Weldon Spring Petition Upd

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 w

radon released during processing was re‐circula

the facility as bounding

• The maximum concentration of radon, based on rele

estimate, to be assigned for intake

 May 2011: discussion and clarification, but no c

proposed direction

 June 2012: WG asked for additional detail to be 

to these slides and for presentation of same to 

ABRWH
Bounding Radon Model—cont

 Weldon Spring Historical Dose Estimate (AN

TM‐308, Meshkov et al., 1986) estimates anradon emissions of 12‐34 Ci/yr

 Radon assumed to be released into the wor

of the refinery, building 103

 Radon emission rate and very low building

ventilation rate were used to calculate equilconcentration 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. w

lived alpha emitting progeny

 Hours in a WLM = 170

 Equilibrium factor = 0.5

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

 Note: At the June Board meeting an equilib

factor of 0.5 was questioned as perhaps bei

low for a building with a low ventilation rate

increase to a more bounding equilibrium fac

would increase the WLM exposure estimate

proportionally, and thus is a site profile rath

an SEC issue.
Bounding Radon Model—cont

 Ceq is the radon‐222 equilibrium conc. (pCi/L) 

ventilated room

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

 V is the volume of the space in L ach is the number of air changes per hour
Bounding Radon Model—cont

so
Recycled Thorium

 EPA Environmental Impact Statement from 1

and other references from that period say ra

pits 3 and 4 contain “thorium‐contaminated

raffinate solids from processing thorium rec

products” or other phrases indicating recyclthorium

 EEOICPA program uses “recycled” to describ

materials irradiated in a reactor then recovere‐use, but outside EEOICPA its meaning is n

specific
Recycled Thorium—cont.

 The question is, had the thorium at Weldon 

previously been irradiated and, if so, to wha

would radiological impurities in recycled thoaffect dose reconstruction

 Inventory records available for Weldon Sprin

show that thorium was present in significan

quantities and processed only during the pe

1963‐1966
Recycled Thorium—cont.

 DOE thorium irradiations (to produce U‐233

occurred at Savannah River starting in the m

1960s

 Documentation from Savannah River indicat

the first shipment of previously‐irradiated areclaimed thorium (recycled thorium) would 

sent to Fernald no earlier than November 19
Recycled Thorium—cont.

 From this, NIOSH concludes that the thorium

processed at Weldon Spring from 1963‐1966 

not recycled thorium, as the term is used in

EEOICPA
Raffinate Pit Drying

 A number of references from the 1980s and 

state raffinate pits were typically covered wwater but pits 1 and 2 were not covered dur

weather periods

 This raised the question of whether resuspe

from the raffinate pits could have been a so

significant exposure during or after operatioperiod
Raffinate Pit Drying—cont.

 Summary of covered periods

• 1955 to 1966 ‐ operational period for WS plant a

raffinate pits

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

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 availa

from:

• 1959‐1965 in Meshkov et al., 1986

• 1987‐2000 in environmental monitoring reports 

by M.K. Ferguson and Jacobs Engineering

• 1966‐1986 various documents from this period d

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

 For the period 1967 to roughly 1985, it appe

unlikely that there were any covered emploWS. The Army controlled WS Plant, and the

raffinate pits were not being used

 If claimants are identified in this period, it s

be possible to use air sampling results from 

estimate exposures from resuspension
Raffinate Pit Drying—cont.

 For the operational period, 1957 to 1966,

resuspension from the pits, if they dried, sh

reflected in the boundary station air samplin

results for that period.

 Environmental dose estimates in the WS Sit

incorporate boundary station air sampling r

and a much larger intake estimate based on proximity to airborne‐generating activities
Raffinate Pit Drying—cont.

 If it is assumed that the boundary airborne

concentrations are comprised of raffinate pi

contents (all resuspension is from pits), thecorresponding adjustment to reconstructed 

would be nominal because of the much larg

presumed intake from being in proximity toairborne‐generating activities