Memo – KCP Matrix Issues – Neutron Dose 1 SC&A – April 21, 2015 

NOTICE: This memo 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 

DATE: April 21, 2015

TO: KCP Work Group 

FROM: Ron Buchanan, SC&A

SUBJECT: SC&A’s Evaluation and Closure of KCP SEC Matrix Issues 11 and 12; Neutron 

Dose

In January 2015, NIOSH provided a response to the Kansas City Plant (KCP) Special Exposure 

Cohort (SEC) neutron dose issue concerning the use of the neutron-to-photon ratio (n/p) method 

by stating at the end of Matrix Issue #11, “After further evaluation, OTIB-24 Estimation of 

Neutron Dose Rates from Alpha-Neutron Reactions in Uranium and Thorium Compounds, is not 

appropriate and should not be used to estimate neutron dose at KCP.” Instead, NIOSH has 

addressed (at the end of Issue 12) the neutron dose issue by applying an annual neutron dose to 

KCP workers that may have been exposed to neutrons as follows: 

NIOSH status for January 20, 2015 WG: As indicated in the previously 

submitted response to Issues Matrix #11, the neutron sources at the KCP appear 

to be confined to Ra-Be/Pu-Be sources and neutron generators. The sources 

produce an average neutron energy of 3.6 MeV (Ra-Be) and 4.2–5.0 MeV (Pu-Be) 

whereas the neutron generators produced a neutron energy of 14.7 MeV. 

Typically, NTA film has a neutron energy-response threshold of 0.5 MeV and 

would be able to detect the neutrons emitted by KCP sources/generators. 

In 1993, an appraisal of Radiation Protection was performed at KCP (SRDB 

111275) to evaluate their compliance with DOE Order 5480.11, DOE RadCon 

Manual, and applicable occupational radiation protection standards and 

practices. The appraisal found that users of radiation generating equipment were 

assigned neutron dosimeters, but there had been no measurable neutron doses in 

three years or on an area dosimeter that had been in a worst-case location for 

three months. The appraisal indicates that removal of the neutron badges 

appears to be justified based on the historical information that less than 0.100 

rem would be received. 

The sources of neutrons at KCP are essentially the same throughout KCP 

operations and annual doses are likely less than 0.100 rem (the dosimetry data 

reviewed from the site confirms that doses greater than 0.100 rem are very 

infrequent). Since the predominant neutron energy is well above 0.5 MeV, a 

correction factor (which is applied at other sites with lower energy neutrons) is 

not needed. The dosimetry records from the site were reviewed and they 

consisted of 13,745 entries, of which 2,188 had neutron monitoring (35 with 

recorded positive neutron dose, remaining all had zero recorded neutron dose). 

Three dosimetry records were greater than 0.100 rem (0.200 rem in 1966, 0.180 
Memo – KCP Matrix Issues – Neutron Dose 2 SC&A – April 21, 2015

NOTICE: This memo 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.

rem in 1988, 0.140 rem in 1970). The 95th percentile dose of the dosimetry 

records with recorded neutron dose (limited set of 35 records) results in a value 

of 0.154 rem. To account for unmonitored neutron dose that may have been 

received, a bounding assignment of 0.154 rem/year neutron could be assigned for 

unmonitored workers who worked with neutron sources or neutron-generating 

devices as indicated in the CATI or other available DOL/DOE information. This 

dose should be assigned using the 2–20 MeV energy range. This approach is an 

overestimate for unmonitored employees and should be assigned as a constant 

distribution.

SC&A evaluated the document containing the neutron exposure records at the KCP (Worker 

Exposure History on the K-drive) and NIOSH’s January 2015 response and found:

 There were 34 records of positive annual neutron dose (1966–1996), and over 2,000 

records of annual neutron dose with zero entries (1965–2010)

 The 34 positive annual neutron recorded doses range from 0.003 rem to 0.200 rem, with 

all but three readings less than 0.100 rem.

 The top three annual neutron dose readings were 0.140 rem (1970), 0.180 rem (1988), 

and 0.200 rem (1966).

 The 95th percentile neutron dose was approximately 0.154 rem/year.

In view of this analysis, SC&A found that NIOSH’s use of a neutron dose of 0.154 rem/year for 

KCP workers that may have been exposed to neutrons is reasonable and claimant favorable. 

SC&A considers the present KCP SEC neutron dose-related issues addressed and the issues have 

been closed by the Advisory Board.