ML24339A020
| ML24339A020 | |
| Person / Time | |
|---|---|
| Issue date: | 12/04/2024 |
| From: | NRC/RGN-II |
| To: | |
| References | |
| Download: ML24339A020 (1) | |
Text
WBN NRC Exam 2024 Post-Exam Comments WBN ILT 2408 Written Exam - Question 6 The station identified an issue with question 6 of the written exam following a review of newly discovered technical information. The station has concluded there is no correct answer and recommends the question be removed from the exam.
Justification: The answer analysis was determined to be flawed following further review of technical information. The question asks the applicant to identify the reason the Residual Heat Removal (RHR) pump 1A is secured during a loss of Component Cooling System (CCS) flow. The answer key states steam hammer and appears to be based on the CAUTION in 1-AOI-14 Section 3.8 between step 1 (Stop the affected RHR Pump) and step 2 (Ensure affected RHR HX FCV closed).
The CAUTION does not apply to step 1 based on EPM-4, EOI Program User Guide, Section 4.1.3 which states In general, special messages apply to the step which they precede. A special message which precedes the first operator action step may also apply to the entire procedure. The CAUTION applies to step 2 which directs closing the affected RHR Heat Exchanger (HX) Flow Control Valve (FCV) to isolate RHR flow through the RHR HX and precludes the possibility of natural circulation. This is discussed in the System Description Document (Adjustment of Essential Raw Cooling Water (ERCW) flow rate to the CCS HXs or bypassing the RHR flow rate around the RHR Hxs will be used to regulate CCS HX outlet temperature) and in 1-SOI-74.01 Section 5.8.1.25 which contains the following caution.
This along with the below thermodynamic evaluation indicates there is no correct or acceptable answer.
Distractors B through D are as discussed in the exam submittal.
Thermodynamic Plausibility Evaluation:
Given the RCS temperature provided in the stem of the question of 240F, steam formation which is required for steam hammer is not possible due to the pressure head generated by the CCS surge tanks relative height above the CCS side of the RHR HX.
Discussion and Calculation:
Given the following plant conditions:
RCS temperature is 240F (from the stem of the question)
The RHR Heat Exchanger is located on elevation 713 of the Aux building.
The CCS Surge tank is located on elevation 757 of the Aux building. The calculation will conservatively assume that the surge tank is empty, and therefore the highest column of water would be at elevation 757. The question describes a loss of CCS flow thus there are no other dynamic forces acting on the CCS system.
In the below equation, where P is Pressure, is fluid density, is acceleration due to gravity, z is the fluid height, and gc is the gravitational constant, it is possible to calculate the CCS system pressure at the RHR Heat Exchanger.
Conservatively assuming CCS heats up to 240F, CCS from Ref.2 is conservatively assumed to be 59.10 lbm/ft3. (1 divided by specific volume of saturated water at 240F or 1/.016921 ft3/lbm.)
WBN NRC Exam 2024 Post-Exam Comments This is a conservative assumption since the water will not be saturated with the pressure calculated below.
The net difference in height, z, is the difference between 757 and 713, which is 44. Applying further conservatism, the pressure will be calculated based on the top height of the RHR HX, which is at elevation 728. Therefore, the net height difference for calculation purposes is 29.
=
Entering these values into the equation (where g=32 ft/sec2 and gc=32 ft lbm/lbf sec2), the stagnant pressure at the RHR HX is determined to be 11.90 psig.
= 59.10 3
x 32 2 x 29x 2 32 x 12 1442
= 11.90 Since the CCS surge tank is vented, normal atmospheric pressure at WBN of 14.4 psia (Ref WBN Drawing 0-47E235-50) is added to the static head to determine absolute pressure in the CCS side of the RHR HX or 11.90+14.4=26.30 psia.
From the Steam Tables and Properties of Saturated and Superheated Steam (Ref 2), the saturation temperature is determined to be 242.9 F which is higher than the theoretical maximum temperature in the RHR HX provided in the question information.
==
Conclusion:==
Since the given RCS temperature is below the saturation temperature for the CCS system provided in this question, it is not plausible that steam formation or steam hammer would occur in the CCS system at this time. Based on this newly discovered technical information, steam hammer is not a valid answer to the question.
Furthermore, the CAUTION referring to steam hammer is after the step in question and does not apply to stopping the RHR Pump as explained in EPM-4.
The remaining incorrect answers are still incorrect. Thus, there is no correct answer to the question as written. The station believes the question should be removed from the exam.
References:
Ref 1. 0-SOI-70.01, Component Cooling Water system operating instruction, Rev 44 Ref 2. 1-SOI-74.01, Residual Heat Removal System, Rev 26 Ref 3. Steam tables from the Sixth International Conference on the Properties of Steam for the ASME Research Committee published in the 2000 ASME Steam Tables Ref 4. EMP-4, EOI Program Users Guide, Rev 001 Ref 5. System Description SDD-N3-70-004
WBN NRC Exam 2024 Post-Exam Comments
WBN NRC Exam 2024 Post-Exam Comments
WBN ILT 2408 Written Exam - Question 68 The station identified an issue with question 68 of the written exam following a review of newly discovered technical information. The station has concluded the question lacks operational validity for Watts Bar Nuclear Station and recommends the question be removed from the exam.
Justification: The intent of question 68 is to determine the applicants understanding of required dosimetry when working in a Radiologically Controlled Area (RCA) at Watts Bar as specified by facility procedural guidance. The question asks the applicant to determine if a Pocket Ion Chamber (PIC) can or can not be used when working in the RCA. Fleet governance under NPG-SPP-05.1, Radiological Controls, does allow the use of a PIC as self-reading dosimetry (SRD) for entry into the RCA. Further investigation determined that a PIC is NOT used at Watts Bar for RCA entry.
Additional technical information was found under NPG-SPP-05.18, Radiological Work Permits (RWP), section 3.2.7 which requires that a SRD provide audible dose and dose rate alarms to be used. This procedural requirement can not be met with a PIC. In addition, NPG-SPP-05.18 contains no information supporting the use of a PIC for RCA entries. The NISP-RP-11, Nuclear Industry Standards and Process Radiological Fundamentals, also does not reference PICs and requires alarm set points to be established. The NISP documents are a nuclear industry standard procedure, and have been adopted and incorporated into the RP Fleet procedures, such as NPG-SPP-05.18. In interviews with the WBN RP manager and additional RP supervisors, it was determined that WBN does not have PICs and has no procedural direction on their use or the issuance of them. Radiation Protection would not allow the issuance of a PIC in lieu of an electronic SRD.
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Conclusion:==
Due to the newly discovered technical information, the station determined question 68 is not a valid question for WBN and recommends removal from the exam.
ES-1.2.B.8 specifies that the candidate should answer all questions based on actual plant operation, procedures, and references. Based on the current procedural guidance for the issuance of SRD at Watts Bar, an applicant would determine that a PIC can not be used for RCA entry when answering this question.
References:
NPG-SPP-05.1, Radiological Controls NPG-SPP-05.18, Radiological Work Permits, Rev 10 NISP-RP-11, Nuclear Industry Standards Process Radiological Fundamentals, Rev 1 WBN RWP Number 24000001, Rev 0, Unit 0 Aux building RCAs
DISTRACTOR ANALYSIS:
A.
Correct: The required dosimetry to enter an RCA Self-Reading Dosimeter (SRD). This can be accomplished by using an electronic dosimeter or a pocket ion chamber. Assigned DLR dosimeters are read at least semi-annually.
B.
Incorrect: Plausible because the first part is correct, required dosimetry to enter an RCA Self-Reading Dosimeter (SRD). This can be accomplished by using an electronic dosimeter or a pocket ion chamber. The second part is plausible because emergency planning dosimeters are read annually.
C.
Incorrect: Plausible because an electronic dosimeter is normally available. The second part is correct, assigned DLR dosimeters are read at least semi-annually.
D.
Incorrect: Plausible because an electronic dosimeter is normally available. The second part is plausible because emergency planning dosimeters are read annually.
A CORRECT ANSWER:
WBN NRC Exam 2024-301 Post-Exam Comments Error in JPM 3R and 3S, Evaluate valve stroke time testing results, Forms 3.2-1, Administrative Topics, Examination Level RO and SRO, regarding Technical Specifications for the JPM.
SR 3.6.6.6 states the following:
The Surveillance descriptions from Bases 3.5.2 for SR 3.5.2.2 and 3.5.2.4 apply as applicable to the RHR spray system.
SR 3.5.2.2 in part states the following:
Verifying the correct alignment for manual, power operated, and automatic valves in the ECCS flow paths provides assurance that the proper flow paths exist for ECCS operation. Based on the situation established in the JPM, the automatic operation of the RHR Pump mini flow recirculation valve is in question. Therefore, presumption of Operability cannot be maintained. This was correctly listed in the JPM as TS LCO 3.5.2 not met for the RHR pump and thus the low head injection piece of the overall ECCS Injection specification. There is historical data within the WBN Operations Narrative logs showing where we routinely state that TS LCO 3.6.6 is not met and required action Condition B is applicable due impacts to the Mini Flow Recirc valves under various conditions.
Based upon the above, the guide for that JPM should have listed TS LCO 3.6.6 as NOT met. An IDO that results in an RHR Pump being INOPERABLE due to the inability to meet the requirements of SR 3.5.2.2 (Automatic Valve Operation) should also result in TS LCO 3.6.6. not met.
Error in Scenario 1, Form 3.3-1, Scenario Outline, and Form 3.322, Required Operator Actions, regarding Technical Specifications for Event 4, SG 2 ADV 1-PCV-1-12 fails OPEN Scenario 1, Form 3.3-1, Scenario Outline, and Form 3.3-2, Required Operator Actions, Event 4, Technical Specification evaluation grading criteria included LCO 3.7.4, Atmospheric Dump Valves (ADVs), Condition A, as being required to be entered.
From the bases for TS 3.7.4:
From the bases for TS 3.7.4:
An ADV is considered OPERABLE when it is capable of controlled relief of the main steam flow and capable of fully opening and closing on demand. Also from the bases:
The ADVs are OPERABLE with a DC power source and control air available. Based on the verbiage in the associated SRs, controlled includes opened/closed AND/OR throttled to control and maintain the required cooldown to mitigate the chapter 15 accident analysis.
SR 3.7.4.1 Bases states:
To perform a controlled cooldown of the RCS, the ADVs must be able to be opened either remotely or locally and throttled through their full range. Based on this statement and in the event, one could not be controlled from the MCR, it would not preclude the ability to throttle the valve through its full range either locally or at the nitrogen control stations.
If an ADV fails open but can still be opened and closed from the MCR switch and or locally, the valve remains operable. Surveillances that are performed to satisfy SR 3.7.4.1 and 3.7.4.2 are 1-SI-1-902-A/B and 1-SI-1-906-A/B. These surveillances perform stroke times of the ADVs by using the pistol grip switches in the MCR not the controller.
Based upon the above, the guide for that scenario should have maintained that TS 3.7.4 was still met, even with the failed ADV hand switch in the CLOSE position.