DRAFT 

A Second White Paper Addressing Enhanced Radon 

Releases from the K-65 Silos at the Fernald Site 

Contract No. 200-2009-28555 

Prepared by U. Hans Behling, PhD 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, VA 22182

April 2010 

Disclaimer 

This document is made available in accordance with the unanimous desire of the Advisory Board on 

Radiation and Worker Health (ABRWH) to maintain all possible openness in its deliberations. However, 

the ABRWH and its contractor, SC&A, caution the reader that at the time of its release, this report is predecisional and has not been reviewed by the Board for factual accuracy or applicability within the 

requirements of 42 CFR 82. This implies that once reviewed by the ABRWH, the Board’s position may 

differ from the report’s conclusions. Thus, the reader should be cautioned that this report is for 

information only and that premature interpretations regarding its conclusions are unwarranted. 
Draft White Paper – Fernald i SC&A – April 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

TABLE OF CONTENTS 

1.0 Relevant Background Information ...................................................................................... 1

2.0 Discussion Points Raised During the Fernald Work Group Meeting Held on 

January 29, 2010 ................................................................................................................. 2

2.1 Regarding the Use of the “Pinney Study” as a Means for the Validation of 

Radon Releases ....................................................................................................... 3

2.2 Review Comments and Relevant Conclusions Regarding the “Pinney 

Report” .................................................................................................................... 4

2.3 Overview of the RAC Models ................................................................................ 5

3.0 Other Data Identified by NIOSH for SC&A’s Review .................................................... 10

3.1 Review of Study #1: Killough and Schmidt (2000)............................................. 10

3.2 Review of Study #2: Hagee et al., 1985............................................................... 11

4.0 Discussion and Summary Conclusions ............................................................................. 14

4.1 The Role of Wind and the Venturi Effect ............................................................. 15

References ..................................................................................................................................... 20

Attachment 1: Table 2 from Hagee et al. 1985 ............................................................................ 21

LIST OF EXHIBITS 

Exhibit 1: Figure 15 from RAC 1998 ..............................................................................................7

Exhibit 2: Figure 16 from RAC 1998 ..............................................................................................8

Exhibit 3: Figure 17 from RAC 1998 ..............................................................................................9

Exhibit 4: Table 8 from RAC 1998 ................................................................................................15

Exhibit 5: Table J-19 from Appendix J of RAC 1995 ...................................................................19
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1.0 RELEVANT BACKGROUND INFORMATION 

On January 29, 2010, the Fernald Work Group met in Cincinnati, Ohio, to discuss/resolve six 

outstanding issues pertaining to the Fernald site. Among the unresolved issues was SC&A’s 

contention that radon releases from the K-65 Silos may have been significantly underestimated 

by NIOSH, as stated in ORAUT-TKBS-0017-5 (ORAUT 2004): 

As previously stated, the contents of the silos have not been disturbed during 

storage to any large degree. However, it has been calculated that during the 

1953 to 1978 period 5,000 to 6,000 Ci/year of 222Rn were released from the silos 

(RAC 1995). [Emphasis added.] 

In a previous White Paper issued in November 2008 (SC&A 2008), SC&A conducted a critical 

review of the Radiological Assessment Corporation 1995 model (RAC 1995). Based largely on 

empirical measurements taken on top of the silos that ironically were included in Appendix J of 

the 1995 RAC Study, SC&A concluded that the modeled release estimates cited in the 1995 

RAC Study were likely a factor of 10 to 20 too low. 

In a memorandum to the Work Group Chairperson, Mr. Brad Clawson, dated October 6, 2009, 

NIOSH rejected SC&A’s analysis and conclusions with the following statements:

NIOSH disagrees with the draft findings reported by SC&A. The RAC model was 

supported by a National Academy of Sciences review; SC&A’s was not. NIOSH 

will rely upon the individual exposure estimates produced using the Pinney/ 

Hornung model which utilized radon exposure levels from the RAC study, plus an 

additional radon source term at Fernald. . . . [Emphasis added.] 

In response to NIOSH’s position, the Work Group directed SC&A to review the National 

Academy of Sciences’ (NAS) review of the 1995 RAC model (NAS 1994).1 On January 26, 

2010 (or three days before the Work Group meeting held on January 29, 2010), SC&A submitted 

its findings regarding the NAS review to the Work Group/NIOSH in the form of a memorandum. 

Our review of the NAS Report showed that there was little support for the RAC model.

 

1

 Note that the National Academy of Sciences performed their review on a 1993 draft of the 1995 RAC 

report. 
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2.0 DISCUSSION POINTS RAISED DURING THE FERNALD WORK 

GROUP MEETING HELD ON JANUARY 29, 2010 

A review of the Work Group’s transcript shows that the issue of radon emissions from the K-65 

Silos was discussed on pages 266 through 294 (NIOSH 2010). For convenience, select 

statements contained in the transcript will be cited below for further discussion. 

 Regarding the “NAS Endorsement” of RAC (1995) Model: (pp. 278–279 of transcript) 

MR. ROLFES: Okay. Looking at the National Academy of Sciences' 

review, it's got a -- I'm reading from the National Academy of Sciences' review of 

the RAC dose reconstruction for Fernald, and on page 17 of the PDF, it has a 

radon section, and I can read that if you'd like. 

DR. MAURO: Is that what you're reading now? 

MEMBER ZIEMER: I'm reading it right now, yes. It certainly leaves 

the question open. 

MR. ROLFES: I'll go ahead and read that into the record. "The 

importance of the radon source term associated with the K-65 silos is difficult to 

establish primarily because the silos have been modified several times over the 

years. If the head space has been adequately sampled, the silos inventory could 

be modeled for release, assuming no retardation by the cap which has been 

sealed to various degrees over the years as a worst case endpoint.

"It is reasonable to separate the calculations into daytime and nighttime 

dispersion because the dispersion figures would certainly differ. However, there 

is no justification given for the release terms of 140 curies per year continuous or 

810 curies per year during the daytime only. It also might be a reasonable 

refinement to have transition periods in between." 

So I think that's really the part that is relevant, and it basically calls into 

question what the release is, and so the RAC report doesn't really get us any 

further down the road on, you know, validating the radon releases. . . . 

[Emphasis added.] 

From these statements, SC&A concludes that neither the Work Group nor NIOSH is of the 

opinion that the NAS concurred with the RAC (1995) model. 
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2.1 REGARDING THE USE OF THE “PINNEY STUDY” AS A MEANS FOR THE 

VALIDATION OF RADON RELEASES 

The “Pinney Study” was referenced multiple times in the Fernald Work Group transcript and is a 

reference to a study that was published in 2008 entitled, Estimation of Radon Exposure to 

Workers at the Fernald Feed Materials Production Center 1952–1988, by R.W. Hornung, S.M. 

Pinney, J. Lodwick, G. Killough, D.E. Brewer, and J. Nasuta in the Journal of Exposure Science 

and Environmental Epidmiology, pages 1–12 (Hornung et al. 2008). 

From page 291 of the transcript: 

MR. MORRIS: Okay. I'd like to also point you to a memo that Dr. 

Pinney wrote to [redacted] on September 13th, 2006, while [redacted] was 

preparing information for the SEC petition apparently, and she writes to 

[redacted] about using the data from the RAC report which was an off-site 

dosimetry model and extending it, extrapolating it back toward the source term to 

reconstruct the doses on the site. She got assurance from the model developer, 

Dr. Killough or Mr. Killough, that it could be extrapolated back on-site, and then 

took the initial action that she describes of validating that model based on some 

on-site information that was available. . . . [Emphasis added.] 

From page 293 of the transcript: 

MR. ROLFES: Right. That seems that the Pinney model has the 

validation of the RAC model essentially in it, and what we had previously said 

had been reviewed by the National Academy of Sciences, when the RAC model 

was reviewed by the NAS, we thought that it had spoken to the radon effluent, but 

it didn't very much, and now what we have here when we look back at the 

documentation we have, we found that the Pinney model actually relies upon the 

RAC model, which has been validated by Susan Pinney's model as well.

[Emphasis added.] 

These statements lack clarity and appear contradictory, inasmuch as they suggest that Pinney 

“relied” upon the RAC model, but then states that it was “validated” by the “Susan Pinney 

Model.”

 From page 300 of the transcript: 

CHAIRMAN CLAWSON: Well, you know, the bottom line comes down 

to SC&A has not been able to see this, and we've got to go back a little ways 

because this was held up to us as the holy grail for the radon and that everything 

was good with it, and now we've changed our whole course to that. So we're 

going to have to have SC&A review what NIOSH has put out there, the Pinney 

report, and so forth because, you know, we're changing whole directions. 
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MR. ROLFES: That's a slightly different -- we've always said since our 

Evaluation Report that we were relying upon the Pinney data. So I did want to 

point that out. [Emphasis added.] 

2.2 REVIEW COMMENTS AND RELEVANT CONCLUSIONS REGARDING THE 

“PINNEY REPORT”

At the request of the Fernald Work Group, SC&A reviewed the 2008 “Pinney Report” (Hornung 

et al. 2008) with regard to its use/validation of radon releases that were modeled by RAC. Based 

on our review, SC&A concludes the following: 

(1) The Pinney Report simply accepted the source term releases of radon from the 

K-65 Silos, as described by the following two RAC reports issued in 1995 and 1998: 

 RAC (1995): The Fernald Dosimetry Reconstruction Project, Tasks 2 and 2 

Radiologic Source Terms and Uncertainties.

 RAC (1998): The Fernald Dosimetry Reconstruction Project, Task 6 Radiation 

Doses and Risks to Residence from FMPC Operations from 1951–1988.

(2) Using the modeled RAC (1995)/RAC (1998) radon release source terms, the “Pinney 

Report” investigators applied a modified Gaussian dispersion model originally intended 

for estimating exposure to residents living within a 10-km radius to estimate onsite radon 

exposures to Fernald workers, as explained in their report: 

From page 2 of the 2008 “Pinney Report”: 

The radon dispersion model was developed by Radiological Assessments 

Corporation (RAC) under contract to the CDC as part of the overall dose 

reconstruction that also included uranium and thorium doses from air and water 

transport. The model had been applied to the estimation of radon exposures to 

residents living near the facility. Details of the development of this model are 

given by Voilleque et al . (1995) [RAC 1995] and Killough et al. (1998) [RAC 

1998] and are beyond the scope of this paper. We have, however, included an 

abbreviated description of the atmospheric dispersion model in Appendix A. The 

model was studied to determine what revisions would be required to make it 

applicable to the estimation of radon exposures to Fernald workers who were 

considerably nearer to the K-65 silos. The radon transport model involved 

emission rates from the silos, meteorological data, distance from the source, 

and decay rates of radon decay products. The output of the model was annual 

average exposure in either pCi/l or Bq/m3at any location specified by longitude 

and latitude coordinates. . . . [Emphasis added.] 
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 From Appendix A of the 2008 Pinney Report: 

The K-65 source term model is an empirical representation of the annual 

release of radon from the K-65 silos from 1952 through 1988. It was calibrated 

to a variety of data, primarily (1) the concentration of radon in the silo headspace 

gas, measured in 1987, (2) measurements of g-ray exposure on the external silo 

dome surfaces before and after they were sealed, and (3) a series of temperature 

and pressure readings in the silo headspace gas, taken in 1987. It is a stochastic 

model, with some parameters derived as probability distributions, which 

propagate into the annual release estimates. Detailed information about the 

K-65 source term model and the ratio of decay products at the point of release is 

given in Appendix Q of Killough et al. (1998) [RAC 1998], with references to 

the earlier report of Voilleque et al. (1995) [RAC 1995] for some details. 

. . . The transport model used for the study described in this paper is adapted from 

the transport model of Killough and Schmidt (2000), but it is coupled with the 

original K-65 source term developed for the CDC dose reconstruction study, as 

described in Appendix Q of Killough et al. (1998) [RAC 1998] and in Voilleque 

et al. (1995) [RAC 1995]. [Emphasis added.] 

This last statement clearly states that the “Pinney Model” simply “ . . . coupled the original K-65 

source term . . .,” as defined in RAC 1995 and RAC 1998, to the radon transport model 

employed by the “Pinney Model.” Thus, contrary to NIOSH’s opinion, the “Pinney Report” 

made no effort to validate the radon source terms defined in RAC 1995 and RAC 1998. 

2.3 OVERVIEW OF THE RAC MODELS 

As already noted above, the 1995 Voilleque et al. study represents the RAC (1995) study, which 

was referenced by NIOSH in the Fernald Site Profile (ORAUT-TKBS-0017-5), and was the 

principal source of information for SC&A’s previous White Paper issued in November 2008 (An 

Alternative Assessment of Radon Release from K-65 Silos) (SC&A 2008). 

In 1998, the 1995 RAC Report was updated/modified. The revised report included (1) a brief 

description of the conventional model that had been described in Appendix J of the earlier 1995 

RAC study, and (2) an updated model that was termed the preferred model that was described 

in Appendix Q of RAC (1998). 

The following excerpts from the 1998 RAC report summarize the earlier conventional model 

and the updated preferred model: 

 From Vol. 1, pages 23 and 27, of RAC 1998: 

 Appendix J of our Task 2/3 report (Voilleque et al. 1995) [RAC 1995] described 

the radon releases in considerable detail; much of the following information is 

summarized from that appendix. . . . 
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 There are no direct measurements of release quantities for radon and 

radon decay product releases . . . The most important data sets for reconstructing 

the radon releases . . . are discussed in the Task 2/3 report (Voilleque et al. 1995) 

[RAC 1995] and in Appendix Q of this report (Volume II). 

 Because of the limited availability of data, models were used to estimate 

the quantities of radon and radon decay products that were released. A 

conventional model for estimating radon releases from radium-226-bearing 

material involves calculating the quantity of radon formed in the material and the 

subsequent diffusion of the radon through the material to the outside air. The 

conventional model was not the primary model employed in this study because 

site-specific measurements of the radon diffusion coefficient and radon emanation 

fraction had not been made. Instead, our preferred method was to develop and 

adapt other models to calculate air exchange, diffusion, and total radon releases 

from the data that were available. Figure 15 compares our preferred method to 

the conventional method. The conventional method was used for a secondary 

calculation to provide a limited check of our primary calculation. . . . [Emphasis 

added.] 

For convenience, “Figure 15” cited above is reproduced herein as Exhibit 1. Of significance are 

statements that acknowledge the limitations and high uncertainties of these models. 

Revised estimates of annual release rates for the preferred method are cited by RAC (1998) in 

Figure 16 and reproduced herein as Exhibit 2. Figure 17 (reproduced herein as Exhibit 3) 

presents a comparison between release estimates derived in behalf of the RAC (1998) preferred 

method and the RAC (1995) conventional method. According to the authors of the two RAC 

reports, while the addition and/or refinements of model parameters only modestly affected the 

median values, there was a significant reduction in the uncertainty of release rates. 

Inspection of Exhibit 3 also shows that, in addition to RAC’s preferred method estimates and 

its conventional method estimates, the authors identified yet a third method, referred to as the 

concentration-based minimum unconstrained release rate, shown by the gray band. The 

issue of “unconstrained” will be discussed in greater detail in Section 3.1 below.
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Exhibit 1: Figure 15 from RAC 1998 
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Exhibit 2: Figure 16 from RAC 1998 
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Exhibit 3: Figure 17 from RAC 1998 
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3.0 OTHER DATA IDENTIFIED BY NIOSH FOR SC&A’S REVIEW 

During the January 29, 2010, Fernald Work Group meeting, NIOSH also identified the following 

two studies to SC&A with the expectation that these studies would further challenge SC&A’s 

claim for enhanced radon emissions from the K-65 Silos: 

 Killough, G.G. and D.W. Schmidt, 2000, Uncertainty Analysis of Exposure to Radon 

Released from the Former Feed Materials Production Center, Environmental 

Radioactivity, Vol. 49, pp. 127–156.

 Hagee, G.R., P.H. Jenkins, P.J. Gephart, and C.R. Rudy, 1985, Radon and Radon Flux 

Measurements at the Feed Materials Production Center, Fernald, Ohio, U.S. Department 

of Energy, MLM-MU-85-68-001. 

Presented below are summary descriptions of these two studies, with focus on issues salient to 

radon release estimates from the K-65 Silos. 

3.1 REVIEW OF STUDY #1: KILLOUGH AND SCHMIDT (2000) 

Important to note here is that the two authors of this study (i.e., Killough and Schmidt) were also 

co-authors of the two previous RAC (1995) and RAC (1998) studies. Thus, in addition to the 

“Preferred Method” estimates, the “Conventional Method” estimates, and the “Concentrationbased Minimum Unconstrained Release Rate Method” described in RAC (1998), yet a fourth 

method was proposed by these authors, which they termed “Empirical Release Model.” The 

fourth “Empirical Release Model” was described in Section 2.1 of their report and provides the 

following explanation: 

2.1. The release model 

The model for release of radon and its decay products that was used in the 

dose reconstruction study is based on measurements, material balance, and other 

physical assumptions. The details, which are somewhat complicated, are given 

elsewhere (Voilleque et al., 1995; Killough et al., 1998) [RAC 1995; RAC 

1998], and we hope to submit a summary for the open literature. We provide 

here a simpler counterpart of the release model, which mimics the original 

adequately for our purpose. This imitation was derived by Monte Carlo methods, 

using the authentic model to generate 1000 sets of releases and estimating 

parameters of the relevant distributions from the resulting data. In this paper, we 

call the radon release model derived in this fashion “empirical” because it 

consists of a joint distribution that is based on sampling the output of the original 

model. Before giving details of the empirical model, it is necessary to explain 

how the releases changed over time during the operation of the plant. 

The years 1952–1988 are divided into five major periods, corresponding 

to changes in the structure or operation of the K-65 silos. These periods are 

1952, 1953–1958, 1959–1979, 1980–1987, and 1988. During the first two 
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periods, the silos were being filled. The third period corresponds to releases at 

the highest annual rate. The fourth period represents the time after the silo 

domes were sealed in 1979. In December 1987, a layer of foam was added to the 

silo domes, further reducing the release rate, and hence 1988 is considered a 

distinct period. The dose reconstruction project's temporal scope ended with 

1988.

During each major release period, it is assumed that the release rate for 

radon is constant with time. Thus the release for each year of a given period is the 

same, but the annual rate varies from one period to another. [Emphasis added.] 

For the time between 1959 and 1979 (which coincides with the time period of concern to 

SC&A), Killough and Schmidt (2000) derived an annual release estimate of 5.41 TBq, which 

corresponds to 146 Ci. 

In spite of their claim that the empirical release model was based on “. . . details, which are 

somewhat complicated [and] are given elsewhere (Voilleque et al., 1995; Killough et al., 1998),”

their new estimate was more than 40 times lower than the median estimates of around 6,000 Ci 

cited in Voilleque et al. 1995, (i.e., RAC 1995), and Killough et al. 1998, (i.e., RAC 1998).

In Section 4.0 of this report, SC&A identifies a common flaw that adversely limits the credibility 

of all four RAC models/release estimates. 

3.2 REVIEW OF STUDY #2: HAGEE ET AL., 1985

In 1984, the U.S. Department of Energy (DOE) sponsored a radon and radon flux study at 

Fernald that focused on the K-65 Silos as the principal source terms for radon releases. 

Important to note is that the time of this study post dates the June 1979 remediation effort by 

5 years. Remediation efforts included (1) the removal of a 15-cm diameter gooseneck at the topcenter of the dome, (2) use of sealant gaskets for four influent manholes and one unloading 

manhole, and (3) use of sealant for all other visible penetrations and structural cracks. Although 

the results of this study have limited quantitative value to SC&A’s contention of enhanced radon 

releases prior to 1979, there are, nevertheless, interesting observations/measurements that 

support our contention of enhanced radon releases prior to 1979.

In this study, radon flux measurements from concrete surfaces were made by means of charcoal 

canisters at 24 locations on top of each of the two silos. Areas selected for flux measurements 

included areas with “obvious cracks and fissures.” For radon flux measurements, the analytical 

methods, instrumentation, results and their limitations are described in Section B of Hagee et al. 

1985. Summarized below are key statements/data taken from Section B of Hagee et al. 1985 that 

are of relevance to this report. 

It was found that when alpha probes were held over some of the obvious cracks, 

the meters (Ludlum Model 12) were disabled even on the least sensitive scale. 
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Likewise, substantial readings were found where metal rods and pipes protruded 

through the concrete surface. 

From these preliminary studies, it was decided that it would be imperative to 

evaluate whether the rate of release of radon from some of the more serous cracks 

was sufficient to saturate charcoal canister [saturation was estimated at 200–

250 μCi]. 

. . . For both of the locations investigated in this study, the 200 to 

250 microcuries [of radon-222] uptake required only 20 minutes of exposure, 

which translated into elevated radon flux values. Clearly, the exposure time for 

these flux measurements is considerably different from the measurements of mill 

tailings and soil which are usually carried out over a period of several days. . . . 

In spite of the selection of the times of exposure as described above, certain 

canisters could not be measured immediately on the scintillation spectrometer . . . 

[due to] . . . prohibitively high count rates on the spectrometer. 

[Furthermore], to permit the measurement of canisters with elevated gamma-ray 

emission rates, two low-geometry counting conditions were established . . . In 

the first condition, the canister was placed on the end of a PVC tube in a 

reproducible location, about 12” from the crystal. In the second condition, lead 

shielding with a hole of approximately 3⁄4-inch diameter was placed on the end of 

the PVC tube. Condition 1 resulted in an efficiency reduction of approximately a 

factor of 20; whereas, in Condition 2, the efficiency reduction was approximately 

a factor of 386. . . . 

Even with reduced counting efficiency, it was necessary in a number of cases to 

wait as long as 8 days before analyzing certain canisters . . . 

Flux values on the north tank ranged from approximately 13 pCi/m2/sec to 3 × 

107

pCi/m2/sec and on the south tank from approximately 30 pCi/m2/sec to 1.4 × 

107pCi/m2/sec.

[Because] the flux values are in pCi/m2/sec, this assumes that the accumulated 

radon is coming from a planar source which, in the case of cracks or fissures is 

not true; . . . 

In another column of Table 2 the rate of radon release is expressed in pCi/cm/sec. 

The assumption made in this case is that the radon is coming through a single 

crack of undefined width whose length is equal to the diameter of the canister . . . 

[Emphasis added.] 

As a benefit to the reader, the above-referenced Table 2 is enclosed herein as Attachment 1, 

which provides radon flux data for the 48 silo locations in the units of (1) pCi/m2/sec and 

(2) pCi/cm/sec. 
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To illustrate these data, sample location #24 of the North Tank provides the following 

information (see Attachment 1):

 This sample location represented the highest measurement and involved a crack (c) that 

was sampled for 52 minutes.

 This resulted in an estimated areal flux (JA) of 2.8 (7) or 2.8 × 107pCi/m2/sec. This 

corresponds to 994 curies/m2/yr.

 When converted to a linear flux value (JL), the value 2.1 (4) or 2.1 × 104pCi/cm/sec was 

derived. This converts to a yearly release rate of 0.66 curies per cm length of the 

“undefined” crack.

With a dome cap diameter of 24 meters, representing 1,810 m2, it is clear that the flux data given 

in Attachment 1 have limited value for defining a collective source term for the silo. These 

feelings were shared by Hagee et al. 1985, who concluded the following:

The surfaces of the storage tanks represent a very discontinuous source. It is, 

therefore, virtually impossible to employ the measured flux values to infer a 

source term. The problem is compounded by the existence of severe radon 

release around most of the metal protrusions on top of the tanks which could not 

be measured by charcoal canister methods. [Emphasis added.]

SC&A concludes that the Hagee et al. (1985) study has limited relevance to silo conditions/radon 

releases prior to June 1979. Nevertheless, the data/observations are highly suggestive of far 

greater releases prior to June 1979, as explained in Section 4.0.
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4.0 DISCUSSION AND SUMMARY CONCLUSIONS

As briefly summarized above, over the years, investigators representing the Radiological 

Assessment Corporation (RAC) developed several models for estimating radon release quantities 

for discrete time periods. These time periods were defined by variations in silo contents and,

more importantly, by physical modifications, which attempted to mitigate radon releases to the 

environment.

In spite of model modifications involving select parameters over the years (see Exhibit 4), a

major limitation for all RAC models is the fact that all of the models principally derived radon 

release rates on (1) radon concentrations in the silo’s headspace and (2) the ventilation rate of 

air/radon in the silo headspace. In turn, RAC assumed that the driving force for the headspace 

ventilation rate was defined by the diurnal fluctuation in ambient temperature and associated 

buildup of pressure within the headspace during the day’s warming cycle, as given by the 

following statements:

 From pages 30–31 of Appendix J, RAC (1995):

The ventilation rate due to the daily temperature changes, λV, ∆T, is the fraction of 

the silo air exhaled due to the temperature changes per some unit time period, 

with units of (air changes) per time. Thus:

λV, ∆T = ∆V/Vo

where,

 ∆V = the increased volume per day caused by rise in 

head-space temperature

 Vo = the initial silo air volume

. . . it was concluded that the silos cannot hold any significant pressure and thus 

the increase in the temperature of the internal silo air resulted in the volumetric 

expansion of the air and the release of “excess” volume to the atmosphere.

In brief, the RAC models and their release estimates are based on the assumption that diurnal

environmental radon releases were defined by the thermal expansion and increased pressure 

within the silo’s headspace and the resultant release of the “excess” volume to the environment.

SC&A believes that this diurnal thermal expansion mechanism is likely to represent but a small 

fraction of the total radon releases from the K-65 silo. What the RAC models fail to address are 

the two-fold impacts on silo ventilation rates imposed by the Venturi effect induced by wind.
Draft White Paper – Fernald 15 SC&A – April 6, 2010 

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Exhibit 4: Table 8 from RAC 1998

4.1 THE ROLE OF WIND AND THE VENTURI EFFECT

In Section 4.0 of our previous White Paper dated November 2008, SC&A had concluded the 

following (SC&A 2008):

A serious deficiency of the RAC model is its failure to properly account for the 

Venturi effect that is likely to have dominated the release of Rn-222 from the silo 

headspace prior to June of 1979, when the silos were subjected to major sealing 

modifications. The Venturi effect would have the following impact: during 

periods of low to moderate winds, a steady flow of air over the curved smooth 

surface of the silo dome creates a partial vacuum (much like that over the leading 

edge of a forward-moving airplane wing that creates the necessary lift for flight). 
Draft White Paper – Fernald 16 SC&A – April 6, 2010 

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In essence, the wind-induced Venturi effect results in the reduction of atmospheric pressure over 

the external surface of the dome cap relative to the atmospheric pressure within the silo’s 

headspace. Under sustained steady wind conditions, this pressure differential not only induces a 

pressure-driven release of air from the silo’s headspace into the environment, but in time also 

results in a reduction of pressure within the headspace relative to the pressure within the waste 

material that is the radon source term. This secondary pressure differential between the 

headspace and silo waste material will also result in a pressure-driven migration of radon gas 

from the waste material into the dome’s headspace.

A review of the scientific literature related to radon in homes, buildings, and other man-made 

structures show that pressure-driven radon flow is the dominant mechanism. The EPA, in a 1987 

document entitled, Radon Reference Manual (EPA 1987), stated the following (from Chapter 8):

. . . Radon in the soil can enter the home through two gas transport mechanisms: 

molecular diffusion (movement from an area of high concentration to low 

concentration at constant pressure) and pressure-driven flow (movement from a 

high to a low pressure area). Scientific investigators have indicated that 

diffusion cannot account for the high levels of indoor radon, but rather, pressure 

differences between indoor and outdoor air seem to be the major determinant. 

Pressure-driven flow, where radon is actually drawn into the structure, is 

influenced by several factors. During the heating season, indoor temperatures

are often higher than outdoor temperatures, causing a tendency for warm indoor 

air to be displaced by cooler outdoor air. This tendency is called the stack effect 

since the warm air tends to rise as in a chimney. . . . Wind is another important 

factor that causes a pressure difference and drives the flow of radon . . . [and] 

open fireplaces also create a significant draw on indoor air. . . [Emphasis 

added.]

Based on the fact that the cylindrical dome-capped silos represent a configuration that is 

optimally affected by wind-induced pressure differentials, it is puzzling why the RAC model 

excluded this important radon release mechanism, even though its authors were fully aware of its 

potential role and stated the following in their 1995 report:

 From pages J-31 and J-32 of Appendix J of RAC 1995:

Since the silo can not hold any significant pressure, it is certainly plausible that 

the cracks and other remaining penetrations in the silo domes are large enough 

and numerous enough that additional ventilation of the silos occurs, due to winds

across the domes. For the present work, it is assumed that the silo ventilation is 

the sum of the ventilation rate due to the temperature effects and a ventilation 

rate due to wind effects. That is,

λV, post = λV, ∆T + λV, wind
Draft White Paper – Fernald 17 SC&A – April 6, 2010 

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However, the authors subsequently elected to ignore the potential contribution of wind-induced 

ventilation, as given on page J-34 of Appendix J:

As discussed earlier, it is plausible that the cracks in the silo domes are numerous 

enough and large enough that the action of winds on the domes could create 

additional ventilation in the silos, represented by λV, wind. However, no data have 

been found to substantiate an estimate of λV, wind. . . . Since additional 

information has not been located to substantiate a value for λV, wind, we now 

assume a value of zero. [Emphasis added.]

Furthermore, it must be noted that the above-cited comments/conclusion by the RAC authors in 

1995 post date the major remediation efforts of June 1979.

It is SC&A’s firm belief that prior to 1979, the wind/Venturi effect was likely the dominant 

mechanism for headspace ventilation and the release of radon to the environment.

 Support for high ventilation rates prior to June of 1979 and the role of the Venturi effect 

comes from the near-equal contact dose rate measurements taken on top of the dome 

before 1979 and after 1987 with the operation of the Radon Treatment System (see 

Exhibit 5). The following data points from Exhibit 5 illustrate our contention: 

 In May 1973, contact dose rate measurements on top of Silo 2 showed values between 

70–75 mrem/hr.

 In April 1980 (or post-1979 sealing of Silo openings), the contact dose rate on Silo 2 

increased to 200–250 mrem/hr.

 In November 1987, contact dose rate measurements for Silo 2 again showed similar dose 

rates of 221 to 250 mrem/hr with an average of 232 mrem/hr.

 In the same period (i.e., November 1987), contact dose rate measurements on top of 

Silo 2 were again taken. However, this time, dose rates were taken after the Radon 

Treatment System (RTS) had been activated. With the activation of the RTS, the dose 

rates were reduced to 60 to 76 mrem/hr, with an average of 68 mrem/hr.

Important to note is that the dose rate in May 1973 (at 70–75 mrem/hr) is essentially equal to the 

dose rates of 60–76 mrem/hr obtained in 1987 with the activation of the Radon Treatment 

System.

Appendix J of RAC 1995 described the Radon Treatment System, as follows (pages J-28 to 

J-29):

The RTS was operated . . . on one silo at a time, with a flow rate of about 1000 ft3

min-1, and was operated until radiation levels on [top of] the silo dome surface

[i.e., contact] stopped decreasing . . . With these flow rates and operating times, 
Draft White Paper – Fernald 18 SC&A – April 6, 2010 

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and an assumed removal efficiency close to 100%, the 222Rn concentrations in the 

silo air space should have been reduced to less than 3% of the initial 

concentrations. . . 

Thus, for this analysis, the exposure rate measurements made after operation of 

the RTS are considered to represent the “background” exposure rate, in the 

absence of 222Rn daughters in the silo air. [Emphasis added.]

From these statements contained in RAC 1995, the following conclusions must be drawn:

(1) The release rates of Rn-222 (and its short-lived daughters) varied greatly over time and 

reflect incremental modifications to the K-65 silos aimed to mitigate the releases of 

Rn-222.

(2) Undoubtedly the single most important modification for reducing radon releases was the 

sealing of multiple penetrations that included manhole covers, a 6-inch diameter 

gooseneck pipe, and large numbers of cracks in June of 1979.

(3) Contact dose rate readings on top of the silos prior to 1979 are essentially identical to the 

1987 contact dose rate readings taken after the operation of the RTS.

(4) Based on the relationship of the 1987 contact dose rate readings on top of the silo domes 

and reduced activity levels in silo headspace, the derived headspace ventilation rate prior 

to June 1979 can be assumed at 1.2/hour. Implicit in this assumption is that for years 

prior to 1980, there was little or no buildup of radon/radon daughters in the headspace of 

the K-65 silos as a result of unfettered radon releases to the environment.

(5) The enhanced emanation rate of Rn-222, from the contained waste into the silo’s 

headspace and the unconstrained release from the headspace into the environment, 

limits further decay and formation of Pb-210 within the waste material. Thus, the 

empirical observation of disequilibrium between Ra-226 and Pb-210 (as noted in 

Table 5-16 of ORAUT-TKBS-0017-5) supports SC&A’s contention of enhanced radon 

releases.

(6) Based on data presented in our previous White Paper and in this report, SC&A estimates 

that radon releases prior to 1980 were in excess of 100,000 Ci/yr from Silos 1 and 2.
Draft White Paper – Fernald 19 SC&A – April 6, 2010 

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Exhibit 5: Table J-19 from Appendix J of RAC 1995
Draft White Paper – Fernald 20 SC&A – April 6, 2010 

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REFERENCES

EPA (U.S. Environmental Protection Agency) 1987. Radon Reference Manual, EPA 520/1-87-

20. Office of Radiation Programs, Washington, DC. 

Hagee, G.R., P.H. Jenkins, P.J. Gephart, and C.R. Rudy, 1985. Radon and Radon Flux 

Measurements at the Feed Materials Production Center, Fernald, Ohio, U.S. Department of 

Energy, MLM-MU-85-68-001.

Hornung, R.W., Pinney, S.M., J. Lodwick, G. Killough, D.E. Brewer, and J. Nasuta, 2008. 

Estimation of Radon Exposure to Workers at the Fernald Feed Materials Production Center 

1952–1988, Journal of Exposure Science and Environmental Epidemiology, 1–12.

Killough, G.G. and D.W. Schmidt, 2000. Uncertainty Analysis of Exposure to Radon Released 

from the Former Feed Materials Production Center, Environmental Radioactivity, Vol. 49, pp. 

127–156.

NAS (National Academy of Sciences) 1994. Dose Reconstruction for Fernald Nuclear Facility: 

A Review of Task 4, National Research Council, National Academy Press, Washington, DC.

NIOSH (National Institute for Occupational Safety and Health), 2010. Transcript of Work 

Group on Fernald Site Profile and SEC. Cincinnati, Ohio. January 29, 2010.

ORAUT (Oak Ridge Associated Universities Team), 2004. Technical Basis Document for the 

Fernald Environmental Management Project (FEMP) – Occupational Internal Dose, ORAUTTKBS-0017-5, Rev. 00, ORAUT, Cincinnati, Ohio. 

RAC (Radiological Assessment Corporation) 1995. The Fernald Dosimetry Reconstruction 

Project, Tasks 2 and 2 Radiologic Source Terms and Uncertainties, prepared by Voilleque, P.G., 

K.R. Meyer, D.W. Schmidt, S.K. Rope, G.G. Killough, M. Case, et al., RAC Report No. CDC-5, 

Neeses, South Carolina.

RAC (Radiological Assessment Corporation). 1998. The Fernald Dosimetry Reconstruction 

Project, Task 6 Radiation Doses and Risks to Residence from FMPC Operations from 1951–

1988, prepared by Killough G.G., M.J. Case, K.R. Meyer, R.E. Moore, S.K. Rope, D.W. 

Schmidt, et al. (RAC) Report No. CDC-1. Volumes I and II (final report). Neeses, South 

Carolina.

SC&A (S. Cohen and Associated) 2008. An Alternative Assessment of Radon Releases from 

K-65 Silos. Draft SC&A White Paper. SC&A, Inc., Vienna, Virginia.
Draft White Paper – Fernald 21 SC&A – April 6, 2010 

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ATTACHMENT 1: TABLE 2 FROM HAGEE et al. 1985
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ATTACHMENT 1 (Continued)
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ATTACHMENT 1 (Continued)
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ATTACHMENT 1 (Continued)