Memo to DRSC – Re: Allied DR 1 SC&A – May 12, 2015 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

MEMO

TO: Dose Reconstruction Subcommittee 

FROM: Ron Buchanan, SC&A 

SUBJECT: Major Differences in the three Dose Reconstruction Methods and their Resolution 

or Course of Action regarding Rocky Flats Plant Case #[Redact] 

DATE: June 16, 2015 

The dose reconstruction (DR) by NIOSH and the blind DRs by SC&A-Method A, and SC&AMethod B were discussed during the April 14, 2015, DRSC meeting. A summary of the doses 

assigned and probability of causation (POC) values are listed in the following table: 

Table 1. Comparison of Original Total External and Internal Dose Estimates and 

Resulting POC Values for the Lung 

Total Lung Doses NIOSH

(rem)

SC&A-Method A

(rem)

SC&A-Method B 

(rem)

External Doses:

 - Photons <30 keV

 - Photons 30–250 keV

 - Neutrons <10 keV

 - Neutrons 10–100 keV

 - Neutrons 0.1–2 MeV

 - Neutrons 2–20 MeV

0.030

1.562

0.118

0.036

1.037

0.457

0.019

1.488

0.129

0.027

0.882

0.400

0.030

2.254

0.171

0.036

1.157

0.524

Occupational Medical Dose 0.084 0.294 0.294

Internal Doses: Alpha 46.033 38.676 67.414

Total Lung Dose 49.357 41.915 71.880

POC 47.51% 56.71% 55.71%

The major areas of differences in the three DR methods, and their resolution or course of action, 

are as follows: 

1. Occupational Medical X-ray Frequency – Both of SC&A’s Method A and B assigned 

annual doses from medical x-rays exams, as per ORAUT-TKBS-0011-3. NIOSH assigned 

doses for the two medical x-ray exams as listed in the DOE records. SC&A pointed out that 

ORAUT-TKBS-0011-3, Table 3-1, page 8, indicates that it is claimant favorable to assign 

annual x-ray doses because the RFP DOE records NIOSH receives may not be complete 

concerning medical x-rays. NIOSH indicated that there is an RFP guideline that 

recommends x-ray exam doses be assigned according to the DOE records received. Status: 

This difference in DR protocol needs to be resolved. 

2. SC&A-Method A Missed Internal Dose Distribution – SC&A Method A assigned missed 

plutonium and americium doses into the IREP table as a geometric mean (GM) value of a 

lognormal distribution with a geometric standard deviation (GSD) of 3.0. However, NIOSH 
Memo to DRSC – Re: RFP DR 2 SC&A – June 16, 2015 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

pointed out that ORAUT-OTIB-0060, page 15, states that it should be assigned using a 

triangular distribution with a minimum of 0, mode of annual dose, and maximum of 2 × 

mode. When SC&A used this distribution for the internal doses in this case (with total dose 

of 41.915 rem) a POC value of 41.09% was derived. This is compatible with NIOSH’s POC 

value of 47.51% when a total dose of 49.357 rem was assigned. Status: This issue has been 

resolved and SC&A will use triangular distributions for missed internal dose in future DRs.

3. SC&A-Method B Internal Doses –

 DU: SC&A Method B assigned depleted uranium (DU) dose because the EE’s DOE 

bioassay records included a listing of analysis for uranium as well as plutonium. 

However, it was concluded that the EE worked in only the plutonium area and not in both 

the plutonium and uranium areas; therefore, assignment of uranium intakes/doses in this 

case would be an overestimate. 

 Missed Internal Dose Distribution: SC&A Method B assigned missed plutonium and 

americium doses into the IREP table as a GM value of a lognormal distribution with a 

GSD of 3.0. However, NIOSH pointed out that ORAUT-OTIB-0060, page 15, states that 

it should be assigned using a triangular distribution with a minimum of 0, mode of annual 

dose, and maximum of 2 × mode. 

 Plutonium/Americium: SC&A Method B assigned plutonium intakes/doses based on 

the Am-241 chest count data. However, during the April 14, 2015, DRSC meeting, it 

was found that the IMBA program that SC&A has available does not contain the “Addon” feature #10 that compensates for Am-241 ingrowth; this lack of adjustment results in 

the plutonium intake/dose results being greater than the values assigned by NIOSH. 

NIOSH indicated that the SC&A intake/dose values would need to be multiplied by 

approximately 55% to obtain the correct values. 

 SC&A-Method B Revised Doses and POC: SC&A revised the doses and POC values 

by (1) eliminating the DU doses, (2) assigning the missed internal doses with a triangular 

distribution, and (3) multiplying the derived plutonium doses by 55%. This resulted in a 

total dose assignment of 36.538 rem with a resulting POC of 38.15%. This is now in line 

with NIOSH’s DR and SC&A’s Method A results.

Status: SC&A needs to have the current version/add-ons, and associated training, for the IMBA 

program to be able to meaningfully compare DR methods and results.

The following is a revised summary table after incorporating the above modifications: 
Memo to DRSC – Re: RFP DR 3 SC&A – June 16, 2015 

Table 2. Comparison of Revised Total External and Internal Dose Estimates and Resulting 

POC Values for the Lung 

Total Lung Doses NIOSH

(rem)

SC&A-Method A

(rem)

SC&A-Method B 

(rem)

External Doses:

 - Photons <30 keV

 - Photons 30–250 keV

 - Neutrons <10 keV

 - Neutrons 10–100 keV

 - Neutrons 0.1–2 MeV

 - Neutrons 2–20 MeV

0.030

1.562

0.118

0.036

1.037

0.457

0.019

1.488

0.129

0.027

0.882

0.400

0.030

2.254

0.171

0.036

1.157

0.524

Occupational Medical Dose 0.084 0.294 0.294

Internal Doses: Alpha 46.033 38.676 32.072

Total Lung Dose 49.357 41.915 36.538

POC 47.51% 41.09% 38.15%

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.