EPA Air Docket A-98-49, Item II-B1-33; August 2014

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Consequence Assessment Review Summary for the

February 2014 Radiological Emission Release

at the Waste Isolation Pilot Plant

Executive Summary

In the immediate aftermath of a radioactive release, modeling is used to project the direction of the 

plume and the amount of potential exposure to the public. The Department of Energy (DOE) refers to 

this activity as consequence assessment. Shortly after the radiation release incident at the Waste 

Isolation Pilot Plant (WIPP), DOE conducted consequence assessment to estimate the extent of the 

release. Based on the source term measured by DOE in the several days after the event, the modeling 

indicated that the release was very low-level (with an effective dose equivalent [EDE] of < 1 mrem to 

the nearest population) and was largely confined to the Land Withdrawal Boundary (LWB), limiting 

exposure to the public. The initial modeling was corroborated by compliance modeling that indicated 

the release would result in annual exposure well below EPA’s National Emission Standards for 

Hazardous Air Pollutants (NESHAP) regulatory limit of 10 mrem annual dose to any member of the 

public. Subsequent environmental samples of air, soil and sediment indicate that levels of radioactivity 

were also very low, in line with the modeled concentrations and doses.

Background

The process for estimating potential effects of the February 14, 2014 radiation release at the WIPP is 

consequence assessment, which involves modeling of the release to the environment. DOE began 

developing consequence assessments on February 15 and updated them periodically until March 10. 

DOE subsequently did additional modeling and collected air and other environmental samples. The 

primary radionuclide released was americium-241. Plutonium-239 was a secondary radionuclide 

detected.

Station B collects effluent air samples downstream from the HEPA filtration system. These samples 

represent the radioactive materials and associated radiation released into the environment. The HEPA 

filtration of the mine exhaust prevented the majority of the contamination from reaching the 

environment; however, leakage within the ventilation system allowed a small amount of mine exhaust 

to bypass the HEPA filters and be released into the environment.

1 EPA is confident that Station B 

samples adequately represented the released radioactivity. DOE’s data indicate that about 99% of the 

release occurred within 24 hours, and most of that by 2 p.m. on February 15, 2014.

2

DOE’s Consequence Assessment Modeling 

Immediately following the incident, DOE conducted initial consequence assessments to estimate 

possible doses to workers and the public. The DOE Carlsbad Field Office (CBFO) asked the National 

 

1 Department of Energy. Accident Investigation Report: Phase 1: Radiological Release Event at the Waste Isolation Pilot 

Plant on February 14, 2014. Washington, DC: 2014. 

http://energy.gov/sites/prod/files/2014/04/f15/Final%20WIPP%20Rad%20Release%20Phase%201%2004%2022%202014_

0.pdf

2 U. Department of Energy (DOE). “February 14th, contamination release consequence assessment Rev.1” Data file, DOE, 

2014. Retrieved from http://www.wipp.energy.gov/Special/Modeling%20Results.pdf
EPA Air Docket A-98-49, Item II-B1-33; August 2014

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Atmospheric Release Advisory Center (NARAC) to model the release using the radioactivity 

information gathered at the Station B monitoring location and using local meteorological data. 

At the beginning of the event the wind was blowing toward the northwest, but shifted to the east on the 

morning of February 15. The NARAC modeled plume reflects the prevalent wind directions during the 

release, with the largest part of the release plume modeled as going to the northwest. The NARAC 

model indicated that both the lower plume concentration of 0.1 mrem dose contour and the larger 1 

mrem dose contour stayed within the LWB (these dose contours are described as “isodose” or “equal 

dose” curves in Figure 1). For comparison, the regulatory NESHAP limit for air emission is 10 mrem 

annual dose to any member of the public.

Compliance Modeling

In addition to the NARAC modeling, DOE also conducted air emissions modeling using an EPAapproved model, CAP88-PC, to confirm compliance with the NESHAP limit of 10 mrem annual dose. 

The CAP88-PC modeling projects the highest potential public exposure for the most exposed 

individual as less than 1 mrem (0.678 mrem) at the fence line in the northwest direction from the WIPP 

air exhaust shaft. Using the same model and information, EPA staff members were able to recreate 

DOE’s results3. In addition to being below the NESHAPs limits, the findings are also well below the 

requirements in 40 CFR Part 191, Subpart A, which sets annual dose limits to any member of the 

public of 25 mrem to the whole body and 75 mrem to any critical organ.

Environmental Data Consistent with Modeling

The low levels of environmental radioactivity projected by modeling are consistent with ambient air 

sampling data that were collected during and after the event. Table 1 lists the data from DOE’s ambient

air sampling4around the WIPP in the days immediately following the release (no air filters in the 

environmental sampling program were above the minimum detectable concentration, or MDC, after a 

week so the DOE data set is truncated in Table 1). Low but detectable levels of radioactivity were 

found only at the WIPP Far Field, WIPP East, WIPP South and Smith Ranch locations; this is what 

would be expected given the plume directions. DOE also did a soil collection transect in March 2014 

across the plume path and found no samples with americium or plutonium above detectable levels, 

save one duplicate for which the companion measurement was below the minimum detection 

concentration. 

Conclusion

Multiple lines of evidence indicate that the February 14, 2014 incident at the WIPP resulted in very 

low releases to the environment. Calculations indicate that the releases remain well below EPA’s 

NESHAP compliance requirement of 10 mrem annual dose limit. The evidence indicates that the 

release of radioactivity from the WIPP in February 2014 does not represent a public health concern.

 

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See EPA’s Confirmatory Dose Calculations of the Department of Energy’s Use of CAP88-PC for the February 2014 

Radiological Emission Release at the Waste Isolation Pilot Plant [EPA Air Docket A-98-49, Item II-B1-32; August 2014]

4 Vincent, Oba of the Department of Energy, email message to Tom Peake of the Environmental Protection Agency, June 

16, 2014. Subject: WIPP Information for call today.
EPA Air Docket A-98-49, Item II-B1-33; August 2014

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Figure 1. Initial estimate of radiation dose. The figure identifies the plume calculated by the NARAC 

for the period February 14-21, 2014. Note that the 0.1 mrem and 1.0 isodose (equal dose) modeled 

areas remain within the Land Withdrawal Boundary (LWB). Adapted from DOE’s February 14th

Contamination Release Consequence Assessment Revision 1, Figure 45.

 

5 Department of Energy (DOE). “February 14th

, contamination release consequence assessment Rev.1” Data file, DOE, 

2014. Retrieved from http://www.wipp.energy.gov/Special/Modeling%20Results.pdf

0.1 mrem isodose

1.0 mrem isodose
EPA Air Docket A-98-49, Item II-B1-33; August 2014

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Table 1. DOE’s Ambient Air Filter Analyses from On and Around the WIPP Site in the Days 

Immediately Following the Incident. The DOE data set below is truncated because no air filters in the 

environmental sampling program were above the minimum detectable concentration (MDC) after a 

week. Note that only four sampling locations had measurements above the MDC. The WIPP Far Field 

location and the Smith Ranch are located in the northwest direction of Figure 1 in the direction of the 

largest release.

Environmental Monitoring & Hydrology Airborne Particulates Sampling

* Filter volumes based on an adjusted filter installation date. This date was changed from the actual filter installation date to 

the date of the release which occurred at 23:30 hours on 2/14/14. Note: Minimum detectable concentration (MDC) 

corresponds to the lowest concentration measurement that can be detected by the laboratory instrumentation. MDC ranges 

are: MDC Am-241 (dpm/sample): 1.89E-02 to 5.05E-01; MDC Pu-238 (dpm/sample): 1.89E-02 to 1.57E+01; MDC Pu239/240 (dpm/sample): 1.70E-02 to 5.94E-0

Location

Sample ID 

Number Sample Date

ISOLO 

Spectrum

Analyzer

WIPP 

Labs 

Gross 

α 

DPM

WIPP Labs Radiochemistry WIPP Labs Radiochemistry

Gross α β

Preliminary/

Final DPM

Am-241

(dpm/sample)

Pu-238

(dpm/sample)

Pu-239/240

(dpm/sample)

Am-241

(Bq/m3)

Pu-238

(Bq/m3)

Pu-239/240

(Bq/m3)

WIPP Far 

Field (WFF)*

AL-WFF20140212-

1.1

02/15/2014 36 --- 4.88E+01 Below MDC 3.67E+00 1.58E-02 N/A 1.19E-03

WIPP Far 

Field (WFF)

AL-WFF20140219-

1.1

02/18/2014 2.4 --- 2.70E-01 Below MDC Below MDC 1.85E-05 N/A N/A

WIPP East 

(WEE)*

AL-WEE20140212-

1.1

02/17/2014 7.29/4.4 --- 5.73E-01 Below MDC Below MDC 4.57E-05 N/A N/A

WIPP South 

(WSS)*

AL-WSS20140212-

1.1

02/17/2014 7.47/3.7 --- 1.41E-01 Below MDC Below MDC 1.13E-05 N/A N/A

Mills Ranch 

(MLR)*

AL-MLR20140212-

1.1

02/18/2014 2.7 --- Below MDC Below MDC Below MDC N/A N/A N/A

Smith Ranch 

(SMR)*

AL-SMR20140212-

1.1

02/18/2014 4.2 --- 2.44E-01 Below MDC Below MDC 1.50E-05 N/A N/A

Carlsbad 

(CBD)*

AL-CBD20140212-

1.1

02/18/2014 1.6 --- Below MDC Below MDC Below MDC N/A N/A N/A

Southeast 

Control 

(SEC)*

AL-SEC20140212-

1.2

02/18/2014 1.3 --- Below MDC Below MDC Below MDC N/A N/A N/A

Southeast 

Control 

(SEC) colocated 

sample*

AL-SEC20140212-

2.2

02/18/2014 1.5 --- Below MDC Below MDC Below MDC N/A N/A N/A

WIPP Far 

Field (WFF)

AL-WFF20140219-

1.1

02/26/2014 --- 1.89 Below MDC Below MDC Below MDC N/A N/A N/A

WIPP East 

(WEE)

AL-WEE20140219-

1.1

02/26/2014 --- 2.48 Below MDC Below MDC Below MDC N/A N/A N/A

WIPP South 

(WSS)

AL-WSS20140219-

1.1

02/26/2014 --- 2.23 Below MDC Below MDC Below MDC N/A N/A N/A

Mills Ranch 

(MLR)

AL-MLR20140219-

1.1

02/26/2014 --- 2.57 Below MDC Below MDC Below MDC N/A N/A N/A

Carlsbad 

(CBD)

AL-CBD20140219-

1.1

02/26/2014 --- 2.23 Below MDC Below MDC Below MDC N/A N/A N/A

Smith Ranch 

(SMR)

AL-SMR20140219-

1.1

02/26/2014 --- 1.12 Below MDC Below MDC Below MDC N/A N/A N/A