National Institute for Occupational Safety and Health

Discussion of Metals and Controls 

Petitioner Comments

Brant Ulsh, Ph.D., CHP

NIOSH, Research Health Physicist

Advisory Board on Radiation and Worker Health

Metals and Controls Work Group Meeting

July 13, 2023
Overview

 Introduction

 Comparability of drain cleaning: D&D vs M&C maintenance 

workers

 Subsurface outside – use of blended D&D characterization 

survey data

– Inside data

– Outside blended survey data

– Use of Mound dust loading data

 Conclusions

7/13/2023 2
Introduction 
Introduction – Petitioner Comments

 The petitioner for SEC 236 submitted written comments dated 

2023-05-27

 This presentation provides NIOSH responses to these 

comments

 The petitioner’s comments concerned two main points:

– Comparability of drain cleaning: D&D vs M&C maintenance 

workers, and

– Subsurface outside – use of blended D&D characterization 

survey data

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Introduction – NIOSH bounding methods (1 of 2)

 NIOSH’s method to bound internal doses from subsurface 

contamination during the residual period:

– Indoor source term estimated from 1996 sediment survey 

(targeted to areas of likely contamination)

• Includes soil data around a fuel rod in a drain line

• Intakes based on 95th percentile sediment concentration 

6887 pCi/g (~1% of the specific activity of natural uranium)

7/13/2023 5
Introduction - NIOSH bounding methods (2 of 2)

 NIOSH’s method to bound internal doses from subsurface 

contamination during the residual period:

– Outdoor source term based on surveys targeted to areas of 

likely contamination

– Intakes also based on 95th percentile Mound dust loading

– NIOSH assumes all subsurface soil and piping are at 95th

percentile concentration, even though >80% of operational 

source term (Naval Reactors, High Flux Isotope Reactor), and 

none of the source term added during residual period (HFIR) 

was covered

7/13/2023 6
Comparability of Drain Cleaning: D&D vs M&C 

Maintenance Workers
Training and Monitoring

 “...the health physics awareness training and monitoring 

provided for the D&D workers did not exist for the AWE 

Residual Period maintenance workers...”

 NIOSH is not basing our internal dose bounding method on an 

assumption that training and monitoring was the same for 

maintenance and D&D workers

– Our bounding method is based on a source term 

calculation that bounds both Maintenance and D&D 

workers. It is not affected by worker training assumptions

7/13/2023 8
Different Methods / Different Tasks

 “...the methods and means of performing the tasks 

were completely different ...”

 NIOSH is not basing our internal dose bounding 

method on an assumption that tasks were the same 

for maintenance and D&D workers

– Our bounding method is consistent with intrusive 

activities performed by both Maintenance and 

D&D workers

7/13/2023 9
Contact with Source Term

 “...tasks were completely different and placed the Residual 

Period maintenance workers in much more intimate contact with 

the residual contamination...”

 NIOSH is not basing our internal dose bounding method on an 

assumption that exposure potential was the same for 

maintenance and D&D workers

– Our bounding method assumes intimate contact with the 

source term for Maintenance workers

– We are not assuming use of PPE, respiratory protection, or 

engineering controls

7/13/2023 10
Risk of Exposure

 “...tasks were completely different and placed the 

Residual Period maintenance workers...at higher risk 

of elevated exposure to residual radiation...”

 NIOSH is not basing our internal dose bounding 

method on an assumption that exposure potential 

was the same for maintenance and D&D workers

– Our models reflect the work Maintenance workers 

performed, e.g. welding/grinding work, HVAC filter 

changes

7/13/2023 11
Maintenance Worker Internal Exposure > D&D

 NIOSH has air monitoring and bioassay data from the 

D&D activities at M&C

 NIOSH’s bounding internal dose method results in 

internal doses that are larger than the D&D 

monitoring data suggest. Therefore, the maintenance 

workers are assigned higher doses than the D&D 

workers, as the petitioner asserts they should be

7/13/2023 12
Subsurface Outside – Use of Blended D&D 

Characterization Survey Data
Inside vs. Outside

 Petitioner quoted SC&A Finding 1 (8/22/22): “The back 

application of a high 1995 sediment survey result to bound 

inside subsurface activities is not adequately supported by 

information for M&C worker activities from the earlier residual 

time period” (emphasis added)

 There was no data blending for the inside subsurface model. 

The inside data is separate from the outside data

 Regarding inside data...

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Bounding Scenario

 The presence of the fuel pin in the pipe indicates that we have 

captured the worst case scenario with the 95th percentile

– We are unaware of a plausible scenario that would result in a 

higher source term estimate

 The survey data targeted contaminated areas. It is not a random 

data set. Therefore we are even more confident that the 95th

percentile is favorable

 We assume all the subsurface soil and piping are at 95th percentile 

concentration, even though >80% of original source term and none 

of the source term added during residual period was covered

7/13/2023 15
Precedent for Back Application of Data

 We propose to use survey data from 1996 throughout the 

residual period (1968-1997). Similar to:

– Chapman Valve (soil data from 1987, and 1992 applied 

back to 1949)

• Diverse, intrusive work, similar to the situation at M&C

– Linde (data from 2001 applied to 1970-2006)

• Subsurface maintenance utility work, confined spaces

– Vitro (air data from 1977 applied to 1965 – 1985)

7/13/2023 16
Hot Spots (1 of 2)

Petitioner quoted SC&A Observation 1 (8/22/22): “The 

use of blended D&D characterization survey data from 

1984 and 1992 to support a bounding dose from 

outside subsurface activities may not be necessarily 

bounding for work in nonuniform soil contamination, 

given the presence of hot spots that existed during the 



residual period at M&C” (emphasis added)

7/13/2023 17
Hot Spots (2 of 2)

 We are modeling representative exposures and hot 

spots are included in the data set.

 Basing modeling only on hot spots would result in 

implausibly high doses

 We use the 95th percentile (data includes hot spots), a 

claimant-favorable method consistent with 

precedents from numerous other similar sites

7/13/2023 18
Application of Mound Dust Loading (1 of 2)

 Petitioner quoted SC&A Finding 2 (8/22/22): “The application 

of surrogate data from the Mound project to provide a dustloading factor for M&C subsurface activities does not satisfy 

the Board’s surrogate data policy”

7/13/2023 19
Application of Mound Dust Loading (2 of 2)

 SC&A conducted an independent evaluation and came up 

with a similar dust loading estimate. SC&A previously agreed 

that Mound data could be applied to M&C

 NIOSH agreed with SC&A that Mound dust loading data 

would not necessarily apply at every site

 The application of outdoor dust loading data to inside 

environments (including confined spaces) is a TBD issue, not 

an SEC issue

7/13/2023 20
Conservatism of 95th Percentile Soil Contamination (1 of 2)

 Petitioner quoted SC&A Observation 2 (8/22/22): References 

to the M&C safety and health manual, NRC inspection results, 

operator training, and other programmatic considerations do 

not necessarily substantiate the conservatism of the 95th 

percentile soil contamination value being applied.”

7/13/2023 21
Conservatism of 95th Percentile Soil Contamination (2 of 2)

 NIOSH is not substantiating the 95th percentile soil 

contamination value by relying on those documents. The 

conservatism of the 95th percentile soil contamination value is 

based on sampling data targeted to contaminated areas

 The conservatism of the 95th percentile intake value does not 

take credit for work practices, PPE, training, or the robustness 

of the radiation protection program

7/13/2023 22
Conclusion
Conclusions (1 of 3)

 NIOSH modeled intake is a function of:

– Source term

– Resuspension factor/dust loading

– Occupancy/time

 NIOSH modeled intake is NOT impacted by: 

– Training/knowledge of hazards (assumes none)

– PPE (assumes none)

– Monitoring (assumes none)

7/13/2023 24
Conclusions (2 of 3)

 NIOSH’s method to bound internal doses from subsurface 

contamination during the residual period:

– NIOSH assumes all of the subsurface soil and piping are at 95th

percentile concentration, even though >80% of original source 

term (Naval Reactors, HFIR), and none of the source term 

added during residual period was covered (HFIR)

– NIOSH assumes all workers are occupationally exposed or in 

close contact with the 95th percentile concentration.

– The petitioner’s comments do not affect NIOSH’s internal 

dose bounding estimate

7/13/2023 25
Conclusions (3 of 3)

 Data have been back extrapolated to cover residual periods at 

other sites with Board concurrence, as we propose to do at M&C

 No plausible bounding scenario higher than the fuel pin in the 

pipe has been identified or proposed by the Working Group

 NIOSH’s bounding internal dose estimate makes multiple 

favorable assumptions. It is not plausible that workers’ exposures 

were higher than these assumptions suggest

– NIOSH’s bounding estimate is sufficiently accurate – it is based 

on source term data from M&C

7/13/2023 26
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.