ML20137U231

Decontamination & Decommissioning of Bldg C - Phase I at Lynchburg Research Ctr

ML20137U231
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Site:	07000824
Issue date:	10/31/1985
From:	BABCOCK & WILCOX CO.
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ML20137U228	List: ML20137U224 ML20137U231
References
RDD:85:8604-01:, RDD:85:8604-1:, NUDOCS 8602190092
Download: ML20137U231 (46)

Text

b DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II AT LYNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA REPORT NUMBER:

RDD:85:8604-01:02 OCTOBER 1985 BABCOCK & WILCOX Lynchburg Research Center Lynchburg, Virginia 8602190092 851213 PDR ADOCK 07000824 C

PDR Ab

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 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 II 2-1 2.4' History of Operations in Phase II 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 3-2 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 Gamma Survey Design 4-3 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 Instruments used for Additional Gamma Survey 4-4 4.3.3 Soil Survey Instrument 4-4 4.4 Survey Procedures 4-5 4.4.1 Surface Surveys 4-5 4.4.2 Soil Surveys 4-6 I-1

' DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 5.0 PHASE II 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 Gamma Radiation Survey 5-3 5.2 Release Soil Survey 5-3 5.2.1 Background Soil Survey 5-3 5.2.2 Ditch Face Release Survey 5-4 5.2.3 Drummed Soil Survey 5-4 5.2.4 Soil Survey Data Analysis 5-5 6.0 SURVEY INTERPRETATION 6-1

7.0 REFERENCES

7.

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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II LIST OF TABLES 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 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 5-3 Summary of Original Alpha Smear Survey Results 5-8 5-4 Summary of Average Release Direct Alpha Survey Results 5-9 5-5 Summary of Maximum Release Direct Alpha Survey Results 5-10 5-6 Alpha Survey Results 5-11 5-7 Summary of Release Direct Beta and Gamma and Smearable Beta Survey Results for 123 Floor Grid Blocks in Phase II 5-11 t

5-8 Analyses of Background Soil Samples 5-11 5-9 Acceptance limits for the Background Soil Activities 5-12 5-10 Analyses of Ditch Face Soil Samples 5-12 5-11 Analyses of Drummed Soil Samples 5-12 5-12 Soil Samples Analysis Results 5-13 f

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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 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 II Hot Drain System 3-4 3-2 Phase II Excavation Locations 3-5 4-1 Typical Surface Grid Arrangement 4-11 5-1 Gamma Radiation Survey 5-15 I-4

ECONTAMINATION AND DECOMMISSIONING OF BUILDING,C - PHASE II

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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 activities with radioactive materials in Building C.

B&W, in ceasing licensed activities in Building C, is complying,Nith 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 pub'lic 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 contaminared soil from around and beneath buildings.

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A decommissioning plan for Building C was submitted to.the NRC for information purposes. (2)

Decommissioning means action taken that res'ults 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'th'e act of decontamination.

The decommissioning plan divided work into three phases with a different section of the building being decontaminated in each phase.

This report addresses the decontamination performed in Phase II.

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 of Building C and the underlying soil.

Table F-1 in Reference 1 establishes numerical limits for sbrface contamination within the facility.

Additional numerical limits for external exposure and soil remaining under Building C i

• are contained in Reference 4.

B&W used these limits as minimum goals to achieve during 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 so-quential phases as described in Reference 2.

1.3 Organiz6 tion of this Report This report contains seven sections that describe the decom-missioning work performed during Phase II of the Building C pro-1-1

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II ject.

Following this introductory section, a physical descrip-tion 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

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 2.0 IDENTIFICATION OF PREMISES 2.1 Site Description 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 tre site property boundary and the locations of the separate fac 'ities on the site.

The LRC is a highly integrated facility built to develop, test, and examine nuclear-eactor cores and to develop overall nuclear fuel cycles.

The location of Building C is shown in Figure 2-2 relative to the other buildings comprising the LRC 2.2 Building C Physical Description The existing structure known as Building C ir 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 construction with outside dimensions of 225 feet by 174 feet at its greatest width.

There is a small basement under one of the laboratories.

The building contains about 24,000 square feet of laboratory, office, and support space.

There were ap-proximately 10,250 square feet in the laboratories which had suitable bench-scale and pilot plant equipment, ventilation, and personnel protection equipment for the handling of radioactive materials.

There was sufficier.t 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 l

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 II Decontamination of Building C will be completed in three phases.

Phase I included laboratories on the western end of the building where projects were performed with thorium, plutonium, and uranium solutions and powders.

Phase II includes labora-tories 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 analyt-ical 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 Building C 2-1

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II are included in this decommis-sioning project.

Phase II includes former Laboratories 15, 16, and 17, the offices and hallway along the front of the building, and the offices on the other side of the hallway which back up to Lab-oratories 15 and 16.

Also included is the eastern portion of Hallway 23, the hallway connecting Hallway 23 to the front hall-way, but not the area that is the main entrance to the building.

The interior walls, ceilings, and floors as well as the under-lying soil are considered to be included in Phase II.

2.4 History of Operations in Phase II I

The original building was constructed in 1962 for bench-scale experiments converting thorium nitrate to thorium oxide.

Expansions of this building were added several times in the next few years.

A major building expansion was completed in 1968 to

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permit work on the FFTF Program.

This work was con-ducted in gloveboxes installed in Laboratories 15, 16, 17, 19, 20.

The FFTF program conducted in these laboratories included fuel prep-aration, pelletizing and rod loading.

Uranium fuel projects were initiated in laboratories that were vacated at the conclusion of the FFTF Program in 1971.

These projects included pelletizing uranium oxide, firing and grinding the pellets, and performing various tests on the fin-ished fuel.

A limited amount of beta-gamma contaminated mate-rial has been brought into the Phase II area.

Samples of beta-gamma materials were occasionally analyzed in Laboratory 19 and the waste was solidified and placed in waste drums for disposal rather than being poured into the Building C drain system.

Plutonium fuel projects were primarily conducted during 1968 to 1971, although two small projects were carried out for DOE dur-ing 1979 and 1980 in Laboratory 17.

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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 3.0 DECONTAMINATION OPERATIONS The Phase II area of Building C was used for a range of R&D projects with plutonium, and uranium powders.

The general pro-cedure for decontamination operations performed in Phase II con-sisted of (a) removing all SNM, equipment and supplies, (b) re-moving service and utility lines that would not be needed during decontamination, (c) decontaminating surfaces in the rooms, (d) removing drain lines, (e) excavating underlying soil, and (f) disposing of contaminated waste.

Surveying for radioactivity was conducted during and after decontamination.

A successfully decontaminated area was isolated from other areas still being decontaminated in order to prevent recontamination.

The decon-tamination operations were performed by skilled and unskilled laborers, lab technicians, and health physics technicians and professionals trained in approved decontamination procedures and surveying and analytical procedures.

The survey equipment and procedures are described in Section 4.0.

3.1 Preparation of Rooms for Decontamination All accountable SNM was removed from the Phase II area.

Equipment and supplies in each laboratory in Phase II were sur-voyed for contamination 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 or above per-missible 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 por-tions 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 con-tioning) ducts were removed if they would have interfered with the comprehensive survey of laboratory surfaces.

Paint and coat-ings were removed from these pipes and ducts.

Dismantled, clean-ed pipes were 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.

Filters, filter housings, and branch ducts in the box off-gas system serving Phase II were removed.

Filters and filter housings in the room off-gas system serving Phase II were re-moved.

The main ducting in Phase III, which serves Phase II, remains in place.

Paint and coatings were removed from the ducts and filter housings.

Cleaned duct and housings were surveyed for radioactivityiand released as clean scrap if the surface activity levels were below the limits specified in Table 4-1.

If'the sur-vey showed activity above these limits, the materials were dis-posed of as contaminated waste.

The box off-gas and room off-gas headers were surveyed in place.

(These headers are suspended 3-1

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II from the ceiling and did not interfere with the survey of room's surfaces.)

All filters were disposed of as contaminated waste.

3.3 Decontamination of Room Surfaces Paint, floor tile, and tile cement were removed from most walls, ceilings, and floors of the laoratories in the Phase II area.

Removal was necessary because the walls and ceilings had been repainted and new floor tile had been installed as labora-tories 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 intro-duction of licensed material into a room.

Paint was not removed from walls that had been erected after cessation of activities with SNM.

(These were primarily walls in the connecting hall.)

Paint was not removed from walls in rooms from which SNM had been excluded.

(SNM was not handled in the front offices and hall-way.)

Floor tile and tile cement were removed to expose the concrete floor surface.

Paint chips, floor tile and other wastes generated in the surface cleaning processes were placed in 55-gallon waste drums.

Samples were obtained from each drum for analysis by gamma spectroscopy.

These analyses were used to determine the disposal classification.

All drums that contain the decontamination waste have been shipped to an NRC

'acnsed disposal site.

Walls, ceilings, and floors were thoroughly sr.. eyed for alpha radioactivity (the ceilings of the offices were not sur-veyed.)

When contaminated areas.were found, walls were decon-taminated by removing portions of cinder block and floors were decontaminated by chipping up portions of the concrete floor.

These areas were resurveyed and the iterative process of chipping and surveying was continued until release limits were met.

These removed materials were disposed of as contaminated waste.

3.4 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 un-contaminated concrete rubble was disposed of as clean land fill.

1 The soil was removed from above each hot drain line and placed in 55-gallon drums.

Samples were obtained from each drum for anal-ysis by gamma spectroscopy.

These analyses were used to deter-mine the ultimate disposal of a drum's contents.

Drums that sat-isfy 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 sur-veyed.

If the surface activity was less than the limits 3-2

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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 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 contaminated waste.

All cold drain lines were surveyed for smearable alpha radioactivity.

All ccid drain lines that were contaminated were 4

decontaminated or disposed of as contaminated waste.

(Experience indicates that pulling a smear cloth through the line is a reli-able method to identify radioactivity.)

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 ex-ceeded these limits, further excavation was performed.

Soil re-moval 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 loca-tion of the excavations.

Excavated soil was placed in 55-gallon drums.

Samples were obtained from each drum for analysis by gamma spectroscopy.

These analyses were used to determine the ultimate disposal of a drum's contents.

Drums that satisfy the criteria shown in Table 4-2 are being retained at the LRC for unrestricted disposal after the verification survey has been com-pleted 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 II 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 applicable requirements as described in References 5, 6, and 7.

Uncontaminated paint chips, floor tile and cinder blocks were also placed in 55-gallon drums and are being shipped to a li-censed disposal facility in accordance with applicable require-ments as described in References 5, 6, and 7.

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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 4.0 SURVEY DESIGN AND PROCEDURES R&D projects performed in Phase II involved the use of plutonium, and uranium.

The isotopes of these elements are pri-marily alpha emitters, but many of their daughters are gamma emitters.

The survey plan was based upon inspecting surfaces primarily for alpha contamination and analyzing granular mate-rials (soil, paint chips, etc.) for gamma contamination.

Sam-pling was planned according to NUREG/CR-2082 (8) to assure that no area remained in Phase II 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 II surfaces were obtained from Table F-1 and Annex C of Reference 1.

These limits are reproduced in Table 4-1.

The limits for transuranics are the most restrictive in this table and were selected for application to Phase II.

These limits can be corrected for local naturally occurring thorium and uranium.

From previous background measure-ment experience within and around the 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 re-quired to achieve the release limits.

Therefore, the surface decontamination work for Phase II 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 II soil are provided in Reference 3 and are listed in Table 4-2.

These limits were applied to soil remaining under Building C and to excavated soil.

These limits can be corrected for the naturally occurring thorium and uranium.

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 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.

(It was recognized that additional release limits might be needed for Co-60, Cs-137, and U-233.

A decision was made to review soil sample analysis data for evidence of these 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 corrected 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 4-1

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 1

J would haveito be taken into account.

(The Hot Cells are lo-cated near the south-west corner of Building B and contain high-level beta-gamma materials.

Located toward the north-east behind l

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 applica-tion to this project.

4.2 Survey Design 4.2.1 Surface Survey Design Most of the laboratories in Phase II had been used for experiments with the elements of interest, i.e.,

plutonium and uranium.

Each Phase II laboratory had been cleaned and repainted more than once so there was a possibility that contamination ex-isted beneath the paint and floor tile.

Prudence dictated stripping walls, 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 and uranium had to be identified.

Materials that could interfere with a comprehensive survey for surface contamination had to be removed.

Paint *, floor tile, and tile cement had to be removed from these surfaces to expose the original surface.

(Paint did not need to be removed from walls that had been erected after cessation of activities with SNM or from walls in areas from which SNM had been excluded.)

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 to correspond with these 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 decontamination.

When the alpha sur-veys showed acceptable results, other types of surveys would be conducted.

Beta smears and direct beta and direct gamma surveys were planned for each of 123 randomly selected floor grid blocks in the Phase II 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 I

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 4.2.2 Gamma Survey Design Gamma radiation surveys were planned for each of the 123 randomly selected floor grid blocks in the Phase II area.

This represents 20% 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.

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 (drummed soil sample).

Another would be for soil sam-ples from the face of an excavation (ditch face sample).

A third would be to determine the extent of contamination identified by the ditch face samples (core samples).

The fourth would be to establish the concentrations of naturally radioactive isotopes in the site's soil (background samples).

The same analytical pro-cedure could be used for each type, but sampling methods would differ.

Since a large number of samples was expected, gamma analyses were planned based upon known daughters of plutonium, uranium and thorium.

A sampling method was planned for excavated soil that would obtain a uniform quantity of soil for analysis as each drum was filled.

(This 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 ditches that would result in a uniform quantity of soil for analysis from gridded areas of the excava-tion.

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.

l The only other pathway for contaminants to enter the soil under the building would be through the concrete floor.

This type of contamination would be found on and in the floor itself during surface surveys and could be tracked if it did appear.

(No evidence was found that contamination penetrated through the concrete into the soil.)

4.3 Survey Instruments The instruments used for survey and analysis in Phase II are standard models routinely used by the nuclear industry for this type of work.

The instruments were calibrated in accordance with applicable LRC Technical Procedures using National Bureau of Standards traceable sources.

4.3.1 Surface Survey Instruments Each surface survey instrument has a lower limit of detection for the radiation being measured.

This is the lowest 1

level of non-zero activity that it can register.

These limits are defined in the following sections.

4-3

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 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 cpm /50 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.

Calibration was performed according to Technical Procedure LRC-TP-51 using NBS traceable beta sources.

The lower limit of detection for the PAC-4G for beta detection was 300 cpm /50 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.

Calibration was done with NBS traceable alpha and beta sources as appropriate.

The background level for the smear counters was 0.1 dpm alpha / 100 sq. cm. and 300 dpm beta /100 sq.

cm.

4.3.1.4 Surface Gamma Survey Instrument A Geiger-Muller (GM) Survey Meter was used for the surface gamma survey.

Instrument calibration was performed according to LRC-TP-50.

The lower limit of detection for the GM meter was about 0.05 mR/hr.

4.3.2 Instruments used for Additional Gamma Survey The Geiger-Muller (GM) Survey Meter described above was used for the gamma surveys one meter abouve the floor surfaces.

A Model RSS-111 Reuter-Stokes Environmental Radiation Monitor was also used to measure gamma radiation one meter above the walking surfaces.

These measurements were taken both inside and outside Building C.

This monitor was calibrated by the manufacturer with NBS traceable sources.

The lower limit of detection for the RSS-111 was 1 nR/hr.

4.3.3 Soil Survey Instrument A Nuclear Data Corporation high-resolution gamma-ray 4-4

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II e

spectroscopy system using HPGe detectors was used to nondestruc-tively analyze soil samples..

This system is standardized according to Technical. Procedure LRC-TP-210.

This spectroscopy system was used to examine a gamma spectrum from about 50 kev to about 2 MeV.

Am-241, plutonium, thorium, and uranium concentrations were measured by analysis of gamma-ray energies within this range.

The Am-241 concentration was determined directly from it's 59.54 kev peak.

The plutonium concentration was calculated by multiplying the Am-241 concentra-

. tion by an experimetally determined factor.

(The Pu-239 concen-tration was directly measured at.375.02 and 413.69 kev in samples containing nCi/g quantities of Pu-239.

These values were com-pared 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 concen-tration.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 Surveys i

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 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.

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 4-5

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II the location and maximum gamma, direct gammma, and direct beta counts on a data sheet.

(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 con-tainer for analysis by gamma spectroscopy.

Soil standards were prepared using Technical Procedure LRC-TP-267.

Varying methods were used to obtain soil samples ac-cording 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 Drummed Soil Technical Procedure LRC-TP-206 describes three techniques for taking samples of drummed 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 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.

4.4.2.2 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 b'ottom of a trench (no longer than 20 feet) from which a drainline has just been removed to create a sample representative of the trench.

4-6

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II (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.

4.4.2.3 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 LRC-TP-207 also describes the method of taking background soil cores external to Building C.

4-7

TABLE 4-1.

ACCEPTABLE SURFACE CONTAMINATION LEVELS Nuclides Average,c,f Maximum,d,f Removable,e,f a

b b

b U-nat, U-235, U-238, and 2

2 2

associated decay products 5,000 dpm a/100 cm 15,000 dpm a/100 cm 1,000 dpm a/100 cm 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 Jo fission) except Sr-90 and 2

2 2

others noted above.

5,000 dpm 87/100 cm 15,000 dpm sy/100 cm 1,000 dpm By/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 I cm and 1.0 mrad /hr at I cm, respectively, measured through not more than 7 milligrams per square centimeter of total absorber.

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 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 ***

Natural Uranium (U-238 +

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 10 uR/hr

• These limits are above background levels.

• • The individual soil limits given in this table apply to each element if it exists by itself.

When they occur as a mixture, the sum of the ratios of the elemental concentrations versus their limits must be less than 1.

Thus, for Phase II, (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 II 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 SAMPLING PROCEDURE LRC-TP-206 PLUTONIUM DECONTAMINATION PROJECT DRUM SAMPLING PROCEDURE LRC-TP-207 BUILDING C SOIL CORE SAMPLING PROCEDURE LRC-TP-208 PREPARATION OF SOIL SAMPLES LRC-TP-210 ANALYSIS OF RADIONUCLIDES IN SOIL BY GAMMA RAY SPECTROSCOPY LRC-TP-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

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DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 5.0 PHASE II SURVEY RESULTS Building C was used primarily for R&D projects with thorium, plutonium, and uranium.

Since these are all alpha emitters and only limited information was available about specific usage in the laboratories, comprehensive surveys for direct and smearable alpha contamination were conducted on the surfaces of the Phase II area in Building C.

Only limited amounts of beta-gamma mate-rials had ever entered Building C, so beta-gamma surveys were conducted on a limited number of randomly selected floor grid blocks.

A survey was performed to establish gamma radiation lev-els due to sources external to Building C.

The data for these surveys and analyses are described below.

All data are contained in the Building C Decommissioning files.

5.1 Surface surveys 5.1.1 Initial Surface Surveys Each laboratory (or former use hrea) 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.

Offices and other clean areas were surveyed on floors and walls (not ceilings) without removing paint and floor tile.

Tables 5-1 through 5-3 provide summaries of these initial surface survey results.

The lower limit of detection for the direct alpha sur-vey was 30 dpm/100 sq. cm.

As Table 5-1 shows, 3,661 of the 3,688 grids or 99.3% were at this level and the other 27 grids or

.7% were below or met the release limit of 100 dpm/100 sq. cm.

About 75% of these 27 grids were on the floors with the other 25%

on the walls.

No contamination was found on the ceilings.

None of the grids exceeded the release limit for direct alpha radia-tion.

The highest reading was on the wall of one of the labora-tories. Using the ALARA concept, additional decontamination was performed on the 27 grids that were above the lower limit of detection.

Table 5-2 summarizes the 47,460 direct alpha readings that were obtained during the initial surface survey.

More than 99.8% or 47,384 of these readings were at the lower limit of detection and 75 or about.2% were below 300 dpm/100 sq. cm.

Only one reading or less than.1% was above 300 dpm/100 sq. cm.

with the highest reading being 600 dpm/100 sq. cm.

No smearable alpha radioactivity above 12 dpm/100 sq.

cm.

was detected.

The background reading for the smear counter was 0.1 dpm/?30 sq. cm.

As shown in Table 5-3, 3,231 of the 4,397 smears or 73% were at this level.

Of the remainder, 965 or 22% were between 0.1 and 5 dpm/100 sq.

cm. and the remaining 5%

or 201 readings were between 6 and 12 dpm/100 sq. cm.

5-1

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 5.1.2 Release Surface Surveys Decontamination was performed in those areas identified in the original alpha survey as being above the limit of detec-tion.

Some areas were more difficult to decontaminate than others.

Removal of 1/16 to 1/4 inch of the concrete surface was adequate in most areas.

Tables 5-4 and 5-5 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 50 dpm/100 sq.

cm.

About 78% of the grids averaging over 30 dpm/100 sq. cm.

were on the floor.

The data are summarized in Table 5-5 and have no single reading exceeding 65 dpm/100 sq. cm.

Over 99.3% of the grid blocks and over 99.8% of the individual readings were at the lower limit of detection of 30 dpm/100 sq. cm.

In the course of data reduction, the raw direct alpha survey data were summarized in terms of range, mean, standard deviation, variance, and other simple statistics as needed for estimating population 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 pop-ulation 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 (three standard deviations) that the population mean lies between 30.09 and 30.01 dpm/100 sq. cm. in the case of the grids and between 30.09 and 30.01 dpm/100 sq. cm. in the case of the indi-vidual readings.

The 99.7% confidence limit is based on the formula UCL = x(mean) + (z)(c)/JN LCL = x(mean) - (z)(c)/JN where z = 3.0 UCL = Upper Confidence Limit LCL = Lower Confidence Limit The data obtained during the original alpha smear survey and shown in Table 5-3 are being used for the releare alpha smear survey.

Precautions were taken during decontamt-nation to prevent the spread of contaminated dust and routine large area smears have shown no trace of smearable alpha activity in the Phase II portion of Building C.

No grid had smearable alpha activity greater than 60 percent of the allowable limit of 20 dpm/100 sq.cm.

The alpha smear survey data were statistically 5-2

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II analyzed in the same manner as the direct alpha survey data.

Table 5-6 contains these results.

Surveys for direct beta, smearable beta, and gamma activity were made in randomly selected floor grid blocks.

The results are shown in Table 5-7.

A survey for gamma radiation was performed in each of 123 floor grids out of a total of 666 in Phase II.

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 nearly equal in all 123 cases indicating no residual gamma contamination was present.

(All 246 readings were between 0.02 and 0.07 mR/hr.

This is the lower limit of detection for the GM meter.) Surveys were per-formed for direct beta and smearable beta activity at the same 123 locations.

As shown in Table 5-7, the beta activity averaged 521 cpm (2000 dpm/100 sq. cm.),.well below the limit of 5,000 dpm/100 sq. cm. for fixed beta activity.

No reading for smear-able beta activity was greater than 310 dpm/100 rq. cm.

The 123 readings were all about 300 dpm/100 sq.

cm. which is the background level for the beta smear instrument.)

5,1.3 Gamma Radiation Survey A survey was conducted in and around Phase II to measure the ambient gamma radiation levels.

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, in addition to terrestial and cosmic radiation, establish the background gamma radiation inside Phase II of Building C.

The data also support the gamma survey data shown in Table 5-7.

5.2 Release Soil Survey Samples were taken from drums of soil excavated from under Building C (drummed soil samples) and samples were taken from the face of ditches in the excavations (ditch face soil sampics).

Samples of site background soil were also taken (background soil samples).

The data are presented in Tables 5-8 through 5-11 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 for all 107 samples are summarized in Table 5-8.

The results for Am-241 and plutonium represent the lower limits of detection for gamma analyses, no Am-241 or Pu activity was found in the background soil samples.

The values given in Table 5-9 for uranium and thorium have been used to correct ditch face and drummed soil samples for local naturally occurring concentrations of these elements.

5-3

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 5.2.2 Ditch Face Release Survey The data are summarized in Table 5-10 for the ditch face survey.

The results for Am-241 and plutonium represent 5 samples in which Am-241 was detected and 80 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 II 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 contam-ination in the drummed soil samples, a series of Bateman decay chain calculations were performed to identify a nuclide that would provide a sensitive indication of U-233 concentration in 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 ditch face samples 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.

The continued ingrowth of Am-241 was recognized and evaluated for its effect upon activity levels in the future.

5.2.3 Drummed Soil Survey The data are summarized in Table 5-11 for the drummed soil release survey.

There are 605 drums of soil that meet release limits.

The results for Am-241 and plutonium represent 36 samples in which Am-241 was detected and 536 samples where Am-241 was reported at the lower limit of detection.

The anal-yses for thorium and uranium indicate primarily background con-centraions for these two elements are contained in the releasable drums.

The background concentrations for thorium and uranium 4

have been deducted for the calculation of the unity factor for i

the releasable drums.

The data from analyses of the drummed soil samples was reviewed for Pb-212 content to address the possibility of poten-tial U-233 contamination.

These data showed that no drums had Pb-212 activity above that expected from the naturally occurring Th-232 parent.

A previous statistical evaluation of both the Pb-212 and Ac-228 activities had indicated that, when the Pb-212 activity was above that expected from the naturally occuring Th-232, the samples had equal concentrations of these isotopes.

(Th-232 produces Ac-228 and Pb-212 daughters.

These two daughters will be in secular equilibrium in geologic soil.

Thus, if their concentrations are found to be equal, a conclusion may be drawn that the Pb-212 originated from Th-232 rather than from U-232 which can also be a parent.)

These results indicate no contamination from U-233.

1 l

5-4 1

DECONTAMINATION AND DECOMMISSIONING CF BUILDING C - PHASE II The drummed soil drum samples data were reviewed for the presence of co-60 and Cs-137 contamination.

None of the release samples indicated concentrations above the experimental background.

The continued ingrowth of Am-241 was recognized and evaluated for its effect upon activity levels in the future.

There were 9 drums of soil that did not meet release limits.

The results for Am-241 and plutonium represented 4 samples in which Am-241 was detected.

The analyses for thorium and uranium indicated some contamination from these two elements was present in the soil in these drums.

The background concen-trations for thorium and uranium have not been deducted for the calculation of the unity factor for these drums.

All 9 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, 5-10, and 5-11 have been summarized statistically and are presented in Table 5-12.

Examination of Table 5-12 shows that the mean of the ditch face soil samples is less than the 99.7% upper confidence level of the background soil samples for Am-241, plutonium, Th-232, and uranimn.' Therefore, we have 99.7% confidence that the concentra-tiens of,any of these substances in the ditch face samples do not statistically exceed their concentrations in the background soil samples.

The same statement is made for the drummed soil samples.

s 5

s I

5-5

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II TABLE 5-1

SUMMARY

OF AVERAGE ORIGINAL DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number Number of Grids of Grids 30 30-100

>100 (average dpm/100 sq. cm.)

Front Offices 1-5 268 268 Front Offices 6-7 108 108 Front Office 8 78 78 Front Office 9 78 78 Front Office 10 78 78 Front Office 11 78 78 Front Office 12 78 78 Lab 15 836 5

841 Lab 16 287 11 298 Lab 17 1087 11 1098 Hallway 23 471 471 Front Hall 471 471 Total 3661 27 3688 5-6

r.

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II 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 (average dpm/100 sq. cm.)

Front Offices 1-5 3480 3480 Front Offices 6-7 1308 1308 Front Office 8 948 948 Front Office 9 948 948 Front Office 10 948 948 Front Office 11 948 948 Front Office 12 948 948 Lab-15 8116 7

1 8124 Lab 16 4608 20 4628 7.ab 17 15208 48 15256 Hallway 23 6682 6682 Front Hall 2542 2542 Total 47384 75 1

47460 l

1 e

5-7

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE Il 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 5-12 (dpm/100 sq. cm.)

Front Offices 1-5 249 49 8

306 Front Offices 6-7 75 26 7

108 Front Office 8 61 14 3

78 Front Office 9 63 12 3

78 Front Office 10 61 12 5

78 Front Office 11 50 24 4

78 Front Office 12 57 12 9

78 Lab 15 710 177 31 918 Lab 16 293 82 9

384 Lab 17 1046 418 105 1569 Hallway 23 386 107 15 508 Front Hall 180 32 2

214 Total 3231 965 201 4397~

r S

5-8

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II TABLE 5-4

SUMMARY

OF AVERAGE RELEASE DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number Number of Grids of Grids 30 30-100

>100 (average dpm/100 sq. cm.)

Front Offices 1-5 268 268 Front Offices 6-7 108 108 Front Office 8 78 78 Front Office 9 78 78 Front Office 10 78 78 Front Office 11 78 78 Front Office 12 78 78 Lab 15 838 3

841

' Lab 16 287 11 298 Lab 17 1089 9

1098 Hallway 23 471 471 Front Hall 471 471 Total 3665 23 3688 t

5-9

.+

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II TABLE 5-5

SUMMARY

OF MAXIMUM RELEASE DIRECT ALPHA SURVEY RESULTS Location Direct Alpha Survey Results Total Number Number of Readings of Readings

(-30 30-300

. >300 aximum dpm/100 sq. cm.)

Front Offices 1-5 3480 3480 Front Offices 6-7 1308 1308 Front Office 8 948 948 Front Office 9 ^

948 948 Front Office 10 948 948 Front Office 11 948 948 Front Office 12 948 948 Lab 15 8818 6

8824 Lab 16 4608 20 4628 Lab 17 15222 34 15256 Hallway 23 6682 6682 Front Hall 2542 2542 Total 47400 60 47260 1

5-10

I s

DECONTAMINATION AND DECOMMISSIONING:OF BUILDING C - PHASE II TABLE 5-6 ALPHA SURVEY RESULTS dpm/100 sq. cm.

Direct Alpha Surveys Alpha Smear Surveys gy Grid gy Reading gy Grid Sample Size 3688 47,460 4,397 Mean 30.05 30.03 1.03~

Standard Deviation 0.82 2.90 1.72 Error.on Mean 0.01 0.01 0.03 99.7% UCL 30.09 30.09 1.11 99.7% LCL 30.01 30.01 0.95 TABLE 5-7

SUMMARY

OF RELEASE DIRECT BETA AND GAMMA AND SMEARABLE BETA SURVEY RESULTS FOR 123 FLOOR GRID BLOCKS IN PHASE II Direct Gamma Direct Beta Smearable Beta Decision Survey Results Survey Results Survey Results uR/hr.

cpm dpm/100 sq. cm.

Average Value Average Value Average Value 37 521 275' Accept Direct Gamma Direct Beta Smearable Beta Decision Survey Results Survey Results Survey Results 4R/hr.

cpm dpm/100 sq. cm.

Maximum Value Maximum Value Maximum Value 65 1000 308 Accept TABLE 5-8 ANALYSES OF BACKGROUND SOIL SAMPLES Number of Activity, pCi/ gram Samples Am-241*

Plutonium

• Th-232 Uranium Avg Max Avg Max Avg Max Avg Max 107**

0.33 0.54 1.43 2.33 1.28 2.12 1.40 2.51 The values shown for Am-241 and plutonium represent minimum detectable levels; i.

e.,

they do not actually indicate-the presence of americium or plutonium, but indicate an upper limit for the values if they were present.

~

• • Of the 107 samples, 45 represent three 15 foot cores and 62 represent one foot and two foot samples from 31 locations.

5-11

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II TABLE 5-9 ACCEPTANCE LIMITS FOR THE BACKGROUND SOIL ACTIVITIES

• Activity, pCi/ gram Bi-214 Pb-214 U-235 Ac-228 Pb-212 T1-208 1.0280 1.079 0.2053 1.738 1.760 1.478

• Details of the calculations for acceptance limits are given in reference 11.

TABLE 5-10 ANALYSES OF DITCH FACE SOIL SAMPLES Number of Activity, pCi/ gram Unity Samples Am-241*

Plutonium

• Th-232 Uranium Factor Avg Max Avg Max Avg Max Avg Max Avg Max 85*

0.35 0.77 1.52 3.32 1.24 1.56 1.41 2.17 0.07 0.16

• Of the 85 values represented for Am-241 and plutonium in this table, 80 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 5-11 ANALYSES OF DRUMMED SOIL SAMPLES Number of Activity, pCi/ gram Unity Samples Am-241 Plutonium Th-232 Uranium Factor Avg Max Avg Max Avg Max Avg Max Avg Max 605*

0.34 1.73 1.48 7.48 1.31 3.49 1.47 3.59 0.07 0.45 9

0.77 1.73 3.34 7.48 3.66 9.05 2.75 5.33 0.98 2.26

• Of the 605 values represented for Am-241 and plutonium in this category, 569 are minimum detectable concentrations; i.

e.,

they do not actually indicate the presence of americium or plutonium, but indicate an upper limit for the values if they were present.

5-12

r-DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II TABLE 5-12 SOIL SAMPLES ANALYSIS RESULTS Am-241 Activity, pCi/g

Background

Ditch Face Drummed Soil Sample size 107 85 605 Mean 0.33 0.35 0.34 Standard Deviation 0.14 0.10 0.12 Error of Mean 0.01 0.01 0.01 99.7% UCL 0.37 0.38 0.36 99.7% LCL 0.30 0.32 0.33 Plutonium Activity, pCi/g

Background

Ditch Face Drummed Soil Sample Size 107 85 605 Mean 1.43 1.52 1.48 Standard Deviation 0.69 0.43 0.54 Error of Mean 0.06 0.05, 0.02 99.7% UCL 1.60 1.66 1.55 99.7% LCL 1.26 1.38 1.42 Th-232 Activity, pCi/q

Background

Ditch Face Drummed Soil Sample Size 107 85 605 Mean 1.28 1.24 1.31 Standard Deviation 0.27 0.13 0.15 Error of Mean 0.03 0.01 0.01 99.7% UCL 1.35 1.28 1.33 99.7% LCL 1.21 1.20 1.29 Uranium Activity, pCi/q

Background

Ditch Face Drummed Soil Sample Size 107 85 605 Mean 1.40 1.44 1.47 Standard Deviation 0.33 0.27 0.29 Error of Mean 0.03 0.03 0.01 99.7% UCL 1.47 1.50 1.50 99.7% LCL 1.32 1.33 1.43-5-13

4 FIGURE 5-1.

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l 5-14 1

l l

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II o

6.0 SURVEY INTERPRETATION An extensive decontamination program was conducted through-out Phase II of Building C.

Based on the survey results shown in Section 5.0, Phace II 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 statis-tical survey was performed for beta-gamma radioactivity.

Fixed alpha contamination was the primary surface contamination found in Phase II with most of the readings (99%) being at the lower limit of detection.

Americium, plutonium, thorium, and uranium from nuclear fuels R&D were the only contaminants found in the soil under Phase II of Building C.

Excavation of soil under the drains continued until samples from the faces and bottoms of the ditches demonstrated release limits had been met with most of the samples (99%) being at background concentrations.

A total of 614,,

55-gallon drums of soil were excavated.

The 9 drums of contam-inated soil were shipped to a licensed commercial radwaste burial site for disposal.

The remaining 605 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 II and all release limits have been met.

Thus, the decon-tamination and decommissioning project for Phase II has been suc-cessfully completed.

Therefore, upon the concurrence of the NRC, Phase II will be released for unrestricted use.

6-1

a.

DECONTAMINATION AND DECOMMISSIONING OF BUILDING C - PHASE II

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.

5.

D.A. Edling and J.F. Grif fin',"~" Certification of ERDA Contractors' Packaging with Respect-to Compliance with DOT Specification 7A Performance Requirements? Phase II Summary Report", MLM-2228, June 12,- 1975.~

c

~

6.

Department of Transportation Hazardous Materials Regulations, Title 49 CFR Part-178.ll8, ~ 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.

i~

8.

NUREG/CR-2082, " Monitoring for compliance with Decommissioning Termination Survey-Crit'eYi'a" with Appendices I through VII, June 1981.

9.

Arthur F. Taggart, " Handbook _of Mineral-Dressing, Ores and Industrial Minerals",' John Wiley & Sons, Inc. 1927.

to W.

T. Cr

" Soil Decontami-10.

Memo, A. F. Olsen, B&W,127 19817 ~ "ow,_NRC, nation Plan", October JlJ i n's..

11.

Memo, N. Soltys, B&W, to R'.

L. Bennett, B&W, " Bldg

'C' decommissioning", January 10, 1985.

7-1

ooccer uo.76-19Y conax. no.

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