ML24017A302

Post Exam Comments Resolution

ML24017A302
Person / Time
Site:	Limerick
Issue date:	12/14/2023
From:	Thomas Setzer NRC/RGN-I/DORS/OB
To:	Constellation Energy Generation
References
EPID L-2024-OLL-0000 2024301
Download: ML24017A302 (1)

Text

Post-Exam Comment Resolution - Limerick Written Exam Administered December 14, 2023 ADAMS Package ML23004A142

Written Exam Question # 17:

Unit 1 plant conditions:

• SE-1 (Remote Shutdown) has been entered and the MCR has been evacuated due to toxic gas

• Prior to evacuating the MCR, the Reactor was scrammed and All MSIVs were closed

• No other control room actions were completed

The Remote Shutdown Panel was staffed and SE-1 activities performed

• All RSP Transfer Switches are in EMERG

• Operators are controlling level with RCIC at 35 inches

• Controlling pressure with SRVs

A primary coolant leak in the drywell causes DW pressure to rise to 1.70 psig up slow.

With no additional action, what is the status of RCIC and HPCI 5 minutes later?

RCIC HPCI

A. Running Running

B. Running Tripped

C. Tripped Running

D. Tripped Tripped

Answer: B

Summary of Facility/Applicant Recommendation:

Question 17 is a question with an unclear stem that confused the applicants or did not provide all the necessary information. The state of RCIC (Running) is correct and is not disputed.

However, the leak in the drywell is not quantified and therefore leads to confusion on the status of the HPCI system. HPCI injection would occur due to drywell pressure exceeding 1.68 psig and would result in the reactor water level reaching +54 inches (HPCI Tripped). However, if the leak was beyond the capability of RCIC, reactor water level would drop to - 38 inches and cause HPCI to restart ( HPCI Running). Simulator plots have been provided to support this conclusion.

As a result, both Distractors A and B should be accepted as correct.

Applicant Performance on Question 17 Five out of 10 applicants selected a wrong Distractor. No applicant asked for any clarification of this question during the exam administration.

NRC Comment Resolution:

Question 17 will be deleted based upon ambiguity in the stem.

The facility/applicant have requested that HPCI Running (Distractor A) and HPCI Tripped (Distractor B) both be accepted as correct. These two distractors contain conflicting information; specifically, they describe a plant condition that cannot be true or exist at the same time (running and tripped). In accordance with NUREG 1021 ES-4.4, the NRC will not accept both answers as correct when both answers contain conflicting information.

The facility/applicant provided simulator data plots to support their explanation that HPCI would be running 5 minutes after drywell pressure rose to 1.70 psig. The stem states that drywell pressure rises to 1.70 psig up slow. The term up slow with respect to drywell pressure is not quantifiable; therefore, it is possible that a leak in excess of the capacity of RCIC could cause reactor level to decrease to the point of restarting HPCI. Since the stem did not provide clear enough information about the size of the leak, the question will be deleted.

Written Exam Question # 46:

Regarding the Standby Gas Treatment System, which of the following describes

1) The basis for the SGTS filter train and

2) The design feature to maintain filter efficiency

Basis for SGTS Filter Train Component to Maximize Filter Efficiency

A. Limit iodine and particulate concentration Electric Heaters in gases, prior to discharge

B. Limitin gases, iodine prior and to particulate discharge concentration Purge Air

C. Limit particulate concentration ONLY in Electric Heaters gases, prior to discharge

D. gases,Limit particulate prior to discharge concentration ONLY in Purge Air

Answer: A

Summary of Facility/Applicant Recommendation:

Question 46 is a question with an unclear stem that co nfused t he applicants or di d not pr ovide all the necessary i nformation. The first part of the question aski ng for the basis i s correct and i s not di sputed. However, the second part i s aski ng for t he design featur e that maintains o r maximizes f ilter e fficiency. Both E lectric H eaters and Pur ge Air a re described in Design Basis Document L-S-32, Standby Gas Treatment S ystem and R eactor E nclosure Recirculation System, Revision 9, S ection 3.3, Design Features, and their function is to lower r elative humidi ty, m aintain cl ean dry ai r and prevent co ndensation of w ater vapor on the ch arcoal f ilters.

Since the question does not sp ecifically ask when the desi gn feature would be used ( operation or s tandby), both opt ions i n the se cond par t of Distractors A and B w ould be correct for maintaining filter efficiency. As a result, both Distractors A and B should be accepted as correct.

Applicant Performance on Question 46 Four out o f 10 appl icants se lected a wrong D istractor. No applicant ask ed f or any clarification of this ques tion during th e exam ad ministration.

NRC Comment Resolution:

Both Distractors A and B are accepted as correct.

The question stem asks for the design feature that maintains (maximizes) filter efficiency. The NRC reviewed the Design Basis Document L-S-32 and found numerous instances where the electric heaters are specifically mentioned as designed to maintain charcoal filter efficiency.

Additionally, the specific design feature of Purge Air is to prevent condensation of water vapor on the filters when the system is in standby. This design feature would act to keep the filters dry, which would maintain or maximize the efficiency of the filters in a similar way as the heaters. Since the stem did not specify the mode (operating or standby), both Distractors A and B can be considered correct.

Written Exam Question # 92:

WHICH ONE of the following is required during Transient Response per OP-LG-103-102-1002, Strategies for successful Transient Mitigation?

A. An RO obtaining CRS permission prior to securing HPCI following automatic initiation

B. Shift Technical Advisor ensure identification of critical parameters

C. Shift Manager approval when action taken is necessary to prevent personal injury

D. An RO obtaining CRS permission to manually initiate RRCS during an ATWS

Answer: A

Summary of Facility/Applicant Recommendation:

There is addi tional t echnical information for Question 92 in procedure OP -LG-103-102-1002 t hat supports a ch ange t o the answ er key. While assignment of cr itical parameters i s the responsibility of the U nit Supervisor/CRS, D istractor B doe s no t state the S TA det ermines critical parameters t o be assi gned but t hat the S TA ensure identification of c ritical par ameters.

Specifically, st ep 5. 3 i dentifies the S TAs role to identify cr itical parameters for t rending. As a result, both Distractors A and B should be ac cepted as correct.

Applicant Performance on Question 92 2 out of 8 SRO applicants selected a wrong Distractor. No applicant aske d for any clarification of this ques tion during the exam ad ministration.

NRC C omment Resolution:

Both Distractors A and B are accept ed as co rrect.

The NRC r eviewed OP -LG-103-102-1002 and found that the Unit S upervisor/CRS i s identified as having t he responsibility to ensu re identification of cr itical parameters. Specificall y, st ep 4.2.2.4 states, in part, The determination of cr itical parameters to be assi gned is t he responsibility of the C ontrol R oom S upervisor. Additionall y, t he STA has an advisory rol e and provides input dur ing a t ransient in making this i dentification, which helps ensure the c ritical parameters ar e i dentified. Since the S TA hel ps en sure critical parameters are identified, bo th Distractors A and B ca n be considered correct.