SECY-19-0040, VR-SECY-19-0040: Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring (PRM-50-111; NRC-2015-0124)

VR-SECY-19-0040: Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring (PRM-50-111; NRC-2015-0124)

ML19284C673
Person / Time
Issue date:	10/11/2019
From:	Commissioners NRC/OCM
To:	Annette Vietti-Cook NRC/SECY
References
SECY-19-0040, SRM-SECY-19-0040 VR-SECY-19-0040
Download: ML19284C673 (48)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 11, 2019 SECRETARY COMMISSION VOTING RECORD DECISION ITEM: SECY-19-0040 TITLE: DENIAL OF PETITION FOR RULEMAKING ON POWER REACTOR IN-CORE MONITORING (PRM-50-111; NRC-2015-0124)

The Commission acted on the subject paper as recorded in the Staff Requirements Memorandum (SRM) of October 11 , 2019.

This Record contains a summary of voting on this matter together with the individual vote sheets, views and comments of the Commission.

~dn-~

Annette L. Vietti-Cook Secretary of the Commission

Enclosures:

1. Voting Summary

2. Commissioner Vote Sheets cc: Chairman Svinicki Commissioner Baran Commissioner Caputo Commissioner Wright OGC EDO PDR

VOTING

SUMMARY

- SECY-19-0040 RECORDED VOTES NOT APPROVED DISAPPROVED ABSTAIN PARTICIPATING COMMENTS DATE Chrm. Svinicki X X 09/27/19 Cmr. Baran X X 05/31/19 Cmr. Caputo X X 09/27/19 Cmr. Wright X X 09/26/19

POLICY ISSUE NOTATION VOTE RESPONSE SHEET TO: Annette Vietti-Cook, Secretary FROM: CHAIRMAN SVINICKI

SUBJECT:

SECY-19-0040: Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring (PRM-50-111; NRC-2015-0124)

Approved XX Disapproved _ Abstain _ Not Participating _

Comments: Below XX Attached XX None I approve the staff's request to deny PRM-50-111 and to publish the notice of denial in the Federal Register, subject to the edits indicated in the attached .

SI ATURE DA i ,Z,l719 Entered on "STARS" Yes _ JNo _

KLS edits [7590-01-P]

NUCLEAR REGULATORY COMMISSION 10 CFR Part 50

[Docket No. PRM-50-111 ; NRC-2015-0124)

Power Reactor In-Core Monitoring AGENCY: Nuclear Regulatory Commission.

ACTION: Petition for rulemaking; denial.

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) is denying a petition for rulemaking (PRM), dated March 13, 2015 , submitted by Mark Edward Leyse (petitioner).

The petition was docketed by the NRC on April 24, 2015, and assigned Docket No.

PRM-50-111 . The petitioner requested that the NRC require all holders of operating licenses for nuclear power plants to operate them with in-core temperature-monitoring devices (e.g., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core. The NRC is denying the petition because current regulations provide a sufficient level of safety, such that additional requirements for in-core temperature-monitoring devices as specified in the petition are not needed .

DATES : The docket for the petitio n for rulemaking, PRM-50-111 , is closed on [INSERT DATE OF PUBLICATION OF PUBLICATION IN THE FEDERAL REGISTERJ .

ADDRESSES : Please refer to Docket ID NRC-2015-0124 when contacting the NRC

about this petition. You may obtain publicly-available information related to this action by any of the following methods:

• Federal Rulemaking Web Site: Go to http://www.regulations .gov and search for Docket ID NRC-2015-0124. Address questions about NRC dockets to Carol Gallagher; telephone: 301-415-3463; e-mail: Carol. Gallagher@nrc.gov. For technical questions, contact the individual listed in the FOR FURTHER INFORMATION CONTACT section of this document.

• NRC's Agencywide Documents Access and Management System (ADAMS): You may obtain publicly-available documents online in the ADAMS Public Documents collection at http://www.nrc.gov/reading-rm/adams .html. To begin the search, select "Begin Web-based ADAMS Search ." For problems with ADAMS, please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, ill 301-415-4737, or by e-mail to pdr.resource@nrc.gov. For the convenience of the reader, instructions about obtaining materials referenced in this document are provided in Section Ill , "Availability of Documents," of this document.

• NRC's PDR: You may examine and purchase copies of public documents at the NRC's PDR, Room 01-F21, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852.

FOR FURTHER INFORMATION CONTACT: James O'Driscoll, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission , Washington DC 20555-0001 ; telephone: 301-415-1325; e-mail : James.O'Driscoll@nrc.gov .

SUPPLEMENTARY INFORMATION:

2

I. The Petition Section 2.802 of title 10 of the Code of Federal Regulations (10 CFR), "Petition for rulemaking-requirements for filing ," provides an opportunity for any interested person to petition the Commission to issue, amend, or rescind any regulation . The NRC received a petition dated March 13, 2015, from Mark Edward Leyse and assigned it Docket No. PRM-50-111. The NRC published a notice of docketing in the Federal Register on July 16, 2015 (80 FR 42067). The NRC did not request public comment on PRM-50-111 because the staff had sufficient information to review the issues raised in the petition .

The NRC identified three issues that provide the bases for the request in PRM-50-111 :

1. Measurement of the temperatures at various locations within the reactor core would enable nuclear power plant operators to better understand the condition of the core under normal and transient conditions, and to more clearly foresee incipient or impending damage to the reactor core.

2. The use of in-core temperature-monitoring devices is needed in boiling-water reactors .

3. The use of in-core temperature-monitoring devices would satisfy recommendations regarding enhanced reactor instrumentation made in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century:

3

The Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident,"

dated July 12, 2011 (ADAMS Accession No. ML111861807).

The petitioner requested that the NRC amend its regulations at 10 CFR part 50, "Domestic Licensing of Production and Utilization Facilities," to require all holders of operating licenses for nuclear power plants to operate them with in-core temperature-monitoring devices (e.g., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core. The petitioner stated that the use of the devices would enable nuclear power plant operators to accurately measure in-core temperatures, thereby providing crucial information to help them track the progression of core damage and manage the accident (for examf)le~. by indicating the correct time to transition from emergency operating procedures to implementing severe accident management guidelines).

The petitioner stated that installing in-core temperature-monitoring devices would satisfy the recommendations in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century," dated July 12, 2011 , regarding enhanced reactor instrumentation . Specifically, the petitioner referenced the following from the report:

[A] new and dedicated portion of the regulations would allow the Commission to recharacterize its expectations for safety features beyond design basis more clearly and more positively as 'extended design-basis' requirements.

The petitioner asserted that a new regulation is needed , requiring that a wide range of in-core temperatures be accurately measured in the event of a severe accident.

II. Reasons for Denial 4

The NRC addressed a substantial portion of the request in this petition in its response to a previous petition . PRM-50-105 was submitted on February 28, 2012, and the NRC published a notice of receipt and request for comment in the Federal Register on May 23, 2012 (77 FR 30435). In PRM-50-105, the petitioner requested that the NRC require all holders of operating licenses for nuclear power plants to operate them with in-core thermocouples at different elevations and radial positions throughout the reactor core to enable the operators to accurately measure a large range of in-core temperatures in nuclear power plant steady-state and transient conditions. The NRC limited the scope of the review of PRM-50-105 to only the use of in-core thermocouples in pressurized-water reactors because that was the primary focus of the requests in PRM-50-105, although boiling-water reactors were mentioned . The petition was denied on September 12, 2013 (78 FR 56174).

As discussed below, the NRC is denying PRM-50-111 because the petitioner does not justify the need for a regulation that requires the use of in-core temperature-monitoring devices in nuclear power plants.

NRC's Response to Issue 1:

In its denial of PRM-50-105, the NRC evaluated whether, in the event of a severe accident, in-core thermocouples would enable nuclear power plant operators to accurately measure in-core temperatures better than core exit thermocouples, and would provide crucial information to help operators manage the accident. In PRM 111, the petitioner reiterated this assertion and expanded on the previous request by including other instrument types that might be used in the measurement of in-core temperatures (e.g. , thermoacoustic sensors).

5

The NRC denied PRM-50-105 because the NRC concluded that knowledge of core temperatures at various elevations and radial positions would not enhance safety or change operator action . Furthermore, core-exit thermocouples, despite known limitations, are sufficient to allow nuclear power plant operators to take timely and effective action in the event of an accident. Core-exit thermocouples in pressurized-water reactors provide an indication of initial core damage during accident conditions and provide the necessary indication to make operational decisions with respect to the approach to imminent core damage.

The current suite of instrumentation used in pressurized-water reactors , which includes core-exit thermocouples, provides sufficient information to determine the need for operator action well before the onset of significant core damage. Other indications include reactor coolant system level and containment pressure. A more comprehensive description of the applications of core-exit thermocouples is provided in NRC's denial of PRM-50-105, Issue 1. In its denial of PRM-50-105, the NRC concluded that there is no need for more accurate measurement of temperatures throughout the core in pressurized-water reactors. The NRC concludes that the reasons for that decision remain valid and are applicable to PRM-50-111 .

In PRM-50-111 , the petitioner discusses core temperature measurement devices other than thermocouples. The NRC evaluated this information and concludes that the nature of the device is not relevant to the decision of whether or not to require the use of in-core temperature instrumentation .

As in the denial of PRM-50-105, the NRC has determined that precise in-core temperatures would not provide information that would enable nuclear power plant operators to better respond to and manage a reactor accident.

6

The NRC therefore concludes that more accurate and precise temperature distribution information within the reactor core that would be provided by such instrumentation is not necessary fefto provide adequate protection to the health and safety of the public or nuclear power plant staff, nor would it provide a substantial safety enhancement at nuclear power plants. Therefore, installation of such instrumentation need not be required by regulation.

NRC's Response to Issue 2:

The petitioner asserted that in the event of a severe accident at a boiling-water reactor, in-core temperature-monitoring devices would be more accurate and immediate for detecting inadequate core cooling and core uncovery than readings of the reactor water level, reactor pressure, containment pressure, or wetwell water temperature. The petitioner also asserted that, after the onset of core damage, water level indicators in boiling-water reactors are unreliable.

The NRC determ ined that the current means to detect and respond to inadequate core cooling is already anticipatory in nature, and emergency operator actions would be no different if in-core temperature-monitoring devices were present.

Therefore, no safety benefit would result from the availability of such devices.

Existing boiling-water reactor emergency operating procedures (EOPs) do not require operator assessment of core cooling. Instead, operators use specific parametric data such as the water level, containment pressure, containment radiation , and reactor pressure) in conjunction with the EOP actions to respond to the event. Under accident conditions, reactor vessel water level is an acceptable indication of conditions relating to imminent core damage, and drywell radiation monitors are typically the primary method 7

for determining the presence of core damage and severe accident management guideline entry conditions. For boiling-water reactors, severe accident management guideline entry conditions are also tied to parameters such as water level, containment hydrogen concentration , and component failures . If reactor water level is unknown or conditions render water level instrumentation unreliable, then the EOPs require the operators to proactively flood the reactor vessel. In addition , the EOPs for boiling-water reactors describe steam cooling as a method of cooling the core when there is insufficient water to cover the core, typically available when water level is at or above two-thirds of core height. This method allows additional time to restore reactor coolant injection and reduce the likelihood of emergency reactor depressurization, which would be necessary for the injection of low pressure sources.

The intent of NRC's regulations is to prevent or minimize significant core damage. The detection of inadequate core cooling and actual core uncovery is not necessary for managing emergency and accident scenarios. Nuclear power plant operators are directed by EOPs to take proactive emergency operating actions based on the indication of parameters that are anticipatory to actual inadequate core cooling conditions, while the instruments reading those parameters are still functioning within their acceptably-accurate performance ranges. If significant core damage were to occur, water level instrumentation and in-core temperature instrumentation (if installed) would no longer be relied upon for operator action .

The NRC has determined that boiling-water reactor operators do not need in-core temperature-monitoring devices to safely navigate emergency and accident scenarios. Because the use of water level instrumentation is sufficient to inform operator actions prior to significant core damage, the NRC finds that the information representing 8

the temperature within specific core locations wouldooes not provide an improvement in the prevention of an accident or the mitigation of the consequences of an accident. The NRC has further determined that having the core temperature data would not provide any additional safety margins in managing post accident or severe accident conditions.

Therefore, the NRC concludes that more accurate and precise temperature distribution within the reactor core that would be provided by such instrumentation is not necessary fefto provide adequate protection of the health and safety of the public or nuclear power plant staff, nor would it provide a substantial safety enhancement at nuclear power plants. Therefore. ijnstallation of such instrumentation need not be required by regulation.

NRC's Response to Issue 3:

The petitioner stated that in-core temperature-monitoring devices would satisfy the July 12, 2011 , near-term task force report recommendations for enhanced reactor instrumentation . As justification for this claim, the petitioner cited Recommendation 8, in Section 4.2 .5 of the report, which recommends strengthening and integrating onsite emergency response capabilities such as emergency operating procedures, severe accident management guidelines and extensive damage mitigation guidelines. The petitioner also cited Volume 10 of NUREG-1635, "Review and Evaluation of the Nuclear Regulatory Commission Safety Research Program : A Report to the U.S. Nuclear Regulatory Commission," dated October 31 , 2012 . The petitioner quoted sections from pages 11 and 12 of this report, in which the NRG-Advisory Comm ittee on Reactor Safeguards stated that the ~NRC recognized the need for enhanced reactor instrumentation , that such instrumentation would help clarify the transition points of 9

various onsite emergency response capabilities, and that the NRC was in the process of adding this to the implementation of the near-term task force report recommendations.

The petitioner gave, as an example of a transition point, the point at which nuclear power plant operators should transition from EOPs to implementing severe accident management guidelines.

The staff proposed plans to the Commission for resolving open near-term task force recommendations in SECY-15-0137, "Proposed Plans for Resolving Open Fukushima Tier 2 and 3 Recommendations," dated October 29, 2015. In SECY 0137, the staff described how remaining open recommendations from the near-term task force report should be resolved. The staff specifically assessed the need for enhanced reactor instrumentation for beyond-design-basis conditions in Enclosure 5 of SECY 0137. The staff recommended that the Commission not pursue additional regulatory action beyond the current requirements , including those imposed by orders EA-12-049, "lssl!anse of Order to--Modifyin9 Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," and EA-12-051 , "Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation." In SRM-SECY 0137, dated February 8, 2016, the Commission approved the staff's closure plan for these items. On January 24, 2019, in SRM-M190124A, the Comm ission directed agency staff to publish a final rule based on lessons learned from the March 2011 accident at Japan's Fukushima Daiichi plant. The final rule will make generically applicable the requirements from the above orders, taking into account fessons learned in the implementation of the orders and feedback received from stakeholders.

As discussed under Issues 1 and 2, the NRC evaluated the potential contribution that more accurate and precise temperature information would have on improving 10

nuclear power plant safety for both boiling-water reactor and pressurized-water reactor plants. The NRC has determined that the availability of such information would not improve operator actions to prevent or mitigate a reactor accident. The NRC finds that the Commission's conclusions in SRM-SECY-15-0137 apply fef..to the instrumentation proposed by the petitioner. The NRC concludes that more accurate and precise temperature distribution information that would be provided by such instrumentation is not necessary fefto provide adequate protection to the health and safety of the public or nuclear power plant staff, nor would it provide a substantial safety enhancement at nuclear power plants. Therefore, installation of such instrumentation need not be required by regulation .

Ill. Availability of Documents The documents identified in the following table are available to interested persons as indicated . For more information on accessing ADAMS , see the ADDRESSES section of this document.

Date Document ADAMS Accession Number/Web site /Federal Register Citation Petition Documents March 13, 2015 PRM-50-111 - Petition for ML151138143 Rulemaking from Mark E.

Leyse Regarding In-Core Temperature Monitoring at Nuclear Power Plants July 16, 20 15 Federal Register notice: 80 FR 42067 Petition for Rulemaking, Notice of Docketing, Power Reactor In-Core Monitorinq 11

February 28, 2012 Petition for Rulemaking ML12065A215 submitted Mark Edward Leyse, on PRM-50-105, Request NRC Require all Holders of Operating Licenses for Nuclear Power Plants to Operate with In-Core Thermocouples at Different Elevations and Radial Positions May 23, 2012 Federal Register notice: 77 FR 30435 Petition for Rulemaking ;

Receipt and Request for Comment, In-core Thermocouples at Different

• Elevations and Radial Positions in Reactor Core September 12, 2013 Federal Register notice: 78 FR 56174 Petition for rulemaking ;

Denial, In-core Thermocouples at Different Elevations and Radial Positions in Reactor Core Other Documents October 30, 1979 The Need for Change, the httos://tmi2kml.inl.oov/Docume Legacy of TMI : Report of nts/Common/Presidents the President's Commission Commission, (Main Re11ort) on the Accident at Three The Need For Change, The Mile Island Lef~cj of TMl-2 (1979 30 . d Commented [A1]: Displayed text for hyperlink edited to replace "%20" with a space for readability. The space will be July 12, 2011 SECY-11-0093 -

Enclosure:

interpreted by web browsers as "%20" because that is the ML111861807 URL encoding for a space; the %20 is retained in the The Near Term Task Force hyperlink corresponding to this text.

Review of Insights from the Fukushima Dai-lchi Accident October 31, 2012 NUREG-1635, Volume 10, ML12311A417 "Review and Evaluation of the Nuclear Regulatory Commission Safety Research Program: A Report to the U.S. Nuclear Reciulatorv Commission" October 29, 2015 SECY-15-0137, "Proposed ML15254A006 Plan for Resolving Open Fukushima Tier 2 and 3 Recommendations" 12

March 12, 2012 EA-12-049 "Issuance of ML12054A735 Order te---Modify]ng Licenses with F.!3.egard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" March 12, 2012 EA-12-051, "Order Modifying ML12056A044 Licenses with F.!3.egard to Reliable Spent Fuel Pool Instrumentation" February 8, 2016 SRM-SECY-15-0137 - ML16039A175 Proposed Plans for Resolving Open Fukushima Tier 2 and 3 Recommendations January 24, 2019 SRM-M190124A: Affirmation ML19024A073 Session-SECY-16-0142:

Final Rule: Mitigation of Beyond-Design-Basis Events (RIN 3150-AJ49)

- -IV. Conclusion For the reasons cited in Section II of this document, the NRC is denying PRM-50-111 . The NRC finds that no improvement in safety would result from amending its regulations to require the installation of in-core temperature-monitoring devices.

Therefore, installation of such instrumentation need not be required by regulation .

Dated at Rockville, Maryland , this xxth day of Xxxxx, 2019.

For the Nuclear Regulatory Commission.

Annette L. Vietti-Cook, 13

Secretary of the Commission.

14

POLICY ISSUE NOTATION VOTE RESPONSE SHEET TO: Annette Vietti-Cook, Secretary FROM: Commissioner Baran

SUBJECT:

SECY-19-0040: Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring (PRM-50-111; NRC-2015-0124)

Approved X Disapproved - - Abstain - - Not Participating - -

COMMENTS: Below - - Attached X None - -

Entered in "STARS" Yes X No DATE

Commissioner Saran's Comments on SECY-19-0040, "Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring" I appreciate Mr. Leyse's thoroughly researched and well-argued petition for rulemaking, which highlights the limitations of core-exit thermocouples in pressurized water reactors.

Despite these acknowledged limitations, I do not believe that a rulemaking to require all operating nuclear power plants to install in-core temperature monitoring devices is necessary at this time for two main reasons .

First, I am not persuaded that the additional information available from in-core temperature monitoring devices would lead operators to take different actions in an emergency.

Nuclear power plant Severe Accident Management Guidelines (SAMGs) "are developed based on the recognition that [core-exit thermocouples] could differ from actual core temperatures." 1 In the event of an emergency, the transition to SAMGs would occur before the core was uncovered and fuel temperatures spiked, based on other available indications, including reactor water, reactor pressure, containment pressure, and containment radiation levels. As a result, the NRC staff has reasonably concluded that having access to precise in-core temperatures would not result in more effective operator actions during a severe accident. 1 Second, the installation and maintenance of in-core temperature monitoring devices would result in higher radiation doses to plant workers. I am reluctant to require licensees to take actions that would increase worker doses in the absence of a demonstrated offsetting increase in plant safety.

Therefore , I approve the NRC staff's recommendation to deny the petition for rulemaking . I also approve publication of the Federal Register notice announcing this decision, subject to the attached edits.

1 U.S. NRC , In-Core Thermocouples at Different Elevations and Radial Positions in Reactor Core, FR 56174 , 56175 (Sept. 12, 2013) .

JMB edits [7590-01-P]

NUCLEAR REGULATORY COMMISSION 10 CFR Part 50

[Docket No. PRM-50-111; NRC-2015-0124)

Power Reactor In-Core Monitoring AGENCY: Nuclear Regulatory Commission.

ACTION: Petition for rulemaking ; denial.

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) is denying a petition for rulemaking (PRM), dated March 13, 2015 , submitted by Mark Edward Leyse (petitioner).

The petition was docketed by the NRC on April 24, 2015, and assigned Docket No.

PRM-50-111 . The petitioner requested that the NRC require all holders of operating licenses for nuclear power plants to operate them with in-core temperature-monitoring devices (e.g., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core. The NRC is denying the petition because current regulations provide a sufficient level of safety, such that additional requirements for in-core temperature-monitoring devices as specified in the petition are not needed.

DATES: The docket for the petition for rulemaking , PRM-50-111 , is closed on [INSERT DATE OF PUBLICATION OF PUBLICATION IN THE FEDERAL REGISTER] .

ADDRESSES: Please refer to Docket ID NRC-2015-0124 when contacting the NRC

about this petition . You may obtain publicly-available information related to this action by any of the following methods:

• Federal Rulemaking Web Site: Go to http://www.regulations.gov and search for Docket ID NRC-2015-0124. Address questions about NRC dockets to Carol Gallagher; telephone: 301 -415-3463; e-mail: Carol.Gallagher@nrc.gov. For technical questions, contact the individual listed in the FOR FURTHER INFORMATION CONTACT section of this document.

• NRC's Agencywide Documents Access and Management System (ADAMS): You may obtain publicly-available documents online in the ADAMS Public Documents collection at http://www.nrc.gov/reading-rm/adams.html. To begin the search , select "Begin Web-based ADAMS Search ." For problems with ADAMS , please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, 301 -415-4737, or by e-mail to pdr.resource@nrc.gov. For the convenience of the reader, instructions about obtaining materials referenced in this document are provided in Section Ill , "Availability of Documents," of this document.

• NRC's PDR: You may examine and purchase copies of public documents at the NRC's PDR, Room 01-F21, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852 .

FOR FURTHER INFORMATION CONTACT: James O'Driscoll, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington DC 20555-0001 ; telephone: 301 -415-1325; e-mail: James.O'Driscoll@nrc.gov.

SUPPLEMENTARY INFORMATION:

2

I. The Petition Section 2.802 of title 10 of the Code of Federal Regulations (10 CFR), "Petition for rulemaking-requirements for filing ," provides an opportunity for any interested person to petition the Commission to issue, amend, or rescind any regulation. The NRC received a petition dated March 13, 2015, from Mark Edward Leyse and assigned it Docket No. PRM-50-111 . The NRC published a notice of docketing in the Federal Register on July 16, 2015 (80 FR 42067). The NRC did not request public comment on PRM-50-111 because the staff had sufficient information to review the issues raised in the petition.

The NRC identified three issues that provide the bases for the request in PRM-50-111 :

1. Measurement of the temperatures at various locations within the reactor core would enable nuclear power plant operators to better understand the condition of the core under normal and transient conditions, and to more clearly foresee incipient or impending damage to the reactor core.

2. The use of in-core tem'perature-monitoring devices is needed in boiling-water reactors.

3. The use of in-core temperature-monitoring devices would satisfy recommendations regarding enhanced reactor instrumentation made in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century:

The Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident,"

dated July 12, 2011 (ADAMS Accession No. ML111861807).

The petitioner requested that the NRC amend its regulations at 10 CFR part 50, "Domestic Licensing of Production and Utilization Facilities ," to require all holders of 3

operating licenses for nuclear power plants to operate them with in-core temperature-monitoring devices (e.g., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core. The petitioner stated that the use of the devices would enable nuclear power plant operators to accurately measure in-core temperatures, thereby providing crucial information to help them track the progression of core damage and manage the accident (for example, by indicating the correct time to transition from emergency operating procedures to implementing severe accident management guidelines).

The petitioner stated that installing in-core temperature-monitoring devices would satisfy the recommendations in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century," dated July 12, 2011 , regarding enhanced reactor instrumentation. Spesifisally, the polilionor roferonsed the fellowing from !he report:

IA] now and dodisalod portion of tho rogl-.tlaliens wol-.tld allow tho Commission lo rocharastorizo its expectations for safely featl-Jros eoyond design easis more clearly and more positi*,ely as 'extended design easis' re{ll-.tiromonls.

tfhe petitioner asserted that a new regulation is needed, requiring that a wide range of in-core temperatures be accurately measured in the event of a severe accident.I { Commented [BJ1]: Move to the end of the prior paragraph.

II. Reasons for Denial As discussed below, the NRC is denying PRM-50-111 because the petitioner does not demonstrate the need for a regulation that requires the use of in-core temperature-monitoring devices in nuclear power plants . The NRC addressed a 4

substantial portion of the request in this petition in its response to a previous petition.

PRM-50-105 was submitted on February 28, 2012, and the NRC published a notice of receipt and request for comment in the Federal Register on May 23, 2012 (77 FR 30435). In PRM-50-105, the petitioner requested that the NRC require all holders of operating licenses for nuclear power plants to OJ)erate-tl=lem -wi#lhave in-core thermocouples at different elevations and radial positions throughout the reactor core to enable the operators to accurately measure a large range of in-core temperatures in nuclear power plant steady-state and transient conditions . The NRC limited the scope of the review of PRM-50-105 to only the use of in-core thermocouples in pressurized-water reactors because that was the primary focus of the requests in PRM 50 105that petition ,

although boiling-water reactors were mentioned . +R&-f)f etition PRM-50-105 was denied on September 12, 2013 (78 FR 56174).

As discussed eelGW;-lt-le NRG is denying PRM 50 111-eecause the petitioner does not justify the need for a regulation that requires the use of in core ternperature rnonitoring de\*ices in nuclear power plants.

NRC's Response to Issue 1:

In its denial of PRM-50-105, the NRC evaluated whether, in the event of a severe accident, in-core thermocouples would enable nuclear power plant operators to accurately measure in-core temperatures better than core exit thermocouples, and would provide crucial information to help operators manage the accident. In PRM 111 , the petitioner reiterated this assertion and updated expanded on the previous request by including other instrument types that might be used in the measurement of in-core temperatures (e.g., thermoacoustic sensors).

The NRC previously denied PRM-50-105 because the NRC concluded that 5

knowledge of core temperatures at various elevations and radial positions would not significantly enhance safety or change operator action . Fllrti=lermore, c_Qore-exit thermocouples, despite known limitations, are sufficient to allow nuclear power plant operators to take timely and effective action in the event of an accident. Coro exit ti=lermocollples i!n pressurized-water reactorsi..!!:!fil'. provide an indication of initial core damage during accident conditions and provide the necessary indication to make operational decisions with respect to the approach to imm inent core damage.

The current suite of instrumentation used in pressurized-water reactors , which includes core-exit thermocouples , provides sufficient information to determine the need for operator action well before the onset of significant core damage. Other indications include reactor coolant system level and containment pressure. A more comprehensive description of the applications of core-exit thermocouples is provided in NRC's denial of PRM-50-105, Issue 1. In its denial of PRM-50-105, the NRC concluded that there is no need for more accurate measurement of temperatures throughout the core in pressurized-water reactors. The NRC concludes that the reasons for that decision remain valid and are applicable to PRM §Q 111 the current petition .

In PRM §Q 111 , ti he petitioner discusses core temperature measurement devices other than thermocouples. The NRC evaluated this information and concludes that the nature of the device is not relevant to the decision of whether or not to require the use of in-core temperature instrumentation.

As in the denial of PRM-50-105, the NRC has determined that precise in-core temperatures would not change operator actions or provide information that would enable nuclear power plant operators to better respond to and manage a reactor accident.

The NRC therefore concludes that more accurate and precise temperature 6

distribution information within the reactor core that would be provided by such instrumentation is not necessary for adequate protection of 11:le--public health and safety8f-ffiJGlear f)ewer f)laRt staff, ner and would notit provide a substantial safety enhancement at nuclear power plants. Therefore, installation of such instrumentation need not be required by regulation.

NRC's Response to Issue 2:

The petitioner asserted that in the event of a severe accident at a boiling-water reactor, in-core temperature-monitoring devices would be more accurate and immediate for detecting inadequate core cooling and core uncovery than read ings of the reactor water level , reactor pressure, containment pressure, or wetwell water temperature. The petitioner also asserted that, after the onset of core damage, water level indicators in boiling-water reactors are unreliable.

The NRC determined that the cu rrent means to detect and respond to inadequate core cooling is already anticipatory in nature, and emergency operator actions would be no different if in-core temperature-monitoring devices were present.

Therefore, no significant safety benefit would result from the availability of such devices.

Existing boiling-water reactor emergency operating procedures (EOPs) do not require operator assessment of core cooling . Instead, operators use specific parametric data such as the water level , containment pressure, containment radiation , and reactor pressure) in conjunction with the EOP actions to respond to the event. Under accident cond itions, reactor vessel water level is an acceptable indication of conditions relating to imminent core damage, and drywell radiation monitors are typically the primary method for determining the presence of core damage and severe accident management guideline entry conditions. For boiling-water reactors , severe accident management 7

guideline entry conditions are also tied to parameters such as water level , containment hydrogen concentration , and component failures . If reactor water level is unknown or conditions render water level instrumentation unreliable, then the EOPs require the operators to proactively flood the reactor vessel. In addition , the EOPs for boiling-water reactors describe steam cooling as a method of cooling the core when there is insufficient water to cover the core, typically available when water level is at or above two-thirds of core height. This method allows additional time to restore reactor coolant injection and reduce the likelihood of emergency reactor depressurization , which would be necessary for the injection of low pressure sources.

The intent of NRC's regulations is to prevent or minimize significant core damage. Ttie detestion of inadeq1cJate sore sooling and ast1cJal sore 1cJnsovery is not nesessary for FRanaging eFRergensy and assident ssenarios. Nuclear power plant operators are directed by EOPs to take proactive emergency operating actions based on the indication of parameters that are anticipatory to actual inadequate core cooling conditions, while the instruments reading those parameters are still functioning within their acceptably-accurate performance ranges. If significant core damage were to occur, water level instrumentation and in-core temperature instrumentation (if installed) would no longer be relied upon for operator action.

The NRC has determined that boiling-water reactor operators do not need in-core temperature-monitoring devices to safely navigate emergency and accident scenarios. Because the use of water level instrumentation is sufficient to inform operator actions prior to significant core damage, the NRC finds that the information representing the temperature within specific core locations does not provide a significantn improvement in the prevention or mitigation of the consequences of an accident. The NRC has further determined that having the core temperature data would not provide 8

any additional safety margins in managing post accident or severe accident conditions.

Therefore, the NRC concludes that more accurate and precise temperature distribution within the reactor core that would be provided by such instrumentation is not necessary for adequate protection of the public health and safety and er mJclear 13ewer 13lant staff, OOF-would notit provide a substantial safety enhancement at nuclear power plants.

Installation of such instrumentation need not be required by regulation .

NRC's Response to Issue 3:

The petitioner stated that in-core temperature-monitoring devices would satisfy the July 12, 2011 , near-term task force report recommendations for enhanced reactor instrumentation . To supportAs j1oJstificatien for this claim, the petitioner cited Re\'.X'mmendation 8, in Section 4.2.5 of the report, which recommends strengthening and integrating onsite emergency response capabilities such as emergency operating procedures, severe accident management guidelines and extensive damage mitigation guidelines. The petitioner also cited Volume 10 of NUREG-1635 , "Review and Evaluation of the Nuclear Regulatory Commission Safety Research Program : A Report to the U.S. Nuclear Regulatory Commission ," dated October 31 , 2012. The petitioner quoted sections from pages 11 and 12 of this report, in which the NRC stated that the agency recognized the need for enhanced reactor instrumentation, that such instrumentation would help clarify the transition points of various onsite emergency response capabilities, and that the NRC was in the process of adding this to the implementation of the near-term task force report recommendations. The petitioner gave, as an example of a transition point, the point at which nuclear power plant operators should transition from EOPs to implementing severe accident management guidelines.

9

The staff proposed plans to the Commission for resolving open near-term task force recommendations in SECY-15-0137, "Proposed Plans for Resolving Open Fukushima Tier 2 and 3 Recommendations," dated October 29, 2015. In SECY 0137, the staff described how remaining open recommendations from the near-term task force report should be resolved . The staff specifically assessed the need for enhanced reactor instrumentation for beyond-design-basis conditions in Enclosure 5 of SECY 0137. The staff recommended that the Commission not pursue additional regulatory action beyond the current requirements, including those imposed by orders EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," and EA-12-051 , "Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation." In SRM-SECY 0137, dated February 8, 2016, the Commission approved the staffs closure plan for these items. ~ a r y 24 , 2Q19, in SRM M1QQ124.A., the Commission directed agency staff to fHiblish a final rule based on lessons learned from the March 2011 accident at Ja13an's F1JklJshima Daiichi 13lant. The final rule will make generically a1313licable the reqlJirements from the above orders, taking into acco1,1nt lessons learned in the im13lementation of the orders and feedback received from stakeholders .

As discussed under Issues 1 and 2, the NRC evaluated the potential contribution that more accurate and precise temperature information would have on improving nuclear power plant safety for both boiling-water reactor and pressurized-water reactor plants. The NRC has determ ined that the availability of such information would not improve operator actions to prevent or mitigate a reactor accident. The NRC finds that the Commission's conclusions in SRM-SECY-15-0137 apply for the instrumentation proposed by the petitioner. The NRC concludes that more accurate and precise temperature distribution information that would be provided by such instrumentation is 10

not necessary for adequate protection of the public health and safety and or n1Jclear 13owor 13lant staff, nor would noti-t provide a substantial safety enhancement at nuclear power plants. Therefore, installation of such instrumentation need not be required by regulation.

Ill. Availability of Documents The documents identified in the following table are available to interested persons as indicated . For more information on accessing ADAMS, see the ADDRESSES section of this document.

Date Document ADAMS Accession Number/Web site /Federal Register Citation Petition Documents March 13, 2015 PRM-50-111 - Petition for ML15113B143 Rulemaking from Mark E.

Leyse Regarding In-Core Temperature Monitoring at Nuclear Power Plants July 16, 2015 Federal Register notice: 80 FR 42067 Petition for Rulemaking, Notice of Docketing, Power Reactor In-Core Monitorinq February 28, 2012 Petition for Rulemaking ML12065A215 submitted Mark Edward Leyse, on PRM-50-105, Request NRC Require all Holders of Operating Licenses for Nuclear Power Plants to Operate with In-Core Thermocouples at Different Elevations and Radial Positions May 23, 2012 Federal Register notice: 77 FR 30435 Petition for Rulemaking; Receipt and Request for Comment, In-core 11

Thermocouples at Different Elevations and Radial Positions in Reactor Core September 12, 2013 Federal Register notice: 78 FR 56174 Petition for rulemaking; Denial, In-core Thermocouples at Different Elevations and Radial Positions in Reactor Core Other Documents October 30, 1979 The Need for Change, the htt12s://tmi2kml .inl .gov/Docume Legacy of TMI: Report of nts/Com man/Presidents %20C the President's Commission om mission,%20(Main%20Re12 on the Accident at Three ort)%20The%20Need%20For Mile Island %20Change,%20The%20Leg ac~%20of%20TMI -

2%20/ 1979-10-30\. odf July 12, 2011 SECY-11-0093 -

Enclosure:

ML111861807 The Near Term Task Force Review of Insights from the Fukushima Dai-lchi Accident October 31 , 2012 NUREG-1635, Volume 10, ML12311A417 "Review and Evaluation of the Nuclear Regulatory Commission Safety Research Program: A Report to the U.S. Nuclear Regulatory Commission" October 29, 2015 SECY-15-0137, "Proposed ML15254A006 Plan for Resolving Open Fukushima Tier 2 and 3 Recommendations" March 12, 2012 EA-12-049 "Issuance of ML12054A735 Order to Modify Licenses with regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" March 12, 2012 EA-12-051, "Order Modifying ML12056A044 Licenses with regard to Reliable Spent Fuel Pool Instrumentation" February 8, 2016 SRM-SECY-15-0137 - ML16039A175 Proposed Plans for Resolving Open Fukushima Tier 2 and 3 Recommendations 12

January 24, 2019 SRM-M190124A: Affirmation ML19024A073 Session-SECY-16-0142:

Final Rule: Mitigation of Beyond-Design-Basis Events (RIN 3150-AJ49)

IV. Conclusion For the reasons cited in Section II of this document, the NRC is denying PRM-50-111 . The NRC finds that no significant improvement in safety would result from amending its regulations to require the installation of in-core temperature-monitoring devices. Therefore, installation of such instrumentation need not be required by regulation .

Dated at Rockville, Maryland, this xxth day of Xxxxx, 2019.

For the Nuclear Regulatory Commission.

Annette L. Vietti-Cook, Secretary of the Commission .

13

POLICY ISSUE NOTATION VOTE RESPONSE SHEET TO: Annette Vietti-Cook, Secretary FROM: Commissioner Caputo ;_'

SUBJECT:

SECY-19-0040: Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring (PRM-50-111; NRC-2015-0124)

Approved X Disapproved _ Abstain _ Not Participating _

Comments: Below Attached X None Entered in STARS Yes-X-No- - -

DATE

AXC Comments on SECY-19-0040 In SECY-19-0040, the staff seeks Commission approval to publish the enclosed Federal Register notice denying petition for rulemaking (PRM)-50-111, submitted to the U.S. Nuclear Regulatory Commission (NRC) by Mr. Mark Edward Leyse.

This petition requests that the NRC require all holders of operating licenses for nuclear power plants to install in-core temperature monitoring devices (e.g., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core.

The petitioner previously submitted a related petition to the NRC. On February 28, 2012, Mr. Leyse requested similar actions in a petition that the NRC docketed as PRM-50-105 (ADAMS Accession No. ML12065A215). In that petition, the petitioner's request was limited tq pressurized-water reactors and the usage of core-exit thermocouples in those plants . The NRC published a notice denying PRM-50-105 on September 12, 2013 (78 FR 56174).

In PRM-50-111 , the petitioner expanded on the previous request in PRM 50-105 to include boiling-water reactors and other instrument types that might be used in the measurement of in-core temperatures.

Three issues were identified in PRM-50-111 . A summary of the issues and the staff's corresponding evaluation is *provided below.

(1) Measurement of the temperature at various locations within the reactor core would enable nuclear power plant operators to better understand core conditions under normal and transient conditions and more clearly foresee incipient or impending damage to the reactor core.

The staff determined that a more accurate measurement of temperatures throughout the core -

such as that described in PRM-105-111 - would not improve operator decision-making and ,

therefore, would provide no safety benefit.

(2) The use of in-core temperature-monitoring devices is needed in boiling-water reactors. The petitioner asserted that, in the event of a severe accident in a boiling-water reactor, in-core temperature-monitoring devices would be more accurate and immediate for detecting inadequate core cooling and core uncovery than readings of the reactor water level , reactor pressure, containment pressure, or wetwell water temperature.

The staff determined that the use of in-core temperature-monitoring devices for the detection of inadequate core cooling and actual core uncovery is not necessary for managing emergency and accident scenarios in these plants. Therefore, no safety benefit would result from the availability of such devices in boiling-water reactors.

(3) The use of in-core temperature-monitoring devices would satisfy recommendations regarding enhanced reactor instrumentation made in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century: The Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," dated July 12, 2011 (ADAMS Accession No. ML111861807).

On October 29, 2015, the staff submitted SECY-15-0137, Proposed Plans for Resolving Open Fukushima Tier 2 and 3 Recommendations (ADAMS Accession No. ML15254A006). This paper addressed the enhanced reactor instrumentation recommendations and recommended that the Commission not pursue additional regulatory action beyond the current requirements . The Commission approved the staff's position in the staff requirements memorandum to SECY 0137, dated February 8, 20 16 (ADAMS Accession No. ML16039A175). The petitioner's request that the NRC require the use of in-core temperature-monitoring instruments is within the scope of that decision .

I approve the staff's request to publish the notice denying PRM-50-111 (Enclosure 1).

POLICY ISSUE NOTATION VOTE RESPONSE SHEET TO: Annette Vietti-Cook, Secretary FROM: Commissioner Wright

SUBJECT:

SECY-19-0040: Denial of Petition for Rulemaking on Power Reactor In-Core Monitoring {PRM-50-111; NRC-2015-0124)

Approved _lL Disapproved _ Abstain _ Not Participating_

Comments: Below X Attached X None I approve the staffs recommendation to deny PRM-50-111. I also approve publication of the Federal Register notice denying PRM-50-111, subject to the attached edits.

Entered in STARS Yes ..7' No- - -

DATE ~ t

DAW Edits (7590-01-P]

NUCLEAR REGULATORY COMMISSION 10 CFR Part 50

[Docket No. PRM-50-111; NRC-2015-0124]

Power Reactor In-Core Monitoring AGENCY: Nuclear Regulatory Commission.

ACTION: Petition for rulemaking; denial.

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) is denying a petition for rulemaking (PRM), dated March 13, 2015, submitted by Mark Edward Leyse (petitioner).

The petition was docketed by the NRC on April 24, 2015, and assigned Docket No.

PRM-50-111 . The petitioner requested that the NRC require all holders of operating licenses for nuclear power plants to operate them with in-core temperature-monitoring devices (e.g ., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core. The NRC is denying the petition because current regulations provide a sufficient level of safety, such that additional requirements for in-core temperature-monitoring devices as specified in the petition are not needed.

DATES: The docket for the petition for rulemaking , PRM-50-111, is closed on [INSERT DATE OF PUBLICATION OF PUBLICATION IN THE FEDERAL REGISTER].

ADDRESSES: Please refer to Docket ID NRC-2015-0124 when contacting the NRC

about this petition. You may obtain publicly-available information related to this action by any of the following methods:

• Federal Rulemaking Web Site: Go to https://www.regulations.gov and search for Docket ID NRC-2015-0124. Address questions about NRC dockets to Carol Gallagher; telephone: 301-415-3463; e-mail: Carol.Gallagher@nrc.gov. For technical questions, contact the individual listed in the FOR FURTHER INFORMATION CONTACT section of this document.

• NRC's Agencywide Documents Access and Management System (ADAMS): You may obtain publicly-available documents online in the ADAMS Public Documents collection at https://www.nrc.gov/reading-rm/adams.html. To begin the search, select "Begin Web-based ADAMS Search." For problems with ADAMS , please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, 301-415-4737, or by e-mail to pdr.resource@nrc.gov. For the convenience of the reader, instructions about obtaining materials referenced in this document are provided in Section Ill , "Availability of Documents," of this document.

• NRC's PDR: You may examine and purchase copies of public documents at the NRC's PDR, Room 01-F21, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852.

FOR FURTHER INFORMATION CONTACT: James O'Driscoll, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington DC 20555-0001; telephone : 301-415-1325; e-mail: James.O'Driscoll@nrc.gov.

2

SUPPLEMENTARY INFORMATION :

I. The Petition Section 2.802 of title 10 of the Code of Federal Regulations (10 CFR), "Petition for rulemaking-requirements for filing ," provides an opportunity for any interested person to petition the Commission to issue, amend, or rescind any regulation . The NRG received a petition dated March 13, 2015, from Mark Edward Leyse and assigned it Docket No. PRM-50-111 . The NRC published a notice of docketing in the Federal Register on July 16, 2015 (80 FR 42067). The NRC did not request public comment on PRM-50-111 because the staff had sufficient information to review the issues raised in the petition.

The NRC identified three issues that provide the bases for the request in PRM-50-111:

1. Measurement of the temperatures at various locations within the reactor core would enable nuclear power plant operators to better understand the condition of the core under normal and transient conditions , and to more clearly foresee incipient or impending damage to the reactor core.

2. The use of in-core temperature-monitoring devices is needed in boiling-water reactors .

3. The use of in-core temperature-monitoring devices would satisfy recommendations regarding enhanced reactor instrumentation made in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century:

The Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident,"

dated July 12, 2011 (ADAMS Accession No. ML111861807).

3

The petitioner requested that the NRC amend its regulations at 10 CFR part 50, "Domestic Licensing of Production and Utilization Facilities," to require all holders of operating licenses for nuclear power plants to operate them with in-core temperature-monitoring devices (e.g ., thermoacoustic sensors or thermocouples) located at different elevations and radial positions throughout the reactor core. The petitioner stated that the use of the devices would enable nuclear power plant operators to accurately measure in-core temperatures, thereby providing crucial information to help them track the progression of core damage and manage tAe-an accident (for example, by indicating the correct time to transition from emergency operating procedures to implementing severe accident management guidelines).

The petitioner stated that installing in-core temperature-monitoring devices would satisfy the recommendations in the near-term task force report, "Recommendations for Enhancing Reactor Safety in the 21st Century," dated July 12, 2011, regarding enhanced reactor instrumentation . Specifically, the petitioner referenced the following from the report:

[A] new and dedicated portion of the regulations would allow the Commission to recharacterize its expectations for safety features beyond design basis more clearly and more positively as 'extended design-basis' requirements.

The petitioner asserted that a new regulation is needed, requiring that a wide range of in-core temperatures be accurately measured in the event of a severe accident.

II.Reasons for Denial The NRC addressed a substantial portion of the request in this petition in its response to a previous petition. PRM-50-105 was submitted on February 28, 2012, and 4

the NRC published a notice of receipt and request for comment in the Federal Register on May 23, 2012 (77 FR 30435). In PRM-50-105, the petitioner requested that the NRC require all holders of operating licenses for nuclear power plants to operate them with in-core thermocouples at different elevations and radial positions throughout the reactor core to enable the operators to accurately measure a large range of in-core temperatures in nuclear power plant steady-state and transient conditions. The NRC limited the scope of the review of PRM-50-105 to only the use of in-core thermocouples in pressurized-water reactors because that was the primary focus of the requests in PRM-50-105, although the petitioner also mentioned boiling-water reactors-wefe mentioned . The NRC denied PRM-50-105 The petition was denied on September 12, 2013 (78 FR 56174).

As discussed below, the NRC is denying PRM-50-111 because the petitioner does not justify the need for a regulation that requires the use of in-core temperature-monitoring devices in nuclear power plants.

NRC's Response to Issue 1:

In its denial of PRM-50-105, the NRC evaluated the petitioner's claims thatwhether, in the event of a severe accident, in-core thermocouples would enable nuclear power plant operators to accurately measure in-core temperatures better than core exit thermocouples , and would provide crucial information 1to help operators manage the accident. In PRM-50-111, the petitioner reiterated !ms-the same assertion§.

and expanded on the previous request by including other instrument types that might be used in the measurement of in-core temperatures (e.g., thermoacoustic sensors).

The NRC denied PRM-50-105 because the NRC concluded that knowledge of core temperatures at various elevations and radial positions would not enhance safety or 5

change operator action. Furthermore, core-exit thermocouples, despite known limitations, are sufficient to allow nuclear power plant operators to take timely and effective action in the event of an accident. Core-exit thermocouples in pressurized-water reactors provide an indication of initial core damage during accident conditions and provide the necessary indication to make operational decisions with respect to the approach to imminent core damage.

The current suite of instrumentation used in pressurized-water reactors, which includes core-exit thermocouples, provides sufficient information to determine the need for operator action well before the onset of significant core damage. Other indications include reactor coolant system level and containment pressure. A more comprehensive description of the applications of core-exit thermocouples is provided in NRC's denial of PRM-50-105, Issue 1. In its denial of PRM-50-105, the NRC concluded that there is no need for more accurate measurement of temperatures throughout the core in pressurized-water reactors . The NRC concludes that the reasons for that decision remain valid and are applicable to PRM-50-111 .

In PRM-50-111, the petitioner discussesg core temperature measurement devices other than thermocouples . The NRC evaluated this information and concludes that the nature of the device is not relevant to the decision of whether or not to require the use of in-core temperature instrumentation.

As in the denial of PRM-50-105, the NRC has determined that precise in-core temperatures would not provide information that would enable nuclear power plant operators to better respond to and manage a reactor accident.

The NRC therefore concludes that more accurate and precise temperature distribution information within the reactor core that would be provided by such instrumentation is not necessary for reasonable assurance of adequate protection of the 6

public health and safety or nuclear pmver plant staff, nor would it provide a substantial safety enhancement at nuclear power plants. Therefore, installation of such instrumentation need not be required by regulation .

NRC's Response to Issue 2:

The petitioner asserted that in the event of a severe accident at a boiling-water reactor, in-core temperature-monitoring devices would be more accurate and immediate for detecting inadequate core cooling and core uncovery than readings of the reactor water level, reactor pressure, containment pressure, or wetwell water temperature . The petitioner also asserted that, after the onset of core damage, water level indicators in boiling-water reactors are unreliable.

The NRC determined that the current means to detect and respond to inadequate core cooling is already anticipatory in nature, and emergency operator actions would be no different if in-core temperature-monitoring devices were present.

Therefore, no safety benefit would result from the availability of such devices.

Existing boiling-water reactor emergency operating procedures (EOPs) do not require operator assessment of core cooling. Instead, operators use specific parametric datai such as the water level , containment pressure, containment radiation, and reactor pressureJ in conjunction with the EOP actions to respond to the event. Under accident conditions, reactor vessel water level is an acceptable indication of conditions relating to imminent core damage, and drywell radiation monitors are typically the primary method for determining the presence of core damage and severe accident management guideline entry conditions. For boiling-water reactors , severe accident management guideline entry conditions are also tied to parameters such as water level , containment hydrogen concentration , and component failures. If reactor water level is unknown or 7

conditions render water level instrumentation unreliable, then the EOPs requi re the operators to proactively flood the reactor vessel. In addition , the EOPs for boiling-water reactors describe steam cooling as a method of cooling the core when there is insufficient water to cover the core , typically available when water level is at or above two-thirds of core height. This method allows additional time to restore reactor coolant injection and reduce the likelihood of emergency reactor depressurization, which would be necessary for the injection of low pressure sources.

The intent of the NRC's regulations is to prevent or minimize significant core damage. The detection of inadequate core cooling and actual core uncovery is not necessary for managing emergency and accident scenarios. Nuclear power plant operators are directed by EOPs to take proactive emergency operating actions based on the indication of parameters that are anticipatory to actual inadequate core cooling conditions, while the instruments reading those parameters are still functioning within their acceptably-accurate performance ranges . If significant core damage were to occur, water level instrumentation and in-core temperature instrumentation (if installed) would no longer be relied upon for operator action.

The NRC has determined that boiling-water reactor operators do not need in-core temperature-monitoring devices to safely navigate emergency and accident scenarios. Because the use of water level instrumentation is sufficient to inform operator actions prior to significant core damage, the NRC finds that the information representing the temperature within specific core locations does not provide an improvement in the prevention or mitigation of the consequences of an accident. The NRC has further determined that having the core temperature data would not provide any additional safety margins in managing post accident or severe accident conditions. Therefore, the NRC concludes that more accurate and precise temperature distribution within the 8

reactor core that would be provided by such instrumentation is not necessary for reasonable assurance of adequate protection of the public health and safety or nuclear power plant staff, nor would it provide a substantial safety enhancement at nuclear power plants. Installation of such instrumentation need not be required by regulation .

NRC's Response to Issue 3:

The petitioner stated that in-core temperature-monitoring devices would satisfy the July 12, 2011, near-term task force report recommendations for enhanced reactor instrumentation . As justification forTo support this claim, the petitioner cited Recommendation 8, in Section 4.2.5 of the report, which recommends strengthening and integrating onsite emergency response capabilities such as emergency operating procedures, severe accident management guidelines and extensive damage mitigation guidelines. The petitioner also cited Volume 10 of NUREG-1635, "Review and Evaluation of the Nuclear Regulatory Commission Safety Research Program: A Report to the U.S. Nuclear Regulatory Commission ," dated October 31 , 2012. The petitioner quoted sections from pages 11 and 12 of this report, in which the NRC stated that the agency recognized the need for enhanced reactor instrumentation, that such instrumentation would help clarify the transition points of various onsite emergency response capabilities , and that the NRC was in the process of adding this to the implementation of the near-term task force report recommendations . The petitioner gave, as an example of a transition point, the point at which nuclear power plant operators should transition from EOPs to implementing severe accident management guidelines.

The staff proposed plans to the Commission for resolving open near-term task force recommendations in SECY-15-0137, "Proposed Plans for Resolving Open 9

Fukushima Tier 2 and 3 Recommendations ," dated October 29, 2015. In SECY 0137, the staff described how remaining open recommendations from the near-term task force report should be resolved. The staff specifically assessed the need for enhanced reactor instrumentation for beyond-design-basis conditions in Enclosure 5 of SECY 0137. The staff recommended that the Commission not pursue additional regulatory action beyond the current requirements, including those imposed by orders EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," and EA-12-051, "Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation." In SRM-SECY 0137, dated February 8, 2016, the Commission approved the staff's closure plan for these items. On January 24, 2019, in SRM-M190124A, the Commission directed agency staff to publish a final rule based on lessons learned from the March 2011 accident at Japan's Fukushima Daiichi plant; the final rule was published in the Federal Register on August 9, 2019 and became effective on September 9, 2019 (84 FR 39684 ).

The final rule wi<<-make§ generically applicable the requirements from the above orders, taking into account lessons learned in the implementation of the orders and feedback received from stakeholders.

As discussed under Issues 1 and 2, the NRC evaluated the potential contribution that more accurate and precise temperature information would have on improving nuclear power plant safety for both boiling-water reactor and pressurized-water reactor plants. The NRC has determined that the availability of such information would not improve operator actions to prevent or mitigate a reactor accident. The NRC finds that the Commission's conclusions in SRM-SECY-15-0137 apply for the instrumentation proposed by the petitioner. The NRC concludes that more accurate and precise temperature distribution information that would be provided by such instrumentation is 10

not necessary for reasonable assurance of adequate protection of the public health and safety or nuclear power plant staff, nor would it provide a substantial safety enhancement at nuclear power plants. Therefore, installation of such instrumentation need not be required by regulation.

Ill. Availability of Documents The documents identified in the following table are available to interested persons as indicated. For more information on accessing ADAMS, see the ADDRESSES section of this document.

Date Document ADAMS Accession Number/Web site /Federal Reqister Citation Petition Documents March 13, 2015 PRM-50-111 - Petition for ML15113B143 Rulemaking from Mark E.

Leyse Regarding In-Core Temperature Monitoring at Nuclear Power Plants July 16, 2015 Federal Register notice: 80 FR 42067 Petition for Rulemaking, Notice of Docketing, Power Reactor In-Core Monitoring February 28, 2012 Petition for Rulemaking ML12065A215 submitted Mark Edward Leyse, on PRM-50-105, Request NRC Require all Holders of Operating Licenses for Nuclear Power Plants to Operate with In-Core Thermocouples at Different Elevations and Radial Positions May 23, 2012 Federal Register notice: 77 FR 30435 Petition for Rulemaking; Receipt and Request for Comment, In-core 11

Thermocouples at Different Elevations and Radial Positions in Reactor Core September 12, 2013 Federal Register notice: 78 FR 56174 Petition for rulemaking; Denial, In-core Thermocouples at Different Elevations and Radial Positions in Reactor Core Other Documents October 30, 1979 The Need for Change, the htt12s://tmi2kml.inl .gov/Docume Legacy of TMI: Report of nts/Common/Presidents%20C the President's Commission ommission,%20(Main%20Re12 on the Accident at Three ort)%20The%20Need%20For Mile Island %20Change, %20The%20Leg acy%20of%20TM I-2%20(1979-10-30).odf July 12, 2011 SECY-11-0093 -

Enclosure:

ML111861807 The Near Term Task Force Review of Insights from the Fukushima Dai-lchi Accident October 31, 2012 NUREG-1635, Volume 10, ML12311A417 "Review and Evaluation of the Nuclear Regulatory Commission Safety Research Program: A Report to the U.S. Nuclear Regulatory Commission" October 29, 2015 SECY-15-0137, "Proposed ML15254A006 Plan for Resolving Open Fukushima Tier 2 and 3 Recommendations" March 12, 2012 EA-12-049 "Issuance of ML12054A735 Order to Modify Licenses with regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" March 12, 2012 EA-12-051 , "Order Modifying ML12056A044 Licenses with regard to Reliable Spent Fuel Pool Instrumentation" February 8, 2016 SRM-SECY-15-0137- ML16039A175 Proposed Plans for Resolving Open Fukushima Tier 2 and 3 Recommendations 12

January 24, 2019 SRM-M190124A: Affirmation ML19024A073 Session-SECY-16-0142:

Final Rule: Mitigation of Beyond-Design-Basis Events (RIN 3150-AJ49)

IV. Conclusion For the reasons cited in Section II of this document, the NRC is denying PRM-50-111. The NRC finds that the existing regulations provide a sufficient level of safety such that additional requirements are not necessary. no improvement in safety

• 1t1ould result from amending its regulations to require the installation of in core temperature monitoring devices. Therefore, installation of in-core temperature-monitoring devices such instrumentation need not be required by regulation .

Dated at Rockville , Maryland, this xxth day of Xxxxx, 2019.

For the Nuclear Regulatory Commission.

Annette L. Vietti-Cook, Secretary of the Commission.

13