|
Excerpt of Publication WDOH/ERS-96-1101
 NOTE: Figures 1 and 2 and
Appendix A do not appear in this on-line version of the report. In addition, the tables in
the Sample Results section have been reformatted from the original but the data is intact.
EXECUTIVE SUMMARY
This report summarizes results from a radiological survey of a sandy downstream section
of 100-D Island. It was conducted in September 1995 by staff from the Washington State
Departments of Health and Ecology with logistical support from the Pacific Northwest
National Laboratory and U.S. Department of Energy.
Historical data characterizing the distribution of discrete Co-60 contaminated
particles in this sandy downstream section was questionable. Signs that this section of
the island was frequented by fishermen was evident, and the potential for public radiation
exposure warranted the survey.
A walking survey of exposed island shoreline was conducted when river levels were at
their lowest. All surveys were performed using micro-R meters suspended approximately 2-4
centimeters above the ground. Background exposure rates along the river shore ranging from
7-8 microR/hr. were measured. A pressurized ion chamber (PIC) was used to measure
variations in background at three island locations. Ambient background measurements
recorded by the PIC varied from 8.8 - 9.5 microR/hr. Three discrete particles were
detected and contact measurements ranged from 85 - 2000 microR/hr.
Analytical results for radioactive and non-radioactive constituents are provided in the
report.
The survey of the downstream end of 100-D Island produced results that were consistent
with previous radiological surveys. The net results support a conclusion that Co-60
contaminated particles do not pose significant human health risks. Radiological posting
should be consistent with Hanford Contractor protocols since ownership of the island is
retained by the U.S. Department of Energy.
INTRODUCTION
There have been several field surveys focused on characterization of radioactivity in
D-Island sediments. Collectively, these surveys confirm a distribution of discrete Co-60
contaminated particles in the upper 15 centimeters of island sediments. Particle density
estimates range from 0.04 to 0.07 particles per cubic meter and contact exposure rates of
several hundred microR/h are not uncommon. Ambient exposure rates range from 6 to 8
microR/h.
In July 1995, the reliability and lack of data for a sandy downstream section of the
island was being debated within the Tri-Party Agreement. As a result, the Washington
Department of Ecology requested that the Department of Health conduct a radiological
survey of this section of the island. The survey was conducted by staff from the
Departments of Health and Ecology on September 18, 1995.
HISTORICAL OVERVIEW
The 100-D Island is located in the Columbia River approximately 250 meters offshore of
100-D Area. [Figure 1, a map of 100-D Island and Survey Area appears in the hard copy] It is a low-lying island that becomes partially submerged
due to daily fluctuations in the river level. Most of the 25-acre island is covered by a
layer of sediments predominated by cobbles, 1 to 6 inches in diameter, and coarse sandy
gravel. Sediments grade to coarse sands where slack-water condition exists as evidenced by
a coarse sandy beach located on the downstream end of the island. Vegetation, present on
the higher elevations of the island, consists of grass, small bushes and a few small
trees.
The D-Reactor cooling water discharge line extends from an outfall on the south bank of
the Columbia River and runs underneath the upstream end of D-Island. As designed, water
was held in a retention basin to allow thermal cooling and decay of short-lived
radioactivity before it was discharged to the center of the river.
The D-Island discharge line was physically and radiologically characterized in 1984 as
part of the decommissioning process (UNC, 1986). In 1990, as part of a site cleanup and
surveillance effort, the D-Reactor effluent line vents became an issue. The vents, which
became exposed during low river flow, are a potential source of contamination. A decision
was made to remove and plug the vent pipes to prevent potential public exposure and/or
release of contamination. Part of the vent pipe removal project was to survey the area to
find any contamination which had escaped through the vents. Approximately 1/2 of the
upstream end of the island was surveyed in 1993 using the USRADs system (Wade and Wendling
1994). Contamination consisted almost exclusively of discrete radioactive particles of
Co-60.
In June 1995, the issue of radioactive contamination on D-Island was being debated
within the Tri-Party Agreement (D-Island DQO Process Summary, 1995). At issue was the
adequacy of existing data to characterize the distribution of discrete radioactive
particles on a sandy downstream section of the island. This sandy section is submerged
during periods of normal river flow and is exposed during periods of low flow. Evidence
confirms this section is frequented by fishermen. Although access is not controlled, it is
closed to the public.
Due to a potential for public exposure, the Department of Health was asked to perform a
radiological survey of this section of the island. The purpose of the survey was to
determine the distribution of radioactive particles to justify radiological posting, thus
minimizing the probability of human exposure.
A radiological survey plan for the exposed sandy downstream shoreline was prepared by
the Department of Health and distributed to all participants. A conceptual summary of the
Department's plan follows:
- A walking survey of exposed shoreline will be conducted when river levels are at the
lowest. Surveys would be conducted along two paths parallel to the water line.
- Three five-by-five meter survey plots would be established and directly surveyed for
discrete particles. Results would be compared with particle density measurements made by
previous surveys. Several 20 to 40 centimeter deep excavations in the sandy area would be
made to look for buried discrete particles.
- All surveys would be performed using calibrated micro-roentgen meters (microR meter) and
micro-rem meters (microRem meter) held approximately 2-4 centimeters above the ground. A
calibrated count rate meter (GM meter) would be used to help locate a discrete particle in
the sediment matrix. Instrument readings along survey lines would be visually averaged
over 100 meters and recorded.
- A pressurized ionization chamber (PIC) would be utilized to provide an accurate
measurement of the external gamma exposure rates at several island locations. The PIC can
measure external gamma radiation at normal background levels with a precision in the range
of » 1microR/h.
- A global positioning device would be used to document the location of all samples and
surveys.
- Variations in field conditions would justify plan revision.
INSTRUMENTS
Instruments, such as microR meters, microRem meters and the pressurized ion chambers
(PIC), were selected on the basis of their reliability, ability to detect small amounts of
radioactivity, and operational convenience in field situations. The PIC, an integrating
instrument, measures the total dose over a given time span. It is a heavy, bulky
instrument comprised of two main components: the electronics and a pressurized gamma ion
chamber capable of measuring ambient radiation levels with a precision of » 1microR/h.
Portable instruments, like the microR and microRem, are rate meters that continuously
measure fluctuations in exposure and dose per unit time.
The relative sensitivities of each instrument to various gamma energies are illustrated
in Figure 2 [Figure 2 appears in the hard copy] (Thatcher 1995).
The NaI (sodium iodide) detector in the microR meter is very efficient and most sensitive
to gamma energies of approximately 50 keV to 700 keV. This property makes it an ideal
instrument for conducting walking surface scans and taking environmental grid point
measurements. In general, the microRem meter is the portable equivalent of the pressurized
ion chamber (PIC) and provides accurate dose rate measurements over a wide range of gamma
ray energies. The under response of the PIC, below 70 kev, is attributable to the
attenuation of low energy gamma radiation by the metal casing surrounding the ion chamber.
RESULTS AND DISCUSSION
The PNNL Surface Environmental Surveillance Project provided a boat and driver to
transport the survey team to the northeast (downstream Hanford side) side of 100-D island.
The river flow was very low, exposing a small area of eurasian milfoil. A sizable section
of sandy beach and low-lying gravel bar on the downstream end of the island was revealed.
The microR meter survey was conducted by two surveyors walking parallel paths along the
water line perimeter of the downstream end of the island. Instruments were suspended at a
height of 2-4 centimeters above the ground surface and two passes were made while the
river was at its lowest level. The second pass was made at 2-5 meters inland from the
waters edge. As the water level in the river began rising, the survey continued inland
from the shore until all of the low-lying area was surveyed (See shaded area on map -
obtainable from hard copy). Special attention was given to the
sandy beach (approximately 20 by 100 meters) and was surveyed in detail using a 1 meter
grid pattern.
Measurements were recorded by averaging exposure rate fluctuations over each 100 meters
surveyed. Instruments were operated in the "audio mode" enhancing the surveyors
ability to detect subtle changes in the exposure rate. The microR survey results were
quite consistent, ranging from 8.5 - 9.5 microR/h and no areas of elevated exposure rates
were detected, except where discrete particles were located. Typical background exposure
rates along the river shore range from 7-8 microR/h.
A pressurized ion chamber (PIC), mounted on a tripod approximately 1 meter above the
terrain, was used to measure variations in exposure rate at three island locations
(Reference Map for Locations [appears in the hard copy]). It was
set to collect a data point every 15 seconds, internally average data points and, generate
an average exposure rate. Data collected for 1.5 hours on the sandy beach section of the
island averaged 9.5 microR/h. Measurements generated in the middle of an area dominated by
coarse gravel and cobble sediments averaged 9.0 microR/h over a 1.2 hour time span. A
third location, on the north shore of the island, averaged 8.8 microR/h over the same
interval.
In addition, three 5 by 5 meter plots were selected at the downstream end of the
island. These were surveyed for discrete particles using a tight grid pattern to compare
with particle densities measured by previous surveys.
Three discrete particles were detected during the survey. A microR meter and GM pancake
probe were used to define the general location of each particle in the sediments and a
trowel was used to separate the particle from the cobbles and gravel. All particles were
isolated in the coarse sand fraction of island sediments and collected in individual
sample containers.
- Particle #1: This particle was found on the north side of the island. The shoreline in
this area is comparatively sloped and appears to be at or near the high water mark. A
surface exposure rate of 30 microR/h was measured and the particle was found about 10 to
15 centimeters below grade. A contact reading of 700 microR/h on the isolated particle was
indicated.
- Particle #2: This particle was found in a relatively flat area, just north of the sandy
beach, and is intermittently exposed by fluctuations in the river level. A surface
exposure rate of 20 microR/h was measured and the particle was found about 5 to 10
centimeters below grade. A contact reading of 2000 microR/h on the isolated particle was
indicated.
- Particle #3: This particle was found in one of the 5 by 5 meter plots, near the center
of an intermittently exposed flat area on the downstream end of the island. A surface
exposure rate of 20 microR/h was measured and the particle was found about 5 centimeters
below grade. A contact reading of approximately 85 microR/h was indicated on the isolated
particle.
All of the discrete particles recovered were sent to the Department of Health
office in Olympia to be analyzed by gamma spectroscopy. The gamma spectrum indicated only
the presence of Co-60. A micro-rem meter was used to provide a measure of the dose rate on
the discrete particles recovered. Quantitative measurements were not performed.
Two shallow pits were excavated to a depth of 30 to 40 centimeters to search for
particles at depth and measure sub-surface radiation levels. The first, in an area near
the location of particle #2, a maximum exposure rate of 11microR/h was measured. The
second, excavated in the sandy beach area, indicated a radiation level of 20 microR/h and
a soil sample was collected for analysis. This sample was split and fractions sent to the
Department of Health Radiation Laboratory in Seattle and the Department of Ecology
contract laboratory.
SAMPLE RESULTS
Analytical results for radioactive and nonradioactive constituents are summarized in
the tables below. Average background concentrations for various constituents are presented
for purposes of comparison. Radiological and non-radiological values reported are
consistent with typical concentrations measured in offsite soil. Zinc (230 mg/kg) was the
only metal reported that was higher than mean background. The zinc value reported is less
than the maximum value (366 mg/kg) used to calculate the mean and is within the range of
observed background values seen in the Yakima Basin.
Concentration of Radionuclides in 100-D Island Soil
(pCi/g » 2 sigma counting error)
| Nuclide | Health Lab | Ecology Lab | PNNL Lab* |
| Co-60 | 1.6 E-01» 0.16E-01 | 1.57 E-01 » 0.37 E-01 | NR |
| Cs-137 | 6.61 E-01 » 0.39E-01 | ND | 3.9 E-01 » 1.3 E-01 |
| Eu-152 | 2.75 E-01 » 0.45 E-01 | ND | NR |
| Eu-154 | 3.2 E-02 » 2.4 E-02 | ND | NR |
| Gross Beta | 1.93 E+01 » 0.25 E+01 | 2.62 E+00 » 0.51 E+00 | NR |
| Sr-89 | NA | <1.5 E-00 | NR |
| Sr-90 | 5.0 E-03 » 3.0 E-03 | <7.1 E-01 | 7.9 E-02 » 1.9 E-02 |
| Tc-99 | 3.8 E-01
» 1.4 E-01 | NA | NR |
| Gross Alpha | NA | 2.45 E+00 » 0.45 E+00 | NR |
| Pu-238 | 8.9 E-03 » 3.2 E-03 | NA | NR |
| Pu-239 | 1.14 E-02 » 0.37 E-02 | NA | 8.4 E-03 » 3.0 E-03 |
| Total Uranium | 1.2 E+00 » 0.1 E+00 | 5.89 E+00 » 0.79 E+00 | 7.1 E-01 » 1.4 E-01 |
* Offsite averages reported in the Hanford Site Environmental Report for Calendar Year
1993
NA - Not Analyzed
ND - Not Detected
NR - Not Reported
METALS ANALYSIS OF 100-D ISLAND SOIL
(mg/kg)
Department of Ecology Contract Laboratory
| ANALYTE | 100-D ISLAND | YAKIMA BASIN BACKGROUND |
| Aluminum | 5100 | 37,200 |
| Antimony | ND | NM |
| Arsenic | 3 | 5 |
| Barium | 40 | NM |
| Beryllium | ND | 2 |
| Cadmium | ND | 1 |
| Calcium | 2800 | NM |
| Chromium | 12 | 38 |
| Cobalt | 5 | NM |
| Copper | 18 | 27 |
| Iron | 13,000 | 51,500 |
| Lead | 17 | 11 |
| Magnesium | 3900 | NM |
| Manganese | 150 | 1100 |
| Mercury | ND | 0.05 |
| Nickel | 14 | 46 |
| Potassium | 600 | NM |
| Selenium | ND | NM |
| Silver | ND | NM |
| Sodium | ND | NM |
| Thallium | ND | NM |
| Vanadium | 22 | NM |
| Zinc | 230 | 79 |
ND - Not Detected
NM - Not Measured
CONCLUSION
The survey of the downstream end of the 100-D Island produced results that were
consistent with previous radiological surveys.
- 1978 - Pacific Northwest Laboratory (Sula, 1980) conducted a radiological survey of
D-Island to determine the distribution and density of radioactive particles and measure
ambient exposure levels.
- Aerial surveys of Columbia River shoreline and island areas were conducted by EG&G
Inc of Las Vegas in 1973-74, 1978 and 1988 (Tipton 1975, EG&G 1982, EG&G 1990).
- 1992 - The Pacific Northwest Laboratory (Cooper and Woodruff 1993) surveyed the islands
and flood plains along the Hanford region of the Columbia River for radioactive and
non-radioactive contamination.
- 1993 - Bechtel Hanford Company (Wade and Wendling, 1994) surveyed approximately 1/2 of
the upstream end of D-Island utilizing USRAD equipment.
The ambient gamma radiation level measured at several island locations was near
background. Burial depth and contact radiation levels of excavated discrete particles were
within the range of values previously reported. No particles were found on the sandy
downstream section of the island.
A rough estimate of particle density can be calculated using this survey data. For this
survey, three, 5 by 5 meter plots were surveyed in which one particle was found. All
particles were found at an average of 10 centimeters below grade, yielding a total of 7.5
cubic meters of sediment. Thus, the number of particles per unit volume is 1.3 x 10-1
particles per cubic meter. It should be noted, this figure is roughly double the particle
density estimates of other studies and is clearly biased due to sample size.
Radiological hazards and potential health effects from exposure to Co-60 particles on
this downstream section of D-Island are consistent with evaluations documented in previous
correspondence and reports.
- 1994 - The Washington State Department of Health (Wells, 1994) publishes: Special Report
- Radioactivity in Columbia River Sediments and Their Health Effects. This document
summarizes previous radiological surveys and evaluates the health effects from exposure to
residual radioactivity.
- 1994 - Letter to the Environmental Protection Agency. This letter provides a risk
assessment of human exposure to Co-60 contaminated metallic specks in Columbia River
sediments. A copy of this letter is included in Appendix A [of the hard
copy report].
The net results from this survey support a conclusion that Co-60 contaminated particles
in downstream D-Island sediments do not pose significant human health risks. Radiological
posting should be consistent with Hanford Contractor protocols since ownership of the
island is retained by the US Department of Energy.
REFERENCES
- Beckstrom, J.F. and J.M. Steffes. April 1986. River Discharges Lines Characterization
Report, UNI-3262, UNC Nuclear Industries, Richland, Washington
- Cooper, A.T. and R.K. Woodruff. September 1993. Investigation of Exposure Rates and
Radionuclide and Trace Metal Distributions Along the Hanford Reach of the Columbia River,
PNL-8789, Pacific Northwest Laboratory, Richland, Washington
- Cooper, A.T. February 1995. Measurements of Environmental Radiation Exposure Rates from
Vernita, Hanford Reach, and Richland Area Shores, PNL-8789, Addendum 1, Pacific Northwest
Laboratory, Richland, Washington
- DOE. August 1995. 100-D Island Discrete Radioactive Particles Data Quality Objectives
Process Summary, U.S. Department of Energy, Richland, WA
- EG&G. 1982. An Aerial Radiological Survey of the U.S. Department of Energy's Hanford
Site. EGG-1183-1828, EG&G Energy Measurement Group, The Remote Sensing Laboratory, Las
Vegas, Nevada
- EG&G. 1990. An Aerial Radiological Survey of the Hanford Site and Surrounding Area.
EG&G-10617-1062, The Remote Sensing Laboratory, EG&G Energy Measurements, Las
Vegas, Nevada
- EG&G. 1975. An Aerial Radiological Survey of the U.S. Energy Research and
Development Administration's Hanford Reservation (Survey Period: 1973-1974).
EG&G-1183-1661, EG&G, Inc, Las Vegas, Nevada
- NCRP. 1989 Limit for Exposure to Hot Particles on the Skin, NCRP Report No. 106,
National Council on Radiation Protection Measurements, Bethesda, Maryland
- PNL. 1994. Hanford Site Environmental Report for Calendar Year 1993, PNL- 9823, Pacific
Northwest Laboratory, Richland, Washington
- San Juan, Charles. 1994. Natural Background Soil Metals Concentrations in Washington
State. Washington Department of Ecology 94-115, Toxics Cleanup Program, Olympia,
Washington.
- Sula, M.J. 1980. Radiological Survey of Exposed Shorelines and Islands of the Columbia
River Between Vernita and the Snake River Confluence, PNL-3127, Pacific Northwest
laboratory, Richland, Washington
- Thatcher, A.H., May 1995, 100-N Area Shoreline Radiation Survey and Dose Evaluation,
Washington State Department of Health, Office of Radiation Protection, Olympia,
Washington
- Tipton, W.J. April 15, 1975. An Aerial Radiological Survey of the U.S. Energy Research
and Development Administrations Hanford Reservation, EG&G-1183-1661, EG&G, Inc,
Las Vegas, Nevada
- Wade, C.D., and M.A. Wendling. 1994. 100-D Island USRADS Radiological Surveys
Preliminary Report - Phase II, BHI-00134, Bechtel Hanford, Inc., Richland, Washington
- Wells, D., March 1994, Radioactivity in Columbia River Sediments and Their Health
Effects, Washington State Department of Health, Office of Radiation Protection, Olympia,
Washington
Authors and Acknowledgements
The authors of the 100-D ISLAND RADIOLOGICAL SURVEY report, Publication
WDOH/ERS-96-1101, are R. Allan Danielson and Richard Jaquish. The report was published
November 1996.
ACKNOWLEDGEMENTS
- Drew Thatcher, WDOH
- Sandi Green, WDOH
- Dave Holland, WDOE
- Jerry Yokel, WDOE
- Randy Brich, USDOE
- Dana Ward, USDOE
- Roger Dirkes, PNL
- Larry Belt, PNL
- Bruce Markes, RFS
For technical information contact Debra McBaugh,
Head, Environmental Radiation Section.
For full copies of this and
other
environmental reports contact Eileen Kramer.
DOH
Home
| Access Washington |
Privacy
Notice |
Disclaimer/Copyright
Information
|
