ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 6

Document Title:

Assignment of Missed Neutron Doses 

Based on Dosimeter Records

Document Number: ORAUT-OTIB-0023

Revision: 01

Effective Date: 05/14/2008

Type of Document: OTIB

Supersedes: 00

Subject Expert(s): Matthew H. Smith

Site Expert(s): N/A

Approval: Signature on File Approval Date: 04/23/2008

Matthew H. Smith, Document Owner

Concurrence: Signature on File Concurrence Date: 04/23/2008

James P. Griffin, Deputy Project Director

Concurrence: Signature on File Concurrence Date: 05/14/2008

Kate Kimpan, Project Director

Approval: Brant A. Ulsh Signature on File for Approval Date: 05/14/2008

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-OTIB-0023 Revision No. 01 Effective Date: 05/14/2008 Page 2 of 6

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

03/07/2005 00 New technical information bulletin to provide information to allow 

ORAU Team dose reconstructors to determine when it is 

appropriate to assign neutron doses to workers at DOE sites using 

the LOD/2 method. First approved issue. Initiated by Steven E. 

Merwin.

05/14/2008 01 Approved revision to incorporate comments from ABWG on 

Procedures and align with page change to IG-001. Added minor 

editorial changes for consistency with current requirements, 

including the addition of an Acronym and Abbreviations list, 

incorporating an Introduction section to include standard OTIB 

language, and updating section numbers. No further changes 

occurred as a result of formal internal review. Incorporates formal 

NIOSH review comments. Training required: As determined by 

the Task Manager. Initiated by Matthew H. Smith.
Document No. ORAUT-OTIB-0023 Revision No. 01 Effective Date: 05/14/2008 Page 3 of 6

TABLE OF CONTENTS

SECTION TITLE 

Acronyms and Abbreviations ...............................................................................................................4

PAGE

1.0 Introduction ..............................................................................................................................5

2.0 Purpose ...................................................................................................................................5

3.0 Background..............................................................................................................................5

4.0 Applications and Limitations.....................................................................................................5

5.0 Analysis ...................................................................................................................................6

6.0 Guidance .................................................................................................................................6

7.0 Attributions and Annotations ....................................................................................................6

References ..........................................................................................................................................6
Document No. ORAUT-OTIB-0023 Revision No. 01 Effective Date: 05/14/2008 Page 4 of 6

ACRONYMS AND ABBREVIATIONS

DOE U.S. Department of Energy

DR dose reconstruction

IG implementation guideline

LOD limit of detection

NIOSH National Institute for Occupational Safety and Health

ORAU Oak Ridge Associated Universities

TIB technical information bulletin 
Document No. ORAUT-OTIB-0023 Revision No. 01 Effective Date: 05/14/2008 Page 5 of 6

1.0

Technical information bulletins (TIBs) are not official determinations made by the National Institute for 

Occupational Safety and Health (NIOSH) but are rather general working documents that provide 

historic background information and guidance concerning the preparation of dose reconstructions at 

particular sites or categories of sites. They will be revised in the event additional relevant information 

is obtained about the affected site(s). TIBs may be used to assist NIOSH staff in the completion of 

individual dose reconstructions.

INTRODUCTION

In this document, the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy (DOE) facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act of 2000 [42 U.S.C. § 7384l(5) and (12)]. 

2.0

The purpose of this TIB is to provide information to allow Oak Ridge Associated Universities (ORAU)

Team dose reconstructors to determine when it is appropriate to assign neutron doses to workers at 

DOE sites using the Limit of Detection (LOD)/2 method.

PURPOSE

3.0

According to OCAS-IG-001, missed doses are to be assigned using the “LOD/2 method,” which was 

originally proposed by the National Research Council in their evaluation of film badge dosimetry for 

compensation of atomic veterans. The method involves the assignment of a dose equal to the LOD 

divided by 2 for each dosimetry measurement that is recorded as either zero, below the limit of 

detection, or below a reported threshold. According to the IG, this method is recommended “since 

this scheme has been used in other compensation programs and has been shown to result in a slight 

positive bias.” 

BACKGROUND

Workers who were unmonitored for external radiation exposure are not assigned missed dose using 

the LOD/2 method; rather, they are assigned either external on-site ambient doses, if they were nonradiological workers and would not have been exposed to workplace radiation sources; or 

unmonitored doses (using coworker studies or some other approach) if a potential for exposure 

existed.

The assignment of missed neutron doses is somewhat more complex. In the early years at most 

DOE sites, neutron doses were not measured reliably, so missed neutron doses are assigned based 

on neutron-gamma ratios, coworker studies, or some other approach. In these situations the 

guidance given in this TIB will not apply. This TIB does provide further guidance regarding when to 

apply missed neutron dose if data from neutron monitoring devices are used for dose reconstruction 

and when other information is available regarding the energy employee’s potential for neutron 

exposure.

4.0

The guidance in this TIB applies to cases in which the data from neutron monitoring devices in use at 

the site were used in dose reconstruction. It does not apply to periods during which the monitoring 

was unreliable and some method other than the monitoring data (e.g., neutron-gamma ratios) is 

normally used to assign neutron dose based on information in the site technical basis document 

(TBD) or other reliable source.

APPLICATIONS AND LIMITATIONS
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5.0

As described in OCAS-IG-001, the LOD/2 method results in a positive bias for photon exposures. By 

definition, this bias is extreme if there was no potential for photon exposure (e.g., a worker downtown 

in an administrative building who did not visit the site). By and large, however, workers who were

issued dosimeter badges at DOE sites had a potential for photon exposure, and photon radiation 

sources were generally omnipresent at the sites so the issuance of dosimeter badges is considered 

an indicator of the potential for exposure. Thus, even though the LOD/2 method for assigning missed 

dose is claimant favorable in general, and highly claimant favorable for employees with limited or no 

potential for exposure (i.e., employees with all or mostly zeroes in the records), this approach has 

been prescribed in the IG upon analysis of alternative approaches.

ANALYSIS 

Regarding neutron exposures, however, at some DOE sites and during certain eras, neutron 

dosimeters were included in the site dosimetry badges as a matter of administrative practice rather 

than as an indicator of a potential for neutron exposure. Thus, some employees have a string of 

zeroes in the neutron column in their monitoring records even though there may have been little or no 

exposure potential based on their work locations. Additionally, at a few DOE sites zeroes may be 

included in the records as an administrative practice even though monitoring did not occur. 

Therefore, not only are there instances in which the LOD/2 method results in unreasonably high 

neutron doses, as acknowledged in the IG, but also instances in which the method is not applicable 

because it could result in the assignment of neutron doses even though there was no potential for 

neutron exposure.

6.0

Workers who were monitored for neutrons using reliable dosimeters should generally be assigned 

missed doses in accordance with OCAS-IG-001 (i.e., using the LOD/2 method for any null results). 

An exception, however, to the method is needed for unreasonably high neutron doses.

GUIDANCE

Missed neutron doses do not need to be assigned if the following condition is met:

The dose reconstructor determines that the employee’s neutron dose was zero or incidental relative to 

the external dose assigned based on the employee’s work location(s) and relevant information in the 

site TBD or other documentation (e.g., neutron source term information, neutron survey results, and 

the potential for neutron exposures). 

If the above condition is met, dose reconstructors should include appropriate explanatory language in 

the dose reconstruction (DR) report. This should include a discussion in the DR report of the 

available information regarding work locations and the rationale for the conclusion that neutron doses 

could not have exceeded incidental levels.

7.0

All information requiring identification was addressed via references integrated into the reference 

section of this document.

ATTRIBUTIONS AND ANNOTATIONS

REFERENCES

NIOSH (National Institute for Occupational Safety and Health), 2007, External Dose Reconstruction 

Implementation Guideline, OCAS-IG-001, Rev. 3, Office of Compensation Analysis and 

Support, Cincinnati, Ohio, November 21.