Review of NIOSH 

Response to SC&A 

Comments on 

ORAUT-RPRT-0090

Joe Fitzgerald, MS, MPH

Bob Barton, CHP

Ron Buchanan, PhD, CHP

To the Advisory Board on Radiation and 

Worker Health ORNL (X-10) Work Group

June 30, 2021
Introduction

◆ 1955 to 1988: 213 “exotic radionuclides” were 

produced by the Isotopes Division and its 

predecessors at ORNL.

◆ March 2018: NIOSH issued ORAUT-RPRT-0090, 

rev. 00, “Monitoring Feasibility Evaluation for 

Exotic Radionuclides Produced by the Oak Ridge 

National Laboratory Isotopes Division.”

2
Summary of RPRT-0090

◆ States that ORNL had adequate monitoring 

capabilities for 179 of the 213 radionuclides.

◆ RPRT-0090, table 7-4, summarized the 34 

remaining radionuclides that needed 

additional evaluation:

– 28 different radionuclides

– 5 iodine radionuclides

– 1 plutonium radionuclide (only at Y-12, not ORNL)

3
Evaluation of RPRT-0090

◆ October 2018: SC&A’s review of RPRT-0090 

identified seven findings and six observations.

◆ June 2020: NIOSH responded to SC&A’s 

evaluation report in a response paper.

4
Finding 1

The scope of RPRT-0090 needs to be clearly 

defined

5
Finding 1: SC&A summary of NIOSH 

response

◆ The scope of RPRT-0090 was purposely limited 

to the production of radioisotopes by the Isotopes 

Division on both the ORNL and Y-12 footprints. 

◆ RPRT-0090 was not intended to be an evaluation 

of whether a co-exposure model type approach 

could be developed for every single radionuclide.

6
Finding 1: SC&A response

◆ SC&A accepts NIOSH’s clarification regarding 

the limited scope of RPRT-0090, which would 

exclude treatment of decontamination and 

decommissioning (D&D), construction, and 

maintenance activities that may encompass the 

facilities in question.

◆ SC&A recommends closure.

7
Finding 2

Incomplete radionuclide and radioisotope facility 

inventory

8
Finding 2: SC&A summary of NIOSH 

response

◆ The discrepancies indicated by SC&A are 

generally related to the scope of the document: 

the isotopes produced by the isotopes group 

versus a more general analysis of the overall 

radionuclide inventory at ORNL. 

◆ The inventory listing was developed 

independently of the facility list and was related 

to isotope group activities across the site. 

9
Finding 2: SC&A response

◆ SC&A accepts the clarifications provided by 

NIOSH in table 1 of its response and notes that 

an explanation will be added to the next revision 

of RPRT-0090 regarding the scope of the 

radionuclide inventory included. 

◆ SC&A recommends closure.

10
Finding 3

Attachment A in vitro bioassay methods lack 

information about actual implementation

11
Finding 3: SC&A summary of NIOSH 

response

◆ NIOSH intends RPRT-0090 to be a review of the 

isotopes handled by the isotopes production group in 

comparison to the available bioassay capability. 

◆ Although not all available data on sporadically 

produced radionuclides will be of sufficient quantity to 

allow for their use in a co-exposure model, this alone 

is not indicative that a potential exposure could not 

be bound with sufficient accuracy.

12
Finding 3: SC&A response

◆ Review of dosimetry capability, while necessary to 

validate that measurement techniques were 

technically acceptable and available, is not sufficient 

to address the feasibility of dose reconstruction. 

◆ Identifying the number of samples devoid of 

exposure potential considerations over 30+ years of 

Isotope Division production arguably would not 

satisfy DCAS-IG-006.

13
Finding 3: SC&A recommendation

◆ At the very least, RPRT-0090 needs a weight-ofevidence approach to validate that monitoring 

took place (or was not necessary) for operational 

time periods that lacked recorded sampling or 

where sampling was sparse (e.g., 1 or 2 

samples). 

◆ SC&A recommends that this finding remain open.

14
Finding 4

Feasibility of monitoring 28 radionuclides not 

adequately addressed

15
Finding 4: RPRT-0090 evaluation of 

28 radionuclides

◆ The “red”-shaded blocks in tables 7-2 and 7-3 

mean:

A specific radionuclide was present in inventory in the 

specified year, but an additional analysis was 

necessary to determine if the nuclide represented an 

infeasibility from a monitoring perspective.

◆ Table 7-6 uses derived air concentration 

(table 7-5) to illustrate the maximum organ dose 

for a hypothetical intake.

16
Finding 4: SC&A summary of NIOSH 

response to bioassay data

◆ The implementation of the monitoring program is 

indicated by the availability of the bioassay cards 

showing results for the respective methods. 

◆ Any available bioassay data could be used to 

assign doses to a claimant. 

◆ Additional review of available records and 

monitoring procedures will be ongoing using the 

data available in the SRDB.

17
Finding 4: SC&A summary of NIOSH 

response to gaps

◆ NIOSH’s 2020 response paper presents some 

supplemental information to address some of the 

gaps in the data in table 7-6 of RRPT-0090.

18
Finding 4: SC&A response

◆ Although the resulting organ doses in table 7-6 

from a hypothetical intake are not alarming, they 

do not appear insignificant for a potential 

unmonitored exposure.

◆ The derived doses do not directly address the 

monitoring feasibility question.

◆ The additional data in NIOSH’s response do not 

address the monitoring feasibility question.

19
Finding 4: SC&A conclusion

◆ SC&A finds that the question of “if the nuclide 

represented an infeasibility from a monitoring 

perspective” remains relevant and that it was not 

specifically and completely addressed in 

sections 7.2 or 8.0 of RPRT-0090, or NIOSH’s 

2020 response. 

◆ SC&A recommends that this finding remain open.

20
Finding 5

1955 and 1956 intakes may not be bound by earlier 

coworker data

21
Finding 5: SC&A summary of NIOSH 

response

◆ 1956 releases (66,700 Ci) compared to 1947 

releases (64,200 Ci) are within the measurement 

uncertainty in the data (i.e., estimates in releases 

differ by less than 4%).

◆ NIOSH responded to various SC&A concerns for 

finding 5 by clarifying the three primary justifications 

for co-exposure estimates:

– Bioassay comparison

– In vivo comparison

– Air concentration guideline comparison

22
Finding 5: Original concerns re 

bioassay comparison

◆ Original SC&A concern: 

– Urinalysis samples primarily after period of interest

– Unclear when highest samples were taken or under 

what circumstances

◆ NIOSH response:

– Co-exposure estimates are done using thyroid 

monitoring, bioassay included for comparison

– Dates and circumstances provided for highest 

measurements

23
Finding 5: SC&A position re 

bioassay comparison

◆ SC&A position:

– Notes that comparison of data from one period to 

another requires the establishment of similar working 

conditions/exposure potential

– Agrees there is no indication to date that conditions 

would result in theoretical bioassay an order of 

magnitude higher than those measured in later periods

24
Finding 5: Concerns re in vivo 

comparison

◆ Original SC&A concern:

– In vivo comparison was a measurement taken at the end of the 

period of interest (1962)

– Is it appropriate to back extrapolate that result for comparison?

◆ NIOSH response: Co-exposure estimates are done using 

thyroid monitoring; in vivo result provided for comparison 

to demonstrate a bounding co-exposure approach

◆ SC&A position: 

– Concurs in the context of comparison purposes

– Notes (in general) caution must be used when back extrapolating 

data from one period to another even for comparison

25
Finding 5: Original concerns re air 

concentration limit comparison

◆ Original SC&A concern:

– Air concentration data only in summary form (individual 

measurements and locations are unknown)

– Are there specific locations where air concentrations may have 

exceeded the operating level and how often?

– Site profile indicates maximum operating level was ~50% higher 

than projected air concentration from co-exposure estimate

◆ NIOSH response: 

– Air concentration comparison is to the allowable operating levels, 

not the actual measurements

– Site profile contains an error in maximum allowable air 

concentration levels and will be corrected

26
Finding 5: SC&A position re air 

concentration limit comparison

◆ Maintains it is important to obtain and evaluate the 

actual air concentration measurements to determine 

if limits were exceeded (and if so, when and where)

◆ Believes the original site profile may not be in error

◆ Original historical records of maximum allowable air 

concentrations are unclear and require further 

discussion

27
Finding 5: Maximum allowable air 

concentrations

Source: Sadowski, G. S. (1953, March 9). Control of radiation exposure in the ORNL 

pilot plant (ORNL 53-3-47). SRDB Ref. ID 103344

28
Finding 5: SC&A summary position

◆ SC&A agrees that differences in stack emissions from 

RaLa production were small when comparing the highest 

years (1947 and 1956).

◆ SC&A believes uncertainty still exists and that care must 

be exercised to assure extrapolation of co-exposure 

estimates are bounding.

– Past precedent in EEOICPA suggests that when uncertainty 

exists, modification factors are used to assure bounding exposure 

estimates.

– Example: Somewhat arbitrary factor of 10 applied in section 7.2 of 

RPRT-0090 to “ensure a conservative evaluation.”

29
Finding 6

Adequacy and implementation of in vivo bioassay 

program not addressed 

30
Finding 6: SC&A summary of NIOSH 

response

◆ NIOSH believes that the volume of available 

monitoring data, including analysis for nonroutine 

radionuclides, as shown in RPRT-0090, table 4.3 

(Bioassay code 000 with monitored nuclide, 

1955–1988), demonstrates the capability to 

monitor exposure to the wide range of materials 

present. However, NIOSH did not intend to 

include a review of program implementation in 

RPRT-0090.

31
Finding 6: SC&A response

◆ SC&A considers this finding subsumed under 

finding 3 and recommends closure of this issue.

32
Finding 7

Unclear treatment of post-1988 monitoring 

capability during abandonment, deactivation, and 

decontamination and decommissioning phases

33
Finding 7: SC&A summary of NIOSH 

response

◆ The point of RPRT-0090 was to assess the 

feasibility of monitoring nuclides produced by the 

isotopes group during production operations. 

◆ While such analysis is outside the scope of the 

document, it would seem credible that it would be 

feasible to bound exposures to the same set of 

radionuclides during D&D periods after 1988 with 

modern dosimetry methods.

34
Finding 7: SC&A response

◆ SC&A accepts this clarification, as noted in the 

response to finding 1. 

◆ SC&A recommends closure of this finding.

35
Observation 1

Inventory discrepancy

36
Observation 1: SC&A summary of 

NIOSH response

◆ Inventory of radionuclides processed by the 

isotopes group was developed through a review 

of published sales records. 

◆ The spreadsheet that SC&A refers to represents 

the compilation of that document review. 

◆ NIOSH updated the radionuclide inventory based 

on a review of logbooks. This review resulted in 

the addition of radionuclides and years.

37
Observation 1: SC&A response

◆ Discrepancies that SC&A identified were 

additional radionuclides or years appearing in 

table 7-2.

◆ SC&A concurs that additional radionuclides or 

years from logbooks added to the X-10 inventory 

spreadsheet would explain the discrepancies in 

inventory between table 7-2 in RPRT-0090 and 

NIOSH’s X-10 inventory spreadsheet. 

38
Observation 1: SC&A conclusion

◆ SC&A finds this observation clarified and 

recommends closure.

39
Observation 2

Specific alpha-emitting radionuclide needs to be 

identified for dose reconstruction (DR)

40
Observation 2: SC&A summary of 

NIOSH response

◆ The original X-10 bioassay cards are provided by 

ORNL for individual claimants and are the basis 

for DR. 

◆ The X-10 database is not used for dose 

reconstruction purposes.

41
Observation 2: SC&A response

◆ Considering NIOSH’s clarification that the X-10 

database will not be used for individual DR, 

SC&A concurs with NIOSH’s response. 

◆ If the X-10 database will not be used in coworker 

intake modeling without further consideration of 

specific alpha-emitting radionuclides, then SC&A 

finds this observation has been clarified and 

recommends closure.

42
Observation 3

Trans-plutonium radionuclides may need further 

analyses

43
Observation 3: SC&A summary of 

NIOSH response

◆ ORAUT-TKBS-0012-5 identifies americium-241 

(Am-241) as the default assumption for transplutonium (TPO) bioassay results. 

◆ Of the 20 radionuclides detectable by the TPO 

method, only two have a higher organ dose 

conversion factor (DCF) (curium-248 and 

californium-249) than Am-241.

◆ Am-241 inventory is much greater than the inventory 

for either of these two radionuclides.

44
Observation 3: SC&A response

◆ Considering the DCFs and inventory amounts of 

TPOs, SC&A finds that using Am-241 as the 

default radionuclide (if other information is not 

available) would be a reasonable assumption. 

◆ SC&A finds this observation clarified and 

recommends closure.

45
Observation 4

Use of gross beta or gamma count data could 

result in underestimate of assigned dose

46
Observation 4: SC&A summary of 

NIOSH response to the Ru-106 issue

◆ The “green” shading for ruthenium-106 (Ru-106) 

in table 7-3 (p. 34) is indicating the presence of 

bioassay data, but no results for these methods 

were present in 1975, 1978, and 1986–1988.

◆ This was an editing error. In the revised RPRT0090, table 7-3 will shade “yellow” the indicated 

years for Ru-106.

47
Observation 4: SC&A response to 

the Ru-106 issue

◆ SC&A concurs with NIOSH’s response to the

ruthenium-106 issue and agrees that the issue

can be resolved by NIOSH making changes in

the next revision of RPRT-0090.

48
Observation 4: SC&A summary of 

NIOSH reply to beta/gamma data

◆ X-10 bioassay cards are provided for claimants 

and are the basis for DR. 

◆ Claimant’s records for specific radionuclides that 

were monitored are available for use in claimantspecific DR. 

◆ Specific adjustments based on individual 

radionuclides would be outside the scope of 

RPRT-0090.

49
Observation 4: SC&A response to 

the beta/gamma data issue

◆ NIOSH does not appear to have addressed the 

following issues: 

– the appropriate radionuclide and counting efficiency to 

be used in a given DR when the bioassay card lists 

gross beta or gamma counts (if this occurs)

– the appropriate radionuclide to assign when the 

bioassay card lists results in dpm or microcurie without 

a specific radionuclide

50
Observation 4: SC&A conclusion

◆ Although RPRT-0090 is not intended to be a 

guide for DR, addressing the information that will 

be needed for DR for radionuclides from Isotope 

Production is appropriate when evaluating RPRT0090. 

◆ SC&A recommends that this observation remain 

open.

51
Observation 5

The results in table 7-6 depend on inventory used 

52
Observation 5: SC&A summary of 

NIOSH response

◆ As indicated in observation 1, the spreadsheet 

SC&A referred to contained only the results of the 

review of Isotope Group sales/inventory data.

◆ Additional research was conducted for 

radionuclides in table 7-6 when information was 

incomplete. Information on the inventory 

discrepancies is provided in table 3, p. 12, of 

NIOSH’s 2020 response.

53
Observation 5: SC&A response

◆ SC&A evaluated NIOSH’s 2020 response and the 

additional information in table 3 (p. 12).

◆ SC&A analyzed the additional data and 

references and concurs with NIOSH’s response 

that addresses the issues summarized in table 3 

of SC&A’s 2018 review concerning table 7-6 of 

RPRT-0090.

54
Observation 5: SC&A conclusion

◆ SC&A finds that this observation has been 

addressed and recommends closure.

55
Observation 6

Additional information comparing RaLa production 

information to commercial operations should be 

provided 

56
Observation 6: SC&A summary of 

NIOSH response

◆ NIOSH agrees that RaLa radioiodine production 

and commercial radioiodine production are 

different.

◆ Both activities were done in the same areas with 

the same radiological controls.

◆ Unlikely workers (1955–1962) were exposed to 

levels that would have triggered the monitoring 

program.

57
Observation 6: SC&A response

◆ Extrapolating exposure estimates from one period to another 

requires careful comparison of operations.

– Implementation criteria (IG-006) require comparison of operations 

even when combining multiple years for co-exposure analysis

– Production output for commercial operations 1956–1962 (limited 

monitoring data) was significantly higher than commercial output 

1947–1949 (proposed co-exposure period)

◆ Contention that workers (1956–1962) were not exposed to 

levels that would have triggered monitoring cannot be 

evaluated.

– Limited monitoring data 1956–1962

– Reason for applying co-exposure estimates for 1947–1949

58
Observation 6: Comparison of 

radioiodine production

59
Observation 6: Additional 

consideration

◆ Unclear if commercial operations are relevant to 

EEOICPA.

◆ Does not appear the operations (commercial 

versus DOE) can be separated.

◆ Dose reconstruction requirements when 

commercial operations are present may need 

clarification.

60
Questions?

61