Accident Monitoring Flashcards
What is the primary function of Accident Monitoring?
- Provide for, and readily identify, reliable Control Room indications for key plant parameters For use during Accident Conditions
- Provide Type A, B, and C, – Category 1 and 2 instruments capable of withstanding all accident environments, with ranges and scales appropriate for all anticipated conditions
What requires Accident Instrumentation?
- 10 CFR 50 Appendix A
- Regulatory Guide 1.97
- Technical Specifications
Discuss Reg Guide 1.97.
Reg Guide 1.97
* 1983 NRC issued Reg. Guide 1.97 as a controlling document to identify, categorize and qualify instruments necessary for accident monitoring.
* Variable types A thru E (Primary Function / Based on information provided) with categories 1, 2, 3 were identified (Qualification Level / Importance Level).
* Reg Guide 1.97 Instrumentation is that which is required to:
a) Remain functional throughout an accident event, including EQ for Cat 1 and 2 instruments.
b) Be qualified to standards assigned per RG 1.97 Table 1.
c) Provide indication in extended range operation considering all anticipated conditions.
Discuss the Types of Accident Instrumentation.
Type A
* Information Needed to Guide Manual Actions, (Such as Depressurizing during a SGTR).
Pzr Press
RCS Th & Tc Temps
S/G level
Containment Hydrogen Concentration
Type B
* Capability to Assess Success of Safety Functions – Must be category 1
Reactivity Control,
MVA,
RCS inventory and pressure control,
Core heat removal,
RCS heat removal,
Containment Integrity,
Containment Pressure and Temperature Control,
Containment Combustible Gas Control).
Type C
* Information on Fission Product Barrier Status
Fuel cladding,
RCS pressure boundary,
Reactor Containment
Type D
* Status of Operating Safety Systems
Type E
* Status of the Magnitude of Releases
SJAE
CTMT Pigs
Rx shield building and annulus radiation monitors
Discuss Categories of Accident Instrumentation.
- Category 1 - Full qualification: Standby Power, Seismic, EQ, Redundancy, Real Time Display
- Category 2 - Similar to Cat 1, but Neither Standby Power Nor Real Time Display Required.
- Category 3 - Least Stringent Requirements. Good Commercial Grade Quality Acceptable.
Discuss
Category 1 & 2 environmental (Adverse).
- White Bezel instruments are all Type A, B, C and Category 1 and 2.
- Designations: Class 1E / Safety Related / EQ / Seismic Qualified
Discuss 1E Instruments.
Class 1E applies to electronic and electrical equipment only (1E)
* Essential to emergency reactor shutdown, containment isolation, reactor core cooling and containment and reactor heat removal or are otherwise essential in preventing significant release of radioactive material to the environment.
* EQ Cat 1 & 2 classification given to components required to be functional during and/or after a DBE All class 1E and safety related components are required to be Seismic Qualified.
Discuss Environmentally Qualified (EQ).
Environmentally Qualified (EQ)
* Specifies that Electrical Equipment (including instrumentation) Important to Safety, Shall Remain Functional Under the Most Adverse Environmental Conditions Expected, and Shall Include:
a) Safety-Related Equipment
b) Some Non Safety-Related Equipment
c) Certain Post-Accident Instruments
* Required per 10 CFR 50.49
* All Class 1E components are safety related, but not all safety related components are Class 1E.
* Potential “Harsh Environment” areas:
a) Containment
b) Certain areas of the RAB
c) Steam Trestle
* Instruments include those in the following systems:
a) NI’s
b) CEA Position Indication
c) RPS
d) ESFAS
e) QSPDS
f) ERDADS/SAS
* EOP’s that involve a “harsh” environment have a Caution statement stating that RG 1.97 instruments should be used when verifying safety functions.
* Harsh environment indirectly defined in 10 CFR 50.49 as not being a “mild” environment, which is defined as “normal” (i.e., non-accident) conditions.
* Harsh environment is an environment with elevated temperatures, pressures, and radiation levels.
Radiation Levels ≥ 105 RADs cumulative during an event
Radiation Levels ≥ 103 RADs cumulative during an event for Teflon™ coated components.
Why is Safety Related Equipment necessary?
Safety Related Equipment necessary to assure the:
* Integrity of the Rx Coolant pressure boundary
* Capability to shutdown and maintain the Rx in a safe shutdown condition
* Capability to prevent or mitigate the consequences of accidents which could result in offsite exposures comparable to 10CFR100 levels
Discuss Seismic Qualified.
- Components capable of functioning during and/or after the site Design Basis Earthquake (DBE): Safe Shutdown Earthquake (SSE) / (Acceleration of 0.1g) are seismic qualified.
- Required of all safety-related components
Discuss Emergency / Accident Event monitoring sequence.
- White Bezel – Preferred for use
- Other Reg. Guide 1.97, safety related,
- Other Reg. Guide 1.97 instruments,
- Other instruments,
- ERDADS Display for confirmation.
Discuss Instrumentation Basics.
- White Bezel instruments are all Type A, B, C and Category 1 and 2.
- Instrument indications are to be believed unless conflicting information is more compelling
- Verify with Redundant, Independent Indicators for Same Parameter
- Use Redundant/Backup indications when Primary or Key Variable indicators are not available.
- Verify with diverse parameter(s) that indicate same condition - i.e. fluctuating motor amps, fluctuating discharge pressure, indicate a cavitating pump
- Accident Instruments may be different from those normally monitored
Discuss Instrumentation Specifics.
- Versatile & OTEK indicators don’t read anything with a loss of power (including scale)
- Sigmas fail As-Is on loss of power (some have a power on light)
Discuss Remote Shutdown Instruments.
- Minimum set of instrumentation necessary for the specific accident of Control Room Inaccessibility, in which no other accident event is assumed to occur.
- Remote Shutdown Instruments are for use in a CRI event.
- Separate Technical Specifications address Remote Shutdown Instrumentation
- Some accident instrumentation can also be Non safety related and are used as backup instruments.
- Reg. Guide 1.97 does not apply to Remote Shutdown Instrumentation
Discuss Procedures / Tech Specs.
- Accident and Remote have different requirements for the establishment of required instruments. Accident is for mitigation of accidents and Remote is minimum instrumentation for control of plant due to only a Control Room Inaccessibility.
