Draft 

Review of Data Used by NIOSH in Support of OCAS-RPT-001 for Assigning 

NP Ratios in Behalf of the Hanford Site Single Pass Reactors 

Contract No. 200-2004-03805 

Prepared by 

U. Hans Behling, Ph.D. 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, VA 22182 

January 2009 

 Disclaimer 

This document is made available in accordance with the unanimous desire of the Advisory Board on 

Radiation and Worker Health (ABRWH) to maintain all possible openness in its deliberations. However, 

the ABRWH and its contractor, SC&A, caution the reader that at the time of its release, this report is predecisional and has not been reviewed by the Board for factual accuracy or applicability within the 

requirements of 42 CFR 82. This implies that once reviewed by the ABRWH, the Board’s position may 

differ from the report’s conclusions. Thus, the reader should be cautioned that this report is for 

information only and that premature interpretations regarding its conclusions are unwarranted.
Draft White Paper – Hanford NP Ratios 1 SC&A – January 2, 2008 

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. 

RELEVANT BACKGROUND INFORMATION 

In June 2008, NIOSH issued OCAS-RPT-001 – A Bounding Estimate of Neutron Dose Based on 

Measured Photon Dose around Single Pass Reactors at the Hanford Site. 

In October 2008, SC&A submitted its evaluation of OCAS-RPT-001 as part of the Hanford SEC 

Evaluation Review under Task Order 5. As stated in Section 5.0 of our report, SC&A concluded 

“. . . that the approach taken by NIOSH for amending neutron-to-photon (NP) ratios in behalf of 

Hanford’s single pass reactors is technically sound.” 

However, this conclusion was based on limited information and was, therefore, deemed 

conditional. As part of our conclusion (on page 9 of the report), SC&A raised the two following 

issues/concerns: 

(1) Selection of Survey Data. From among 238 boxes of available survey data, NIOSH 

requested 83 boxes, received 81 boxes, and found that 64 boxes contained survey data for 

the Hanford 100 Area production reactors. Of the 64 boxes, 57 boxes contained survey 

data that met the selection criteria for paired neutron and photon measurements. 

The initial request for 83 boxes from a pool of 238 boxes represents a statistically 

sound sample set. At this time, however, OCAS-RPT-001 provides no information 

regarding the process by which the 83 boxes were identified/selected. 

(2) Selection of Paired Measurements. NIOSH’s selection of 5,773 paired measurements 

provides a reasonable distribution of data in behalf of (1) individual reactors, (2) years of 

operation, and (3) facility location. (Note, as part of this review, however, SC&A has 

not been provided the raw data that defines the 5,773 paired measurements.) 

In response to the above-cited concerns, NIOSH, on December 19, 2008, provided Dr. Melius 

and members of the Hanford Work Group with the “. . . supporting data file . . . used in the 

preparation of the report OCAS-RPT-001.” 

The data file consists of an Excel® spreadsheet that represents data in behalf of 5,773 paired 

neutron and photon measurements that NIOSH had gleaned from survey records contained in the 

aforementioned 57 DOE file boxes. (Important to note here is that the supporting data file does 

not contain original records, but represents collated and transcribed data entered into an 

Excel® spreadsheet from original survey reports.) 

Provided herein as Exhibit 1 are salient data (Columns H through V from the Excel® 

spreadsheet) for the first 271 paired NP survey measurements. Presented below are preliminary 

comments and questions regarding the data file that makes reference to Exhibit 1. 
Draft White Paper – Hanford NP Ratios 2 SC&A – January 2, 2008 

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. 

PRELIMINARY COMMENTS AND THE NEED FOR ADDITIONAL INFORMATION 

After a cursory inspection of the 5,773 paired NP data points, SC&A has the following 

comments and requests for information/data clarification. 

 Comments: 

 Columns P and Q are identified as “neutron” and “photon,” respectively, but do not 

identify the unit(s) of measurement. However, based on Columns T, U, and V, which 

correspond to SN (or slow neutrons), IN (or intermediate neutrons), and FN (or fast 

neutrons), respectively, the metric for “neutron” is in the unit of “mrem.” 

 Questions: 

(1) Is the metric for Columns P and Q a dose rate for both neutrons and photons that 

is normalized in the units of mrem/hour? 

(2) How were the original neutron survey measurements recorded? Were they 

recorded as neutron flux (i.e., η/cm2 sec) or in neutron flux dose equivalent 

(i.e., mrem/hr)? 

(3) If either AEC/DOE or NIOSH converted neutron flux to dose equivalent values, 

what were the assumed quality factors for neutrons? 

 Comments: 

 Column M in Exhibit 1 identifies the metric “PWR.” SC&A assumes that “PWR” 

identifies the power level of the single pass production reactor at the time of the NP 

survey. 

For many paired data entries throughout the 5,773 paired measurements, this entry is 

blank. For example, Exhibit 1 shows entries 2 through 84 as blanks 

In addition, it is assumed that the reactor power level directly and proportionately affects 

the neutron flux, but affects the photon dose rate in a more complex way (in addition to 

Rx power levels, the duration of reactor operation and build-up of fission and activation 

products is another critical variable that affects photon levels). For example, entries #271 

and #272 identifies two datasets at the identical location and time for the 105 F reactor. 

While paired measurements for entry #271 identify a NP ratio of 0.0717, entry #272 

shows the identical photon dose rate, but a 13-fold higher neutron dose rate, which 

proportionately raises the NP ratio to 0.9383. This difference is likely the result of a 

transient change of Rx power level. 
Draft White Paper – Hanford NP Ratios 3 SC&A – January 2, 2008 

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. 

 Questions: 

(1) What assumptions should be made for paired measurements that do not identify 

the Rx power level? Should these values be excluded? 

(2) Were surveys conducted on a fixed routine schedule during reactor operations, or 

was the timing of surveys dictated by other variables that included or affected the 

reactor power level? For example, surveys that coincide with pulling targets at 

reduced power levels would bias NP ratios toward a lower value. In the absence 

of assigning time-weighted values to NP ratios, paired NP measurements may 

have to be restricted to those time periods when the reactor was operating at its 

normal production power level. 

 Comments: 

 As noted in OCAS-RPT-001, surveys involving neutron measurements at different 

reactors and over time involved several types of instruments, which included single and 

double moderated BF3 detectors and the Cheng and Eng neutron detector. 

Information regarding instrumentation used for photon dose rate measurements is not

described in OCAS-RPT-001. 

Reported dose rates for neutrons included dose rates as low 0.1 mrem/hour. Dose rates 

for photons were frequently reported at 1 mrem/hour. 

 Questions: 

(1) For neutron and photon survey instruments, what were the lower limits for 

detection of dose rates? For example, entries #75 through #78 cite 10 mrem/hour 

as a minimum reportable gamma dose; however, dose rates as low as 

1 mrem/hour are frequently cited elsewhere. 

(2) What is the uncertainty of dose rate measurements for these instruments at the 

low end of the detection level? For example, the uncertainty of BF3 neutron flux 

detectors is driven by counting statistics, energy distribution, etc. 

 Currently, OCAS-RPT-001 provides NP ratios along with geometric standard deviation 

value that do not include the uncertainty of the individual measurements. 

Before SC&A conducts a more comprehensive and detailed analysis of the 5,773 paired survey 

measurements, we are requesting the Hanford Work Group to arrange a forum for the purpose of 

answering these and other questions. 
EXHIBIT 1: EXCERPTS FROM EXCEL® SPREADSHEET DATA USED TO DERIVE 

NP RATIOS FOR HANFORD SINGLE PASS REACTORS 

Draft White Paper – Hanford NP Ratios 4 SC&A – January 2, 2008 

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. 
Exhibit 1 (Continued) 

Draft White Paper – Hanford NP Ratios 5 SC&A – January 2, 2008 

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. 
Exhibit 1 (Continued) 

Draft White Paper – Hanford NP Ratios 6 SC&A – January 2, 2008 

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.