Biota Dose Assessment Methods used at the Idaho National Engineering and

Environmental Laboratory

Biota Dose Assessment Methods used at the Idaho National Engineering and

Environmental Laboratory

Randall C. MorrisEnvironmental Science and Research Foundation101 S. Park Ave., Suite 2P.O. Box 51838Idaho Falls, ID 834-05-1838(208) 525-7053 morrisr@env.esrf.isu.edu

Robin VanHornLockheed Martin Idaho Technologies P.O. Box 1625Idaho Falls, ID 83415-3960(208) 526-8531rh9@inel.gov

PRESENTERS

Text slide: The Idaho National Engineering and

Environmental Laboratory (INEEL)

The INEEL is a Department of Energy facility established in 1949 for nuclear research and related activities. Today, research, training, and production activities related to defense and non-defense programs are conducted at the INEEL.

The INEEL occupies 2,300 km2 on the northwestern portion of the eastern Snake River Plain in southeastern Idaho. The Lost River, Lemhi, and Bitterroot mountain ranges border the INEEL on the north and west.

Elevation ranges from 1,460 m in the south to 1,650 m in the northeast, with the exception of the East (2,003 m) and Middle (1,948 m) Buttes.

Approximately 95% of the INEEL is controlled by DOE; the remaining 5% includes public highways and the Naval Reactors Facility (Department of Defense).

TEXT SLIDE: The Ecology of the INEEL

Cool desert ecosystem characterized by shrub-steppe vegetative communities.

Relatively, flat, with several prominent volcanic buttes and numerous basalt flows that provide important habitat for small and large mammals, reptiles, and some raptors.

Dominated by sagebrush; provides habitat for numerous fauna such as sage grouse, pronghorn, and sage sparrows. Rabbitbrush, grasses and forbs, salt desert shrubs, and exotic/weed species make up other communities. Since 1957, the central portion of the INEEL (approximately 1,385 km2 ) has been maintained as a grazing exclusion area.

In 1972 , the DOE established the INEEL as a National Environmental Research Park. It is the second largest of seven such Parks and is one of two which contain sagebrush-steppe ecosystems.

TEXT SLIDE: CERCLA Activities at the INEEL

In 1989, the INEEL was placed on the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) National Priorities List.

In 1991, the Federal Facility Agreement and Consent Order (FFA/CO [DOE-ID 1991]) was signed to establish a procedural framework and schedule for CERCLA activities at the INEEL. The FFA/CO divides the INEEL into 10 waste area groups (WAGs).

Within a WAG, the multiple sites of contamination are grouped by similar contamination problems or boundaries and are called operable units (OUs).

Sites range from large facilities to small rubble piles and include pits, percolation ponds, landfills, septic systems, injection wells, trenches, and abandoned tanks.

TEXT SLIDE: WAG DescriptionsTEXT SLIDE: WAG Descriptions

Test Area North - (WAG 1)

TAN, located at the northern end of the INEEL Site, consists of facilities for handling, storage, examination and research of spent nuclear fuel. TAN also houses a project to manufacture armor packages for Army tanks.

Test Reactor Area - (WAG 2)

TRA, the world's most sophisticated materials testing complex, houses extensive facilities for studying the effects of radiation on materials, fuels and equipment. The Advanced Test Reactor (ATR), located at TRA, produces a neutron flux that allows simulation of long-duration radiation effects on materials and fuels. ATR is also used for production of important isotopes used in medicine, research and industry.

TEXT SLIDE: WAG Descriptions (Continued)TEXT SLIDE: WAG Descriptions (Continued)

Idaho Nuclear Technology and Engineering Center - (WAG 3)

INTEC, houses facilities that provide safe interim storage for government-owned defense and research spent nuclear fuels. Other facilities at INTEC include a waste solidification facility and related waste storage bins, a state-of-the-art remote analytical laboratory and a coal-fired steam generating plant.

Central Facilities Area - (WAG 4)

CFA is where services for the entire site are headquartered. These services include environmental laboratories, security, fire protection, medical facilities, communications systems, warehouses, a cafeteria, vehicle and equipment pools, bus system and laundry.

TEXT SLIDE: WAG Descriptions (Continued)

Power Burst Facility and Auxiliary Reactor Area - (WAG 5)

PBF, is located in an area originally constructed for the Special Power Excursion Reactor Tests (SPERT). Four SPERT reactors were built beginning in the late 1950s. All of these reactors were removed and the SPERT facilities have undergone partial or complete D&D. The PBF reactor is still operational but is in a standby mode. ARA, consists of four groupings of buildings in which activities, including the operation of test reactors occurred. All ARA reactors were removed from the facility and have undergone partial or complete D&D.

PBF/ARA sites of concern include tanks and components of wastewater disposal systems (e.g., evaporation ponds, percolation ponds. Leach fields, pits, and dry wells).

TEXT SLIDE: WAG Descriptions (Continued)TEXT SLIDE: WAG Descriptions (Continued)

Radioactive Waste Management Complex - (WAG 7)

RWMC was established in 1952 as a controlled area for disposal of solid radioactive wastes generated in INEEL operations. Since 1954, the facility has also received defense wastes for storage and/or disposal from other sites. Currently, various strategies for waste storage, processing and disposal are studied at RWMC.

Naval Reactors Facility - (WAG 8)NRF is the birthplace of the U.S. Nuclear Navy.

Beginning in the early 1950s, prototype reactors for both submarines and surface ships were developed and operated here. Until May 1995 when the last prototype was shut down, NRF served as a training school for officers and enlisted personnel destined for service aboard nuclear-powered ships. As it has for nearly 40 years, NRF continues to receive and examine Naval spent fuel.

TEXT SLIDE: WAG Descriptions (Continued)

TEXT SLIDE: WAG Descriptions (continued)

Argonne National Laboratory-West - (WAG 9)

ANL-W, part of Argonne National Laboratory operated by the University of Chicago, conducts research and development and operates facilities for DOE. Research is typically focused on areas of national concern including those relating to energy, nuclear safety, spent nuclear fuel treatment, nonproliferation, decommissioning and decontamination technologies, nuclear material dispositioning and similar work.

TEXT SLIDE: WAG Descriptions

WAG 10, includes miscellaneous surface sites and liquid disposal areas throughout the INEEL that are not included within other WAGs. WAG 10 also includes regional Snake River Plain Aquifer concerns related to INEEL that cannot be addressed on a WAG-specific basis. This WAG will also perform the INEEL-wide ecological risk assessment.

INEEL ISSUESINEEL ISSUES

Multiple stakeholders – Approach and methodology developed

was a result of negotiation between DOE-ID, EPA Region Ten, and State of Idaho.

ERA guidance limited at that time Multiple CERCLA sites Multiple radionuclides (~ 160)

INEEL Guidance INEEL Guidance

Guidance manual (1995) documented– phased approach to ERA process– functional grouping method – method to address radionuclides and

nonradionuclides– pathways and routes of exposure identified– parameter values– ecologically based screening levels (EBSLs)

Phased ApproachPhased Approach

Applies an iterative, “tiered” process in which preliminary assessments based on conservative assumptions support progressively more refined assessments, at each WAG.

Phased Approach (continued)Phased Approach (continued)

1 Sites without potential exposure routes or pathways are eliminated,

2 contaminate concentrations at each site are compared to ecologically based screening values (EBSLs),

3 sites and/or contaminates remaining are assessed using more realistic modeling.

Functional GroupingFunctional Grouping

Functional groups should demonstrate:– Potential for contaminant exposure through

shared dietary and physical pathways (trophic and habitat parameters)

– Potential for similar biological response to that exposure (taxon).

Functional GroupsFunctional Groups

As defined, all species are potential surrogates for the other members of the same functional group. For assessment, parameters were integrated from several species to address the risk to the group as a whole.

Functional Grouping ExampleFunctional Grouping ExampleAV122

Rock dove(Columba livia) Aves 1 Columbiformes

Sage grouse(Centrocercus urophasianus) Aves 1 Galliformes

AV222

Western meadowlark(Sturnella neglecta) Aves 2 Passeriformes

Brewer's sparrow(Spizella breweri) Aves 2 Passeriformes

M122

Pronghorn(Antilocapra americana) Mammalia 1 Artiodactyla

Western harvest mouse

(Reithrodontomys megalotis) Mammalia 1 Rodentia

Black-tailed jackrabbit(Lepus californicus) Mammalia 1 Lagomorpha

M222

Merriam shrew(Sorex merriami) Mammalia 2 Insectivora

Northern grasshopper mouse

(Onychomys leucogaster) Mammalia 2 Rodentia

Functional Grouping MethodologyFunctional Grouping MethodologyTrophic category - "Primary" feeding habits (based on >50% of prey consumed).

1 Herbivore

2 Insectivore

3 Carnivore

4 Omnivore

5 Detritivore

Feeding habitat - "Primary" feeding habitat (based on location of >50% food or prey items). 1.0 AIR

2.0 TERRESTRIAL

2.1 Vegetation canopy

2.2 Surface/understory

2.3 Subsurface

2.4 Vertical habitat

3.0 TERRESTRIAL/AQUATIC INTERFACE

3.1 Vegetation canopy

3.2 Surface/understory

3.3 Subsurface

3.4 Vertical habitat

4.0 AQUATIC

4.1 Surface water

4.2 Water column

4.3 Bottom

Chronic Radiation Dose for Ecological Receptors

The International Atomic Energy Agency (IAEA) report on the Effects of Ionizing Radiation on Plants and Animals at Levels Implied by Current Radiation Protection Standards (IAEA 1992) was used as the basis for developing a dose.

Chronic Radiation Dose (Continued)

The IAEA (1992) technical report provides valuable information on the estimated doses to both plants and animals under current radiation protection standards for three different scenarios:

– controlled releases of radionuclides to the atmosphere,

– controlled releases of radionuclides to a freshwater aquatic system, and

– uncontrolled releases of radionuclides from a shallow land nuclear waste repository.

Chronic Radiation Dose (continued)

The IAEA (1992) determined – reproduction (including the processes from

gametogenesis through to embryonic development) is likely to be the most limiting end point in terms of population maintenance

– that irradiation at chronic dose rates of 1 mGy/day or less does not appear likely to cause observable changes in terrestrial animal populations

– that irradiation at chronic dose rates of 10mGy/day or less does not appear likely to cause observable changes in terrestrial plant populations.

Chronic Radiation Dose (continued)Chronic Radiation Dose (continued)

In 1995, the DOE Air, Water, and Radiation Division (EH-412) sponsored a workshop to evaluate the adequacy of the IAEA (1992) report as a basis for promulgating standards.

The workshop concluded that currently available data adequately supported the dose limits for plants and animals recommended by the IAEA.

Barnthouse, L.W. 1995. Effects of ionizing radiation on terrestrial plants and animals: A workshop report. ORNL/TM-13141, Environmental Sciences Division Publication No. 4494. Oak RidgeNational Laboratory, Oak Ridge, TN. 20 p.

BASIC ASSUMPTIONS

An acceptable chronic dose rate of 0.1 rad/day for terrestrial animal populations and 1 rad/day for terrestrial plant species (IAEA 1992) was assumed.

BASIC ASSUMPTIONS (Continued)

It was assumed that radionuclides emitting alpha and beta particles would not present a external dose risk since the basic rule of thumb (Shleien 1992) is that it requires an alpha particle of at least 7.5 MeV or a beta particle of at least 70 keV to penetrate a protective layer of skin (.07 mm thick). Therefore only the internal dose for these emitters was assessed. Gamma emitters can produce a dose rate to tissues from both external and internal exposure and were included in both assessments.

BASIC ASSUMPTIONS (Continued)

For terrestrial receptors (either plant or animal) the dose to reproductive organs from radionuclide contaminants is estimated by assuming it is equal to the internal radiation dose estimate, (calculated from the steady-state whole body concentration).

A quality factor of 20 was used for alpha emitters. Population effects were evaluated. The

assessment criteron was reduced by a factor of 10 to account for potentially greater risk to individuals.

Internal Dose Calculations for Ingestion

The equation of interest is:

Qx ADE x f CS x CF xSUF x ED x = DR

TEXT SLIDE: Internal Dose Calculations for Ingestion

where:DR = Internal radiation dose estimate (Gy/day);

CS = Concentration of contaminant in soil ingested (pCi/g)

CF = Concentration factor (unitless);

ADE = Average decay energy (MeV/dis);

FA = Fraction of decay energy absorbed (unitless). For ß or radiations the FA was set equal

to 1 (100%) and for the FA was set equal to .3 (30%);

ED = Exposure duration;

SUF = Site use factor;

f = unit conversion factor;

Q = Quality factor (a quality factor of 20 is

added for radiation).

Internal Dose Calculations for Water Ingestion

A simple differential equation was used to determine tissue concentration from ingestion of water.

where:

TC = tissue concentration (pCi/g tissue)

1 = decay constant physical (1/day)

2 = decay constant biological (1/day)

I = intake [(pCi/L)(L/g tissue-day)]

L = other loss (e.g.,urination) [(pCi/L)(L/g issue-day)].

dTC

dt I - (TC) - (TC) - L = 1 2

Internal Dose Calculations for Water Ingestion (continued)

Conservatively assuming L = 0 and solving for TC at equilibrium (i.e., dTC/dt=0) gives

TC = I

+ 1 2

Internal Dose Calculations for Water Ingestion (continued)

The daily ingestion rate of the radionuclide from water, I, is calculated as

where:

CW = concentration of the radionuclide in water pCi/L)

WI = water ingestion rate (L/d)

BW = body weight of receptor (kg)

f = unit conversion factor

f x BW

WI x CW = I

Internal Dose Calculations for Water Ingestion (continued)

So the tissue concentration (or steady state adsorbed dose) due to water ingestion is:

where the water ingestion (WI) for mammals and birds is found from allometric equations (EPA 1993).

f x ) + ( x BW

WI x CW = TC

21

External Dose Calculations

where

DR = dose rate (rad/day)

E = the average gamma energy per disintegration (MeV);

C = the concentration (mCi/cm3);

the density of the medium (g/cm3).

2.12EC

RD

TEXT SLIDE: BASIC ASSUMPTIONS (Continued)

The rule of thumb calculation for external dose is recommended to calculate the external dose to ecological receptors. This equation calculates the dose rate to tissue in an infinite medium uniformly contaminated by a gamma emitter (Shleien 1992).

This was conservatively assumed to be the dose to burrowing functional groups. Nonburrowing functional groups were assumed to be at 50% of

this exposure (a hemisphere).

Conceptual Site Model

Potential Food Web

Exposure Pathways of Contamination Migration Modeled Exposure Pathways of Contamination Migration Modeled

Supported by human health sampling– Surface and subsurface soil

uptake by plants uptake by animals

– Water Not modeled (primarily waste disposal ponds and

sewage lagoons)

– Groundwater not assessed

– Air pathways not assessed

Exposure Routes EvaluatedExposure Routes Evaluated

Ingestion– plants, animals, water, soil

Dermal– not assessed, are evaluating for use

during INEEL-wide ERA Inhalation

– not assessed, limited information is available to support this assessment.

ParametersParameters

Concentration factors (CFs), Exposure duration (ED), and home range– developed from existing literature, using

site specific and native species as possible

Ingestion rates were developed from allometric models

Calculation of Ecologically Based Screening Levels (EBSLs)

The dose equations can be manipulated to yield equations for an Ecologically Based Screening Level (EBSL)

TEXT FILE: EBSL for Internal Exposure

Qx FA x ADE x CF

f x TRV =EBSL

For internal exposure to soil the equation becomes:

TEXT FILE: EBSL for Internal Exposure (continued)

where:

EBSL = Ecologically based screening level for radionuclides in soil (pCi/g);

TRV = Toxicity reference value Gray/day);

CF = Concentration factor (unitless);

ADE = Average decay energy (MeV/dis);

FA = Fraction of decay energy absorbed (unitless);

Q = Quality factor.

TEXT FILE: EBSL for External Exposure

For external dose the equation becomes:

where

EBSL = Ecologically based screening level for radionuclides in soil (pCi/g);

D = the dose rate;

E = the average gamma energy per disintegration (MeV).

EBSL =D x

x E

10

212

6

.

EBSL ScreeningEBSL Screening

For CERCLA purposes EBSLs allowed screening of radionuclides as COPCs at all WAGs except two.– WAG 2 (Cs-134, Cs-137, Am-241, Pu

238/239, and Sr-90) at two sites– WAG 3 (Am-241, Co-60, Cs-137, Eu-152,

Eu-154, and Sr-90) at three sites

Current ActivitiesCurrent Activities

Comparing site specific CFs to those used in models

Developing INEEL-wide approach Air deposition modeling long term monitoring

Current Activities (ESRF)Current Activities (ESRF)

Revising dose calculations methods Surveys for sensitive species Proposed Big Lost River Sinks sampling Soil bioavailability studies

Current Activities (ESRF)Current Activities (ESRF)

Environmental monitoringEvans, R.B., R.W. Brooks, D. Roush, and D. Martin. 1998.

Idaho National Engineering and Environmental Laboratory site environmental report for calendar year 1997. ESRF-030, DOE/ID-12082(97). Environmental Science and Research Foundation, Inc. Idaho Falls, ID. 181 p.

Ecology and radioecology researchWeigmann, D.L. and R.D. Blew. 1999. Environmental

Science and Research Foundation, Inc. annual technical report to DOE-ID: Calendar year 1998. ESRF-033. Environmental Science and Research Foundation, Inc. Idaho Falls, ID. 100 p.

http://esrf.org

References

DOE-ID, (Department of Energy, Idaho Operations Office), 1991, Federal Facility Agreement and Consent Order for the Idaho National Engineering Laboratory, State of Idaho Department of Health and Welfare, U.S. EPA, U.S. DOE, December 4.

Environmental Protection Agency (EPA), 1993, Wildlife Exposure Factors Handbook, EPA/600/R-93/187a,b.

IAEA (International Atomic Energy Agency), 1992, Effects of Ionizing Radiation on Plants and Animals at Levels Implied by Current Radiation Standards, Technical Report Series No. 332.

References (continued) Shleien, B., 1992, The Health Physics and

Radiological Health Handbook, Scinta Publishers, Silver Springs, MD.

VanHorn, R. L., N. L. Hampton, and R. C. Morris, 1995, Guidance Manual for Conducting Screening Level Ecological Risk Assessments at the INEL, Idaho National Engineering Laboratory, Idaho Falls, ID, INEL-95/0190, April, 1995.

VanHorn, R.L., Hampton, N. L., and Morris, R.C. (1998) Methodology for Conducting Screening-level Ecological Risk Assessments for Hazardous Waste Sites. Part I. Overview. Int. J. of Environment and Pollution, Vol. 9, No. 1, 1998.

References (continued)References (continued) Hampton, N.L., Morris, R.C., and R.L. VanHorn

(1998) Methodology for Conducting Screening-level Ecological Risk Assessments for Hazardous Waste Sites. Part II. Grouping ecological components. Int. J. of Environment and Pollution, Vol. 9, No. 1, 1998.

Kester, J. E., VanHorn, R.L., and Hampton, N.L. (1998) Methodology for Conducting Screening-level Ecological Risk Assessments for Hazardous Waste Sites. Part III. Exposure and effects assessment. Int. J. of Environment and Pollution, Vol. 9, No. 1, 1998.

Morris, R.C. and VanHorn, R.L., 1999, Screening Risks to Terrestrial Vertebrates from Radionuclide Contamination in Soil and Water. Waste Management 99 Conference, Tuscon, Arizona.

Additional References Cember, H. 1983, Introduction to Health Physics,

(2nd Ed.) Pergamon Press. New York, NY. EPA, 1989, Risk Assessment Guidance for

Superfund, Vol. 1, Chapter 10, EPA/540/1-89/001. Kocher, 1981, Radioactive Decay Data Tables,

NTIS DOE-TIC-11026. National Council on Radiation Protection and

Measurements (NCRP), 1984, Radiological Assessment: Predicting the Transport, Bioaccumulation, and Uptake by Man of Radionuclides Released to the Environment, NCRP Report No. 76.

Additional References

Turner, J.E., 1986, Atoms, Radiation, and Radiation Protection, Pergamon Press, New York, N.Y.

Schulz, V. and F. W. Whicker, 1982, Radioecology: Nuclear Energy and the Environment. CRC Press, Inc., Boca Raton,FL.

Till, J.E. and Meyer, H.R., 1983, Radiological Assessment: A Textbook on Environmental Dose Analysis. NUREG/CR-3332.