ML22208A284

From kanterella
Jump to navigation Jump to search
2022 NEI RP Forum Slides - Calibration (Steve)
ML22208A284
Person / Time
Issue date: 07/27/2022
From: Garmon D
NRC/NRR/DRA/ARCB
To:
Garmon D
References
Download: ML22208A284 (25)
v • d • e


Text

1 NRC Update NEI Radiation Protection Forum Steve Garry, CHP Sr. Health Physicist Office of Nuclear Reactor Regulation Division of Risk Assessment U.S. Nuclear Regulatory Commission August 2, 2022 (ML22208A284)

2 RG 1.21 - Accident-Range Gaseous Effluent Monitoring

  • RG 1.21 summarizes previously issued NRC requirements and guidance in:

- NUREG-0578 (July 1979) ~ TMI Short Term Items

- NUREG-0660 ~ TMI Action Plan Requirements

- 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

- NRR Letter to Regional Administrators, (August 16, 1982) Proposed Guidance for Calibration and Surveillance

3 Accident-Range Gaseous Effluent Monitoring

  • 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 in Tables II.F.1-1, II.F.1-2, and II.F.1-3

4 Containment High Range Monitors (CHRM)

  • CHRM 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

5 RG 1.21 Accident-Range Gaseous Effluent Monitoring

  • RG 1.21 summarizes previously issued NRC requirements and guidance in:

- NUREG-0660 ~ TMI Action Plan

- 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

6 Accident-Range Gaseous Effluent Monitoring

  • 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 in Tables II.F.1-1, II.F.1-2, and II.F.1-3

7 Accident-Range Radiation Monitors

  • Three different instrument criteria to discuss:

- Instrument design criteria

- Instrument calibration criteria

- Instrument measurement criteria

8 Three different criteria:

  • Design criteria:

- RG 1.97 establishes a factor of 2 for design criteria, not a calibration criteria

  • Calibration criteria:

- NUREG-0737 - sufficient to perform intended function

- ANSI N320-1979 and IEEE-497 - generally +/- 40% - +/- 50%

  • Measurement criteria:

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

- CHRMs should be able to measure within factor of 2

9 Calibration of Accident-Range Radiation Monitoring Equipment

  • Actual guidance is in a letter from NRR to NRC Regional Administrators (ML103420044)

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

  • GM detector, scintillator or CdTe(Cl) detector output is in cpm or mR/hr
  • Manufacturer provides energy response characterization from low to high gamma energy (~81 keV to 3 MeV)
  • Manufacturer provides instrument response factor (efficiency factors) for Xe-133 (and Kr-85 for scintillators and CdTe(Cl) detectors)
  • Licensees perform periodic calibration checks with a solid source
  • Licensees perform periodic calibration checks with a solid source to ensure proper operation

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

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

12 NUREG-0737 Item II.F.1-3 Containment High Range Monitor (CHRMs)

13 In-plant calibration checks

  • Instrument and Control (I&C) technicians do a one-point radiological calibration check in the first scale/decade
  • I&C do an electrical calibration checks for higher scales/decades
  • HP only provides radiological support (RWP, pre-job briefings, and job coverage)
  • Instrument response factors (efficiency factors) are normally NOT adjusted

14 Instrument Response Factors (Efficiency Factors)

  • Noble gas monitoring instruments are GM detectors, plastic scintillators, and CdTe(Cl) solid-state detectors, typically ~2 mm x 2 mm x 5 mm size
  • Each solid-state detector has its own counting efficiency -

(Monticello, Waterford examples)

  • 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)

15 Instrument Response Factors (Efficiency Factors for effluent monitors)

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

16 Radionuclide Mix

  • Gaseous effluent is not just Xe-133
  • Gaseous effluent is a mix of noble gases, and is very time dependent
  • Generally, short-lived noble gas nuclides have higher energy gammas than long-lived nuclides
  • Efficiency factors are 10 - 30 times higher for high energy gammas
  • A time-dependent efficiency factor (instrument response factor) is needed

17 GM Detector Instrument Response Factors (based on calibration to Xe-133) 1.0 6.0 11.0 16.0 21.0 26.0 31.0 36.0 0.1 1

2 4

8 12 24 48 168 720 Instrument Over-Response Factors Core Melt Gas Gap Relative Response to Xe-133

18 Potential Errors in Use of Efficiency Factors (instrument response factors)

  • Licensees use wrong calibration geometry
  • Licensees may use wrong efficiency factors

- Assume 1 efficiency factor fits all detectors

- Replace detectors and do not update efficiency factors (particularly General Atomics CdTe(Cl) solid state detectors

- Apply Xe-133 efficiency factor to the radionuclide mix

19 Plant staff responsibilities

  • Plant staff:

- Some plants have lost their rad-engineering expertise

- I&C does calibrations without knowledge of radiological response characteristics

  • Plant staff should know:

- what equipment is installed

- which department is in charge

- how equipment works (vendor manuals and calibrations)

- how calibration checks are performed

- the basis for efficiency factors and detector specific factors

- how monitor output interfaces with dose assessment codes

20 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 2018 REEW Presentation - Effluent Monitoring

21 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

22 Containment High Range Monitors (CHRM)

  • CHRM 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

23 NRC staff training CHRMs

  • NRC developed, provided, and recorded training on CHRMs calibration in 2021

24 Plant staff responsibilities

  • Plant staff:

- Some plants have lost their rad-engineering expertise

- Instrument and Control (I&C) staff may be doing calibrations without knowledge of radiological response characteristics

  • Plant staff should know:

- what equipment is installed

- which department is in charge

- how equipment works (vendor manuals and calibrations)

- how calibration checks are performed

- the basis for efficiency factors and detector specific factors

- how monitor output interfaces with dose assessment codes

Questions & Discussion

Retrieved from "https://kanterella.com/w/index.php?title=ML22208A284&oldid=3792826"