ML20211C691
| ML20211C691 | |
| Person / Time | |
|---|---|
| Site: | 07000824 |
| Issue date: | 01/31/1987 |
| From: | BABCOCK & WILCOX CO. |
| To: | |
| Shared Package | |
| ML20211C660 | List: |
| References | |
| RDD:87:8604-01:, RDD:87:8604-1:, NUDOCS 8702200181 | |
| Download: ML20211C691 (54) | |
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1 FINAL REPORT DECONTAMINATION AND DECOMMISSIONING OF BUILDING C AT LYNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA REPORT NUMBER:
RDD:87:8604-01:03 JANUARY 1987 l
l BABCOCK & WILCOX Lynchburg Research Center Lynchburg, Virginia g22fD C
o FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE OF CONTENTS SECTION PAGE
1.0 INTRODUCTION
1.1 Statement of the Problem 1-1 1.2 Statement of the Objective 1-1 1.3 Organization of this Report 1-2 2.0 IDENTIFICATION OF PREMISES 2.1 Site Description 2-1 2.2 Building C Physical Description 2-1 2.3 Definition of Phase 3 2-1 2.4 History of Operation of Phase 3 2-2 3.0 DECONTAMINATION OPERATIONS 3.1 Preparation of Rooms for Decontamination 3-1 3.2 Decontamination of Pipe and Duct 3-1 3.3 Decontamination of Room Surfaces 3-2 3.4 Drainline Removal 3-2 3.5 Soil Excavation 3-3 3.6 Decontamination of Building Exterior 3-3 3.7 Waste Disposal 3-4 4.0 SURVEY DESIGN AND PROCEDURES 4.1 Applicable Release Limits 4-1 4.2 Survey Design 4-2 4.2.1 Surface Survey Design for Use Areas 4-2 4.2.2 Surface Survey Design for Non-use Areas 4-3 4.2.3 Exterior Surface Survey Design 4-3 4.2.4 Survey Design for Equipment 4-3 4.2.5 Soil Survey Design 4-4 4.2.6 Ambient Gamma Radiation Survey Design 4-4 4.3 Survey Instruments 4-5 4.3.1 Surface Survey Instruments 4-5 4.3.2 Instruments used for Additional Gamma Survey 4-6 4.3.3 Soil Survey Instrument 4-6 l
4.4 Survey Procedures 4-6 1
4.4.1 Surface Surveys for Use Areas 4-6 i
4.4.2 Surface Surveys for Non-use Areas 4-7 l
4.4.3 Exterior Surface Survey 4-8 4.4.4 Equipment Survey 4-8 l
I-1
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 4.4.5 Soil Surveys 4-8 4.4.6 Ambient Gamma Radiation Survey 4-10 5.0 PHASE 3 SURVEY RESULTS 5-1 5.1 Surface survey 5-1 5.1.1 Initial Surface Surveys 5-1 5.1.2 Final Surface Surveys 5-2 5.2 Release Soil Survey 5-2 5.2.1 Background soil Survey 5-2 5.2.2 Excavation Release Survey 5-3 5.2.3 Drummed Soil Survey 5-3 5.3 Ambient Gamma Radiation Survey 5-4 6.0 SURVEY INTERPRETATION 6-1
7.0 REFERENCES
7-1 APPENDIX I-2
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C LIST OF TABLES Table Page 4-1 Acceptable Surface Contamination Levels 4-11 4-2 Building C Soil Release Limits and Building C External Gamma Exposure Limit.
4-12 4-3 LRC Technical Procedures Used for Building C Decommissioning Operations 4-13 5-1 Original Average Direct Alpha Survey Results 5-5 5-2 Original Direct Alpha Survey Results 5-6 5-3 Alpha Smear Survey Results 5-7 5-4 Final Average Direct Alpha Survey Results 5-8 5-5 Final Direct Alpha Survey Results 5-9 5-6 Summary of Release Direct Beta and Gamma and Smearable Beta Survey Results for 287 Floor Grid Blocks in Phase 3 5-10 5-7 Analyses of Background Soil Samples 5-10 5-8 Acceptance Limits for the Background Soil Activities 5-11 5-9 Analyses of Ditchface Release Soil Samples 5-11 5-10 Analyses of Drummed Soil Samples 5-12 I-3 l
7 FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 1
LIST OF FIGURES Figure Page 2-1 Babcock & Wilcox Property - Mount Athos 2-3 2-2 Lynchburg Research Center Plan of Buildings 2-4 2-3 Building C - Construction History 2-5 2-4 Building C - Floor Plan With Phase Boundaries 2-6 3-1 Building C - Phase 3 Hot Drain System 3-5 3-2 Phase 3 Excavation Locations 3-6 4-1 Typical Surface Grid Arrangement 4-15 5-1 Ambient Gamma Radiation Levels, nR/ hour on the Grounds and Roof of Building C 5-13 5-2 Ambient Gamma Radiation Levels, nR/ hour on the Grounds and the Interior of Building C 5-14 I-4
v FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C
1.0 INTRODUCTION
i 1.1 Statement of the Problem The Babcock & Wilcox Company (B&W), a wholly owned subsidiary of McDermott International, Inc., holds NRC License j
SNM-778 (1) to conduct operations involving SNM at its Lynchburg Research Center (LRC) near Lynchburg, Virginia.
Under this 4
license, research and development on thoria, urania, and plutonia nuclear fuels were performed in Building C at the LRC.
. A corporate decision was made in 1982 to discontinue R&D activities with radioactive materials in Building C.
B&W, in ceasing licensed activities in Building C, is complying with the i
license requirement as stated in Appendix F of SNM-778 to provide for decontamination of this building to protect the environment and the general public from exposure to levels of radioactivity i
in excess of those permissible.
Decontamination means the removal or reduction of radioactivity from buildings, walls, floors, and equipment and removal of radioactively contaminated i
soil contiguous with the building.
i A decommissioning plan (2) for Building C was submitted to the NRC for information purposes.
Decommissioning means action taken that results in the facility or a portion thereof being restored and reused for non-nuclear projects.
Decommissioning includes the act of decontamination.
The decommissioning plan divided work ~into three phases with a different section of the building being decontaminated in each phase.
This report addresses the results of the decontamination performed in the third and final phase.
Phase 1 and Phase 2 were reported earlier.
See references 5 and 6 respectively.
1.2 Statement of the Objective The principal objective of the decommissioning project is to obtain NRC concurrence that the building has been decontaminated, enabling the restoration and reuse of the facility for non-i nuclear purposes according to the criteria specified in Appendix i
F of SNM-778.
To assure adequate standards of quality were maintained in achieving this objective, work was performed accordin.g to QA Plan NO. 82008L (3).
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The decontamination included the interior and exterior surfaces of Building C and the underlying soil.
Table F-1 of Reference 1 establishes numerical limits for surface i
contamination within the facility.
Additional numerical limits for external exposure and soil remaining under Building C are contained in Reference 4.
B&W used these limits as minimum goals to achieve during decontamination, and followed the principle of l'
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FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C reducing contamination to ALARA levels (As Low As Reasonably Achievable).
The objectives have been achieved in three sequential phases as described in Reference 2.
1.3 Organization of this Report This report contains seven sections that describe the decommissioning work performed during Phase 3 of the Building C project.
Following this introductory section, a physical description of the site and Building C is provided.
Information is provided in Section 3 about the decontamination and decommissioning operations for Phase 3. The fourth section contains descriptions of the survey design and survey procedures and instrumentation used to determine radioactivity in, under, and around the building.
Sections 5 and 6 provide the results and data interpretation of the surveys.
The final section lists the documents referenced in this report.
The Appendix provides additional information relevant to Phase 1.
1-2
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C S
2.0 IDENTIFICATION OF FREMISES 2.1 Site Description The Lynchburg Research Center (LRC) is located near the James River about 4 miles east of Lynchburg, Virginia.
The site lies within Campbell County and borders on Amherst County.
Of the 525 acres at this location, only 13.6 acres are utilized by the LRC.
Other major B&W facilities on the site are the Naval Nuclear Fuels Division and the Commercial Nuclear Fuels Plant.
Figure 2-1 shows the site property boundary and the locations of the separate facilities on the site.
The LRC is a highly integrated facility built to develop, test, and examine nuclear reactor cores and to develop overall nuclear fuel cycles.
The location of Building C is shown in Figure 2-2 relative to the other buildings comprising the LRC.
2.2 Building C Physical Description The existing structure known as Building C is the result of several additions to a cmall laboratory completed in 1962 (see Fig.
2 3).
Building C is a single story building of concrete block construction with outside dimensions of 225 feet by 174 feet at its greatest width.
There is a small basement under one of the laboratories and two waste tanks under another.
The building contains about 24,000 square feet of laboratory, office, and support space.
There were approximately 10,250 square feet in the laboratories which had suitable bench scale and pilot plant equipment, ventilation, and personnel protection equipment for the handling of radioactive materials.
There was sufficient office space to house up to 38 technical, support, and supervisory personnel.
The building also contains two vaults formerly used for storage of SNM, a mechanical equipment room containing a boiler, compressed air, chilled water supply, and HVAC (heating, ventilation and air conditioning) systems, and a laundry.
There was a large storeroom that served the entire LRC.
Finally, Building C contains the exhaust fan and stack that serves adjacent Building B as well as Building C.
I 2.3 Definition of Phase 3 Phase 3 includes former Laboratories 19 and 20 located in the center of the building which were used primarily for analytical chemistry projects on plutonium fuels, two waste tanks under Lab 19, two vaults adjacent to Labs 19 and 20, l
Hallway 24, a part of Hallway 23, change rooms for men and women, ventilation equipment penthouses, the janitors closet, and two offices, a hallway and the main entrance of the building.
The Mechanical Equipment Room, the Fire Equipment Room near the main entrance, the Fan Room and Laundry Room are also included in 2-1
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- i FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C Phase 3.
The exhaust fans and stack continue to provide ventilation for Building B, but the Building C exhaust system was shut down and removed.
These areas occupy about 8,000 square feet.
Figure 2-4 shows the areas included in each phase.
Additionally, the loading dock and ramp, the enclosed storage area at the loading dock, all exterior walls and the roof are included in Phase 3.
2.4 History of Operation of Phase 3 Laboratories 19 and 20 were constructed as part of the 1968 expansion.
These two rooms were used primarily for chemical analysis of uranium and plutonium compounds in support of the FFTF program.
Laboratory 19 contained gloveboxes where wet chemical analyses were performed.
Laboratory 20 contained walled cubicles used as a darkroom, as an x-ray laboratory, and to house an emission spectrograph.
Laboratory 20 also contained equipment for scrap recovery operations and equipment for several materials testing procedures.
A small room opening off of hallway 24 was originally used as a shipping and receiving vault, and during the decommissioning project this room was used as a staging area for surveying and packaging contaminated waste.
Another room, originally opening off of the east end of hallway 23 has been in continuous use as a storage vault.
The original door was sealed and a new doorway into labs 17 and 19 was opened.
The rest of the Phase 3 area was not used for nuclear materials processing.
A limited amount of beta-gamma contaminated material was brought into the Phase 3 area.
Samples of beta-gamma materials were occasionally analyzed in Laboratories 19 and 20 after the end of the FFTF work.
The waste resulting from this work was solidified and placed in waste drums for disposal rather than being poured into the Building C drain system.
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FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 4
3.0 DECONTAMINATION OPERATIONS Building C was used for a broad range of R&D. projects with thorium, plutonium, and uranium solutions and powders.
The general procedure for decontamination operations performed in the Building consisted of (a) removing all SNM, equipment and supplies, (b) removing service and utility lines that would not be needed during decontamination, (c) decontaminating surfaces in the rooms, (d) removing drain lines, (e) excavating underlying soil, and (f) disposing of contaminated waste.
Surveying for radioactivity was conducted during and after decontamination.
A successfully decontaminated area was isolated from other areas still being decontaminated in order to prevent recontamination.
. The decontamination operations were performed by skilled and unskilled laborers, lab technicians, and health physics technicians and professionals trained in approved decontamination surveying and analytical procedures.
The survey equipment and procedures are described in Section 4.0.
j 3.1 Preparation of Rooms for Decontamination 4
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All accountable SNM was removed from the area to be 1
decontaminated.
Equipment, supplies, and HVAC filters were surveyed for contamination before removal from Building C.
The equipment and supplies were released for unrestricted use if survey results met applicable release criteria.
If the survey showed. contamination at or above permissible limits, the material was decontaminated to meet the limits before removal or was disposed of as contaminated waste.
In some cases, equipment was disassembled and contaminated portions were removed and disposed of as contaminated waste.
3.2 Decontamination of Pipe and Duct i
Service lines (compressed air, chilled water, vacuum, etc.),
electrical conduit, HVAC, and exhaust ducts were removed if they i
would have interfered with the comprehensive survey of room I
surfaces.
Paint and coatings were removed from these pipes and ducts.
Dismantled, cleaned pipes were surveyed for radioactivity and released as clean scrap if the limits met applicable release criteria.
Pipes that exceeded these limits were disposed of as contaminated waste.
Filters, filter housings, and branch ducts in th'e glove box off-gas system were removed.
Filters and filter housings in the room off-gas system were removed.
Paint and coatings were removed from the ducts and filter housings.
Cleaned duct and housings were surveyed for radioactivity and released as clean l
scrap if the activity levels met applicable release criteria.
1 If the survey showed activity above these limits, the materials were disposed of as contaminated waste.
Preliminary surveys of glove box off-gas and room off-gas headers showed no removable i
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FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C contamination on interior or exterior surfaces.
The duct was surveyed at-all joints, disassembled, sealed in plastic, and is being retained for'further survey.
3.3 Decontamination of Room Surfaces Paint, floor tile, and tile cement were removed from most walls, ceilings, and floors.
Removal was necessary because many of the walls and ceilings had been repainted and new floor tile had been installed as laboratories were converted to other uses.
The paint was removed to expose either the base surface or the original layer of paint that had been applied prior to introduction of licensed material into a room. Paint was not removed from walls in rooms where it was the original coat or where SNM had been excluded.
SNM was not handled in the Mechanical Equipment Room, the Fire Equipment Room, the Change Rooms or the front offices.
Walls, ceilings, and floors were surveyed for alpha radioactivity (the ceilings of offices were not surveyed).
When contaminated areas were found, walls were decontaminated by removing portions of cinder block and floors were decontaminated by chipping up portions of the concrete floor.
These areas were resurveyed and the iterative process of chipping and surveying was continued until release limits were met.
These removed materials were disposed of as contaminated waste.
3.4 Drainline Removal Hot and cold drainlines had been installed under the floor of Building C.
A diagram of the hot drain system for Phase 3 is shown in Figure 3-1.
The floor was removed from above each hot drainline after the bare concrete floor had been surveyed and released.
This uncontaminated concrete rubble was disposed of as clean landfill.
The soil was removed from above each hot drainline and placed in 55-gallon drums.
Samples were obtained from each drum for analysis by gamma spectroscopy.
These analyses were used to determine the ultimate disposal of a drum's contents.
Drums that satisfy the release criteria shown in Table 4-2 are being retained at the LRC for unrestricted disposal after the verification survey has been completed by the NRC.
Drums that exceeded these criteria have been shipped to an NRC licensed disposal site.
Each hot drain line was cut into sections, removed, and surveyed.
The pipe was released as clean scrap if the survey results indicated that it met applicable release limits; otherwise, the pipe was decontaminated to meet the limits or was disposed of as contaminated waste.
3-2
________ A
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C All cold drain lines were surveyed for smearable alpha radioactivity.
No contamination was found, therefore, these lines were not removed.
(Experience indicates that pulling a smear cloth through the line is a reliable method for detecting the presence of radioactivity.
A contaminated drain line was found by this method in Phase 2.)
3.5 Soil Excavation Samples were taken of the soil lying under drainlines after the pipe was removed.
If analyses showed the radioactivity to be below the limits specified in Table 4-2, temporary flooring was installed to isolate the pipe trench.
If the activity exceeded these limits, further excavation was performed.
Soil removal from a given area was continued until soil samples taken from the surface of the excavation showed the radioactivity to be below the limits listed in Table 4-2.
Figure 3-2 shows the location of the excavations.
Excavated soil was placed in 55-gallon drums.
Samples were obtained from each drum for analysis by gamma spectroscopy.
These analyses were used to determine the ultimate disposal of a drum's contents.
Drums that satisfy the criteria shown in Table 4-2 are being retained at the LRC for unrestricted disposal after the verification survey has been completed by the NRC.
Drums that exceed these criteria have been shipped to an NRC licensed disposal site.
3.6 Decontamination of Building Exterior The Fire Equipment room, Mechanical Room, and enclosed storage area are included in outside areas as the normal access to these rooms is from the building exterior.
All stored materials and non-essential equipment was surveyed for contamination and moved to appropriate on-site storage locations or disposed of as uncontaminated waste.
A comprehensive alpha survey was performed on all walls and floors, only horizontal surfaces in the overhead were checked.
A statistical survey for beta was made on floors.
No contamination was found.
Equipment remaining in these rooms was statistically surveyed for both alpha and beta on all accessible surfaces.
The only contaminated material found was in the high efficiency filters removed from the main HVAC unit in the Mechanical Equipment Room.
The low level activity in these filters was identified as Cs-137 and Cs-134 with traces of Am-241.
This analysis leads to the belief that the material found, in part at least, had origins at Chernobyl earlier in 1986.
The filters were disposed of as radioactive waste.
The loading dock and ramp were surveyed in the same manner as the outside area rooms and no contamination was found.
The exterior walls, roof, and equipment were statistically 3-3
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C surveyed for alpha and beta activity.
Decontamination activities associated with these surveys included:
(1) building exhaust system ductwork - preliminary surveys showed no removable interior contamination.
The outer covering and insulation were surveyed, removed and disposed of as uncontaminated waste, (2) expansion joint copper flashing and galvanized HVAC cover - low level activity found in these locations was removed and the decontaminated items left in
- place, (3) laundry dryer discharge stack - low level beta contamination found on the interior surface was removed and the cap reinstalled.
3.7 Waste Disposal Contaminated materials (equipment, pipes, ducts, off-gas filters, filter housings, paint chips, floor tile, concrete chips, soil, etc.) were placed in standard shipping containers for shipment to a licensed disposal facility according to the
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FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 4.0 SURVEY DESIGN AND PROCEDURES R&D projects performed in Building C involved the use of plutonium, thorium and uranium.
The isotopes of these three elements are primarily alpha emitters, but many of their daughters are gamma emitters.
The survey design was based upon inspecting surfaces primarily for alpha contamination and performing gamma spectroscopy analyses on soil, paint chips, etc.
Sampling was planned according to NUREG/CR-2082 (10) to assure that no area remained that contained radioactivity above release limits established by the NRC.
The effect of naturally occurring thorium and uranium in the soil at the LRC site was also taken into account during planning and surveying.
4.1 Applicable Release Limits The release limits applicable to surfaces were obtained from Table F-1 of License SNM-778, Reference 1.
These limits are reproduced in Table 4-1.
The limits for transuranics are the most restrictive in this table and were selected for application to the decommissioning of Building C.
From previous background measurement experience within buildings at the LRC, it was concluded that the small natural surface background alpha and beta-gamma activity from thorium, uranium, and their daughters would not significantly affect the decontamination effort required to achieve the release limits.
Therefore, the surface decontamination work for Building C was based on the conservative use of gross alpha and gross beta residual activity to satisfy the surface release limits of Table 4-1 for unrestricted use.
In practice the limits used for alpha contamination were 20 dpm/100 cm2 removable, 100 dpm/100 cm2 average fixed, and 300 dpm/100 cm2 maximum fixed.
For beta contamination the limits used were 1000 dpm/100 cm2 removable, 5000 dpm/100 cm2 average fixed, and 15000 dpm/100 cm2 maximum fixed.
Release limits for the concentration of radioactivity in soil are provided in Reference 3 and are listed in Table 4-2.
These limits were applied to soil remaining under Building C and to excavated soil.
These limits can be corrected for the naturally occurring thorium and uranium (10).
Survey design included correcting the measured analyses for soil samples below the limits, but not correcting measured analyses that were at or above the limit.
The correction would add confidence that an ALARA condition was achieved.
The release limit for external gamna exposure is given in Reference 2 and is included in Table 4-2.
This limit may be corrected for local background actitity.
It was concluded that the beta-gamma activity from natural thorium, uranium, and their daughters would not significantly affect survey results, but radiation from Building J and the Hat Cells would have to be taken into account.
4-1
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C The Hot Cells are located near the southwest corner of Building B and contain high-level beta-gamma materials.
Building J is located toward the northeast behind Building C and is used for storage of high-level beta-gamma waste.
Measurable levels of gamma radiation are present in the vicinity of both of these buildings.
A survey in and around Building C for external gamma activity would be needed to obtain data showing that the source of gamma radiation in the vicinity of Building C was from the I
adjacent areas and not from Building C itself.
4.2 Survey Design 4.2.1 Surface Survey Design for Use Areas Most of the laboratories in Phase 3 had been used for experiments with all three elements of interest, i.e.
plutonium, uranium, and thorium.
Some laboratories had been cleaned and repainted more than once co there was a possibility that contamination existed beneath the paint and floor tile. Walls, floors, and ceilings were stripped to the original surface to expose potential contamination for identification.
The surface surveys were designed with these items in mind.
The laboratory surfaces (walls, floors, and ceilings) that had existed during experimental work with plutonium, thorium, and uranium had to be identified.
Materials that could interfere with a comprehensive survey for surface contamination had to be removed.
Paint, floor tile, and tile cement had to be removed from these surfaces to expose the original surface.
A rectangular grid was designed for use on walls, floors, and surfaces with each grid block containing one square meter.
The dimensions of the grid block were determined by the size of the probe to be used for direct alpha survey.
An example of a grid configuration is shown in Figure 4-1.
The alpha survey design included a comprehensive direct survey and removable (smear) survey for each of the grid blocks.
This comprehensive method was chosen for the alpha surveys because the history of usage, leaks, and spills of SNM within specific laboratories was uncertain.
The alpha surveys would be conducted after removal of surface coatings to identify areas that would require further decontamination.
When the alpha surveys showed acceptable results, other types of surveys would be conducted.
Direct and removable beta, direct gamma, and one meter from surface gamma surveys were planned for floor grid blocks randomly selected in each Phase 3 area.
This statistical method was chosen for beta-gamma surveys because of the low potential for beta-gamma contamination in Building C.
Since the i
I l
4-2
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C flocr was the most likely place to have been contaminated in case of a spill, only floor grid blocks were routinely selected for the beta-gamma surveys.
However, other areas would be surveyed on a special basis when operating history or survey data indicated a need for beta surveillance.
4.2.2 Survey Design for Non-use Areas The survey design for non-use areas was divided into two categories:
(1) Areas accessible from use areas such as the front offices and hallway, (2) Areas accessible only from the building exterior such as the Fire Equipment Room and the Mechanical Room.
For areas accessible from use areas, surveys were performed in the same manner as use areas except that ceilings were not surveyed.
For areas not accessible from use areas, a
direct alpha survey was performed, 5 points per 1 meter square grid, with removable alpha surveys in each grid and direct beta surveys in randomly selected floor grids.
Overheads were checked on horizontal surfaces only.
4.2.3 Exterior Surface Survey Design Due to the reduced likelihood of contamination on exterior surfaces, the survey density used was reduced to five locations in each grid block.
The grid size also varies from 2x3 meters on walls to 4x4 meters on the loading dock ramp.
Outside walls were surveyed to two meters above grade.
Direct alpha surveys were made in each grid block and beta and gamma surveys were made in randomly selected ramp and roof grid blocks.
Removable alpha (smear) surveys were made in each grid block and removable beta surveys were performed for horizontal surfaces.
Penetrations in surfaces were surveyed independent of grid pattern as equipment.
4.2.4 Survey Design for Equipment A separate equipment survey plan was developed due to the amount of equipment which has been left in place in Phase 3 at the conclusion of decommissioning and will be released as a part of the building.
Equipment includes such items as pumps, motors, water pipes, heating / ventilation systems, ceiling trusses, and conduit.
Direct statistical alpha surveys were performed with the largest appropriate alpha probe on all 4-3
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C equipment.
A statistical beta survey was performed as appropriate.
Small area smears were counted for both alpha and beta. Large area smears were taken on all accessible surfaces and measured using an alpha survey meter.
4.2.5 Soil Survey Design Four separate types of soil surveys were planned.
One would be to determine the extent of contamination (core samples)
Another would be for excavated soil placed in drums (drummed soil samples)
A third would be for soil samples from the face of an excavation (ditch face sample)
The fourth would be to establish the concentrations of naturally radioactive isotopes in the site's soil (background samples). The same analytical procedure could be used for each type, but sampling methods would differ.
Since a large number of samples was expected, gamma analyses were planned based upon known daughters of plutonium, uranium and thorium.
A sampling method was planned for excavated soil to obtain a uniform quantity of soil for analysis as each drum was filled.
A sampling method was planned to obtain samples from the surface of the ditches that would result in a uniform quantity of soil for analysis from gridded areas of the excavation.
Core samples were planned to define contaminated soil boundaries and to obtain samples of background soil at this site.
The sampling plan was based on the assumption that the only source for soil contamination would be the hot drain system.
The only other pathway for contaminants to enter the soil under the building would be through the concrete floor.
This type of contamination would be found on and in the floor itself during surface surveys and could be tracked if it did appear.
(No evidence was found that contamination penetrated through the concrete into the soil.)
4.2.6 Ambient Gamma Radiation Survey Design While establishing background levels, it became obvious that the gamma radiation levels in and around Building C were due to external sources The Building J high level waste storage area is the major source with the hot cell and other operations in Building B contributing.
Additional shielding was added to the roof in an attempt to achieve levels of not greater than 57 nR/hr (500 nR/hr full-time occupancy) in Building C.
To verify the success of this effort, a gamma radiation survey plan was developed.
All measurements were taken with a commercially available micro-R meter.
Readings would be taken in a uniform grid pattern established on the grounds around the building.
4-4
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 4.3 Survey Instruments The instruments used for survey and analysis in Phase 2 are standard models routinely used by the nuclear industry for this type of work.
The instruments were calibrated in accordance with applicable LRC Technical Procedures using National Bureau of Standards traceable sources.
4.3.1 Surface Survey Instruments Each surface survey instrument has a lower limit of detection for the radiation being measured.
This is the lowest level of non-zero activity that it can register.
These limits are defined in the following sections.
4.3.1.1 Direct Alpha Survey Instruments Eberline Model PAC-4G or Model PAC-4G-3 Gas Proportional Survey Meters were used for making direct alpha surveys with two different size probes.
The probes consisted of either a Model AC-23A 335 cm2 Flat Plate Probe or a Model FM-3G 445 cm2 Floor Monitor Probe.
Calibration was performed according to Technical Procedure LRC-TP-51 using NBS traceable alpha sources.
The lower limit of detection for the PAC-4G for alpha detection was 30 cpm /50 cm2, 4.3.1.2 Direct Beta Survey Instrument Separate Eberline PAC-4G instruments similar to those described above were used for making direct beta surveys.
Calibration was performed according to Technical Procedure LRC-TP-51 using NBS traceable beta sources.
The lower limit of detection for the PAC-4G for beta detection was 300 cpm /50 cm2 4.3.1.3 Alpha and Beta Smear Survey Instruments Either an NMC Model PC-5 Proportional Counter or an ORT-S-1 Gas Proportional Smear Counter was used to count alpha and beta smears.
The former is calibrated using Technical Procedure LRC-TP-162 and the latter using Technical Procedure LRC-TP-190.
Calibration was done with NBS traceable alpha and beta sources as appropriate.
The background level for the smear counters was 0.1 dpm alpha / 100 cm2 and 300 dpm beta /100 cm2, 4.3.1.4 Surface Gamma Survey Instrument A Geiger-Muller (GM) Survey Meter was used for the surface gamma survey.
Instrument calibration was performed according to LRC-TP-50.
The lower limit of detection for the GM meter was about 0.05 mR/hr.
4-5
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 4.3.2 Instruments used for Additional Gamma Survey The Geiger-Muller (GM) Survey Meter described above was used for the gamma surveys one meter above the floor surfaces.
A Model RSS-lll Reuter-Stokes Environmental Radiation Monitor was also used to measure gamma radiation one meter above the walking surfaces.
These measurements were taken both inside and outside Building C.
This monitor was calibrated by the manufacturer with NBS traceable sources.
The lower limit of detection for the RSS-lll was 1 nR/hr.
4.3.3 Soil Survey Instrument A Nuclear Data Corporation high-resolution gamma-ray spectroscopy system using HPGe detectors was used to nondestructively analyze soil samples.
This system is standardized according to Technical Procedure LRC-TP-210.
This spectroscopy system was used to examine a gamma spectrum from about 50 kev to about 2 MeV.
Am-241, plutonium, thorium, and uranium concentrations were measured by analysis of gamma-ray energies within this range.
The Am-241 concentration was determined directly from the 59.54 kev peak.
The plutonium concentration was calculated by multiplying the Am-241 concentration by an experimentally determined factor.
(The Pu-239 concentration was directly measured at 375.02 and 413.69 kev in samples containing nci/g quantities of Pu-239.
These values were compared with Am-241 concentrations in the same samples to develop the factor.)
The Th-232 concentration was determined indirectly from the Pb-212 daughter 238.60 kev peak.
The uranium concentration was determined directly from the 185.72 kev peak for U-235.
(A correction was made for the 186.18 kev peak for Ra-226.) Other gamma-ray peaks were evaluated for radionuclides such as Co-60, Cs-137, and U-232 as needed.
l 4.4 Survey Procedures A list of the procedures used for this project is provided in Table 4-3.
These procedures were prepared in accordance with QA Plan No. 82008L (3).
4.4.1 Surface Surveys for Use Areas Surface surveys were conducted according to Technical Procedure LRC-TP-183.
The major steps in this procedure are summarized below.
l (1) Mark the surface with 1 square meter grid blocks.
l Sketch the grid on a data sheet and label each block.
l 4-6
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C (2) Perform a direct alpha survey with a PAC-4G using a large area probe.
Make sequential measurements in a grid block until the entire block has been surveyed.
Record the location and the direct count on a log sheet.
(3) Take a 100 cm2 smear in each grid block.
Count the smears for alpha activity in a proportional counter.
Record the location and smear activity on a data sheet.
(4) In a randomly selected grid block on the floor, conduct a direct gamma survey, a direct beta survey, and a beta smear survey.
Using a GM meter, locate the point in the grid block with the maximum gamma radiation level.
Record the GM readings at this point at floor level and at one meter above the floor.
Perform a direct gamma survey at this point at 1 meter above the floor with the RSS-111 pressurized ion chamber.
Perform a direct beta survey of the floor at the maximum gamma point in each block with a PAC-4G/AC-21B beta meter.
Record the grid number and survey results on a data sheet.
(5) Take a 100 cm2 smear at the maximum gamma point in each block.
Count the smears for beta activity in a proportional counter.
Record the location and smear activity on the data sheet.
4.4.2 Surface Surveys for Non-use Areas Areas accessible from use areas were surveyed according to LRC-TP-183.
These surveys were conducted in the same manner as use area surface surveys except that the ceiling was not surveyed.
Areas not accessible from use areas were survayed according to LRC-TP-327, " Survey Procedure for Building C-Outside Areas."
This procedure requires the following:
(1) Establish the grid pattern required by the procedure after non-essential equipment and stored materials have been surveyed and removed.
Prepare maps for each surface which assigns a coordinate system for grid block identification, (2) Perform direct alpha measurements in each grid block using a large area probe except in the overhead where accessiblity requires that a small probe be used, (3) Perform direct beta and gamma measurements in randomly selected walking surface grid blocks.
Dose-rate measurements are made 1 meter above the surface in the same location, (4) In each grid block, large area smears are collected and measured for alpha.
Small area smears are measured for 4-7
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C alpha on all surfaces and for beta on walking' surfaces, (5) All data are recorded on appropriate data sheets.
A If contamination is discovered, a survey is performed to establish the extent of contamination.
Expanded grid maps are prepared for evaluation.
If the area is decontaminated the final survey is comprehensive.
4.4.3 Exterior Surface Survey Exterior surface surveys were also performed according to LRC-TP-327.
The requirements for this survey is described in section 4.4.2.
4.4.4 Equipment Survey Equipment was surveyed according to technical procedure LRC-TP-330 which requires:
(1) A sketch or photograph of equipment to document survey locations, (2) Direct alpha survey of 100% of accessible surfaces on equipment located in use areas. A statistical survey is performed on equipment associated with exterior or non-use areas.
A large area probe is used where practicable, (3) Statistical direct beta surveys are required on equipment located in Penthouses and exterior areas, (4) Collect a large area smear from all accessible surfaces of all equipment and measure for alpha activity, (5) Collect small area smears for a representative number of locations on each piece of equipment and measure for both alpha and beta activity, (6) Document all results on data sheets supplied.
4.4.5 Soil Surveys All soil samples (whether from drums, excavations, or cores) were prepared for analysis using Technical Procedure LRC-TP-208 and were analyzed according to Technical Procedure LRC-TP-210.
Each sample was dried, screened, and placed into a container for analysis by gamma spectroscopy.
Soil standards were prepared using Technical Procedure LRC-TP-267.
Varying methods were used to obtain soil samples according to their source.
These methods are described below.
All samples were placed in labelled containers.
4-8
t
,,- r, O
~
, Q '
FINAL REPORT OF DECONTAMINATION'AND DECOMMISSIONING OF BUILDING C O4 s
SU bu Sampling,. sample preparation, and sample analysis information and data were recorded on route sheets that/followed the sanple from the time it was taken through the time'it was1 analyzed.
S s
f,
~ 4.4.5.1 Building C Core Samples 5
) a Technical Procedure LRC-TP-207 describes the method for;taking exploratory cores,in the vicinity of Ms conf'aminated soil to guide further' excavation' efforts.
A'; core sampler is used that collects a 2 liter sample per foot ofi depth.
k T
4.4.5.2 Drummed Soil s
I
?
L
- d
~
Technical Procedure LRC-TP-206 describes i R,'
three techniques for taking samples of drummed soil.
These are
((?'
al1scammonly used sampling techniques (11).
These three techniquesallowsamplingasadrumisfilledorafteritbas-me.,
been filled:
(1) Collect six to eight grab samples as3a drum is(filled to s
obtain a 3,to 4 liter sample.
The multiple samples 1
l create a composite sample representative of the drum's i '
contents.
I sq
-a M #
m
's 3
(2) Scoop a 3 to 4 liter sample from theicntire 7.'
length of a filled drum as it is laying on its'si'de, b
(3) Use a sampling thief to obtain a 3 to 4 liter sample from a filled drum standing upright.
14.4.5.3 Ditch Face Survey
'3' s -
Technical Procedure LRC-TP-197 describes two i
S techniques for collecting soil samples in excavated areas:
l l'
1 (1) Scoop a 3 to 4 liter sample from the bottom of a trench i
f (no longer than 20' feet)'from which a'drainline has just 4
Jh s been removed to create a sample representative of the
~ t
- trench, (2) Scoop a 3 to 4 liter sample from the surface of a trench to crea,te a sample representative of about 10 square i
fect.
4.4.5.4 Background Soil Core Samples I
Technical Procedure LRC-TP-207 also describes the method of taking background soil cores external to "Suilding C.
i hs o
l 6
i i
P 4-9 1
,.-.y.-,,,,.-
, ~,--
y
._y.
..m_..___.-_,-.s___
-%.,m.
,,,.-..,-r._
_..,y m.
- J FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 4.4.6 Ambient Gamma Radiation Survey The procedure for measuring ambient gamma radiation levels was as follows:
(1) Establish a 20x20 foot grid pattern on the grounds around Building C and prepare a sketch for documentation assigning a coordinate system, (2) Using the micro-R meter (RSS-lll) measure the gamma radiation levels 1 meter above walking surfaces, as near grid line intersections as possible, (3) During surface surveys in Phase 3, measure the gamma radiation levels 1 meter above walking surfaces in each grid block selected for beta-gamma measurement, (4) Make measurements in the remainder of the building using a building plat to document location, (5) Data sheets are used to document readings.
The guidelines and techniques used for this survey are found in LRC-TP-183, LRC-TP-282, and LRC-TP-327.
4-10
TABLE 4-1.
ACCEPTABLE SURFACE CONTAMINATION LEVELS a
b b
b Nuclides Average,c,f Maximum,d,f Removable,e,f i
U-nat, U-235, U-238, and associated decay products 5,000 dpm a/100 cm 15,000 dpm a/100 cm 1,000 dpm a/100 cm 2
2 2
Transuranics, Ra-226, Ra-228, Th-230, Th-228, Pa-231, 4
Ac-227, I-125, I-129 100 dpm/100 cm 300 dpm/100 cm 20 dpm/100 cm 2
2 2
Th-nat, Th-232, Sr-90, Ra-223, Ra-224, U-232, I-126, I-131, I-133 1,000 dpm/100 cm 3,000 dpm/100 cm 200 dpm/100 cm 2
2 2
i Beta-gamma emitters (nuclides with decay modes other than alpha emission or spontaneous j'
fission) except Sr-90 and
[j others noted above.
5,000 dpm sy/100 cm 15,000 dpm sy/100 cm 1,000 dpm sy/100 cm 2
2 2
Where surface contamination by both alpha-and beta-gamma emitting nuclides exists, the limits established a
1 for alpha and beta-gamma-emitting nuclides should apply independently.
i b As used in this table, dpm (disintegrations u minute) means the rate of emission by radioactive material as determined by correcting the counts per murate observed by an appropriate detector for background, efficiency, and geometric factors associated with the instrumentation.
Measurements of average contaminant should not be averaged over more than 1_ square meter.
For objects of c
less surface area, the average should be derived for each such object.
d The maximum contamination level applies to an area of not more than 100 cm,
2 e The amount of removable radioactive material per 100 cm of surface area should be determined by wiping 2
that area with dry filter or soft absorbent paper, applying moderate pressure, and assessing the amo.unt of radioactive material on the wipe with an appropriate instrument of know efficiency. When removable contamination on objects of less surface area is determined, the pertinent levels should be reduced pro-portionally and the entire surface should be wiped.
f The average and maximum radiation levels associated with surface contamination resulting from beta-ganma emitters should not exceed 0.2 mrad /hr at I cm and 1.0 mrad /hr at I cm, respectively, measured through not more than 7 milligrams per square centimeter of total absorber.
4 4
e
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 4-2 BUILDING C SOIL RELEASE LIMITS AND BUILDING C EXTERNAL GAMMA EXPOSURE LIMIT
- Maximum Acceptable Limit For Unrestricted Use **
Contaminant Natural thorium (Th-232 +
Th-228) with daughters present and in equilibrium 10 pCi/g soil ***
U-234) with daughters present and in equilibrium 10 pCi/g soil Depleted uranium or natural uranium that has been separated from its daughters, soluble or insoluble 35 pCi/g soil Enricl.ed uranium soluble or insoluble 30 pCi/g soil Plutonium (Y) or (W) compounds 25 pCi/g soil Americium-241 (W) compounds 30 pCi/g soil External exposure Rate 10 micro-R/hr
- These limits are above background levels.
- The individual soil limits given in this table apply to cach element if it exists by itself.
When they occur as a mixture, the sum of the ratios of the elemental concentrations versus their limits must be less than 1.
Thus, for Building C, (Am-241/30) + (Pu/25) + (Th-232/5) + (U/30) <1
~
- A limit of 5 pCi Th-232/g soil has been adopted for this project.
4-12
-FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 4-3 LRC TECHNICAL PROCEDURES USED FOR BUILDING C DECOMMISSIONING OPERATIONS LRC-TP-50 CALIBRATION PROCEDURE FOR EBERLINE G-M COUNTER LRC-TP-51 CALIBRATION PROCEDURE FOR PAC-4G GAS PROPORTIONAL COUNTER LRC-TP-87 GENERAL RADIATION SURVEY LRC-TP-95 RESPIRATORY PROTECTION PROGRAM LRC-TP-162 CALIBRATION AND OPERATING PROCEDURE FOR NMC PC-5 PROPORTIONAL COUNTER LRC-TP-183 SURVEY OF DECONTAMINATED LABORATORY AND OFFICES IN BUILDING C FOR FIXED AND SMEARABLE CONTAMINATION LRC-TP-190 CALIBRATION PROCEDURE FOR BUILDING C PROPORTIONAL SMEAR COUNTER LRC-TP-197 BUILDING C SOIL SAMPLING PROCEDURE LRC-TP-206 PLUTONIUM DECONTAMINATION PROJECT DRUM SAMPLING PROCEDURE LRC-TP-207 BUILDING C SOIL CORE SAMPLING PROCEDURE LRC-TP-208 PREPARATION OF SOIL SAMPLES LRC-TP-210 ANALYSIS OF RADIONUCLIDES IN SOIL BY GAMMA RAY SPECTROSCOPY LRC-TP-219 EFFICIENCY CALIBRATION FOR GAMMA-RAY SPECTROSCOPY SYSTEM LRC-TP-220 GAMMA-RAY SPECTROSCOPY SYSTEM - COUNT REPRODUCIBILITY CONTROL CHART PREPARATION LRC-TP-221 GAMMA-RAY SPECTROSCOPY SYSTEM - ENERGY CALIBRATION AND PERIODIC CHECKS OF ACTIVITY AND ENERGY CALIBRATION LRC-TP-222 GAMMA-RAY SPECTROSCOPY SYSTEM - BACKGROUND CHECKS 4-13
5 FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C Table 4-3 cont.
LRC TECHNICAL PROCEDURES LRC-TP-236 OPERATING INSTRUCTIONS FOR USE OF 3M BRAND WHITECAP HELMET MODEL W-5005 LRC-TP-237 PREPARATION OF WASTE SHIPMENTS TO THE U.
S.
ECOLOGY SITE IN WASHINGTON LRC-TP-267 PREPARATION OF SOIL STANDARDS LRC-TP-271 STANDARDIZATION OF BECKMAN WIDE BETA COUNTING SYSTEM LRC-TP-275 ANALYSIS OF SELECTED RADIONUCLIDES IN PAINT CHIP SAMPLES LRC-TP-282 USE OF RSS-111 AREA MONITOR LRC-TP-327 SURVEY PROCEDURE FOR BUILDING C - OUTSIDE AREAS LRC-TP-329 COLLECTION OF PAINT CHIP SAMPLES.FROM BUILDING C SURFACES LRC-TP-330 EQUIPMENT SURVEY - BUILDING C LRC-TP-331 SURVEY OF BUILDING C ROOF OFF-GAS DUCT INSULATION FOR UNRESTRICTED RELEASE LRC-TP-334 RADIOCHEMICAL ANALYSIS OF SPECIAL SAMPLES FOR GROSS ALPHA AND GROSS BETA LRC-TP-335 PREPARATION OF PAINT CHIP SAMPLES i
i 4-14 l
FIGURE 4-1.
TYPICAL SURFACE GRID ARRANGEMENT LAUNDRY ROOM SOUTH WALL i
15 EAST WEST WALL FLOOR WALL CEILING i
A A
I 0;
B EAST B i
C C
14 i
15 l
15-NORTH l
15 NORTH WALL i
~
_g i'
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 5.0 PHASE 3 SURVEY RESULTS Building C was used'primarily for R&D projects with thorium, i
Since these are all alpha emitters and l~
.only limited information was available about specific usage in t
the laboratories, comprehensive surveys for direct and smearable alpha contamination were conducted on the surfaces of the Phase 3 area in Building C..
Only_ limited amounts of beta-gamma materials i
4 had ever entered Building C, so beta-gamma surveys were primarily conducted on a limited number of randomly selected floor grid blocks.
A survey was performed to establish gamma radiation i
levels due to sources external to Building C.
The data for these surveys and analyses are described below.
All data are contained j
in the Building C Decommissioning files.
I j
5.1 Surface Surveys 5.1.1 Initial Surface Surveys a
i Each former use area was cleaned (SNM and equipment l
were removed, non-essential service pipe and duct were removed, and paint and floor tile were stripped) and an initial survey was y
i performed to determine direct and smearable alpha radiation i
levels on the room's surfaces.
Offices and other non-use areas i
were surveyed on floors and walls (not ceilings) without removing I
paint and floor tile.
Tables 5-1 and 5-2 provide summaries of these initial surface survey results.
The lower limit of detection for the direct alpha survey with the large area alpha probes was at or below 30 dpm/100 cm2 As Table 5-1 shows, 4,785 of the 5,395 grids or 88.7% were at this level.
Another 592 grids or 11% were below or met the average release limit of 100 dpm/100 cm2 Eighteen or O.33% of the grids were above the average release limit and were subsequently cleaned.
The data from the waste tank skew this percentage because 11 of the 18 grids were tank grids.
Using the i
ALARA concept, additional decontamination was performed on the grids that were above the lower limit of detection.
No j
contamination was fcund on the ceilings.
Table 5-2 summarizes the 57,720 direct alpha readings i
that were obtained during the initial surface survey.
More than I'
91.5% or 52,837 of these readings were at the lower limit of detection and another 4877 or about 8.4% were below the maximum release limit of 300 dpm/100 cm2 Only six readings 'or less than l.
0.01% were above 300 dpm/100 cm2 with the highest reading being about 800 dpm/100 cm2, i
j No smearable alpha radioactivity above 20 dpm/100 cm2 was i
detected.
The background reading for the smear counter was 0.3 l
dpm/100 cm2 As shown in Table 5-3, 6,902 of the 8,296 smears or 83.2% were at this level.
Of the remainder, 1374 or 16.6% were between 1 and 6 dpm/100 cm2 and of the remaining 0.2% or 20 5-1
S FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C readings, 19 were between 6 and 15 dpm/100 cm2 and one reading between 15 and 20 dpm/100 cm2 5.1.2 Final Surface Surveys Decontamination was performed in those areas identified in the original alpha survey as being significantly above the limit of detection.
Some areas were more difficult to decontaminate than others.
Removal of 1/16 to 1/4 inch of the concrete surface was adequate in most areas.
Tables 5-4 and 5-2 provide summaries of the final survey results.
Table 5-4 gives a summary of the final direct alpha surface survey data.
The data show that all grid blocks are below the release criterion of an average value of 100 dpm/100 cm2 The data summarized in Table 5-5 has no single reading exceeding 300 dpm/100 cm2 Over 89.2% of the grid blocks and over 91.9% of the individual readings were at or below the limit of detection of 30 dpm/100 cm2 Table 5-3 summarizes alpha smear results.
No grid had smearable alpha activity greater than the allowable limit of 20 dpm/100 cm2, Surveys for direct and removable beta, and gamma activities were made in randomly selected floor grid blocks.
The results are shown in Table 5-6.
A gamma radiation reading was taken less than 1 cm from the floor and another reading was taken 1 meter from the floor at the same spot with a GM meter.
Both readings were nearly equal in all 287 grids indicating no residual gamma contamination was present.
(All 287 readings were between 0.02 and 0.11 mR/hr.
This is the lower limit of detection for the GM meter.)
As shown in Table 5-6, the beta activity averaged 30 cpm (corrected for background) well below the average release limit of 5,000 dpm/100 cm2 for fixed beta activity.
No reading for smearable beta activity was greater than 100 dpm/100 cm2, 5.2 Release Soil Survey Samples were taken from drums of soil excavated from under Building C (drummed soil samples) and samples were taken from the faces of excavations (ditchface soil samples).
Samples of site background soil were also taken (background soil samples).
The data are presented in Tables 5-7 through 5-10 for each type cf material.
These data are discussed below.
5.2.1 Background Soil Survey Core samples were taken at each foot of depth from three holes 15 feet deep and from 31 holes 2 feet deep to orovide 107 samples of background soil.
These samples were analyzed for Am-241, Th-232, Pu, and U. The results for all 107 samples are summarized in Table 5-7.
The results for Am-241 and plutonium represent the lower limits of detection for gamma analyses.
No 5-2
t FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C Am-241 or Pu activity was found in the background soil samples.
The values given in Table 5-8 for uranium and thorium have been used to correct ditch face and drummed soil samples for local naturally occurring concentrations of these elements.
5.2.2 Excavation Release Survey The data are summari ed in Table 5-9 for the ditchface survey for drainlines under the building.
The results for Am-241 and plutonium represent 11 samples in which Am-241 was detected and 113 samples where Am-241 was reported at the lower limit of detection.
The analyses for thorium and uranium indicate only background concentrations for these two elements remain in the excavation under Phase 3 and identify the relatively uniform concentration of these elements throughout the region.
To address the possibility of potential U-233 contamination in the ditch face soil samples, a series of Bateman decay chain calculations were performed to identify a nuclide that would provide a sensitive indication of U-233 concentration in soll.
This nuclide is Pb-212 which is a daughter of the U-232 present in the U-233 as a contaminant.
A review of the data from the ditch face samples showed that none had Pb-212 activity above that expected from the naturally occurring Th-232 parent.
A previous statistical evaluation of both the Pb-212 and Ac-228 activities had indicated that, when the Pb-212 activity was above that expected from the naturally occurring Th-232, the samples had equal concentrations of these isotopes.
(Th-232 produces Ac-228 and Pb-212 daughters.
These two daughters will be in secular equilibrium in geologic soil.
Thus, if their concentrations are found to be equal, a conclusion may be drawn that the Pb-212 originated from Th-232 rather than from U-232 which can also be a parent.)
These results indicate no contamination from U.^33.
The continued ingrowth of Am-241 was recognized and evaluated for its effect upon activity levels in the future.
5.2.3 Drummed Soil Survey i
l The data are summarized in Table 5-10 for the drummed soll release survey for drainline soil excavations.
There are 378 drums of soil that meet release limits.
The results for Am-241 and plutonium represent 45 samples in which Am-241 was detected and 325 samples where Am-241 was reported at the lower limit of detection.
The analyses for thorium and uranium indicate that primarily background concentrations for these two elements are contained in the releasable drums.
The background concentrations for thorium and uranium have been subtracted for the calculation of the unity factor for the releasable drums.
The data from analyses of the drummed soil samples was also reviewed for Pb-212 content to address the possibility 5-3
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C of potential U-233 contamination.
The statistical evaluation on which this review is based was discussed in Section 5.2.2. These data showed that no drums had Pb-212 activity above that expected from the naturally occurring Th-232 parent.
The drummed soil sample data were reviewed for the presence of Co-60 and Cs-137 contamination.
None of the samples for drums retained for release indicated concentrations above the experimental background.
There were 37 drums of soil that did not meet release limits.
The results for Am-241 and plutonium represented 25 samples in which Am-241 was detected.
The analyses for thorium and uranium indicated some contamination from these two elements was present in the soil in these drums.
The background concentrations for thorium and uranium have not been deducted for the calculation of the unity factor for these drums.
All 37 dr ms have been shipped t'o a commercial radwaste burial site for disposal.
5.3 Ambient Gamma Radiation Survey A survey was conducted in and around Building C during Phase 3 to measure the ambient gamma radiation levels.
Figure 5-1 and Figure 5-2 show representative results of these surveys.
These results are gross readings; i.e.,
no background has been subtracted.
The data show that the high-level waste stored in Building J and the Hot Cells in Building B are the external sources that, in addition to terrestrial and cosmic radiation, establish the background gamma radiation levels inside Building C.
5-4
1 FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 5-1 ORIGINAL AVERAGE DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number of Grids Number
<30 30-100
>100 of (grid average dpm/100 cm2)
Grids Laundry Room 195 8
203 Fan Room 397 34 431 Fire Equipment Room JB 48 Offices 139 139 Hallways 816 10 826 Change Rooms 578 58 636 Vault #18 205 13 218 Penthouse (V18) 176 176 Lab 19 410 125 11 546 Lab 20 692 50 742 Vault #22 22 70 92 Penthouse (V22) 59 7
66 Mech. Equip. Room 370 370 Storage Room 344 344 Exterior 334 217 7
558 Total 4785 592 18 5395 5-5
s FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 5-2 ORIGINAL DIRECT ALPHA SURVEY RESULTS Location-Direct Alpha Survey Results Total Number of Readings Number
<30 30!300
>300 of (dpm/100 cm2)
Readings Laundry Room 2829 651 3480 Fan Room 4369 178 4547 Fire Equipment Room 201 166 367 offices 1767 115 1882 Hallways 8560 342 8902 Change Rooms 6452 565 7017 Vault #18 2583 37 2620 Penthouse (V18) 1982 1982 I
Lab 19 4715 1080 5
5800 Lab 20 10424 418 10842 Vault #22 711 323 1034 Penthouse (V22) 1005 43 1048 Mech. Equip. Room 1916 208 2124 Storage Room 1720 1720 Exterior 3603 751 1
4355 Total 52837 4877 6
57720 5-6
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 5-3 ALPHA SMEAR SURVEY RESULTS Location Alpha Smear Survey Results Total Number of Grids Number
<1 170
>20 of
-~
(dpm/100 cm2)
Smears Laundry Room 344 63 407 Fan Room 549 141 690 Fire Equipment Room 117 14 131 Offices 190 32 222 Hallways 894 194 1088 Change Rooms 864 174 1038 Vault #18 193 36 229 Penthouse (V18) 179 27 206 Lab 19 712 157 869 Lab 20 1000 182 1182 Vault #22 87 22 109 Penthouse (V22) 97 18 115 Mech. Equip. Room 578 123 701 Storage Area 241 47 288 Outside 857 164 1021 Total 6902 1394 8296 5-7
t FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C I
TABLE 5-4 FINAL AVERAGE DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number of Grids Number
<30 30-100
>100 of (grid average dpm/100 cm2)
Grids Laundry Room 195 8
203 Fan Room 397 34 431 Fire Equipment Room 48 48 offices 139 139 Hallways 823 3
826 Change Rooms 587 49 636 Vault #18 205 13 218 Penthouse (V18) 176 176 Lab 19 420 126 546 Lab 20 696 46 742 Vault #22 22 70 92 Penthouse (V22) 59 7
66 Mech. Equip. Room 370 370 Storage Room 344 344 Exterior 335 223 558 l
Total 4816 579 5395 l
i i
1 5-8
t FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 5-5 FINAL DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number of Readings Number
<30 30-300
>300 of (dpm/100 cm2)
Readings Laundry Room 2829 651 3480 I
Fan Room 4369 178 4547 Fire Equipment Room 201 166 367 offices 1767 115 1882 Hallways 8607 314 8921 Change Rooms.
6469 548 7017 Vault #18 2583 37 2620 Penthouse (V18) 1982 1982 Lab 19 4819 988 5807 Lab 20 10452 409 10861 Vault #22 711 323 1034 Penthouse (V22) 1005 43 1048 Mech. Equip. Room 1916 208 2124 Storage Room 1720 1720 Exterior 3660 716 4376 Total 53090 4696 57786 5-9
i FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 5-6
SUMMARY
OF RELEASE DIRECT BETA AND GAMMA AND SMEARABLE BETA SURVEY RESULTS FOR 287 FLOOR GRID BLOCKS IN PHASE 3 Direct Gamma Direct Beta Smearabel Beta Decision Survey Results Survey Results Survey Results Average Value Average Value Average Value uR/hr cpm dpm/100 cm2 0.03 30 4
Accept Direct Gamma Direct Beta Smearabel Beta Decision Survey Results Survey Results Survey Results Maximum Value Maximum Value Maximum Value uR/hr cpm dpm/100 cm2 0.11 1550 62 Accept TABLE 5-7 ANALYSES OF BACKGROUND SOIL SAMPLES Number Activity, pCi/ gram of Am-241*
0.33 0.54 1.43 2.33 1.28 2.12 1.40 2.51 The values shown for Am-241 and plutonium represent minimum detectable levels; i.
e.,
they do not actually indicate the presence of americium or plutonium, but indicate an upper limit for the values if they were present.
- Of the 107 samples, 45 represent three 15 foot cores and 62 represent one foot and two foot samples from 31 locations.
5-10
e t
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C I
TABLE 5-8 ACCEPTANCE LIMITS FOR THE BACKGROUND SOIL ACTIVITIES
- Activity, pCi/ oram Bi-214 Pb-214 U-235 Ac-228 Pb-212 T1-208 1.03 1.08 0.21 1.74 1.76 1.48
- Details of the calculations for acceptance limits are given in Reference 10 and 12.
TABLE 5-9 ANALYSES OF DITCHFACE RELEASE SOIL SAMPLES Number Activity, pCi/ gram Unity of Am-241*
Max Avg Max 124*
0.35 0.85 1.50 3.69 1.19 2.04 1.44 2.17 0.08 0.21
- Of the 124 values represented for Am-241 and plutonium in this table, 113 are minimum detectable concentrations; i.
e.,
they do not actually indicate the presence of americium or plutonium, but indicate an upper limit for the values if they were present.
5-11
t FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C TABLE 5-10 ANALYSES OF DRUMMED SOIL SAMPLES Number Activity, pCi/ gram Unity of Am-241 Plutonium Th-232 Uranium Factor Samples Avg Max Avg Max Avg Max Avg Max Avg Max 370*
0.35 0.78 1.53 3.38 1.28 2.08 0.29 9.58 0.08 0.38 37 3.96 55.3 17.1 238.8 1.77 3.34 5.03 20.4 0.98 12.1
- Of the 370 values represented for Am-241 and plutonium in this category, 325 are minimum detectable concentrations; i. e.,
g they do not actually indicate the presence of americium or plutonium, but indicate an upper limit for the values if they were present.
l 1
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l 5-12
FIGURE 5-1.
AMBIENT GAMMA RADIATION LEVELS, nR/ HOUR ON THE~ GROUNDS AND ROOF OF BUILDING C 1
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5-14
i-,, 3 FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C 6.0 SURVEY INTERPRETATION i
An extensive decontamination program was conducted through-out Building C.
Based on the survey results shown in Section 5.0 for Phase 3 of the building, together with previously reported results on Phase 1 and Phase 2, the entire building meets or surpasses all applicable release limits and can be restored and released for non-nuclear purposes pending approval J
by the NRC.
Comprehensive surveys were performed on the room surfaces to measure direct and smearable alpha radioactivity.
A statis-e tical survey was performed for beta-gamma radioactivity.
Fixed alpha contamination was the primary surface contamination found i
in Phase 3 with most of the readings (99%) being at the lower
~
limit of detection.
Americium, plutonium, thorium, and uranium from nuclear fuels R&D were the only contaminants found in the soil under Phase 3 of Building C.
Excavation of soil under the i
drains continued until samples from all the faces of the excavations demonstrated release limits had been met with most of the samples (99%) being at background concentrations.- A total of I
407 55-gallon drums of soil were excavated.
The 37 drums of contaminated soil were shipped to a licensed commercial radwaste burial site for disposal.
The remaining 370 drums of soil are j
being retained at the LRC until approved for release.
The scope of the decontamination project and the procedures, i
equipment, and analyses applied give strong assurance that the i
measured values of residual radioactivity are representative and all release limits have been met.
Thus, the decontamination i
and decommissioning project for the building has been successfully completed and upon the concurrence of the NRC, will j
be released for unrestricted use.
s i
4 l
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6-1
e e
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C i
i
7.0 REFERENCES
1.
Docket No. 070-00824, NRC Materials License SNM-778, as renewed, and is under the timely renewal provisions of 10 CFR Part 70.33.
2.
Memo, A.F. Olsen, B&W, to W.T. Crow, NRC, " Decommissioning Plan for the Lynchburg Research Center's Building C", March j
28, 1993.
3.
LRC Building C Decommissioning Project QA Program, Work Plan for Plutonium Decontamination, Revision No. O, LRC Order No.
8604, LRC QA No. 82008L. May 12, 1982.
4.
Memo, W.T.
Crow, NRC to A.F. Olsen, B&W, " Standard Review Plan for Termination of Special Nuclear Material Licenses" with Appendix I, March 15, 1983.
1 5.
Report, " Decontamination and Decommissioning of Building C
-Phase 1 at Lynchburg Research Center Lynchburg, Virginia" j
RDD:85:8604-01:01, May 1985.
6.
Report, " Decontamination and Decommissioning of Building C
-Phase 2 at Lynchburg Research Center Lynchburg, Virginia" RDD:85:8604-01:02, October 1985.
7.
D.A. Edling and J.F. Griffin, " Certification of ERDA 4
Contractors' Packaging with Respect to Compliance with DOT Specification 7A Performance Requirements, Phase II Summary
~
Report", MLM-2228, June 12, 1975.
8.
Department of Transportation Hazardous Materials Regulations, Title 49 CFR Part 178.118, Specification 17H; steel drums.
9.
NRC Materials License No. 16-19204-01, Amendment No. 4, Expires November 30, 1985 and State of Washington j
Radioactive Materials License WN-1019-2, Expires November 30, 1985.
- 10. NUREG/CR-2082, " Monitoring for Compliance with Decommissioning Termination Survey Criteria" with Appendices I through VII, June 1981.
- 11. Arthur F. Taggart, " Handbook of Mineral Dressing, Ores.and Industrial Minerals", John Wiley & Sons, Inc. 1927.
- 12. Memo, N. Soltys, B&W, to R.
L. Bennett, B&W, " Bldg
'C' Decommissioning", January 10, 1985.
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i 1,
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C i
APPENDIX ADDITIONAL INFORMATION RELEVANT TO PHASE 1 l
In response to our final survey report for Phase 1 and the l
subsequent Region II inspection, the Nuclear Regulatory j
Commission raised two issues requiring followup (1).
Survey data and other information pertinent-to these issues is presented in i
this section of the report.
+
1 Removal of Duct. System At the time of the Phase 1 inspection, off-gas ducting for the yet-to-be decontaminated Phase 2 and 3 areas of the building was still in service.
This ducting passes through Phase 1 on the way to the fans and stack.
The NRC indicated that when the ducting was finally removed, there would be a possibility of recontaminating Phase 1.
The off-gas systems serving both the glove boxes and the i
laboratory rooms were removed.
The removal was done by cutting the duct into manageable lengths, surveying the inside at each end, sealing the open end with plastic film, and carrying the segments to Laboratory 44 for temporary storage.
Before using the laboratory for storage, the floor and walls up to an elevation of 4 feet were covered with plastic sheet.
The results of smear surveys for removable alpha comtamination at each end of each duct segment as it was removed showed that all segments were below the minimum detectabe level (15 dpm/100cm2).
Additional surveys were then made prior to i
release of the material.as uncontaminated scrap.
These l
additional surveys confirmed that there was no removable activity on any of the duct segments.
Therefore, there is no way l
that the Phase 1 area could have been recontaminmated by the i
removal of the ducting.
These data will be available for NRC to review when they perform the Phase 2/3 inspection.
I.
Painted Surfaces l
Over the life of Building C, many of the walls and other surfaces were repainted.
Because we did not have documented l
evidence that the wallis were uncontaminated before they were l
repainted, paint was removed from repainted surfaces to reach the original coat of paint or the original masonary surface.
The i
release survey was done on this exposed surface.
Some of the l
walls, however, had never been repainted. It was our judgement at the beginning of the decommissioning project that such original l
painted surfaces could be surveyed without removing the paint.
Any contamination that might have worked its way into and through the paint would leave a trace of contamination on the outside surface that would be detected by the survey of that surface.
However, NRC requires that we demonstrate that there is no l
contamination beneath any painted surface (1).
l The issue was evaluated in two ways.
The first was to l
interpret the nature of the small but measureable activity I
l 1
e s
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C reported by NRC on paint chip samples obtained during their conformation survey of Phase 1.
Three sets of samples were taken i
from originally painted walls adjacent to positions where NRC had taken samples.
Each set consisted of three kinds of samples:
concrete and paint ( a film of paint and the piece of concrete block to which it adhered), paint (removed by paint thinner),
and concrete alone (obtained from the interior of the concrete block).
The samples were analyzed for gross alpha and gross beta by standard radioanalytical procedures.
The results are presented in Table 6-1.
When the accuracy of the measurement is taken into consideration (about 125%), it is clear that the activity is due to naturally occurring radioisotpes in the concrete.
The gross alpha results from the concrete and paint samples are also in rough agreement with those obtained by NRC, indicating that NRC data are essentially background.
The results for paint alone convert to 4 dpm/100 cm2 which is well below the release limit.
The second set of measurements involved a statistical sampling of unrepainted walls in Laboratories 16 and 27 and in the Laundry Room.
These walls were selected because they had the highest exposure to radioactive contaminants.
Futhermore, all of the other unrepainted walls left in the building were in areas were in where radioactive materials were never used such as offices.
1 The contaminant of primary concern was plutonium, which is the most restrictive in terms of release criteria.
The release criteria are 100 dpm/100 cm2 average and 300 dpm/100 cm2 maximum.
A very sensitive method of determining plutonium activity is to use gamma spectroscopy and measure for the presence of Am-241 which is a decay product of Pu-241.
It has been determined for j
the plutonium used in Building C that the ratio of alpha-emitting plutonium isotopes to Am-241 is 4.321.
Therefore, the plutonium release crieria corresponds to Am-241 activities of 19 dpm/100 cm2 average and 56 dpm/100 cm2 maximum.
A total of 30 random samples were analyzed for Am-241, U-235, and Th-232 by gamma spectroscopy.
The sample locations were uniformly distributed over unrepainted walls so that the sample population would be representative of the total population.
The sample locations were surveyed with a PAC-4G 335 cm2 alpha probe before and after the samples were taken.
All direct readings were background (<30 dpm/100 cm2).
Small area smears were also taken at these locations and counted for alpha contamination.
The results showed an average smearable activity of 0.6 dpm/100 cm2 and a maximum of 6 dpm/100 cm2, The paint was removed over an area the size of the PAC-4G 1
large probe (Sin.x181n.) at each sample location using paint remover.
The paint samples were counted by gamma spectroscopy, standardized and normalized to 100 cm2 The results are summerized in Table 6-2.
Of the 30 values represented in the.
Table, 27 are minimum detectable concentrations, i.e.,
they do not actually indicate the presense of americium or plutonium, but i
give an upper limit for the values if they were present.
The accuracy of the Am-241 and plutonium results is about 121% ; the accuracy of the Th-232 and U-235 results is comparable, but was 2
l..
FINAL REPORT OF DECONTAMINATION AND DECOMMISSIONING OF BUILDING C not derived because these results are very much less than the release limits.
The measurements clearly demonstrate that there is no radioactive contamination above release limits in or beneath unrepainted surfaces.
Reference 1.
Letter, W.T.
Crow, NRC, to A.F. Olsen, B&W, June 20, 1986.
TABLE 1. Gross Alpha and Beta Activity on Paint and Concrete Gross Activity (dpm/gm)*
Sample Description Alpha Beta concrete alone 24 186 Paint alone 2
31 Concrete-plus-paint 22 197
- Corrected for counting background.
TABLE 2. Summary of Paint Gamma Analysis Results Number of Activitv, DPM/100 cm2 Grids Am-241 Plutonium Th-232 U-235 AVG MAX AVG MAX AVG MAX AVG MAX 30 4.8 11.3 20.9 48.8 7.2 18.7 3.0
6.0 (Note
The avergae values from a background paint sample are 4.8 dpm/100 cm2 Am-241, 3.4 dpm/100 cm2 U-235, and 6.2 dpm/100 cm2 Th-232.)
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