ML23338A235

Hermes 2 General Audit Questions 7.1-2, 7.1-3, 7.1-4, 7.1-5, and 7.2-3

ML23338A235
Person / Time
Site:	Hermes  File:Kairos Power icon.png
Issue date:	12/04/2023
From:	Michael Orenak NRC/NRR/DANU/UAL1
To:	Peebles D, Gardner D Kairos Power
References
EPID L-2023-CPS-0000
Download: ML23338A235 (1)

Text

From:

Michael Orenak To:

Darrell Gardner; Drew Peebles Cc:

Pravin Sawant; Matthew Hiser; Edward Helvenston

Subject:

Hermes 2 Audit Questions 7.1-2, 7.1-3, 7.1-4, 7.1-5, and 7.2-3 Date:

Monday, December 4, 2023 12:51:00 PM Darrell and Drew,

Below is the fourth set of audit questions for the Hermes 2 General Audit. These questions are all specifically on instrumentation and control. The NRC staff would like to have a discussion regarding these questions and questions 7.2-1 and 7.2-2 (from the last audit question set) when Kairos is ready.

PSAR Section Request Number Request/Question 7.1, Instrumentation and Controls Overview 7.1-2 Table 7.2-3, Plant Control System Interlocks and Inhibits, of the Hermes 2 PSAR lists high radiation detection in the pebble handling area as an input for plant control system (PCS) interlocks or inhibits; however, the sensor input is not reflected in Figure 7.1-1, Instrumentation and Controls System Architecture. Please discuss if this sensor input should be on Figure 7.1-1. Additionally, please specify where these radiation monitor(s) would be located and any impact on the reactor when the setpoint for this interlock/inhibit is reached (on radiation) since the pebble flow is stopped.

7.1, Instrumentation and Controls Overview 7.1-3 Figure 7.1-1 indicates that the Power Generation System (PGS) instrumentation and control architecture is made up of six subsystems. However, there is limited information provided in the remainder of the PSAR regarding the Air Cooler Control System, Water Supply and Treatment Control System, and Auxiliary Steam Control System (e.g., not included in Table 3.6-1, Structures, Systems, and Components, or Section 9.9, Power Generation System, of the PSAR). Please clarify the relationships between these systems and the PGS and discuss the safety significance (if any) of these systems relative to plant operations (e.g., safety classification).

7.1, Instrumentation and Controls Overview 7.1-4 The separation of functions and interactions between the reactivity control system (RCS),

reactivity shutdown system (RSS), and the reactivity control and shutdown system (RCSS) is unclear throughout the PSAR:

a. RCS: RCS is defined as the reactivity control system in Figure 7.1-1.However, the RCS is also defined as the reactor

control system in Section 7.2.1, Description, and in the master list of acronyms in the table of contents.

b. RSS: In Figure 7.1-1 and Section 5.2.4, Testing and Inspection, the RSS is defined as reactivity shutdown system, but in Section 13.1.10.1, Recriticality or Reactor Shutdown System Failure, it is defined as the reactor shutdown system. RSS is not listed in the master list of acronyms in the table of contents.

Additionally, the RSS is listed on Figure 7.1-1 and discussed in Chapter 7, Instrumentation and Control Systems, as a component of the non-safety related PCS. However, the RSS is described in Section 13.1.10.1 as the safety-related portion of the RCSS and is relied upon to shut down the reactor. Section 4.2.2, Reactivity Control and Shutdown System, also discusses a safety-related portion of the RCSS but does not list the RSS.

c. RCSS: The RCSS appears to be a system that combines the RCS with the RSS functions, as discussed in Chapter 3, Design of Structures, Systems, and Components, Section 7.3.1, Description, and many other locations in PSAR. The relationships and interactions between the RCS, RSS, and the RCSS with regards to instrumentation and controls is unclear considering that the only system that is discussed in sufficient detail in Chapter 7 is the RCS in Section 7.2.1.1, Reactor Control System. Please clarify the relationships and interactions between RCS, RSS, and RCSS.

7.1, Instrumentation and Controls Overview 7.1-5 Figure 7.1-1 has multiple systems and control systems. Many of those systems are not listed in Table 3.6-1 (e.g., the intermediate loop thermal management system). The NRC staff would like to understand Kaiross criteria for having inclusion of systems listed on in Table 3.6-1.

7.2, Plant Control System 7.2-3 Section 7.2.1.5, Power Generation Control System, of the Hermes 2 PSAR lists the five capabilities of the Power Generation Control System. Table 3.6-1 and Section 9.9 of the Hermes 2 PSAR describe the Power Generation System as having three subsystems. The matching of these capabilities to the subsystems is not clear. The NRC staff would like to understand the descriptions of this system and subsystems and have a discussion regarding how they align and support each

other to provide a consistent understanding of the functions performed.

If you have any questions or need clarifications on the questions before the discussion, please do not hesitate to contact me. This email will be added to ADAMS and will be made public.

Mike

Michael D. Orenak, Project Manager Advanced Reactor Licensing Branch 1 (UAL1)

NRR - Division of Advanced Reactors and Non-Power Production and Utilization Facilities (DANU) 301-415-3229 Michael.Orenak@nrc.gov