Bounding Intakes of Exotic Radionuclides at Los Alamos National 

Laboratory (ORAUT- RPRT-101)

LaVon Rutherford, CHP

Health Science Administrator

LANL Work Group Meeting

March 23, 2022

National Institute for Occupational Safety and Health
Presentation Overview

■ Background

■ Report Overview

■ Summary and Conclusions
Background

 As a part of the evaluation of SEC-0109, NIOSH concluded dose 

reconstruction was not feasible for all employees at LANL from 

1976-1995 based on the inability to bound unmonitored exposures 

to exotic alpha emitters, fission products, and activation products

 NIOSH found that dose reconstruction is likely feasible starting in 

1996 with implementation of 10 CFR 835

 November 2018 work group meeting SCA indicated they find no

substantiation for NIOSH’s belief regarding exotic radionuclides; 100 

mrem/year CEDE is bounding for primary radionuclides
Background cont.

 After the work group meeting in November 2018, NIOSH/ORAUT 

had many discussions on a path forward for addressing 

MFAP/Exotics

 NIOSH approach

– Identify radionuclides of concern

– Determine air concentration required to get 100 mrem CEDE

– Identify areas where the potential for exposure MFAP/Exotics

– Capture air sample data from these areas

– From those areas identify areas of greatest concern

– Compare actual air concentrations to those required to get 100 mrem CEDE 
Report Overview
Report Overview cont.

 The report addresses the issue of bounding dose for exotic 

radionuclides for LANL workers from 1996 through 2005 using 

surface contamination survey data, air monitoring data, and 

personal contamination monitoring to comply with 10 C.F.R. 835

 Exotic radionuclides includes short-lived activation and spallation 

products from Los Alamos Neutron Science Center (LANSCE; TA-53) 

and mixed fission products in TA-3 and TA-48

 The report also addresses heavy elements 227Ac, 237Np, 241Am, 

244Cm, and Thorium
Workplace Monitoring

 Workplace monitoring was used by LANL Health Physics to ascertain 

the effectiveness of workplace controls and compliance with 10 

C.F.R. 835

 Sitewide procedures addressing various aspects of radiological 

protection

 Area –specific monitoring instructions which included survey 

locations and frequencies

 In addition to routine sampling, LANL used continuous air monitors 

with alarm capabilities
Workplace Monitoring cont.

 A Hazard Index (HI) of less than 1 indicated a low hazard potential 

from airborne radioactivity and no air monitoring was prescribed

 A HI of 1 to 100 indicated an increased potential for airborne 

radioactivity and general air monitoring was prescribed

 A HI of 2 corresponds to 2% of an ALI which equates to 100 mrem 

CEDE

 In addition to routine/general air sampling, LANL used continuous 

air monitors with alarm capabilities
Worker Self-monitoring

 Workers were required to frisk when exiting High Contamination 

Areas, Airborne Radioactivity Areas, Contamination Areas, Buffer 

Areas, and Controlled areas

 LANL maintained and operated a large inventory of portal monitors 

consisting of Personal Contamination Monitors (PCM) and Hand and 

Foot monitors (HFM)

– NIOSH found examples of personnel alarming the portal 

monitors and the actions taken
Contamination Surveys and Airborne Monitoring Data

 To evaluate the effectiveness of the LANL radiological control 

program, we analyzed contamination survey and air monitoring 

data

 Routine smears and air sampling surveys were selected from TA-3,

TA-48, and TA-53

– These TAs were selected because of known work with exotics 

during the 1996 to 2005 period

 Background information taken from the smear and air survey data 

included date, TA, bldg. number, survey frequency, number of 

results 
Contamination Surveys and Airborne Monitoring Data 

cont.

 Data collected from the smear surveys included results exceeding:

– 20 dpm/100 cm2 alpha (LANL action limit)

– 1000 dpm/100 cm2 Beta (LANL action limit)

• The LANL action limits are the 10 C.F.R. 835 Contamination 

Control Limit

 ORAUT derived limits associated with 100 mrem CED

– 400 dpm/100 cm2 alpha (ORAUT derived upper limit)

– 3,200,000 dpm/100 cm2 Beta (ORAUT derived upper limit)
Purpose

 Purpose for compiling the data

– Demonstrate the number of samples taken in these areas was 

substantial

– Determine the likelihood an individual could receive a significant 

intake

 The purpose of collecting smear data exceeding 400 dpm/100 cm2 

alpha and 3,200,000 dpm/100 cm2 beta was to assess the likelihood 

of an individual exceeding 100 mrem
Limited Data

 Previous LANL document, evaluation reports, work group meetings 

and associated papers have indicated the following radionuclides 

have been associated with limited data:

– Mixed Fission Products and Mixed Activation Products

– Americium 241 (241Am) (Separated from Plutonium)

– Thorium 232 (232Th)

– Thorium 230 (230Th)

– Protactinium 231 (231Pa)
Limited Data cont.

 Additional radionuclides associated with limited data:

– Neptunium 237 (237Np)

– Curium 244 (244Cm)

– Actinium 227 (227Ac) 
Worst Case Radionuclides

 Of these radionuclides, ORAUT evaluated which alpha and beta 

emitter would require the smallest amount of surface 

contamination to be resuspended and a worker exposed for a year 

(2000 hours) to receive 100 mrem CED for both alpha and beta

– 227Ac type F worst-case alpha emitter

– 90Sr type S worst case beta emitter (Fission Product)
Worst Case Radionuclides cont.

 Data collected from the air sample surveys included results 

exceeding

– 0.04 dpm/m3 alpha (ORAUT derived limit)

– 320 dpm/m3 beta (ORAUT derived limit)

 The purpose of collecting air data exceeding 0.04 dpm/m3 alpha and 

320 dpm/m3 beta was to assess the likelihood of an individual 

exceeding 100 mrem CED

– 227Ac type F worst-case alpha emitter

– 90Sr type S worst case beta emitter
Contamination Surveys and Airborne Monitoring 

Results

 Table 3-1 summarizes the monitoring results for all three TAs as a 

whole and individually

 Table 3-2 shows the results by year

 Tables 3-3 through 3-5 are summarized below

 A review of the data shows that over 98% of all smears and 99% of 

air monitoring data were below the lower limits for alpha

 The evaluated data does not represent a random sample or all the 

data, but the data does suggest the workplaces were well 

controlled

 The results exceeding the limits still need to be evaluated further
Table 3-3, Breakdown of Smear Survey Results above 

Lower LANL Limits

Technical Area Total Number of 

Smears

Percentage of 

Results exceeding 

lower limit

All 40,717 1.2

3 8,771 3.9

48 7,888 0.70

53 24,058 0.34
Table 3-4, Breakdown of Results Above Derived Upper 

Surface Contamination Limit (100 mrem Limit)

Technical Area Total Number of 

Smears

Percentage of 

Results exceeding 

Upper limit

All 40,717 0.04

3 8,771 0.16

48 7,888 0.03

53 24,058 0.01
Table 3-5, Air Concentrations Above Alpha and Beta 

Derived Limits (100mrem limit)

Technical Area

Total Number of 

Area Air Sample 

Results

Percentage of 

Results exceeding 

100 mrem limit

All 67,067 0.38

3 61,704 0.15

48 3214 0.45

53 2149 7.0
Technical Area 3 -Overview

 This area included small labs with bench scale operations to larger 

radiological operations of Chemistry Metallurgy Research (CMR) 

(Bldg. 29) and Sigma Complex (Bldg. 66)

 All smears with alpha plus beta results were from Radiological 

Buffer Areas (RBA) or Contamination Areas (CA)

 Surface contamination was not found in the same location for over 

two consecutive surveys
Technical Area 3 - Contamination Surveys

 There were 28 smeared spots that exceeded the derived upper limit 

for alpha 400 dpm/100cm2

 No spot exceeded the derived upper beta limit 3,200,000 

dpm/100cm2

 17 of the 28 smeared spots were found in the Sigma Complex area 

where uranium was the radionuclide of interest

 The other 11 smears exceeding the upper derived limit were found 

in CMR where actinides were primary source of concern
Technical Area 3 – Contamination Surveys cont.

 Surface contamination smears were below the upper derived limit 

99.87% of the time

 Surveyed spots with readings above the lower LANL surface 

contamination limit were posted and/or cleaned and resurveyed

 For this TA, considering the minimal number of surface 

contamination samples above any limit and the minimal amount of 

time potentially exposed, routine workers would not be exposed to 

surface contamination levels for a year to exceed 100 mrem CED
Technical Area 3 – Airborne Results

 Airborne contamination results exceeding an alpha or beta limit 

were found on 119 sets of results for TA-3

– Sets are a grouping of airborne results from a specific location 

• Ex. On 1/26/00 In TA-3 Wing 5 there were 67 results and 

only 1 exceeded the limit

 All were for alpha results exceeding 0.04 dpm/m3

 In all, 179 individual air monitoring results exceeded 0.04 dpm/m3 

 The set of individual air monitoring results that exceeded limits is 

0.15% of the total air monitoring 
Technical Area 48 - Overview

 TA-48 is known as the Radiochemistry site supporting research and 

development in nuclear and radiochemistry

 Radiochemistry 1 (RC-1) was the only bldg. of radiological concern

 RC-1 activities included small scale radiochemistry, chemical 

research of high alpha activity in the alpha facility, sample counting 

room, small-scale production of medical radioisotopes

 The radionuclides used in these locations primarily included 

actinides and mixed fission and activation products (MFAP)
Technical Area 48 – Contamination Surveys

 Surface contamination smears exceeding either the lower alpha or 

beta contamination limit were found in 56 surveys, all in RC-1

– All smears exceeding the lower LANL Surface Contamination 

limit were found in an RBA or CA

 From the 56 surveys (7888 smears) , alpha contamination exceeding 

the lower LANL limit was found on 57 smears and beta 

contamination on 54 smears

 Individual smears exceeding the lower LANL limit were .7% of the 

total number of smears
Technical Area 48 - Contamination Surveys cont.

 As for the derived upper contamination limits

– No smears exceeded the upper beta limit 

– There were four smears that exceeded the upper alpha limit

 Of the total number of smears 99.9 % were at or below the derived 

upper limit
Technical Area 48 – Airborne Results

 Airborne contamination results exceeding a derived limit were 

found on 10 sets of airborne results for TA-48

 All were from RC-1

 Twenty-nine individual air monitoring results exceeded the derived 

alpha limit 

 NO beta results exceeded the derived limit

 Of the total monitoring results available 0.45% exceeded a limit
Technical Area 53 - Overview

 TA-53 housed the LANSCE 

 During the period of evaluation, TA-53 had approximately 400 

bldgs. and other structures and had about 800 personnel

 There were many controls established to protect workers including 

shielding, fencing, access controls, sweep procedures, beam shutoff 

mechanisms, monitoring devices, dosimetry, posted safety 

information, training, other administrative controls and emergency 

response mechanisms.
Technical Area 53 – Contamination Surveys

 The radionuclides of interest in this area were primarily actinides 

and MAPs

 Surface contamination exceeding either lower LANL limit was found 

on 46 surveys

 All smeared locations were in areas that LANL monitored for 

external exposures and intakes

 From the 46 surveys (24,058 smears), alpha contamination above 

the lower LANL limit was found on 107 smeared spots and beta 

contamination on 59 smeared spots
Technical Area 53 cont.

 The set of individual smears exceeding the lower LANL surface 

contamination limit is 0.34% of the total smears available

 Considering the derived upper limit, ORAUT found three smeared 

spots exceeding the alpha limit and no smeared spots exceeding 

the beta limit

– One spot in experimental area in MPF-3M and the other two in 

the beam target area

 This equates to 99.9% of all the smeared spots were at or below the 

derived upper limit
Technical Area 53 – Air monitoring Results

 For air monitoring samples analyzed for gross alpha and beta 

contamination, 286 individual air monitoring results exceeded the 

derived alpha limit and 14 exceeded the derived beta limit

 The set of air monitoring results that exceeded the alpha and beta 

limits is about 7% of the total air monitoring results

 Air monitoring results represent sampling at the target area, along 

the beam line, and at the beam service area and ancillary support 

facilities

 A majority of the results exceeding the limit were found in 

Experimental Area A
Technical Area Summary

 While the analysis included limited contamination survey and air 

monitoring data for three TAs, results of the smear and air 

monitoring data demonstrate that LANL effectively controlled 

radioactive contamination

 Radionuclides of interest for the period of evaluation were primarily 

actinides (uranium, plutonium, and americium) in TA-3 and TA-48 

but included activation and fission products. Spallation activation 

products as well as alpha-emitters including plutonium were of 

primary interest in TA-53
Summary and Conclusions
List of Summary and Conclusions

 In the report, the LANL radiological control program is discussed

and demonstrates that contamination was well controlled in TA-3, 

TA-48, and TA-53

 Data shows LANL controlled routine contamination that could lead 

to doses greater than 100 mrem

 The LANL Radiological program included the use of portal monitors 

to identify and remediate workplace contamination

 They required frisking upon exiting CAs, HCAs, ARAs, and RBAs

– Examples of PCM alarms and responses
List of Summary and Conclusions cont.

 The weight of the evidence clearly indicates that workers doses to 

unmonitored exotic radionuclides would not likely exceed 100 

mrem

 Doses for workers monitored by bioassay can be bounded using 

bioassay results.

 Doses to the unmonitored worker are bounded at 100 mrem
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.