Savannah River Site Special Exposure 

Cohort Petition Evaluation 

Radiological Monitoring for Neptunium

Timothy D. Taulbee, Ph.D., CHP

Research Health Scientist

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support

February 2014

Cincinnati, OH
Overview

 Neptunium Processes at Savannah River Site 

(SRS)

 Radiological Controls at SRS

• Special Hazards Bulletins

• DPSOP-40

 Personnel Monitoring for Neptunium

• Bioassay

• Whole body Counting

 Neptunium Co-worker Model (ORAUT-OTIB-0081)

 A Comparison of Co-worker models for 

Neptunium (ORAUT-RPRT-0056)
Neptunium Processes at SRS

 Overall Goal was the production of Pu-238 

Np-237 (n, γ) Np-238  Pu-238

 Production started in 1961

 Production ended in July 1984

 Main Processes involving Np

• Manufacture Np targets (200 and 300 area)

• Irradiate targets in reactors (100 area)

• Chemical Separation of Pu-238 from Np (200 area)
Neptunium Flow Diagram
HB-Line Np Process

 Mission: Conversion of Np nitrate to Np oxide

 ABRWH toured HB-Line in 2010

 Two main sources of Np nitrate (97%)*

• HM Process from enriched uranium (EU)

‒ Approx. 3-4 kg / month (23% of total)*

‒ Low plutonium contamination

• Frames – dissolving irradiated Mk-53 targets

‒ Approx. 8-10 kg / month (74% of total)*

‒ Significant plutonium contamination

 * ESH-HPT-96-117
Pu contamination from HB Line

Report # NpO2 

(kg)

Minimum 

Pu wt%

Average 

Pu wt%

Maximum 

Pu wt%

# Billets 

made (235F)

# Tubes Extruded 

(321M)

SRDB #

DPSP-74-1-1 21.80 <0.05 0.16 0.60 5 12 72893

DPSP-74-1-2 4.84 0.18 0.36 0.53 7 12 72894

DPSP-74-1-3 12.65 0.02 0.18 0.42 5 0 72895

DPSP-74-1-4 5.25 0.01 0.03 0.06 4 14 72896

DPSP-74-1-5 2.25 0.25 0.28 0.32 0 0 72897
Why is Pu contamination important?

 Specific Activity

(alpha activity)

• Pu-238 = 17.1 Ci/g

• Np-237 = 0.00069 Ci/g

 NpO2 - Plutonium is the main hazard

 Requires ultra pure Np for it to dominate 

exposure 

Np wt% Pu wt% Pu : Np 

alpha ratio

99.5 0.5 125 : 1

99.9 0.1 25 : 1

99.95 0.05 12 : 1

99.99 0.01 2.5 : 1

99.995 0.005 1.2 : 1

99.999 0.001 0.25 : 1
Neptunium Billet Fabrication 235F

DPSTSA – 200-5 
Neptunium Billet Glovebox Line

DPSPF 30200-6 (1980) 
Neptunium Billet Glovebox Line

Maintenance side of glovebox line
235-F Summary / Observations

 Relatively small glovebox line 

• (10s of workers not 100s)

 Regulated radiation area

• Supervisors – White Lab coat shoe covers

• Operators – White regulated clothing and neutron 

dosimeters

 Shadow shields due to high gamma dose rate

 Billets are bagged for transfer to 321M
Radiological Controls - 235F

 Neptunium billets surveyed before transfer

• High gamma dose rate

• Neutron component is about 1%
Radiological Controls - 235F

 Plutonium billets surveyed before transfer

• Lower gamma dose rate

• Neutron component is about 25%
Radiological Controls - 235F

 Engineered Controls

• Gloveboxes

 Workplace Radiation 

monitoring 

• Daily control surveys

• Fixed Air Samples 

• Continuous Air Monitors 

(CAMs)

 Personnel Protective 

Equipment 

• Anti-contamination 

clothing
235F Routine Air Monitoring
235-F Personnel Monitoring

 Dosimeters

• Must wear dosimeter in regulated areas

‒ Gamma dose rate was significant

‒ Interviews indicate workforce swap-out

‒ Operators were required to wear neutron dosimeters

 Bioassay (DPSOL 193-302 Rev 8, 1978)

• 235-F workers bioassay category C and W

‒ C = 2 plutonium samples per year

‒ W = 1 neptunium sample per year
321M Np Billet Extrusion

 Billet Extrusion Process

1. Bagged Billets are received

2. Billets are surveyed

3. Billets are helium leak checked

4. Billets are outgassed

5. Billets are preheated

6. Billets extruded into long thin tubes

7. Tubes are surveyed for shipment to reactors
321M Np Billet Survey - Example
321M Np Billet Extrusion

Bebbington (1990) History of DuPont at the Savannah River Plant
321M Np Billet Extrusion

Bebbington (1990) History of DuPont at the Savannah River Plant
321M Np Tube Survey - Example
Radiological Controls 1972-1990

 Since 1956 Special Hazards Bulletins and DPSOP40 Savannah River Plant Radiation and 

Contamination Control covered: 

1. Work in Regulated Areas

2. Investigating radiation and contamination incidents

3. Protective clothing

4. Injury in regulated areas

5. Disposal of contaminated waste

6. Fires in regulated areas

7. Radiation exposure control
Work in Regulated Areas

 Definitions

 Basic Procedure

 Responsibilities

Special Hazards Bulletin #1, SRDB 86188, p. 163
Definitions and Basic Procedure

Special Hazards Bulletin #1, SRDB 86188

Special Hazards Bulletin #1, SRDB 86188
Basic Procedures & Responsibilities

Special Hazards Bulletin #1, SRDB 86188

Special Hazards Bulletin #1, SRDB 86188
SHB #3 - Protective Clothing

Special Hazards Bulletin #3, SRDB 86188, p. 166
DPSOP-40 

Control Guides
Special Hazards Bulletin #7 

Radiological Exposure Control

Special Hazards Bulletin #7, SRDB 86188, p. 61
DPSTS-RH-0.07 – Personnel Monitoring
Bioassay 

Control

 DPSOL 193-302 

• Rev. 5 (1971)
Bioassay Control - Construction

DPSOL 193-302 (Rev 5. 1971)
Bioassay Control Procedure Revision
Bioassay 

Control

 DPSOL 193-302 

• Rev. 8 (1978)

 DPSOL 193-302T 

• Rev. 0 (1985)

 DPSOL 193-211 

• Rev. 0 (1989)
Bioassay 

Control

 DPSOL 193-302 

• Rev. 8 (1978)

 DPSOL 193-302T 

• Rev. 0 (1985)

 DPSOL 193-211 

• Rev. 0 (1989)

DPSOL 193-302T (Rev 0 1985)
Bioassay Control - Construction

DPSOL 193-302T (Rev 0 1985)
Bioassay Control Summary

 Monitoring prescribed by work area

 Monitoring frequency is based on potential for 

exposure 

 Post 1978 - Neptunium urine bioassay for 

highest exposure potential area (235F)
SHB #2 - Radiological Incidents
Radiological Incident Reporting

 Special Hazards Investigations (SHI)

• Serious incidents – Initiated upon request from either 

Department or Health Physics

 Department or Area Incident reports

• DPSP Reports (Reactor Incidents, Separations, etc...)

• DPST Reports (Technical Area – 773A)

 Health Physics Logbooks
Neptunium Incidents

HB-Line (Jan 1972)

One construction worker continued installation of Pu-Np partitioning 

equipment in the JT·3 process cabinet in Room 311. Transferable 

contamination was measured up to 10e8 dpm/ft2 and gamma 

radiation exposure rates to 100 mR/hr were measured in the 

cabinet. Plastic suits were worn for personnel protection and 

containment huts were used for contamination control. Even with 

these precautions, as one employee undressed following work, he 

contaminated his hair to 80,000 dpm and his right cheek to 30,000 

dpm. A second employee contaminated his coveralls to 40,000 dpm 

when a seam in his plastic suit failed. Bioassay analyses indicated 

that neither employee assimilated radioactive materials (SRDB 

68265).
Neptunium Incidents

235F (Nov. 1974)

Two Maintenance mechanics and a Separations operator received 

nasal contamination to 420 dpm, 25 dpm, and 30 dpm, respectively, 

due to a process cabinet glove failure while working in the 

Neptunium Compact Operating Room. The Maintenance mechanic 

with the highest nasal contamination also had contamination to 

10,000 dpm on his wrist. There were five other persons in the room 

at the time; their nasal smears were negative. Bioassay sampling for 

the three persons with positive nasal smears were initiated. A survey 

of the room one failed glove and 14 contaminated gloves. The failed 

glove was contaminated to 8,000,000 dpm alpha with levels to 

100,000 dpm on the other 14 [gloves]. The floor was contaminated 

up to 100,000 dpm/ft2 (SRDB 68041).
Neptunium Incidents

235F (Oct. 1978)

An operator working in the neptunium line incurred nasal 

contamination of 190 dpm when a cabinet glove failed. The glove 

was contaminated to 10,000 dpm and the floor to 2000 dpm/0.1 m2. 

Room airborne activity remained less than RCG during the incident. 

Nasal irrigation promptly removed the contamination. A follow-up 

chest count of the operator indicated less than the minimum 

detectable amount and urine sample results were negative (SRDB 

68282).
Neptunium Incidents

321M (Nov. 1978)

Alpha contamination to 200,000 dpm was detected in a 1.5 mm wide 

and 1.5 cm long crack on the cladding of an extruded neptunium 

tube. No transferable or airborne contamination was detected. 

Gamma exposure rates to 200 mR/hr were measured 45 cm from the 

tube (SRDB 68347).
Neptunium Incidents

321M (Jun. 1980)

Transferable contamination to 3,000,000 dpm alpha/1000 cm2 was 

detected on the hood furnace floor, valves, and manifold fittings 

upon completion of neptunium billet outgassing. No particulate 

airborne radioactivity was detected in the work area. Employees 

wore appropriate respiratory protection. All equipment was 

decontaminated to less than 500 dpm alpha/1000 cm2 (SRDB 68325)
Radiological Controls (1990-2007)

 Radiation Work Permit System implemented in 

1990 

 SRS implemented a new radiation control 

manual (WSRC-5Q) in 1991 to comply with DOE 

Order 5480.11, it was updated as follows to 

comply with:

• 1992 DOE Radiological Control Manual DOE N 5480.6

• 1994 DOE Radiological Control Manual DOE/EH-0256T

• 1995 Occupational Radiation Protection 10CFR835
Neptunium Monitoring Data

 Three time periods

• 1961 – 1969: Urinalysis (separations, gross alpha)

• 1970 – 1989: Limited Urinalysis (Whole Body Counts)

• 1990 – present: Urinalysis (alpha spec)

 DPSOL 193-302 and DPSOL 193-211

• Monitoring prescribed by area

• Monitoring prescribed for Construction workers

‒ Job Plans prescribe for non-routine exposures
Neptunium Monitoring Data

Year # of Neptunium Samples Identified 

in Works Technical Reports

# of Neptunium Urine Samples located in 

other Pu, EU, Am Logbooks

1972 22 20

1973 31 17

1974 42 18

1975 No Listing in Report

1976 No Listing in Report

1977 No Listing in Report

1978 No Listing in Report

1979 11 1

1980 48* 49

1981 57 19

1982 146 78

1983 22* 25

1984 37* 48

1985 13* 14

1986 No Summary Report

1987 No Summary Report

1988 No Summary Report 30

1989 No Summary Report 14

* Only partial year information currently available
Neptunium Monitoring Data

Year Number of Samples by Area

 235-F HB Line 321M 773/772-F other

1972 20 

1973 16 1 

1974 17 1 

1975 

1976 

1977 

1978 

1979 1 

1980 36 8 3 2 

1981 3 2 9 3 2 

1982 36 32 6 3 1 

1983 12 4 7 2 

1984 23 5 16 4 

1985 7 2 3 2 

1986 

1987 

1988 5 5 16 4 

1989 3 9 2 

Total 178 50 41 49 15

 333 Np urine 

samples 

 Area frequency 

based on exposure 

potential

 Most are from 

235F 
Np Dose Reconstruction Methods

 At least four methods that NIOSH could use to 

develop a co-worker model in order to estimate 

Np exposures in the 1970 to 1990 timeframe: 

1. Use the limited bioassay

2. Ratio Np from the Pu bioassay given that the Pu 

activity is between 2-10 times greater than Np 

activity (best estimate for an epidemiology studies)

3. Interpolate between urine bioassay points between 

1969 and 1990 

4. Use whole body count data to develop co-worker 

model (most claimant favorable)
NIOSH Co-worker Model

 NIOSH chose to use whole body count 

information because:

• At the time NIOSH didn’t have complete information 

on the actual Pu:Np ratio (data has now been copied)

• NIOSH had confirmed that workers in Np areas were 

required to have whole body counts

‒ Shift employees - 2/year

‒ Day employees - 1/year

• Np doses calculated using WBC (Whole Body Count) 

are claimant favorable upper bounds but not 

unreasonably high as to be insufficiently accurate 
NIOSH Co-worker Model

 50 year equivalent doses

Organ 50-Year Equivalent Dose (rem)

Urinary Bladder 0.352

Breast 0.352

Kidneys 0.958

Liver 4.280

Red Bone Marrow 10.300

Bone Surface 268.000

Stomach 0.352

Lung 6.920

Even the 268 rem / 50 years = approximately 5 rem / year
Np Co-worker Model and Bioassay
Np Co-worker Model Comparison

ORAUT-RPRT-0056 

 Stratified the monitored workforce

• Construction Trades Workers (CTWs)

• Non-Construction Trades Workers (nCTWs)

• Unknowns (no unknowns from 1974-1989)

 Developed two co-workers models

• CTW Model

• nCTW Model
Np Co-worker Model Comparison

 Peto-prentice test

 Significance level

• p < 0.05

 Since no comparison year 

was less 0.05 we could not 

conclude that they were 

different

 Comparison methodology 

is being discussed in SEC 

Workgroup

Period p-value

CTW:nonCTW

1961 0.243

1962 0.899

1963 0.075

1974 0.876

1975 0.075

1977 0.975

1978 0.516

1979 0.666

1980 0.821

1981 0.310

1983 0.235

1984 0.850

1985 0.441

1986 0.685

1987 0.445

1988 0.142

1989 0.288
Construction Exposures

 Construction Personnel 

Monitoring

• Dosimeters required for regulated 

areas

• Construction worker interviews:

“Regulated Area posted one day 

and then postings removed for 

construction work.”
Supplemental TLD Badges for 

Construction

SRDB: 56619 p.131
Supplemental TLD Badges for 

Construction

SRDB: 56619 p.170
Supplemental TLD Badges for 

Construction

SRDB: 56619 p.88
Construction Worker Exposures

 Radiological records and construction personnel 

interviews are actually consistent.

 There are times when construction trades were not 

monitored because of low potential.

 There are times when construction trades were 

monitored but did not know it. The monitoring was of 

the workplace not them personally. 

 In the case of Np due to the very high photon dose rate 

we contend that all CTWs that had a potential for 

neptunium exposure were personally monitored.