ML14107A410
| ML14107A410 | |
| Person / Time | |
|---|---|
| Issue date: | 11/17/2015 |
| From: | NRC/RES/DE |
| To: | |
| Burton S | |
| Shared Package | |
| ML14107A404 | List: |
| References | |
| DG-1275 RG-1.027, Rev 3 | |
| Download: ML14107A410 (13) | |
Text
Response to Public Comments on Draft Regulatory Guide (DG)-1275 Ultimate Heat Sink for Nuclear Power Plants Proposed Revision 3 of Regulatory Guide (RG) 1.27 On September 9, 2013, the NRC published a notice in the Federal Register (78 FR 55117) that Draft Regulatory Guide, DG-1275 (Proposed Revision 3 of RG 1.27), was available for public comment. The Public Comment period ended on November 8, 2013. The NRC received comments from the organizations listed below. The NRC has combined the comments and NRC staff responses in the following table.
Comments were received from the following:
Vijay M. Nilekani, Technical Advisor Chris Dudley Nuclear Energy Institute (NEI) ADAMS Accession No. ML13269A375 1201 F Street, NW, Suite 1100 Washington, DC 20004 Anonymous ADAMS Accession No. ML13322B147 ADAMS Accession No. ML13325A931 Commenter Section of Specific Comments NRC Resolution DG-1275 NEI 1 Page 4 & 5 Too prescriptive, with some elements that may not have an The staff partially disagreed with this comment.
Discussion, established or NRC endorsed mechanism to evaluate, and new Background design inputs that may belong to 'beyond design basis' In proposed revision 3 of draft RG-1.27 (DG-Sufficient considerations, a process still in regulatory development. 1275), the staff added discussions on design conservatism considerations for the ultimate heat sink (UHS) capability For example, "consider the effects of climate changes that might such as the transient analysis, the potential effects of a single occur over the design life of the facility, etc. What would be the of recirculation on the same and/or interference on sources criteria & methodology to quantify? Moreover, the Fukushima adjacent UHS wet cooling towers, etc. The staff Flooding Task Force is working with NRC on various guidance also clarified the discussions on the meteorological on dam failures, etc. and language here is duplicative of other conditions to be considered in the design of the guidance. UHS. The staff disagreed that these discussions represent beyond design basis scenarios.
Regarding the example cited, the intent of this statement was to ensure that long-term possible environmental changes are considered in the October 2014
design of the UHS. Staff has further clarified the sentence to read:
For natural sources, historical experience indicates that river blockage (e.g., ice dams or flood debris) or diversion may be possible, as well as potential changes in ocean, river, or lake levels as a result of severe natural events, or possible changes in climatological conditions in the site region resulting from human or natural causes, that may occur during the plant lifetime.
The staff also added the following sentence in Regulatory Position C.1.e.(1) :
Current literature on possible changes in the climatological conditions in the site region should also be reviewed to be confident that the methods used to predict weather extremes are reasonable.
This addition is consistent with the Standard Review Plan (SRP) Section 2.3.1 Regional Climatology.
NEI 2 Page 6, last The guidance for scoping of SSC's in the Maintenance Rule is in The staff partially agreed with this comment that paragraph NUMARC 93-01 Rev. 4a, and endorsed by R.G. 1.160. Further, not all water control structures affecting a plant and page 11, in many cases, the water controlling structures are not in the site would be within the jurisdiction of the sect. 5 jurisdiction of the licensee, but other entities. Reference to the licensee/applicant. The discussion of the paragraph d Maintenance Rule should be removed, as it is an arbitrary Maintenance Rule has been revised to clarify that inclusion as written. only those structures within the jurisdiction of the licensee should be monitored in accordance with the Maintenance Rule and RG 1.160.
NEI 3 Page 7, Use of international standards should go through a formal The staff agreed with the comment. The Harmonizati endorsement review process, preferably with adequate stake discussion of the IAEA Safety Guide is not an on with holder input as applicable, similar to adoption of other standards. endorsement of the Safety Guide. It is to only International make the reader/user of this RG aware that a 2
Standards corresponding international standard exists. Any endorsement of an international standard would be incorporated into Section C of the RG and subject to public comment. No change to the RG is needed.
NEI 4 Page 9, Pumps and some valves typically require operator action to start. The staff partially disagreed with this comment.
paragraph j Operator action times have been evaluated to ensure they meet Since the active UHS typically support decay system requirements. Either eliminate this paragraph on heat removal or emergency diesel generators, the
'autostart', or include flexible language to permit operator should automatically start language remains as-manual action to start the system. is. The staff added the following to allow operator action:
If the UHS mechanical component does not incorporate design features that automatically start and open/close, operator actions are required to support its intended safety function.
NEI 5 Page 11, sect This is duplicative of Item III page 6 of GL 89-13 and could be The staff agreed in part with this comment that the 5, paragraph deleted. text is duplicative of the guidance provided in GL a: entire 89-13. However, the staff disagreed with deleting paragraph this text from proposed Revision 3 to RG 1.27.
Generic communications such as generic letters or interim staff guidance are intended to be informal guidance to address emerging issues in a timely manner. It is appropriate to incorporate these interim communications into more permanent guidance such as the regulatory guides. Therefore, the staff decided to keep this guidance in the proposed Revision 3 to RG 1.27.
NEI 6 Page 11, sect This paragraph would move HX testing from GL 89-13 into the The staff disagreed with this comment. It was not 5, paragraph IST program. GL 89-13 allows HX testing frequency to be the staffs intention to move heat exchanger (HX) b: entire based on test results from each HX. IST frequency is time- testing from GL 89-13 into the in-service testing paragraph based. This would increase work scope with no increase in (IST) program. The intent of this paragraph was to safety margins. ensure that the UHS systems, including those safey-related heat exchangers are tested periodically. The staff has revised the sentence to 3
read:
Both the initial pre-service test program and the periodic test program should encompass those safety-related heat exchangers that are connected to the UHS and required for the UHS to perform its nuclear safety-related functions.
This should eliminate the confusion with the ASME Operation and Maintenance (OM) Code IST program. The staff also revised the heading of Section 5 to read:
Inspection, Maintenance, and Performance Testing NEI 7 Page 11, Part 21 section 7.3 states that test temperatures should be as The staff agreed in part with this comment. The sect. 5, close as possible to accident conditions as possible to minimize scope of Part 21 of the OM starndards states that paragraph c: errors from fluid property changes. This Part establishes the requirements for "Performanc preservice and inservice testing to assess the e testing of The available heat load for most HX testing is much lower than operational readiness of certain heat exchangers UHS heat design basis. Therefore the testing must be performed at cooling used in nuclear power plants. The heat exchangers exchangers water temperatures much lower than design so that the covered are those required to perform a specific should be in temperature differential between shell-side and tube-side fluids function in shutting down a reactor to the safe accordance is maximized. Otherwise, temperature instrument error and test shutdown condition, in maintaining the safe with ASME uncertainty could yield a meaningless result. See attached shutdown condition, or in mitigating the OM-2009, ASME OM-2012, Part 21 page. Delete this paragraph or further consequences of an accident. Based on this, the Part 21" clarify. Please note that ASME OM-2012 supersedes OM 2009. staff concluded that it was reasonable to perform testing of UHS heat exchangers in accordance with Part 21 of the ASME OM standards or an equivalent test method as stated in the proposed Revision 3 to RG 1.27. Specific test requirements regarding OM standards should be addressed by the appropriate ASME technical committee.
The staff has updated ASME OM-2009 to ASME OM-2012.
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NEI 8 Page 11, sect This is duplicative of paragraph B of Enclosure 1 of GL 89-13 The staff agreed in part with this comment that the 6, paragraph and could be deleted. text is duplicative of the guidance provided in GL a: entire 89-13. However, the staff disagreed with deleting paragraph on this text from proposed Revision 3 to RG 1.27.
chemical Generic communications such as generic letters or treatment of interim staff guidance are intended to be informal service guidance to address emerging issues in a timely water. manner. It is appropriate to incorporate these interim communications into more permanent guidance such as the regulatory guides. Therefore, the staff decided to keep this guidance in the proposed Revision 3 to RG 1.27.
NEI 9 Page 11, sect This is duplicative of paragraph C of Enclosure 1 of GL 89-13 The staff agreed in part with this comment that the 6, paragraph and could be deleted. text is duplicative of the guidance provided in GL b: entire 89-13. However, the staff disagreed with deleting paragraph on this text from proposed Revision 3 to RG 1.27.
flushing Generic communications such as generic letters or redundant interim staff guidance are intended to be informal and guidance to address emerging issues in a timely infrequently manner. It is appropriate to incorporate these used cooling interim communications into more permanent loops. guidance such as the regulatory guides. Therefore, the staff decided to keep this guidance in the proposed Revision 3 to RG 1.27.
NEI 10 D. This is not industry's understanding of the appropriate The staff agreed in part with these comments.
Implementati application of backfit requirements. Please see Attachment 3 on on, Use by Section D. The comments generally agreed with the NRC NRC Staff position by re-articulating the Agency position.
2nd para, last Section D. Implementation sentence The stated purpose of this section is to provide information on However, the NRC took exception to NEIs how applicants and licensees may use Revision 3 to Regulatory conversion of the phrase essential consideration Guide 1.27, as well as to explain how the NRC plans to use to read indispensable consideration in the last Revision 3. Section D states that applicants and licensees may paragraph of Attachment 3 to NEIs comments.
voluntarily use the guidance contained in Revision 3 to demonstrate compliance with underlying regulations, but leaves Specifically, NEI stated that [T]he essential 5
open the possibility of alternative methods. Section D also consideration criteria should limit application clarifies that "voluntary" use of the guidance by a licensee of the forward-fit concept to new or different means that "the licensee is seeking the action of its own accord, positions contained in Revision 3 that are without the force of a legally binding requirement or an NRC indispensable in order for the NRC staff to approve representation of further licensing or enforcement action."'1 the voluntary licensee request at hand.
Importantly, with respect to maintenance of a licensee's current The staff concluded that an indispensable licensing basis, the guide states: "Current licensees may consideration was an unnecessarily higher continue to use guidance the NRC found acceptable for standard than an essential consideration, and complying with the identified regulations as long as their current NEI failed to show why the less stringent test licensing basis remains unchanged."2 Further, Section D clarifies would be insufficiently protective. The higher that unless Regulatory Guide 1.27 is part of the licensing basis standard would unduly limit the NRCs capability for the facility, the NRC staff may not take the position that to make regulatory decisions that are defensible failure to comply with the guide constitutes a violation of the and have public confidence. It was also not agency's requirements. NEI agrees with these statements needed to achieve NEIs goals, based upon NEIs regarding maintenance of a licensee's current licensing basis. own example in its comment. A review of NEIs Imposition of new or different positions contained in Revision 3, example for applying the indispensable test (i.e.,
in the circumstances described above, would likely meet the rejecting missile protection and pipe whip as not definition of backfitting provided in 10 C.F.R. § 50.109, and an indispensable consideration to changes in water must be analyzed as such prior to being imposed on licensees. chemistry), would reveal that the same outcome would be achieved even under the essential Section D goes on to describe limited circumstances in which consideration test. Thus, it was unclear why a the NRC staff may request that a licensee adopt new or different more stringent test is needed.
positions in Revision 3, or an equivalent alternative:
No changes were made to proposed Revision 3 of If an existing licensee voluntarily seeks a license RG 1.27 as a result of this comment.
amendment or change and (1) the NRC staff's consideration of the request involves a regulatory issue directly relevant to this new or revised regulatory guide and (2) the specific subject matter of this regulatory guide is an essential consideration in the staff's determination of the acceptability of the licensee's request, then the staff may request that the licensee either follow the guidance in this regulatory guide or provide an equivalent alternative process that demonstrates compliance with the underlying NRC regulatory requirements. This is not considered 6
backfitting ... or a violation of any of the issue finality provisions in 10 CFR Part 52.3 This language describes an important category of so-called "forward fits,"4 to which the backfitting rule and issue finality provisions in 10 CFR Part 52 do not apply. In a June 2010 letter, the NRC General Counsel described "forward-fits" as follows:
[T]here are guidance documents which the NRC staff intends only to be "forward fit," that is, the guidance will be applied only to: (i) future applicants; and (ii) applications from existing licensees for license amendments, requests for exemptions, and other requests for dispensation from compliance with otherwise-applicable legally binding requirements (an example of such a request would be an application to use an alternative under 10 CFR 50.55a). In these circumstances, the NRC does not consider the issuance of "forward fit" interpretive guidance to constitute "backfitting." As the NRC has stated in several different contexts, the Backfit Rule does not protect the expectations of future applicants (including licensees seeking NRC permission to conduct licensed activities in a manner different than what the NRC previously approved) regarding the regulatory requirements that they must meet to obtain NRC approval.5 The second category of "forward-fits" highlighted in the above-quoted passage is of particular concern to industry because it applies to existing licensees, rather than "future applicants."
Unlike "future applicants," licensees justifiably rely on the adequacy of their current licensing bases to ensure compliance with NRC requirements. A stable (although not necessarily static) licensing basis is vital to ensuring predictable and reliable regulatory framework. In this vein, a primary purpose of the backfitting rule and issue finality provisions in 10 C.F.R. Part 52 is to ensure that changes to that framework are properly 7
evaluated and justified, prior to being imposed on licensees.
Thus, it is vital that the language in Section D that limits and conditions imposition of new or different positions on licensees that are seeking voluntary changes to their current'licensing bases be applied in a consistent, reliable, and disciplined manner.
Specifically, new or different positions contained in Revision 3 (or acceptable alternatives to such positions) may be imposed on licensees that voluntarily seek changes to their current licensing bases, without prior application of the backfitting rule or issue finality provisions, only where:
- 1. The NRC staff's consideration of the licensee's voluntary request involves a regulatory issue directly relevant to Revision 3; and
- 2. The specific new or different position contained in Revision 3 that the staff wishes to impose on the licensee is an essential consideration in the staff's determination of the acceptability of the licensee's voluntary request.
Criteria 1 - i.e., the "direct relevance" criteria - should limit application of the forward-fit concept to voluntary requests for changes involving issues that are directly and explicitly addressed in Section C. "Staff Regulatory Guidance" of Revision
- 3. These issues include:
- System design considerations for the Ultimate Heat Sink
- Natural phenomena and site hazards for the Ultimate Heat Sink (UHS)
- Defense-in-Depth considerations for the UHS
- Technical Specifications explicitly addressing the UHS
- In-service testing, maintenance, and performance testing of the UHS piping, structures and components
- Water testing and microbiological control of water used in 8
the UHS Applied in this way, the "direct relevance" criteria appropriately limits application of the forward-fit concept to voluntary licensee requests dealing with changes that are directly and explicitly covered by the specific regulatory guidance actually provided in Revision 3 to Regulatory Guide 1.27.
Criteria 2 - i.e., the "essential consideration" criteria - should limit application of the forward-fit concept to new or different positions contained in Revision 3 that are indispensable in order for the NRC staff to approve the voluntary licensee request at hand. For example, a new or different position in Revision 3 dealing with missile protection and the effects of pipe whip would not be an "essential consideration" in approving a voluntary licensee request to change a portion of the current licensing basis dealing with UHS water chemistry.6 Thus, in this example, the backfitting rule would need to be addressed prior to imposition new or different positions on missile protection and the effects of pipe whip, notwithstanding the fact that the licensee is voluntarily requesting a change to its CLB on UHS water chemistry. Applied in this way, the "essential consideration" criteria would appropriately limit application of the forward-fit concept to issues that are indispensable to the staff's approval of the voluntary licensee request at hand.
1 DG-1275, at FN3.
2 Id. at pg. 12.
3 Id. See also, Letter from Stephen Burns (General Counsel, NRC) to Ellen Ginsberg (Vice President, General Counsel, and Secretary, NEI) (June 14, 2010), at FN2.
4 Id.
5 Id (emphasis added).
6 This example is included purely for illustrative purposes. It is not meant to imply that there are actually new or different 9
positions on missile protection or the effects of pipe whip in Revision 3.
Chris General Missing from this is any consideration of how sea level rise may The staff agreed in part with this comment.
Dudley Comment impact the reliability of the UHS during the license period. Pond banks that were initially safe may be washed away by enhanced The staff agreed that these are important storm surge for example leaving no cooling water supply. considerations for the design of the UHS systems.
Cooling water that was initially fresh may become brackish and In fact, the potential change in sea level was damage equipment not designed for the changed water chemistry included in the discussion section of proposed leading to failure of critical cooling systems. Changed tidal flow Revision 3 to RG 1.27, which states: For natural patterns may lead to accumulation of clogging debris where the sources, historical experience indicates that river original design prevented this. If the effects of subsidence on blockage (e.g., ice dams or flood debris) or ground water are to be considered, then surely the effects of sea diversion may be possible, as well as changes in level rise up to at least 2 meters by 2080 must be considered as ocean or lake levels as a result of severe natural well. events.
The staff has added a new regulatory position under section C.2.a to further address this comment:
(5) potential changes in ocean, river, or lake levels as a result of severe natural events, or possible changes in climatological conditions in the site region resulting from human or natural causes, that may occur during the plant lifetime.
Anonymous Draft Regulatory Guide 1.27, Revision 3, has removed the worst The staff disagreed with this comment.
1 24-hour period following the initial design specific critical time period for peak cooling water temperature. The commenter refers to specific provisions in Revision 2 of RG 1.27, and by extension an Concern: apparent absence from the draft of Revision 3 to Revision 2 of the Regulatory Guide 1.27, required transient RG 1.27, as requirements or that inclusion of a analysis to include the worst 24-hours following the initial specific time period in a certain analysis is critical time period. This analysis period should remain part of required. The staff wishes to clarify by referring the design basis analysis because peak heat loads from a realistic the commenter to Section A of proposed Revision or conservative analysis may occur several hours after the start 3 to RG 1.27 under the heading Purpose of of the initial accident. The proposed relaxation of the transient Regulatory Guides which states, among other 10
analysis requirements would allow under prediction of the peak things, that compliance with them (i.e., regulatory temperature, as the initial water mass may not reach the plant guides) is not required.
until after the first critical time period. For example, the delay in peak temperatures will occur because of the time required to the The proposed revision did not relax considerations heat up of the suppression pool, following the event, before that for the transient analysis. Instead, the proposed energy is transferred to the UHS. Additionally, plant specific revision specified that The meteorological procedure requirement and time required to alignment plant conditions resulting in the maximum intake water system could delay the peak heat load (e.g. spent fuel pools temperature to the plant from the UHS should be cooling may not occur immediately following an event). the worst combination of controlling parameters, including diurnal variations, where appropriate, for Suggested Revision: the critical time period(s) unique to the specific Following the site specific UHS critical time period the worst design of the UHS. Depending on the UHS 24-hour period should be maintained as a requirement for design, the critical time period (i.e., the time transient analysis for peak cooling water temperature. interval after a design-basis accident (DBA) to when the intake water to the plant from the UHS reaches its maximum value) varies. For example, if a wet cooling tower is used as the UHS, the critical time period may be on the order of several hours. As another example, the plant intake water temperature from a cooling pond used as the UHS may reach a maximum several days following a shutdown or DBA. In practice, the 24-hour, post-accident time period has, in many cases, been looked upon as a default time period. Now rather, the proposed revision clarifies that the responsibility for defining and justifying the time period(s) critical to the UHS design lies with the applicant or licensee.
The staff added the following sentence in Section B Discussion, paragraph 7 to further clarify this:
Determining the maximum temperature to the plant from the UHS after a DBA and the associated critical time period can be an iterative process since the maximum temperature to the plant from 11
the UHS can be a function of meteorological conditions, plant heat input, and recirculation time.
Anonymous The draft guidance discusses that "the UHS should be able to The staff partially agreed with the comment.
2 dissipate the heat for that accident safely, permit the concurrent safe shutdown and cooldown of the remaining units, and A change was added to Section C.1.b to address maintain them in a safe-shutdown condition". Furthermore, it is the combined theme of the comments and better stated that there should be sufficient conservatism and freedom clairify NUREG-0800 expectations:
of movement.
The analysis should account for all variations of Concern: design parameters and the full range of operating The existing guidance allows flexible to defer cooling of the conditions that may exist at the time of the spent fuel pools to gain transient analysis margin. Requirements postulated event. This type of analysis is discussing cooling of spent fuel pools should be clarified. Also, commonly accomplished when the most severe set the existing guidance allows for significant delays in cooling the of operating parameters and/or operational non-accident unit to gain transient analysis margin. Emergency conditions is assumed to occur simultaneously and procedures direct operates to cool the units to ensure safety is commonly referred to as a bounding analysis.
margin. Limiting the cooling capability for the UHS structure is Alternatives to this approach should be inappropriate for a shared safety system (e.g. a cooling pond). communicated for review.
Reducing UHS cooling capacity in this manner restricts operational flexibility and reduces plant safety margin. These An additional safety function was added to the modeling approaches gain analytical margin by slowing the Background information to further clarify spent transfer of heat into the UHS instead of ensure that the UHS can fuel pool cooling:
cope with peak heat loads that may be necessary to protect the public. The UHS performs three principle safety functions: (1). and (3) dissipation of Suggested Resolution: maximum expected decay heat from the spent fuel The guidance should prescriptively discuss cooling requirements pool to ensure the pool temperature remains within and the treatment of the associated heat loads in transient the design bounds for the structure, analysis to ensure that safety margin is adequately maintained.
This addition concurs with the SRP 9.1.3, Spent Fuel Pool Cooling and Cleanup System.
No specified time was included for cooling the non accident unit because neither General Design Criterion (GDC) 5 nor Branch Technical Position 12
(BTP) 5-4 specify a cooldown time. GDC 5 specifies an orderly shutdown and cooldown of the accident unit and BTP 5-4, Design Requirements of the Residual Heat Removal System, Section B 1.D, specifies the RHR system must be capable of bringing the reactor to a cold shutdown condition, with only offsite or onsite power available, within a reasonable period of time following shutdown, assuming the most limiting single failure.
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