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Review of NIOSH’s Current Approach to Reconstruction of 

Insoluble Tritium Particulate at the Pinellas Facility

Revision 0

National Institute for Occupational

Safety and Health

December 11, 2015 

Mutty Sharfi

Oak Ridge Associated Universities Team

- 

Reviewed by James Neton

Division of Compensation Analysis and Support
 

This 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

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Background 

During the Pinellas working group meeting on November 19, 2012, NIOSH indicated that they 

wanted to review the current approach to reconstruction of insoluble tritium exposures at 

Pinellas. While the approach described in section 5.7.1.2 of the Pinellas site profile (ORAUTTKBS-0029-5) is similar to that used for the Mound facility, NIOSH wanted to make sure that 

the methodology and parameters used for the bounding intake calculation were appropriate. To 

this end, the following 5 issues were evaluated: 1) the resuspension value used; 2) the validity of 

the bounding contamination survey used; 3) the appropriateness of the tritide measurement 

technique; 4) a review of the extent of tritide contamination, and 5; the solubility types of tritides 

present at Pinellas. A review of each of these issues is provided below. 

Issue 1: The appropriateness of the 1E-06 resuspension factor (RF) in light of the approach 

currently being adopted at Mound that uses an RF of 5E-05 

A review of the Mound facility and other sites where resuspension factors have been applied in 

active work areas was performed. An RF of 1E-06 is generally used for undisturbed areas; 

whereas, an RF of 1E-05 is generally used for areas with ongoing operations. As discussed in 

the sections below, Pinellas was aware of the impact of contaminated areas and worked to 

maintain a clean work environment when contamination was identified. However, one could 

argue that the type of tritium work and facilities at Pinellas are similar to those at Mound. 

Therefore, the more favorable to the claimant RF of 5E-05 will be used. This will result in an 

increase in the annual metal tritide (MT) intake rate from 6.184E+05 pCi/year to 3.092E+07 

pCi/year.

Issue 2: The use of the highest contamination survey reported between 1957 and 1973 as 

the basis for the airborne contamination source term

For the Mound approach the site profile calculated the 95th percentile value’s surface 

contamination levels using the 60,264 contamination smear sample results that were captured 

from the site. 

For the Pinellas Plant, little individual contamination smear data is available. The primary data 

source that we have for the Pinellas Plant's contamination survey results were the monthly 

Health Physics Summary Reports that reported the highest contamination levels measured for a 

given month. 

An analysis of the available data of the monthly Health Physics Summary Reports (SRDB 

27095) found the highest surface contamination level reported was 4.4E+06 dpm/100 cm2

, which 

is 10,000 times their control limit. These reports also indicate that surface contamination levels 

above the control limits of 2E-05 μCi/in2 (688 dpm/100 cm2), as early as 1959, and 440 dpm/100 

cm2 (reported in 1969) resulted in the initiation of decontamination efforts. This was confirmed 
 

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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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in an interview of a past radiological control personnel (SRDB 127111) who indicated that metal 

tritide contamination was cleaned up fairly quickly. Radiological Control personnel would take 

wipes in the morning and, if contamination was identified, they would then mop up the area and 

re-survey. The likelihood of routine surface contamination level in the millions of dpm/100 cm2

should be considered unusual and short in duration. 

As a comparison, the assumption of an average contamination level of 4.4E+06 dpm/100 cm2 is 

one to two orders of magnitude higher (depending on the year) than the surface contamination 

levels at Mound, which had a similar process as Pinellas. Therefore, the approach applied at 

Pinellas is considered bounding and favorable to the claimant. 

Issue 3: The ability of the method used to measure smear samples to detect tritium bound 

to particulate metal

The primary focus of tritium contamination monitoring at the Pinellas Plant was monitoring for 

soluble forms of tritium. The three tritium contamination smear analysis procedures that are 

available (SRDB Ref 12806 p 80-82, SRDB Ref 12947 p 95-96 and 135-137) indicate that the 

Pinellas Plant used wetted cotton balls to collect smear samples for tritium contamination 

monitoring. The available procedures also indicate that the cotton ball smear samples were 

rewetted in a paper cup with a prescribed amount of deionized water (8 to 10 ml, depending on 

the procedure), and that a rinsate was squeezed from the cotton balls while they were still in the 

paper cup. These procedures indicate that the rinsate from the cotton balls was then filtered 

through a Whatman #1 filter. Two of the available procedures are undated, but are among a 

collection of other procedures that have dates range from the late-1960s into the 1980s (SRDB 

Ref 12947 p 95-96 and 135-137). The copy of the procedure found in an incident investigation 

report indicates that the rinsate was filtered through a Whatman # 1 filter as late as January 1976 

(SRDB Ref 12806 p 80-82). Interviews with Pinellas Plant workers involved with the tritium 

contamination smear collection and analysis procedures indicate that the rinsate was no longer 

being filtered by 1977 

In an interview with a Health Physicist that was at the Pinellas Plant during 1987–1997 (SRDB 

127111), it was indicated that they had never used the Whatman #1 filter to filter the rinsate from 

the tritium smears. When they analyzed the smears, the rinsate was unfiltered. An additional 

interview with two of the Chemistry Department’s personnel that analyzed the tritium 

contamination smears during the years 1977–1997 (SRDB 129125) stated that they recall rinsing 

the cotton balls used to collect the tritium contamination smear samples. However, they did not 

recall filtering the rinsate through a filter. According to them, filtering the rinsate through a filter 

was not part of the routine analysis procedure when they were at the Pinellas Plant and all of the 

routine tritium contamination smears were analyzed by the same procedure. To their knowledge, 

there were not any routine or special procedures for analyzing the tritium contamination smears 

when metal tritide contamination was suspected. 

One possible purpose of filtering a rinsate could be to limit the amount of dust and dirt ending up 

in the filtrate, which would minimize quenching issues. However, the chemistry department 
 

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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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.Page 4 of 6

personnel indicated that they could not remember any issues with the smears being so dirty that it 

would cause problems with the cocktail solution. 

The Whatman #1 filter paper has a nominal pore size of 11 microns, and a maximum pore size of 

12.7 microns. Therefore, the Whatman #1 filters would only filter out the non-respirable SMT 

particles (i.e. the particles greater than 10 microns), if they filtered out any SMT particulates at 

all. This may have been the reason why the Whatman #1 filters were chosen to be used as a 

filter. 

The SMTs of concern at the Pinellas Plant were deposited as a vapor onto ceramic or metal 

target substrates. The SMTs on ceramic or metal target substrates were typically only dispersed 

from metal flaking off the substrates or from vacuum tube implosions (e.g. the accidental 

breaking of neutron tubes). A material data sheet for titanium-hydride (SRDB 12275, pg 28) 

indicated that average particle size ranged from 6 to 9 microns, which is less than the 11 micron 

nominal pore size for the Whatman #1 filters. Therefore, it is unlikely that there was any loss in 

particulate activity from filtering the rinsate (i.e. there would be no impact to an individual’s

assessed exposure). 

In addition, a Health Physics paper (SRDB 12275, pp 9-11) titled, “A Study of the Particulate 

and Gaseous Emission of Tritium from Neutron Generator Targets”, looked at impact on 

deuteron bombardment on the targets. The study looked at used and new targets. The study 

results for new targets (which what was handled at Pinellas) show that the gaseous emission rate 

was much higher than that of the particulate. This implies that any intake associated particulate 

tritium (SMT) would also be associated with a much higher intake of gaseous tritium (HT and 

HTO), which would have been identified based on the individuals urinalysis results. Since all 

contamination smears in the Pinellas methodology are treated as 100% particulate, even if the 

Whatman #1 filter paper filtered out the SMT particulates, the recorded tritium activity (which 

would be associated with just gaseous tritium alone) would provide a bounding estimate of SMT. 

However, given the Whatman #1 filter paper likely would not filter out the SMT particulate, the 

use of the total tritium results (particulate plus gaseous) as 100% Type S SMT particulate results 

in an bounding estimate of the particulate contamination levels. 

Issue 4: The magnitude and the extent of potential for tritide contamination at Pinellas 

At the Pinellas Plant, insoluble forms of tritium were handled only in areas where the more 

dispersible and more soluble forms of tritium were also present. A review of the available 

dosimetry records indicates that the Pinellas Plant routinely monitored workers with any 

potential for soluble tritium exposures. Therefore, SMT exposures only need to be assessed for 

workers were also monitored for soluble tritium exposures. 

The available information on the Pinellas Plant indicates that only a relatively small portion of 

the Pinellas Plant’s workforce had the potential to be exposed to dispersible forms of SMTs, and 

those scenarios were typically limited to accidents. The available incident information in the 

monthly health physics reports (SRDB 13358, 27095, 133577, 133579, 133580, 133581, 133583, 
 

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.Page 5 of 6

133586, and 133591) indicate that when the contamination levels exceeded the control level, the 

affected areas were cleaned up immediately. There is no indication from these reports that 

routine contamination levels were close to the bounding levels assumed in the Pinellas approach. 

In a lot of cases, the source of the contamination from these reported incidents (SRDB 13358, 

27095, 133577, 133579, 133580, 133581, 133583, 133586, and 133591) are not associated with 

SMTs. Rather, they are associated with loaded glass tubes of tritiated gas that were dropped 

releasing the tritium gas or from maintenance activities (which would likely be associated with 

tritiated pump oils, i.e. OBTs). Exposures associated from these types of releases would be also 

captured in the analysis of the tritium bioassay. 

In cases (SRDB 27095) where contamination was associated with actual SMTs releases, it was 

normally associated with titanium tritide, which is a more soluble SMT (Type M). The 

assumption that 100% of all intakes are Type S SMTs is not a likely scenario, but is a favorableto-the-claimant assumption. Scandium tritide was the only known Type S insoluble tritium 

compound present at the Pinellas Plant. 

The highest reported tritium surface contamination level was 4.4E+06 dpm/100 cm2

 (10,000 

times the control limit). This was reported in a 1970 health physics summary report (SRDB 

27095) and was associated with maintenance operations, not a SMT incident. The highest 

tritium contamination level associated with a SMT incident (SRDB 27095) was 1.89E+05

dpm/100 cm2

 (about 4% of the surface contamination level used to estimate the SMT exposure in 

the TBD). In most cases, tritium surface contamination level associated with a SMT incident 

was at least an order of magnitude less. This means that the use of the highest reported tritium 

surface contamination level assumed to have occurred for 2000 hours/year to estimate the SMT 

exposure rate likely results in a SMT exposure that is orders of magnitude larger than the actual 

potential SMT exposure. 

Issue 5: The relative solubility of the various metal tritides present

The Pinellas Plant had SMTs representing all three lung absorption types. The SMTs at the 

Pinellas Plant were primarily erbium tritide (Type M), scandium tritide (Type S), titanium tritide

(Type M), and uranium tritide (Type F), but other less prevalent SMTs were also at the site. 

From 1957 through 1967, glass tritide storage beds that utilized titanium metal were used (SRDB 

12026). Elemental target material (typically erbium, scandium, or titanium) was deposited as a 

vapor onto a ceramic or metal target substrate (SRDB 12945 & 88797), after which the targets 

were loaded in the neutron tubes. The nearly completed neutron tubes were then attached to a 

glass manifold vacuum system under an exhaust hood. The glass encased titanium-hydride 

storage beds were replaced with stainless-steel encased depleted uranium-hydride storage beds in 

1968 (SRDB 13125). 
 

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Therefore, the source term for SMT exposures are typically not Type S SMTs, rather the more 

moderately insoluble and soluble Type M and F SMTs. The assumption that 100% of all intakes 

are Type S SMTs is not a realistic scenario, but it is a favorable to the claimant assumption.

Conclusions

Given the ongoing nature of operations at Pinellas, NIOSH believes that the resuspension value 

of 1E-06 used is in the current TBD should be increased to 5E-05. A review of the filtration 

methodology employed to measure smears at Pinellas indicates that the technique is capable of 

quantitatively assaying particulate tritium contamination. Because the majority of the smear 

surveys (and in particular the highest ones) were likely to represent soluble or slightly insoluble 

tritium compounds, NIOSH concludes that the use of the highest measured contamination survey 

result will result in claimant favorable doses to workers at Pinellas.