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What are the positions and responsibilities within the control room?
- SM (Oversight)
- CRS (Command and Control)
- RM (Oversight and Direct Reactivity Manipulations)
- RO (Perform Manipulations)
- RE (Conrol Room Advisor)
- STA (Gives Engineering Advice to the Crew)
What is the purpose of the 1/m plot?
What are the count rate points used to perform them?
How is 1/m calculated?
To prevent early criticality
- Start up channels (<2000cps)
- Log Channels - Safety channels A, B, C, D
1/m = CR0/CRx
What are the restrictions on the magnitude in Phase I
- Phase 1: From reg group 1 @ 0 to PDIL
- Pull Doubbling
- Hold Points ~ 150 pcm
What are the restrictions on the magnitude in Phase II
- Phase 2: From PDIL to -150 pcm
- Count Doubbling
- 1/2 distance to criticality
What are the restrictions on the magnitude in Phase III
- Phase 3: from -150 to critical; trying to go to critical
- Pull 75-100 pcm
- SUR limit 1 DPM (target 0.3DPM)
What is early criticality?
Critical below the PDIL.
Why do you not want to be critical below the PDIL?
- PDIL is group 3 @ 60; do nt want to vilate the LAW!
- Since PDIL is the way we satisfy shutdown margin
Explain shutdown margin.
The amount (pcm) by which the reactor can be made instantaneously subcritical assuming the most worthy rod is stuck full out. No credit is taken for partial strength.
Why is count doubbling important?
If your counts double you have reached 1/2 the distance to criticality.
Define overall doubbling.
Count doubbling (pcm)
What is ECC? What does it encompass? How is ECC determined?
Estimated Critical Condition (based on prediction)
- Estimated Critical Boron Concentration (ECBC)
- Estimated Critical Rod Position (ECRP)
Determined from the rod worth curve
What are the restrictions after the 4th doubbling?
your overall doubbling must be <100 pcm.
How do you know when you have reached criticality?
the reactor will experience a continuous rise in power (counts) with no rod motion (which means the reactor is supercritical).
When must you abort startup?
When two consecutive ACP's are below the PDIL or -500
What is the PDIL? Why do you not want to go critical before it?
- Power Dependent Insertion Limit
- Group 3 @ 60
- The LAW!
What are the modes during the startup process?
Draw and explain the 1/m plot.
What are the time limitations for the ECC?
- Within 1 hour for < 96 hours
- Within 1 day for > 96 hours
What is fissle material? Name some of them.
- Fuel that causes fission at lower energies.
What is reacticity?
The fractional change in neitron population per generation.
What is the MTC?
- Moderator Temperature Coefficient
- Reactivity inserted into the core per degree of change in the mderator temperature
What happens to the value of the MTC as the soluble boron concentration increases?
The MTC increases
Should MTC be positive or negative? Why?
How does a - MTC effect reactivity?
- Negative; We want the reactor to be "inherently stable"
What are the most significant fission product poisons that exist in the core? How do they work?
- Xenon-135 and Samarium - 149
- They have extremely large microscopic cross sections that absorb thermal nuetrons
What is Xenon?
How is Xenon-135 produced?
Xenon - a good poison
- 1. Directly from fission
- 2. Indirectly from radioactive decay of Iodine-15
How is Xenon-135 removed from the core? When is the core considered Xenon free?
- 1. From radiactive decay (beta minus)
- 2. From the neutron absorbing process (producing Xe-136) or burnout
Considered Xe free after 96 hours
What defines a transfer?
Grappling a FFA initiates, ungrappling completes
What are the sequence control modes for moving fuel?
- 1. Pre-planned: all details provided, changes require authorization
- 2. Field-directed: boundaries provided, details written in field
How are move locations determined?
- 1. Availability: Shall
- 2. Eligibility: Shall
- 3. Security: Shall for recently discharged assemblies (n-1)
- 4. Strategic: optional
- *Always want to minimize fuel movement
Define excess reactivity.
the amount of reactivity beyond that required for criticality.
What control the basic forms of control poisons?
- 1. Control Rds (CEA's)
- 2. Soluble Poison (B-10)
- 3. Erbium part of fuel mix (Erbia pins)
What are the uses for burnable poisons?
- 1. Minimize control reacticity requirements at the BC
- 2. Able to use greater fuel load - allows fr a logner cycle
- 3. Limit "hot spots" when loaded in strategic locations.
Define linear heat rate. What are the units?
- Local Power Density; power produced per foot of fuel rod
- Units of kW/ft.
Point of maximum heat transfer rate sustainable with nucleate boiling
What is the DNBR tech spec limit?
Draw and explain the boiling water curve
What are the parameters that advesely affect DNBR?
- Decrease in Temperature
- Decrease in Pressure
- Decrease in Flow
- Decrease in Power Level
- critical heat flux/actual heat flux (can relate to the bioling water curve)
- Desireable to have a larger ratio; further away from nucleate boiling
Why is nucleate boiling not desirable?
DNB will result in fuel clad damage
What are the 3 safety limits and what do they protect?
- Reactor Core Safety limits (fuel Protection):
- 1. DNBR > 1.34; applies to MODES 1 & 2;
- 2. Fuel Peak Centerline Temperature <5080; applies to MODES 1 & 2
- RCS Pressure SL (RCS Integrity):
- 1. RCS Pressure <2750 psia; MODES 1-5
What does the SAFDL limit on peak centerline temperature protect?
- Protects the fuel pellet
Name the fission product barriers.
- 1. Clad
- 2. RCS
- 3. Containment
What are the setpoints for COLLS and CPCS and what do they trigger?
- COLSS - Set point of 13.5 KW/ft. - Triggers alarm
- CPCS - Set point of 21 KW/ft - Triggers a Reactor Trip
What is COLSS and how does it work?
- Core Operating Limit Supervisory System
- Assists operator in monitoring Tech Spec LCO's for DNBD and LHR for POL
- Uses Incores (61 strings, 5 levels per string spaced evenly)
- Not a safety system - will alarm but not trip the plant
Describe the reload process:
What are the modes of operation as according to Tech Specs?
What general information is contained in the SABDs? Why were the SABDs created?
- 1. Description of the Event
- 2. Licensing Bases
- 3. Analysis Methodology
- 4. NSSS Response to Event
- 5. Systems required to mitigate the event
- 6. Analysis History
SADBs are qualified documents that hekp engineers perform UFSAR ch. 15 Safety Analysis in accordance with the licensing bases.
How are changes made to the SADBs?
PVAR --> Design Bases Change Package (DBCP) as according to 05DP-0NF22, Appendix B
How do you know if there are change documents issued against teh SADBs?
Change mechs tab in SWMS
What is a licensing bases document? Name a few.
- A document for which the NRC has established requirements for content, reporting, and change control.
- Examples: UFSAR, Tech Specs, QA Plan, Security Plan, E-Plan, Fire Protection plan, COLR
Are SABDs licensign bases documents?
No, they have never been submitted to the NRC for any type of approval.
What is the UFSAR?
an update of the safety analysis report submitted to the NRC to get an operating license
Is the UFSAR a licensing bases document?
Yes, the NRC has established requirements for content, reporting, and change control
What procedures govern updates to the SABDs?
- 05DP-0NF22 - general design control requirements
- 04DP-0NF09 - more specific requirements for generating the analyses and SABDs
What is the purpose of 10 CFR 50.59?
To determine whether prior NRC approval is needed prior to implementing a change.
Does not determine whether the activity is safe, it is the responsibility of the utility to determine safety.
How do you know if a change requires 10 CFR 50.59 to be performed?
How are Chapter 15 events organized?
Organized according to different events that have similiar effects.
- 1. Increase in heat removal by the secondary system
- 2. Decrease in heat removal by the secondary system
- 3. Decrease in reactor coolant flow rate
- 4. Reactivity and power distribution anomolies
- 5. Inrease in RCS inventories
What are the frequency classifications of Ch. 15 events?
- Moderate Frequent Events - May occur during a calendar year
- Infrequent Events - May occur during plant lifetime
- Limiting Fault Events - Low probability of occurance during a plant lifetime
Explain the realationship between Safety Analysis Calculations, SADBs, and the UFSAR.
Safety Analyses --> performed via AORs to demonstrate NRC requirements have been met --> Reviewed and approved by NRC --> become part of the UFSAR
SADBs were created to help NFM engineers understand how to perform Safety analyses according to licensing history.