Weldon Spring Petition Update

Stuart Hinnefeld, CHP

Director

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support

September 2012

Denver, CO
Update on 3 WS Issues

 Bounding radon model

 Recycled thorium 

 Raffinate pit drying
Bounding Radon Model

 January 2011: NIOSH presented a scenario in which all 

radon released during processing was re-circulated into 

the facility as bounding

• The maximum concentration of radon, based on release 

estimate, to be assigned for intake

 May 2011: discussion and clarification, but no change in 

proposed direction

 June 2012: WG asked for additional detail to be added 

to these slides and for presentation of same to full 

ABRWH
Bounding Radon Model—cont. 

 Weldon Spring Historical Dose Estimate (ANL/EESTM-308, Meshkov et al., 1986) estimates annual 

radon emissions of 12-34 Ci/yr

 Radon assumed to be released into the work area 

of the refinery, building 103

 Radon emission rate and very low building 

ventilation rate were used to calculate equilibrium 

concentration in building 103
Bounding Radon Model—cont. 

 Building 103 volume: 2.6 x 104 m3

 Ventilation rate: 1 air change per hr

 34 Ci/yr = 3.9 x 109 pCi/h

 1 WL = 100 pCi/L of Ra-222 in full equilib. with short 

lived alpha emitting progeny

 Hours in a WLM = 170

 Equilibrium factor = 0.5

 Number of occupational work hours = 2,000/yr
Bounding Radon Model—cont. 

 Note: At the June Board meeting an equilibrium 

factor of 0.5 was questioned as perhaps being too 

low for a building with a low ventilation rate; an 

increase to a more bounding equilibrium factor 

would increase the WLM exposure estimate 

proportionally, and thus is a site profile rather than 

an SEC issue.
Bounding Radon Model—cont. 

 Ceq is the radon-222 equilibrium conc. (pCi/L) in a 

ventilated room 

 I is the influx of radon-222 in pCi/h = 3.9 x 109 pCi/h

 V is the volume of the space in L

 ach is the number of air changes per hour
Bounding Radon Model—cont. 

so
 EPA Environmental Impact Statement from 1989 

and other references from that period say raffinate 

pits 3 and 4 contain “thorium-contaminated 

raffinate solids from processing thorium recycled 

products” or other phrases indicating recycled 

thorium

 EEOICPA program uses “recycled” to describe 

materials irradiated in a reactor then recovered for 

re-use, but outside EEOICPA its meaning is not so 

specific

Recycled Thorium
Recycled Thorium—cont. 

 The question is, had the thorium at Weldon Spring 

previously been irradiated and, if so, to what extent 

would radiological impurities in recycled thorium 

affect dose reconstruction

 Inventory records available for Weldon Springs 

show that thorium was present in significant 

quantities and processed only during the period 

1963-1966
Recycled Thorium—cont. 

 DOE thorium irradiations (to produce U-233) 

occurred at Savannah River starting in the mid1960s

 Documentation from Savannah River indicates that 

the first shipment of previously-irradiated and 

reclaimed thorium (recycled thorium) would be 

sent to Fernald no earlier than November 1966
 From this, NIOSH concludes that the thorium 

processed at Weldon Spring from 1963-1966 was 

not recycled thorium, as the term is used in 

EEOICPA

Recycled Thorium—cont. 
Raffinate Pit Drying

 A number of references from the 1980s and 1990s 

state raffinate pits were typically covered with 

water but pits 1 and 2 were not covered during dry 

weather periods

 This raised the question of whether resuspension 

from the raffinate pits could have been a source of 

significant exposure during or after operational 

period
Raffinate Pit Drying—cont. 

 Summary of covered periods

• 1955 to 1966 - operational period for WS plant and 

raffinate pits

• 1967 to Sept 1985 – “inactive” period; during this period 

WS plant was controlled by Dept. of the Army

• Oct 1985 to 2002 – remediation period
Raffinate Pit Drying—cont. 

 Site perimeter air sampling results are available 

from:

• 1959-1965 in Meshkov et al., 1986

• 1987-2000 in environmental monitoring reports prepared 

by M.K. Ferguson and Jacobs Engineering

• 1966-1986 various documents from this period describe 

air sampling results indistinguishable from background
Raffinate Pit Drying—cont. 

 For the period 1967 to roughly 1985, it appears 

unlikely that there were any covered employees at 

WS. The Army controlled WS Plant, and the 

raffinate pits were not being used

 If claimants are identified in this period, it should 

be possible to use air sampling results from 1987 to 

estimate exposures from resuspension 
Raffinate Pit Drying—cont. 

 For the operational period, 1957 to 1966, 

resuspension from the pits, if they dried, should be 

reflected in the boundary station air sampling 

results for that period. 

 Environmental dose estimates in the WS Site Profile 

incorporate boundary station air sampling results 

and a much larger intake estimate based on being in 

proximity to airborne-generating activities
Raffinate Pit Drying—cont. 

 If it is assumed that the boundary airborne 

concentrations are comprised of raffinate pit 

contents (all resuspension is from pits), the 

corresponding adjustment to reconstructed doses 

would be nominal because of the much larger 

presumed intake from being in proximity to 

airborne-generating activities