ML20128F952
| ML20128F952 | |
| Person / Time | |
|---|---|
| Site: | 07000824 |
| Issue date: | 05/31/1985 |
| From: | BABCOCK & WILCOX CO. |
| To: | |
| Shared Package | |
| ML20128F942 | List: |
| References | |
| RDD:85:8604-01:, RDD:85:8604-1:, NUDOCS 8507080418 | |
| Download: ML20128F952 (47) | |
Text
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n DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I AT LYNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA 4
REPORT NUMBER:
RDD:85:8604-01:01 MAY 1985 BABCOCK & WILCOX Lynchburg Research Center Lynchburg, Virginia 8507080418 850528 PDR ADOCK 07000824 C
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o DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE OF CONTENTS SECTION PAGE
1.0 INTRODUCTION
1-1 1.1 Statement of the Problem 1-1 1.2 Statement of the Objective 1-1 1.3 Organization of this Report 1-1 2.0 IDENTIFICATION OF PREMISES 2-1 2.1 Site Description 2-1 2.2 Building C Physical Description 2-1 2.3 Definition of Phase I 2-1 2.4 History of Operations in Phase I 2-2 3.0 DECONTAMINATION OPERATIONS 3-1 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 Drain Line Removal 3-3 3.5 Soil Excavation 3-3 3.6 Waste Disposal 3-3 4.0 SURVEY DESIGN AND PROCEDURES 4-1 4.1 Applicable Release Limits 4-1 4.2 Survey Design 4-2 4.2.1 Surface Survey Design 4-2 4.2.2 External Gamma Survey Design 4-2 4.2.2 Soil Survey Design 4-3 4.3 Survey Instruments 4-3 4.3.1 Surface Survey Instruments 4-3 4.3.2 External Gamma Survey Instrument 4-4 4.3.3 Soil Survey Instrument 4-4 4.4 Survey Procedures 4-5 4.4.1 Surface and External Gamma Surveys 4-5 4.4.2 Soil Surveys 4-6 I-1
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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 5.0 PHASE I SURVEY RESULTS 5-1 5.1 Surface Surveys 5-1 ~
5.1.1 Initial Surface surveys 5-1 5.1.2 Release Surface Surveys 5-2 5.1.3 External Gamma Radiation Survey 5-3 5.2 Release Soil Survey 5-3 5.2.1 Background Soil Survey 5-3 5.2.2 Excavation Release Survey 5-4 5.2.3 Excavated Soil Drums Survey 5-4 5.2.4 Soil Survey Data Analysis 5-5 5.3 Decontamination, Waste Survey 5-5 6.0 SURVEY INTERPRETATION 6-1
7.0 REFERENCES
7-1 I-2
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' DECONTAMINATION AND' DECOMMISSIONING OF BUILDING C - PHASE I LIST OF TABLES
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Table Page 4-1 Acceptable Surface Contamination Levels 4-8 4-2 Building C Soil Release Limits and Building C External Beta-Gamma Exposure Limit 4-9 4-3 LRC Technical Procedures Used for Building C i
Decommissioning Operations 4-10 5-1 Summary of Average Original Direct Alpha Survey Results 5-6 5-2 Summary of Maximum Original Direct Alpha Survey Results 5-7 i
5-3 Summary of Original Alpha Smear Survey Results 5-8 5-4 Summary of Average Release Direct Alpha Survey Results 5-9 j
5-5 Summary of Maximum Release Direct Alpha l-Survey Results 5-10 5-6 Alpha Survey Results 5-11 4
f 5-7 Summary of Release Direct Beta and Gamma and t~
Smearable Beta Survey Results for 242 Floor Grid Blocks in Phase I 5-11 5-8 Analyses of Background Soil Samples 5-11 5-9 Analyses of Excavation Release Soil Samples 5-12 5-10 Analyses of Excavated Soil Samples 5-12 4
5-11 Soil Samples Analysis Results 5-13 5-12 Analyses of Decontaminated Waste Samples 5-14 I-3
o e
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 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 I Hot Drain System 3-5 1
3-2 Phase I Excavation Locations 3-6 4-1 Typical Surface Grid Arrangement 4-11 5-1 External Gamma Survey 5-15 I
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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I
1.0 INTRODUCTION
1.1 Statement of the Problem The~ Babcock & Wilcox Company (B&W), a wholly owned subsidi-ary of Mc Dermott International, Inc., holds NRC License SNM-778 (1) to conduct operations involving SNM at its Lynchburg Research Center (LRC) near Lynchburg, Virginia.
Under this license, re-search 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 activties with radioactive materials in Building C.
B&W, in ceasing licensed activities in Building C, is complying with a valid license requirement as stated in Appendix F to SNM-778 to provide for decontamination of this building to protect the environment and the general public from exposure to levels of radioactivity in excess of those permissible.
Decontamination means the removal or reduction of radioactivity from buildings, walls, floors,and equipment and of radioactively contaminated soil from around and beneath buildings.
A decommissioning plan for Building C was submitted to the NRC for information purposes. (2)
Decommissioning means action taken that results in the facility or a portion thereof being released for unrestricted use and termination of control of License SNM-778 for the facility or portion thereof by the NRC and includes the act of decontamination.
The decommissioning plan divided work into three phases with a different section of the building being decontan,inated in each phase.
This report addresses the decontamination performed in Phase I.
1.2 Statement of the Objective The objective of the decommissioning project is to decon-taminate Building C in a responsible and safe manner so as to enable release of the facility for unrestricted use and from licensed control.
To assure adequate standards of quality are maintained in achieving this objective, work is performed accord-ing to QA Plan No. 82008L. (3) The decontamination includes the interior and exterior surfaces cf Building C and the underlying soil.
Table F-1 in Reference 1 establishes numerical limits for surface 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 daring decontamination, but followed the princi-ple of reducing contamination to ALARA levels (As Low As Reason-ably Achievable).
The objective will be achieved in three se-quential phases as described in Reference 2.
1.3 Organization of this Report This report contains seven sections that describe the decom-missioning work performed during Phase I of the Building C pro-1-1
D DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I ject.
Following this introductory section, a physical-descrip--
Etion of the site and Building C is provided.
Information is provided in Section 3 about the decontamination and decommission-ing operations themselves. The fourth section contains descrip-tions of the survey design and survey. procedures used to deter-mine residual radioactivity in and under the building.
Sections 5 and 6 provide the results and data interpretation of the sur-veys.
The final section lists the documents referenced in this report.
1-2
O D
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I o
2.0 IDENTIFICATION OF PREMISES 2.1 Site Description
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The Lynchburg Research Center (LRC) is located on 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 buridings comprising the LRC 2.2 Building C Physical Description The existing structure known as Building C is the result of several additions to a small laboratory completed in 1962 (see Fig.
2-3).
Building C is a single story building of concrete block con-struction with outside dimensions of 225 feet by 174 feet at its greatest width.
There is a small basement under one of the labora-tories.
The building contains about 24,000 square feet of labora-tory, 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 equip-ment 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 boiler room containing a boiler and a chilled water supply system, and a laundry.
There was a large storeroom that served the entire LRC.
Finally, the building contains a fan room with associated air stack that serves adjacent Building B as well as Building C.
2.3 Definition of Phase I Decontamination of Building C will be completed in three phases.
Phase I includes laboratories on the western end of the building where projects were performed with thorium, plutonium, and uranium solutions and powders.
Phase II includes laboratories on the eastern end of the building where projects were performed with plutonium and uranium oxide powders.
(External drain lines between Building C and the Liquid Waste Building are included in Phase II.)
Phase III includes two laboratories in the center of the building that were used primarily for analytical chemistry projects on plutonium fuels.
The Fan Room and Laundry are also included in Phase III.
Phase I includes about 10,000 square feet; Phase II, about 6,000 square feet; and Phase III about 8,000 square feet.
Figure 2-4 shows the areas included in each phase.
No area beyond the walls and roof of Build-ing C are included in this decommissioning project.
2-1
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I Phase I includes former Laboratories 25 (Health Physics Office),
26 (Technician's Office), 27, 43, 44, 50, 51, 52, 53, and 54.
Also included are the offices and hallway along the front of the building that used to be part of Labs 43, 44, and 50; the western portion of Hallway 23; and the region marked as Old Central Stores.
The inter-ior walls, ceilings, and floors as well as the underlying soil are considered to be included in Phase I.
Physically surrounded by Phase I, but not included in Phase I, are the Fan Room and the Laundry Room.
The exhaust fans still pro-vide ventilation for all of Building C (both decontaminated and non-decontaminated areas).
The Laundry is still used for clothing from controlled areas.
2.4 History of Operations in Phase I The first experiments performed in the original building were bench-scale experiments converting thorium nitrate to thorium oxide.
An expansion in 1964 added pilot scale equipment for preparation of thorium - U-233 nuclear fuel by a sol-gel process.
Thorium fuel R&D was conducted in Laboratories 43, 44, 50, 53, and 54 and existing offices that used to be part of Laboratories 43, 44, and 50.
R&D with plutonium-bearing fuels was initiated in new labora-tories added in 1965.
A major building expansion was completed in 1968 to permit work on the FFTF Program.
Experiments with plutonium nitrate solutions were conducted in gloveboxes installed in Labora-tories 43, 44, 50, 53, and 54 and existing offices that used to be part of Laboratories 43, 44, and 50.
(Laboratory 25 has been used as the Health Physics Office; Laboratory 26, Technician's Office; and Laboratory 27, glovebox construction prior to it's conversion to an analytical chemistry laboratory for non-plutonium materials.)
Uranium fuel projects were initiated in la'boratories that were vacated at the conclusion of the FFTF Program.
These projects included work with uranium nitrate and uranium fluoride solutions and uranium fluoride, uranium chloride, and uranium oxide powders.
Uran-ium fuel R&D was performed in Laboratories 27, 43, 44, 50, 53, and 54.
A limited amount of beta-gamma contaminated material has been brought into the Phase I area.
Samples of beta-gamma materials were occasionally analyzed in Laboratory 27 and the waste was solidified and placed in waste drums for disposal rather than being poured into the Building C drain system.
Scaled containers of beta-gamma contam-inated materials from reactor sites were stored in the rear of Old Central Store.
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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 3.0 DECONTAMINATION OPERATIONS The Phase I area of 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 Phase I consisted of (a) removing all SNM, equipment and supplies, (b) removing service and utility lines that would not be needed dur-ing decontamination, (c) decontaminating surfaces in the rooms, (d) removing drain lines, (e) excavating underlying soil, and (f) dispos-ing 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 per-formed by skilled and unskilled laborers, lab technicians, and health physics technicians and professionals trained in approved decontami-nation procedures and surveying and analytical procedures.
The sur-vey equipment and procedures are described in Section 4.0.
3.1 Preparation of Rooms for Decontamination All accountable SNM was removed from the Phase I area.
Equip-ment and supplies in each room in Phase I were surveyed for contam-ination prior to removal from Building C.
The equipment and supplies were released for unrestricted use if the surface contamination levels were below the limits specified in Table 4-1.
If the survey showed contamination at cr 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 Service lines (compressed air, chilled water, vacuum, etc.),
electrical conduit, and HVAC (heating, ventilation, and air condi-tioning) ducts were removed if they would have interfered with the comprehensive survey of laboratory surfaces.
Paint and coatings were removed from these pipes and ducts.
Dismantled, cleaned pipes wera surveyed for radioactivity and released as clean scrap if the limits specified in Table 4-1 were met.
Pipes that exceeded these limits were disposed of as contaminated waste.
Dismantled, clean HVAC ducts were also surveyed for radioactive contamination and all were rein-stalled because they met the limits specified in Table 4-1.
Filters, filter housings, and branch ducts in the box off-gas cystem serving Phase I were removed.
Filters and filter housings in the room off-gas system serving Phase I were removed.
Paint and coatings were removed from the ducts and filter housings.
Cleaned duct and housings were surveyed for radioactivity and released as cican scrap if the surface activity levels were below the limits specified in Table 4-1.
If the survey showed activity above these limits, the materials were disposed of as contaminated waste.
The box off-gas and room off-gas headers were surveyed in place.
(These headers are suspended from the ceiling and did not interfere with the 3-1
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I survey of room's surfaces.)
All filters were disposed of as contam-inated waste.
3.3 Decontamination of Room Surfaces Paint, floor tile, and tile cement were removed from most walls, ceilings, and floors in the Phase I area.
Removal was necessary because the walls and ceilings had'been repainted and new floor tile had been installed as laboratories were converted to other uses.
Potential existed for alpha contamination to be hidden under the new paint and floor tile.
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.
(The paint was not removed from the walls of Lab 27 because it was the original coat.)
Paint was not removed from walls that had been erected after cessation of activities with SNM.
(These were primarily walls in the front offices.)
Paint was not removed from walls in rooms from which SNM had been excluded.
(SNM was not handled in Labs 25 or 26 or old Central Stores.
Non-nuclear operations have been resumed in old Central Stores.)
Floor tile and tile cement were removed to expose the concrete floor surface.
Paint chips, floor tile, sand and other wastes generated in the surface cleaning processes were placed in 55-gallon waste drums.
Samples were obtained from each drum for analy-sis by gamma spectroscopy.
These analyses were used to determine the ultimate disposal of a drum's contents.
Drums that satisfy the cri-teria shown in Table 4-2 are being retained at the LRC for unre-stricted 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.
Walls, ceilings, and floors were thoroughly surveyed for alpha radioactivity.
When contaminated areas were found, walls were decon-taminated by removing portions of cinder block and floors were decon-taminated 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.
Two areas, Lab 44 and Labs 50 - 54, were released for uncon-trolled access, but were later returned to controlled area status.
It was learned that Lab 44 was being inadvertently entered as a controlled area to change an area film dosimeter.
When this area was resurveyed for release, contamination was found under the original coat of epoxy paint on the floor and in the surface of the concrete.
The levels were below release limits, but decontamination was per-formed to meet ALARA conditions.
Contaminated soil was discovered under Lab 50 after it had been released for uncontrolled access.
The connecting Labs 50 - 54 were used as a cor. trolled area until excava-tion was complete and then were resurveyed for release.
Contamina-tion was found in the concrete floor in Lab 53 where a drainage sump had been filled with concrete.
(This was not known during the first release surver and was not found.)
The concrete plug was chipped out and the surrounding floor was decontaminated to meet release limits.
3-2
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 3.4 Drain Line Removal Hot and cold drain lines were installed under the floor of Building C.
A diagram of the hot drain system is shown in Figure 3-1.
The floor was removed from above each hot drain line after the bare concrete floor had been surveyed and released. This uncontami-nated concrete rubble was disposed of as clean land fill.
The soil was removed from above each hot drain line 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 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.
Each hot drain line was cut into sections, removed, and survey-ed.
If the surface activity was less than the limits specified in Table 4-1, the pipe was released as clean scrap.
Otherwise, the pipe was decontaminated to meet the limits or was disposed of as contami-nated waste.
All cold drain lines were surveyed for smearable alpha radio-activity.
No contamination was found, therefore, these lines were not removed.
(Experience in Phase II indicates that pulling a smear cloth through the line is a reliable method to identify radioactiv-ity.
A contaminated drain line was found by this method in Phase II.)
3.5 Soil Excavation Samples were taken of the soil lying under the drain line 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, core samples were taken to determine the extent of the con-tamination and then 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 ultimato 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 Waste Disposal As stated above, Phase I contaminated materials (equipment, pipes, ducts, off-gas filters, filter housings, paint chips, floor tile, concrete chips, soil, etc.) were placed in 55-gallon drums for shipment to a licensed disposal facility in accordance with applic-3-3
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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I able' requirements as described in References 5, 6, and 7.
Uncontami-nated paint chips, floor tile, cinder blocks, and sand were also placed in 55-gallon drums and are being retained at the LRC for unre-stricted disposal after the verification survey has been ccmpleted by the NRC.
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9 DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 4.0 SURVEY DESIGN AND PROCEDURES R&D projects performed in Phase I involved the use of plutonium, thorium and uranium.
The isotopes of these three elements are pri-marily alpha emitters, but many of their daughters are gamma emit-tors.
The survey plan was based upon inspecting surfaces primarily for alpha contamination and analyzing granular materials (soil, paint chips, etc.) for gamma contamination.
Sampling was planned according to NUREG/CR-2082 (8) to assure that no area remained in Phase I that contained radioactivity above release limits established by the NRC.
The effect of naturally occurring thorium and uranium at the LRC site was also taken into account during planning and surveying.
4.1 Applicable Release Limits The release limits applicable to Phase I surfaces were obtained from Table F-1 and Annex C of Reference 1.
These limits are repro-duced in Table 4-1.
The limits for transuranics are the most re-strictive in this table and were selected for application to Phase I.
These limits can be corrected for local naturally occurring thorium and uranium.
From previous background measurement experience within buildings at LRC, it was concluded that the small natural background surface alpha and beta-gamma activity from thorium and uranium and their daughters would not significantly affect the decontamination effort required to achieve the release limits.
Therefore, the sur-face decontamination work for Phase I was based on the conservative use of gross alpha and beta-gamma residual activity to satisfy the surface release limits of Table 4-1 for unrestricted use.
Release limits for Phase I soil are provided in Reference 3 and cre listed in Table 4-2.
These limits were applied to soil remaining under Building C and to excavated soil.
These limits can be correct-cd for the naturally occurring thorium and uranium.
Plans were made to correct the measured analyses for soil samples below the limits, but not to correct measured analyses that were at or above the limit.
The correction would have little effect on analyses above the limit cnd would add confidence that an ALARA condition was achieved.
A new cet of background soil sampics would be needed to obtain data for opplication to this project.
(These soil release limits were also cpplied to drums of other granular materials; i.
e.,
paint chips, cand, concrete chips, and floor tilo.) (It was recognized that cdditional release limits might be needed for co-60, Cs-137, and U-233.
A decision was made to review soil sample analysis data for cvidence of those isotopes before requesting limits.
The collected data are presented in Section 5.0 and are discussed and evaluated in Section 6.0.
There does not appear to be a need for release limits for these three isotopes.)
The release limit for external beta-gamma exposure is given in Reference 2 and is included in Table 4-2.
This limit can be correct-cd for local background activity.
It was concluded that the beta-gamma activity from natural thorium and uranium and their daughters would not significantly affect survey results, but external beta-gamma activity from the Hot Cells and Building J would have to be 4-1
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I taken into account.
(The Hot Cells are located near the south-west corner of Building B and contain high-level beta-gamma materials.
Located toward the north-east behind Building C, Building J is used for storage of high-level beta-gamma waste.)
A survey in and around Building C for external beta-gamma activity would be needed to obtain data for application to this project.
4.2 Survey Design 4.2.1 Surface Survey Design Most of the laboratories in Phase I had been used for experiments with all three elements of interest - plutonium, uranium, and thorium.
Each Phase I laboratory had been cleaned and repainted more than once so there was a possibility that contamination existed beneata the paint and floor tile.
Prudence dictated stripping walla, floors, and ceilings 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 sur-faces to expose the original surface.
(Paint did not need to be removed from walls that had been erected after cessation of activi-ties with SNM or from walls in areas from which SNM had been exclud-ed.)
A rectangular grid was designed for use on walls, floors, and surfaces with each grid block containing slightly less than 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.
A comprehensive direct alpha survey was planned to include 100% of each grid block and alpha smears were planned 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 direct and indirect (smear) alpha surveys would be conducted immediately after removal of surface coatings to identify areas that would require further decontamina-tion.
When the alpha surveys showed acceptable results, other types of surveys would be conducted.
Beta smears and direct beta and direct gamma surveys were planned for each of 242 randomly selected floor grid blocks in the Phase I area.
This statistical method was chosen for beta-gamma surveys because of the low potential for beta-gamma contamination in Building C.
Since the floor was the most likely place to have been contaminated in case of a spill, only floor grid blocks were selected for the beta-gamma surveys.
4.2.2 External Gamma Survey Design External gamma surveys were planned for each of the 242 randomly selected floor grid blocks in the Phase I area.
This 4-2
1
~
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I represents 30% of the floor grid blocks.
This statistical method was chosen to establish background levels for. comparison with direct gamma surveys taken on the same basis.
d 4.2.3 Soil Survey Design Four separate types of soil surveys were foreseen.
One would be for soil excavated from under the floor and placed in drums.
Another would be for scil samples from the face of an excavation.
A third would be to' determine the extent of contamination identified by the excavation face samples.
The fourth wculd be to establish the concentrations of naturally radioactive isotopes in the site's soil.
The'same analytical procedure could be used for each type, but sam-pling methods would differ.
Since the SNM isotopes are primarily alpha emitters'and.a large number of samples was expected, gamma analyses were plenned based upon known daughters of plutonium, thor-ium, and uranium.
'A sampling method was planned for excavated soil that would obtainh,a\\ uniform quantity of soil for analysis as each drum was filled. l(Thi's; method was also planned for use with other granular' materials; e; g., paint chips, concrete chips, and floor
_ tile.)
A sampling method was planned to obtain samples from the surface of,the excavation 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 drainline system.
The only c_ther pathway for contaminants to enter the soil under the building would be'through the concrete floor.
This type of contami-nation 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.)
s 4.3' Survey Instr:1ments The instruments used'for survey and analysis in Phase I are standard models routinely used by the nuclear industry for this type of work.
The instruments were calibrated in accordance with applic-ig able LRC Technical Procedures using National Bureau of Standards t,raceable sources with the exception of the direct gamma survey instrument.
!^
4.3.1 Surface Survey Instruments d
Each surface survey instrument has a lower limit of detection for the radittion being measured.
This is the lowest level of non-zero activity that it can register.
These limits are defined in the following sections.
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4-3
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 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 sq. cm. Flat Plate Probe or a Model FM-3G 445 sq.
cm. 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 dpm/100 sq.
cm.
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.
Cal-ibration was performed according to Technical Procedure LRC-TP-51 using NBS traccable beta sources.
The lower limit of detection for the PAC-4G for beta detection was 300 dpm/100 sq. cm.
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.
Calibra-tion was done with NBS traceable alpha and beta sources as appropri-ate.
The background level for the smear counters was 0.1 dpm alpha /
100 sq. cm. and 300 dpm beta /100 sq. cm.
4.3.1.4 Direct Gamma Survey Instrument A Geiger-Muller (GM) Survey Meter was used for the direct gamma survey.
Instrument calibration was performed according
.to LRC-TP-50, but the NBS certificate for the calibration source can not be located.
A new source has been obtained and a new calibration will be performed.
The lower limit of detection for the GM meter was about 0.05 mR/hr.
4.3.2 External Gamma Survey Instruments The Geiger-Muller (GM) Survey Meter described above was also used for the external gamma survey.
A Model RS-lli Reuter-Stokes Environmental Radiation Monitor was also_used to measure gamma radiation due to external sources.
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 RS-lll was 1 uR/hr.
l 4.3.3 Soil Survey Instrument A Nuclear Data Corporation high-resolution gamma-ray spectroscopy system using HPGe detectors was used to nondestruc-4-4
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I tively analyze soil samples.
This system is standardized according to Technical Procedure LRC-TP-210.
This spectroscopy system was used to examine a gamma spec-trum 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 it's 59.54-kev peak.
The plutonium concentration was calculated by multiplying the Am-241 concentration by an experimetal-ly determined factor.
(The Pu-239 concentration was directly measur-ed 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 it's Pb-212 daughter's 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.
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 (8).
4.4.1 Surface and External Gamma Surveys surface surveys were conducted according to Technical Procedure LRC-TP-183.
The major steps in this procedure are summarized below.
(1) Mark the surface with 1 sq. m. grid blocks.
Sketch the grid on a data sheet and label each block.
(2) Perform a direct alpha survey with a properly calibrated PAC-4G.
Make sequential measurements in a grid block until the entire block has been surveyed.
Record the location and count on a log sheet.
(3) Take a random 100 sq. cm. smear in each grid block.
Count l
the smears for alpha activity in a properly calibrated proportional counter.
Record the location and count 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 properly calibrated GM meter, locate the point in the grid block with the maximum gamma level.
l Perform a direct gamma survey at this point with a properly calibrated G-M meter.
Perform a direct beta survey at the maximum gamma point in each block with a properly calibrated PAC-4G meter.
Record the location and maximum gamma, direct gammma, and direct beta counts on a data sheet.
i 4-5 l
L
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I (5) Take a 100 sq. cm. smear at the maximum gamma point in each block.
Count the smears for beta activity in a properly.
calibrated proportional counter.
Record the location and count on a data sheet.
4.4.2 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.
Sampling, sample preparation, and sample analysis information and data were recorded on route sheets that followed the sample from the time it was taken through the time it was analyzed.
4.4.2.1 Excavated Soil Technical Procedure LRC-TP-206 describes three techniques for taking samples of excavated soil.
These are all commonly used sampling techniques. (9)
These three techniques allow sampling as the drum is filled or after it has been filled.
(1) Six to eight grab samples can be taken as a drum is filled to form a 4-liter sample.
The multiple samples are obtained to create a composite sample representative of the drum's contents.
(This method was also used with other granular materials besides soil; i.
e.,
paint chips, sand, concrete chips, and floor tile.)
(2) A 4-liter sample can be scooped from the entire length of a filled drum as it is laying on its side.
(3) A sampling thief can be used to obtain a 4-liter sample from a filled drum standing upright.
4.4.2.2 Excavation Survey Technical Procedure LRC-TP-197 describes two techniques for collecting soil samples in excavated areas.
(1) A 4-liter sample can be scooped from the bottom of a trench (no longer than 20 feet) from which a drainline has just been removed to create a sample representative.
(2) A 4-liter sample can be scooped from the surface of a trench to create a sample representative of about 10 square feet.
4-6
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 4.4.2.3 Building C Core Samples Technical Procedure LRC-TP-207 describes the
~
method for taking exploratory cores in the vicinity of contaminated soil to guide further excavation efforts.
A core sampler is used that collects a 4-liter sample per foot of depth.
4.4.2.4 Background Soil Core Samples Technical Procedure LEC-TP-207 also describes the method of taking background soil cores external to Building C.
G 4-7
TABLE 4-1.
ACCEPTABLE SURFACE CONTAMINATION LEVELS a
b b
b Nuclides Average,c,f Maximum,d,f Removable,e,f 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, 2
2 2
Ac-227, I-125, I-129 100 dpm/100 cm 300 dpm/100 cm.
20 dpm/100 cm Th-nat, Th-232, Sr-90, Ra-223, Ra-224, U-232, 2
2 2
I-126, I-131, I-133 1,000 dpm/100 cm 3,000 dpm/100 cm 200 dpm/100 cm Beta-gamma emitters (nuclides with decay modes other than alpha emission or spontaneous c'o fission) except Sr-90 and 2
2 2
others noted above.
5,000 dpm sy/100 cm 15,000 dpm sy/100 cm 1,000 dpm sy/100 cm a Where surface contamination by both alpha-and beta-gamma emitting nuclides exists, the limits established for alpha and beta-gamma-emitting nuclides should apply independently.
b As used in this table, dpm (disintegrations per minute) means the rate of emission by radioactive material as determined by correcting the counts per minute observed by an appropriate detector for background, efficiency, and geometric factors associated with the instrumentation.
c Measurements of average contaminant should not be averaged over more than 1 square meter.
For objects of less surface area, the average should be derived for each such object.
2 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 that area with dry filter or soft absorbent paper, applying moderate pressure, and assessing the amount 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 ' gamma emitters should not exceed 0.2 mrad /hr at 1 cm and 1.0 mrad /hr at 1 cm, respectively, measured through not more than 7 milligrams per square centimeter of total absorber.
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE 4.2 BUILDING C SOIL RELEASE LIMITS AND BUILDING C EXTERNAL BETA-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 Enriched 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 Beta-Gamma Exposure Rate 10uR/hr
- These limits are above background levels.
- The individual soil limits given in this table apply to each clement 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 Phase I, (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.
4-9
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 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-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 SAMPLIFG 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-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 4-10 i
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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I l
5.0 PHASE I SURVEY sSSULTS Building C was used primarily for R&D projects with thorium,
~
Since these are all alpha emitters and only limited information was available about specific usage in the labora-t tories, comprehensive surveys for' direct and smearable alpha contami-l-
nation were conducted on the surfaces of the Phase I area in Building
.C.
Only limited amounts of beta-gamma materials had ever entered Building C, so beta-gamma surveys were conducted on a limited number j,
of randomly selected floor grid blocks.
A survey was perform-ed to establish gamma radiation levels due to sources external to Building C.
The data for these surveys and analyses are described below.
All j
data are contained in the Building C Decommissioning files.
5.1 Surface Surveys 5.1.1 Initial surface Surveys L
Each room was cleaned (SNM and equipment were removed, non-essential' service pipe and duct were removed, and paint and floor tile were stripped) and an initial survey was performed to determine direct and smearable alpha radiation levels on the room's surfaces.
3 2
Tables 5-1 through 5-3 provide summaries of these-initial surface survey results.
The lower limit of detection for the direct alpha survey 1
was 30 dpm/100 sq. cm.
As Table 5-1 shows, 3,987 of the 4,339 grids or 92% were at this level and another 281 grids or 6% were below or i-met the release limit of 100 dpm/100 sq. cm.
About 75% of these 281 i
grids were on the floors with the other 25% on the walls.
No contam-ination was found on the ceilings.
About 2% or 71 grids exceeded the release limit for direct alpha. radiation.
About 70% of these grids were on the walls with the other 30% on the floors.
(The data from i
the pit skew this percentage because 46 of the 71 grids were pit-wall grids.)
Using the ALARA concept,. additional decontamination was per-formed on the 352 grids that were above the lower limit of detection.
Table 5-2 summarizes the 61,458 direct alpha readings that were obtained during the initial surface survey.
Ninety five per cent or 58,421 of these readings were at the lower limit of detection i
and 2,887 or about 5% were below 300 dpm/100 sq. cm.
Less than 1% or 150 readings were above.300-dpm/100 sq. cm. with the highest reading
}
being 9,000 dpm/100 sq. cm.
No smearable alpha radioactivity above 10 dpm/100 sq. cm.
was detected.
The background reading for the smear counter was 0.1 dpm/100 sq. cm.
As shown in Table 5-3, 3,561 of the 4,339 smears or i
82% were at this level.
Of the remainder, 651 or 15% were between 1 and 5 dpm/100 sq.
cm. and the remaining 3% or 127 readings were between 6 and 10 dpm/100 sq. cm.
Alpha smears were taken at random 4
l locations in the front part of Old Central Stores, but~no direct surveys for-alpha radioactivity were performed since radioactive i
]
materials were not handled in this area.
No activity was found.
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PAGE 5-1 4
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I DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 5.1.2 Release Surface Surveys
~
Decontamination was performed in those 352 areas identified in the original alpha survey as being above the limit of detection.
Some areas were more difficult to decontaminate than others.
Removal of 1/16 -1/4 inch of the concrete surface was adequate in most areas, but as much as 5 inches of concrete had to be chipped up in Lab 53.
It was also necessary to remove epoxy paint from the floor in Lab 43 to complete decontamination (even though the floor was painted prior to the use of SNM in this laboratory).
Tables 5-4 and 5-5 provide summaries of the release survey results.
Table 5-4 gives a summary of the release 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 sq. cm. with no grid block exceeding an average of 70 dpm/100 sq. cm.
About 95%
of the grids averaging over 30 dpm/100 sq. cm. were on the floor.
The data summarized in Table 5-5 show that no single reading exceeded 150 dpm/100 sq. cm.
Over 97% of the grid blocks and over 99% of the individual readings had readings at the lower limit of detection of i
30 dpm/100 sq. cm.
In the course of data reduction, the raw direct alpha sur-i vey data were summarized in terms of range, mean, standard deviation, variance, and other simple statistics as needed for estimating popu-lation parameters.
Normal distribution statistics were used as all sample sizes were greater than 100.
Sample means were used as the least biased estimate of the unknown population mean.
Confidence limits were set up on the sample mean to assess the significance or degree of confidence that can be placed on such a value.
As shown in Table 5-6 (which summarizes the data from Tables 5-4 and 5-5), we can be 99.7%' confident that the population mean lies between 30.38 and 30.06 dpm/100 sq. cm. in the case of the grids and between 30.24 and 30.14 dpm/100 sq. cm. in the case of the individual readings.
The 99.7% confidence limit is based on the formula UCL = x(mean) + (z)(c)/JN LCL = x(mean) - (z)(c)//N where z = 3.0 UCL = Upper Confidence Limit LCL = Lower Confidence Limit The data obtained during the original alpha smear survey i
l and shown in Table 5-3 are being used for the release alpha smear survey.
Precautions were taken during decontamination to prevent the spread of contaminated dust and routine large area smears have shown no trace of smearable alpha activity in the Phase I portion of Build-ing C.
No grid had smearable alpha activity greater than 50 percent of the allowable limit of 20 dpm/100 sq.cm.
The alpha smear survey data were statistically analyzed in the same manner as the direct PAGE 5-2 i-
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I alpha survey data.
Table 5-6 contains these results.
Surveys for direct beta, smearable beta, and direct gamma activity were made in randomly selected floor grid blocks.
The re-sults are shown in Table 5-7.
A survey for direct gamma was perform-ed in each of 242 floor grids out of a total of 780 in Phase I.
A gamma radiation reading was taken 1 meter from the floor and another reading was taken less than 1 cm from the floor at the same spot.
Both readings were equal in all 242 cases indicating no residual gamma contamination was present.
(All 484 readings were 0.04 or 0.05 mR/hr.
This is the lower limit of detection for the GM meter.)
Surveys were performed for direct beta and smearable beta activity at the same 242 spots.
As shown in Table 5-7, the beta activity aver-aged 300 dpm/100 sq. cm., well below the limit of 5,000 dpm/100 sq.
cm. for fixed beta activity and the limit of 1,000 dpm/100 sq.
cm.
for smearable beta activity.
(one reading for smearable beta activ-ity was 360 dpm/100 sq. cm.
The other 241 readings were all 300 dpm/100 sq. cm. which is the background level for the beta smear instrument.)
5.1.3 External Gamma Radiation Survey A survey was conducted in and around Phase I to measure the gamma radiation levels due to external sources.
Figure 5-1 shows the results of this survey.
The data show that the Hot Cells in Building B and the high-level waste stored in Building J are the external sources that establish the background gamma radiation inside Phase I of Building C.
The data also support the gamma purvey data shown in Table 5-7.
5.2 Release Soil Survey Samples were taken from drums of soil excavated from under Building C and samples were taken from the face of the excavations.
Samples of site background soil were also taken.
The data are presented in Tables 5-8 through 5-10 for each type of 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 provide 107 samples of background soil.
These samples were analyzed for Am-241, Th-232, Pu, and U. The results are summarized in Table 5-8.
The results for Am-241 and plutonium represent the lower limits of detection for gamma analyses.
These data are being reported here, but do not actually indicate the presense of Am or Pu, but indicate an upper limit for the values if they were present.
The values for uranium and thorium have been used to correct excavation and drum samples for local naturally occurring concentrations of these elements.
PAGE 5-3
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 1
5.2.2. Excavation Release Survey The data are summarized in Table 5-9 for the excavation release soil-survey.
The results for Am-241 and plutonium represent 76 samples in which Am-241 was detected and 203 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 I and identify the relatively uniform concentration of these elements throughout the region.
The calculation of the unity factor was performed with only the Am-241 and Pu values.
To address the possibility of potential U-233 contamination
' in the excavated soil samples, a series of Bateman decay chain calcu-lations were performed to identify a nuclide that would provide a sensitive indication of U-233 concentration in soil.
This nuclide is Pb-212 that is a daughter of the U-232 that is present in the U-233 as a contaminant.
A review of the data from the excavation samples 3
showed that none had Pb-212 activity above that expected from the naturally occurring Th-232 parent.
(Th-232 also produces Pb-212 as well as U-232.)
These results indicate no contamination from U-233..
. A sample of sludge was taken from the storm sewer that lay i
. under Lab 43.
This sample contained 125 pCi co-60/g and 9 pCi Cs-137/g that. originated from material that had leaked into the storm sewer from the Hot Cells. (10)
The excavation soil samples data were reviewed and found to indicate that co-60 and Cs-137 concentrations were all below 1 pCi/g.
Radiation levels were measured with the RS-i 111 in the excavations under Lab 43 and under the Fan Room.
No read-ings above background were found.
These results indicate no contami-i nation from co-60 or Cs-137.
The continued ingrowth of Am-241 was. recognized and evaluated for its effect upon activity levels in the future.
The Am-241 concentration will reach a maximum in about another 65 years.
The maximum Unity Factor for excavation samples would be about 0.25 at that time.
1 5.2.3 Excavated Soil Drums Survey The data are summarized in Table 5-10 for the excavated soil release survey.
There are 989 drums of soil that meet release limits.
The results for Am-241 and plutonium represent 311 samples l
in which Am-241 was detected and 673 samples where Am-241 was reported at the lower limit of detection.
The analyses for thorium
. and uranium indicate primarily background concentrations for these
~ two elements are contained in the releasable drums.
The background q
concentrations for thorium and uranium have been deducted for the calculation of the unity factor for the releasable drums.
The data from analyses of the samples of excavated soil drums was reviewed for Pb-212 content to address the possibility of potential U-233 contamination.
These data showed that 18 drums had l
Pb-212 activity above that expected from the naturally occurring Th-PAGE 5-4 e
-.,.,,,e,
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 232 parent.
A statistical evaluation of both the Pb-212 and Ac-228 activities indicated these 18 samples had equal concentrations of _
l 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-233.
The excavation soil drum samples data were reviewed and found to indicate that Co-60 and Cs-137 concentrations were all below 1 pCi/g.
These results indicate no contamination from Co-60 or Cs-137.
The continued ingrowth of Am-241 was recognized and evaluated for its effect upon activity levels in the future.
The Am-241 concentration will reach a maximum in about another 65 years.
The maximum Unity Factor for excavated soil samples would be about 0.40 at.that time.
There were 709 drums of soil that did not meet release limits.
The results for Am-241 and plutonium represented 694 samples in which Am-241 was detected and 15 samples where Am-241 was reported at the lower limit of detection.
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 709 drums have been shipped to a commercial radwaste burial site for disposal.
5.2.4 Soil Survey Data Analysis The data used to prepare Tables 5-8, 5-9, and 5-10 have been summarized statistically and are presented in Table 5-11.
Exam-ination of Table 5-11 shows that the mean of the excavation samples is less than the 99.7% upper confidence level of the background soil samples for Am-241, plutonium, Th-232, and uranium.
Therefore, we have 99.7% confidence that the concentations of any of these substan-ces in the excavation samples do not statistically exceed their con-centrations in the background soil samples.
The same statement is made for the excavated soil samples.
5.3 Decontamination Waste Survey The data are summarized in Table 5-12 for the decontamination waste release survey.
There were a total of 55 drums of paint chips, concrete chips, floor tile, and sand removed from Phase I during the decontamination of the rooms.
The decontamination waste was sampled and analyzed in the same manner as the excavated soil.
The analyses
!showed that 35 of these drums meet the release limits for unrestrict-ed disposal.
These drums are being retained at the LRC until approv-ed for release.
The other 20 drums have been shipped to a commercial radwaste burial site for disposal.
PAGE 5-5
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE 5
SUMMARY
OF AVERAGE ORIGINAL DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number Numb.r of Grids of Grids 30 30-100
>100
( Werage dpm/100 sq. cm.)
Front Offices 550 2
552 Front Hall 312 3
315 Hall 23 173 1
174 Lab 25 147 1
148 Lab 26*
412 412 Lab 27 553 11 564 Lab 43 366 32 2
400 Lab 44 209 60 11 280 Lab 50 232-36 268 Labs 51 & 52 241 31 272 Lab 53 104 26 12 142 Lab 54 105 37 142 Pit 17 41 46 104 Old Central Stores 566 566 Total 3,987 281 71 4,339
- Data for Lab 26 also includes the Janitor's Closet and Filter Room.
PAGE 5-6
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE 5-2
SUMMARY
OF MAXIMUM ORIGINAL DIRECT ALPHA SURVEY RESULTS
~
Location Direct Alpha Survey Results Total Number Number of Readings of Readings 30 30-300
>300 (hiaximum dpm/100 sq. cm.)
Front Offices 7,055 4
7,059 Front Hall 4,196 5
4,201 Hall 23 2,428 2
2,430 Lab 25 1,943 1
1,944 Lab 26*
5,810 5,810 Lab 27 8,186 29 8,215 Lab 43 5,579 393 7
5,979 Lab 44 3,645 549 20 4,214 Lab 50 4,022 162 4,184 Labs 51 & 52 3,380 265 3,645 Lab 53 1,605 304 19 1,928 Lab 54 1,571 448 2,019 Pit 539 724 105 1,368 Old Central Stores 8,462 8,462 Total 58,421 2,887 150 61,458
- Data for Lab 26 also includes the Janitor's Closet and Filter Room.
PAGE 5-7
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I-TABLE 5-3
SUMMARY
OF ORIGINAL ALPHA SMEAR SURVEY RESULTS
~
~
Location Alpha Smear Survey Results Total Number Number of Grids of Grids 0.1 0.1-5 5-10 (dpm/100 sq. cm.)
Front Offices 439 92 21 552
-Front Hall 234 73 8
315
-Hall 23 161 13 174 Lab 25 130 17 1
148 Lab 26*
367 40 5
412 Lab 27 491 66 7
564 Lab 43 280 78 42 400
--Lab 44 232 45 3
280 Lab 50 211 46 11 268 Labs 51 &:52 233 36 4
272 Lab 53 127 14 1
142 Lab 54 111 24 7
142 Pit 81 19 4
104 Old Central Stores 462 91 13 566
. Total 3,561 651 127 4,339
- Data for Lab 26 also includes the Janitor's Closet and Filter Room.
PAGE 5-8
e DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I
~ TABLE 5-4
SUMMARY
OF AVERAGE RELEASE DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Sury,2y Results Total Number Number of Grids of Grids 30 30-100
>100
( Werage dpm/100 sq. cm.)
Front Offices 552 552 Front Hall 313 2
315 Hall 23 174 174 Lab 25 148 148 Lab 26*
412 412 Lab 27 554 10 564 Lab 43 394 6
400 Lab 44 259 21 280 Lab 50 267 1
268
. Labs 51 & 52 260 12 272 Lab 53 113 29 142 Lab 54 123 19 142 Pit 104 104 Old Central Stores 566 566 Total 4,239 100 4,339
- Data for Lab 26 also includes the Janitor's Closet and Filter Room.
PAGE 5-9
9 DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE 5-5
SUMMARY
OF' MAXIMUM RELEASE DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number Number o_f, Readings of Readings 30 30-300
>300 (iiIaximum dpm/100 sq. cm.)
Front Offices 7,059 7,059 Front Hall 4,197 4
4,201 Hall 23 2,430 2,430 Lab 25 1,944 1,944 Lab 26*
5,810 5,810 Lab 27 8,187 28 8,215 Lab 43 5,955 24 5,979 Lab 44 4,129 85 4,214 Lab 50 4,181 3
4,184
-Labs 51 & 52 3,495 150 3,645 Lab 53 1,770 158 1,928 Lab 54 1,907 112 2,019 Pit 1,368 1,368 Old Central Stores 8,462 8,462 Total 60,894 564 61,458
- Data for Lab 26 also includes the Janitor's Closet and Filter Room.
1 PAGE 5-10
DECONTAMINATION'AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE 5-6 ALPHA SURVEY RESULTS dpm/100 sq. cm.
Direct Alpha Surveys Alpha Smear Surveys
@y Grid gy Reading gy Grid Sample Size 4339 61,458 4,339 Mean-30.22 30.19 0.73 Standard Deviation 3.5 3.6 1.47 Error on Mean 0.053 0.015 0.02 99.7% UCL 30.38 30.24 0.80 99.7% LCL 30.06 30.14 0.66 TABLE 5-7
SUMMARY
OF RELEASE DIRECT BETA AND GAMMA AND SMEARABLE BETA SURVEY RESULTS FOR 242 FLOOR GRID BLOCKS IN PHASE I Direct Gamma Direct Beta Smearable Beta Decision Survey Results Survey Results Survey Results dpm/100 sq. cm. dpm/100 sq. cm.
dpm/100 sq. cm.
Average Value Average Value Average Value 300 300 300 Accept
. Direct Gamma Direct-Beta Smearable Beta Decision Survey Results Survey Results Survey Results dpm/100 sq. cm. dpm/100 sq. cm.
dpm/100 sq. cm.
Maximum Value Maximum Value Maximum Value i
300 300 360 Accept TABLE 5-8 ANALYSES OF BACKGROUND SOIL SAMPLES Number of Activity, pCi/ gram Samples Am-241*
Max v
107 0.33 0.54 1.43 2.33 1.28 2.12 1.40 2.51
e.,
they do not actually indicate the presence of americium or plutonium, but indicate an upper limit for the values if they were present.
PAGE 5-11
~.
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE 5-9 ANALYSES OF EXCAVATION RELEASE SOIL SAMPLES Number of Activity, pCi/ gram Unity Samples Am-241*
- Th-232 Uranium Factor Avg Max Avg Max Avg Max Avg Max Avg Max 279 0.36 1.46 1.56 6.31 1.04 1.75 1.26 2.87 0.06 0.23
- Of the 279 values represented for Am-241 and plutonium in this table, 203 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.
TABLE 5-10 ANALYSES OF EXCAVATED SOIL SAMPLES Number of Activity, pCi/ gram Unity Samples Am-241 Plutonium Th-232 Uranium Factor Avg Max M
Max M
Max M
Max M
Max 989*
0.37 1.71 1.60 7.39 1.13 1.20 1.31 3.78 0.06 0.39 709 98 5,910 423 25,500 4.70 25.2 22.3 1,670 17.1 1,687
- Of the 989 values represented for Am-241 and plutonium in this category, 673 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.
PAGE 5-12
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I TABLE.5-11
~
SOIL _ SAMPLES ANALYSIS RESULTS Am-241 Activity, pCi/g
Background
Excavation Excavated Soil Sample size 107 279 989 Mean 0.33 0.36 0.37 Standard Deviation 0.14 0.16 0.33 Error of Mean 0.01 0.01 0.01 99.7% UCL 0.37 0.39
~
0.40 99.7% LCL 0.30 0.33 0.34 Plutonium Activity, pCi/g
Background
Excavation Excavated Soil Sample Size 107 279 989 Mean 1.43 1.56 1.60 Standard Deviation 0.69 0.69 1.43 Error of Mean 0.06 0.04 0.05 99.7% UCL 1.60 1.68 1.73 99.7% LCL 1.26 1.44 1.46 Th-232 Activity, pCi/g
Background
Excavation Excavated Soil Sample Size 107 279 989 Mean 1.28 1.04 1.13 Standard Deviation 0.27 0.18 0.24 Error of Mean 0.03 0.01 0.01 99.7% UCL 1.35 1.07 1.16 99.7% LCL 1.21 1.01 1.11 Uranium Activity, pCi/g
Background
Excavation Excavated Soil Sample Size 107 279 989 Mean 1.40 1.26 1.31 Standard Deviation 0.33 0.33 0.40 Error of Mean 0.03 0.02 0.01 99.7% UCL 1.47 1.32 1.35
.99.7% LCL 1.32 1.20 1.27 PAGE 5-13
DECONTAMINATION AND~ DECOMMISSIONING OF BUILDING C - PHASE I TABLE 5-12 ANALYSES OF DECONTAMINATED WASTE SAMPLES Number of Activity, pCi/ gram Unity Samples Am-241 Plutonium Th-232 Uranium Factor A3 Max A_vg Max A3 Max A_vg Max Avg Max 35 0.28 1.00 1.21 4.32 0.31 1.54 1.97 7.56 0.17 0.55 20 21 235
'91 1,015 ~1.66 9.29 24 118 4.50 37
?
i l
e f
I PAGE 5-14
o.
FIGURE 5-1.
EXTERNAL GAMMA SURVEY, pR/ HOUR (Survey Conducted With RS-111 Environmental Monitor) 55 67 72 80 75 13 0 69 78 85 93 90 148 FV1
,Y1 L
m f
,v, 66 77 87 95 110 143 186 169 156 77 M
"U" E,
67 80 87 88 109 135 158 165 134 72 ilo 1 31 14 6 117
_58 y
v1 m
Pv g
40 35 23 24 25 18 35
~
66 74 80 77 p -f
=.:mn.->,
M 29 e tag 235 22L==J ) 6 2 54
- 5 ' -14 9
d 00
,, _l =. g 65 70 65 44 29 15 i
i3 l'6 20 "
16 59 48 39 j
f" T l/~~ T AW T
NTN Nfl)"
s==='
l =8,
qLL
__L pl
_J a
=9 42 45 44 38 29 28 24 28 26 25 29 25 42 45 43 37 40 40 El 24 54 43 46 49 52 52 49 51 51 60 56 46 34 39 56 C5 43 25 45 53 56
+
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I 6.0 SURVEY INTERPRETATION An extensive decontamination program was conducted throughout '
Phase I of' Building C.
Based on the survey results shown in Section 5.0,-Phase I meets or surpassess all applicable release limits and can be released for unrestricted use pending approval by the NRC.
Comprehensive surveys were performed on the room's surfaces to measure direct and smearable alpha radioactivity.
A statistical sur-vey was performed for beta-gamma radioactivity.
Fixed alpha contami-nation was the primary surface contamination found in Phase I with most of the readings (71%) 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 I of Build-ing C.
Excavation of soil under the drains continued until samples from the surfaces of the excavation demonstrated release limits had been met with most of the samples (72%) being at background concentrations.
A total of 1,688 55-gallon drums of soil were excavated.
The 702 drums of contaminated soil were shipped to a licensed commercial radwaste burial site for disposal.
The remaining 982 drums of soil are being retained at the LRC until approved for release.
The scope of the decontamination project and the procedures, equipment, and analyses applied give strong assurance that the measured values of residual radioactivity are representative of-Phase I and all release limits have been met.
Thus, the decontami-nation and decommissioning project for Phase I has been successfully completed.
Therefore, upon the concurrence of the NRC, Phase I will be released for unrestricted use.
{
i PAGE 6-1
DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE I
7.0 REFERENCES
1.
Docket No. 070-00824, NRC Materials License SNM-778, as renewed, Expires July 31, 1985.
2.
Memo, A.F. Olsen, B&W, to W.T.
Crow, NRC, " Decommissioning Plan for the Lynchburg Research Center's Building C",
March 28, 1983.
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.
e 5.
D.A. Edling and J.F. Griffin, " Certification of ERDA Contract-ors' Packaging with Respect to Compliance with DOT Specification 7A Performance Requirements, Phase II Summary Report", MLM-2228, June 12, 1975.
6.
Department of Transportation Hazardous Materials Regulations, Title 49 CFR Part 178.118, Specification 17H; steel drums.
7.
NRC Materials License No. 16-19204-01, Ammendment No. 4, Expires November 30, 1985 and State of Washington Radioactive Materials License WN-1019-2, Expires November 30, 1985.
8.
NUREG/CR-2082, " Monitoring for Compliance with Decommissioning Termination Survey Criteria" with Appendices I through VII, June 1981.
9.
Arthur F. Taggart, " Handbook of Mineral Dressing, Ores and Industrial Minerals", John Wiley & Sons, Inc. 1927, 10.
Memo, A.
F. Olsen, B&W, to W. T.
Crow, NRC, " Soil Decontami-nation Plan", October 12, 1981.
PAGE 7-1