SC&A Review of SEC-00188 Evaluation 

Report Addendum 2 for Sandia 

National Laboratories – Albuquerque

Bob Barton, Ron Buchanan, Joe Fitzgerald

SC&A, Inc.

Advisory Board on Radiation and Worker Health, Sandia 

National Laboratory – Albuquerque, Work Group

March 3, 2022
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SC&A review of SEC-00188 ER Addendum 2

 External Dose:

– No issues that preclude dose reconstruction with sufficient accuracy. 

– Questions remain on the application of dosimetry data to reconstruct 

exposures to severe radiation gradients encountered at the Sandia 

Pulse Reactor (SPR). [1 observation]

 Internal Dose: Weight of evidence supports feasibility of dose 

reconstruction with sufficient accuracy for 1997–2011. However, SC&A 

unable to verify completeness of breathing zone (BZ) monitoring results 

due to lack of available records from which the total number of workers 

monitored via BZ, or the total number of BZ samples issued and 

processed, could be tabulated. [1 finding, 6 observations]
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SC&A conclusions 1 & 2: ER Addendum 2

1. Is weight of evidence sufficient for feasible external and internal dose 

assessment?

Answer: Yes. But for external dose assessment, questions remain about 

reconstructing severe radiation gradients at SPR and how NIOSH will 

apply available data. For internal dose assessment, unable to verify fully 

the completeness of BZ monitoring results; other clarifications 

requested.

2. Was implementation of 10 CFR Part 835 requirements for internal 

exposure monitoring adequate to support 100 mrem committed effective 

dose equivalent (CEDE) annual monitoring requirement as bounding 

value in co-exposure model?

Answer: Yes. Program implementation documented by end of 1996.
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SC&A conclusions 3 & 4: ER Addendum 2

3. Any limitations or uncertainties related to SNL-A reliance on personnel 

air sampling results as indicators for assignment of 100 mrem CEDE 

dose?

Answer: Weight of evidence supports this assignment, with limitations of 

available BZ monitoring records mitigated by conservatism of NIOSH 

approach.

4. Is there evidence that security guards at SNL-A were potentially exposed 

to unmonitored intakes in excess of 100 mrem CEDE per year? 

Answer: SC&A concludes that it is unlikely that security guards would 

have received an intake at or in excess of this annual dose.
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Finding 1: Direct evaluation of record 

completeness is not possible

 SC&A: Unable to locate references, such as periodic health physics 

reports, that tabulate the total number of workers monitored via BZ nor 

the total number of BZ samples issued and processed. Thus, a direct 

evaluation of the completeness of captured BZ results is not currently 

feasible. 

 NIOSH response: 

– NIOSH (2021) agrees that the dataset of raw field-monitoring data sheets is 

incomplete.

– NIOSH notes that for 1997–2002 there were 965 sample entries in DAC-hr tracking 

logs and a dataset of 3,741 raw BZ samples available for comparison.

– Evaluation indicates that 952 (or 98.7%) of samples found in DAC-hr logbooks were 

also located in NIOSH’s available dataset for evaluation. 

– NIOSH conclusion: Dosimetrically significant BZ samples were included in the 

dataset.
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SC&A reply and recommended status

 SC&A reiterates that the conclusion reached in its Addendum 2 ER 

review was that a bounding dose reconstruction approach for 

unmonitored workers or partially monitored workers is likely feasible 

based on the weight of available evidence (SC&A, 2020, p. 7).

 SC&A concurs with the NIOSH response about potential biases 

based on a comparison with DAC-hr tracking reports (1997–2002 

only, 63 of 173 applicable months). 

 Nonetheless, the determination of acceptable levels of 

incompleteness in a feasibility context is ultimately a subjective 

judgment that should be discussed by the work group.

 Therefore, SC&A recommends this finding remain in progress 

pending work group discussion.
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Observation 1: Duplicate samples and total 

breathing zone samples

SC&A identified 151 duplicate samples analyzed for 2002 in 

Addendum 2 of the petition evaluation report (ER) (NIOSH, 

2019). These samples should not be included in reported BZ 

totals and should be removed from any exposure estimates. 

Furthermore, when reporting the total number of BZ samples, the 

distinct measurements (gross alpha, gross beta, low-energy beta, 

and tritium) should not be counted as separate and distinct BZ 

samples.
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Observation 1: NIOSH response

For duplicate samples:

 NIOSH (2021) confirmed the 

presence of 148 usable samples that 

were duplicates.

 NIOSH removed the duplicate 

entries, repeated the original 

analysis, and found little to no impact 

on results.

 To be expected due to the large 

number of zero or negative results 

that require imputation.

For total breathing zone samples:

 More appropriate comparison would 

be to the actual number of BZ 

component measurements (alpha, 

beta/gamma, and tritium).

 Reiterated that analyzing the BZ data 

by alpha, beta, and tritium samples 

separately is appropriate and 

claimant favorable.

 Dose from alpha was orders of 

magnitude larger than the other 

components (beta/gamma, lowenergy beta, and tritium).
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Observation 1: SC&A reply and recommended 

status (observed duplicate samples)

 SC&A and NIOSH agree that there were duplicate BZ results 

inadvertently entered and analyzed for 2002. 

 NIOSH has appropriately reanalyzed the data, and it had little to no 

effect on calculated results. 

 Although NIOSH indicated that it could not find duplicate entries for 

other years identified in table 1 of SC&A (2020), resolving these few 

discrepancies observed by SC&A would have no effect on the 

resulting analysis and proposed methods for dose reconstruction. 

 Therefore, SC&A recommends the part of observation 1 concerning 

duplicate samples be closed.
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Observation 1: SC&A reply and recommended 

status (total reported BZ samples)

 SC&A’s comparison was to table 6-1e, “Available Breathing Zone Air Monitoring 

Results: 1997-2011,” in section 6 of the SEC ER (NIOSH, 2019).

 NIOSH’s 2021 response states on page 7: “the tabulation for Section 6 

(i.e., Table 6-1e) is related to the number of line items of data available to 

NIOSH – with each line item potentially containing more than one result type.”

 SC&A understands where the discrepancies between the NIOSH SEC ER 

tabulation and SC&A’s own analysis arise.

– However, SC&A believes that this characterization of the data is misleading and 

overstates the actual amount of available data.

– SC&A recommends further discussion with the work group and potentially revising the 

SEC ER.

 SC&A agrees with the final aspect of NIOSH’s (2021) response, which defends 

separating BZ results by radiation type for the purpose of evaluating the 

magnitude of exposures. (SC&A never has questioned this.) 
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Observation 2: Temporal variation indicates 

incomplete dataset

 SC&A: Observed temporal variation in number of captured BZ samples 

suggests available dataset does not represent a complete set of 

monitoring records for affected worker population. Therefore, any 

conclusions about exposure potential reflected in captured BZ samples 

are likely based on incomplete data.

 NIOSH response: 

– Agrees that the BZ dataset is not complete.

– Believes the dataset is likely biased high (all data transmitted to the 

internal dosimetry group for DAC-hr tracking purposes are included).

 SC&A reply and recommended status: SC&A and NIOSH agree. SC&A 

recommends that observation 2 be subsumed under finding 1 

discussions.
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Observation 3: Use of WebDose to establish 

completeness and bounding dose estimate

 SC&A: Comparison of BZ entries in WebDose to captured hardcopy 

records demonstrates that WebDose does not represent a complete data 

source reflecting who was monitored via BZ at SNL-A. Therefore, the use 

of WebDose to support the 100 mrem dose threshold may not be 

appropriate.

 NIOSH response: 

– Concurs with SC&A observation that WebDose dataset does not 

contain entries for all collected BZ samples.

– Notes that WebDose entries represent a complete assessment of most 

highly exposed worker population.

– Constitutes an additional piece of evidence that a bounding dose 

reconstruction methodology is feasible.
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Observation 3: SC&A reply and 

recommended status

 SC&A reviewed the WebDose database against available 

DAC-hr logbooks and agrees with NIOSH’s conclusion that 

100% of those logbook entries are contained in WebDose.

 Provides weight of evidence that the available dataset contains 

the dosimetrically significant BZ results (and is potentially 

biased high).

 SC&A recommends that observation 3 be subsumed under 

finding 1 discussions.
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Observation 4: Distribution of breathing zone 

samples among individual workers

 SC&A: Substantial portion of available BZ samples per year are 

often assigned to just a few individuals. Approximately 8% of total 

BZ samples were associated with just a single individual, though 

over 195 monitored individuals were identified. Nearly 80% of 

identified individual workers in a given year had 20 BZ samples or 

fewer.

 NIOSH: Concurs with this observation and believes that it does not 

affect the conclusion that a bounding dose reconstruction 

methodology is feasible. This methodology using 100 mrem per 

year of internal dose for unmonitored or partially monitored workers 

is claimant favorable and appropriate

 SC&A reply and recommended status: Recommend work group 

closure.
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Observation 5: Workers frequently monitored 

by BZ also participated in bioassay program 

 SC&A: 79 of 194 identified individuals in the captured BZ records 

also participated in the non-tritium bioassay program during 

evaluated SEC period. This includes identified workers with the 

highest number of BZ results per year and 11 workers with the 

highest number of BZ results over the entire period. Therefore, 

evidence suggests that workers who were most often monitored via 

BZ were also often monitored via non-tritium bioassay. (SC&A, 

2020, p. 25)

 NIOSH response: Concurs with SC&A’s observation and reaffirms 

its conclusion that the captured set of raw BZ monitoring records 

were among those with the highest potential for internal exposure. 

 SC&A reply and suggested status: Recommend work group 

closure.
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Observation 6: Fluctuations in exposure 

potential by year and work area

 SC&A:

– SC&A’s analysis of relative exposure potential demonstrates that 

noteworthy fluctuations in exposure potential can exist by year and by 

work area. 

– SC&A does not believe these fluctuations necessarily obviate the use 

of 100 mrem as a maximizing dose assignment to unmonitored 

workers, as several significantly conservative assumptions were 

included in the dose estimates. (SC&A, 2020, pp. 35–36)
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Observation 6: Fluctuations by year 
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Observation 6: Fluctuations by area 
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Observation 6: Mitigating factors

 Pu-239 was assumed for nearly all (i.e., greater than 99%) dose calculations, 

though lower derived air concentration (DAC) value radionuclides were 

applicable in several specific scenarios (e.g., depleted uranium or mixed fission 

products).

 Respiratory protection was never considered in the dose estimates, though 

consideration of such protection factors would lower the dose anywhere by a 

factor of 40 (standard air purifying respirator) to 10,000 (supplied-air bubble 

suit). Respiratory protection was used in over two-thirds of the available BZ 

events when transuranic material was identified as the contaminant of interest.

 The number of probable exposure events per year was likely much less than 

200 (SC&A, 2020, p. 23), which was calculated by NIOSH to result in 100 mrem 

at approximately 0.5 mrem per event. 

 Observed individuals with the most frequent number of BZ events were also 

included in the non-tritium bioassay program.
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Observation 6: NIOSH response and SC&A 

recommendation

 NIOSH: NIOSH concurs with the observation and does not 

believe these fluctuations obviate the use of 100 mrem as a 

maximizing dose assignment to unmonitored workers.

 SC&A reply and recommended status:

– Based on these mitigating factors, SC&A (2020, 2021) concluded that 

dose assessment using incomplete BZ data is sufficiently conservative 

to allow the conclusion that a bounding internal dose estimate of 

100 mrem on an annual basis is appropriate for unmonitored or 

partially monitored workers.

– Recommend work group closure.
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Observation 7: Sandia Pulse Reactor 

radiation gradient dose

 SC&A: Issue of exposure to severe radiation gradients would not be applicable 

to personnel working outside the immediate area of the bottom of SPR reactor 

vessel. However, potential exposures to maintenance and operating personnel 

while performing close-up work on SPR has not been sufficiently addressed and 

resolved.

 NIOSH: Finds that further research is needed for dose assignments for SPR 

workers. NIOSH intends to conduct additional review and research to determine 

the need for adjustment to recorded dosimetry doses. NIOSH will revise the 

external dose section of the SNL-A site profile to reflect any necessary changes 

to external dose assignment to SPR workers when using recorded dosimetry 

results.

 SC&A reply and suggested status: SC&A concurs with NIOSH’s plan to 

(1) conduct additional review and research and (2) document dosimetry 

practices in an update to the external dose section of the SNL-A site profile. 
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Summary of SC&A recommendations: 

Finding 1, observations 1–3

 Finding 1: Recommend some additional work group discussion to 

clarify issues remaining about data completeness.

 Observation 1:

– First part of observation about inclusion of duplicate samples should be 

closed.

– Recommend further discussion of the second part of the observation about 

the contents of table 6-1e, “Available Breathing Zone Air Monitoring Results: 

1997-2011,” in the NIOSH SEC ER. 

 Observation 2: Temporal issues should be subsumed under 

finding 1 discussion of data completeness.

 Observation 3: Use of WebDose as evidence of data bias should 

be subsumed under finding 1 discussion of data completeness.
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Summary of SC&A recommendations: 

Observations 4–6

 Observation 4: SC&A and NIOSH agree that the number of 

observed BZ samples per worker per year does not adversely 

impact the feasibility of dose reconstruction. Recommend closure.

 Observation 5: SC&A and NIOSH agree that the workers most 

often sampled by BZ also participated in the non-tritium bioassay 

program. Recommend closure.

 Observation 6: Despite temporal and location variation in exposure 

potential, SC&A believes the proposed dose reconstruction 

methodology is feasible and bounding based on three mitigating 

factors:

1. Conservative choice of contaminant for analysis (Pu-239)

2. No consideration of respiratory protection

3. Probable number of exposure events per year
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Summary of SC&A recommendations: 

Observation 7 and summary conclusion

 Observation 7: NIOSH will address the SPR radiation gradient 

dose in the next revision of the SNL-A site profile.

 Summary Conclusion: Assuming these followup activities are 

addressed, SC&A does not have any remaining concerns 

about the Addendum 2 ER and its conclusion that a bounding 

dose reconstruction method is feasible, sufficiently accurate, 

and claimant favorable for SNL-A during the evaluated period 

(January 1, 1997–May 21, 2011).
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References

National Institute for Occupational Safety and Health. (2019). SEC petition 

evaluation report Petition SEC-00188, Addendum 2 (1997–2011) (rev. 0). 

https://www.cdc.gov/niosh/ocas/pdfs/sec/sandianm/snlnmer-188-a2-508.pdf

National Institute for Occupational Safety and Health. (2021). NIOSH response to 

SC&A’s review of SEC-00188 Sandia ER Addendum 2 [Response paper]. 

https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-snlsec188erad2-508.pdf

SC&A, Inc. (2020). Review of SEC petition evaluation report: Petition SEC-00188, 

Addendum 2 (1977–2011), for Sandia National Laboratories – Albuquerque (SCATR-2020-SEC004, rev. 0). https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/scasec188erad2-508.pdf

SC&A, Inc. (2021). Reply to NIOSH’s response to SC&A’s review of the Sandia 

National Laboratories – Albuquerque SEC-00188 Addendum 2 evaluation report

(SCA-TR-2021-SEC006, rev. 0).