ML12020A096
| ML12020A096 | |
| Person / Time | |
|---|---|
| Site: | Plum Brook File:National Aeronautics and Space Administration icon.png |
| Issue date: | 01/04/2012 |
| From: | Mann B US National Aeronautics & Space Admin (NASA) |
| To: | NRC/FSME |
| References | |
| Download: ML12020A096 (65) | |
Text
Plum Brook Reactor Facility Final Status Survey Report 3 Revision 1 Primary Pump House (Building 1134)
FINAL STATUS SURVEY REPORT ROUTING AND APPROVAL SHEET Document
Title:
Final Status Survey Report, 3 Primary Pump House (Building 1134)
Revision Number: 1 ROUTING SIGNATURE DATE Prepared By B. Mann C4
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Prepared By N/A REVIEW & CONCURRENCE Independent Technical Reviewer R. Case T7T"*T Other Reviewer, QA Manager J. Thomas f
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Other Reviewer N/A FSS/Characterization Manager W. Stoner I.,.
I NASA Project Radiation Safety Officer W. Stoner ii
NASA PBRF DECOMMISSIONING PROJECT CHANGE/CANCELLATION RECORD DOCUMENT TITLE: Final Status DOCUMENT NO: N/A REVISION NO: 1 Survey
- Report, Attachment 13, Primary Pump House (Building 1134)
Revision 0: Initial issue of Report Revision 1: Page 27 of the text is revised to correct a typographical error in the 4th bullet of paragraph 2.
7~7 IAD-01131
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Plum Brook Reactor Facility FSSR 3 Rev. I LIST OF EFFECTIVE PAGES DOCUMENT NO:
N/A REVISION NO: 1 Page No.
Revision Level Page No.
Revision Level Page No.
Revision Level Cover Page I
Routing & Approval I
Sheet Change/Cancellation 1
Record LOEP I
TOC 0
List of Tables & List 0
of Figures List of Acronyms &
0 Symbols, 2 pages Text, pages 1 0
through 26 Text, page 27 1
Text, pages 28 0
through 35 Appendix A 0
22 pages Appendix B 0
45 pages
- 4.
4
- 6*
4 I
a I
a 77~71 IAD-01151
[i~J iv
Plum Brook Reactor Facility FSSR 3, Rev. 0 TABLE OF CONTENTS 1.0 Introduction.............................................................................................................
1 2.0 Prim ary Pum p H ouse D escription...........................................................................
2 2.1 Building Layout and Construction...........................................................................
2 2.2 Building System s and Services................................................................................
6 2.3 Building M odifications............................................................................................
7 2.4 Final Configuration and Scope................................................................................
7 3.0 H istory of O perations.................................................................................................
7 3.1 Chronology...........................................................................................................
8 3.2 Startup and Operations...........................................................................................
8 3.3 Radioactive M aterials in the PPH...........................................................................
9 3.4 Post-Shutdown Materials Disposition and Characterization..................................
11 3.5 D ecom m issioning...................................................................................................
11 4.0 Survey Design and Implementation for the PPH.................................................
13 4.1 FSS Plan Requirem ents.........................................................................................
13 4.2 Area Classification and Survey Unit Breakdown....................................................
14 4.3 N um ber of M easurem ents and Sam ples..................................................................
16 4.4 Instrum entation and M easurem ent Sensitivity......................................................
19 5.0 PPH Survey R esults................................................................................................
23 5.1 Scan Surveys...........................................................................................................
23 5.2 Fixed M easurem ents and Tests..............................................................................
24 5.3 A dditional M easurem ents.......................................................................................
26 5.4 Soil Survey U nit Results........................................................................................
28 5.5 Q C M easurem ents...................................................................................................
28 5.6 A LA RA Evaluation.................................................................................................
30 5.7 Com parison w ith EPA Trigger Levels.................................................................
32 5.8 Conclusions............................................................................................................
33 6.0 R eferences.....................................................................................................................
33 7.0 A ppendices....................................................................................................................
35 A ppendix A - Exhibits..............................................................................................................
Appendix B - Survey Unit Maps and Tables Showing Measurement Locations and Results.
v
Plum Brook Reactor Facility FSSR 3, Rev. 0 LIST OF TABLES Table 1, Unusual Incident Reports Involving the PPH (1960-1973)........................................
10 Table 2, PPH Pre-decommissioning Survey Results...............................................................
12 Table 3, PPH Radionuclide Activity Fractions and Gross Activity DCGLs...........................
14 Table 4, Class-Based Survey Scan Coverage and Action Level Requirements.......................
14 Table 5, PPH Survey U nits for FSS.........................................................................................
15 Table 6, PPH Survey Unit Breakdown....................................................................................
16 Table 7, PPH Survey Design Sum m ary.....................................................................................
17 Table 8, Sensitivity Analysis for PPH FSS Design.................................................................
18 Table 9, Typical Detection Sensitivities of Field Instruments.................................................
20 Table 10, Typical Detection Sensitivities of Field Instruments used for Soil Scans................ 22 Table 11, Scan Survey R esults.................................................................................................
23 Table 12, PPH Total Surface Beta Activity Measurement Summary and Test Results........... 25 Table 13, PPH Investigative Static Measurements..................................................................
26 Table 14, Removable Surface Activity Measurements.............................................................
28 Table 15, PPH Soil Survey Unit Sample Results....................................................................
28 Table 16, PPH Total Surface Activity QC Measurements.....................................................
29 Table 17, RPD Evaluation of Replicate QC Surface Activity Measurements..........................
30 Table 18, Screening Level Values for PPH and Radionuclide Activity Fractions...................
31 Table 19, NRC Soil Screening Level ALARA Comparison...................................................
32 Table 20, Comparison of Soil Sample Results with EPA Trigger Levels................................
32 LIST OF FIGURES Figure 1, PBRF NW Area Showing Reactor Building, PPH and Hot Lab................................
2 Figure 2, PPH M ain Floor Layout..............................................................................................
3 Figure 3, Schematic Showing Main PCW Piping Between PPH and Reactor Building............ 5 vi
AEC ALARA AF bi BR BPL CFR cm cm 2
cpm CV A
d' DCGL DCGLEMc DCGLW dpm Ei E,
gpm HTD hr HSOO i
in.
LMI LBGR m2 MARSSIM MDC Plum Brook Reactor Facility FSSR 3, Rev. 0 LIST OF ACRONYMS & SYMBOLS alpha; denotes alpha radiation, also type I error probability in hypothesis testing Atomic Energy Commission As Low As Reasonably Achievable Area Factor beta; denotes beta radiation, also type II error probability in hypothesis testing background counts in observation interval Background count rate Byproduct License Code of Federal Regulations centimeters square centimeters counts per Minute Containment Vessel, the large steel shell surrounding the reactor vessel and adjacent equipment rooms delta, DCGLW - LBGR Scan surveyor sensitivity index Derived Concentration Guideline Level DCGL for small areas of elevated activity, used with the Elevated Measurement Comparison test (EMC)
DCGL for average concentrations over a survey unit, used with statistical tests.
(the "W" suffix denotes "Wilcoxon")
disintegrations per minute Detector, or instrument efficiency Surface efficiency Total efficiency Elevated Measurement Comparison US Environmental Protection Agency Final Status Survey Final Status Survey Plan Final Status Survey Report gamma; denotes gamma radiation gram gallons per minute Hard To Detect hour Health Safety Operations Office observation counting interval during scan surveys inch Ludlum Measurements, Inc.
Lower Bound of the Gray Region square meters Multi-Agency Radiation Survey and Site Investigation Manual Minimum Detectable Concentration vii
Plum Brook Reactor Facility FSSR 3, Rev. 0 LIST OF ACRONYMS & SYMBOLS. Continued MDCscan Minimum Detectable Concentration for scanning surveys MDCstati.
Minimum Detectable Concentration for static surface activity measurements MDCR Minimum Detectable Count Rate mrem millirem MOTA MOTA Corporation, now a subsidiary of Seimplekamp MW Megawatt MWH Montgomery Watson Harza, Inc.
NASA National Aeronautics and Space Administration N
Number of FSS measurements or samples established in a survey design N/A Not Applicable NRC US Nuclear Regulatory Commission PCW Primary Cooling Water PBRF Plum Brook Reactor Facility PNL Pacific Northwest Laboratory PPH Primary Pump House (Building 1134)
(D Standard normal distribution function p
surveyor efficiency for scan surveys pCi/g picocuries per gram percent QC Quality Control RAMS Remote Area Monitoring System RESRAD RESidual RADioactive - a pathway analysis computer code developed by Argonne National Laboratory for assessment of radiation doses. It is used to derive cleanup guideline values for soils contaminated with radioactive materials RESRAD-BUILD A companion code to RESRAD for evaluating indoor building contamination and developing site-specific DCGLs ROLB Reactor Office and Laboratory Building, Building 1141 s
seconds a
generic symbol for standard deviation of a population SAIC Science Applications International Corporation SCW Secondary Cooling Water SEMS Stack Effluent Monitoring System SNL Sandia National Laboratory SR Survey Request tb background count time ts sample count time TBD Technical Basis Document P
Mean activity concentration UCM Unusual Condition Measurement UL Upper limit of the confidence interval about the mean VSP Visual Sample Plan Z1-.
Proportion of standard normal distribution values less than 1 -a ZI-0 Proportion of standard normal distribution values less than 1-3 00 Mathematical symbol for infinity viii
Plum Brook Reactor Facility FSSR 3, Rev. 0 1.0 Introduction This report presents the results of the final status radiological survey of the Plum Brook Reactor Facility (PBRF) Primary Pump House (PPH, Building 1134). It is Attachment 13 of the PBRF Final Status Survey Report (FSSR).' This attachment describes the PPH, its operational history and final condition for the final status survey (FSS). It describes the methods used in the FSS and presents the results of the survey measurements.
As stated in the PBRF Final Status Survey Plan (FSSP) [NASA 2007], the goal of the decommissioning project is to release the facility for unrestricted use in compliance with the requirements of US NRC 10CFR20 Subpart E. The principal requirement is that the dose to future site occupants will be less than 25 mrem/y. Subpart E also requires that residual contamination be reduced to levels as low as reasonably achievable (ALARA). A Derived Concentration Guideline Level (DCGL) for residual surface contamination has been established for the PPH. Considering the radionuclide mixtures established for the PPH, the gross activity DCGL is 26,348 dpm/I00-cm 2.2 The survey measurement results and supporting information presented herein demonstrate that residual contamination levels in each survey unit of the PPH are well below the DCGL. Additionally, it is shown that residual contamination has been reduced to levels that are consistent with the ALARA requirement. Therefore, the PPH meets the criteria for unrestricted release.
Section 2.0 of the report provides a description of the PPH. This includes the building layout, its relation to other PBRF buildings and facilities, design and materials of construction, building contents and use, systems and services, building modifications, final configuration for the FSS and scope of the FSS for this building.
A brief history of operations is presented in Section 3.0. A chronology of significant milestones is followed by history of operations with radioactive materials. Post shutdown and decommissioning activities are summarized.
Section 4.0 presents the FSS design for the PPH. This section includes applicable FSS Plan requirements, breakdown into survey units and assignment of MARSSIM classification to each, the survey design approach, instrumentation used for the FSS and measurement sensitivities.
Survey results are presented in Section 5.0. This section includes a summary of the FSS measurements performed in the PPH survey units, comparison to the DCGL, tests performed and an evaluation of residual contamination levels relative to the ALARA criterion.
Supporting information is contained in Appendices. Appendix A contains photos and schematics to supplement the text. Survey design maps, tables of coordinates and total surface beta measurement results for each survey unit are provided in Appendix B.
I The PBRF Final Status Survey Report comprises the report main body and several attachments. The attachments present survey results for individual buildings and open land areas. The entire final report will provide the basis for requesting termination of NRC Licenses TR-3 and R-93 in accordance with 1 OCFR50.82 (b) (6).
2 As discussed in Section 4.0, in accordance with PBRF-TBD-07-001 [PBRF 2007] the gross activity DCGL is 26,348 dpm/100-cm2 for all the PPH areas except Room 4, which due to the unique radionuclide mix, was assigned a DCGL of 11,186 dpm/I00-cm 2. Also, one soil survey unit was established in the PPH. The DCGL for this survey unit is 6.23 pCi/g.
I
Plum Brook Reactor Facility FSSR 3, Rev. 0 2.0 Primary Pump House Description The Primary Pump House is located adjacent to and shares a common wall on the east side of the Reactor Building. It housed the major components of the reactor primary cooling water system. This included primary coolant pumps (three 8650 gpm pumps), two large heat exchangers, flow measuring and coolant monitoring equipment, a cleanup system and a fuel element test rig.
2.1 Building Layout and Construction Figure 1, a map of the PBRF main facility area shows the Reactor Building and adjacent support buildings, the Primary Pump House and Hot Lab. Views of the PPH exterior are shown in Exhibit 1 of Appendix A. The PPH is of concrete construction with walls and roof designed to provide shielding from gamma radiation originating in the primary coolant and contaminated process equipment. The south and east walls contain sections with removable concrete blocks to provide access for large equipment replacement (heat exchangers, pumps, etc).
Figure 1, PBRF NW Area Showing Reactor Building, PPH and Hot Lab D!
513 IlL Fr,"
"DEMOUSHED BUILDING5 5EB 5ERVICE5 EQUIPMENT DUILDING FH1 FAN HOU51 WHD WA5TE HANDUNG DUILDING ROLW REACTOR OFFICE $ #LAORATORY BUILDING HRA HOT RETENTION AREA
"'THE5E DUILDING5 WERE DEMOU5I=ED TO -3 ft.
ELEVATION AND BACK.FILLED.
2
Plum Brook Reactor Facility FSSR 3, Rev. 0 The principal primary cooling water (PCW) system components are located on the main floor (at the PBRF 0 ft. elevation) of the PPH in heavily shielded rooms. The PPH main floor layout is shown in Figure 2. The three main coolant pumps were housed in individual pump rooms (Rooms 1 through 3) located adjacent to the main equipment galley, or Heat Exchanger Room (Room 4). The pumps were located on elevated platforms at the 7ft. 3 in. mezzanine level in each pump room. In addition to the two primary cooling system heat exchangers, Room 4 contained a venturi flow meter, a large strainer, associated PCW and secondary cooling water (SCW) supply and return and vent/relief piping and valves. It also contained PCW connections to the PCW by-pass cleanup system, and the PCW supply head tank (emergency and regular fill lines), and instrumentation (PCW differential pressure for flow, N-16 detector, PCW pressure, etc.).
Figure 2, PPH Main Floor Layout Figure 2 Note: The Resin Pit has been removed (demolished and excavated - 2010).
Rooms 5 and 6 housed PCW liquid and gaseous radioactive waste treatment equipment.
Room 5 contained the PCW degassifier system including a degassifier, recirculation pump, steam generator, superheater, recombiner, condenser, vacuum pump, moisture separator, water cooled compressor, gas storage tank and condensate tank with associated piping and instrumentation. Room 6 housed two mixed-bed de-ionizers, two pumps, a filter and one heat 3
Plum Brook Reactor Facility FSSR 3, Rev. 0 exchanger for the by-pass cleanup system, plus associated piping, instrumentation and connections to the waste sump located in Room 8 and the adjacent resin pit.
Room 7, which ran the length of the PPH on the north side of the Pump Rooms at the -4 ft.
elevation, included a mezzanine. This was located above and to the north of the Pump Rooms at the 7 ft. 3 in. elevation. This level, housed the three 600 HP PCW pump motors. The main floor of Room 7 served as an operating area. It contained pump motor control centers (the main PCW pump controls were located in the Reactor Control Room) and valve operating extensions. It also contained the fuel element test rig (used to test the mechanical integrity of new reactor fuel elements received from fuel fabrication contractors) on the lower level.
Room 8, on the 0 ft. elevation located on the east side of the PPH adjacent to Rooms 5 and 6 contained an electrical control center, valve extensions, a resin discharge sump, a sampling hood and a monorail crane for removing the PPH waste sump shield plug. A deionizer waste resin pit that was located outside below grade near the southeast comer of the building was connected to the waste resin discharge sump.
The five ft. thick PPH west wall (common wall with the Reactor Building) extends to the -15 elevation. The south end of the below grade portion of this wall is part of a concrete enclosure surrounding the 24 in. main PCW supply and return piping where it emerges from the PPH.
This structure extends from beneath PPH Room 4 to the outer radius of the Reactor Bioshield, a linear distance of approximately 110 ft. From the PPH, the PCW piping runs underneath the Reactor Building and connects to the Reactor Vessel at the - 34 ft. elevation. A schematic of the PCW piping between the PPH and the Reactor Containment Vessel (CV) is shown in Figure 3. The Cold Pipe Tunnel (CPT) passed beneath Room 7, but was not connected to the PPH.3 The PPH roof was constructed of three-ft. thick concrete covered with 1" rigid insulation board topped with a built -up 4-ply bitumen and gravel finish. Access to the interior of Rooms 1 to 6 was provided through roof openings (hatchways and manholes) that were normally closed with shield plugs; these shielding plugs were removable using gantry type cranes located at various positions on PPH roof pads. The roof also contained vents and roof drains. The roof perimeter was bordered with safety hand-rails.
The PPH was not continuously occupied during PBRF operations. The PPH equipment required only periodic checks to ensure proper performance. During routine operations, personnel periodically entered Rooms 7 and 8 to monitor equipment, take primary water samples and collect operational data. The equipment rooms (Rooms 1 through 6) were primarily accessed only for equipment repair, maintenance or modification. These rooms were generally "high radiation areas" during reactor operations. Routine personnel access to the PPH was provided through a door on the west side connecting Room 7 directly to the Reactor Building. Personnel doors on the south and north sides provided access from outside at grade level. A ladder mounted on the south exterior provided personnel access to the roof area. A large truck door was located on the east side of the building.
3 The FSS of the CPT is reported as part of the Service Equipment Building in Attachment 2 of the PBRF FSS Report.
4
Plum Brook Reactor Facility FSSR 3, Rev. 0 Figure 3, Schematic Showing Main PCW Piping Between PPH and Reactor Building 2
PPH ROOM 4 HEAT EXCHANGERS REACTOR
-6.-s.
-12'-2"
-34'-0"
-39'-G" 5
Plum Brook Reactor Facility FSSR 3, Rev. 0 2.2 Building Systems and Services In addition to the PCW and process systems described above, the PPH was connected to most of the PBRF common building services and utilities. These included station electric power, high and low pressure steam for process system and space heating, domestic water, fire protection, secondary cooling water and building ventilation. No sanitary sewer connections were provided to the PPH. Of special note are radioactive process waste handling and monitoring systems. These include the PPH ventilating air system, the hot drain system and the Remote Area Monitoring System (RAMS).
The PPH ventilating system was designed to maintain negative air pressure in the building interior by pulling outside air through roof plug and wall penetration interfaces, valve stems, pipes and conduits. Contaminated air was collected by vent risers in the Heat Exchanger Room, the three pump rooms, the degassifier room (Room 5), the bypass deionizer cleanup room (Room 6), and the PPH sump (which collected contaminated air from the resin pit and the sump tank). A 6 in. fresh air inlet line provided a continuous purge of the sump. There were also vent relief valves located on the primary pumps, the primary pump inlet header and the PCW strainer and PCW line shutoff valves. These vented air and primary coolant to the floor drains. The eight vent risers drew air from the aforementioned vents, valve stem seals, roof plugs, pipe and conduit seals and the discharge from the PCW degassifier gas storage tank in a manner that induced uncontaminated air inflow from outside the PPH to the contaminated spaces inside the building. The vent risers exhausted to the eight inch PPH ventilating air line which connected to the Fan House via the underground ventilation exhaust header. Exhaust air from the PPH and other PBRF buildings was filtered and monitored prior to release to the Fan House Stack.
Contaminated water from PPH equipment drains and floor drains was collected in the main PPH sump located below grade in the south end of Room 8. This sump connected to underground Hot Drain System collection piping that fed contaminated waste water to the Hot Retention Area tanks for storage and processing as described in Attachment 5 of the FSS Report.
The RAMS provided essential information on PPH conditions, as the building was not routinely occupied. The system provided continuous radiation monitoring information to the Health Safety Operations Office (HSOO) in the Reactor Office and Laboratory Building (ROLB) and to a panel in the Reactor Control Room (in the Reactor Building). The RAMS had the capacity to receive information from up to 100 field monitoring units located throughout the PBRF. Field units included radiation detection instruments for monitoring airborne activity (particulate and radioiodine), activity in process water and direct radiation levels. The base units (containing receiver channels, recorders and alarm annunciators) were located in the HSOO. Detectors for airborne particulate activity and direct radiation were 6
Plum Brook Reactor Facility FSSR 3, Rev. 0 located in PPH Room 7 on the mezzanine level (12 ft. elevation) and in Room 8 near the south door. 4 2.3 Building Modifications The PPH was operated as designed and built, with only minor modifications after initial startup. The external ladder to the roof was removed and a stair case added in the 1960s to provide a safer means for personnel access to the roof. A PCW sampling hood was added to Room 8 and the fission product monitoring system removed in about 1969. The roof was modified sometime in the 1980-90 time period, with the addition of a foam sealant layer to minimize rainwater leakage into the building. Also, the roof was repaired during decommissioning (circa 2006) to mitigate rainwater in-leakage.
2.4 Final Configuration and Scope Configuration of the PPH for the FSS and the period until license termination is controlled by PBRF decommissioning and FSS procedures. The structure was intact for the FSS except for the following:
- the floor concrete of Room 3 was removed (a soil survey unit was added to cover the exposed soil beneath),
- the concrete roof plugs were removed 5 and
- the Resin Pit formerly located adjacent to the south wall has been removed by excavation.
6 For the FSS, the PPH was essentially stripped of equipment and fixtures (see Section 3.5 for a summary of equipment removal and preparation of surfaces). Utilities and services are limited to temporary lighting and power. The scope of the FSS includes the basic building structure interior surfaces and exterior walls and roof. Primary Pump House conditions at the time of the FSS are illustrated by photos in Appendix A (see Exhibit 1 and Exhibits 4 through 20).
3.0 History of Operations A chronology of major PBRF milestones which include the PPH is given below. This is followed by a discussion of building operations, post-shutdown and decommissioning activities. Emphasis is on 4 Descriptions of the RAMS are provided in the PBRF Operations Procedures Manual, system Procedure OSY-7617 located in PBRF Records Management Files Box #23, Remote Area Monitoring System. Also, PBRF Training Manual, Section 8.4, Remote Area Monitoring System.
5 Materials removed from PBRF facilities prior to FSS are evaluated for disposition under PBRF Radiological Control Procedures, primarily RP-008, Radiological Release of Equipment, Material and Vehicles.
6 The FSS of the excavated area formerly occupied by the Resin Pit is reported in Attachment 16 of the PBRF FSS Report.
7
Plum Brook Reactor Facility FSSR 3, Rev. 0 operations with radioactive materials that could affect the final building condition and final status survey.
7 3.1 Chronology Major PBRF and PPH milestones are listed below:
1956 - September, groundbreaking for PBRF.
1957 - PPH construction initiated.
1959 - PPH structure completed. 8 1961 - June, 60 MW Test Reactor critical.
1963 - Full Power 60 MW Test Reactor Operations begin.
1973 - January 5 th, Reactor shutdown (after 152 "cycles").
1973 - June 30, PBRF facilities placed in "standby condition".
1985 - Initial radiological characterization, Teledyne Isotopes Inc.
1989 - Follow-up radiological characterization, GTS-Duratek.
2002 - Decommissioning Plan approved; initial equipment removal and building decontamination.
2006-2010 - Remediation of PPH contaminated areas and preparation for FSS.
2011 - FSS measurements completed.
3.2 Startup and Operations Construction of the PPH was mostly completed in the 1959-1960 timeframe. The PPH was an integral part of reactor operations and it was utilized throughout the reactor operations period and during preparation for reactor standby status in 1973. The PPH systems were first utilized in 1960 for hydraulic testing of the primary cooling water system before reactor criticality in June 1961 and subsequently for low power testing. The PPH building was utilized from 1960 through the period of PBRF 60MW test reactor operations from June 1961 to January 1973, 7 Information sources for the history and pre-decommissioning period include, construction photos, construction drawings, PBRF operating cycle reports, Radiochemistry periodic reports, PBRF Annual Reports, Unusual Occurrence Files, memoranda and other historical files maintained by PBRF Document Control.
8 Construction photos show that PPH construction was underway in 1957 and the structure completed in 1959 [PBRF 2009].
8
Plum Brook Reactor Facility FSSR 3, Rev. 0 and then for a short period post shutdown to clean the system and prepare it for standby condition.
3.3 Radioactive Materials in the PPH The US Atomic Energy Commission (AEC) authorized operations and use of radioactive materials at the PBRF under several licenses. 9 License No.TR-3 (Docket 50-30) authorized the 60 MW test reactor. The 100 KW mock-up reactor was licensed under License No. R-93.
A broad byproduct license (BPL) No. 34-06706-03, authorized possession and use of radioactive materials (byproduct material) produced by the Plum Brook 60MW and Mockup reactors and other radioactive materials [PBRF 2009].
The main source of radiation fields and radioactive materials in the PPH was the primary cooling water which carried activation and fission products from the reactor core where they were deposited throughout the PCW piping and components. Radioactive materials were removed from the coolant by the by-pass cleanup and degassifier systems. In addition to the primary circuit piping and components and cleanup systems, the resin disposal system, hot drains and sumps, ventilation systems and sample collection points were contaminated.
Radioactive materials (primary cooling water, resins and other samples) were routinely transported from the PPH to the radiochemistry and metallurgy laboratories in the ROLB. For example, primary reactor coolant samples were routinely carried from Room 8 in lead casks or other shielded containers for counting and analysis in the radiochemistry labs. This process occasionally led to minor spills. In addition, contamination occurred in various locations from PCW valve leakage, PCW main and auxiliary pump seal leakage or failure, and maintenance activities such as PCW strainer cleanout and pump replacement. The PPH was designed and operated to confine and control leaks and spills from potential sources (PCW water leakage, ventilating air, spent resins, etc.). They were contained and directed to hot storage facilities and systems where they were sampled, monitored and treated to ensure compliance with the AEC regulations prior to release to the environment. However a number of incidents and spills occurred which resulted in contamination of PPH structures.
Unplanned incidents in PBRF facilities, including the PPH, were documented in PBRF Health Safety Operations Office Operations Cycle Reports. Table 1 summarizes the unusual incident reports for PPH related activities.
9 Authority for the PBRF reactor and radioactive materials licenses was assumed by the US Nuclear Regulatory Commission in 1975.
9
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 1, Unusual Incident Reports Involving the PPH (1960-1973)
Report Date Description Cycle No.
10 12/26/1963 Contaminated primary cooling water from the Tungsten-i185 sampling resin column drained from the Room 8 floor drain to the cold sump at the Reactor Building -15 ft.
elevation. It was determined that the Room 8 floor drain was required to be a "hot drain".
11 2/4/1964 Radiation levels of up to 500 mrad/hr were measured on the PCW sampling hood drain line in Room 8. A PCW leak discovered in the rear of the sampling hood had spilled onto the floor. The line was repaired and the floor decontaminated.
12 2/8/1964 Pieces of spiro-helic gasket reading 1.5 Rad/hr were found in the PCW strainer.
15 3/26/1964 Radiation levels of up to 400 mR/hr were measured on the PCW sampling hood drain line. The area was posted and the drain line shielded.
15 4/4/1964 Radiation levels of up to 6.5 rad/hr were measured on piping and valves associated with the PH meter in Room 8. The area was appropriately zoned and posted.
23 9/21/1964 Radiation levels of up to 25 Rad/hr were measured at the fission product monitor cabinet door in Room 8. This was attributed to high PCW activity - probably from minor fuel leaks. Shielding was added.
27 11/8/1964 One gallon of PCW was spilled in Room 8. It drained to a cold floor drain near the PCW sampling hood. The cold floor drain was converted to a hot drain line.
68 10/28/1967 Primary cooling water was discovered to be leaking from the fission product monitor in Room 8. The leak was repaired and the area decontaminated.
80 9/23/1968 While back-flushing the PCW cleanup loop filters, high activity was recorded on the PBRF Stack Effluent Monitoring System (SEMS). A radiation survey of the filter housing recorded 60 mR/hr.
84 12/3/1968 A fan belt failure in the PCW sampling hood caused a buildup of airborne activity from off gassing of a PCW sampling line that was left on slow purge. Airborne activity of 7 x 10"9 ptCi/ml beta-gamma was measured in the vicinity. The fan was repaired and air activity was reduced to normal levels.
127 5/21/1971 RAMS #27 indicated high airborne activity on the mezzanine Level near 10POl pump shaft opening (2 x 10-7 p Ci/ml beta-gamma). The opening was calked. During this investigation a small PCW leak (3 x 10-2 ptCi/ml) was noted in the PPH-Reactor Building wall. The area was established as a controlled area and a commercial absorbent applied (Zorb-all). The open valve was closed.
136 11/27/1971 Primary cooling water leaking through an open isolation valve and a leaking check valve in PPH Room 8 contaminated the deionized water line in the CPT and the SEB lab. A sample of the contaminated water measured 3 x 10-3 tCi/ml (beta-gamma).
The affected lines were purged to the hot drains.
139 2/24/1972 A deionized water sample taken in the PPH Room 8 sink measured 1.2 x 10-4 jCi/ml (beta-gamma). It was suspected that PCW had leaked through the pH meter lines contaminating the truck fill line in Room 8.
148 9/17/1972 A gasket blew out of the north by-pass cleanup deionizer in PPH Room 6 causing an 80-90 gpm PCW leak and resin spill. Three inches of water and resin were found on the floor creating a direct radiation field of 2.5 Rem/hr at three feet. The area was cleaned up and the waste packaged in radwaste drums. Radiation levels of up to 10 R/hr at the drum surfaces and work area fields of up to 5 R/hr were measured.
10
Plum Brook Reactor Facility FSSR 3, Rev. 0 3.4 Post-Shutdown Materials Disposition and Characterization In the period following termination of reactor operations in January 1973 and June 30th of 1973, layup of PPH systems was performed in accordance with the PPH "end-condition statement". The PBRF end condition statements governed the status of each system for the protected safe shutdown mode. The end condition statement required flushing, decontaminating the PCW and associated systems and components. Layup efforts included installation of a continuous nitrogen purge system to keep the PCW system dry. Following shutdown, activities were controlled under modified NRC licenses TR-3, R-93 and Byproduct Material License No. 34-06706-03. Selected materials, equipment and waste (both low level radioactive and non-radioactive) were removed to other locations or disposed of. A brief summary of post-shutdown activities is provided in the NASA PBRF Decommissioning Plan, Revision 6 [NASA 2008]. 10 The radiological status of the PPH has been investigated on several occasions since the PBRF was shutdown in January 1973. The initial post shutdown survey was performed in 1973 by Teledyne Isotopes Inc., the NASA radiological support contractor. The 1973 PPH surveys reported high direct radiation levels in contact with equipment of up to 5 R/hr (West Heat Exchanger - south end) and general area dose rates in equipment rooms of about 5 mR/hr. A summary of the 1973 survey results was provided in the 1987 Teledyne report [TELE 1987].
A comprehensive decommissioning planning and evaluation study was performed by Teledyne Isotopes, Inc. during 1984-86. This study included radiological surveys of most of the PBRF facility [TELE 1987]. The Teledyne Isotopes study reported that all the PPH pumps, other equipment and piping were contaminated and would require removal and disposal as contaminated waste. Piping and equipment residues in the PPH contained primarily Co-60, Sr-90 and Cs-137. Removable surface contamination levels measured on equipment external surfaces ranged up to 26,000 dpm/100-cm 2 beta and 44 dpm/I00-cm 2 alpha [TELE 1987].
At the time of the 1984-86 Teledyne study, direct radiation levels in the PPH equipment rooms ranged from < 1 mR/hr up to 75 mR/hr (in the vicinity of the heat exchangers).
Removable surface contamination levels on PPH structure surfaces reported in the Teledyne study were low, with maximum smear sample results of 30 dpm/100-cm 2 (both for beta and alpha). It was concluded in the Teledyne report that "the Building 1134 structure has but minimal contamination" [TELE 1987]. 11 The PPH was not covered in the 1998 Plum Brook Confirmatory Survey performed by GTS-Duratek [GTS 1998].
3.5 Decommissioning In October of 2003, the decommissioning contractor performed comprehensive surveys in PPH Rooms 1 through 6 [PBRF 2005]. High levels of total and removable surface contamination were found, with the highest readings summarized in Table 2.
10 See PBRF Decommissioning Plan, Section 1.2.1 Historical Overview.
11 In contrast to the Teledyne conclusion that the PPH structure was minimally contaminated, characterization surveys performed during 2003 - 2009 showed extensive contamination of the structure.
11
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 2, PPH Pre-decommissioning Survey Results Total Surface Activity Removable Surface Activity PPH Equipment or Structure Beta (1)
Alpha (I)
Beta 1 Alpha (1)
Surface Equipment 980k (2) 389 2k 1
Struct. Surface 1.3M (3) 502 7k 2
Equipment 2.3M 175 370 Struct. Surface 5.3M 267 15k 3
Equipment 2.OM 470 2k Struct. Surface 3.4M 312 20k 4
Equipment 1.6M 597 320 103 Struct. Surface 1.3M 490 2k 21 5
Equipment 550k 239 7k 13 Struct. Surface 160k 224 120 8
6 Equipment 240k 221 172 42 Struct. Surface 1.5M 383 145 Table 2 Notes:
- 1. Units are dpm/100-cm 2.
- 2. k represents kilo or multiplier of 1000.
- 3. M represents a multiplier of one million.
All equipment housed in the PPH was removed and disposed of as contaminated waste or recyclable materials during 2004 and 2005. All tanks, piping, fans, electrical cabinets, instrument and control panels, metal gratings, etc. were shipped for disposal.
After removal of equipment and piping from the rooms, sub-floor drain and process piping was decontaminated during 2006 and 2007. Following decontamination, the piping was surveyed for FSS using structural DCGL values. Results of the PPH piping FSS are reported in Attachments 9 (Embedded Piping) and 17 (Buried and Miscellaneous Piping) of the PBRF Final Survey Report. The 24 inch PCW piping (including the remnants that entered Room 4) was decontaminated and surveyed to meet FSS Plan embedded piping DCGL values. The piping above 3 ft. below grade was cut off and disposed of. The remaining piping (below 3 ft.
below grade) was grouted in place.
Also, during 2006 and 2007, the decommissioning contractor remediated the surfaces of PPH rooms by sponge blasting the walls and ceilings. Floor shaving was performed in rooms 4, 7 and 8. Local areas required aggressive remediation by scabbling and related mechanical means. Core bores were used to remove contaminated concrete around penetrations and to remove local areas of concrete contaminated to depth. Extensive areas of the Room 3 floor were determined to have volumetric contamination above DCGL values and the floor was removed in 2009. See Exhibits 4 through 18 for illustration of the extensive remediation performed in the PPH. 12 12 The summary of PPH decommissioning activities is adapted from Survey Design No. 47, Section 2.0, History.
12
Plum Brook Reactor Facility FSSR 3, Rev. 0 Radiological surveys performed in support of the PPH decommissioning activities are summarized above. The objective of final post-remediation surveys was to ensure that the PPH could satisfy the release criteria with a high probability of success. Surveys were performed in 2006 by the decommissioning contractor in 2006 (MOTA) and by Science Applications International Corporation (SAIC) in 2009 in support of remediation and preparation for FSS. 13 The radionuclide mixture for development of the PPH gross activity DCGL for the FSS was reported in TBD-07-001 [PBRF 2007]. The information used to develop the radionuclide profile was obtained from characterization samples collected in the PPH in 2003 and other PBRF buildings in 2005.
4.0 Survey Design and Implementation for the PPH This section describes the method for determination of the number of fixed measurements and samples for the FSS of the PPH. Applicable requirements of the FSS Plan are summarized. These include the DCGLw14, the gross activity DCGL, scan survey coverage and action-investigation levels, classification of areas and breakdown of the survey units. Radiological instrumentation used in the FSS of the PPH and their detection sensitivities are discussed.
4.1 FSS Plan Requirements The DCGLs for individual radionuclides were obtained for PBRF structures considering exposure to future site occupants from two potential pathways. Single radionuclide DCGLs were calculated using RESRAD-BUILD Version 3.22 for a building reuse scenario. Single radionuclide volumetric DCGLs were calculated for subsurface structures using RESRAD Version 6.21 for a resident farmer scenario. 15 The volumetric DCGLs (in pCi/g) were converted to "effective surface" DCGLs (in dpm/100-cm 2) using surface-to-volume ratios for the assumed volume of contaminated subsurface concrete. The DCGL calculations are described in the FSSP, Attachment B. To obtain the DCGLs for PBRF structures, the smaller of the two DCGLs calculated for each of the radionuclides of concern were selected.
A gross activity DCGL is used for structural surfaces in the PBRF, where multiple radionuclides are potentially present in residual contamination. The gross activity DCGL accounts for the presence of multiple radionuclides, including beta-gamma and alpha emitters.
The gross activity DCGL can also account for so-called hard-to-detect (HTD) radionuclides.
The latter are not detected, or detected with very low efficiency, by the beta detectors selected for the FSS of structures.
13 Final PPH post remediation surveys were performed under Survey Request SR-1 18.
14 The convention used in the MARSSIM is to identify the DCGL used as the benchmark for evaluating survey unit measurement results, as the DCGLw. The "W" subscript denotes "Wilcoxon", regardless of the particular test used (Wilcoxon Rank Sum Test, or Sign Test).
" Potential exposure to future occupants from subsurface structures could occur from contaminated concrete rubble placed as fill and from contaminated intact structures such as the below-grade portion of the Reactor Bioshield.
13
Plum Brook Reactor Facility FSSR 3, Rev. 0 The gross activity DCGL for the PPH is calculated using equations in the FSSP for gross beta, gross alpha and surrogate DCGLs, based on the radionuclide mixture in residual contamination. Activity fractions and the gross activity DCGLs for the PPH are shown in Table 3.
Table 3, PPH Radionuclide Activity Fractions and Gross Activity DCGLs Radionuclides DCGLw Location H-3 Co-60 Sr-90 1-129 Cs-137 Eu-154 U-234 U-235 (dpm/100-
~m 2)
Activity Fractions Assigned to PPH dm Room 4 (2) 0.4291 0.0956 0.0256 0.2255 0.1892 0
0.0334 0.0016 11,186 All Other Rom 0.5422 0.0866 0.0939 0
0.1881 0
0.0805 0.0087 26,348 Rooms Exterior Surfaces (3) 0.2707 0.0965 0.0788 0.0142 0.4671 0.0012 0.0698 0.0017 27,166 Table 3 Notes:
- 1. Activity profiles and gross activity DCGLs for structures are reported in the Technical Basis Document PBRF-TBD-07-001 [PBRF 2007].
- 2. The DCGL for PPH Room 4 was established in TBD-07-001 as 11,186 dpm/100-cm 2. This was due to the unique radionuclide composition obtained from Room 4 characterization samples whereby I-129 and Co-60 (both with relatively low DCGLs, 14,900 and 11,000 dpm/100-cm 2, respectively) constituted over 1/ 3rd of the activity.
- 3. The default radionuclide mixture and DCGL for PBRF structures reported in TBD-07-001 was applied to PPH exterior surfaces.
Survey designs incorporate requirements for scan coverage and investigation levels derived from the MARSSIM classification of survey units. The values applicable to the PPH are shown in Table 4.
Table 4, Class-Based Survey Scan Coverage and Action Level Requirements Static Measurement Classification Scan Survey Scan Investigation or Sample Result Coverage Levels Investigation Levels Class 1 100%
> DCGLEMC
> DCGLEMC Class 2 10 to 100%
> DCGLw or > MDCSC
> DCGLW if MDC,,a is > DCGLw
>_DCG
_w Class 3 Minimum of 10% > DCGLw or > MDCS, 2 if
> 50% of the DCGLw
_ las_ 3 Minmu of___
10%_____MDCscn is > DCGLw 4.2 Area Classification and Survey Unit Breakdown The PPH was divided into 12 survey areas, all classified as MARSSIM Class 1, as shown in Table 2-1 of the FSS Plan. As part of the FSS implementation process, individual survey units 14
Plum Brook Reactor Facility FSSR 3, Rev. 0 were identified and their final MARSSIM classification established. The PPH building interior was divided into 30 survey units and the building exterior into 12 survey units, all Class 1, for the FSS. These are identified in Table 5. Table 5 also identifies the Survey Design and Survey Request associated with each survey unit. Table 6 summarizes the survey unit breakdown by major elevation (building interior and exterior). 16 Table 5, PPH Survey Units for FSS SuvyArea Survey Class in Survey Class Ae Sre SR #
Description FS 2
Unit (1)
(M2)
Design SR#
Description_
FSSP (2)
PH-I-1 1
64.5 27 323/339 Room 1 -Floor, Ceiling, Platform, I
PH-1-2 1
84.4 27 323/339 Room 1 -Walls 1
PH-1-3 1
64.6 27 323/339 Room 2 - Floor, Ceiling, Platform, 1
PH-1-4 1
84.1 27 323/339 Room 2-Walls I
PH-1-5 1
58.7 27 323/339 Room 3 - Floor, Ceiling, Platform, 1
PH-1-6 1
86.9 27 323/339 Room 3 - Walls I
PH-1-7 1
72.3 27 322/339 Room 4 - Floor Section 1 1
PH-1-8 1
53.1 27 322/339 Room 4-Floor Section 2 1
PH-1-9 1
99.0 27 322/339 Room 4 - West & North Walls 1
PH-1-10 1
93.8 27 322/339 Room 4 - East & South Walls & Wall penetrations PH-I-11 1
56.4 27 322/339 Room 4 - W Ceiling & Hatchway I
PH-I-12 1
52.9 27 322/339 Room 4 - E Ceiling & Hatchway 1
PH-I-13 1
40.3 27 323/339 Room 5 -Floor, Ceiling, & Hatchway 1
PH-1-14 1
75.5 27 323/339 Room 5-Walls 1
PH-I-15 1
51.9 27 323/339 Room 6-Floor, Ceiling, & Hatchway I
PH-1-16 1
98.4 27 323/339 Room 6-Walls 1
PH-1-17 1
69.3 26 132 Room 7 & 8 - Floor Section 1 1
PH-1-18 1
45.2 26 132 Room 7 & 8 -Floor Section 2 1
PH-1-19 1
42.6 26 132 Room 7 & 8 - Floor Section 3 1
PH-1-20 1
56.6 26 132 Room 8 Sump I
PH-1-21 1
84.1 26 133 Room 7 & 8 - Wall Section 1 & West Stairs PH-1-22 1
95.2 26 133 Room 7 & 8 - Wall Section 2 PH-1-23 1
89.2 26 133 Room 7 & 8 - Wall Section 3 & East Stairs PH-1-24 1
71.3 26 133 Room 7 & 8 - Wall Section 4 1
PH-1-25 1
93.7 26 133 Room 7 & 8 - Wall Section 5 1
PH-1-26 1
99.2 26 133 Room 7 & 8 - Wall Section 6 1
PH-1-27 1
94.4 26 133 Room 7 & 8 - Platforms 1
PH-1-28 1
94.1 26 134 Room 7 & 8 - Ceiling Section 1 1
PH-1-29 1
87.1 26 134 Room 7 & 8 - Ceiling Section 2 1
PH-1-30 1
11.4 47 342 Room 3 soil.
1 PH-2-1 1
98.0 68 347/350 Roof Section #1 1
16 The calculations performed in preparation of this report are documented in a memorandum to the PBRF Decommissioning Project File [PBRF 2011].
15
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 5, PPH Survey Units for FSS Surve Area Survey Class in Unit Class SR #
Description FSSP (2)
Unit____
(in2)
Design FS 2
PH-2-2 1
98.3 68 347/350 Roof Section #2 1
PH-2-3 1
70.5 68 347/350 Roof Section #3 1
PH-2-4 1
67.0 68 347/350 Roof Section #4 1
PH-2-5 1
93.6 68 347/350 Roof Section #5 1
PH-2-6 1
90.4 68 347/350 Roof Section #6 1
PH-2-7 1
53.0 68 347/350 South Wall - Lower 1
PH-2-8 1
94.2 68 347/350 South Wall - Upper PH-2-9 1
45.6 68 347/350 East Wall - Lower PH-2-10 1
88.0 68 347/350 East Wall - Upper 1
PH-2-11 1
56.8 68 347/350 North Wall - Lower 1
PH-2-12 1
91.5 68 347/350 North Wall - Upper 1
Table 5 Notes:
- 1. The FSSP Table 2-1 identified 12 PPH survey areas. For the FSS, this was divided into 42 survey units to meet FSS Plan classification-based size limits.
- 2.
The FSS Plan classification was based on area history and available characterization data.
Table 6, PPH Survey Unit Breakdown No. of Surface
% of Survey
% of Surface Survey Units Area (m2)
Units Area Building Interior 30 2170.2 71 70 Outside Walls &
12 946.9 29 30 Roof Total 42 3117.1 100 100 4.3 Number of Measurements and Samples The number of measurements and samples for each survey unit was determined using the MARSSIM statistical hypothesis testing framework as outlined in the FSS Plan. The Sign Test is selected because background count rates of instruments to be used are equivalent to a small fraction of the applicable DCGLw. 17 Decision error probabilities for the Sign Test are set at a = 0.05 (Type I error) and 03 = 0.10 (Type II error) in accordance with the FSSP.
The Visual Sample Plan (VSP) software was used to determine the number of FSS measurements in the PPH. 18 When the Sign Test is selected, the VSP software uses 17 Background count rates for the LMI 44-116 detector, the instrument of choice for FSS surface beta activity measurements on structures, are in the range of 300 cpm or less for most materials. This is equivalent to about 2500 dpm/100-cm 2 (this assumes a detection efficiency of - 12%).
" The FSS Plan (Section 5.2.4) states that a qualified software product, such as Visual Sample Plan0 [PNL 2010], may be used in the survey design process.
16
Plum Brook Reactor Facility FSSR 3, Rev. 0 MARSSIM Equation 5-2 to calculate the number of measurements. Equation 5-2 is shown below:
N=l.2 (Zl-a +(ŽI-2 (Equation 1) 4[D A -0.5 where:
1.2 = adjustment factor to add 20% to the calculated number of samples, per a MARSSIM requirement to provide a margin for measurement sufficiency, N = Number of measurements or samples, a = the type I error probability, 03 = the type II error probability, Zl- = proportion of standard normal distribution < 1 - a (1.6449 for a =
0.05),
Zip = proportion of standard normal distribution < 1 - P3 (1.2816 for 0 - 0.1),
(D (A/a) = value of cumulative standard normal distribution over the interval -
00, A/a, A = the "relative shift", defined as the DCGL - the Lower Bound of the Gray Region (LBGR) and o = the standard deviation of residual contamination in the area to be surveyed (or a similar area). This may include the variation in measured "ambient" background plus the material background (for total surface beta measurements).
The MARSSIM module of VSP requires user inputs for the following parameters: a, [3, LBGR, the DCGLw and a. The numbers of measurements were calculated for PPH survey units using the parameters established in five survey designs. Table 7 summarizes the PPH survey design calculations and lists the values of the key VSP input parameters.
Table 7, PPH Survey Design Summary Design N
No. ) Survey Units Class DCGL (2) LBGR (2)
A (2)
(2 26 PH-I-17 through 1-1 23,713 22,807 906 302 3.0 11 29 PH-1-1 through 1-7 27
& PH-I-13 through 1
23,713 (3) 19,081 4,632 1,544 3.0 11 1-16 27 PH-1-8 through 1-12 1
10,067 (4) 5,435 4,362 1,544 3.0 11 (Room 4) 14 34 47 PH-1-30, Room 3 1
6.23 (5) 3.11 3.12 1.25 2.5 11 soil 68 Building Exterior 1
24,449 (6) 12,225 12,225 4,890 2.5 11 17
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 7 Notes:
- 1. The data reported in this table is taken from the Survey Design reports listed. They are maintained in the PBRF Document Control System.
- 2. Units are dpm/1 00-cm 2, except for Design 47, where the units are pCilg.
- 3. For these designs, the DCGLw for the survey design calculations, 23,713 dpm/1 00-cm 2, was obtained by adjusting the DCGL of 26,348 dpm/100-cm 2 published in TBD-07-001, by a factor of 22.5/25 to account for the allocation of 2.5 mrem for "insignificant" radionuclides.
- 4. The DCGLw for the survey design calculations, 10,067 dpm/100-cm 2, was obtained by adjusting the DCGL of 11,186 dpm/I00-cm 2 published in TBD-07-001, by a factor of 22.5/25 to account for the allocation of 2.5 mrem for "insignificant" radionuclides. See Table 3 notes for an explanation of the relatively low DCGL value for the Room 4 survey units.
- 5. The DCGL for soil sampling design, per Design 47 DCGL used the radionuclide mixture from PPH structure residual contamination reported in TBD-07-001 [PBRF 2007].
- 6. The DCGLw for the survey design calculations, 24,449 dpm/100-cm 2, was obtained by adjusting the DCGL of 27,166 dpm/100-cm 2 published in TBD-07-00 1, by a factor of 22.5/25 to account for the allocation of 2.5 mrem for "insignificant" radionuclides.
Selection of design input parameters followed guidance in the FSS Plan. The Plan states that "the LBGR is initially set at 0.5 times the DCGLw, but may be adjusted to obtain a value for the relative shift (A/a) between 1 and 3." It is seen in Table 7 that relative shift values of 2.5 and 3.0 were used in the final calculations for determining N.
The VSP software automatically performs an analysis to examine the sensitivity of N, the number of samples, to critical input parameter values. The following is an example obtained from the VSP report for survey unit PH-1-1. The sensitivity of N was explored by varying the following parameters: standard deviation, lower bound of gray region (as % of DCGL), beta, probability of mistakenly concluding that the survey unit mean concentration (p) is greater than the DCGL and alpha, probability of mistakenly concluding that the survey unit mean concentration is less than the DCGL. Table 8 summarizes this analysis. The region of interest is for a = 0.05 (required to be fixed), 13 = 0.10 (may be adjusted) and the LBGR at 70% to 90% of the DCGL. With the LBGR set to 90%, doubling a increases N from 14 to 34. With the LBGR set to 80%, doubling a increases N slightly (from 11 to 14). The sensitivity of N to an incorrect conclusion that the survey unit will pass (regulator's risk) is quite low; increasing a from 0.05 to 0.10 and 0.15 while holding 03 constant at 0.10 and a constant at 1544 dpm/ 100-cm2, shows that the number of measurements is 11 or fewer in all cases (when the LBGR is between 80 to 90% of the DCGL). These results show that N = 11 represents a conservative design.
Table 8, Sensitivity Analysis for PPH FSS Design Number of Samples DCGL = 23,713 (
a = 0.05 (2) a = 0.10 a = 0.15 a 3088 _
_cr a= 1544 a = 3088 a = 1544 a = 3088 r = 1544 LBGR = 90% (1'
- 4) f=0.05(5) 42 17 34 14 28 12
_ _=_0.10 34 14 26 11 21 9
___= 0.15 28 12 21 9
17 7
LBGR = 80%
0.05 17 14 14 11 12 9
_ _= 0.10 14 11 11 8
9 7
_ _=0.15 12 9
9 7
7 6
LBGR = 70%
0.05 14 13 11 11 10 9
_=0.10 11 11 9
8 7
7
_ _=0.15 10 9
7 7
6 6
18
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 8 Notes:
- 1. Units of DCGL, a and LBGR are dpmr/100-cm 2.
- 2. a = alpha, probability of mistakenly concluding that p < DCGL.
- 3. a = Standard Deviation.
- 4. LBGR = Lower Bound of Gray Region (as % of DCGL).
- 5. P3 = beta, probability of mistakenly concluding that p > DCGL.
Visual Sample Plan was also used to determine the grid size, the random starting location coordinates and to display the measurement locations on survey unit maps drawn to scale.
Refer to Appendix B for location coordinate tables and scale VSP maps showing measurement locations for each PPH survey unit.
The survey designs also specify scan survey coverage and action levels based on the MARSSIM classification listed in Table 4. If the scan sensitivity of the detectors used in Class 1 survey units is below the DCGLw, the number of measurements in each survey unit is determined solely by the Sign Test. If the scan sensitivity is not below the DCGLw, the number of measurements is increased as determined by the Elevated Measurement Comparison (EMC). As discussed in the next section, the scan sensitivities of instruments used in the FSS of the PPH are below the DCGLw, and no increase in the number of measurements above the value calculated using the Sign Test was required.
4.4 Instrumentation and Measurement Sensitivity Instruments to be used in the FSS of each survey unit are selected in each survey design.
Their detection sensitivities must be sufficient to meet the required action levels for the MARSSIM class of each survey unit. Minimum detection sensitivities for direct surface activity static and scan (alpha and beta) measurements are calculated using equations from Section 6.4 of the FSS Plan [NASA 2007]. The static MDC equation is:
3 + 3.29FBRt,(1 + t)
AMDCstatic A
'I (Equation 2) 100 where:
MDCstatic = Minimum Detectable Concentration (dpm/100-cm 2),
BR = Background Count Rate (cpm),
tb = Background Count Time (min),
ts = Sample Count Time (min),
A = Detector Open Area (cm 2) and Etot = Total Detection Efficiency (counts per disintegration). The total efficiency equals the product of Detector Efficiency, Ei and Surface Efficiency, Es.
The scan MDC equation is:
19
Plum Brook Reactor Facility FSSR 3, Rev. 0 d'.bJ57 6 0
- MCsc,
=
(Equation 3)
EiES..-* A 100 where:
MDCsca = Minimum Detectable Concentration (dpm/ 100-cm2),
d' = Index of sensitivity related to the detection decision error rate of the surveyor, from Table 6.5 of MARSSIM [USNRC 2000],
i = observation counting interval, detector width (cm) / scan speed (s),
bi = background counts per observation interval, E, = Detector Efficiency (counts per disintegration),
Es = Surface Efficiency, typically 25% for alpha and 50% for beta per ISO 7503-1, Table 2 [ISO 1988],
p = Surveyor efficiency (typically 50%) and A = Detector Open Area (cm2).
A summary of the a priori detection sensitivities of instruments used in the FSS of the PPH is provided in Table 9.
Table 9, Typical Detection Sensitivities of Field Instruments Detector MDCscaI Net cpm MDCsttc Detector Model Efficiency (dpm/1 00-cm 2)
Equivalent to (dpm/1 00-cm 2)
(c/d) (')
(2) (3)
DCGLw (2)
LMI 44-116 (4)(5 )
0.140 2,587 2,772 589 LMI 44-9 (6) 0.125 11,268 356 3,668 Table 9 Notes:
- 1. The detector efficiencies listed are total efficiency, i. e., E, = Ei + Es.
- 2. A priori scan sensitivities are calculated using Equation 3 and static sensitivities are calculated using Equation 2.
- 3. The scan MDC for the LMI 44-116 is reported in Design No. 27 for background count rate = 200 cpm; scan speed =15 cm/s and E, = 0.5. An efficiency correction factor =
0.8349 is applied to compensate for concrete roughness (the detector-to-surface distance is 0.5 in.).
- 4. The static MDC for the LMI 44-116 detector is reported in Design No. 27 for background count rate = 200 cpm, E, = 0.5 and the detector-to-surface distance = 0.5 in. (one minute count times are assumed for both the background and sample counts).
- 5. The scan MDC for the LMI 44-9 is obtained from Survey Design No. 27. The background count rate is 125 cpm with a scan speed of 4.4 cm/s and the detector in contact with the surface. Note that the scan speed is reduced to 2.2 cm/s when the 44-9 is used in Room 4 (PH-1 -8 through Ph 12) to achieve the necessary sensitivity (MDCSCB, = 7967 dpm/100-cm 2); as the DCGLw is only 10,067 dpm/100-cm 2.
20
Plum Brook Reactor Facility FSSR 3, Rev. 0
- 6. The static MDC for the LMI 44-9 listed in Table 9 is obtained from Survey Design No.
- 27. The background count rate is 125 cpm and the detector in contact with the surface (one minute count times are assumed for both the background and sample counts).
The scan investigation level for Class I survey units listed in Table 4 is the DCGLEMC, as specified in the FSS Plan Section 8.1. However, the scan investigation level is typically set at an instrument count rate corresponding to the DCGLw established in the survey design for each structure survey unit. For example, as seen in Table 9 above, the 44-116 detector count rate that corresponds to the DCGLW is 2772 net cpm. In practice, this is rounded downward to 2700 gcpm in typical PPH survey instructions. 19 This practice was established early in the FSS of PBRF structures and has been continued.
It is also noted the FSS Plan states that technicians are to respond to indications of increased count rates even though scan count rates may not be above the investigation level specified in survey instructions.
Scan sensitivities for detectors used for gamma scan surveys of soil are determined using the method referenced in the PBRF FSS Plan and described in NUREG-1507 [USNRC 1998].
Scan sensitivities for the Ludlum Model 44-10 Nal detectors used in FSS of soils at PBRF were developed in a technical basis document [PBRF 2009a]. The method is summarized and the key equations presented. The scan MDC is calculated using the following equations adapted from NUREG-1507 [USNRC 1998] for walkover gamma scanning with Nal detectors:
AM CR SURV
- d'-
bi 60*
(Equation 4)
MD CRs(E i
Conv
- MSo (Equation 5) where:
MDCsuRv = the minimum detectable count rate in cpm that can be reliably detected by the "surveyor",
d'= index of sensitivity, unitless (MARSSIM default value of 1.38 is assigned),
bi background counts observed in the interval i, 19Note that for the scan survey of PH Room 4 (PH-1-8 through PH-1-12) the scan investigation level for the 44-116 detector is reduced to 1177 ncpm to correspond with the lower DCGL (10,067 dpm/100-cm 2) for these survey units.
20 From FSS Plan Section 7.1.1: "Technicians will respond to indications of elevated areas while surveying. Upon detecting an increase in visual or audible response, the technician will reduce the scan speed or pause and attempt to isolate the elevated area. If the elevated activity is verified to exceed the established investigation level, the area is bounded (e.g., marked and measured to obtain an estimated affected surface area). Representative static measurements are obtained as determined by the FSS/Characterization Engineer. The collected data is documented on a Radiological Survey Form."
21
Plum Brook Reactor Facility FSSR 3, Rev. 0 i= observation interval (s),
p = surveyor efficiency, unitless (MARSSIM default value of 0.5 for walkover scans is assigned),
MDCsca = the scan MDC, here in units of pCi/g, Conv = instrument response conversion factor, units of cpm per jiR/hr and MSo = instrument response in units of tR/hr per pCi/g (determined empirically or with a shielding algorithm).
Site-specific parameter values for the MDCscan equation are obtained from the technical basis document [PBRF 2009a]. The instrument response factor for Cs-I 37 is 0.139 giR/hr per pCi/g, calculated using the MicroShield code. The most conservative instrument response conversion factor measured for detectors in the PBRF LMI 44-10 inventory is 232.39 cpm per jiR/hr for Cs-137.
Using these values, typical detection sensitivities of the instruments used in the FSS of soil survey units are provided in Table 10. Minimum detectable count rates and MDCscan values for 44-10 detectors operated in the Cs-I137 window vs. background count rates are shown in the table.
Table 10, Typical Detection Sensitivities of Field Instruments used for Soil Scans LMI 44-10 with Cs-137 Window (1)
M Ba kg ou d cp ) (2)
M DCR M DCý,ý.
Background (cpm (ncpm) (3)
(pCilg) 100 50 1.54 150 60 1.87 200 70 2.14 220 (3) 72 2.24 Table 10 Notes:
I. Ludlum Model 44-10 Nal detector with Model 2350-1 data logging scaler-rate meter setup to count in Cs-1 37 energy window. Data from Survey Design No. 47.
Scan speed = 0.5 m/s, detector to soil surface = 10 cm.
- 2. Specified as average background count rate.
- 3. The scan action level for soil scan surveys in PH-1-30 was set at 109 ncpm in Survey Design No. 47, for background count rates of 220 cpm (or less).
Survey instructions include directions to account for unusual measurement conditions.
Modified detection sensitivities may be applied taking into account adjustments in detector efficiency. Scan speeds may be reduced to ensure that required scan sensitivities are achieved.
The bases for adjustments due to non-standard conditions are provided in PBRF Technical 22
Plum Brook Reactor Facility FSSR 3, Rev. 0 Basis Documents.21 Examples of areas or locations in PPH survey units where special measurement conditions apply are shown in Exhibits 16 through 20 of Appendix A.
5.0 PPH Survey Results Results of the PPH FSS are presented in this section. This includes scan survey results for each survey unit and investigations prompted by scan surveys. Systematic-fixed measurement results for each survey unit and the results of comparison tests of survey unit maximum and average values with the DCGLw are reported. As discussed below, no statistical tests were required. Static measurements initiated by scan investigations, removable surface activity measurement results and QC measurements are presented. It is shown that levels of residual contamination have been reduced to levels that are ALARA. This section closes with a summary which concludes that applicable criteria for release of the PPH for unrestricted use are satisfied and all FSS Plan requirements are met.
5.1 Scan Surveys Scan survey results were reviewed to confirm that the scan coverage requirement (as % of survey unit area) was satisfied for all survey units. The results of QC replicate scan surveys were also reviewed to confirm that the minimum coverage requirement of 5% was satisfied.
Results of the PPH scan surveys are compiled in Table 11. The table shows that scan coverage requirements were satisfied for all survey units. The table also shows that investigations were performed in seven survey units (all PPH survey units are Class 1).
Table 11, Scan Survey Results Scan Survey Survey Investigation QC Replicate Scan Survey Unit Class Coverage (%) (
Request No.
Performed Coverage (%) (1) (2) (3)
PH-I-1 1
100 323/339 Yes 7.5%
PH 2 1
100 323/339 No 7.5%
PH 3 1
100 323/339 No 7.5%
PH 4 1
100 323/339 No 7.5%
PH 5 1
100 323/339 No 7.5%
PH 6 1
100 323/339 No 7.5%
PH 7 1
100 323/339 Yes 6.7%
PH 8 1
100 323/339 No 6.7%
PH 9 1
100 323/339 No 6.7%
PH 10 1
100 323/339 Yes 6.7%
PH 11 1
100 323/339 No 6.7%
PH 12 1
100 323/339 No 6.7%
PH 13 1
100 323/339 No 7.5%
PH 14 1
100 323/339 No 7.5%
PH 15 1
100 323/339 Yes 7.5%
PH 16 1
100 323/339 Yes 7.5%
2' The PBRF-TBD-07-004 [PBRF 2007a] presents efficiency correction factors developed for the LMI 44-116 detector.
The correction factors are presented as a function of detector-to-surface distance. Application of the factors requires empirical measurements of the effective detector-to-surface distance for areas with non-standard surface conditions as part of the survey unit inspection process.
23
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 11, Scan Survey Results Scan Survey Survey Investigation QC Replicate Scan Survey Unit Class Coverage (%) (1)
Request No.
Performed Coverage (%) (1) (2)(3)
PH 17 1
100 132 No 6.4%
PH 187"4 1
100 132 No 6.4%
PH 19 1
100 132 No 6.4%
PH 20 1
100 132 Yes 6.4%
PH 21 1
100 133 Yes 5.4%
PH 22 1
100 133 No 5.4%
PH 23 1
100 133 No 5.4%
PH 243 4 1
100 133 No 5.4%
PH 25 1
100 133 No 5.4%
PH 26 1
100 133 No 5.4%
PH 276 4 )
1 100 133 No 5.4%
PH 28 1
100 134 No 6.3%
PH 29 1
100 134 No 6.3%
PH-1-30 1
100 342 No 8.8%
PH-2-1 1
100 347/350 No 5.6%
PH-2-2 1
100 347/350 No 5.6%
PH-2-3 1
100 347/350 No 5.6%
PH-2-4 1
100 347/350 No 5.6%
PH-2-5 1
100 347/350 No 5.6%
PH-2-6 1
100 347/350 No 5.6%
PH-2-7 1
100 347/350 No 5.6%
PH-2-8 1
100 347/350 No 5.6%
PH-2-9 1
100 347/350 No 5.6%
PH-2-10 1
100 347/350 No 5.6%
PH-2-11 1
100 347/350 No 5.6%
PH-2-12 1
100 347/350 No 5.6%
Table 11 Notes:
- 1. Calculated scan % coverage values are rounded to the nearest 1/ 10th per cent. Values reported with the first decimal as 5, e. g., 5.5, are rounded downward.
- 2. The % scan coverage is given as the % of the area scanned in the initial survey.
- 3. Replicate QC scan results are reported for multiple survey units in most Survey Requests. The QC scan percentages are reported as % of the scanned area of the survey units combined. So the same % coverage value is assigned to all of the survey units reported in a Survey Request.
- 4. One hundred percent of the accessible surface area was scanned. A fraction of the surface area of the survey unit is inaccessible for scanning. In most such survey units, it is less than a few percent of the total surface area.
5.2 Fixed Measurements and Tests Results of the assessment of PPH FSS total surface beta measurements are presented in Table 12 (individual measurements in each survey unit are reported in Appendix B). The table presents the number of measurements, maximum, average and standard deviation for each 24
Plum Brook Reactor Facility FSSR 3, Rev. 0 survey unit. It compares the maximum activity measured in each survey unit to the DCGLw.22 It is demonstrated that all measured activity values are less than the DCGLw, thus all survey units meet the 25 mrem/y release criterion. The mean activity of each survey unit is also compared to the DCGLw, and as expected, are all less than the DCGLw. The average of 454 total surface beta measurements reported in the PPH release records is: 775 +/- 568 dpm/100-cm2 (one standard deviation) [PBRF 2011]. 23 Table 12, PPH Total Surface Beta Activity Measurement Summary and Test Results Test Result:
Standard Test Result:
Survey No. of Maximum Average (1)
Maximum <
(1)
Deviation Average <
Unit ID Measurements DCGLw (I)(2)
DCGLw PH-I-1 11 1487 Yes 859 319 Yes PH 2 11 1342 Yes 829 242 Yes PH 3 11 1895 Yes 1134 405 Yes PH 4 11 1217 Yes 946 152 Yes PH 5 11 3622 Yes 1307 908 Yes PH 6 11 4849 Yes 1925 1052 Yes PH 7 11 1118 Yes 661 360 Yes PH 8 12 1072 Yes 819 174 Yes PH 9 11 1797 Yes 917 353 Yes PH 10 11 972 Yes 724 126 Yes PH 11 11 928 Yes 687 168 Yes PH 12 11 1469 Yes 756 296 Yes PH 13 11 937 Yes 644 237 Yes PH 14 11 1190 Yes 835 189 Yes PH 15 11 1570 Yes 931 291 Yes PH 16 11 8100 Yes 1943 2065 Yes PH 17 11 627 Yes 378 173 Yes PH 18 11 789 Yes 606 127 Yes PH 19 11 1013 Yes 665 274 Yes PH 20 11 1183 Yes 778 289 Yes PH 21 11 1010 Yes 674 321 Yes PH 22 11 1050 Yes 590 299 Yes PH 23 11 861 Yes 521 270 Yes PH 24 11 975 Yes 729 156 Yes PH 25 11 972 Yes 700 133 Yes PH 26 12 1040 Yes 692 167 Yes PH 27 11 1070 Yes 685 252 Yes PH 28 11 1220 Yes 834 212 Yes PH 29 11 868 Yes 548 157 Yes PH-2-1 11 948 Yes 530 310 Yes PH-2-2 I1 1301 Yes 469 434 Yes 22 For comparison of survey unit maximum and average values to the DCGLw, the most restrictive PPH DCGLw, value, 10,067 dpm/100-cm 2, was used.
23 It is noted that in converting total surface activity measurements in cpm to dpm/100-cm 2, the detector background response from surface materials is not subtracted. As a result, the total surface activity measurement results are biased high.
25
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 12, PPH Total Surface Beta Activity Measurement Summary and Test Results Survey No. of Maximum Test Result:
Average Standard Test Result:
Unit ID Measurements (1)
Maximum <
(1)
Deviation Average <
Unit DCGLw (1)(2)
DCGLw PH-2-3 11 1842 Yes 894 418 Yes PH-2-4 11 2862 Yes 974 673 Yes PH-2-5 11 895 Yes 449 346 Yes PH-2-6 11 1170 Yes 809 218 Yes PH-2-7 11 2784 Yes 796 724 Yes PH-2-8 11 1125 Yes 593 229 Yes PH-2-9 11 732 Yes 360 164 Yes PH-2-10 12 809 Yes 471 335 Yes PH-2-11 11 948 Yes 509 316 Yes PH-2-12 11 1270 Yes 650 342 Yes Table 12 Notes:
- 1. The units for: maximum, average and standard deviation are dpm/1 00-cm2.
- 2. Standard deviations of the measurements in each survey unit are reported for comparison to the values used in the survey design. In most PPH structural survey units, values of o obtained from the FSS measurements are much less than values used in the survey designs, as reported in Table
- 7. This confirms that the survey designs for the PPH were conservative.
- 3. In the FSS design calculation for survey units developed using VSP; "extra" fixed measurement locations are sometimes added when "fitting" the calculated grid size onto the survey unit layout.
5.3 Additional Measurements Additional measurements were performed as a result of investigations initiated during scan surveys of the PPH survey units. The investigations and the results of the investigative static measurements are summarized in Table 13 (investigative measurements are designated as IM-x). It is noted that most of the investigations were initiated when technicians observed increased count rates during scans as opposed to observing count rates above action levels (scan survey action levels in survey instructions are discussed in Section 4.0). As shown in the table, scan investigation-action levels were exceeded in some cases. Also, in one case an investigative static measurement exceed the DCGLw.
Table 13, PPH Investigative Static Measurements Static Size of Survey SR Measurement Elevated Measurement DCGLw Unit (dpm/100-cm 2)
Area (cm 2)
ID PH-1-1 323 13,300 100 IM-1 23,713 PH-1-1 323 15,000 100 IM-2 23,713 PH-1-1 323 21,100 100 IM-3 23,713 PH-1-7 322 7,400 100 IM-1 23,713 PH-1-7 322 7,990 100 IM-2 23,713 PH-I-10 322 1,707 100 IM-1 10,067 PH-I-10 322 2,473 100 IM-2 10,067 PH-I-15 133 20,700 100 IM-1 23,713 PH-1-16 133 13,100 100 IM-I 23,713 PH-1-16 133 25,000 100 IM-2 23,713 26
Plum Brook Reactor Facility FSSR 3, Rev. 1 Table 13, PPH Investigative Static Measurements PH-1-20 132 16,294 800 IM-1 23,713 PH-1-21 133 5,520 12(')
IM-1 23,713 Table 13 Note:
- 1.
Measurement taken with LMI 44-9 detector.
As a result of the investigative static measurement in Survey Unit PH-I-16 which exceeded the DCGL, the elevated measurement comparison (EMC) and elevated measurement test (EMT) were performed. In accordance with the FSS Plan, Section 8.3, the DCGLEMC is calculated as the product of the Area Factor (AF) and the DCGLw. The EMT is defined by the following unity rule equation:
9 (average concentration in elevated area) - t
-+
- <1.0
[Equation 6]
DCGLW (AF) (DCGLw)
Where: 6 is the average residual activity concentration in the survey unit.
If more than one elevated area is found in a survey unit, the second term in Equation 6 is calculated for each and summed with the first term to perform the unity rule calculation for the EMT. Results of the DCGLEMc and EMT calculations are summarized:
" From Table 13, the size of the elevated area is 100 cm2; per the FSS Plan Table 3-5, the area factor for elevated areas of size < 0.25 m2 is 40.2.
- From Table 12, the average residual activity concentration, 6, in Survey Unit PH-I-16 is 1943 dpm/100-cm2.
2
- From Table 7, the applicable DCGLw is 23,713 dpm/100-cm.
- The DCGLEMC is calculated to be 9.53E+05 dpm/1 00-cm 2 (40.2 x 23,713 dpm/100-cm2); this is much greater than 25,000 dpm/100-cm 2, the measured activity in the elevated area. Thus the elevated measurement comparison is easily satisfied.
- Calculating the unity value using Equation 6 yields:
1943 + (25,000 -1943) = 0. 11, which is much less than 1.0.
23,713 (40.2) (23,713)
Removable surface activity measurements were taken at each systematic measurement and investigative measurement location in structural survey units. The Plan requires that removable surface activity in each survey unit be less than 10% of the DCGLw. Removable surface activity is measured by counting 100 cm2 smear samples for beta and alpha activity.24 Smear results were below 10% of the DCGLw in all PPH survey units and less than counting 24 Smears are counted in the PBRF Counting Laboratory on automated sample changer proportional counters. Two such counters are available for this purpose: Tennelec Model LB-5 100 and Tennelec Model 5X-LB.
27
Plum Brook Reactor Facility FSSR 3, Rev. 0 instrument MDA in all except one PPH survey unit. The measurement results in excess of MDA are shown in Table 14.
Table 14, Removable Surface Activity Measurements Survey Measurement Beta Alpha Activity Activity Unit ID ID (3)(4)
(3)(4)
PH-1-16 IM-1 (2) 25.97
< MDA PH-1-16 IM-2 (2) 60.09
< MDA Table 14 Notes:
- 1. Units are dpm/1 00-cm 2.
- 2. IM denotes investigative measurement.
- 3. Maximum removable surface activity measured in the survey unit.
- 4. The beta MDA for these measurements was 16.55 dpm. The alpha MDA for these measurements was 8.33 dpm.
5.4 Soil Survey Unit Results One soil survey unit was established for the PPH FSS: Survey Unit PH-1-30 Room 3 Soil. It was established to cover soil exposed by removal of the contaminated concrete floor of Room 3, one of the three PPH pump rooms. As shown in Table 11, Scan Survey Results, 100 % of the exposed soil area was scanned (by Nal detectors set up to count in the Cs-137 energy window). No elevated areas were observed and no investigations were performed. Surface soil samples were collected from the survey unit and analyzed by gamma spectroscopy by the PBRF laboratory. The results are summarized in Table 15. All results are < MDA.
Table 15, PPH Soil Survey Unit Sample Results Survey Survey No. of Samples Maximum Concentration (pCi/g) (2 Unit ID Design (1)
Cs-137 I
< MDA
< MDA See Note Table 15 Notes:
- 1. The No. of samples is systematic measurements (samples) per survey design.
- 2. The maximum concentrations shown are from systematic samples. No investigative samples were collected.
Cs-137 activity ratio is 0.499 assuming the same mix as in the PPH Room 3 structure per TBD-07-001 [PBRF 2007]. Hence the maximum Sr-90 concentration is < 1/2 the maximum Cs-137 MDA of7.71E-02 pCi/g.
5.5 QC Measurements Per FSS Plan requirements, QC replicate measurements were taken for at least 5% of the PPH measurements. This included scan surveys, systematic total surface activity measurements and soil samples. Scan QC survey results are shown in Table 11 wherein the 5% scan QC coverage is confirmed. These surveys confirmed the results of the original scan surveys of the areas covered. No QC scan surveys identified areas of elevated activity.
28
Plum Brook Reactor Facility FSSR 3, Rev. 0 Replicate total surface activity measurements were performed at selected measurement locations including systematic and investigative measurements. The 5 % requirement is satisfied in that 31 QC measurements were reported; this represents 6.7 % of 466 systematic and investigative measurements. The measurement results for the 31 surface activity original and QC replicate measurement data pairs are shown in Table 16.
Table 16, PPH Total Surface Activity QC Measurements Survey Measurement Net Activity QC Replicate (dpm/l100 CM)
RPD Unit Location No.
cm 2) (1)
(dpmli00 PH-I-11 SM-7 362 566 43.97 PH-1-29 SM-5 493 362 30.64 PH-I-1I SM-5 566 650 13.82 PH-1-17 SM-6 627 968 42.76 PH-1-22 SM-2 646 550 16.05 PH-I-11 SM-9 651 923 34.56 PH-I-11 SM-8 658 748 12.80 PH-1-24 SM-2 671 732 8.70 PH-2-4 SM-2 678 902 28.35 PH-1-23 SM-5 759 530 35.53 PH-1-18 SM-7 789 601 27.05 PH-I-1I SM-6 809 713 12.61 PH-1-14 SM-4 895 804 10.71 PH-2-4 SM-6 914 915 0.11 PH-1-19 SM-5 915 1066 15.24 PH-2-4 SM-4 974 810 18.39 PH-2-4 SM-1 980 1418 36.53 PH-1-28 SM-3 987 812 19.46 PH-2-4 SM-5 1020 784 26.16 PH-1-26 SM-10 1040 966 7.38 PH-2-4 SM-7 1145 1216 6.01 PH-I-14 SM-5 1190 1220 2.49 PH-1-16 SM-1 1520 1410 7.51 PH-1-16 SM-2 1980 2020 2.00 PH-2-4 SM-3 2862 2190 26.60 PH-1-21 IM-i 5520 4680 16.47 PH-1-7 IM-2 7,990 9,224 14.34 PH-I-1 IM-1 13,300 12,340 7.49 PH-1-20 IM-1 16,294 17,283 5.89 PH-I-15 IM-1 20,700 20,600 0.48 PH-I-16 IM-2 25,000 24,200 3.25 Table 16 Notes:
- 1. Table data is sorted by increasing net activity.
29
Plum Brook Reactor Facility FSSR 3, Rev. 0 The FSS Plan (Section 12.7) specifies that the relative percent difference (RPD) between original and replicate measurements must be within 20% [NASA 2007]. Ten of the 31 measurement pairs were above the 20% criterion. Each measurement pair failing to meet the 20% criterion was individually investigated and resolved in accordance with FSS Plan requirements and implementing procedures.25 It is found that all the measurements which failed the 20% criterion were low activity measurements (below 1000 dpm/100-cm2). Results of the replicate QC measurement evaluation are summarized in Table 17. The table shows that the average RPD is inversely proportional to the magnitude of residual surface contamination levels.
Table 17, RPD Evaluation of Replicate QC Surface Activity Measurements No. of Average Average QC Rep Average Activity Range o)(2)
Measurement Original (e)
- Pairs Activity l Activity ()
RPD (%) (3)
< 1000 18 743 782 22.6 1000 to 10000 9
2696 2634 12.1
> 10,000 4
18824 18606 4.3 Table 17 Notes:
- 1. Units are 100 dpm/ 100-cm2.
- 2. The activity range is specified for the original measurements.
- 3. Calculated as the average of individual RPD values within the stated activity ranges.
A replicate QC sample was collected from the PPH soil survey unit (PH-1-30) and analyzed.
Results for all analytes in both the original and QC samples are <MDA. The PH-1-30 Release Record reported that the results were evaluated in accordance with Section 12.7.2 of the FSS Plan and that positive agreement the original and QC sample was indicated.
5.6 ALARA Evaluation It is shown that residual contamination in the PPH has been reduced to levels that are ALARA, using a method acceptable to the NRC. The NRC guidance on determining that residual contamination levels are ALARA includes the following:
"In light of the conservatism in the building surface and surface soil generic screening levels developed by the NRC, NRC staff presumes, absent information to the contrary, that licensees who remediate building surfaces or soil to the generic screening levels do not need to provide analyses to demonstrate that these screening levels are 25 When the acceptance criterion is not met, an investigation is performed to determine the cause and corrective actions.
The investigation may include repetition of the replicate QC measurement or other actions determined by the FSS/Characterization Supervisor. If upon repetition, the RPD criterion is still not satisfied, the result may be accepted if the original and QC replicate measurement are in agreement that both are below the DCGLw for the survey unit, the FSS/Characterization Supervisor reviews the investigation and concurs that the measurement is acceptable and the results of the investigation are documented in the Survey Request Summary and Close-out (Procedure CS-0 1, Survey Methodology to Support PBRF License Termination).
30
Plum Brook Reactor Facility FSSR 3, Rev. 0 ALARA. In addition, if residual radioactivity cannot be detected, it may be presumed that it had been reduced to levels that are ALARA. Therefore the licensee may not need to conduct an explicit analysis to meet the ALARA requirement." 26 Screening level values published by the NRC for the mix of radionuclides in structural surface residual contamination potentially present in the PPH are shown in Table 18. Since individual radionuclide activity concentrations are not measured in the FSS of structures, a direct comparison of residual contamination levels to individual radionuclide screening level values is not possible. A comparison can be made by converting the nuclide-specific screening level values to an appropriate gross activity DCGL. This is accomplished using activity fractions used in development of the PPH gross activity DCGL for Room 4, the PPH Heat Exchanger Room. A screening level value that is equivalent to the gross activity DCGL was calculated using the equations in Section 3.6 of the FSS Plan.27 The activity fractions listed in Table 3 (also shown in Table 18) were used in the calculation. The screening level equivalent DCGL 2
for the PPH Room 4 is calculated to be 2103 dpm/100-cm2.
The average total surface beta activity measured in the FSS of the PPH is 775 +/- 568 dpm/100-cm (one standard deviation). The upper limit of the 95t /confidence interval of this mean 2 28 value is 828 dpm/100-cm.
This value is below the screening level gross activity DCGL of 2103 dpm/I00-cm2. From this comparison, it is concluded that the ALARA criterion is satisfied.
Table 18, Screening Level Values for PPH and Radionuclide Activity Fractions Screening Level Value PPH Activity Radionuclide (dpm/100-cm 2)
Fraction (%) (1)
H-3 1.2 E+08 42.91 Co-60 7.1E+03 (2) 9.56 Sr-90 8.7E+03 (2) 2.56 1-129 3.5E+04121 22.55 Cs-137 2.8E+04 (2) 18.92 Eu-154 1.2E+04(3) 0 U-234 9.1E+01 (3) 3.34 U-235 9.8E+01131 0.16 Table 18 Notes.
- 1. Activity fractions used to develop the DCGLw for PPH Room 4.
- 2. Values from NUREG-1757 Vol. 2, Table H.1 [USNRC 2006].
- 3. Values from NUREG/CR-5512, Vol. 3, Table 5.19 [SNL 1999]. These are 90th percentile values of residual surface activity corresponding to 25 mrem/y to a future building occupant.
26 This guidance was initially published in Draft Regulatory Guide DG-4006, but has been reissued in NUREG-1757 Volume 2, Appendix N.
27 The equivalent screening level gross activity DCGL is calculated using an EXCEL template [PBRF 2011]. This template incorporates the equations in section 5.3 of the FSS Plan [NASA 2007].
28 The upper limit of the confidence interval, 95th percentile value, is calculated as: UL = mean + 1.96 o/'/n, where n 454 measurements.
31
Plum Brook Reactor Facility FSSR 3, Rev. 0 Table 19, NRC Soil Screening Level ALARA Comparison NRC Screening Maximum Measured Radionuclide Level (pCi/g) (1)
Concentration (pCi/g)
Co-60 3.8
< MDA(2)
Cs-137 11
< MDA (3)
Sr-90 1.7 See Note (4)
Table 19 Notes:
- 1. Values from NUREG-1757 Vol. 2, Table H.2 [USNRC 2006].
- 4. Maximum Sr-90 concentration inferred from the maximum Cs-137 MDA and Sr-90: Cs-137 activity ratio of 0.499. The maximum inferred Sr-90 concentration so obtained is < 0.045 pCi/g.
5.7 Comparison with EPA Trigger Levels The PBRF license termination process includes a review of residual contamination levels in groundwater and soil, as applicable, in accordance with the October 2002 Memorandum of Understanding (MOU) between the US NRC and the US Environmental Protection Agency (EPA) [USEPA 2002]. Concentrations of individual radionuclides, identified as "trigger levels" for further review and consultation between the agencies, are published in the MOU.
This comparison is shown in Table 20. The table shows that the measured soil activity concentrations are well below EPA trigger levels. It is noted that groundwater is not within the scope of the PPH FSS.
Table 20, Comparison of Soil Sample Results with EPA Trigger Levels Radionuclide EPA Trigger Maximum Measured Level (pCi/g)
Concentration (pCi/g)
Co-60 4
< MDA(1)
Cs-137 4) 6
< MDA (2)
Sr-90 (4) 23 See Note (3)
Table 20 Notes:
- 3. Maximum Sr-90 concentration is < 0.045 pCi/g; inferred from the maximum Cs-137 MDA and SR-90: Cs-137 activity ratio of 0.499.
- 4.
Specified in the MOU as including daughter activity [USEPA 2002].
32
Plum Brook Reactor Facility FSSR 3, Rev. 0 5.8 Conclusions The results presented above demonstrate that the PPH satisfies all FSS Plan commitments and meets the release criteria in 10CFR20 Subpart E. The principal conclusions are:
- Scan surveys were performed in 100 % of the accessible surfaces of all 42 PPH survey units - all were Class 1.
- Residual surface contamination levels requiring investigation were observed in seven survey units. A localized area with activity above the DCGLw was measured in one survey unit. The EMC and EMT were performed and were successful.
- All randomly selected (systematic with random start) fixed total surface activity measurements are less than the applicable DCGLw.
- All survey unit mean fixed measurement results (total surface beta. activity) are below the DCGLw, hence no statistical tests were required.
" All removable surface activity measurements are less than 10% of the DCGLW.
" Residual surface and soil activity concentration measurement results are shown to be less than NRC screening level values - demonstrating that the ALARA criterion is satisfied.
- Only minor changes from what was proposed in the FSS Plan were made - the PPH was divided into 42 survey units, whereas the FSS Plan had not shown a survey unit breakdown.
- There was one change from initial assumptions (in the FSS Plan) regarding the extent of residual activity in the PPH. One area of potentially contaminated soil was identified underneath the PPH in Room 3; this was not identified in the FSS Plan. No reclassification of survey units was required as a result of FSS measurements and investigations.
6.0 References GTS 1989 GTS Duratek Radiological Engineering and Field Services, Kingston, TN, Plum Brook Confirmatory Survey, November 1998.
ISO 1988 International Organization for Standardization, Evaluation of Surface Contamination, Part 1: Beta Emitters and Alpha Emitters, ISO-7503-1, 1988.
MWH 2003 MWH Constructors, Inc., Characterization Package Cl134-201C1 Primary Pump House Structure, Prepared for US Army Corps of Engineers Under Contract DACW-27-97-0015, October 2003.
NASA 2006 NASA Safety and Mission Assurance Directorate, Plum Brook Reactor Facility, Decommissioning Project Quality Assurance Plan, QA-01, Revision 2, February 2006.
NASA 2007 NASA Safety and Mission Assurance Directorate, Final Status Survey Plan for the Plum Brook Reactor Facility, Revision 1, February 2007.
33
Plum Brook Reactor Facility FSSR 3, Rev. 0 NASA 2008 PBRF 2005 PBRF 2007 PBRF 2007a PBRF 2009 PBRF 2009a PBRF 2011 PNL 2010 SNL 1999 TELE 1987 NASA Safety and Mission Assurance Directorate, Decommissioning Plan for the Plum Brook Reactor Facility, Revision 6, July 2008.
Plum Brook Reactor Facility, MWH Constructors, Inc. Survey Package Cl 134 201C1, Primary Pump House (1134) Structural Surfaces Rooms 1-6, August 2005.
Plum Brook Reactor Facility Technical Basis Document, Adjusted Gross DCGLsfor Structural Surfaces, PBRF-TBD-07-00 1, June 2007.
Plum Brook Reactor Facility Technical Basis Document, Efficiency Correction Factor, PBRF-TBD-07-004, November 2007.
Plum Brook Reactor Facility, Memorandum to Project File, J. L. Crooks, Don Young, Final FSS Report Background -NASA Plum Brook Reactor Facility Primary Pump House (1134), December 08, 2009.
Plum Brook Reactor Facility Technical Basis Document, 44-10 NaI Detector MDCscan Values for Various Survey Conditions, PBRF-TBD-09-002, June 2009.
Plum Brook Reactor Facility Decommissioning Project Office, Memorandum to Project File, Engineering Record for Final Status Survey Report Calculation - PPH Update. August 4, 2011.
Battelle Pacific Northwest Laboratories (PNL), Visual sample Plan, Version 5.9, 2010.
Sandia National Laboratories (SNL), for US Nuclear Regulatory Commission, Residual Radioactive Contamination From Decommissioning, Parameter Analysis, NUREG/CR-5512, Vol.3, Oct. 1999.
Teledyne Isotopes, An Evaluation of the Plum Brook Reactor Facility and Documentation of Existing Conditions, Prepared for NASA Lewis Research Center, December 1987.
Memorandum of Understanding, US Environmental Protection Agency and US Nuclear Regulatory Commission, Consultation and Finality on Decommissioning and Decontamination of Contaminated Sites, October 9, 2002.
US Nuclear Regulatory Commission, Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants and Field Conditions, NUREG-1507, Rev. 1, June 1998.
US Nuclear Regulatory Commission, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), NUREG-1575, Rev. 1, August 2000.
US Nuclear Regulatory Commission, Consolidated Decommissioning Guidance, Characterization, Survey and Determination of Radiological Criteria, NUREG 1757, Vol. 2, Rev. 1, September 2006.
USEPA 2002 USNRC 1998 USNRC 2000 USNRC 2006 34
Plum Brook Reactor Facility FSSR 3, Rev. 0 7.0 Appendices Appendix A - Exhibits Appendix B - Survey Unit Maps and Tables Showing Measurement Locations and Results 35
Final Status Survey Report 3 Primary Pump House (Building 1134)
Revision 0 Appendix A Exhibits
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 2 of 22 List of Exhibits Exhibit 1, Current Views of PPH Exterior.......................................................................................
3 Exhibit 2, PPH Construction Photo...................................................................................................
4 Exhibit 3, PPH First Floor Layout Showing Survey Units...............................................................
5 Exhibit 4, Pum p Room V iew s..........................................................................................................
6 Exhibit 5, Pump Room Views, Continued.........................................................................................
7 Exhibit 6, Room 3 and Soil Survey Unit............................................................................................
8 Exhibit 7, Room 4 - Heat Exchanger Room.....................................................................................
9 Exhibit 8, Room 4 - Heat Exchanger Room, Continued.................................................................
10 Exhibit 9, Room 5 - D egassifier Room...............................................................................................
11 Exhibit 10, Room 6 - Bypass Deionizer Room................................................................................
12 Exhibit 11, R oom 7 V iew s...................................................................................................................
13 Exhibit 12, Room 7 Views, Continued...........................................................................................
14 Exhibit 13, R oom 8 V iew s...................................................................................................................
15 Exhibit 14, Room 8 Views, Continued...........................................................................................
16 Exhibit 15, PPH Sum p V iew s..........................................................................................................
17 Exhibit 16, Unusual Condition Measurement Areas (UCMs)........................................................
18 Exhibit 17, Unusual Condition Measurement Areas (UCMs), Continued.......................................
19 Exhibit 18, Surface Measurement Test Areas (SMTAs)..................................................................
20 Exhibit 19, Examples of Other Special Measurement Conditions.................................................
21 Exhibit 20, Examples of Other Special Measurement Conditions, Continued...............................
22
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 3 of 22 Exhibit 1, Current Views of PPH Exterior (view from northeast)
(view from south)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 4 of 22 Exhibit 2, PPH Construction Photo (Grade Level View Looking Southwest)
I
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 5 of 22 Exhibit 3, PPH First Floor Layout Showing Survey Units F Lj "
U UR
.OM I
..I L7U ROOM 7 F--
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ROOM 1 ROOM 2 ROOM 3 ROOM 5 ROOM 4 ROOM 6 ROOM 8 i
Survey Description Survey Description Unit Unit PH-I-1 Room 1 - Floor, Ceiling, Platform, PH 16 Room 6 - Walls Hatchways PH 2 Room 1 - Walls PH 17 Room 7 & 8 - Floor Section I PH 3 Room 2 - Floor, Ceiling, Platform, PH 18 Room 7 & 8 - Floor Section 2 Hatchways PH 4 Room 2 - Walls PH 19 Room 7 & 8 - Floor Section 3 PH 5 Room 3 - Floor, Ceiling, Platform, PH 20 Room 8 Sump Hatchways PH 6 Room 3 - Walls PH 21 Room 7 & 8 - Wall Section 1 & West Stairs PH 7 Room 4 - Floor Section 1 PH 22 Room 7 & 8 - Wall Section 2 PH 8 Room 4 - Floor Section 2 PH 23 Room 7 & 8 - Wall Section 3 & East Stairs PH 9 Room 4 - West & North Walls PH 24 Room 7 & 8 - Wall Section 4 PH 10 Room 4-East & South Walls & Wall PH 25 Room 7 & 8 - Wall Section 5 penetrations PH 11 Room 4 - West Ceiling & Hatchway PH 26 Room 7 & 8 - Wall Section 6 PH 12 Room 4 - East Ceiling & Hatchway PH 27 Room 7 & 8 - Platforms PH 13 Room 5 - Floor, Ceiling, & Hatchway PH 28 Room 7 & 8 - Ceiling Section 1 PH 14 Room 5 - Walls PH 29 Room 7 & 8-Ceiling Section 2 PH 15 Room 6 - Floor, Ceiling, & Hatchway PH-1-30 Room 3 - Soil
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 6 of 22 Exhibit 4, Pump Room Views (Room 1 floor looking east)
(Room 2 upper walls, showing valve pedestal)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 7 of 22 Exhibit 5, Pump Room Views, Continued (Room 2 floor, showing cored areas)
(Room 2, wall and ceiling)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 8 of 22 Exhibit 6, Room 3 and Soil Survey Unit (walls and ceiling and floor remnant)
(close-up of soil surface beneath former floor)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 9 of 22 Exhibit 7, Room 4 - Heat Exchanger Room (Floor looking west to east)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 10 of 22 Exhibit 8, Room 4 - Heat Exchanger Room, Continued (Room 4 showing main PCW piping egress in southwest comer)
(grouted PCW piping entrance/exit from PPH inside sheath below Room 4 floor)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 11 of 22 Exhibit 9, Room 5 - Degassifier Room (View of Floor showing sump and floor corings)
(NW Wall showing pipe penetrations, remediated concrete and ledge)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 12 of 22 Exhibit 10, Room 6 - Bypass Deionizer Room (view of floor showing holes bored to remove anchors)
(West Wall showing concrete remediated around penetrations)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 13 of 22 Exhibit 11, Room 7 Views (Room 7 looking east)
(West entrance from Reactor Building and stairs to Pump Room motor platforms)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 14 of 22 Exhibit 12, Room 7 Views, Continued (pump motor platform galley above Room 7 looking east)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 15 of 22 Exhibit 13, Room 8 Views (Floor and lower walls looking south)
Sumn access at south end of Room R)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 16 of 22 Exhibit 14, Room 8 Views, Continued (ceiling central area looking south)
(Room 7/8 ceiling north east comer of PPH looking north)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 17 of 22 Exhibit 15, PPH Sump Views (View of Sump from Room 8 Floor)
(view from sump first level to the bottom)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 18 of 22 Exhibit 16, Unusual Condition Measurement Areas (UCMs)
(Remediated area in Room 4 wall concrete showing rebar)
(through-wall penetrations from Room 7 to Pump Room)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 19 of 22 Exhibit 17, Unusual Condition Measurement Areas (UCMs), Continued (typical anchor plate)
(aggressively decontaminated concrete)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 20 of 22 Exhibit 18, Surface Measurement Test Areas (SMTAs)
(Scabbled concrete in Room 7 floor)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 21 of 22 Exhibit 19, Examples of Other Special Measurement Conditions (grout-filled pipe in Room 4 floor)
(irregular surface from core drilling to remove contaminated pipe in Room 4 Wall)
Plum Brook Reactor Facility FSSR, Attachment 11 Appendix A, Rev. 0, Page 22 of 22 Exhibit 20, Examples of Other Special Measurement Conditions, Continued (eight-inch core bores in Room 8 floor)
(penetration in Room 3 ceiling showing rough edges and rebar)