ML22161A913

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2022 Reew NRC Hq Update
ML22161A913
Person / Time
Issue date: 06/28/2022
From: Steven Garry
NRC/NRR/DRA/ARCB
To:
Stevens G
References
Download: ML22161A913 (48)
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NRC Update ADAMS Accession Number ML22161A913 Steve Garry, CHP Sr. Health Physicist Division of Risk Assessment Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Radiological Effluents and Environmental Workshop June 28, 2022 Savannah, GA

Topics

1. Regulatory Guide Updates

- RG 1.21 ~ Routine Effluent Monitoring

- RG 4.13 ~ Environmental Dosimetry

- RG 4.25 ~ Groundwater Discharges

2. Decommissioning Planning Rule
3. Accident- Monitoring Instrumentation
4. Instrument Calibrations 2

RG 1.21 Measuring, Evaluating, and Reporting Radioactive Material in Liquid and Gaseous Effluents and Solid Waste

  • Updating long-term, annual average /Q and D/Q values
  • Environmental monitoring for iodine (I) -131 in drinking water
  • ODCM - making changes to effluent and environmental programs
  • Calibration of accident-range radiation monitors 3

/Q and D/Q values

  • Long-term annual-average /Q and D/Q should be based on 5 or more years of meteorological data
  • /Q and D/Q values should be reevaluated periodically (e.g., every 3-5 years).
  • If /Q and D/Q values are substantially nonconservative (e.g., higher by 20-30 percent or more), revise /Q and D/Q values used in dose assessment 4

Environmental Monitoring I -131 in Drinking Water

  • Perform a prospective dose evaluation to determine if the likely dose from I-131 in drinking water is > 1 mrem/yr
  • If dose is > 1 mrem/yr, perform I-131 sampling & analysis using an LLD of 1 pCi/L
  • If dose is < 1 mrem/yr, perform I-131 sampling and analysis using an LLD of 15 pCi/L 5

Offsite Dose Calculation Manual (ODCM)

  • ODCMs need to be kept current
  • Plant changes affecting ODCMs:

- Plant operating status (operating or decommissioning)

- Principal radionuclides (e.g., failed fuel or decommissioning status

- noble gas and iodine have been eliminated)

- Installation of new or out-of-service radwaste processing equipment

C-14 Dose Assessment

  • C-14 is likely a principal radionuclide in operating reactors
  • C-14 is not a principal radionuclide for air dose calculations
  • C-14 source term and dose assessment

- Scaling factors can be based on power generation

- NUREG-0016 GALE computer codes

- NCRP-81s C-14 report

- PWRs release ~ 6 curies, (~ 4.6 mrem max dose)

- BWRs release ~ 9 curies, (~4.7 mrem max dose)

  • Appendix I ingestion doses include iodines, tritium and particulate nuclides 7

Environmental Dosimetry for Direct Radiation Dose Assessment

  • RG 4.13, Rev. 2, Environmental Dosimetry - Performance Specifications, Testing, And Data Analysis was revised in June 2019
  • RG 4.13 provides an NRC-approved method of determining facility-related dose (FRD) from direct radiation
  • NRC endorsed ANSI/HPS N13.37, Environmental Dosimetry -

Performance Specifications, Testing, And Data Analysis

  • RG 4.13 methods can be used in the demonstration of compliance with 10 CFR 20.1302 surveys and EPAs 40 CFR 190s dose limit of 25 mrem/year 8

Direct Radiation Data Analysis Method Using Environmental Dosimetry

  • At each location, using historical data, determine the baseline background dose rate and the baseline standard deviation ()
  • Then, perform a 2-step quarterly data analysis process:

- At each location, determine if there is there a detectable increase greater than 3? (a yes/no question)

- If > 3, determine the facility-related dose (FRD)

  • Subtract current quarterly reading from baseline background dose rate
  • Do not subtract the > 3 value
  • Environmental dosimetry systems can measure FRD dose at:

~ 5 mrem/quarter, and ~ 10 mrem/year 9

Compliance with EPA dose limit

  • EPA dose limit required by 10 CFR 20.1301(e) is 25 mrem/yr whole body and any organ (except thyroid)
  • C-14 is a dominant source of organ dose (bone)

- maximum organ dose in 2020 was 4.6 mrem

- Total organ dose = effluent dose plus direct radiation dose

  • For example, total dose = 4.7 mrem + <10 mrem <14.70 mrem
  • < 14.70 mrem is less than the 25 mrem EPA 40 CFR 190 limit 10

Return/Reuse of Previously Discharged Radioactive Effluents

  • RIS 2008-03 states radioactive material with less than exempt concentrations that is properly released in gaseous or liquid effluent is not considered licensed material (does not apply to solids)
  • The unlicensed material can be used and returned to the environment without being considered a new radioactive material effluent release
  • Licensees are responsible for evaluating any new exposure on-site or off-site exposure pathways > 10% of total effluent dose (per RG 1.109) 11

List of Leaks and Spills (L&S)

  • 55 - currently licensed and operating nuclear sites
  • 38 of those sites historically have had L&S of H-3 20,000 pCi/L reported
  • 7 sites currently have residual radioactive ground water with H-3 20,000 pCi/L 12

Leaks and Spill Remediation

  • SRM-SECY-13-108, Remediation of Residual Radioactivity During Operations
  • Evaluate feasibility of prompt remediation
  • However, prompt remediation is not a requirement 13

14 RG 4.25 Groundwater Discharges

  • RG 4.25 - guidance on calculating on-site groundwater discharges to off-site groundwater
  • Groundwater discharge to off-site areas is not a calculation of plant releases into the on-site subsurface groundwater 15

Reporting Abnormal Discharges (leaks and spills)

  • RG 1.21, Section 9.5 Supplemental Information

- Provides guidance on abnormal releases from plant equipment into onsite groundwater

- Reporting thresholds include:

  • Voluntary reports under NEI 07-07, Industry Groundwater Protection Initiative - Final Guidance Document, Rev. 1
  • Abnormal discharges to the unrestricted area
  • Information submitted should include:
  • Date, duration, volume, etc.
  • Doses to public 16

On-site Discharges into On-site Ponds

  • Some licensees dispose of liquid effluents to on-site ponds as though releases were to the unrestricted area (10 CFR 50.36a)
  • Most on-site ponds leak into on-site groundwater (GW)
  • There is an important footnote in RG 4.25 that provides an exclusion for reporting leakage from on-site ponds into GW if previously accounted for

- Leakage from bottom of lake or pond to groundwater does not need to be reported (again)

  • However, the potential dose (through a new groundwater pathway) must be assessed if the off-site dose from leakage from onsite ponds is greater than 10% of all pathways combined per RG 1.109
  • RG 1.109, Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR part 50, Appendix I 17

Decommissioning Planning Rule* (DPR)

  • Licensees are required to plan for decommissioning during operations
  • The DPR as revised in 2012 made changes to 10 CFR 20.1501(a) to include performing radiological surveys in the subsurface (i.e., ground water)
  • 10 CFR 20.1406(c) - Licensees shall minimize residual radioactivity (contamination), including subsurface (ground water) 18

10 CFR 20.1501 Radiological Surveys and Monitoring

  • Related documents:

- NEI 07-07, Industry Groundwater Protection Initiative - Final Guidance Document, Rev. 1

- NEI 08-08, Generic FSAR Template Guidance for Life Cycle Minimization of Contamination

- NEI 09-14, Guideline For The Management Of Underground Piping And Tank Integrity 19

Decommissioning Programs

  • Groundwater monitoring may need to be increased in support of license termination
  • Licensees must maintain and update 10 CFR 50.75(g) record keeping files to include leaks and spills
  • Decommissioning-related RGs

- RG 4.22, Decommissioning Planning During Operations

- RG 1.185, Standard Format and Content for Post-Shutdown Decommissioning Activities Report

- NUREG-1757, Consolidated Decommissioning Guidance

- Draft Revision of NUREG-1757 for public comment 20

Accident Monitoring Instrumentation

  • RG 1.21, Rev. 1 Measuring, Evaluating, and Reporting Radioactive Material In Liquid and Gaseous Effluents And Solid Waste summarizes previously issued NRC requirements and guidance in:

- NUREG-0737, Clarification of TMI Action Plan Requirements (ML051400209)

- HPPOS-001, Guidance on Calibration and Surveillance to meet Item II.F.1, Additional Accident-Monitoring Instrumentation 21

Accident Monitoring Instrumentation (Contd)

  • Item II.F.1 is Additional Accident-Monitoring Instrumentation requiring:

- Noble gas effluent monitoring (Item II.F.1-1)

- Iodine and particulate sampling and analysis (Item II.F.1-2)

- Containment high range radiation monitoring (II.F.1-3)

  • Specifications for radiation monitoring equipment are provided in Tables II.F.1-1, II.F.1-2, and II.F.1-3 22

Accident-Range Radiation Monitors

  • Three different instrument criteria to discuss:

- Instrument design criteria

- Instrument calibration criteria

- Instrument measurement criteria 23

Three Different Criteria

  • Design criteria:
  • RG 1.97, Instrumentation For Light-Water-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During And Following an Accident, establishes a design accuracy criteria of a factor of 2
  • Note: These are design accuracy criteria, not calibration criteria 24

Accuracy Criteria

  • NUREG-0737, Rev. 1, Clarification of TMI Action Plan Requirements states that the accuracy requirement is that accuracy is sufficient to perform intended function
  • ANSI N320-1979, Performance Specifications for Reactor Emergency Radiological Monitoring Instrumentation provides an accuracy criteria of +/- 40%

at the 95% confidence level

  • IEEE-497, Accident Monitoring Instrumentation for Nuclear Power Generating Stations specifies accuracy within +/- 50%

25

Measurement criteria NUREG-0737

  • Item II.F.1 Additional Accident-Monitoring Instrumentation

- Effluent monitors should be able to measure fresh noble gas mixtures (0 - 10 days) within overall system accuracy factor of 2

- Containment High Range Monitors (CHRMs) should be able to measure within factor of 2 26

Design, Calibration & Measurement Criteria

  • Design criteria is prescribed in RG 1.97 within a factor of 2 (not the calibration accuracy)
  • Calibration criteria is prescribed in NUREG-0737 as sufficiently accurate to perform the intended function

- ANSI N320-1978 says (calibration) accuracy should be +/- 40%

- IEEE-397 - (calibration) accuracy should be +/- 50%

  • Measurement criteria is prescribed in NUREG-0737 as per RG 1.97 (i.e., within a factor of 2) 27

Health Physics Positions (HPPOS)

Calibration of Accident-Range Radiation Monitors

  • HPPOS-001 is a summary of the NRC guidance on meeting Item II.F.1 calibration and surveillance criteria
  • The memo from D. G. Eisenhut (NRR) to Regional Administrators contains detailed calibration guidance and is located in ADAMS at Accession Number ML103420044 28

NUREG-0737 Item II.F.1-1 Noble Gas Effluent Monitoring

  • Ion chamber, GM detector, scintillator or CdTe(Cl) solid-state detector output is in mR/hr or cpm
  • Manufacturer provides energy response characterization from low (~81 keV) to high (~3 MeV) gamma energy
  • Manufacturer provides instrument response factor (efficiency factors) for Xe-133 (and Kr-85 for scintillators and CdTe(Cl) detectors) 29

NUREG-0737 Item II.F.1-1 Noble Gas Effluent Monitoring

  • Licensees perform periodic calibration checks with a solid source to ensure proper operation
  • Licensees should account for time-dependent, changing radionuclide mix 30 30

NUREG-0737 Item II.F.1-2 Iodine and Particulate Monitoring

  • Real-time iodine and particulate monitoring is not practical
  • Licensees must develop procedures for collection and analysis of samples
  • Note: Iodine releases can be calculated based on partitioning (scaling) factors to noble gas (RG 1.21) 31 31

Item II.F.1-3 Containment High Range Monitors (CHRMs) 32 32

Instrument Calibrations 33

Accident Range Effluent Monitors Initial Vendor Calibrations

  • Vendors perform initial calibrations:

- Perform dose-rate linearity check

- Determine the detectors energy response characteristics

- Determine the instrument response factor for a standard gas (Xe-133 or Kr-85)

- (µCi/cc) / (cpm) or (µCi/cc) / (mR/hr)

- Vendors also build a field calibrator with a Cs-137 source for licensees use for in-plant calibration checks

- Vendors provide a calibration check source value (~ 7 R/hr) 34

In-plant Calibration Checks

  • I&C / RP / Chem conduct a one-point radiological calibration check
  • Licensees decay correct the check source value
  • I&C conduct an electronic calibration check for all scales above first decade
  • Instrument adjustments are normally NOT made based on the radiological calibration check 35

Instrument Response Factors (Noble gas monitoring)

  • Historically, noble gas monitoring instruments are GM detectors, ion chambers, plastic scintillators, or CdTe(Cl) solid-state detectors
  • GM and ion chambers are typically calibrated to Xe-133; i.e., to low energy, 81 keV photons with low yield (~36%)
  • Plastic scintillators and solid-state detectors are calibrated to Xe-133 (gamma) and Kr-85 (beta)
  • Energy response curves are provided in the vendor calibration summary report 36

Instrument Response Factors (noble gas monitoring) (Contd)

  • Detector output is a count rate or a dose rate
  • Output is converted to a Xe-133 concentration, µCi/cc
  • Concentration (µCi/cc) times flow rate (cubic feet per sec) = release rate (µCi/sec)
  • µCi/cc x flow rate = release rate (µCi/sec) of Xe-133 37

Challenge (noble gas monitoring)

  • Gaseous effluent is not just Xe-133
  • Gaseous effluent is a mix of noble gases, and is very energy dependent and time dependent
  • Generally, short-lived noble gas nuclides have higher energy gammas than long-lived nuclides
  • Detector efficiency is higher for high energy gammas
  • A time-dependent instrument response factor for a mix of noble gases is needed 38

Accident Source Term: 13 Noble Gases 6 Kryptons 7 Xenons

  • 1. Kr-83m 7. Xe-131m
  • 2. Kr-85m 8. Xe-133m
  • 4. Kr-87 10. Xe-135m
  • 5. Kr-88 11. Xe-135
  • 6. Kr-89 12. Xe-137
13. Xe-138 There are ~ 60 different gamma energies and gamma yields from 13 noble gas nuclides to consider 39

60 Gamma Energies Half keV Half keV Half keV Life Life Life 40

GM Instrument Response Factors (based on calibration to Xe-133)

Relative Response to Xe-133 Instrument Over-Response Factors 36.0 31.0 Core Melt 26.0 21.0 16.0 11.0 6.0 Gas Gap 1.0 0.1 1 2 4 8 12 24 48 168 720 Hours after shutdown 41

Plant Staff Responsibilities

  • Plant staff should know:

- which department is in charge

- what equipment is installed

- how equipment works (vendor manuals and calibrations)

- how calibration checks are performed

- the basis for instrument response factors

- how monitor output interfaces with dose assessment codes 42

NRC presentation at REEW in 2018 Accident-Range Gaseous Effluent Monitoring Calibration and Time-Dependent Instrument Response Factors ADAMS ML18171A035 Steve Garry, CHP Sr. Health Physicist Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Radiological Effluents and Environmental Workshop June 27, 2018 New Orleans, LA 43

Iodine and Particulate (I&P)

Monitoring

  • Real-time iodine and particulate monitoring is not required
  • However, licensees should have procedures for sample collection and analysis of hot samples
  • Real-time dose assessment can be performed using scaling factors to noble gas 44

Containment High Range Monitors (CHRMs)

  • CHRMs measurements are used in Emergency Action Levels (EALs) and for core damage assessment
  • Core damage assessment methods are in NUREG-1940, Radiological Assessment System for Consequence Analysis (RASCAL) section 1.2.8 and NUREG-1940, Supplement 1, Section 2.6
  • Licensee staff perform a one-point radiological calibration check below 10 R/hr
  • Licensee staff perform an electronic calibration check for each decade above 10 R/hr 45

NRC staff training CHRMs

  • NRC gave training to NRC inspection staff on CHRMs in 2021
  • Training material is publicly available at ML21327A271 46

Questions & Discussion 47

Acronyms ARERR Annual Radioactive Effluent Release Report CHRM Containment High Range Monitor FRD Facility-Related Dose GALE Gaseous and Liquid Effluents GW Ground Water GM Geiger-Mueller GPI Groundwater Protection Initiative LLD Lower Limit of Detection ODCM Offsite Dose Calculation Manual RASCAL Radiological Assessment System for Consequence Analysis RG Regulatory Guide TS Technical Specifications 45

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