ML20205F137
| ML20205F137 | |
| Person / Time | |
|---|---|
| Site: | 07000824 |
| Issue date: | 06/30/1986 |
| From: | BABCOCK & WILCOX CO. |
| To: | |
| Shared Package | |
| ML20205F129 | List: |
| References | |
| RDD:87:8665-19:, RDD:87:8665-19:3, NUDOCS 8608190097 | |
| Download: ML20205F137 (67) | |
Text
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FINAL SURVEY REPORT FOR
~
RELEASE OF BUILDING A FROM THE SNM-778 LICENSE AT LYNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA REPORT NO.
RDD:87:8665-19:3 JUNE 1986 BABCOCK & WILCOX LUNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA 8608190097 860619 PDR ADOCK 07000824 C
On FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 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 2.2 Building A Physical Description 2-1 2.3 Definition of Building A/ SNM-778 2-2 2.4 History of Operations in Building A 2-2 3.0 DECONTAMINATION OPERATIONS 3-1 3.1 Preparation of Rooms for Survey 3-1 3.2 Drain Lines 3-3 3.3 Roof 3-4 3.4 Soil Excavation 3-4 3.5 Waste Disposal 3-4 4.0 SURVEY DESIGN AND PROCEDURES 4-1 4.1 Release Criteria 4-1 4.2 Survey Instruments 4-1 4.2.1 Surface Survey Instruments 4-2 4.2.2 Instruments Used for Additional Gamma Surveys 4-2 4.2.3 Soil / Paint Chip Survey Instrument 4-3 4.3 Survey Design 4-3 4.3.1 General 4-3 4.3.2 Surface Surveys 4-4 4.3.3 Additional Gamma Surveys 4-9 4.3.4 Soil Surveys 4-9 I-1
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FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE OF CONTENTS 5.0 LICENSE CX-10 AREA 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 Paint Chip Samples 5-3 5.2 Gamma Radiation Survey 5-3 5.3 Release Soil Survey 5-4 5.3.1 Background Soil Survey 5-4 5.3.2 Ditch Face Release Survey 5-4 6.0 SURVEY INTERPRETATION 6-1 6.1 Floors, Walls and Roof 6-1 6.2 Paint Chip Samples 6-3 6.3 Ventilation System and Other Surfaces 6-5 6.4 conclusions 6-5
7.0 REFERENCES
7-1 1
{
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FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE LIST OF TABLES Table Page 4-1 Acceptable Surface Contamination Levels 4-12 4-2 Soil Release Limits and External Beta-Gamma Exposure Limit 4-13 4-3 LRC Technical Procedures Used for Building A Decommissioning Operations 4-14 5-1 Summary of Original Direct Alpha Survey Results (Grid Average) 5-5 5-2 Summary of Original Direct Alpha Survey Results (Individual PAC-4G Readings) 5-6 5-3 Summary of Original Direct Beta Survey Results (Grid Average) 5-7 5-4 Summary of original Direct Beta survey Results (Individual PAC-4G Readings) 5-8 5-5 Summary of Alpha Smear Survey Results 5-9 5-6 Summary of Beta Smear Survey Results 5-10 5-7 Summary of Final GM Meter Survey Results (Grid Averages) 5-11 5-8 Summary of Final GM Meter Survey Results (Individual GM Meter Readings) 5-12 5-9 Summary of Final Direct Alpha Survey Results (Grid Averages) 5-13 5-10 Summary of Final Direct Alpha Survey Results (Individual PAC-4G Readings) 5-14 5-11 Summary of Final Direct Beta Survey Results (Grid Averages) 5-15 5-12 Summary of Final Direct Beta Survey Results (Individual PAC-4G Readings) 5-16 5-13 Summary of Paint Chip Gamma Analysis Results 5-17 5-14 Summary of Final Gamma Survey Results 5-18 I-3
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE LIST OF TABLES 5-15 Analyses of Background Soil Samples 5-19 5-16 Acceptance Limits for Background Soil Activities 5-19 5-17 Analyses of Ditch Face Soil Samples 5-20 6-1 Floors / Walls-Storage Bldg.,SA 1, Vault, 6-2 Old HP, CR, Penthouse 6-2 Other Indoor Horizontal Walking Surfaces 6-2 6-3 Roof and Outside Walls 6-3 I-4
' FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE LIST OF FIGURES Figure Page 2-1 Babcock & Wilcox Property - Mt. Athos 2-4 2-2 Lynchburg Research Center Plan of Buildings 2-5 2-3 Building A Construction History-First Floor 2-6 1-4 Building A Construction History-Second Floor 2-7 2-5 Building A Floor Plan With License Boundaries-First Floor 2-8 2-6 Building A Floor Plan With License Boundaries-Second Floor 2-9 3-1 Building A Hot Drain System 3-6 4-1 Typical Surface Grid Arrangement 4-16 4-2 Building A Cold Drain System 4-17 4-3 External Gamma Survey 4-18 1
l I-S 1
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE
1.0 INTRODUCTION
1.1 Statement of the Problem The Babcock & Wilcox Company (B&W), a wholly owned subsidiary of McDermott International, Inc., holds NRC License SNM-778 (1) to conduct operations involving Special Nuclear Material (SNM) at its Lynchburg Research Center (LRC) near Lynchburg, Virginia.
Under this license, a variety of SNM, source materials, and by-product materials were used in Building A at the LRC.
A corporate decision was made in 1983 to discontinue Research and Development (R&D) activities with radioactive materials in Building A.
A decommissioning plan for Building A 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.
1.2 Statement of the Objective The objective of the decommissioning project was to decontaminate Building A 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 were maintained in achieving this objective, work was performed according to QA Plan NO.
85009L (3).
The decontamination included the interior and exterior surfaces of Building A and the contiguous soil systems.
As described in Reference 2, numerical limits for surface contamination are those presented in Reg. Guide 1.86 (4).
Additional numerical limits for external exposure and soil contamination I
are also contained in Reference 2.
B&W used these limits as minimum goals to achieve during decontamination, but followed the principle of reducing contamination to ALARA (As Low As j
Reasonably Achievable) levels.
1.3 Organization of this Report This report contains seven sections that describe the decommissioning work performed during the Building A project.
Following this introductory section, a physical description of the site and Building A is provided.
Information is provided in Section 3 about the decontamination and decommissioning operations themselves. The fourth section contains descriptions of the survey design and survey procedures used to determine residual radioactivity in 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.
1-1
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 2.0 IDENTIFICATION OF PREMISES 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 2
sice.
l The LRC is a highly integrated facility built to j
develop, test, and examine nuclear reactor cores and to develop overall nuclear fuel cycles.
The location of 1
Building A is shown in Figure 2-2 relative to the other j
buildings comprising the LRC 2.2 Buildina A Physical Description e
.The existing structure known as Building A is the result of several additions to a small laboratory completed in 1956 (see Figures 2-3 & 2-4).
The original building consisted of i
a heavily shielded high bay, a sub-assembly room used in the preparation of reactor experiments, a counting room, health physics laboratory, a reactor control room, electronics shop,
-j physics laboratory, rest rooms, offices,and an adjacent storage building.
This structure also included a penthouse on the building roof.
The penthouse outline is indicated by the dashed line on Figure 2-6.
The location of the storage j
building is illustrated in Figure 2-2 at the south end of Building A.
The shielded bay housed two low power critical i
facilities, CX-1 and CX-19.
The other laboratories and j
offices were operated in support of the reactors.
The first addition to Building A (designated "FIRST 1
ADDITION" in Figures 2-3 & 2-4) was made in 1957.
This j
addition has two floors, and was built under the CX-10 Construction Permit (5).
The first floor was comprised of a heavily shielded high bay, a rest room, Sub-Assembly room, l
physics laboratory, and offices.
The second floor, which is an extension of the original building, consisted of the high bay area (Bay 2), a storage room, control room, chemistry laboratory, electronics shop and offices.
Bay 2 was constructed to house two low-power critical experiment reactors, CX-10 and CX-12.
The second addition to Building A (designated "SECOND l
ADDITION" in Figures 2-3 & 2-4) was made in 1958.
This was a j
two-floor addition which housed a pool-type reactor that was j
originally licensed in September, 1958 for 200 kW operation, j
which was later increased to 1 MW.
The first floor consisted l
2-1 i
i.
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE of an open work area and the lower portion of the reactor pool.
In 1962, an autoclave was added with its associated heat exchanger, pumps and valves in this area.
The second floor was comprised of the upper portion of the pool, the control room area and later, the autoclave control panel area.
The first and second floors, a heat exchanger room and a cooling tower were licensed under AEC License R-47.
These areas were released for unrestricted use and the license terminated on July 20, 1982.
The third addition to Building A (designated as " THIRD ADDITION" in Figures 2-3 & 2-4) was begun in 1963.
This two-floor addition was not used to handle licensed material.
The first floor was originally a single storage room but is now two computer areas.
The second floor consists of offices and a conference room.
2.3 Definition of Building A [ SNM-778 Decontamination of Building A has been completed in several phases.
In the first phase, the areas designated e
" Released 1982" in Figures 2-5 and 2-6 were released for unrestricted use when License R-47 was terminated in July, 1982.
The second phase was the area designated as "CX-10" in Figures 2-5 and 2-6, and its decontamination was discussed in a report issued to NRC in June 1986(6).
The third phase is covered by this report and is the area designated as "SNM-778" in Figures 2-5 and 2-6, and includes the areas designated as " Penthouse" and " Storage Building".
The area of Building A / SNM-778 covered by this report includes Bay 1 (basement and first floor), offices numbered 1 to 12 inclusive, two rest rooms, drafting (subassembly room
- 1), storage (vault), counting room, Xerox room (old HP office), the penthouse and a small storage building located l
to the south of Building A.
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2.4 History of Operations in Building A The first building (designated as " Original Building")
contained Bay 1, which housed two low power tank-type critical experiment reactors.
The CX-1 reactor license was issued on March 20, 1957. and the CX-19 license was issued on January 22, 1958.
Both of these reactors ceased operation in 1971.
Authorization from the Atomic Energy Commission to dismantle these facilities was received on March 8, 1973.
Subsequent to a confirmation inspection, the facility licenses were terminated by the AEC and released for unrestricted use on June 6, 1973.
Bay 1 was then added to areas under control of SNM-778.
Except for short-term storage of a single sealed source, no radioactive material has been used or stored in Bay 1 since the decommissioning.
The Sub-Assembly room (most recently a drafting room) 2-2
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE i
was a use and storage area associated with the CX-1 critical facility.
Large quantities of highly enriched urania powder and metallic thorium were used to construct plate type fuel assemblies in one of the first programs performed under CX-1.
The highly enriched urania powder was also recovered in the Sub-Assembly room after the critical experiments were completed.
Because of these operations, step off lines and a separate air handling system were provided to isolate this room from the rest of the facility.
After the transfer of Bay 1 to the control of SNM-778, the equipment in the Sub-Assembly room was decantaminated and removed, portions of the ventilation system were replaced, and the area i
decontaminated.
i The counting room has been used for counting irradiated foils and wires in connection with the reactors at the LRC.
No basic change has been made to the room since its construction.
The one-room building at the south end of Building A was used for the storage but not the handling or processing of licensed material.
No licensed material has been stored in this building since the CX-1 and CX-19 reactor 1
l decommissioning.
The offices designated 5, 6, 7, 8 and 9 comprise an area i
that was originally constructed as an electronics shop and physics laboratory.
When the first addition was constructed, the electronic shop was relocated in the area occupied by Offices E, F and G. The physics laboratory was then enlarged to fill the vacancy created.
Licensed material was not handled in the physics laboratory and only sealed sources used in instrument calibration were handled in the electronics shop.
The first addition (designated as "CX-10") contained Bay 2, which housed two low-power critical experiment reactors, CX-10 and CX-12.
The CX-12 license was issued September 29, 1958, and terminated in 1971.
Bay 2 and its associated control room and basement are under the purview of License CX-10 which was issued on January 27, 1958.
Operation of this facility ended in September 1983.
The CX-10 facility has been dismantled, and NRC has been requested to terminate i
the CX-10 license and release the first addition from licensed control (5).
At the time of this writing, that request is still pending.
The areas in the second addition (designated as
" released 1982") were released for unrestricted use when l
License R-47 was terminated in July 1982.
The areas in the third addition were not designated for the handling or storage of licensed material.
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FINAL SURVEY REPORT FOR RELEASE OF BUILDING A 4
FROM THE SNM-778 LICENSE i
3.0 DECONTAMINATION OPERATIONS I
j Since the termination of the CX-1 and CX-19 reactor t
licenses,the only licensed materials used or stored in the j
areas covered by this report were in the form of sealed sources or metallic counting foils and wires.
These were j
handled only in Sub-assembly 1, the vault, or the counting room.
Therefore, little decontamination was needed.
The i
exceptions to this rule were the hot drains and the air handling systems associated with Sub-assembly 1.
Substantial work was done removing low-level contamination from these surfaces.
i The extent of planned cleanup in each room varied according to the activities previously performed there.
For example, floor tile, mastic, and ceiling tile were removed in i
Sub-assembly 1 to expose original surface; on the other hand, office areas that were never used for handling or storing radioactive material were hardly affected, except for the
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rearrangement of furniture to provide access for the survey of horizontal walking surfaces.
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The decontamination / cleanup plan also considered the i
statistical nature of the release survey.
Because the final I
radiological condition of the facility was to be inferred
]
from a random sample survey population, care was taken to l
ensure that the entire surface of each survey stratum was i
uniformly cleaned.
If surveys showed spots of contamination, j
the contaminated region was defined and cleaned.
Releasability of the surface was then based on a 100%
resurvey of the affected surface, or on the as-found (i.e.,
pre-cleaning) contamination levels.
The survey equipment and procedures are described in Section 4.0.
3.1 Preparation of Rooms for Survey i
In Sub-assembly 1 and the vault, all equipment was removed.
Since this equipment had been installed after j
cleanup of the area and its return to general use, the equipment (drawing boards, furniture, etc.) was not surveyed.
The ceiling tiles were taken down, and the floor tile was removed.
The floor tile mastic was removed to expose the bare concrete floor.
The room surfaces were then surveyed as described is Section 4.0.
j In the xerox room (old HP office), all equipment was I
removed.
The original tile floor was still present.
Wax was stripped from the floor and all loose tiles were removed, surveyed, and disposed of accordingly.
The ceiling tile was also removed.
The room surfaces were then surveyed as described in Section 4.0.
The counting room was the only area where licensed material was still being stored when this project began.
All 3-1
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE licensed material (sealed sources, counting foils, etc.) were removed and disposed of as radioactive waste.
All equipment including the cold sink and work benches were surveyed and removed to provide access to the entire floor surface.
The original tile surface was still present.
Wax was stripped from the floor and all loose tiles were removed, surveyed and disposed of accordingly.
The room surfaces were then surveyed as described in Section 4.0.
Equipment in the Bay 1 basement was moved to provide access to the floor, which was swept and vacuumed.
Initial surveys in the Bay 1 basement revealed some low level contamination on the concrete floor.
The contamination was well below the release limits specified in Section 4.0, and it wasn't clear whether this contamination was naturally occurring radioactivity or residual licensed material.
Nevertheless, the entire floor surface was cleaned with wax stripper (to remove residual sealant) and given a 100% survey as described in Section 4.0.
In addition, the sludge in the Bay 1 basement sump was removed, surveyed, dried and disposed of as radioactive waste.
A needle-descaler was used to remove a layer of concrete from the bottom and sides of the sump before the final survey described in Section 4.0.
The Bay 1 sump pump was removed, dismantled and surveyed before reinstallation.
The associated drain lines were surveyed as described in Section 4.0.
i The Building A Penthouse was not used for the handling of radioactive material, but was used for long term equipment storage.
Equipment from areas throughout LRC were stored here.
All equipment stored in the Penthouse was surveyed.
No items with removable contamination were found, but a few with low-level fixed contamination were found.
Contaminated items were decontaminated or disposed of as radioactive waste.
The equipment was then rearranged to provide access to the floor and walls, which were swept, vacuumed, and surveyed as described in Section 4.0.
A fire occurred in a uranium glove box off gas system in 1958.
The off-gas blower, motor, and ductwork were checked for contamination.
The off-gas system ductwork was replaced immediately after the fire, and no contamination was found in it.
The off-gas blower and motor, however, were found to be contaminated and were disposed of as radioactive waste.
These were located in the Building A Penthouse.
Because of the contamination found in the blower, all room surfaces near it were also checked for contamination.
Horizontal overhead surfaces in the Penthouse ceiling were found to be contaminated with uranium.
All contaminated surfaces were decontaminated with cloth towels soaked in an aqueous i
solution containing detergents, chelating reagents and other i
active cleaning agents.
These surfaces were then surveyed as described in Section 4.0.
i 3-2
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE The HVAC system for the Sub-assembly 1, which is a separate system from the other systems serving Building A, was also located in the Penthouse.
Initial surveys showed that the interior of this ductwork contained low level uranium contamination.
The ductwork was dismantled, wrapped, and transferred to sub-assembly 1, where it was decontaminated with the same aqueous solution used to clean the Penthouse overhead surfaces.
The air handling unit itself was packaged and disposed of as radioactive waste.
(The decontaminated ducting will be re-installed with a new air handling unit.)
The storage building at the south end of Building A was used for the storage but not for the handling or processing of licensed materials.
All equipment was removed from this building to provide access to the floors and walls for survey.
Low level alpha contamination was found in one area on the concrete floor and an adjacent cinderblock wall.
The residual alpha levels were below the release limits specified in Table 4.1, but additional decontamination was performed in the interest of ALARA.
Using the same method described for the Bay 1 basement floor, the storage building floor was decontaminated and the surface was resurveyed as described in Section 4.0.
A pneumatically driven needle-descaler was used to decontaminate the cinderblock wall, which was also resurveyed as described in Section 4.0.
3.2 Drain Lines Because of the work performed in Sub-assembly 1 in the 1950's, there was a possibility of finding low level alpha contamination in the hot drainlines serving this area (there were no other designated hot drains in this portion of Bldg.
A).
Accordingly, tight fitting cloths were pulled through the hot drainlines to check for contamination.
Preliminary smears of the first few feet of the drains showed no measurable contamination.
More thorough smears were then i
performed by pulling the smear cloths through the entire i
length of each former hot drain.
These cloths were surveyed with the portable beta and alpha gas flow proportional counters described in Section 4.2.
No beta activity above background was found.
The smears did show alpha activity above background.
Assays with the germanium gamma spectrometer (Section 4.2) showed that the contaminant was highly enriched uranium.
The total amount of uranium activity was never more than a few hundredths of a microcurie.
When this activity was normalized by the drain line area smeared, the activity per unit surface area was always less than the limit for removable activity listed in Table 4.1.
Nevertheless, in the interest of ALARA, it was decided to decontaminate the hot drains as much as possible.
The hot drains, which were made of steel, were decontaminated by pulling durable cloth towels dipped in an 3-3
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE aqueous solution containing detergents, chelating reagents and other active cleaning agents through the entire length of each contaminated drain.
Care was taken to ensure that each towel fit very tightly in the drain for maximum scrubbing effect.
The cleaning towels were dried and surveyed.
This was repeated until the towels could be pulled through the drainline without being soiled and without being detectably contaminated.
A final survey as outlined in Section 4.0 was then performed.
Figure 3-1 shows the location of the hot drain system.
As discussed in Section 4.0, cold drains in areas where licensed materials were used or stored were also checked for contamination.
Cold drains in Bay 1, Sub-assembly 1, counting room, old HP office, storage building and the Penthouse (including Sub-assembly 1 air handling system condensate drain) were checked.
Only the drain in the storage building was contaminated.
(This drain did not empty onto a sanitary or storm sewer system; it emptied onto the ground behind the storage building.)
This drainline was decontaminated as described above and surveyed as described in Section 4.0.
3.3 Roof The Penthouse roof in the vicinity of the Sub-assembly 1 off-gas vent has found to have measurable surface alpha contamination. Samples of the roof gravel were counted on the gamma spectroscopy system described in Section 4.2, which showed that the contaminant was highly enriched uranium.
All contaminated gravel was removed, packaged, and disposed of as radioactive waste.
3.4 Soil Excavation soil was excavated where the storage building's contaminated drain emptied onto the ground.
The soil was assayed on the gamma spectroscopy system described in Section 4.2, and was found to contain slight uranium and thorium contamination.
A 3 ft. by 3 ft. by 6 in. volume of soil was removed, packaged, and disposed of as radioactive waste.
The entire excavation surface was sampled and found to be at background.
3.5 Waste Disposal All radioactive sources, decontamination materials, I
contaminated sludge, equipment that was contaminated above the Table 4.1 release limits, and soil that was contaminated above the Table 4.1 release limits, were packaged and disposed of as radioactive waste in accordance with 3-4
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE applicable NRC and DOT regulations.
Soil that was sampled and found to be below the Section 4.1 release limits is being retained at LRC for unrestricted disposal after the verification survey has been completed by NRC.
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FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 4.0 SURVEY DESIGN AND PROCEDURES R&D projects performed in the reference area of Building A involved the use of thorium and uranium fuels.
The survey plan was based on inspecting surfaces for alpha, beta and gamma contamination and analyzing materials for gamma contamination.
Sampling was planned according to NUREG/CR-2082 (7) to assure that no area remained that contained radioactivity above release limits established by the NRC.
The effect of naturally occurring isotopes at the LRC site was taken into account during planning and surveying.
4.1 Release Criteria s
The release criteria applicable to the Building A area surfaces were obtained from the Building A Decommissioning Plan and Reg. Guide 1.86.
These limits are reported in Table 4-1.
From previous background measurement experience within i ~
and arcund the buildings at LRC, it was concluded that the small. natural background surface alpha activity from thorium andxuranium and their daughters would not significantly affect the decontamination effort required to achieve the release limits.
Therefore, the surface decontamination work for this area was based on the conservative use of gross alpha activity to satisfy the surface release limits of Table 4-1 for unrestricted use.
Background corrections were used for the beta and gamma survey instruments.
Release limits for the soil are provided in the Building A Decommissioning Plan and summarized in Table 4-2.
These limits can be corrected for the naturally occurring thorium and uranium.
Plans were made to correct the analyses for soil samples below the limits, but not to correct analyses that were at or above the limit.
The correction would have little effect on analyses above the limit and would add confidence that an ALARA condition was achieved.
A set of background soil samples was used to obtain data for application to this project.
Survey results are presented and discussed in Sections 5.0 and 6.0.
4.2 Survey Instruments The instruments used for survey and analysis in Building A are standard models routinely used by the nuclear industry for this type of work.
Most instruments were calibrated in accordance with applicable LRC Technical Procedures.
l Instruments for which an approved LRC calibration procedure was not available were sent to a QA-approved vendor for calibration.
All calibrations were performed with National Bureau of Standards traceable sources.
l' l
4-1 i
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 4.2.1 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.
4.2.1.1 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-21 50 cm2 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 200 dpm/100 cm2 for the small probe, and about 25 dpm/100 cm2 for the large area probe.
4.2.1.2 Direct Beta Survey Instrument Separate Eberline PAC-4G-3 instruments using AC-21B 50 cm2 probes 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 about 400 dpm/100 cm2, 4.2.1.3 Alpha and Beta Smear Survey Instruments A Beckman Widebeta II smear counter was used to count 100 cm2 alpha and beta smears.
This instrument was calibrated using Technical Procedure LKC-TP-271 using NBS i
traceable sources.
The background levels for this instrument correspond to 0.3 dpm (alpha) and 2 dpm (beta).
Smear cloths
("large area smears") that were too large to ccunt in the Beckman smear counter were assayed with the PAC-4G l
instruments described above.
4.2.1.4 Surface Gamma Survey Instruments 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.
4.2.2 Instruments used for Additional Gamma Surveys A Model RSS-111 Reuter-Stokes Environmental Radiation Monitor and an Eberline PRM-7 (micro R meter) were used to measure gamma radiation one meter above surfaces.
These measurements were taken both inside and outside Building A.
These monitors were calibrated by the J
4-2
1 1
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE manufacturers with NBS traceable sources.
The lower limit of detection for each was 1 nR/hr.
4.2.3 Soil / Paint Chip Survey Instrument A Nuclear Data Corporation high-resolution gamma-ray spectroscopy system using HPGe detectors was used to nondestructively analyze soil samples.
This system was standardized according to Technical Procedure LRC-TP-210.
This system was also used to analyze paint. chip samples.
For this application, calibration was performed according to LRC-TP-275.
This spectroscopy system was used to examine a gamma spectrum from about 50 kev to about 2 MeV.
Radionuclide concentrations were measured by analysis of gamma-ray energies within this range.
This system was also used to assay and identify radionuclides for a variety of other sample types as needed.
4.3 Survey Design 4.3.1 General The history of operations in the reference portion of Building A suggested that residual contamination levels would be very low.
Bay 1 had already been inspected and released from the reactor licenses by the AEC.
- Moreover, the fuel used in this area was in sealed form; no processing of the fuel was performed in Bay 1.
The only use of licensed material in Bay 1 after termination of the reactor licenses was temporary storage of a sealed source.
Sub-assembly 1, where one program involving extensive processing of highly enriched uranium oxide powder had taken place in the 1950's, had been isolated from the rest of Building A during this operation.
In addition, this area had been cleaned and returned to general use since that time.
The Old HP Office (more recently the xerox room) had also been cleaned and returned to general use.
The only room whose function had been essentially unchanged when this i
project began was the counting room, which had been used for the counting of activated foils and wires.
Small sealed sources had been stored here as well.
The materials handled here were not likely to result in significant surface contamination.
All other areas in which licensed material was used or stored had been cleaned and put to general laboratory or office use.
The final termination survey consisted of a stratified random sampling program that took into 4-3
~
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE consideration the likelihood of finding contamination or activation in various areas throughout the facility, and the type of contamination or radiation that might be found.
The surface survey design was based on the recommendations in Section 3 of Reference 7.
Figure 4-1 shows a typical grid arrangement.
Where indicated by survey results, decontamination and expanded surveys were performed to ensure that no significant contamination was left behind.
Additional gamma surveys were performed to provide baseline gamma radiation levels and ensure that all areas met release limits.
The soil survey design was similar to that described in Reference 9.
More detailed descriptions of the surveys are presented in tha following sections.
4.3.2 Surface Surveys The following surface survey strata were identified:
(1)
Counting room, Old HP Office, Penthouse, and the storage building floors, including walls up to two meters above the floor and selected overhead areas.
(2)
Sub-assembly 1 and vault floors, walls, and ceilings.
(3)
All horizontal walking surfaces other than the rooms in items (1) and (2) shown in Figure 2-5
& 2-6.
(4)
Ventilation ductwork.
(5)
Former_ hot drainlines.
(6)
Outside walls and roof.
Several technical procedures were written for the l
survey of these surfaces.
These include LRC-TP-239, -269, l
-271, -275, -276, -278 and -282.
A more detailed description i
of the surveys for each surface follows.
4.3.2.1 Survey of Counting Room and Old HP Office (xerox room) l The major steps in the survey of these surfaces are summarized below:
(1)
Mark floor surfaces with grids up to one meter on an edge.
Mark walls (up to two meters above the floor) with grids up to two meters on an edge.
1 4-4
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE Sketch and label grid pattern on data sheet.
(2)
Survey a minimum of five locations in each grid with a properly calibrated PAC-4G a meter, PAC-4G meter and GM survey meter.
Select survey locations that have the highest potential for contamination, otherwise uniformly disperse survey locations.
If any readings above background are found, increase scope to identify boundary of contaminated area.
Record results on data sheet.
(3)
Smear the entire grid with absorbent cloth and survey the smear cloth with properly calibrated PAC-4G a meter and PAC-4G S meter.
Record results on data sheet.
(4)
Take a 100 cm2 smear on each grid.
This shall be taken from the area with the highest direct c/S survey.
Otherwise, choose smear locations at random.
Count each smear for alpha and beta activity on a properly calibrated proportional counter.
Record the result on a data sheet.
(5)
Collect a paint chip sample from each grid on a painted surface.
This sample should be taken from the area with highest GM survey meter reading.
Otherwise, choose paint chip sample location at random.
Using properly calibrated PAC-4G cand survey meters, survey the paint chip sample location after collecting the sample.
Analyze the paint chip sample on a properly calibrated gamma spectrometer.
Record the direct survey results on a data sheet and the gamma analysis result on the paint chip sample route sheet.
(6)
Using a calibrated PRM-7 or RSS-lll, measure the gamma radiation level one meter (or less) above each grid block.
The following additional surveys were also performed:
i (1)
A fume. hood had been located in the Old HP Office.
The hood and its exhaust were removed some time ago when this area was converted to general laboratory use.
The penetration in the roof where the hood exhaust was located had been patched.
The ceiling and overhead fixtures in the area where the hood exhaust had penetrated the building roof were surveyed.
Direct alpha and beta surveys and removable alpha and beta surveys were performed.
Results were documented and recorded on survey maps and data sheets.
l 4-5
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE (2)
Several penetrations were located in the floors and walls of the counting room.
The floor penetration had been used for the storage of sealed sources, and the wall penetration (between Sub-assembly 1 and the counting room) had been used as a beam collinator.
The wall penetration was surveyed for direct and removable alpha and beta contamination, and was also surveyed with the GM survey meter.
The floor penetrations were too small for direct and S surveys, but they were checked for removable and contamination.
Surveys with the calibrated GM survey meters were also performed.
Results were documented and recorded on survey maps and data sheets.
4.3.2.2 Survey of Sub-assembly 1/ Vault The major steps in the survey of these surfaces were identical to the steps described in 4.3.2.1, with two exceptions:
(1)
Because of the discovery of lov.' level contamination in the Sub-assembly 1 air handling system, the survey scope in this area was expanded to include all wall surfaces and the ceiling.
Wall grids were 1 meter (or less) on an edge, and ceiling grids were 2 meters (or less) on an edge.
(2)
The floor in sub-assembly 1 and the vault had been tiled since the use of licensed materials there.
Floor tile and mastic were removed before the floor surfaces were surveyed.
4.3.2.3 Survey of Penthouse and the Storage Building
(
Survey of these area was performed according to the steps outlined in 4.3.2.1, with the following exceptions:
l (1)
Because the walls were not painted, no paint chip samples were collected.
i l
(2)
The Sub-assembly 1 off-gas blower (which was located in the Penthouse) was contaminated with uranium.
This contamination was traced to a fire that occurred in this system in 1958 when it was attached to a uranium glove box.
The off-gas blower, motor and mount were packaged and disposed of as radioactive waste.
Because of the contamination found on the blower, all nearby room surfaces were checked for direct and recoverable contamination.
Contamination was found on overhead surfaces immediately above the blower location.
All horizontal overhead surfaces (beams, pipe, conduit, etc.) were surveyed in all directions from 4-6
1 l
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE this location until the perimeter of the contaminated region was identified.
This region was then decontaminated as described in Section 3.0 and given a 100% direct alpha and beta resurvey.
Smearable alpha and beta levels were also remeasured after decontamination.
Random direct and removable alpha and beta surveys were also performed in the Penthouse overhead outside of the contamination perimeter to confirm that no additional decontamination was needed.
Survey maps and data sheets were used to document the survey results.
4.3.2.4 Survey of Halls and Offices The major steps in the survey of these surfaces (all indoor areas besides Old HP Office, counting room, Sub-assembly 1 and Vault, Penthouse, and Bay 1) were identical to the steps described in 4.3.2.1, with two exceptions:
(1)
Because of the lower likeliho.1 of contamination in non-use areas, larger grid sizes (up to 3 m on an edge) were used.
(2)
Walls were not surveyed.
4.3.2.5 Survey of Bay 1 The major steps in the Survey of Bay 1 were identical to those described in 4.3.2.4 with two exceptions:
(1)
Because of spotty contamination on the basement floor (even though levels were below release limits) 100% of the basement floor was surveyed.
Results were documented on survey maps and. data sheets.
(2)
The basement floor sump was cleaned and given a 100% direct alpha and direct beta survey.
This included dismantling, cleaning, and surveying the basement sump pump.
Results were documented on survey maps and data sheets.
4.3.2.6 Survey of Ventilation Ductwork All ventilation ductwork was surveyed at each inlet and outlet.
The interior of all air handling units was also surveyed.
Removable alpha and beta surveys were performed at each access point.
Direct alpha and beta surveys were also performed at locations where sufficiently large access openings existed.
These surveys included checks of all roof vents and exhausts.
Survey locations were sketched on a survey map.
Survey results were recorded on l
data sheets.
4-7
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 4.3.2.7 Drain Lines The interior drains formerly used for transferring radioactive or potentially radioactive liquids were iron or steel.
Smear surveys showed that some of these drains were contaminated with low levels of highly enriched uranium.
This material was from the operation in Sub-assembly 1 involving large quantities of highly enriched uranium in the form of uranium dioxide powder.
This material was not handled or processed in the form of solutions.
The former hot drain system in shown in Figure 3-1.
All hot drainlines were surveyed by pulling a tight fitting, absorbent cloth through the entire length of the drainline.
The cloth was surveyed with calibrated PAC-4G alpha and beta meters.
If any contamination was found, the entire length of drainline was decontaminated as described in Section 3.0 and resurveyed as described above.
This was repeated, if necessary, until the cloth was visibly clean and no alpha or beta activity could be detected on it.
Additional 100 cm2 smears (minimum of three) were then taken at each access point.
These smears were counted for alpha and beta activity on a calibrated gas flow proportional smear counter.
Survey maps and data sheets were used to document survey location and results.
Designated cold drains that, by virtue of their location, might inadvertently have been used for disposal of licensed material into the sanitary or storm drain systems were also checked for contamination with the large area smear method.
The cold drain lines checked were in the former use areas, and are illustrated in Figure 4-2.
Three cold drain lines not shown in Figure 4-2 were also checked; the Sub-assembly 1 air handling system condensate drain, the Penthouse floor drain, and the storage building floor drain.
The drains serving the Sub-assembly air handling system and the Penthouse floor were checked because of traces of contamination found in the air handling system ductwork and the Penthouse overhead.
The storage building floor drain was surveyed as part of the storage building survey program.
The only designated cold drain that showed evidence of contaminaticn was the storage building drain, which was decontaminated as described in Section 3.0 and resurveyed with the small area smear method described above for the hot drains.
4.3.2,8 Survey of Outside Walls and Roof This survey stratum includes the walls outside Bay 1, Sub-assembly 1, and the counting room (up to 3 m above walking surfaces), the Bay 1 roof, the Penthouse roof, and the roof above the other areas depicted in Figure 2-4.
These surfaces were surveyed as described in Section 4.3.2.1, i
4-8
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE except as follows:
(1)
Grids were up to 3 m on an edge, although 1 m2 grids l
were used on the roof in the immediate vicinity of all air handling system exhausts and vents.
(2)
Paint chip samples were not collected on the outside wall grids.
These grids were surveyed before the walls were sandblasted and painted in the summer of 1985.
4.3.3 Additional Gamma Surveys Gamma surveys were performed in addition to those described in Section 4.3.2 outside the building using calibrated RSS-111 and PRM-7 meters.
The contiguous building grounds were divided into grids and surveyed.
These surveys were performed to ensure that all areas met the gamma release limit specified in Table 4.1, and to provide a baseline of background gamma radiation levels.
These surveys were documented on survey maps and data sheets.
Figure 4-3 shows i
the location of the surveys done on the outside of the building.
4.3.4 Soil Surveys Soil surveys were performed in two areas:
(1)
Behind the storage building at the terminus of the contaminated floor drain.
(2)
At the former termini of the Building A storm drain shown in Figure 3-1.
Before the radioactive liquid waste holding tank became available in 1958, the Building A drains were configured in such a way that operational error could have directed contaminated effluent from the Sub-assembly hot drains into the Building A storm drain line, although there is no evidence or record that this actually happened.
The storm drain configuration shown in Figure 3-1 is as the storm drain now exists; it has been extended twice during different construction operations at LRC involving soil grade changes in the drainage basin.
Using construction drawings and photographic records of the drain line extension operations, the former terminal locations were found, and soil in the vicinity was surveyed for contamination using the gamma spectroscopy system described in Section 4.2.3.
Four separate types of soil surveys were foreseen.
One would be to determine the extent of 4-9
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE contamination (core samples).
Another would be for excavated soil placed in drums (drummed soil sample).
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 procedures were used for each type, but sampling methods were different.
Since a large number of samples was expected, gamma analyses were planned based upon the known contaminants:
highly enriched uranium and, possibly, thorium.
A sampling method was planned for excavated soil that would 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.
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.
4.3.4.1 Drummed Soil Technical Procedure LRC-TP-206 describes techniques for taking samples of drummed soil.
These are all commonly used sampling techniques.
(8)
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 3 to 4 liter sample.
The multiple samples are obtained to create a composite sample representative of the drum's contents.
(2)
A 3 to 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 3 to 4 liter sample from a filled drum standing upright.
4-10
i FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 4.3.4.2 Ditch Face Survey Technical Procedure LRC-TP-197 describes two techniques for collecting soil samples in excavated areas.
(1)
A 3 to 4 liter sample can be scooped from the bottom of a trench (no longer than 20 feet) from which a drainpipe has just been removed to create a sample representative of the trench.
(2)
A 3 to 4 liter sample can be scooped from the surface of a trench to create a sample representative of about 10 square feet.
4.3.4.3 Core Samples Technical Procedure LRC-TP-207 describes the method for taking exploratory cores to guide further excavation efforts.
A core sampler is used that collects approximately two liters of sample per foot of depth.
4.3.4.4 Background soil core Samples Technical Procedure LRC-TP-207 also describes the method of taking background soil cores.
4-11
8 TABLE 4-1.
ACCEPTABLE SURFACE CONTAMINATION LEVELS Huclides" Average,c,f Maximum,d,f Removable,e,f b
b b
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, 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
Beta-gamma emitters (nuclides with decay modes other than alpha emission or spontaneous u
1 fission) except Sr-90 and others noted above.
5,000 dpm sy/100 cm 15,000 dpm sy/100 cm 1,000 dpm sy/100 cm 2
2 2
a Where surface contamination by both alpha-and beta-gamma emitting nuclides exlsts, 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.
j 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 shculd be determined by wiping 2
that area with dry filter or soft absorbent paper, applying moderate pressure, and assessing the amount of radioactive material en 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 I cm and 1.0 mrad /hr at I cm, respectively, measured through not more than 7 milligrams per square centimeter of total absorber.
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 4-2 SOIL RELEASE LIMITS AND EXTERNAL GAMMA EXPOSURE LIMIT
Th-228) with daughters present and in equilibrium 10 pCi/g soil **
Enriched Uranium Soluble or insoluble 30 pCi/g soil **
External Gamma Exposure Rate 5 nR/hr @l meter These limits are above background levels.
- These values are taken from Reference 9.
4-13
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 4-3 LRC TECHNICAL PROCEDURES USED FOR 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-197 BUILDING C/A SOIL SAMPLING PROCEDURE LRC-TP-206 PLUTONIUM DECONTAMINATION PROJECT DRUM SAMPLING PROCEDURE LRC-TP-207 BUILDING C/A 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 SPECTROMETRY SYSTEM LRC-TP-220 GAMMA-RAY SPECTROMETRY SYSTEM - COUNT REPRODUCIBILITY CONTROL CHART PREPARATION LRC-TP-221 GAMMA-RAY SPECTROMETRY SYSTEM - ENERGY CALIBRATION AND PERIODIC CHECKS OF ACTIVITY AND ENERGY CALIBRATION i
LRC-TP-222 GAMMA-RAY SPECTRGMETRY SYSTEM - BACKGROUND CHECKS LRC-TP-237 PREPARATION OF WASTE SHIPMENTS TO THE U. S.
ECOLOGY SITE IN WASHINGTON j
LRC-TP-239 EQUIPMENT SURVEY PROCEDURE - BUILDING A LRC-TP-267 PREPARATION OF SOIL STANDARDS LRC-TP-269 SURVEY OF BUILDING A DRAINLINES FOR REMOVEABLE CONTAMINATION LRC-TP-271 STANDARDIZATION OF BECKMAN WIDE BETA COUNTING SYSTEM l
4-14 1
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE LRC TECHNICAL PROCEDURES LRC-TP-275 ANALYSIS OF SELECTED RADIONUCLIDES IN PAINT CHIP SAMPLES BY GAMMA-RAY SPECTROSCOPY LRC-TP-276 USE OF PRM-7 MICRO-R METER LRC-TP-278 SURVEY OF BUILDING A SURFACES FOR UNRESTRICTED RELEASE LRC-TP-282 USE OF RSS-111 AREA MONITOR LRC-TP-283 COLLECTION OF POTENTIALLY CONTAMINATED PAINT SAMPLES FROM BUILDING A SURFACES e
4-15
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12
,\\d 4-18 13
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 5.0 AREA SURVEY RESULTS The data for the Release Project surveys and sample analyses are presented below.
All data are contained in the Building A (SNM-778) files.
5.1 Surface Surveys 5.1.1 Initial Surface Surveys After each laboratory (or former use area) was prepared for survey as described in Section 3.0, an initial survey was performed to determine direct and smearable alpha and Offices and other beta radiation levels on the room's surfaces.
clean areas were surveyed on floors without removing paint and floor tile.
Tables 5-1 through 5-4 provide summaries of these initial surface survey results.
Area names used in the tables of this section correspond to the descriptions given in Section 4.3.2.
Where significant alpha contamination was found in Building A, media or smear samples were collected for isotopic l
These samples included Bay 1 sump sludge, Penthouse analysis.
roof gravel, Bay 1 basement floor debris, and a swipe from the Penthouse overhead.
In each case, the contaminant was found to be uranium, not thorium.
This is consistent with the Building's history (use of uranium oxide powder in Sub-assembly 1, occurrence of fire in Sub-assembly 1 off-gas system that contaminated Penthouse overhead).
Where contamination was isotopically identified, the appropriate release criteria (in this case, uranium) was applied. In other building areas where no direct evidence regarding identification of contaminants was i
available or where thorium was found (storage building drain),the The alpha more conservative thorium release limits were applied.
survey data presented in Tables 5-1, 5-2, 5-9 and 5-10 should be evaluated with this point in mind.
The lower limit of detection for the direct alpha l
survey was 25 dpm/100 cm2 for the large area probe and 200 dpm/100 for the small area probe.
As Table 5-1 shows, 1287 of the cm2 i
1309 grids or 98.3% were at this level and the other 22 grids orThe 1.5% were below or met the release limit of 5000 dpm/100 cm2 highest readings were associated with the Sub-assembly 1 Using the ALARA concept, additional ventilation system.
decontamination was performed on those grids that were above the l
lower limit of detection.
Table 5-2 summarizes the 6,746 direct alpha readings About that were obtained during the initial surface survey.
97.7% or 6,594 of these readings were at the lower limit of detection and another 137 or about 2% were below the release j
limits.
I The background level of radiation for the direct beta 1
5-1
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE survey was 1200 to 1600 dpm/100 cm2 The values given in Tables 1
5-3 and 5-4, as well as Tables 5-12 and 5-13, have been corrected i
for the background radiation level.
The lower limit of detection for the beta survey meters was about 400 dpm/100 cm2 As Table 5-3 shows, 1165 of the 1309 grids or 89.0% were below this limit of detection and 141 grids or 10.8% were below the release limit of 5000 dpm/100 cm2 The highest readings were associated with the ventilation system.
Using the ALARA concept, additional decontamination was performed on those grids that were above the lower limit of detection.
Table 5-4 summarizes the 6,745 direct beta readings that were obtained during the initial surface survey.
More than 90.3% or 6,092 of these readings were below the lower limit of detection and the remaining 653 or about 9.7% were below the release limit of 15,000 dpm/100 cm2, No smearable alpha radioactivity above 30 dpm/100 cm2 was detected.
The background reading for the smear counter was 0.3 dpm/100 cm2 As shown in Table 5-5, 1,374 of the 1,906 smears or 72% were at this level.
No reading was above the a
release limit of 1000 dpm/100 cm2 The values of Tables 5-5 and 5-6 have been corrected for smear counter background.
No smearable beta radioactivity above 30 dpm/100 cm2 was detected.
The background reading for the smear counter was 2 dpm/100 cm2 As shown in Table 5-6, 1,267 of the 1,906 smears or 66.5% were at this level.
Of the remainder, 616 or 32.3% were between background and 10 dpm/100 cm2 No reading was above the release limit of 1000 dpm/100 cm2, The background level of radiation for the GM meter was 20 to 60 cpm.
As Table 5-7 shows, all 1,305 of the grids were at the background level. Table 5-8 summarizes the 6,443 direct GM meter readings that were obtained during the surface survey.
All were at background.
5.1.2 Release Surface Surveys Decontamination was performed in those areas identified in the original alpha survey as being above the limit of detection.
Some areas were more difficult to decontaminate than others.
Scrubbing of the surface or removal of paint was adequate in most areas.
In the Bay 1 sump, a needle-descaler was needed to remove significant contamination from the concrete surface.
Tables 5-9 to 5-12 provide summaries of the final survey results.
Tables 5-9 and 5-10 give a summary of the final direct alpha surface survey data.
The data in Table 5-9 show that all grid blocks are well below the release criterion of an average value of 5000 dpm/100 cm2 (uranium) or 1000 dpm (thorium),
with no grid block exceeding an average of 500 dpm/100 cm2 The individual reading data are summarized in Table 5-10; there are 5-2
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE no single readings exceeding 500 dpm/100 cm2 Over 98% of the individual readings were at the lower limit of detection of 200 dpm/100 cm2, Tables 5-11 and 5-12 give a summary of the final direct beta surface survey data.
The data in Table 5-11 show that all grid blocks are below the release criterion of an average value of 5000 dpm/100 cm2 The individual reading data are summarized in Table 5-12, no single reading exceeds 5000 dpm/100 cm2 About 93% of the grid blocks and over 94% of the individual readings were at background.
5.1.3 Paint Chip Samples The primary contaminant of concern was uranium, although paint chips were also checked for Cs-137, co-60, and Th-232 activity.
These samples were collected upon the walls of Sub-assembly 1, counting room, and the Old HP Office.
Paint chip samples collected from the CX-10 control room walls were used to provide data for thorium and uranium background corrections.
Table 5-13 presents the data accumulated from the analysis of the paint chip samples.
5.2 Gamma Radiation Survey A survey was conducted in and around Building A to measure the ambient radiation levels.
Table 5-14 summarizes the gamma readings recorded on 988 grids using the PRM-7 and the RSS-lli gamma meters.
As noted in Table 5-14, the PRM-7 readings should be considered for information only, since its NaI detector does not measure true dose equivalence.
The RSS-lli, on the other hand, measures true dose equivalence fairly well for the gamma i
energy range of interest because it uses an ion chamber as sensor.
Table 5-14 provides the average and maximum readings for all of the Building A/SNM-778 areas.
These values are gross readings; i.e.,
no background has been subtracted.
The outdoor-grounds readings in Table 5-14 reflect readings taken outside the original Building A.
"Outside the original Building A" means those survey locations illustrated in Figure 4-3 that are south l.
of the line separating the original building from its first addition.
The gamma background for indoor areas was estimated from the average of the office measurements; this value is 10.5 4R/hr.
As can be seen in Table 5-14, none of the indoor readings was more than 5 nR/hr above this level.
In fact, Sub-assembly 1, Bay 1, and the Penthouse are several uR/hr below this level.
This is attributed to the thick concrete walls around these rooms that shield them from shy-shine from the Building J Annex (see Reference 11).
Although the outdoor gamma readings are expected to be 5-3
w FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE somewhat higher than the indoor readings because of the enhanced background from the waste storage area, none of the outdoor readings is more than 5 4R/hr above the background level established for indoor areas.
It is concluded from this data that no residual contamination or activation remains in Building A that produces a radiation field of 5 4R/hr or more 9 1 meter from any surface.
5.3 Soil Surveys Samples were taken of soil excavated from behind the storage building near Building A (drummed soil samples), and samples were taken from the face of this excavation (ditch face soil samples).
Samples of soil were also taken at two locations where the Building A storm drain formerly terminated (core soil samples).
Finally, samples of site background soil were taken (background soil samples).
The data are presented in Tables 5-15 through 5-17 for the ditch samples and background samples.
The core samples were at background, and they are not tabulated.
The single drum sample indicated that the excavated material was contaminated slightly above release limits, and this drum has been readied for disposal at a' commercial LLW disposal facility.
l These data are discussed below.
5.3.1 Background Soil Survey i
Core samples were taken at each foot of depth from 31 holes 2 feet deep to provide 62 samples of background soil.
These samples were analyzed for Co-60, Cs-137, Thorium (calculated from Pb-212), and Uranium (calculated from U-235).
The results for all 62 samples are summarized in Table 5-15.
The results for Co-60 and Cs-137 represent the lower limits of detection for gamma analyses (or low level cave background).
No Co-60 or Cs-137 activity was found in the background soil j
samples.
The acceptance limits for background are presented in Table 5-16.
Soil samples with activity concentrations above I
these acceptance limits were considered to contain extraneous contamination, i
5.3.2 Ditch Face Release Survey The data are summarized in Table 5-17 for the ditch face survey.
The results for Co-60 and Cc-137 represent experimental background.
The analyses for uranium reflect corrections for background. The activity above background is a small fraction of the release limits. The calculation of the unity factor was performed with only the U-235 and Cs-137 values.
i 5-4 i
w FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-1
SUMMARY
OF ORIGINAL DIRECT ALPHA SURVEY RESULTS (Grid Averages)
Location Direct Alpha Survey Results Total Number Number of Grids of Grids
<200 200-1000 1000-5000 >5000 (grid average dpm/100 cm2)
Bay 1 117 1
118 Sub-assembly 1 361 361 Counting Room 117 117 4
Old H.P. Office 66 66 Penthouse 234 4
1 1
240 Ventilation Ductwork 14 6
6 1
27 Offices 62 62 Outside(Roof & Walls) 257 2
259 Storage Building 59 59 Total 1287 13 7
2 1309 5-5
.,-,.,y
u FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-2
SUMMARY
OF ORIGINAL DIRECT ALPHA SURVEY RESULTS (Individual PAC-4G Readings)
Location Direct Alpha Survey Results Total Number Number of Readings of Readings
<200 200-1000 1000-5000 >5000 (maximum dpm/100 cm )
a Bay 1 695 3
698 Sub-assembly 1 1805 1805 Counting Room 489 489 Old H.P. Office 289 289 Penthouse 1177 41 24 5
1247 Ventilation Ductwork 199 24 32 10 265 Offices 310 310 Outside(Roof & Walls)1224 10 1234 Storage Building 406 3
409 Total 6594 81 56 15 6746 l
l 5-6
O.
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-3
SUMMARY
OF AVERAGE ORIGINAL DIRECT BETA SURVEY RESULTS (Grid Averages)
Location Direct Beta Survey Results Total Number Number of Grids of Grids
<400 400-1000 1000-5000 >5000 (net grid average dpm/100 cm2)*
Bay 1 106 12 118 Sub-assembly 1 361 361 Counting Room 117 117 Old H.P. Office 65 1
66 Penthouse 236 3
1 240 Ventilation Ductwork 17 2
6 2
27 offices 62 62 Outside(Roof & Walls) 144 113 2
259 Storage Building 57 2
59 Total 1165 133 8
3 1309
- All readings are corrected for background activities.
)
5-7
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE l
TABLE 5-4
SUMMARY
OF ORIGINAL DIRECT BETA SURVEY RESULTS (Individual PAC-4G Readings)
Location Direct Beta Survey Results Total Number Number of Readings of Readings
<400 400-1000 1000-5000 >5000 (net maximum dpm/100 cm2)*
Bay 1 542 33 5
1 581 Sub-assembly 1 1805 1805 Counting Room 542 542 Old H.P. Office 290 3
293 Penthouse 1209 25 6
3 1243 Ventilation Ductwork 200 35 18 12 265 Offices 310 310 Outside(Roof & Walls) 807 449 29 1285 Storage Building 387 29 5
421 Total 6092 574 63 16 6745
- All readings are corrected for background activities.
5-8
FINAL SURVEY REPORT FOR THE RILbASE OF BUILDING A FROM THE SNM-778 LICENSE e
TABLE 5-5
SUMMARY
OF ALPHA SMEAR SURVEY RESULTS Location Alpha Smear Survey Results Total Number of Smears Number of Smears
<1 1-10 10-30
- (dpm/100 cm )
T Bay 1 109 18 127 Sub-assembly 1 374 73 447 Counting Room 146 76 222 Old H.P. Office 60 19 79 Penthouse 246 99 4
349 Ventilation Ductwork 187 140 4
331 Offices 52 8
60 Drainlines 23 5
1 29 Outside(Roof & Walls) 129 71 3
203 Storage Building 47 12 59 Total 1374 520 12 1906 l
5-9
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-6
SUMMARY
OF BETA SMEAR SURVEY RESULTS Location Beta Smear Survey Results Total Number of Smears Number of Smears
<2 2-10 10-30 Tnet dpm/100 cm2)
Bay 1 71 56 127 Sub-assembly 1 326 113 8
447 Counting Room 152 69 1
222 Old H.P. Office 56 21 2
79 Penthouse 237 109 3
349 Ventilation Ductwork 203 124 4
331 offices 44 16 60 Drainlines 23 6
29 Outside(Roof & Walls) 129 70 4
203 Storage Building 26 32 1
59 Total 1267 616 23 1906 5-10
e FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE s
TABLE 5-7
SUMMARY
OF FINAL GM METER SURVEY RESULTS s
(Grid Averages)
Location GM Meter Survey Results Total Number Number of Grids of Grids
<60 60-200
>200 (grid average cpm)
Bay 1 125 125 Sub-assembly 1 361 361 Counting Room 129 129 Old H.P. Office.
65 65 Penthouse 233 233 offices 62 62 Outside(Roof & Walls) 271 271
. Storage Building 59 59 Total 1305 1305 l
5-11
~
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-8
SUMMARY
OF FINAL GM METER SURVEY RESULTS (Individual GM Meter Readings)
Location GM Meter Survey Results Total Number Number of Readings of Readings
<60
<60-200
>200 (maximum cpm)
Bay 1 661 661 Sub-assembly 1 1805 1805 Counting Room 602 602 Old H.P. Office 309 309 Penthouse 1119 1119 offices 310 310 Outside(Roof & Walls) 1342 1342 Storage Building 295 295 Total 6443 6443 i
5-12
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A N
FROM THE SNM-778 LICENSE TABLE 5-9
SUMMARY
OF FINAL DIRECT ALPHA SURVEY RESULTS (Grid Averages)
Location Direct Alpha Survey Results Total Number Number of Grids of Grids
<200 200-500
>500 (grid average dpm/100 cm2)
Bay 1 118 118 Sub-assembly 1 361 361 Counting Room 81 81 Old H.P. Office 66 66 Penthouse 239 1
240 Ventilation Ductwork 23 23 offices 62 62 Outside(Roof & Walls) 259 259 Storage Building 59 59 Total 1268 1
0 1269 5-13
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A g
FROM THE SNM-778 LICENSE TABLE 5-10
SUMMARY
OF FINAL DIRECT ALPHA SURVEY RESULTS (Individual PAC-4G Readings)
Location Direct Alpha Survey Results Total Number Number of Readings of Readings
<200 200-500
>S00 (maximum dpm/100 cm2)
Bay 1 859 859 Sub-assembly 1 1805 1805 Counting Room 318 318 Old H.P. Office 289 289 Penthouse 1231 126 1357 Ventilation Ductwork 296 296 Offices 310 310 Outside(Roof & Walls)1234 1234 Storage Building 351 351 Total 6693 126 0
6819 l
l 5-14
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-11
SUMMARY
OF FINAL DIRECT BETA SURVEY RESULTS (Grid Averages)
Location Direct Beta Survey Results Total Number Number of Grids of Grids
<400 400-1000 1000-1500 >1500 (net grid average dpm/100 cm )*
a Bay 1 113 5
118 Sub-assembly 1 361 361 Counting Room 81 81 Old H.P. Office 65 1
66 4
Penthouse 239 1
240 Ventilation Ductwork 23 23 Offices 62 62 Outside(Roof & Walls) 173 86 259 Storage Building 59 59 Total 1176 93 0
1269
- All readings are corrected for background activities.
5-15
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-12
SUMMARY
OF FINAL DIRECT BETA SURVEY RESULTS (Individual PAC-4G Readings)
Location Direct Beta Survey Results Total Number Number of Readings of Readings
<400 400-1000 1000-1500 >1500 (net maximum dpm/100 cm2)*
Bay 1 582 21 1
605 Sub-assembly 1 1805 1805 Counting Room 373 373 Old H.P. Office 290 3
293 Penthouse 1340 1
1341 Ventilation Ductwork 295 1
167 Offices 310 310 Outside(Roof & Walls) 942 340 4
1286 Storage Building 365 1
366 Total 6302 367 5
0 6674
- All readings are corrected for background activities.
5-16
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A 3
FROM THE SNM-778 LICENSE TABLE 5-13
SUMMARY
OF PAINT CHIP GAMMA ANALYSIS RESULTS Locations Gamma Analysis Results*
Total Number Number of Grids of Grids BKG 100-500 500-5000
>5000 Sub-assembly 1 Counting Room, 149 13 8
1 171 and Old H.P.
Office
e Except for one sample which showed a slightly higher than background reading for Pb-212, the presence of Pb-212, Co-60 or Cs-137 could either be attributed to instrument background or the lower limit of detection.
B 5-17
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A 3
FROM THE SNM-778 LICENSE TABLE 5-14
SUMMARY
OF FINAL GAMMA SURVEY RESULTS Location Instrument Readings
- Number
<----PRM-7--->
<---RSS-111- ->
of Grids AVE MAX AVE MAX (nR/hr)
Bay 1 3.9 4.5 5.7 6.6 108 Sub-assembly 1 5.3 6.0 7.4 8.3 100 Counting Room 5.5 6.0 7.7 8.1 45 Old H.P. Office 8.4
.10.5 10.2 12.1 39 i
Penthouse 4.5 5.5 7.0 8.1 166 Offices 9.7 10.0 10.5 13.3 62 Drainlines 5.1 7.0 14 Outside (Roof, Walls & Yard) 17.8 26.0 10.4 14.5 419 Storage Building 11.0 11.0 10.3 11.4 35 Average 10.9 8.9 Maximum 26.0 14.5 Total 988
- PRM-7 does not m'easure true dose equivalence over all energy ranges.
These data are provided for information only.
5-18
_ _ ~ _ _ - _ _ _ _ _ _ _ _ _ _.
FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A
.g FROM THE SNM-778 LICENSE TABLE 5-15 ANALYSES OF BACKGEOUND SOIL SAMPLES Number of Activity, pCi/ gram Samples Co-60*
Cs-137*
Max AS Max A_vS Max 62**
0.08 0.30 0.10 0.47 1.45 2.12 5.06 8.55 Some of the values represented for co-60 and Cs-137 are minimum detectable levels; i.
e.,
they do not necessarily indicate the presence of cobalt or cesium in the soil, but indicate an upper limit for the values if they were present.
- Of the 62 samples, 31 represent one foot and 31 represent two e
foot samples from 31 locations.
TABLE 5-16 ACCEPTANCE LIMITS FOR THE BACKGROUND SOIL ACTIVITIES
" Acceptance limit" means the value at which it is concluded that the lostope is present above background levels.
This limit was calculated as described in references 7 and 11.
5-19
.c FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE TABLE 5-17 ANALYSES OF DITCH FACE SOIL SAMPLES Number of Activity, pCi/ gram Unity Samples Co-60*
Cs-137*
- Factor Ayvg Max Avg Max Avg Max A_v_g Max Am Max v
20**
0.09 0.17 0.16 0.39 1.48 1.76 0.62 2.51 0.06 0.16 Uranium values are corrected'for the background contribution.
- Some of the values represented for Co 60 and Cs-137 in this category are minimum detectable concentrations; i.
e.,
they do not necessarily indicate the presence of cobalt or cesium, but indicate an upper limit for the values if they were present.
l l
r l
l 5-20
c FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 6.0 SURVEY INTERPRETATION The LRC considers that the survey results summarized in Section 5.0 accurately represent the radiological condition of Building A and demonstrate that the facility has been sufficiently decontaminated to meet the NRC criteria for unrestricted release.
The conclusion that these survey data adequately represents the facility's radiological condition rests on the choice of survey strata and the extent of survey performed in each one.
For those surfaces that were given a 100% survey (Bay 1 basement floor, a portion of Penthouse overhead, ditch behind storage building, Sub-assembly air handling system ductwork), the conclusion of releasability is unequivocal; the survey data clearly demonstrates that the NRC release criteria have been met or surpassed.
The survey results of these surfaces will not be further discussed in this section.
However, other portions of the facility were given random, systematic surveys, and the interpretation of these results is discussed in the following paragraphs.
6.1 Floors, Walls and Roof Floors in the facility were randomly surveyed as described in Section 4.0.
In some areas the floor stratum was extended to include walls up to 2 meters above the horizontal walking surfaces.
The outside walls and roof were given a similar random survey.
These random surveys were systematically performed to ensure that each surface was given a representative survey.
Each of the individual surveys was reviewed and found to be well below release limits.
The next step was to determine what statistical inference could be made about the releasability of each stratum; i.e., how confident can one be that the unsurveyed portions of each stratum are below release limits?
This was done by using equation 6.1.
This equation correlates the minimum sample size, n (with the condition that no rejectionable contamination is found) needed to provide the confidence level r that there are no more than K rejectionables in a total population N :
n=[1-(1-r)^(1/K)][N-(k-1)/2]
6.1 The total population (N) was obtained by dividing the total surface area of each stratum by the sample area.
The direct a and p surveys were performed with probes whose sensitive area was 50 cm2; therefore, N(direct)=N(50)=(Total Stratum Area, cm2)/50 cm2 Many a surveys were performed with a probe whose sensitive area was 445 cm2; in these cases, 6-1 4
c FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE N(direct)=N(445)=(Total Stratum Area, cm2/445 cm2 The removable surveys were performed by collecting 100 cm2 smears.
Therefore, N(removable)=N(100)
=(Total Stratum Area, cm2)/100 cm2 Three floor / wall / roof strata were surveyed.
These are:
(1)
Floors and walls in former use/ storage areas (storage building, Sub-assembly 1, Vault, Old HP office, Counting Room, and Penthouse).
(2)
Indoor Horizontal walking surfaces (Besides 6 areas listed above).
(3)
Roof and outside walls.
The survey results and minimum survey sample sizes for these strata are summarized in, Tables 6.1, 6.2, and 6.3.
Table 6.1 Floors / Walls-Storage Bldg.,SA 1, Vault, Old HP, CR, Penthouse (including SA-1 and Vault ceiling)
No. of **
No. of **
Direct Direct No. of **
Stratum Original Original Small~
Minimum
- Sample Area Alpha Beta Area size m2 Surveys Surveys Smears 1944 4145 4212 1042 90 Table 6.2 Other Indoor Horizontal Walking Surfaces (including upper floor Bay 1) 1 No. of **
No. of **
Direct Direct No. of **
Minimum
- Stratum Original Original Small~ ****
Sample Area Alpha Beta Area Size m2 Surveys Surveys Smears 382 370 370 72 90 l
6-2 f
-,-,---,--..,-.n-_---
, _., - - -,., _ _. - - -, -. - - - ~ -., - -. -,. _, -.,,. -...,,, -.,. _ -, - -
,_-..-.-.,,.,-.,n-,
-e,
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE Table 6.3 Roof and Outside Walls No. of **
No. of **
Direct Direct No. of
- Minimum
- Stratum Original Original Small- ***
Sample Area Alpha Beta Area Size ma Surveys Surveys Smears 775 1234 1285 203 90 Minimum sample size is defined as the minimum number of surveys needed to provide 99% confidence that less than 5% of unsurveyed portions of stratum exceed release limits, with the condition that all samples be below release limits.
Total population size =N(50),
T =0.99 and K=0.05*N.
Each survey point was below release limits.
Does not include outside walls; no small area smears were collected on outside walls. 100%
of each outside wall grid was given a large area smear, which was surveyed for a and S contamination.
No activity above background was found.
- Direct surveys were all below removable limits, so sample population for removable surveys was well above minimum sample size.
The results in Tables 6.1, 6.2, and 6.3 show that the surveys of the reference strata were sufficiently thorough to provide reasonable assurance that those surfaces meet or surpass NRC release criteria for residual contamination.
6.2 Paint Chip Samples No significant Cs-137, Co-60, or Th-232 activity was found in the paint chips.
Therefore only uranium activity was considered in evaluating whether the paint chip analysis indicated that nonreleasable levels of activity were beneath the painted surfaces.
In evaluating the paint chip data relative to the appropriate release limits (15,000 dpm/100 cm2 for any 100 cm2, and 5,000 dpm/100 cm2 averaged over 1 m2), two types of distribution were considered: discrete and continuous.
A discrete distribution is appropriate if we could consider the U-235 readings as acceptable or not acceptable; that is, 6-3
eh FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE readings under the maximum allowable limit are acceptable and readings above the maximum allowable limit are not acceptable.
All of the readings in the test areas (Old HP, CR, SA-1 and Vault) are below the maximum allowable limit.
However, the sample size is somewhat limited, resulting in a high percentage of the area, at specified probabilities, exceeding the maximum allowable limits.
Consequently, a number of continuous distributions were investigated to determine which is the most representative for the available data.
7 4
The log-log distribution was found to be an appropriate fit to the individual data sets.
To obtain the distribution each reading was transformed as follows:
y log [ log (10^10 X(i))].
The transformation provided a distribution that approximated a normal distribution that could be used in establishing limits.
On the basis of the log-log transformation, the limiting values for 99.99% of the distribution were determined.
This limiting value for the reference Building A surfaces is 5,020 dpm/100 cm2 Consequently, it is concluded that the probability of exceeding the maximum allowable level (15,000 dpm/100 cm2 for any 100 cm2) is less than 0.01%.
There are two ways of determining if the averages for square meters exceed the maximum allowable limit of 5,000 dpm/100 cm2 One method would be to take multiple readings for a number of square meters.
The average of the averages and the variability measure for the averages are calculated and used to establish the probability of exceeding the allowable limit.
However, this approach would require that a large number of additional samples (3-4 more samples for 10-20 grids) be collected and analyzed. Therefore, another approach was used.
l The second way of determining whether the probability that average readings for a square meter are within the acceptable limits is to assume that the square meter averages for each location are distributed similarly for the l
individual uranium readings.
This is not an unrealistic assumption, since the average of the individual readings is, in all likelihood, equal to the average of all the square meter averages.
And, by theory, the variability of the averages for a set of readings is less than the variability l
for the individual readings.
Following this premise and using the statistics derived for the individual values, the probability of any square meter having an average uranium contamination above the stated limit of 5,000 dpm/100 cm2 is 0.05%.
I 1
l l
6-4 i
FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE 6.3 Ventilation Systems and Other Surfaces Included in this general category are the HVAC systems (ductwork and air handling systems), former hot drainlines, Old HP overhead, source storage tubes, and so on.
The survey data for these surfaces was not taken as systematically as those for floors and walls.
This was usually because of problems with accessibility.
For example, the source storage tubes were too small for the surveyors to insert the PAC-4G probes for direct alpha and beta surveys.
Therefore, only removable alpha and beta surveys and direct GM meter surveys were performed; these were appropriate surveys considering the nature of contamination most likely to be found there (i.e., a source that became dislodged from its holder or removeable contamination from a leaky source).
The acceptability of such surfaces for radiological release must therefore be more heavily based on the appropriateness and reasonableness of the surveys performed than on statistical inferences.from survey results.
Surveys of the HVAC system at convenient access points showed no significant contamination, with the exception of the Sub-assembly 1 air handling system, which was completely dismantled and decontaminated.
Direct and removable measurements were made on vertical and horizontal surfaces, near bends, and inside air handling units.
These areas meet the requirements in Reg.
Guide 1.86 for the survey of such surfaces.
The lack of significant contamination at these representative areas provides strong evidence that these systems are radiologically clean.
The indoor hot drains were c1 caned as described in Section 3 and surveyed as described in Section 4.
Care was taken to clean the entire system (i.e., 100% of each drain) in the same way so that the surveyed surface could be considered typical of the surfaces that were inaccessible for survey.
Small area smears were then taken at both ends of each hot drain line branch. These smears were taken from vertical and horizontal pipe runs, and showed residual contamination far below release limits.
Again, the lack of
)
l significant contamination on these representative surfaces provides strong evidence that residual contamination throughout the system is acceptably low.
6.4 conclusions Selected facility surfaces and contiguous soil systems were systematically surveyed in accordance with an approved Project QA Plan and written technical procedures.
These surveys were performed with sufficient depth and scope to evaluate the facility's radiological condition with respect to all NRC release criteria for residual alpha and beta 6-5
.j FINAL SURVEY REPORT FOR RELEASE OF BUILDING A FROM THE SNM-778 LICENSE contamination on surfaces and in soil, and for gamma radiation levels throughout the facility.
Survey results were reviewed and, where appropriate, statistically analyzed.
These analyses showed that there was a high confidence that the subject areas were radiologically clean.
LRC concludes that the facility meets all of the NRC release criteria and that the reference facility can be released for unrestricted use.
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FINAL SURVEY REPORT FOR THE RELEASE OF BUILDING A FROM THE SNM-778 LICENSE
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 Building A Lynchburg Research Center", June 23, 1983.
3.
Building A Decommissioning Project Quality Assurance Plan, 85009L, Revision No. O, LRC Order No. 8665, October 7, 1985.
4.
" Termination of Operating Licenses for Nuclear Reactors", USAEC Regulatory Guide 1.86, June 1974.
5.
Docket No. 50-13, USAEC Construction Permit, No. CPCX-9, October 2, 1957.
6.
Memo, A.F. Olsen, B&W, to.The Division of Licensing,NRC,
" License Termination Survey Report for the CX-10 Critical Experiment Facility", June 2, 1986.
7.
NUREG/CR-2082, " Monitoring for Compliance with Decommissioning Termination Survey Criteria" with Appendices I through VII, June 1981.
8.
Arthur F. Taggart, " Handbook of Mineral Dressing, Ores and Industrial Minerals", John Wiley & Sons, Inc. 1927.
9.
" Disposal or Onsite Storage of Residual Thorium or Uranium from Past Operations", NRC SECY 81-576, October 5, 1981.
10.
Memo, N Soltys, B&W, to H.L. Beazley, B&W, " Site Background Levels", May 8, 1986.
11.
" Supplement No. 1 to License Termination Survey Report for the CX-10 Critical Experiment Facility",
RDD:87:8665-19:2, Babcock & Wilcox Co., June, 1986.
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