Document Number:

Office of Compensation Analysis and Support OCAS- TIB-OO7

Technical Information Bulletin

Effective Date: 09/17/2003

Revision No. 0

Neutron Exposures at the Savannah River Site Page 1 of 6

'~\.AI~ ~ ~- Approval: Supersedes: J.W.

None

RECORD OF ISSUE/REVISIONS

1.0 Purpose

This Technical Information Bulletin provides guidance on when neutron exposures should be

included in Savannah River Site dose reconstructions. Due to changes in monitoring practices at

the Savannah River Site, energy employees who worked at the site prior to the implementation

of the Thermoluminescent Neutron Dosimeter (TLND) in 1971 might or might not have been

adequately monitored for neutron exposure. In addition, some of the energy employees who

were monitored for neutron exposure might or might not have a recorded neutron dose due to

the use of Nuclear emulsion Type A (NT A) film, which generally under responded to neutrons

below 500 keV. As a result, neutron monitoring records prior to 1971 are generally considered

inadequate for indication of neutron exposure.

Starting with the use of the TLND in 1971, routine workers with significant potential for neutron

exposure were adequately monitored with the TLND. Their dose and missed dose should be

calculated in accordance with the External Dose Reconstruction Implementation Guideline'.

There are some workers who depending on their job classification might have been intermittently

exposed to low-level neutrons. The general criteria for neutron monitoring in the 1970s through

late 1980s was determined based on being exposed to a neutron field greater than or equal to 1

mrem/hr. As a result, non routine workers might or might not have been adequately monitored
for neutron exposure depending on where in the facility they were conducting their work.

Starting around 1 989, SRS used the DOE criteria of the potential for 100 mrem/year as the

basis for who was monitored for neutron exposure.

In the following sections, this bulletin provides general guidance on when neutron exposures

should be considered in SRS Dose Reconstructions

2.0 Potential for Neutron ExDosure Drior to 1971

2.1 Work area is known

When exposure or work history records are sufficient to indicate that an energy employee

worked in any of the following areas, neutron dose should be included in the dose

reconstruction. These areas have been identified in Section 5.0 of the SAS Technical Basis

Document2 and are based on information in Brackenbush et al3 and other site documentation.4.s.6

A Area (300 & 700 Areas)

. Calibration Facility (736A)

. Savannah River laboratory (773A)

Reactor - 100 Area fC,K,L,P,R - Reactors)

. Only certain occupations involved neutron exposure, see section 2.2 for further guidance.

Separations - 200 Area (H and F Canyons)

. HB and FB lines (221Ft 221H)

. Plutonium Fuel Facility (235F)

. Production Control Laboratory (772F)

Fuel Fabrication - 300 Area

. Fuel Fabrication Facility (321 M) - Only during certain time periods, see section 2.2 for

further guidance.

2.2 Work area is unknown or not clear

When the work area is not known or is not clear, a Health Physicist should use professional

judgment to determine whether neutron exposures should be included. There is no single

definitive source document that can be used to determine whether an energy employee was

exposed to neutrons, however, from the weight of evidence investigation, a Health Physicist

should be able to determine the neutron exposure potential. The Health Physicist should keep in

mind the claimant favorable approach to dose reconstruction under EEOICPA and when there is

equal evidence of potential exposure, the approach should be to include the neutron exposure.

Listed below is some general guidance that can be used to assist in determining whether an

individual was potentially exposed to neutrons.
2.2.1 General indications of Dotential neutron eXDosure

1. If an energy employee was monitored for neutron exposure in 1971 or later, and they did

not change jobs or work area, the energy employee should be consid~red to have been

exposed to neutrons prior to 1971. The monitoring for neutrons increased dramatically

after the implementation of the TLND in 1971, thus contemporary monitoring is a good

indicator of potential for neutron exposure.

2. External dosimetry records indicate the 17 keY calibration curve was used for

interpretation of the shallow dose. This is an indication of exposure to plutonium and

therefore neutrons. This indicator could be for work in the 100, 200, or 300 areas.

3. Neutron exposure indicated in external dosimetry records between 1958-1962 (codes 32

and 33). This neutron dose might or might not have been separated in the HPAREH

summary sheet. In addition, the dosimetry cards prior to 1958 also contained an area for

fast neutrons (NF) and slow neutrons (NS) to be recorded. A close investigation of the

dosimetry records should be conducted to evaluate the potential for neutron exposure.

2.2.2 Area sDecific indications of Dotential neutron eXDosure

A Area (700 Area)

Indications, either through the Computer Assisted Telephone Interview (CATI), bioassay records,

or other information (i.e. incident reports), that the energy employee worked with Californium or

Curium. Curium was an intermediate step in the production of Cf-252. Cf-252 undergoes

spontaneous fission and is thus considered a strong neutron source. An indication of work with

either of these isotopes identifies individuals who were part of this project and have a potential

for exposure to neutrons.

Reactor - 100 Area fC,K,L,P,R - Reactors)

Neutron exposures should only be considered for energy employees who might have been

involved in maintenance activities in the crane wash areas of the reactors. These occupations

would include mechanics, pipefitters, electricians, carpenters, sheetmetal workers, etc... There

is also a potential for neutron exposure for radiological control technicians, health physicist and

possibly reactor operators, since these individuals were generally responsible for workplace

safety. Monitoring for neutron exposure in 1971 or later is again a strong indicator that the

energy employee performed work in the crane wash area and was potentially exposed to

neutrons.

During the loading of Pu-AI targets during certain campaigns, there are other workers in the

reactor areas who might have been exposed to neutrons. According to site personnel, during
these operations, the individuals involved would have been monitored for neutron exposure. As

a result, monitoring for neutrons in 1971 or later in the reactor areas is an indicator that an

energy employee performed this type of work.

Separations - 200 Area (H and F Canyons)

Routine (i.e. more frequent than annual) plutonium (Pu) bioassay monitoring, and a relatively

high shallow dose to deep dose ratio (> 2.0), and 3) relatively little enriched uranium (EU)

bioassay indicates the energy employee worked on either the FB or HB lines.

The high shallow to deep dose ratio is not always a clear indicator of neutron exposure in the

200 area. For example if there is numerous enriched uranium bioassay measurements in the

200 area, the energy employee most likely worked on the A lines and would have received little

to no neutron exposure. The high shallow dose is the result of beta exposure from uranium

daughter products.

Because certain occupations (crafts/trades) might have worked in both the A and B line areas of

the 221-F facilities, a claimant favorable weight of the evidence approach should be used to

evaluate the potential for exposure to neutrons. Clearly indications of work in the A-line or tank

farm areas demonstrate a lack of potential neutron exposure and should not be included. For

energy employees who worked in multiple areas, some modification to the neutron exposure

distributions provided in the SRS Technical Basis Documents2 might be necessary.

Fuel Fabrication - 300 Area

Bioassay monitoring for plutonium in 300 area. Generally this area was a uranium fuel

fabrication area. There were certain campaigns (time periods), however, in which plutoniumaluminum (Pu-AI) targets were manufactured in the 321-M facility4. These Pu-AI targets emitted

neutrons. Generally, there will also be indications that the 17 keV calibration curve was used to

interpret the shallow dose. The use of this calibration curve is an indicator of potential neutron

exposure. Currently research is being conducted to better determine the time periods in which

the 300 area manufactured Pu-AI targets. Research to date has indicated this work was

conducted in late 1964 through at least 1967. This work was most likely conducted in later

time periods as well, however this information has not been located.

3.0 Potential for Neutron Exposure (1971-present)

Routine workers were adequately monitored for neutron exposures starting in 1971 and later.

There is a potential for unmonitored neutron dose for non-routine (intermittent) workers who

occasionally visited neutron exposure areas. The criteria for monitoring were based on entry

into a neutron exposure field greater than or equal to 1 mrem/hr. Since all routine workers in

facilities with this level of a field were monitored, the non-routine (intermittent) workers are

expected to have received a neutron dose that was significantly less. Starting around 1989,
SRS adopted the DOE criteria of monitoring workers who had a potential of exceeding 100

mrem/yr. As a result the neutron dose for unmonitored workers from 1989 to present is

considered to be significantly less than 100 mrem/yr.

3.1 Non-Routine Workers (1971-1989)

For non-routine workers with photon monitoring, however no neutron monitoring, a careful

evaluation of their work location, job description (classification), CATI, and photon exposure

history should be conducted to determine whether neutron dose should be included in the dose

reconstruction.

The following criteria should be met to determining whether neutron dose should be added.

1. Work Location - If the work location is any of the areas noted in section 2.1, then

neutron exposures should be considered providing the other criteria are met.

2. Job Description (Classification) or CA TI - If either the job description or the CA TI

indicates a type of work that could result in only intermittent exposure to neutrons in an

area listed in section 2.1, then neutron exposure should be considered. An example of a

job type that might result in intermittent neutron exposure would be a quality

control/production inspector or inventory/accountability clerk.

3. Positive Photon Exposure - The energy employee ~as a measured photon dose (not

missed dose).

When an energy employee has been evaluated as exposed to neutrons but not monitored, the

neutron/photon ratios discussed in the SRS Technical Basis Document2 should be applied. While

these estimates will tend to overestimate the neutron dose especially considering the ratios were

developed based on routine workers, they are considered reasonable but claimant favorable.

4.0 Clarification on use of neutron to Dhoton ratio

The neutron to photon ratio should only be applied in cases where the neutron monitored is

considered inadequate. There are some locations at SRS where the neutron monitoring was

adequate and workers received a measured dose. When the measured dose is greater than the

estimated dose using the neutron to photon ratio, the measured dose should be applied. For

1971 and later, the uncertainty in this measured neutron dose should be estimated using

information in the SRS Technical Basis Document2 in conjunction with the External Dose

Reconstruction Implementation Guideline.'
5.0 Summary

For further information on whether neutron dose should or should not be included in the

Savannah River Dose reconstructions, documents listed in the reference section of this bulletin

provide additional details of SRS operations and associated neutron exposures.

A claimant favorable weight of the evidence approach with particular attention to the source

information identified in section 2.2.1 (monitoring in 1971 or later, use of 17 keY calibration

curve for shallow dose, and neutron monitoring identified in early dosimetry records) should be

used when the work location and or activities are not clear.

6.0 References

1. NIOSH, (2002) External Dose Reconstruction Implementation Guideline, Rev 1, OCAS-IG001, National Institute for Occupational Safety and Health, Office of Compensation Analysis

and Support, Cincinnati, Ohio.

2, ORAU Team, ORAUT -TKBS-0003, Technical Basis Document for the Savannah River Site To

Be Used for EEOICPA Dose Reconstructions, (2003)

3. Brackenbush, L. W., Soldat, K. L., Haggard, D. L., Faust, L. G., and Tomeraasen, P. L.

Neutron Dose and Energy Spectra Measurements at Savannah River Plant, Richland,

Washington, PNL-6301, (1987)

4. Dupont. Progress Report: Works Technical Department - August 1965, Savannah River

Plant, DPSP 65-1-8, (1965)

5. Taylor, G. A., Crase, Kenneth W., LaBone Thomas R., and Wilkie, W. H. A History of

Personnel Radiation Dosimetry at the Savannah River Site, Aiken, South Carolina, WSRC-RP95-234, (1995)

6, Bebbington, W.P. History ofDu Pont at the Savannah River Plant. E.:

and Company, Wilmington, Delaware 0-934870-27-6 (1990).

du Pont de Nemours