the material to cool and be collected on filters.

6.

Assessment of statistically significant demolition sampling data:

6.a Page3 Please clarify how the probability density functions (pdfs) for each sampling week during demotion were constructed. For example, how many measurements were used to determine the population variability component of variance when constructing the demolition sampling pdfs found in Appendix D?

7.

Rubble Pile vs. Load Out Emissions:

7.a Page 3 How does DOE differentiate between debris pile and load out.

emissions and other demolition activities occurring at the.

same time or does DOE assume all emissions come from just

. one activity?

12 The population variability for a sample is calculated as the difference between the individual sample variability and the average variability for all samples collected during demolition.

The statistical test was something that was promised in

• the Test Plan. It provides a method to evaluate if a sample is different from the baseline population. It was not used to determine emission factors.

Emis$ions were calculated on an hourly.basis. As discussed above in 1.c and the general background section, it was recognized that demolition activities are a mixture of discrete activities, (hydraulic hammer, mechanical shearing or waste loading) and continuous emission sources (debris piles). In practice, there are few times when only one of those activities is occurring at any one time, especially if there is a debris pile. To better account for the overlapping emission sources, hourly emission files were used.

In this demolition effort, piles were a unique activity where there were multiple weeks when there were no other demolition activities being performed. During those weeks, piles were the only demolition related emission source. During other periods, emissions were totaled from a combir,ation of sources.

_Page No, Comment Section or Number Paragraph No.

7.b Page 3 7.c Page 3.

Comments Could DOE comment on the relative risk of various demolition activities?

In the case of hydraulic hammering, DOE notes the weeks when only debris pile emissions contributed to the measured concentrations (see Table 24) and independently modified the moisture content parameter to better match data during those weeks. However, hydraulic hammering did not occur in isolation and adjustments to hydraulic hammering ARFs to match air concentration data were confounded by the contributions from multiple sources.

13

Response

The risk from the hydraulic hammering and mechanical shearing appears to be low. Both of these methods are used for short periods of time and are well controlled by misting at the point of demolition.

Loading of debris is also a low risk operation with relatively low air emissions. Again, the activity occurs over a short time period with application of water and/or fixative to mitigate emissions. However, in general, it was found that debris pile emissions dominated the risk from the airborne pathway. This was also observed at the Plutonium Finishing Plant at the Hanford site.

Hot cutting of highly contaminated materials can also be a major source of airborne emissions, especially when the contamination is a compound with a high vapor pressure (low boiling point: as the vapor pressure at the boiling point equals 1 atmosphere).

The relative risk is factored into the demolition plans and may also include risks due to building collapse, personnel exposure due to time in the work area, and other hazards such as waste load out issues (i.e.,

container sizes and acceptable locations to dispose of the waste materials).

As previously discussed, it was known that the emissions would include multiple sources when the study began. To help account for this, emissions were calculated on an hourly basis. The AERMOD model calculates emissions hourly. See the discussion in the background section at the beginning of this document.

Page No, Comment. Section or Number *. Paragraph No.

8.

Estimated Doses:

8.a Page 3 8.b Page3 8.c Page 3

. Comments.

While DOE provided preliminary estimates of dose based on modeling, could DOE provide final estimated worker and member of the public doses from the Vitrification Facility demolition based on measured values?

Could DOE comment on the types of activities and radionuclides that are expected to lead to the highest doses?

Could DOE provide information on the expected relative risk from demolition of the Vitrification Facility versus the Main Plant Process Building demolition?

14

• • Response The estimated total worker dose during VF demolition (September 2017 to September 2018) was 3.087 rem.

The 2017 estimated dose to the public was

<0.46 mrem. The 2018 estimated dose to the public was <0.55 mrem, and included the contribution from Cs-137 (see response to comment 5.a) as well as non-detectable results from the other isotopes measured at the WVDP's off-site ambient air network.

The annual dose to the public is published in th.e WVDP Annual Site Environmental Report (ASER).

Copies of the report are available at htt s://www.wv.doe. ov/ASER_lndex.html For external doses (dose from sources outside the body) the primary contributor will be from Cs-137 in.

cells.CPC, PMC and the XC-1 to XC-3 cells.

For potential internal exposure (exposures due primarily to inhalation from airborne materials) the main contributors would be from Am-241 and Pu-239. The

• highest concentrations will be in the areas of PPG North and South.

The higher areas of concern in the MPPB will be approximately 10 times higher than the VIT Cell.

Based on actual data, 3.8 DAG-hr was measured at the 90 meter VF demolition boundary. This was a result of measured levels of contamination on VIT walls and surfaces. For the MPPB demolition, a maximum of 40 DAG-hr (100 mrem).is allowed at the boundary, meaning allowed contamination levels may be approximately 10-times (40/3.8) higher than VF levels.

Therefore, the maximum expected relative risk during MPPB demolition may be up to 10 times higher than it was for VF demolition.

Comment Number

1.

Page No, Section or Paragraph No.

Page 4 Comments What lessons learned did DOE incorporate into its demolition plans and procedures, if any, based on the Hanford Plutonium (Pu) finishing plant contamination event? The Hanford Pu contamination event pointed to the need for a good understanding of demolition practices reflected in the modeling and clear documentation of assumptions used in the modeling, as well as consideration of lower likelihood events and pathways. For example, for the Hanford demolition project, uniform demolition rates were assumed in the modeling although actual demolition rates were variable with higher rates of demolition occurring near the end of the project. The Hanford demolition project modeling may have assumed that the demolished building rubble was packaged and disposed in a timely manner while the rubble may have

. remained on the ground for a few days representing a*

significant source term. Low frequency meteorological events may lead to under-or over-estimates in public and worker doses (e.g., high winds leading to greater dispersion of particles.)

It appears that building demolition plans and procedures at West Valley considered building rubble emissions, had constraints on rates of demolition, and considered uncertainty in meteorological conditions through use of 95th percentile concentrations from modeling simulations. Were any changes made to project plans and procedures following the Hanford event to ensure that the modeling is consistent with actual practices and considers potential conditions at the time of the demolition to ensure workers and members of the public are protected?

15

Response

The validation study did not include within its scope lessons learned from the Hanford Demolition or from any other demolition action. The validation study was.

limited to comparison of modelled emissions to measured emissions during the demolition of the VF.

Demolition work plans for the MPPB will include lessons learned, including from VF demolition and from PFP at Hanford.

For example:

1) Demolition times used in modeling will be included in the work packages when the time is a critical factor.

2) Debris piles will be controlled by limiting the time the pile remains and the size of the pile.

3) Wind speed limitations were included in the VF demolition work plans and are included in the MPPB demolition work plans.

4) The air emissions model is still being developed.

Worst case scenarios, as well as 95% meteorology is being considered.

5) Air emission estimates will be based on the emission factors presented in the final VF validation study as approved by EPA.

Comment Number Page No, Section or Paragraph No.

Model Uncertainty:

2.

Page 4 Ambient/Offsite Sampling:

3.

Page4 Comments,,

How is uncertainty in modeling parameters, including the material at risk, considered in the modeling to ensure that projected doses are acceptable? For example, the 95th percentile concentration from modeling was calculated based on 5 years of meteorological data to ensure that concentration remained below 0.02 times the Derived Air Concentration (DAG). What other modeling uncertainties (e.g., inventory, deposition, treatment of low wind conditions and building wake effects) were considered or how was uncertainty otherwise managed?

What were the results of and what analyses did DOE perform with respect to off-site air sampling to evaluate whether air concentrations were indistinguishable from background?

Confirm that validation to CAP-88 calculations will not be performed and the reasons for the lack of validation of off-site air concentrations (e.g., due to negligible impacts *at offsite locations).

Hespons~..

The uncertainty in modeling parameters is minimized by using the best available data as input to the MPPB air emissions model which is still being developed.

Factors such as wind speed and building wake effects are part of the AERMOD model and are incorporated.

The model being developed is based on the demolition sequence. The model will be executed for each planned sequence. There are currently 120 sequences in the demolition and each sequence will.be modelled as a discrete event.

The MAR in each sequence is based on the WVDP characterization database. There are currently over 2,200 structures in the MPPB MAR file. Contamination

• levels for each structure is an average of multiple (generally 5) samples, followed by a surface scan to ensure that the data is representative of the entire structure.

The site operates 16 low volume and 1 high volume samplers that ring the site, and also a background location that are sampled biweekly and analyzed quarterly for radioisotopes Sr-90, 1-129, Cs-137,

• U-232, Pu-238, Pu-239/240, and Am-241. The biweekly samples are also analyzed for gross alpha and gross beta. During demolition, the only filters collected that had detectable radioactivity above background were sampling the air during hot cutting.

The annual average concentrations at AF15 and AF16 samplers in 2018 had detectable Cs-137 values. As discussed above in comment 5a, the predicted values

Comment Number Page No, Section or Paragraph No.

3.

Page 4 (continued)

(continued)

1.

Page4

2.

Page4 Comments

Response

compared well with the measured values when the adjusted emission factors for hot cutting were used.

The site uses actual measured results from the ambient sampling ring to calculate dose and not CAP88. The dose calculation method using ambient samplers is an EPA approved method for the WVDP.

A detailed presentation of off-site air sampler results is published in the WVDP Annual Site Environmental Report (ASER). Copies of the report are available at https://www.wv.doe.gov/ASER_lndex.html

==========-===,_.,_,,_

-,--.,,,.,_-=-,---I Clarification:

What is meant by "boiling point of radionuclides?" Is this the boiling point of the chemical form of radiological contamination?

Apparent cut and paste error:

Table 13 has the same values for modeled and predicted concentrations.

• 17 Yes, it would be the chemical compound, such as CsCI or CsOH.

Agreed.

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