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with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Air Sample Data at Area IV SSFL in 

Support of SEC-00235

White Paper

National Institute for Occupational

Safety and Health

November 6, 2018

Lara Hughes 

Division of Compensation Analysis and Support
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

BACKGROUND

In May 2017, NIOSH issued an evaluation report for petition SEC-00235 for Area IV of the 

Santa Susana Field Laboratory (SSFL) for the period of August 1, 1991 to June 30, 1993 

(NIOSH, 2017). SEC-00235 was qualified for evaluation because of compromised bioassay 

samples from vendor Controls for Environmental Pollution (CEP) during this time period. 

NIOSH does not use the bioassay results from CEP because they were implicated in data 

falsification at another site (not SSFL affiliated). NIOSH found that, despite the lack of roughly 

two years’ worth of in-vitro bioassay data, there was no dose reconstruction infeasibility for the 

evaluated period and did not recommend that a class be added to the SEC. During the work 

group discussion on Area IV SSFL pertaining to SEC-00235 on December 4, 2017, NIOSH was 

tasked by the work group to provide more information on the available air sample data for the 

period where in-vitro bioassay data cannot be used (Transcript, 2017). Below is a summary of 

the operational highlights and the available air sample data for the 1991-1993 period at Area IV 

SSFL. A period in 1993, where several elevated general air samples were observed in the Hot 

Lab, is analyzed in greater detail.

RADIATION CONCERNS DURING THE REMEDIATION PERIOD (AFTER 1988)

The EEOICPA covered period for Area IV SSFL is 1955-1988, with a remediation period from 

1989 through present. By the end of 1988, all nuclear reactors and their fuel had been removed 

from Area IV SSFL, and the facilities were undergoing decontamination and decommissioning 

(D&D). The main facilities that could produce a notable airborne hazard were the Rockwell 

International Hot Laboratory (Hot Lab), the SNAP reactor facility (T059) and the Radioactive 

Material Disposal Facility (RMDF) (Quarterly Reviews, 1991-1993; Documented 

Communication, 2017a, 2017b). The RMDF was not in D&D mode, but an active facility. The 

radiation hazard at any given facility could vary significantly by the specific activity that was 

going on at any given time─meaning that it was not necessarily consistent over the course of the 

1991-1993 period. There are monthly and quarterly activity and surveillance reports available 

that summarize the operations at the respective facilities (see “quarterly review” and “activity 

report” labeled documents in the Reference section). A brief summary is provided below for 

each of these three facilities (Hot Lab, RMDF, SNAP facility). 

Based on the evaluation by Area IV SSFL Health Physicists (Moore, 1992), the remaining 

radionuclides of concern at Area IV in 1992 were Cs-137, Sr-90, Co-60 and Pu-239. Only fission 

products Cs-137 and Sr-90 were indicated to be present in sufficient quantity to be readily 

dispersed for inhalation by workers and Cs-137 was considered the most important radionuclide 

of concern during this period in operational history. It had been observed to be present along 

with Sr-90. The remaining Co-60 was largely contained in activated structural steel of reactor 

facilities and did not readily become airborne during demolition, except during cutting 

operations. The remaining Pu-239 was considered low level residual surface contamination and 

residual in remaining liquid waste handling systems. Pu-239 presented the biggest challenge in 

measurement and interpretation and was a focus of personal air sampling as is Sr-90. Cs-137 and 

Co-60 are gamma emitters and can be detected at relatively small fractions of permissible body 

burdens, using whole body counting. General work area and worker breathing zone air sampling 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

in areas where unencapsulated radioactive materials were handled were the primary indicators of 

potential radionuclide intakes by workers (Moore, 1992; Documented Communication, 2017a, 

2017b) 

AIR SAMPLING PRIMER

Moore (1992) and Tuttle and Kittinger (1996) are references with a good description of the air 

sampling program at the SSFL sites in the 1990s. Air sampling methods consisted of both 

general area (GA) and breathing zone samples (BZ). 

The GA and BZ results were compared to the maximum permitted air activity concentration 

(MPC). The radionuclides of concern to the air sample program at SSFL were the beta emitter 

Sr-90 and the alpha emitter Pu-239. The MPC values used are 1E-09 μCi/mL for Sr-90 and 

2E-12 μCi/mL for Pu-239 (Quarterly Reviews, 1991-1993). Based on the guidelines stated in 

the quarterly reports, any air samples above 0.25 times the MPCs were analyzed for licensed 

materials (as opposed to naturally occurring radon and thoron progeny). For BZ air 

concentrations, the site used a limit of 2000 MPC-hours per calendar year (or 40 MPC-hrs/week 

for 50 weeks a year). The SSFL also applied a derived limit of 520 MPC-hrs per calendar quarter 

(Quarterly Reviews, 1991-1993). The available filtered full face respirators provided a protection 

factor of 50. Air-line respirators (the type most commonly used) provide a protection factor of 

2000. The respiratory program at SSFL was evaluated annually by SSFL management (Quarterly 

Reviews, 1991-1993, PDF p. 406). Around 1992, the terminology from 10 CFR 835 was 

implemented and MPC-hours became DAC-hours. The Annual Limit of Intake (ALI) and/or 

Derived Air Concentration (DAC) values were used to limit radiation exposure from airborne 

radionuclides, based on 10 CFR 835. The ALI or DAC for a single radionuclide is the maximum 

intake in a year or the average concentration for a working year such that a person would not 

exceed a committed effective dose equivalent limit of 0.05 Sv (5 Rem) or a committed dose 

equivalent limit to any organ or tissue of 0.5 Sv (50 Rem). The values for MPC and DAC-hours 

used as the limit for GA and BZ concentration remained the same as before.

During the 1988-1992 period, air sampling was the primary assessment method for worker 

exposure, as controlling exposure via MPC-hour assessment was the regulatory requirement. 

Bioassay sampling was done as a backup to the air sampling program (Documented 

Communication, 2017b). Moore (1992) indicated that BZ air sampling is the preferred method to 

control for Pu-239 intakes, because it is difficult to measure an intake at regulatory level in the 

body (i.e., via bioassay). 

General air samples were collected in fixed locations and were intended to reflect the longer term 

time-averaged concentrations in the workplace. At Area IV SSFL, GA samples were generally 

averaged over a week. Since all residual radionuclides had fairly long half-lives, radioactive 

decay was not a factor in evaluating time averaged general air samples. Continuous air sampling 

using fixed position air samplers used Gelman Type A/B glass fiber filters. The air samplers 

were operated continuously, with each filter collecting particulate aerosols for about 168 hours 

per week, or normally about 2184 hours per quarter. The available quarterly reports show 

averages for 13 weekly samples for each sampling location. The air flow typically is calibrated to 
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28.32 L/min (Quarterly Review, 1990a; Quarterly Review, 1990b, 1990c). The GA sample filters 

were counted in a gas flow proportional counter system for alpha and beta emitters and were 

allowed 72-96 hours of decay time to ensure the removal of radon daughter products before 

counting (Tuttle and Kittinger, 1996). However, the quarterly review reports state that the 

ambient air concentrations include radon and thoron daughter products (Quarterly Reviews, 

1991-1993). There were 28 fixed sample locations in the Hot Lab, 7 fixed sample locations in the 

RMDF and no fixed sample locations in the SNAP facility (Quarterly Reviews, 1991-1993). 

Breathing zone (BZ) air was measured in localized areas for very specific tasks that had a high 

probability of producing measurable quantities of radioactive aerosols. The sample collector was 

required to be placed close to the worker’s nose or respirator inlet valve. This was thought to 

produce a better measure of worker exposure, since the BZ samplers were carried on the person. 

Each worker carrying a BZ sampler was equipped with a battery powered sampling pump and an 

air sample filter holder containing a Gelman Type A/E glass fiber particulate aerosol filter. The 

filter holder was mounted on the worker’s outer PPE and connected to an air pump via a flexible 

hose. The airflow was ~ 3 L/min and is turned on and off by the worker when entering and 

leaving the work area. Actual worker internal exposures were controlled by the type of 

respiratory protection used, if any (Quarterly Review, 1990a). Breathing zone samples were 

reported by the worker. Some workers had multiple entries during the reporting period. Samples 

were averaged over the reporting period (Moore, 1992; Quarterly Reviews, 1991-1993). 

OPERATIONS SUMMARY FOR HOT LAB, SNAP FACILITY AND RMDF

The activity descriptions below were selected from quarterly reviews and weekly activity reports 

(Activity Reports, 1991, 1992, 1993), based on their potential impact to worker radiation 

exposure.

SNAP Reactor Building (Building T059)

Quarterly reviews are available for 1991 (4 quarters) (Quarterly Reviews, 1991-1993) and 

weekly activity summaries are available for 1991-1993 (Activity Reports, 1991, 1992, 1993). 

The SNAP reactor was designed to power satellites in space. Several reactors of this type were 

operated at SSFL from 1956 to 1969. After the end of operations, the facilities have been 

gradually decontaminated and structures removed. This process was on-going during the 1991-

1993 period. The facility is regulated by DOE (Quarterly Reviews, 1991-1993). The main 

remaining source term in Building 59 was Co-60 (Documented Communication, 2017a; Activity 

Reports, 1992). 

During the 1991-1993 period, contaminated piping and structural material inside the SNAP 

reactor vessel pit were removed, which potentially resulted in high contact exposure rates of 5-8 

mrem/hr. Irradiated structural steel and irradiated high density concrete were handled (such as 

shielding blocks). Some of this process involved the use of jackhammers. Sections from the 

reactor building structure were sent to the RMDF, where they were decontaminated and reduced 

in size before being placed into interim storage for eventual shipment off-site. A backlog of 

packaging material caused some interim storage of material in the high bay, which lead to 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

observed elevated dose rates. Deficiencies outlined in the DOE Tiger Team report were 

addressed (rewiring of basement). The HEPA filtration system had routine repair and 

maintenance. Some groundwater seepage into the test cell area was observed. Airborne 

radionuclide contamination was observed during operations, such as the removal of old NaK 

lines. Workers wore breathing zone air sample equipment and respirators during critical 

operations. This operation (removal of NaK lines) caused the highest assigned exposures 

(accounting for respiratory protection), which ranged from 0.02 to 0.22 DAC-hrs. The facility 

was shut down for several weeks in 1992 to acquire additional tools needed for D&D operations 

(a torch power supply). Test cell liners were cut and torched. A spreadsheet was developed, 

estimating the amount of residual radioactivity still in place at the SNAP facility, and it was ~7 

Ci in 1992 (Quarterly Reviews, 1991-1993). 

Rockwell International Hot Laboratory (Hot Lab, RIHL, Building 20)

The Hot Lab was a four-cell facility for the remote manipulation of mega-curie quantities of 

radioactive materials. The facility started operations in 1959. Operations with high level 

materials ended in 1987, when the facility was transitioned into D&D. The facility is regulated 

by NRC. Quarterly surveillance reports are available from first quarter of 1991 to the fourth 

quarter of 1993 (12 quarterly reports). The first quarter of 1990 is an incomplete report 

(Quarterly Review, 1990b, 1990c, 1990d, 1990e; Quarterly Reviews, 1991-1993). Annual 

reports detailing the Hot Lab decommissioning activities are also available (Annual Report, 

1992, 1993, 1994). Annual Report (1993) has photographs showing workers wearing BZ 

equipment and respirators during operations (photographs are not of good quality and were 

therefore not reproduced here). 

During the 1990-1993 period, areas of contamination in the hot cells and the decontamination 

room were cleaned by sandblasting and components were reduced in size and removed. The 

removal of the hot cell liner was a time-consuming and tedious task that involved cutting the 

liner with oxy-acetylene torches to smaller pieces to remove them from the substructure (Annual 

Report, 1992). Other power tools, such as jackhammers, were used for size reduction of 

structural elements. The main objective was the removal of the contaminated fixtures from noncontaminated substructures. The HEPA filtration system was routinely maintained (filter 

replacement, duct maintenance) and repaired where needed. Structural components were 

removed and sent to the RMDF for size reduction, packaging and interim storage and eventually 

off-site disposal. Some areas required contamination tents to be installed around the area being 

dismantled. The removal of drain lines was an operation that had the potential to produce 

significant external dose rates. Alternate ventilation methods were implemented as the regular 

ventilation system had to be dismantled to get access to the drain lines. The removal of in-floor 

storage tubes began in 1993. An earthquake struck in January 1994, but no significant damage to 

SSFL structures was observed. Personnel radiation exposures for the fourth quarter of 1993 

were significantly higher than previous quarters. This was due to the removal of contaminated 

drain lines which contained high levels of activation products. Some operations took place 

outside the building, such as removal of contaminated asphalt in the holdup yard and surveying 

of metal stock that was stored outside. With the removal of the glove box in room 139, all former 
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plutonium processing equipment had been removed from the Hot Lab, except for trace amounts 

in ventilation and liquid waste processing systems. 

Incidents reported consisted of skin contamination and a case of a cut from flying debris during 

metal cutting operations. Incidents were followed up by health physics if there was a radiological 

concern. Concerns voiced by Health physics was related to a shortage of respirators, which 

caused scheduling delays. All workers requiring BZ samples also were reported wearing 

respirators. 

Breathing zone sampling was reported for 7 to 22 workers, based on their work assignments. 

Some workers had multiple entries; some workers had more than 50 entries during the reporting 

period. The reported MPC-hours account for the use of respirators by the workers. The highest 

MPC or DAC-hours assigned was 7.295 MPC hours in 1993 (of 520 allowed per quarter).

The Hot Lab reported between 31 (in 1990) and 28 (1991-1993) locations for general air 

sampling. The data is summarized in Table 1. During the first three quarters of 1993, there were 

four reported GA averages that were above the MPC levels, all for the gross beta monitor (Sr90). These elevated results are discussed below.

Radioactive Materials Disposal Facility (RMDF)

The Radioactive Materials Disposal Facility (RMDF) consisted of several buildings dedicated to 

storage, packaging and shipment of radioactive materials, and was in active use during the 1991-

1993 period. Quarterly surveillance reports are available for the years 1990 and 1991, with the 

exception of the third quarter of 1990 (Quarterly Reviews, 1991-1993; Quarterly Review,

1990a). Activity Reports for Radiation Protection and Health Physics Services are available for 

January-December, 1991-1993 respectively (Activity Reports, 1991, 1992, 1993). 

In this period, shipments of radioactive waste materials were made to various recipients, such as 

Hanford and University of Missouri. Liquid and solid waste materials were treated and stored or 

removed from the site. The RMDF received radioactive wastes from the Hot Lab, T059 and 

T886, as well as other smaller facilities. The boxes from T059 consisted mainly of contaminated 

concrete, and the material was shipped to Hanford for burial. The material from the Hot Lab of 

most concern was the contaminated drain lines. In addition, material from the remediation of the 

Sodium Burn Pit facility (T886) was received in the form of lightly contaminated soil. A quantity 

of depleted uranium (DU) (240 kg) was shipped from the RMDF to Los Alamos National 

Laboratory (LANL). Materials from the TRUMP-S program (DU and Np-237) were shipped to 

University of Missouri in May of 1990. The RMDF retention pond was drained, sampled and 

resurfaced. In 1991, the facility had increased shipment activity, which resulted in a reduction of 

perimeter dose rates as radioactive items were removed. In 1991, the Hot Lab Cell doors were 

placed in temporary storage. In 1993, a total of 149 boxes and 349 bags of laundry were shipped 

without incident. Other routine operations at the RMDF consisted of cleanup of localized areas 

of radioactive contamination. Routine maintenance and repairs were done on the HEPA filter 

system. Work was suspended in the decontamination room in 1991 because of vent blower 

failure. Also in 1991, operations were briefly suspended until better air sampling procedures 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

were implemented as a result of the Tiger Team report. Laundry was routinely sorted and 

prepared for shipping to the laundry vendor. 

Seven locations at the RMDF typically reported GA air samples. The highest sample was 

collected next to the fume hood in the decontamination room when handling material from the 

Hot Lab (first half of 1990). 

BZ data for up to ten workers are available from various operations, such as size reduction of 

Building 059 concrete, laundry sorting and HEPA filter handling. 

AIR DATA REPORTING AND DATA AVAILABILITY

Air data are reported in the quarterly safety review reports for the Hot Lab and for the RMDF 

and the SNAP reactor Building (T059). Not all quarterly reports are available to NIOSH for all 

three facilities. It is not clear if these reports exist and where they are located. A recent request 

for additional quarterly reports to the DOE-EM Consolidated Business Center (EMCBC) in 

Cincinnati, Ohio, where DOE records from SSFL operations were sent, has not yielded 

additional quarterly review reports. It is not known at this time if additional reports or potentially 

raw data could be located, but attempting to do so would likely require significant time and 

effort. 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure 1. Annual Maximum Averages for GA Beta Sampler at the Hot Lab Reported in Annual Reports for 

1975-1988

Annual Review of Radiological Control reports are available for the operational period from 

1975-1988 (Annual Review, 1975-1988). These reports have annual interior air sample summary 

data for the Hot Lab available. The annual maximum average air results over time are shown in 

Figure 1 for beta analysis. Even the maximum reported annual averages are below the MPC of 

1E-09 μCi/mL, except for 1985. The 1985 review does not discuss the above MPC average value 

in any detail. Generally the reported average values are in the same range as the values reported 

during the 1990-1992 period. The GA average values for 1993 have locations with elevated GA 

results for some locations. This is discussed in more detail below.

Table 1 below lists the general air data available in quarterly reports from Area IV SSFL during 

the CEP period as well as adjacent quarters. There are gaps in the completeness of the records 

during this time. However, the available summary reports are complete for the Hot Lab for 1990-

1993. 

The maximum reported values are the highest values reported in that quarter between the three 

facilities, where available. The maximum value GA in Table 1 represents a 13 week average of a 

given air sample location. The maximum BZ value represents the highest number of DAC-hrs 
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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

assigned to a worker as a result of wearing a BZ sampler over a quarter. This accounts for 

respirator protection factors assigned. 

It is a reasonable assumption that the Hot Lab would represent a bounding dose regarding 

potential airborne particulate intakes, because of its operating history and its residual levels of 

Pu-239 and elevated results observed in 1993. It also has the largest number of GA samplers and 

the largest group of workers with BZ data available. This is supported by the activity reports for 

1992, which mentioned that worker bioassay was triggered, as some BZ results from Hot Lab 

operations in the second and third quarter 1992 were detected above the MDA (Activity Reports, 

1992, PDF pp. 32, 84). This report also indicates that the site maintained the BZ data results in 

spreadsheet and data base form (dbase) (a database management system) (Activity Reports, 

1992, PDF p. 94). NIOSH does not have this data at this time. 
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Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. 

This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that 

is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 1. Air Sampling Data Summary for Area IV SSFL Before, During and After the CEP Period.

Quarter SNAP

(T059) Bz

SNAP 

(T059) GA

Hot Lab 

BZ

Hot Lab 

GA

RMDF 

BZ

RMDF 

GA

Maximum Reported Value 

BZ (DAC-hrs)

Maximum Reported Value 

GA (μCi/mL)

01/1990 Not 

Applicable

Not 

Applicable

Not 

Applicable 

(pages 

missing)

Not 

Applicable

Not 

Applicable 7 Not Applicable

Beta: 1.7E-12 (RMDF)

Alpha: 1.7E-14 (RMDF)

02/1990 Not 

Applicable

Not 

Applicable 22 workers 31 4 workers (6 entries) 7 1.78 (RIHL)

Beta: 1.1E-11 (RMDF)

Alpha: 5.8E-14 (RMDF)

03/1990 Not 

Applicable

Not 

Applicable 16 workers 31 Not Applicable

Not 

Applicable 1.14 (RIHL)

Beta: 3.8E-12 (RIHL)

Alpha: 5.0E-14 (RIHL)

04/1990 Not 

Applicable

Not 

Applicable 11 workers 28 3 workers 7 1.1 (RMDF)

Beta: 5.1E-12 (RMDF)

Alpha: 4.1 E-14 (RMDF)

01/1991 Not 

Applicable 0 Not Applicable 28 Not Applicable 7 Not Applicable

Beta: 1.0E-11 (RIHL)

Alpha: 1.0E-14 (RIHL)

02/1991 3 workers 0 

13 workers

(275 entries)

28

10 workers

(23 entries)

7 0.89 (RIHL)

Beta: 3.4 E-11 (RMDF)

Alpha: 4.0E-14 (RIHL)

03/1991a 7 workers

(32 entries)

0 

12 workers

(285 entries)

28

8 workers

(32 entries)

7 0 .396 (RIHL)

Beta: 3.4E-12 (RIHL)

Alpha: 5.0E-14 (RIHL)

04/1991

6 workers

(12 entries)

0 

10 workers

(245 entries)

28

6 workers

(20 entries)

7 0.6 (RIHL)

Beta: 1.2 E-12 (RIHL)b

Alpha: 2.2 E-14 (RMDF)b

01/1992 Not 

Applicable

Not 

Applicable

10 workers

(314 entries)

28 Not 

Applicable

Not 

Applicable 0.4 (RIHL)

Beta: 1.5E-13 (RIHL)b

Alpha: 2.0E-14 (RIHL)b

02/1992 Not 

Applicable

Not 

Applicable

11 workers

(373 entries)

28 Not 

Applicable

Not 

Applicable 0.594 (RIHL)

Beta: 3.04E-12 (RIHL)

Alpha: 1.56E-13 (RIHL)

03/1992 Not 

Applicable

Not 

Applicable

9 workers

(208 entries)

28 Not 

Applicable

Not 

Applicable 0.057 (RIHL)

Beta: 1.4E-12 (RIHL)

Alpha: 6.38E-14 (RIHL)
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This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that 

is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Quarter SNAP

(T059) Bz

SNAP 

(T059) GA

Hot Lab 

BZ

Hot Lab 

GA

RMDF 

BZ

RMDF 

GA

Maximum Reported Value 

BZ (DAC-hrs)

Maximum Reported Value 

GA (μCi/mL)

04/1992 Not 

Applicable

Not 

Applicable

15 workers

(261 entries)

28 Not 

Applicable

Not 

Applicable 1.791 (RIHL)

Beta: 1.97E-13 (RIHL)

Alpha: 8.58E-15 (RIHL)

01/1993 Not 

Applicable

Not 

Applicable

16 workers

(414 entries)

28 Not 

Applicable

Not 

Applicable 1.069 (RIHL) Beta: 9.90E+1 (RIHL)

Alpha: 2.41E-14 (RIHL)

02/1993 Not 

Applicable

Not 

Applicable

13 workers

(262 entries)

28 Not 

Applicable

Not 

Applicable 0.466 (RIHL) Beta: 4.82E+1 (RIHL)

Alpha: 3.7E-14 (RIHL)

03/1993 Not 

Applicable

Not 

Applicable

14 workers

(315 entries)

28 Not 

Applicable

Not 

Applicable 7.295 (RIHL) Beta: 8.49E+4 (RIHL)

Alpha: 5.04E-14 (RIHL)

04/1993 Not 

Applicable

Not 

Applicable

7 workers

(131 entries)

28 Not 

Applicable

Not 

Applicable 2.234 (RIHL)

Beta: 2.27E-12 (RIHL)

Alpha: 1.52E-14 (RIHL)

a. The CEP period, 03/1991-02/1993, is shaded grey.

b. These quarters reported only averages for quarter.
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 12 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Even though the highest reported samples for several quarters were for the RMDF, please note 

that none of these samples were above the MPC, and that the results for the hot lab were in the 

same overall range – with the exception of the 1993 results. 

During the first three quarters of 1993, the Hot Lab reported four significantly elevated general 

air samples in a three locations for Sr-90, as shown in Table 1. Table 2 below shows more detail 

on these elevated air samples (Quarterly Reviews, 1991-1993, PDF pp. 371, 436, 532, 538). 

Table 2. Reported Elevated GA Sample Reading for Hot Lab in 1993 for Sr-90. 

Quarter Location Minimum Reading 

(μCi/mL)

Maximum Reading 

(μCi/mL)

Average Reading 

(μCi/mL)

01/1993 Service Gallery Beta Monitor 4.00E-01 9.90E+01 3.01E+01

02/1993 Service Gallery Beta Monitor Non-detect 4.82E+01 1.25E+01

03/1993 Basement North East 3.20E-14 4.99E+04 3.84E+03

03/1993 Service Gallery North 3.79E-14 8.49E+04 6.50E+03

Table 2 indicates that elevated general air results occurred during three quarters of 1993. Of the 

28 monitored GA locations, one showed elevated beta counts for the first two quarters, and two 

locations had elevated results during the third quarter. There were no elevated results reported 

during the fourth quarter. The remaining locations of the 28 had averages below the MPC for 

these quarters. The location for the elevated averages is “Service Gallery Beta Monitor” for 

01/93 and 02/93 and “Basement North East” and “Service Gallery North” for 03/93. The 

average values reported in the quarterly report represent a 13 week average, so it is not clear for 

how long this elevated airborne contamination was recorded (Quarterly Reviews, 1991-1993). 

Activity reports were reviewed to determine the activities that could have resulted in these 

elevated GA samples. During those quarters, generally some elevated personnel exposures were 

observed (Quarterly Reviews, 1991-1993, PDF p. 517). One quarterly report mentioned a CAM 

alarm on July 20, 1993 in an area in the basement where a plasma torch was used to cut 

ventilation ducting. The worker’s BZ sampling indicated the airborne ambient concentration was 

0.21 DAC (< 0.1 DAC after accounting for a respirator factor of 50). As a consequence of this 

incident, the worker was instructed to change his procedure and the sample point was moved to a 

more appropriate location. It is likely that this incident is related to the reported elevated GA 

result for the Hot Lab basement area. A review of area TLD data for 1993 indicated some TLD 

slightly elevated results (< 2 mrem) in the hot lab basement area and the liquid waste tank area 

during the second and third quarter in 1993 (Quarterly Reviews, 1991-1993; Tuttle, 1994, PDF p.

33). One of the major tasks completed in this timeframe was the removal of contaminated drain 

lines from the hot cells. This required accessing the drain lines from the basement through 

concrete walls (Quarterly Reviews, 1991-1993; Activity Reports, 1993). It also required the 

removal of ventilation ducting and installation of alternate ventilation in the affected area. The 

drain line removal resulted in very high external dose rates from contaminated debris contained 

in the drain lines. Therefore, the source of localized high general air samples in the basement 
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 13 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

area likely was a result of this operation, especially since there were changes in the area 

ventilation setup. 

No information was found in the available records on the elevated sample in the Service Gallery 

North. The service gallery was an area running the length behind the decontamination cells 

(which were behind the hot cells) on the hot side of the facility. There were four GA samplers in 

this area, labeled “Service Gallery Alpha Monitor”, “Service Gallery Beta Monitor”, “Service 

Gallery North” and “Service Gallery South.” Two of those locations had elevated GA results but 

the other GA sampler (Service Gallery South) did not, indicating that the elevated air 

concentration was somewhat localized. The operations in that area consisted of the removal of 

drain lines in cells 3 and 4, the core drilling of through tubes and slave ports in the service 

gallery and in the decontamination rooms, and the removal of ventilation ducts in cell 4 (Activity 

Reports, 1993). Available incident reports point to work activities in the hot lab that resulted in 

an off-scale dosimeter reading (Incidents, 1990) for work in cell 3 area in September of 1993, 

and personal contamination as a result of a “contamination event” at the Hot Lab (Incident, 

1993) in August of 1993. 

During this period, workers in the Hot Lab also had BZ data available and whole body counts on 

workers were done in October 1992, April 1993, September/October 1993 and June 1994. Those 

results are available and were also included in quarterly reports. The names of the workers 

involved in the Hot Lab operations requiring BZ monitoring are available and detailed worker 

records can be accessed in the workers’ dosimetry files, which are available to NIOSH, even if 

the worker is not a claimant. Looking at the WBC results, three hot lab workers had reported 

values for Cs-137 of 2 nCi (+/- 1 nCi) during 1993. Those workers’ individual worker dosimetry 

files were reviewed (Worker dosimetry files can be found in the ABRWH review folder under 

Santa Susana). 

To further investigate the exposure potential of the Hot Lab workers in light of elevated beta 

readings, NIOSH selected five workers who were working in the Hot Lab during those quarters 

and who had indications of non-zero breathing zone MPC-hours assigned (none were close to the 

limit, though), and who also had whole body counts and urine bioassay to assess if there were 

any indication of unmonitored intakes from the Hot Lab (third and fourth quarter 1993 bioassay 

are useable due to a new bioassay vendor). The data are provided below in Tables 3 and 4. Table 

3 indicates that the highest worker was assigned less than 0.1% of the occupational intake limit 

based on their BZ data assessment.
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 14 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 3. Breathing Zone Air Sample Data for 1993 Hot Lab Operations for 5 Selected Workers.

Worker Number Quarter Number of 

Entries

Maximum BZ for 

Sr-90 (μCi/mL)

DAC-hrs 

Assigneda

1 [redacted] 3/93 64 1.2E-08 1.08

2 [redacted] 1/93 43 2.60E-09 0.165

3 [redacted] 1/93 35 4.6E-09 0.032

4 [redacted] 1/93 33 1.9E-9 0.036

5 [redacted] 1/93 14 2.6E-9 0.162

a. DAC-hrs assigned for Sr-90 from this entire quarter of BZ sampling accounting for respiratory 

protection (the limit is 520 DAC-hrs)

Table 4. Urine and Whole Body Count Data for 5 Selected Hot Lab Workers. 

Worker 

Number WBC Date WBC Result (nCi)

Urine Sample 

Date after CEP

Urine Bioassay 

Analytes Urine Result

1 [redacted] [redacted]1993

[redacted]1993

0

0 

[redacted]1993

[redacted]1994

GA, U, MFP, 

GB “less than”

2 [redacted]

[redacted]1993

[redacted]1993

[redacted]1994

2 (± 1) Cs-137

2 (± 1) Cs-137

2 (± 1) Cs-137

[redacted]1993

[redacted]1993

[redacted]1993

GA, GB, U, “less than”

3 [redacted]

[redacted]1993

[redacted]1993

[redacted]1994

2 (± 1) Cs-137

0 

0 

[redacted]1993

[redacted]1994 GA, GB, U, GB “less than”

4 [redacted]

[redacted]1993

[redacted]1993

[redacted]1994

2 (± 1) Cs-137

0 

0 

[redacted]1994 GA, GB GB: 7.60 (± 4.3) 

pCi/L

5 [redacted] [redacted]1993

[redacted]1993

0

0 

[redacted]1993

[redacted]1994 GA, GB, H-3 “less than”

From examination of Table 4, it can be seen that there is no seemingly clear correlation between 

the GA data, the BZ data and the WBC and the bioassay results from August 1993 and later. The 

positive whole body count results are for Cs-137, which is a fission product and is often present 

along with Sr-90. Since work was done in an area of elevated airborne contamination, it is 

possible that some workers received some intakes. There is no indication that the radiation dose 

could not be bounded for these workers (or their coworkers) using the available data, be it 

available air, WBC or urine bioassay data. Whereas it seems that all workers who were involved 

in the D&D operations were monitored by BZ and WBC, it is also possible to assign potentially 

missed dose using the available coworker models for SSFL. The period in 1993 is a period of 

occasional higher airborne contamination in the Hot Lab as a result of the D&D operations, and 
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 15 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

may be the bounding exposure scenario for the CEP period. Since the new bioassay vendor 

started analyzing samples in August 1993, any intakes from the previous quarters would likely 

be detected. 

CONCLUSION

There are BZ and GA air data available for Area IV of the SSFL during the CEP period, but they 

are not complete for some quarters. Data for the Hot Lab is available and can be considered a 

bounding scenario, based on available operations descriptions and workers being monitored. 

There is no clear evidence that the general air and breathing zone data are in any way unusual, 

given the operational status of the facilities at the time. Elevated air samples and whole body 

count results are in line with the work that was being completed then. There were a few localized 

elevated samples observed during the 1993 period, when bioassay are not useable for the first 

half of the year, but there is no indication that between the WBC and the bioassay sampling 

taking place in August would have led to significant missed exposures. Whole body counts and 

BZ samples wer e collected for workers in locations likely to receive an intake. Not all air and 

BZ data is available for all quarters and facilities, but it is believed this is because it has not been 

captured, not because it does not exist. There is no evidence that additional data capture for 

remaining quarters and facilities will lead to a different conclusion on the status of the air data or 

the feasibility to assess internal doses for Area IV SSFL using available data or the coworker 

model. 

REFERENCES 

Activity Reports, 1991, Compilation of Weekly Activity Reports for Radiation Protection and 

Health Physics Services, throughout 1991, correspondence, P. Rutherford, Rockwell 

International, various dates throughout 1991. [SRDB Ref ID: 166437] 

Activity Reports, 1992, Compilation of Weekly Activity Reports for Radiation Protection and 

Health Physics Services, throughout 1992, correspondence, P. Rutherford, Rockwell 

International, various dates throughout 1992. [SRDB Ref ID: 166447] 

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Health Physics Services, throughout 1993, correspondence, P. Rutherford, Rockwell 

International, various dates throughout 1993. [SRDB Ref ID: 166450] 

Annual Report, 1992, Annual Report Rockwell International Hot Laboratory Decommissioning, 

GFY 1992, E. M. Larson, Rockwell International, July 02, 1993. [SRDB Ref ID: 

072050] 

Annual Report, 1993, Annual Report Rockwell International Hot Laboratory Decommissioning, 

GFY 1993, L. D. Felton, Rockwell International, April 26, 1995. [SRDB Ref ID: 

072025] 
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 16 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Annual Report, 1994, Annual Report Rockwell International Hot Laboratory Decommissioning, 

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International, March 21, 1980. [SRDB Ref ID: 019136]

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International, May 27, 1980. [SRDB Ref ID: 019135]

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International, August 06, 1980. [SRDB Ref ID: 019134]

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International, September 15, 1980. [SRDB Ref ID: 019133]

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International, January 29, 1985. [SRDB Ref ID: 019130]

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International, January 25, 1986. [SRDB Ref ID: 019129]

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International, March 18, 1986. [SRDB Ref ID: 019128]

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International, July 11, 1986. [SRDB Ref ID: 019142]

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International, July 05, 1988. [SRDB Ref ID: 019141]

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International, May 12, 1989. [SRDB Ref ID: 019139]
White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 17 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Documented Communication, 2017a, Documented Communication with Former Area IV of the 

SSFL Employee, Email communication by ORAU Team and NIOSH, May 10, 2017. 

[SRDB Ref ID: 166848]

Documented Communication, 2017b, Personal Communication with Former Area IV of the 

SSFL Employee, Interview by ORAU Team and NIOSH, April 18, 2017. [SRDB Ref ID: 

166847]

Incident, 1993, Radiological Safety Report ─Personnel Contamination of Co-60 and Cs-137 on 

T-shirt, Rockwell International internal letter, August 10, 1993. [SRDB Ref ID: 166190]

Incidents, 1990, Historical Radiological Incidents ETEC-SSFL, compilation of incident files 

received from DOL in December 2017. [SRDB Ref ID: 169476]

Moore, 1992, Internal Dose Assessment Program Procedures, Operating Procedure, J. D. 

Moore, Rockwell International; December 16, 1992. [SRDB Ref ID: 073474]

NIOSH, 2017, SEC Petition Evaluation Report for Petition SEC-00235, Area IV of the Santa 

Susana Field Laboratory, National Institute for Occupational Safety and Health 

(NIOSH); May 11, 2017. [SRDB Ref ID: 174360]

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White Paper Air Sample Data at Area IV SSFL in Support of SEC-00235 November 6, 2018

Page 18 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Quarterly Reviews, 1991-1993, Compilation of Quarterly ALARA and Surveillance Reports 

(1991-1993), correspondence, various authors, Rockwell International, various dates 

through 1991-1993. [SRDB Ref ID: 166444]

Transcript, 2017, U.S. Department of Health and Human Services Centers for Disease Control 

National Institute for Occupational Safety and Health, Advisory Board on Radiation and 

Worker Health, Area IV of the Santa Susana Field Laboratory Work Group, Transcript, 

Monday, December 4, 2017. [SRDB Ref ID: 174359] 

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California Department of Health Services, April 13, 1994. [SRDB Ref ID: 170405]

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