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MARLAP, MARSSIM and RETS-REMP: How is All of this

Related…or NOT?

Robert Litman, Ph.D.Eric L. Darois, MS, CHP

Radiation Safety & Control Services, Inc.Stratham, NH

www.radsafety.com

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RETS-REMP

• Two separate programs required of Nuclear Power Plants for assessment of dose to the public based on modeling assumptions of uptake and measurements of activity concentration and rate of release from the plants.

• Related documents for these programs:– Technical Requirements Manual/Technical Specifications– RG 4.15– RG 1.21– 10CFR50– 10CFR20– others

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Program Objectives?

Exactly what is it that we want to measure?1. Difference between background concentration and

concentration of radionuclides released in the respective medium

2. Proximity of radionuclide concentration released to the limit specified in 10CFR20 and 10CFR50

3. An administrative limit established by an omniscient executive director

4. None of the above

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Old Terms

• Precision– How close to the “true value” the

measurement is

• Accuracy– How reproducible the measurement is

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Measurement Quality Objectives(MQOs)

• What are MQOs?• Are they necessary?• Do they apply to the RETS or REMP

Programs?• Is there a rational approach to how the

MQOs are established?• Does any one verify that the MQOs have

been achieved (and how does one go about doing that)?

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MARSSIM

• The Multi-Agency Radiation Survey and Site Investigation Manual (NUREG-1575, EPA 402-R-97-016)– A guidance document– Provides information on planning, conducting,

evaluating and documenting Final Status Surveys (FSS) in support of decommissioning.

– Provides a consistent approach to the FSS radiological issues and encourages effective use of resources.

– Focuses on field sampling methodologies to support the FSS activities

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The MARSSIM Process

• Originally written for planning for the decommissioning or closure of facilities contaminated with radioactive materials.

• Historical Site Assessment (10CFR50.75(g)• Facility Characterization• Facility Classification (1,2,3, Non-Impacted)• Survey Areas and Survey Units• Final Status Survey Design (DQOs)

– Data Quality Objectives– Derived Concentration Guideline Levels– Sampling Density– Scanning Methods and Density Elevated Measurement Comparison

• Data Review and Interpretation – Data Quality Assessment (DQAs)• Non-Parametric Statistical Tests – Survey Unit Passes or Fails

• Use of DQO and DQA process can apply to RETS-REMP

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MARSSIM

• Provides significant information regarding the planning of the location and numbers of samples to be taken for environmental monitoring.

• Applicable to REMP program?

• What about looking forward to decommissioning?

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MARLAP

Multi-agency Radiological Laboratory Analytical Protocols Manual (NUREG 1576, EPA 402-B-001C)– A guidance document– Two parts, three volumes– Provides a structured approach to project planning

(Part I)• Identifying MQOs• Identifying a project plan team and responsibilities• Selecting a laboratory to perform analyses• Selecting a method for the radiochemical analyses• Data verification and validation method

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MARLAP (continued)

– Provides a significant amount of technical information on (Part II):

• Sample Preparation• Sample Digestion• Radiochemical Separations• Nuclear Counting Techniques• Laboratory Quality Control• A rational approach to data evaluation

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MARLAP (continued)

• What are the individual data components that are inputs to your dose calculations for RETS or REMP?

• Can the guidance in MARLAP be applied to these?

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Data Trends

• How do you know the data are valid?

• Are there written acceptance criteria for results?

• How are the data evaluated?

• Should RETS or REMP data be trended?

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Uncertainty

• How do you define it?

• Is it a necessary parameter?

• Can it (should it) be used for data evaluation?

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MARLAP - Principals

The central principal of the MARLAP is:

Required Method Uncertainty1

Or…

How well do you really need to know what you are measuring?

1Same concept as used in MARSSIM

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MARLAP - Uncertainty

The required method uncertainty is based on:

• the ‘important range’ of your data1 defined by:– An upper bound called the Action Level– A lower bound called the discrimination level

AND

1Referred to as the ‘Gray Region

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MARLAP - Uncertainty

• The acceptable error rate for that data to fall either above the Action Level (AL) or below the Discrimination Level (DL)

The required method uncertainty is defined as:

uMR = [AL –DL]/(sum of error rates)

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MARLAP - Uncertainty

• When the acceptable error rate for a Type I and a Type II error on an individual sample are held at 5%, The equation reduces to:

uMR = [AL – DL]/(1.645 +1.645) = [Gray Region]/3.29

This is frequently identified as Δ/3.

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Uncertainty and the Action Level

Relatively large uncertainty can be tolerated:

Either more accuracy or more samples are needed:

Δ

Δ

The closer the mean of the distribution of analytical results is to the action level, the smaller the uncertainty needs to be to distinguish the mean from the action level.

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Uncertainty and the Action Level

Some observations regarding uMR:• As the gray region decreases the uMR

value decreases (at the same error rate)• As the acceptable error rate decreases the uMR value decreases for the same gray region

• If your sample value is at the action level, there is a 50% chance that the ‘true value’ is above the action level

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An Example

Values for α or βerror ratesRate Value0.001 3.0900.01 2.3260.025 1.9600.05 1.6450.10 1.2820.20 0.8420.30 0.5240.50 0.000

Your WL discharge limit is 5x10-6 μCi/ml for 137Cs (otherwise the tank will need to be reprocessed). Your Site Director says he wants to be 99.9% sure that your measurement will show that the tank is less than this value. What is the maximum value that the tank can have to prove this?

Gray Region = [5x10-6 – zero]

uMR = 5x10-6/(2x3.09) = 8.1x10-7

In order to prove that the tank is not above the AL, with 99.9% surety the value cannot exceed [AL – 3.090x8.1x10-7] = 2.5x10-6 μCi/ml

For the same example change the gray region to [5x10-6- 2x10-6] and the “do not exceed” value becomes 3.5x10-6 μCi/ml.

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REMP Data Evaluation

You have received your latest report form the contract laboratory for offsite well analysis (closest DW supply). All analytical radionuclide values required by your REMP program are reported as “non-detects”, except for 59Fe which is reported as 45 pCi/L. Your reporting limit is 400 pCi/L and your ‘required detection limit’ is 30 pCi/L.

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REMP Data Evaluation

What do you do?1. No investigative action as the value is below

the reporting level2. Notify the NRC that a potential release has

occurred as you are above the required detection limit

3. Have the laboratory reanalyze the sample and hope for a value less than the required detection limit.

4. Something else….

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REMP Data Evaluation

Trending of REMP data and qualifying each radionuclide result provides historical evidence of normal variation in measurements at the background levels.

The record of qualifiers and of QC data agreement also provides information about the consistency of the results.

Both provide factual information to defend decisions about detectability of data and to what population the data most likely belongs.

Information on how to incorporate these into your program is found in the MARLAP.

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Questions ?