ML23303A103
| ML23303A103 | |
| Person / Time | |
|---|---|
| Issue date: | 10/24/2023 |
| From: | Shurtleff C Holtec International SMR |
| To: | Sayoc E NRC/NRR/DNRL/NLIB |
| Sayoc, M.,NRR/DRA/DNRL (301) 415-4084 | |
| References | |
| Download: ML23303A103 (5) | |
Text
From: Clark Shurtleff To: Andrew Brenner; Manny Sayoc Cc: Carolyn Lauron; Shilp Vasavada; Michelle Hayes; India Banks; Sean McCloskey; Jodine Vehec; Andy Arend
Subject:
[External_Sender] RE: Staff Questions for 10/25 Meeting on Risk Significance Methodology Date: Tuesday, October 24, 2023 10:18:11 AM Attachments: Holtec Responses - Presubmittal Meeting Questions.docx Manny, our responses to the questions are provided in the attached document.
Clark From: Andrew Brenner <a.brenner@holtec.com>
Sent: Monday, October 23, 2023 10:43 AM To: Manny Sayoc <Emmanuel.Sayoc@nrc.gov>; Clark Shurtleff <C.Shurtleff@holtec.com>
Cc: Carolyn Lauron <Carolyn.Lauron@nrc.gov>; Shilp Vasavada <Shilp.Vasavada@nrc.gov>; Michelle Hayes <Michelle.Hayes@nrc.gov>; India Banks <India.Banks@nrc.gov>
Subject:
RE: Staff Questions for 10/25 Meeting on Risk Significance Methodology Thanks Manny, I appreciate the early feedback from you and the staff. Ill pass these questions on to our staff and make sure we address them in the meeting, if not also providing written responses prior.
- Thanks, Andrew From: Manny Sayoc <Emmanuel.Sayoc@nrc.gov>
Sent: Monday, October 23, 2023 8:24 AM To: Andrew Brenner <a.brenner@holtec.com>; Clark Shurtleff <C.Shurtleff@holtec.com>
Cc: Carolyn Lauron <Carolyn.Lauron@nrc.gov>; Shilp Vasavada <Shilp.Vasavada@nrc.gov>; Michelle Hayes <Michelle.Hayes@nrc.gov>; India Banks <India.Banks@nrc.gov>
Subject:
Staff Questions for 10/25 Meeting on Risk Significance Methodology Importance: High CAUTION: This email came from a source OUTSIDE of Holtec!!
Do not click any links or open any attachments unless you trust the sender and know the contents to be safe.
Clicking links or opening attachments could lead to infecting your computer or Holtecs servers with malicious viruses.
Hello Andrew and Clark, Please see the following questions from the staff for our subject meeting in 10/25. We dont necessarily need a written response, although they are welcome, but perhaps a discussion on these items at our public meeting.
Presubmittal Meeting Questions
- 1. Although not stated, it appears that Holtec's proposed risk significance determination methodology is similar to the approved risk significance determination methodology from NuScale Topical Report TR-0515-13952-NP-A (ML16284A016).
- a. Are there any differences between NuScales approved risk significance determination methodology and Holtecs proposed methodology?
- b. Is Holtec familiar with the limitations and conditions that the NRC staff placed on the approval of NuScales risk significance determination methodology? These limitations and conditions may be applicable to Holtecs risk significance determination methodology approval. Does Holtec have any concerns related to this?
i.Describe the applicability of the methodology based on the baseline risk since the baseline risk is not yet available to the NRC.
ii.Describe inputs to the determination of risk significance that ensure the process is risk-informed and not risk-based (e.g., defense-in-depth, safety margins, performance monitoring).
- 2. The approved risk significance determination methodology in NuScale Topical Report TR-0515-13952-NP-A is based, in part, on a CDF on the order of 1E-7 per year.
- a. What are the estimated baseline CDF and LRF values for the Holtec SMR-160+ design?
- 3. Are the risk thresholds selected by Holtec based on the cumulative risk from all hazards, or will risk thresholds be based on risks from individual hazards?
I will introduce the key Staff at the meeting that will review the Risk Significance TR, but the leads are Stacey Rosenberg and Steve Alferink, from our Div or Risk Assessment. Shilp Vasavada is the branch chief for the lead review branch. You will likely interact with them mostly during the meeting.
Thank You, Very Respectfully, Emmanuel Manny Sayoc Safety and Environmental Project Manager NRR/DNRL/NLIB 301-415-4084 emmanuel.sayoc@nrc.gov The information contained herein is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material from Holtec International. If you are not the intended recipient, you must not keep, use, disclose, copy or distribute this email without the author's prior permission. Further, review, retransmission, dissemination, or other use of this information in whole or part for any
other purpose by persons outside the recipient's organization is strictly prohibited unless explicit authorization to such effect has been issued by the sender of this message. Holtec International policies expressly prohibit employees from making defamatory or offensive statements and infringing any copyright or any other legal right by Email communication. Holtec International will not accept any liability in respect of such communications. Holtec International has taken precautions to minimize the risk of transmitting software viruses, but we advise you to carry out your own virus checks on any attachment to this message. Holtec International cannot accept liability for any loss or damage caused by software viruses. If you are the intended recipient and you do not wish to receive similar electronic messages from us in the future then please respond to the sender to this effect.
Presubmital Meeng Quesons - Risk Signi"cance Methodology
- 1. Although not stated, it appears that Holtec's proposed risk signi"cance determinaon methodology is similar to the approved risk signi"cance determinaon methodology from NuScale Topical Report TR-0515-13952-NP-A (ML16284A016).
- a. Are there any dierences between NuScales approved risk signi"cance determinaon methodology and Holtecs proposed methodology?
There are no dierences between Holtecs proposed risk signi"cance determinaon methodology and NuScales approved risk signi"cance determinaon methodology.
- b. Is Holtec familiar with the limitaons and condions that the NRC sta placed on the approval of NuScales risk signi"cance determinaon methodology? These limitaons and condions may be applicable to Holtecs risk signi"cance determinaon methodology approval. Does Holtec have any concerns related to this?
Holtec has reviewed the limitaons and condions placed on the approval of NuScales risk signi"cance determinaon methodology. Holtec believes the limitaons and condions apply to Holtecs risk signi"cance determinaon methodology as well. Holtec has no concerns with the limitaons and condions.
- i. Describe the applicability of the methodology based on the baseline risk since the baseline risk is not yet available to the NRC.
Based on current PSA models (including at-power and LPSD Level 1 and 2 models of internal and external events), the Holtec SMR baseline CDF is expected to be on the order of 10-7/yr and the baseline LRF is expected to be on the order of 10-8/yr. This is signi"cantly smaller than the typical CDF and LRF of the current operang "eet and is similar to the NuScale reactor module CDF and LRF. This supports Holtecs determinaon that the methodology is applicable to the Holtec SMR design.
ii. Describe inputs to the determinaon of risk signi"cance that ensure the process is risk-informed and not risk-based (e.g., defense-in-depth, safety margins, performance monitoring).
PRA risk insights will be considered along with determinisc approaches and defense-in-depth concepts such that Holtec is ulizing a risk-informed rather than a solely risk-based approach. In short, these new criteria will be implemented in the same way the tradional RG 1.200 relave risk criteria would have been.
- 2. The approved risk signi"cance determinaon methodology in NuScale Topical Report TR-0515-13952-NP-A is based, in part, on a CDF on the order of 1E-7 per year.
- a. What are the esmated baseline CDF and LRF values for the Holtec SMR-160+ design?
Based on current PSA models (including at-power and LPSD Level 1 and 2 models of internal and external events), the Holtec SMR baseline CDF is expected to be on the order of 10-7/yr and the baseline LRF is expected to be on the order of 10-8/yr.
- 3. Are the risk thresholds selected by Holtec based on the cumulave risk from all hazards, or will risk thresholds be based on risks from individual hazards?
The criteria apply to the full-scope PRA, including all hazards and operang modes, and both CDF and LRF. The thresholds are applied at the single unit level; the absolute RAW thresholds apply to the aggregated risk across all hazards, and the FV thresholds apply individually to each hazard group and mode of plant operaon, and individually to CDF and LRF.