ML20153D648
| ML20153D648 | |
| Person / Time | |
|---|---|
| Issue date: | 07/24/1998 |
| From: | Collins S NRC (Affiliation Not Assigned) |
| To: | Burrows F NRC (Affiliation Not Assigned) |
| Shared Package | |
| ML20153D328 | List: |
| References | |
| NUDOCS 9809250126 | |
| Download: ML20153D648 (2) | |
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UNITED STATES L
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,j NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. 30e06-0001 o
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July 24, 1998 MEMORANDUM TO:
Frederick H. Burrows, Electrical Engineer Electrical Engineering Branch Division of Engineering, NRR FROM:
Office of Nuclear Reactor Regulation
SUBJECT:
DIFFERING PROFESSIONAL VIEW AND DIFFERING PROFESSIONAL OPINION REGARDING TECHNICAL SPECIFICATION SETPOINTS AND ALLOWABLE VALUES FOR INSTRUMENTATION j
in a memorandum dated March 17,1997, you expressed a differing professional view (DPV) regarding technical specifications (TS) trip setpoints (TSP) and Allowable Values (AV) for instrumentation. A panel reviewed the concems addressed in the DPV and prepared a report which was provided to appropriate NRC staff in order to propose actions to address the panel's recommendations and the schedule for comp'eting those actions in a memorandum dated October 31,1997. NRR staff responsible for li strumentation mid technical specifications, along with senior NRR managers, reviewed the panel t recommendations and conducted further discussions with you and representatives from ths Office of the General Counsel (OGC). By memorandum dated June 22,1998 (attached), staff documented completion of this review and expressed disagreement with the panel's conclusions and concems over implementation of the panel's recommendations. On May 21,1998, you submitted a related differing professional opinion (DPO) to the Executive Director for Operations (EDO) based on concems over the extended period of time without resolution of this issue. This DPO was retumed to me for processing along with the still open DPV, I have carefully reviewed your concems a'ong with the recommendations of the DPV panel and the conclusions of the subsequent staff review. The DPV panelis of the opinion that the regulations require that the technical specifications (TS) include the TSP to meet the 10 CFR 50.36 requument that the TS contain the limiting safety system settings (LSSS). The staff review doc onts the basis of disagreement with this view, concludes that the regulations are not clear in this area, and that precedence on how the regulations have been implemented support th* view that the AV satisfies the requirement that the TS include the LSSS. In addition, sts has expressed conmms over the operability issues if the AV were to be removed from the TS and replaced by the TSP. They have also indicated that it would require significant resources on the parts of both the staff and industry to implement the panel's recommendations. Both the DPV panel and stati agree that there is not a safety issue, in that, with either approach, instrument settings would be adequately controlled. Finally, OGC has advised that, while use of the TSP would clearly satisfy the 10 CFR 50.36 requirement, it may be possible to justify the use of other values such as the AV if the stuff is able to conclude from a technical standpoint that the definition of LSSS is satisfied.
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4 F. Burrows 2
July 24, 1998 Given that there is not a safety issue; that the current system used in the Standard Technical Specifications (STS) and improved STS, which rely on either the AV alone or a combination of AV and TSP, is adequate to controlinstrument settings; and that significant staff and industry resources tLt would be required to implement the recommended changes, the only remaining rationale for implementing the panel's recommendation would be based on the view that they are necessary to satisfy legal requirements. However, based on OGC review, it is not clear that the regulations or the corresponding regulatory history totally support the DPV panel view. I believe that the case presented by staff review (reference to June 22,1998 memo), that AVs satisfy the requirement that the TS include the LSSS is equally valid. Therefore, given no compelling safety or regulatory improvement, I do not believe that it is an appropriate use of either NRC or industry resources to implement the DPV panel's recommendations.
I consider the review of this DPV by NRR to be concluded and intend to take no further actions based on this DPV. Because the subsequent DPO did not raise any additional technicalissues, only a question of timeliness, I also intend no further actions to address the DPO. I would like to thank you for submitting your concems and allowing the DPV process to carry this to conclusion. I realize that sometimes it is a di'ficult personal decision to submit a DPV and I commend you for it. I also realize that it took much longer than expected to reach a decision, this was a difficult issue which required much discussion among the staff, the DPV review panel, and OGC. I hope you recognize that not all DPVs will be resolved to everyone's satisfaction. It is fully expected that in a regulatory business such as ours, reasonable people will occasionally disagree. The purpose of the DPV process is to provide a fair and open forum for this disagreement to be aired and an informed decision to be made. Please do not hesitate to contact me or Brian Sheron, if you have any questions.
Attachment:
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UNITED STATES O
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WASHINGTON D.C. 300SH001
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June 22, 1998 i
MEMORANDUM TO:
Samuel J. Collins, Director j
Office of Nuclear Reactor Regulation i
FROM:
Brian W. Sheron, Acting Associate Dire For Technical Review, NRR Bruce A. Boger, Acting Associate Director For Projects, NRR
SUBJECT:
FOLLOW UP ACTIONS TO NRR AD HOC REVIEW PANEL ON DIFFERING PROFESSIONAL VIEW ON TECHNICAL SPECIFICATION TRIP SETPOiNTS AND ALLOWABLE VALUES FOR l
INSTRUMENTATION
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In a memorandum dated March 17,1997, a differing professional view (DPV) was expressed regarding Tec'inical Specifications (TS) trip setpoints (TSPs) and Allowable Values (AVs) for instrumentation. A panel reviewed th3 cor.: erns addressed in the DPV and provided a report which you forwarded to us in a memorandum dated October 31, 1997. In that memorandum, you requested that we prcir.';15e ections proposed to address the panel's recommendations and the schedule for ccmpleting those actions.
l We have completed a review of the panel's recommended follow up actions regarding the DPV. In addition, we have met with the Office of the General Counsel (OGC), and they have indicated that the wording of applicable regulations and rulemaking history support the view that the TSPs corresponds to the limiting safety system settings (LSSS) which are required to bs in the technical specifications (TS) as recommended by the DPV panel.
However, we ht.ve also met with members of the NRR technical staff responsibis for i
instrumentation and for TS. Based on this integrated interfe e, we believe an alternate l
interpretation exists. Furthermore, the issue is of negligible safety significance j
and implementation of the recommendations would require extensive staff and industry resources. Moreover, we believe that current TS satisfy the requiremer.ts of 10 CFR 50.36 for the reasons discussed below.
We believe that the DPV panel and OGC, in developing their opinion applied more emphasis to the word " setting" in 10 CFR 50.36 than to the description of the LSSS as //mitino safety system sett/ngs. We further believe that the regulatory record is not clear and does not specifically identify either TSPs or AVs as the LSSS. The DPV Panel acknowledges that 10 CFR 50.36 could reasonably be read as allowing the use of either the TSPs or the AVs as the LSSS. Therefore, rather than trying to interpret an unclear regulatory record, we have focused on the precedent set by the staff in implementing this regulation. This history indicates that the staff intended AVs to be acceptable for the LSSS in TS.
Moreover, the current staff position as implemented in the improved Standard TS (ISTS) is ATTACHMENT 486M.' 'O 416 '7&.
S. Collins 2
June 22, 1998 to represent the LSSS as AVs in a single-column fermat with the exception of the Westinghouse ISTS which includes both AVs and TSPs in a dual-column format. OGC i
agreet that tne regulatory record is not totally clear. The lack of clarity is further evidenced by the extensive discussions held by the DPV panel as well as discussions subsequent to the panel decision. Given the lack of a safety issue and the legal ambiguity, we believe that the appropriate decision should be influenced by operational issues associated with the TS and the impact on both industry and staff resources of any change.
More discussion of the NRR staff view is presented in the attachment.
There are three important TS operational issues with which the staff is conce'rned relative l
to the DPV panel's recommended follow up actions: (1) licunsees with only TSPs in their TS have experienced issues in implementing setpoint methodologies and in complying with channel functional test and channel calibration TS requirements, (2) licensees with the l
single-column AV format determine instrument channel operability and satisfy applicable safety limits based on AVs not TSPs, and (3) the assignment of the LSSS exclusively to 3
TSPs is inconsistent with setpoint methodologies that support the ISTS, the previous STS, j
current regulatory guidance, and previous industry standards. The current ISA Standard, S67.04-1994, "Setpoints for Nuclear Safety-Related Instrumentation," which was referenced by the panel but has not been endorsed by the staff, allows the LSSS to be either AVs, TSPs, or both; this standard also allows the LSSS to be controlled by plant procedures.
An obvious app,oach to implement the panel's recommendations would be to list TSPs in a l
single column format in the instrumentation function tables in the TS. We believe this is not appropriate because it would neither ensure control of setpoints, margins, and uncertainties sufficient to satisfy setpoint methodologies, nor would it provide for operability determination consistent with approved setpoint methodologies, national consensus tinndards, and 10 CFR 50.36. As a minimum, AVs provide TS operability criteria; this approach is consistent with the ISTS. An opt:on that would both meet this operability requirement and rddress the DPV recommen6ations would be a two-column TS i
format containing both TSPs and AVs. This option would control operability criteria not Just by plant procedures but by the TS as required by 10 CFR 50.36. TS Surveillance Requirements for channel functional tests and channel calibration would assure that the j
operability criteria were satisfied. To ensure that instrumentation settings were left within the TSP tolerance, the TS could explicitly require resetting an instrument within the TSP tolerance in the event the as found setting was outside the tolerance.
While the option of requiring a two-column format with both AVs and TSPs in TS might be i
viewed as optimal because it would address both TS operability and the C PV panel l
recommendations, it would represent a backfit for plants that have relocated TSPs from the TS. This option would require significant staff and industry resources to implement;it j
4 j.
could not be justified based on safety; and it would not be required to meet the j
i requirements of 10 CFR 50.36 for the LSSS. Thus, the only compelling argument to j
pursue this option would be a compliance backfit based solely on an interpretation of 10 j
CFR 50.36 that TSPs are required by regulation to be included in the TS.
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l ATTACHMENT i
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s S. Collins 3
June 22, 1998 As discussed above and further elaborated upon in the attachment, we do not believe that the regulations or the supporting regulatory history clearly support the OGC view or the differing professional view. We believe that an equally wiid case can be made that AVs satisfy the requirement that the TS include LSSS. Therefore, we do not believe that it is an appropriate use of either NRC or industry resources to implement the DPV panel's recommendations, in summary, the staff believes the current approach to implementing the 10 CFR 50.36 requirement for LSSS by means of AVs is acceptable and can continue to be applied to the TS conversions to the ISTS. However, the staff does and will allow a two-column format with both TSPs and AVs as an option to ticensees who prefer this approach.
Attachment:
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ATTACHMENT 1
l3, As stated in 10CFR 50.36, "Each applicant for a license authorizing operation of a production or utilization facilit'/ shall include in his application proposed technical specifications in accordance with the requirements of this section." Additionally,10 CFR 50.36 requires that a," summary statemant of the bases or reasons for such specification, other than those covering administrative contrels, shall also be included in the application, but shall not become part of the technical specifications. The technical specification will be derived from the analysis and evaluation included in the safety analysis report and may include such additional technical specifications as the commission finds appropriate."
Among the items to be included in the technical specifications (TS) according to 10CFR 50.36 are safety limits, limiting safety system settings (LSSS), limiting conditions for operation (LCO) and surveillance requirements.
Safety limits for nuc!aar reactora are limits upon important process variables that are found necessary to reasonably protect the integrity of certain of the physical barriers that guard against the uncontrolled release of radioactivity. Further, should a safety limit be exceeded the reactor must be shut down and the licensee must notify the commission, review the matter, and record the results of the review including the cause of the condition and the corrective action taken to preclude recurrence.
The LSSS are settings for automatic protective devices related to those variables having significant safety functions. Two points about the LSSS are made, (1) where an LSSS is specified for a variable on which a safety limit has been placed, the setting must be so chosen that the automatic protective action will correct the abnormal situation before a safety limit is exceeded, and (2) if during operation, it is determined that the automatic safety system does not function as required, the licensee shall take appropriate action.
An LCO is the lowest functional capability or performance level of equipment required for safe operation of the facility. When an LCO is not met, the licensee must shut down the reactor or fo! low any remedial action permitted by the technical specifications until the condition can be met.
Surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that the facility operation will be within safety limits, and that the limiting conditioris of operability will be met.
As can be seen from the above, the ree.uirement for an ' Allowable Value" (AV) is not ' pecifically s
required by 10 CFR 50.36 and it would appear, therefore, not to be necessary to include an AV in the TS In fact, the definition for an AV is not specifically stated in TS whether they are "custonf, standard, or the more recent improved standard technical specifications (ISTS).
However,10 CFR 50.36 also does not specifically define or require a " trip setpoint" (TSP)
The purpose of this discussion la to show that although the term " Allowable Value" is not specifically defined in 10 CFR50.36 or in TS, by choosing AVs to specify LCOs for conbiling channel operability and as LSSS for preserving applicable safety I!mits, the requirements of 10 CFR 50.36 are met. The discussion will also show that although TSPs play an integral part of Attachment
2 operating within the LSSS, it is more reasonable when writing TS to select AVs to specify LCOs rather than TSPs. What is important is that TS provide rppropriate limits consistent with staff approval of licensee's various setpoint programs.
Although the inclusion of LSSS in the TS is a requirement of 10 CFR 50.36, the relationship of LSSS to safety limits, LCOs, AVs, TSPs, setpoint methodologies, standards, and regulatory guides continues to be the subject of debate within the nuclear power industry. The assignment of the LSSS to a single TS variable s.id associated setpoint methodology is difficult to resolve for a variety of reasons. Among these reasons is a lack of national consansus setpoint standards during the earfy years of the nuclear power industry and the various unique and not entire!y compatible setpoint methodologies originally provided by NSSS suppliers and contractors. These variations, together with various staff requirements and interpretations resulted in various TS instrumentation requirements, TS formats, LSSS interpretations, operability determinations, and at times excessive LER generation.
Recently, OGC was asked to provide an opinion as to whether the term, " Limiting Safety System Settings" as used in 10CFR 50.36(c)(1)(li) refers only to manually adjusted TSPs or whether LSSS can be interpreted as embracing AVs which are derived from the TSP and analyticallimit instrument channel uncertainty evaluation. The OGC discussion of the LSSS,
" Meaning of Limiting Safety System Settings in CFR 50.36," dated March 16,1998, referenced the guidance document supporting the original 10 CFR 50.36 rule. Although the evaluation by OGC concluded that the LSSS are the TSPs, it is the staff's opinion that the TSPs were not the LSSS as originally implemented. The staff's opinion is based on the implementation of the
" custom" TS, previous STS (circa 1980), ISTS (1992), and reviews of setpoint standards development up to the current industry standard revision. The OGC evaluation stressed that LSSS were " settings"; however, the staff considers the word " limiting" to be just as significant.
As pointed out in the OGC evaluation, the original wording for the LSSS was " Maximum Safety System Setting." This was subsequently changed to " Limiting Safety System Settings" for the final rule. The reason given for the change was that safety limits, safety limit settings, and conditions of operation can be limited at either upper or lower bounds and therefore the word
- limiting" was rnore appropriate, in other words, LSSS are the " limiting" safety system settings or the maximum / minimum settings that safety system settings may have and continue to satisfy the safety limits. The guidance document supporting the initial issuance of 10 CFR 50.36 also states that, "The licensee is free to coerate with any safety system settina within the limitina i
y.alus.*
Based on OGCs review of the 10CFR 50.36(c)(1)(li) and original 50.36 rule making, it was their opinion that contrary to the ISTS single-column AV format that assigns the LSSS to AVs, the LSSS are represented by the TSPs since they are considered the instrument " settings". The staff considered the reasoning behind OGC's opinion and agrees that the inclusion of the TSPs in the technical specification could have some benefit. 'he staff does not believe, however, that a single setpoint column TS with only the TSPs can be implemented without significant confusion and impact on licensees because such an approach wculd not include necessary limits on parameters. To successfully implement the DPV panel /OGC format, the staff concludes that a two colurre opproach with AVs and TSPs would be necessary. Furthermore, Attachment
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the staff believes that a single column TS utilizing AVs can be successfully implemented and still meet the requirements of 50.36 as discussed below.
The DPV panel stated, "The panel found these concems primarily administrative in nature (i.e.,
rt, lated to compliance with 50.36) and do not adversely affect the safe operation of reactors that are subject to TS requirements that do not include TSPs." in addition "... the panel found that the issues identified during these discussions and deliberations do not adversely affect the safe operation of reactors due to TS requirements associated with those issues." Given this general conclusion, the question arises: If the panel recommendation is to be implemented as stated, is a licensee required to add TSPs to the TS? Again, OGC reviewed this question and determined that backfitting would be required if the agency adopted the position that the LSSS be defined as the TSPs and only the TSPs. Although the safety significance was determined to be minimal by the panel, the adoption of the panel's recommendation in conjunction with OGCs opinion would require a compliance backfit for those licensees that previously assigned the LSSS to the AVs. Th4 includes those licensees who have converted to the ISTS.
Operating experience showed a need for guidance on the selection of instrument setpoints (pressure, differential pressure, flow, level, temperature, power, radiation, time delay) used to initiate automatic protective actions and alarms. The lack of a national consensus standard on setpoint methodology led to the development of Regulatory Guide (RG) 1.105 Rev.1. This RG was an attempt by the staff to describe an acceptable method to ensure that instrument Felpoints in systems important to safety were initially within and remained within specified limits.
The RG notes that the most frequent abnormal occurrence reports submitted between January 1972 and June 1973 involved drift of protective instrument setpoints outside TS limits. The single most prevalent reason for a parameter being outside TS limits was the fact that the TS allowed insufficient or no margin between the setpoint and the " technical specification limit" to account for instrument inaccuracies, vibration, or minor calibration variation.
RG 1.105, Rev.1 defines various terms including " technical spec /fication limif' stating that it was the limit prescribed as a license condition on an important process variable for safe operation. However, there is no clear discussion as to the relationship of LSSS to technical specification limits. There is no discussion about LSSS being defined as TSPs. And there is no discussion of the concept of an AV. However, the RG does explain,"the setpoints should be established with sufficient rnargin between the technical specification limit for the process variable and the nominal trip setpoint to allow for (a) the inaccuracy of the instrument (b) uncertainties in the calibration, and (c) instrument drift that could occur during the interval between calibrations." Based on a review of " custom
- TS formats and the discussions and resulting positions taken in the RG, the technical specification limit as referenced by the RG was to be the limit prescribed as a license condition. [ltalics added to quotations for er7hasis.)
Regulatory position 6 of RG 1.105, Rev.1 states that the assumptions -the minimum margin with respect to the LSSS, drift rate, and the relationship of drift rate to testing interval-used in selecting the setpoint values are to be documented. The actual assignment of LSSS to particular variables is not stated. However, the implication that the TSPs' relationships to the LSSS be defined and that sufficient margin be provided between the setpoints and the technical Attachment
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specification limits implies that the TSPs were net required to be the LSSS. A11 hough i
" technical s'oecification limit"is not a 10 CFRSO.36 term it can be asen from RG 1.105. Rev.1 and the ' custom" TS that the LSSS were not soecifically intended to be or assioned to the l
TSPs. Based on the above. the LSSS and the TSPs were not considered identical and the j
TSPs bv themselves were not considered tM LSSS.
i The staff believes that the DPV panel and OGC applied more emphasis to.the word ' setting' j
than to the description of the LSSS as llaldlag safety system settings. The development of l
10 CFR50.36 and " custom" TS does not support the opinion that the TSPs chosen by the licensee must be included in the TS. The limiting values are the values to be listed in the TS.
However, in the initial STS, the staff provided a means to document the TSPs. The reason for i
this wat to more fully monitor licensees' drift assumptions over surveillance intervals to better control TSP values. Subsequently, with the development of the ISTS single column AV format, 2
j the staff again documented the AVs as the ' limiting
- settings which if exceeded the licensee must take appropriate action. The TSPs would be set by the licensee cons! stent with the l
assumptions used to develop channel uncertainty allowances. Obviously the licensee should establish the TSPs conservatively with respect to the AVs such that safety and operability limits j
would not be exceeded except on rare occasions. In other words the TSPs must ba set such i
that they are bounded by the limiting values (i.e., AVs) consistent with the setpoint calculations.
One relaxation associated with the ISTS format is that instrument performance criteria may not j
be as well controlled within the TS. In developing ISTS, instrument performance was recognized as a programmatic objective appropriately left to the licensee and not required to be i
in the TS. From a TS point of view, as long as the trip function criteria are met (the channel trips within the AVs/LSSS) the channelis operable. The performance parameters of the channel with respect to the setpoint calculation and uncertainty assumptions are documented during surveillance (per IEEE 338 and RG 1.118) or inspection and are evaluated by the licensee.
The staff's position is that the TSPs are not the limiting values with respect to TS and that a single column format specifying the AVs as the LSSS is acceptable to control parameter values such that operability is maintained and safety firnits are not be exceeded. The staff believes this position is supported by the 10 CFR50.36 rulemaking documintation and a review of
" custom
- TS developed per the guidance of 10 CFR50.36 shortly after it was issued. The staff's opinion is that a single-column format, with only the TSPs, based on current setpoint methodology would require revisions to TS, setpoint methodologies, Regulatory Guides, industry guidance and standards with a potential loss of ope,iting margin and with no improvement in safety. The DPV panel concurred that the safety significance of not including the TSPs in the TS was minimal. It is the staffs opinion, therefore, that the ISTS single-column AV format is an acceptable and preferable implementation of the requirements of 10 CFR50.36.
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