ML25050A113
| ML25050A113 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 01/23/2025 |
| From: | Marlone Davis Energy Northwest |
| To: | Heather Gepford NRC/RGN-IV/DORS/OB |
| References | |
| GO-25-031 | |
| Download: ML25050A113 (1) | |
Text
Docusign Envelope ID: BAC14A41-3782-4ABC-8D75-3AEF02C64DD6 THE ENCLOSED EXAMINATION MATERIALS SHALL BE WITHHELD FROM PUBLIC DISCLOSURE AS AGREED UPON WITH THE NRC.
GO-25-031 Thomas Farina U.S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Michael W. Davis Columbia Generating Station P.O. Box 968, MD 1028 Richland, WA 99352-0968 Ph. 509.377.4281 l F. 509.377.8662 mwdavis@energy-northwest.com
Subject:
ADDRESEE ONLY: COLUMBIA GENERATING STATION, DOCKET NO.
50-397 POST-EXAMINATION PACKAGE.
Dear Mr. Farina:
The Columbia Station initial license examination was completed on January 23, 2025. In accordance with NUREG-1021, Operator Licensing Examination Standards for Power Reactors, ES-4.4, section B.7, the following post-examination information has been electronically transferred via Box:
- 1. Each applicants original answer sheet (clean).
- 2. Each applicants original answer sheet (graded).
- 3. Each applicants examination cover sheet.
- 4. Master written examinations.
- 5. Master written examination answer key, annotated to indicate any changes made while administering and grading the examinations.
- 6. Questions asked by the applicants and answers given to the applicants during written examination administration.
- 7. All examination administration/post-examination review comments made by the facility licensee. Note that applicants provided no post-examination review comments.
- 8. Written examination seating chart.
- 9. Written examination performance analysis or high-miss questions, with recommendations for substantive changes.
Note that the submission of Form 1.3-1, Examination Security Agreement, will be delayed to complete collection of post-examination signatures. These forms will be submitted via Box at a later date.
Station management concurs with the exam results as detailed in the post-examination package. No new regulatory commitments are made in this letter. If you require additional information, please contact Kelly Robertson, Exam Group Supervisor, at (509) 377-4070.
Respectfully, Michael W. Davis Director, Training
Issue: Question SRO-83 as given correct answer is D. Following analysis, correct answer is C.
Analysis: SRO-83 requires applicants to utilize knowledge of ABN-BACKPRESSURE. This includes automatic actions and immediate actions which applicants need to have memorized as well as general awareness of paths that will be taken in subsequent actions. Per the stem of the question, reactor power is 56% and main turbine output is 680MWe, and condenser backpressure is 3.5 in Hg and up 0.5 in Hg per minute. The main turbine trip setpoint at 680MWe is roughly 6.5 in Hg, meaning the turbine trip would occur in six minutes without any operator action.
The keyed answer D states the CRS should direct a power reduction in accordance with PPM 3.2.4 Fast Power Reduction. This is in accordance with step 4.3 of ABN-BACKPRESSURE. However, this action would be adverse for several reason. First, reducing reactor power would reduce turbine loading and cause a change to the turbine trip setpoint associated with backpressure. At 560MWe, the turbine trip setpoint reaches its lowest value of 5.5 in Hg, meaning the time to a turbine trip could quickly be reduced to four minutes. Second, at an initial reactor power of 56%, the power reduction would not constitute a relatively fast and easy flow back in recirculation flow. Control rod movement would need to be evaluated and rods would be inserted to help with the power reduction. This task takes more time than the operating crew would have available to them before the automatic turbine trip would occur.
Distractor C gives the applicant the option to scram the reactor and trip the main turbine. This would be the prudent action and is found in ABN-BACKPRESSURE step 3.1. This step directs these actions when reactor power is GT 25% and a condenser backpressure trip is imminent. The applicant is faced with deciding if they can correct the issue within a limited time frame or take the actions associated with taking the plant offline. In this case, without a way to correct the rising backpressure and a main turbine trip only six minutes away, taking this action described in distractor C is the correct response and C should be selected by the applicant, not D.
Question as written:
Reactor power is 56%.
Main Turbine output is currently 680MWe.
A small Condenser leak results in degrading Backpressure in the Main Condenser.
Current condenser backpressure: 3.5 in Hg, up 0.5 in Hg per minute.
What action(s) should the CRS direct?
A. Trip the main turbine ONLY.
B. Scram the reactor and close MSIVs.
C. Scram the reactor and trip the main turbine.
D. Reduce reactor power in accordance with PPM 3.2.4, Fast Power Reduction.
Answer:
DC Explanation: Distractor C and D explanations have been corrected in blue.
Explanation:
A. Incorrect. Plausible since tripping the main turbine is one of the correct actions for the conditions given. Plausibility is enhanced since this would be the only action if reactor power were less than 25%. However, since reactor power is 56%, the CRS should direct a reactor scram in addition to tripping the main turbine.
B. Incorrect. Plausible since a reactor scram is one of the correct actions for the condition given.
Plausibility is enhanced since closing the MSIVs would be a correct action if Circulating Water (CW) were completely lost or Main Condenser backpressure was approaching 20 in Hg.
However, these conditions are not present. Therefore closing the MSIVs is the incorrect action.
C. Correct. In accordance with ABN-Backpressure, step 3.1, if reactor power is GT 25% and main condenser backpressure back pressure trip is imminent, the CRS should direct a reactor scram and main turbine trip. ABN-BACKPRESSURE step 3.1 states if reactor power is GT 25% and a turbine trip is imminent on backpressure, the CRS should direct a reactor scram and main turbine trip. At a reduced reactor power level and main turbine load as described in the stem, the trip setpoint is lower than at full power. The applicant should understand the reduced setpoint means theres less time to investigate the cause of the rising backpressure and less time to attempt maneuvering the plant to preclude the impending turbine trip. Therefore, the CRS should direct the reactor scram and main turbine trip. In accordance with attachment 7.1, Turbine Backpressure Limits, the main turbine will trip at 6.59 in Hg, which is LT 1 minute.
Therefore, the CRS should direct a reactor scram and main turbine trip.
D. Incorrect. Plausible as the applicant may calculate the approximate time to the turbine trip as being six minutes under the given initial conditions in the stem. The action to reduce power will however move the plant closer to a turbine trip on backpressure and ultimately result in approximately four minutes until the turbine trip. Further, at the reduced reactor power level that is given in the stem, control rod insertion would be required as part of the power maneuvering.
This evolution takes longer than a recirculation flow reduction and it is likely that the turbine trip would occur automatically during this lengthy evolution. Therefore it would not be prudent to attempt a reactor power reduction as it would likely complicate the casualty. Plausible since reducing power is proscribed in step 4.3 of ABN-Backpressure if a turbine trip has not occurred and is not imminent. However, the conditions given in the stem indicate that a turbine trip is imminent. Therefore, actions of step 3.1 must be directed.
Evaluation of high miss questions for ILC-26 NRC Exam.
RO-6: 46.2% pass rate 6 applicants selected C, 1 applicant selected B. Question is correct as written.
Weak Area: ABN-CR-EVAC Applicants demonstrated a weakness in knowledge of ABN-CR-EVAC. Specifically, knowing that RCIC would operate normally regardless of if it is started from the control room or the remote shutdown panel should drive the applicant to the correct answer.
Additionally, RCIC is not fire protected and operation could be erratic if the control room evacuation is due to a fire.
RO-35: 23.1% pass rate 3 applicants selected A, 3 applicants selected C, 4 applicants selected D. Question is correct as written.
Weak Area: PPM 3.1.2 Startup Flow Chart Applicants demonstrated a weakness in both what constitutes good overlap data between SRMs and IRMs and what action to take if overlap cannot be successfully verified.
RO-36: 23.1% pass rate 9 applicants selected B, 1 applicant selected D. Question is correct as written.
Weak Area: SRM detector operation Applicants demonstrated a weakness in what region of the gas-filled detector characteristic curve SRMs operate in. Generically speaking a detector operating in the proportional region could be used as an SRM. However, CGS operates SRM detectors in the ionization region.
RO-37: 38.5% pass rate 5 applicants selected A, 3 applicants selected D. Question is correct as written.
Weak Area: PRNM system Applicants demonstrated a knowledge deficiency concerning the interface between the reactor recirculation flow input and APRM STP readings. Additionally, failures of the recirculation transmitters and the subsequent effects on plant indications, alarms, and actuations was not well demonstrated by the applicants. One applicant noted that a full APRM display could be included to enhance the question. The information given in the stem has been determined to be sufficient without additional information or references.
RO-52: 30.8% pass rate 9 applicants selected C. Question is correct is written.
Weak Area: ABN-SW Applicants demonstrated a weakness with entry conditions for ABN-SW. One applicant noted that changing the stem to replace the word fails, when referencing the status of SW-V-29, with the word indicates could make the intent of the question clearer.
Future use of this question will include this change.
SRO-83: 0% pass rate.
All 9 applicants selected C. Correct answer is D. Question has been analyzed and answer C has been deemed to be the correct answer. Further discussion and justification has been included on a separate attachment.
SRO-90 44.4% pass rate.
4 applicants selected C, 1 applicant selected A. Question is correct is written.
Weak Area: CCH Chiller operation Applicants demonstrated a weakness with the interface between WCH (normal control room cooling medium) and CCH (emergency control room cooling medium). With WCH available and the CCH system supplying control room cooling, a fault or adverse condition with CCH can be mitigated by placing WCH cooling back in service. This is done by returning the CCH chiller control switch to the OFF position.
Questions Asked During Exam Time Question
Response
0810 Question RO Is the answer based solely on the reference?
0815 - You have all the information needed to answer the question.
0823 Question RO Is the answer based on the reference or PPM 5.2.1 actions?
0825 - You have all the information needed to answer the question.
0840 Question RO Are indicating lights for SW-V-29 both lit?
0845 - Yes both indicating lights are lit. Updated all applicants and made a note on the white board at the front of the room.
0936 Question RO What is obviate?
0936 - Asked applicant if they would like a dictionary, applicant declined use of dictionary.
0955 Question RO What is the status of indicating lights above RWCU-V-1 and RWCU-V-4?
0958 - Red light is lit and green light is not lit for both valves.
1001 Question SRO Is RCIC required to be in service for level control?
1003 - You have all the information needed to answer the question.
1003 Question SRO What is the noun name for RPS-EPA-3A?
1010 - EPN for RPS-EPA-3A is RPS Trip Sys Bus A electr. Prot. Assembly. Updated all applicants and made a note on the white board.
1010 Question RO Use of dictionary for obviate.
1011 - Candidate utilized dictionary for obviate.
1016 Question SRO What is the noun name for DSA-ENG-C/2C?
1025 - EPN for DSA-ENG-C/2C is Diesel Eng For DSA-C-2C. Updated all applicants and made a note on the white board.
1022 Question SRO Do any other actions go with the first part of the distractors for A and B?
1024 - You have all the information needed to answer the question.
1040 Question SRO What is the noun name for SR 3.7.5.1?
1042 - There are no noun names for SRs (surveillance requirements).
1050 Question SRO Is LPCS available?
1055 - You have all the information needed to answer the question.
1139 Question RO Does initially mean before DEH responds?
1141 - You have all the information needed to answer the question.
1155 Question SRO Is PT 220 on CMS-TR-5 the normal red digital indication used in the main control room?
1157 - You have all the information needed to answer the question.