NRC Decommissioning Lessons Learned

Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-01 Facility Type: Reactors Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning Licensing, Facilitates Decommissioning WorkSubject: Licensees should develop a unique radionuclide profile for each of the major types of materials expected to rema

 remediation.

Discussion: A unique radionuclide profile must be developed for each of the major types of materials expected to remain o

A commercial light-water power reactor facility will likely require profiles for contaminated soil or sediments, s

materials, and activated materials. The licensee must consider that activation products in steels and concreteconstituents and operational history. Concrete will also differ between facilities because of different trace elem

generic list cannot be developed that would be applicable to all power reactor licensees and types of contami

radioactive decay has been considered to the time when final status surveys (FSSes) will be conducted, a sebe developed for surface contamination and for activated materials. The licensee should confirm, by using chand historical assessments, that the radionuclide lists developed are applicable to the facility and appropriate 

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-02 Facility Type: Reactors, Material Facilities Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning LicensingSubject: Licensees should follow the guidance in NUREG-1757, Volume 2, Revision 1, regarding deselecting radionuclide

evaluation in demonstrating compliance during license termination.

Discussion: Guidance in Section 3.3 of NUREG-1757, Volume 2, Revision 1, states, “Once a licensee has demonstrated 

exposure pathways are insignificant, then (a) the dose from the insignificant radionuclides and pathways mus

demonstrating compliance, but (b) the radionuclides and pathways may be eliminated from further detailed ev

during characterization of a facility, if a profile contains radionuclides that collectively contribute less than 10 % those nuclides may be deselected from the list. Since derived concentration guideline levels are developed to radiological criteria for license termination (0.25 mSv/y (25 mrem/y)) total effective dose equivalent to the avecritical group and ALARA, for unrestricted release in 10 CFR 20.1402), those radionuclides that collectively c

0.025 mSv/y (2.5 mrem/y) may be considered insignificant, given all appropriate exposure scenarios and path

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-03 Facility Type: Reactors Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning WorkSubject: Licensees should follow the guidance in NUREG-1757, Volume 2, Revision 1, when choosing acceptable method

embedded piping and buried piping.

Discussion: There are several methods that have been used to characterize the residual activity within embedded pipe, a

be used for buried piping, as well. By definition, “embedded piping” is piping (e.g., part of a plant system) thaand encased in concrete floors and walls, while “buried piping” is piping (e.g., culvert) that is buried in soils. T

each method should address the following nine issues:a) radionuclides of interest and chosen surrogate,b) levels and distribution of contamination,c) internal surface condition of the piping,d) internal residues and sediments and their radiation attenuation properties,e) removable and fixed surface contamination,f) instrument sensitivity and related scan and fixed minimum detectable concentrations,g) piping geometry and presence of internally inaccessible areas/sections,h) instrument calibration, andi) data quality objectivesAn industry study (Cline, J. E., “Embedded Pipe Dose Calculation Method,” Electric Power Research Institute November, 2000) evaluated several techniques for measuring the radiological contamination on the inside of Measurement techniques included pipe crawlers, gamma-ray scanners, dose rate measurements with dose-tscraping samples with radiochemical analyses, and smear samples with radiochemical analyses.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-04 Facility Type: Reactors, Material Facilities Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning LicensingSubject: Licensees should follow the guidance in NUREG-1757, Volume 2, Revision 1, when developing input distribution 

for soil or concrete when using site-specific dose modeling codes

Discussion: Kd values for input into site-specific dose modeling codes may be determined by the following:

Use sensitivity analyses, which include an appropriate range of Kd values, to identify the importance of the Kd assessment and how the change in Kd impacts the dose (i.e., how dose changes as Kd increases or decreasvalues that bound the sensitivity analysis may be obtained from (a) the literature, (b) the default distribution in 

default distribution in the probabilistic code of RESRAD (please refer to the “Basis” section that follows). Usin

sensitivity analysis, choose a conservative Kd value, depending on how it affects the dose (e.g., if higher Kd v

larger dose, an input Kd value should be selected from the upper quartile of the distribution, or if lower Kd val

dose, an input Kd value should be selected from the lower quartile of the distribution). For those isotopes whehave a significant impact on the dose assessment (i.e., Kd is not a sensitive parameter), the median value wi

acceptable input parameter. If the licensee feels that the Kd value is overly conservative, the licensee is enco

site-specific Kd determination, so that the dose assessment reflects true site conditions.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-05 Facility Type: Reactors, Material Facilities Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning LicensingSubject: Licensees can use illustrative examples to demonstrate appropriate selection of survey instrumentationDiscussion: Licensees can define the data quality objective process and acceptance criteria using examples that demons

selection of radiation survey instrumentation for the expected types of final status survey surface conditions a

forming the basis of the derived concentration guidelines. For example, the selection of instrumentation may of surfaces with similar features and expected instrument responses over these surfaces. For each of the defsurvey instrumentation and methods presented in the license termination plan (e.g., soil scanning, surface sc

fixed measurements), the licensee should provide the derivation of scan and fixed minimum detectable conce

derivation of the MDCs must take into account instrument efficiencies (surface and detector), scan rates and 

surfaces, surveyor efficiency, and minimum detectable count rate, using the guidance in Multi-Agency RadiatInvestigation Manual and NUREG–1507, “Minimum Detectable Concentrations with Typical Radiation Survey 

Various Contaminants and Field Conditions.”

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-06 Facility Type: Reactors, Material Facilities Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning LicensingSubject: Licensees are not required to use characterization data to support the initial classification of Class 1 areasDiscussion: Areas classified as Class 1 do not require characterization data to support that classification.

Note that characterization data are needed to support decommissioning activities for all areas including: • Determination of radionuclide distribution profiles and identification of surrogate radionuclides• Dose modeling and development of derived concentration guideline levels• Final status survey design and instrument selection• Structuring the data quality objectives• Assessment of spatial variability of radioactive contaminants on building surfaces and in surface and subsu• Assessment of whether ground water is impacted, using the results of the surface and subsurface soil cha• Initially defining and changing the boundaries of Class 1 survey units with bordering and adjacent survey u• Reclassification of survey units (using guidance in the Multi-Agency Radiation Survey and Site Investigatio

A.1 of Appendix A of NUREG-1757, Volume 2, Revision 1)

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-07 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Requirements for calibration of instrument/detector combinations used for assessing residual radioactive materiaDiscussion: Industry guidance for the calibration of instrument/detector combinations used for assessing residual radioac

contamination levels requires calibrations be performed in a manner that simulates the environmental and se 

which the equipment will be used (ANSI 1997 and NCRP 1991). Recent evaluations of surface activity discreevaluating comparative licensee and confirmatory survey measurements found a systematic under response 

reported activity levels during cold weather periods. In these cases, alpha plus beta or beta-only scans or meconducted using gas proportional detectors. Normal practice is to conduct calibrations in a laboratory settinginstruments are distributed for use, the conditions may change once the user is out in the field. Temperature v

of 30 to 40° F over the course of a work day are common. Past investigations have determined that the optim

plateau, established during calibration, shifts while the instrument is being used under varying temperature co

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-08 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Some types of data logging instrumentation selected for final status surveys have audio response limitations that 

ability, under certain conditions, to discern the presence of elevated activity.

Discussion: Some types of data logging instrumentation selected for final status surveys have audio response limitations 

surveyors ability, under certain conditions, to discern the presence of elevated activity. These instruments hav

response that plateaus once the count rate reaches 4500 counts per minute (cpm). This condition does not imcontamination assessment and normally does not interfere with assessing beta surface activity when ambienare at typical environmental levels. On the other hand, when these instruments are used for conducting gammscintillation detectors, complicating factors occur. Typical background gamma levels range from approximate

when using the more common NaI detector crystal sizes. It can be immediately seen that the background macapability of the instrument making it impossible for the surveyor to rely on increases in audio response to ide

elevated direct gamma radiation. There are essentially three solutions to this problem, all of which result in e

complicating factors that must be addressed or potential further project costs.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-09 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: NUREG-1757, Vol. 2, Rev.1 illustrates other issues that have been noted related to survey instrumentationDiscussion: Other instrument issues that have been noted include static (disconnection from a continuous gas supply) op

proportional detectors, long detector to instrument cables, and altitude effects on the calibration of gas proporgas proportional detectors are operated in a static mode, there will be some gas leakage from the detector. Adecreases, the detector efficiency degrades accordingly. The rate of gas leakage greatly varies among detec

the factory-installed face and gasket are removed for maintenance. The rate of leakage has been observed to days. Past field observations of FSSes and comparative measurements have found that these detectors may purge, resulting in the underestimation of surface activity levels. Therefore, procedures should specify that wh

mode, the operational parameters should be checked regularly through either a background or source check. below established parameters, repurging the detector would be required prior to continuing surveys. Operatio

voltages more readily allows the surveyor to distinguish a drop in efficiency caused by gas leakage as the bacgenerally in the 200 to 500 cpm range for hand-held detectors — will noticeably decrease. However with the voltage backgrounds of most hand-held gas proportional detectors, a decrease in efficiency will not be immed

therefore will necessitate a regular operational source check to validate performance.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-10 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Equations to calculate the scan minimum detectable concentration (MDC) using the MARSSIM approach are not 

instruments that have an alarm at a pre-determined count rate action level.

Discussion: There have been a number of instances where final status survey procedures have implemented the use of v

coupled to data logging instruments. These instruments in several cases were set to alarm at a pre-determine

level that is calculated to correspond to the derived concentration guideline level, rather than relying on the su

audible response. Although this may be an acceptable practice, with the provision of an adequate technical bscan minimum detectable concentration (MDC) equations are no longer appropriate. The reason for this positderivation of the scan MDC equations are based on signal detection theory. That is, how a human observer ththe audible input and then makes decisions.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Lesson ID: 2005-11 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Procedures for confirmatory surveys in Class 1 survey units require systematically spaced, fixed point gamma me

prescriptive surface scanning over 100 % of the survey unit area.

Discussion: Confirmatory surveys conducted in Class 1 soil survey units at several sites have identified small areas of res

contamination that when evaluated, exceeded the derived concentration guideline level. A root cause analys

determined that the site procedures required systematically spaced, fixed point gamma measurements rather surface scanning over 100 % of the survey unit area in accordance with MARSSIM. Experience has shown tsurveys, where contamination may be more distributed, systematic fixed point gamma measurement can be ularge areas requiring investigation.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-12 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Not listening to audio to audio responses during surface scans can impact a person’s ability to identify locations o

contaminations

Discussion: A significant number of facilities assessed during decontamination and decommissioning do not require the s

instrument audio response while conducting radiological surface scans. Rather, the analog meter is visually 

instrument alarm is set to notify the surveyor when to pause and investigate, a peak trap mode (the maximum 

value is stored in the instrument memory) is used and the data are reviewed for anomalies post-survey, or a s

than the individual using the detector - listens to the instrument audio. Each of these techniques have inhereimpact one’s ability to identify locations of residual contamination.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Lesson ID: 2005-13 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Licensees should consistently apply instrument calibration guidance for assessing alpha and beta surface activity 

7503-1 (ISO 1988) to avoid underestimation of surface-level activity of radionuclides

Discussion: The implementation of the instrument calibration guidance for assessing alpha and beta surface activity recom

(ISO 1988) and adapted into the MARSSIM is not always consistently applied. This issue was identified while license termination plans or specific licensee calibration procedures. The ISO 7503-1 guidance more accurateconditions encountered at decommissioning sites - typically rough, dirty, or porous - and emission energy of t

concern. Without the proper application of the ISO 7503-1 guidance, surface activity levels for alpha and low-contaminants will be significantly underestimated. The guidance recommends a total efficiency that is the pro

- an instrument efficiency (εi ) and a source efficiency (εs ).

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-14 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning WorkSubject: Beta measurements provide a more accurate evaluation than alpha measurements for natural thorium contamina

surfaces

Discussion: There have been several instances where residual natural thorium surface contamination was assessed by p

activity measurements. Natural thorium emits both alpha and beta radiations, therefore, either alpha or beta a

measured for determining the residual activity of the thorium contaminant. However, beta measurements provevaluation of thorium contamination on structural surfaces due to the problems inherent in measuring alpha cporous, and/or dirty surfaces. For the thorium series in secular equilibrium, for each beta emission there are a

emissions - a beta to alpha ratio of 0.67. At one site, both alpha and beta surface activity measurements were 

confirmatory surveys at the same location and the results compared. The data clearly showed the significant alpha attenuation with beta to alpha ratios ranging from 3 to 280 - much greater than the theoretical ratio of 0further evidence that alpha activity is difficult to measure on surfaces that are typically encountered during radwhen possible, beta measurements should be performed.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-15 Facility Type: Reactors, Material Facilities Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning Licensing, Facilitates Decommissioning WorkSubject: Derivation of site-wide ratios between various contaminants in a facility should consider collecting soil samples in 

ratio developed accurately represents both spatial and depth variability of the radionuclide concentrations

Discussion: There have been several instances where a limited number of soil samples were used to determine a site-wid

various contaminants. A surrogate contaminant was then to be measured and the ratio used to account for thcontaminants. In one case, the sampling procedure did not take into account the actual site spatial contamin

Instead, a limited sample data set from one area of the site was relied upon to prepare the radionuclide ratioscollected during earlier scoping surveys clearly demonstrated that the ratio varied among the radionuclides of 

upon which area of the site the sample represented. When the varying ratios were analyzed, it was determinsurrogate ratio that had been developed would significantly underestimate the inferred radionuclide concentra

site. This issue can be readily avoided provided representative samples are collected in such a manner that accurately represents both spatial, and in some cases, depth variability.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-16 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning LicensingSubject: Licensees should use the unity rule to demonstrate compliance with the release criteria if there are multiple contaDiscussion: Recent reviews of final status survey data packages have identified a critical oversight with demonstrating co

release criteria at some sites with multiple contaminants. What has occurred is that each individual radionucli

respective derived concentration guideline level (DCGL) and a conclusion reached as to the acceptability of a 

However, an additional requirement is to apply the unity rule (also known as “sum of fractions”) to the data to dose limit is met. This is based on the DCGL for each radionuclide equating to the dose limit for release of thadditive nature of the dose from each radionuclide, the total residual activity must be proportionality reduced t

each radionuclide divided by its DCGL does not exceed one (unity).

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Lesson ID: 2005-17 Facility Type: Reactors, Material Facilities Stage: Decommissioning PlanningBenefits: Facilitates Decommissioning LicensingSubject: Licensees should consistently apply the recommendations in the Multi-Agency Survey and Site Investigation Man

classification of radiological survey units.

Discussion: Evaluations of licensee survey unit designations and confirmatory surveys have identified inconsistencies wit

in MARSSIM on survey unit classification; primarily involving contaminated Class 2 survey units. That is, conthe derived concentration guideline level that has been found during past confirmatory surveys within Class 2 

expected, the contamination was usually identified in that portion of the survey unit bordering adjacent Class solution for the observed occurrences would have been for the licensee to have extended the size of the Clasinclude adjacent regions. In one case, the contamination was found on the wall portion of the interface betweand Class 2 wall.

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007 
Search Criteria: Year: 2005 Facility Type: All Facility Types

Stage: All Functional Areas Benefit: All Benefits

Lesson ID: 2005-18 Facility Type: Reactors, Material Facilities Stage: Decommissioning WorkBenefits: Facilitates Decommissioning LicensingSubject: Licensees should conduct additional data assessment during final status surveys (FSS) if there are hot spots rem

demonstrate compliance with the basic dose limit.

Discussion: There have been isolated instances where reviews of FSS data packages or confirmatory survey findings ide

where the derived concentration guideline level (DCGL) was statistically satisfied, but hot spots were not fully 

spots remain in a survey unit, the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) rdata assessment to ensure compliance with the basic dose limit. The first recommendation is that each hot sagainst the (DCGL), relative to hot spot size and allowable concentration within the hot spot area. Generally, documented in FSS packages, this recommendation is addressed adequately. A component for demonstratibeen overlooked is showing that the combination of residual hot spot contamination in addition to any uniform

less than the basic dose limit. MARSSIM, Section 8.5.2, provides the equation and narrative guidance for im

documentation in survey units where this condition exists.There have been isolated instances where reviews or confirmatory survey findings identified survey units where the derived concentration guideline level (DCGL

satisfied, but hot spots were not fully addressed. When hot spots remain in a survey unit, the Multi-Agency R

Site Investigation Manual (MARSSIM) recommends additional data assessment to ensure compliance with thfirst recommendation is that each hot spot be evaluated against the (DCGL), relative to hot spot size and allowithin the hot spot area. Generally, for hot spots documented in FSS packages, this recommendation is addrcomponent for demonstrating compliance that has been overlooked is showing that the combination of residucontamination in addition to any uniformly distributed activity is less than the basic dose limit. MARSSIM, Se

equation and narrative guidance for implementation and documentation in survey units where this condition e

References: NUREG-1757: Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of R

2, Rev. 1, Appendix Ohttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/v2/sr1757v2r1.pdf

Monday, September 10, 2007