ML25321A402
| ML25321A402 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 11/17/2025 |
| From: | NRC/RGN-II |
| To: | |
| References | |
| Download: ML25321A402 (1) | |
Text
Hatch 2025-301 Post Exam Comments SRO Question #98 Answer is KEYED for (C)
References:
- 31EO-TSG-001-0 v20.0
- 31EO-EOP-012-2 v8.0
Hatch 2025-301 Post Exam Comments Applicants Comment (Docket Numbers: 55-73493, 55-24510, 55-77816)
The question provided an initial set of conditions and asked for the appropriate direction of venting the primary containment along with the corresponding band.
The initial conditions are as follows:
Reactor Water Level - -165 inches, stable Torus Pressure - 52 psig, slowly rising Torus Level - 305 inches, stable Drywell Pressure - 54 psig, slowly rising Drywell Wide Range Radiation - 10,000 R/hr Based on NUREG-1021 Rev. 12, the applicant should not assume conditions that are not specified in the question unless they occur as a consequence of other conditions stated in the question.
Therefore, the following can be assumed by the applicant due to being a consequence of conditions stated in the question:
Drywell Spray is NOT in service due to >215 inches Torus Level (EOP-PC)
Core damage is or has occurred based on 10,000 R/hr (EALs)
The marked correct answer is to vent through the Drywell to maintain pressure in a 45-52 psig band. This comment is based on the subjective nature of the words appropriate decision in the question body and challenge of the technical information provided in the stem.
In the stem, Torus Water Level is stated to be 305 inches, stable. This condition, as stated, cannot be seen in the Main Control Room but in this question is specifically given to the applicant as a known plant value and trend. Without this information, the maximum indicated level available to the Main Control Room is 300 inches.
Several plant reference documents support venting through the Torus given the conditions in the stem of the question (Torus Water Level - 305 inches, stable).
According to 31EO-EOP-012-0 v1.2, Primary Containment Control Basis, Section 4.7 Primary Containment Pressure, torus water level is elevated and rising. Reducing primary containment pressure while the torus vent path is still available scrubs the discharge through the torus, reducing any radioactivity release. Delaying venting until after the torus vent penetration is submerged would necessitate use of the drywell vent path, raising the resulting radioactivity release. Pg 48 of 58
Hatch 2025-301 Post Exam Comments According to 31EO-EOP-101-2 v5.3, Emergency Containment Venting, Section 4.6 Containment Preservation Strategy, includes a Note that states Venting the Suppression Chamber is the preferred vent path whenever possible to maximize fission product scrubbing features of the suppression pool AND significantly reduce overall activity release and total offsite dose.
According to 31EO-TSG-001-0 v20.0, Plant Hatch Technical Support Guidelines, Section 3.20.3.2 Containment Venting After Core Damage, Torus vents should be used to vent the containment and to maintain the containment pressures low if possible, until Torus water level rises to the elevation of the vent.
Plant Technical Documents place the elevation of the Torus vents at 331 inches. See a portion of 31EO-TSG-001-0, Technical Support Guideline, Figure 2.7, v1.3 below:
Hatch 2025-301 Post Exam Comments See the discussion from 31EO-EOP-001-0 v1.2, EOP Basis Introduction and General Information, Section 4.6.13 Caution 12.
As written, this question assumes that the SRO evaluating this Caution is using indications available to them in the Main Control Room. As stated previously, 300 inches is the highest indicated level in the Main Control Room. If the stem of the question had said, Main Control Room Torus Water Level Indication - Upscale High, then the appropriate action would be to vent via the Drywell since exact Torus Water Level is unknown, and the Torus Vent path should be assumed lost.
However, this was not how the question was presented. Given the known information of Torus Water Level - 305 inches, stable, the appropriate action is to vent via the Torus. There remains 26 inches of air volume to vent from prior to the Torus Vent path becoming unavailable for use.
Applicants Recommendation: Change correct answer from (C) to (A).
Facility position on Applicant Comments: The facility licensee concurs with the applicants comment and recommendation. The facility recommends changing the answer from (C) to (A) based on a question with an unclear stem that led the applicant to misunderstand the intent of the question and the validity of the choices. NUREG-1021 Rev 12, ES-4.4 C.3.c states:
Despite the extensive reviews performed by both the NRC and the facility licensee before examination administration, it is possible that errors may be discovered only after an examination has been administered. The NRC will consider examination changes for the following types of errors, if identified and adequately justified by the facility licensee or an applicant:
Hatch 2025-301 Post Exam Comments
- a question with an unclear stem that confused the applicants or did not provide all the necessary information (to assist in determining whether an unclear stem confused the applicants, closely evaluate any applicant questions asked during the examination; also evaluate the question stem to determine whether the information provided could reasonably result in the applicant misunderstanding the intent of the question or the validity of the answer choices)
The facility reviewed the exam package of each applicant, and it is apparent to the facility that each applicant possessed and applied the appropriate knowledge of the EOPs to answer the question, as given. See screenshots of test packages below:
Hatch 2025-301 Post Exam Comments Facility has created and issued Technical Evaluation #1189317 to a member of the exam team to edit the stem of this question prior to further use at the facility.