ML20154J847
| ML20154J847 | |
| Person / Time | |
|---|---|
| Issue date: | 08/12/1985 |
| From: | Harold Denton, Minogue R Office of Nuclear Reactor Regulation, NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20151L097 | List: |
| References | |
| FRN-54FR52946, REF-GTECI-A-49, REF-GTECI-RV, RTR-REGGD-01.099, RTR-REGGD-1.099, TASK-A-49, TASK-OR AD01-1-03, AD1-1-3, NUDOCS 8603110083 | |
| Download: ML20154J847 (3) | |
Text
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1 AUG 12 585 MEMORANDUM FOR: William J. Dircks. Executive Director for Operations
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FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation 1
Robert B. Minogue Director Office of Nuclear Regulatory Research CORRELATION IN THE PTS RELATIONSHIPOFRT"kORRELATIONS(YOURMEMORAND
SUBJECT:
RULE TO OTHER RT OF JULY 30,1985pT l
This memorandum explains the relationship between the recently promulgated PTS rule, Reg. Guide 1.99, Rev.1 and the recently proposed Reg. Guide 1.99 Rev. 2.
This memorandum also contains RES and NRR's recessnendations regarding how to proceed with the proposed Reg. Guide 1.99, Rev. 2.
promulgated PTS rule (published in the Federal Register on The recently ? contains its own RT 3TS) correlation (to distinguish it from July 23, 1985
, which the rule requires licensees other procedt.res for calculating RT to use when evaluating their p5S[t's RT for comparison to the rule-specified screening criterion. The RT PTlorrelationinthePTSrule was taken from a regression analysis perfor E on the PWR surveillance data available at the time of the initial formulation of the PTS rule in late l
1982 (SECY 82-465. November 1982).
The RT correlation in Reg. Guide 1.99, Rev.
1, dated April
- 1977, (whichNDIs used primarily to set pressure-temperature limits for normal operation), was taken from a i
bounding curve for the data available at that time, consisting of about 2/3 experimental data from research reactors and only 1/3 surveillance data from power reactors.
The staff deliberately chose not to incorporate the Reg. Guide 1.99 RTlkI correlation into the PTS rule because: 1) it was desired to have the lat j
methods, acceptably conservative for PTS use, included in the PTS rule, and Reg. Guide 1.99, Rev. I was somewhat outdated at the time the PTS proposed i
rule was drafted (late 1982); and 2) it was recognized that Reg. Guide 1.99 i
might be subject to repeated revision.because the technology is improving and the surveillance data base is continually expanding, and it was desired i
not to subject the PTS screening criteria to constant changes, with the l
resultant variability in impact, and 3) it was believed necessary to include a prescribed method of calculating RT so that the overall j
conservatism of the rule would not be upset by INnsee or NRC changes to the RT,Yo correlation without giving serious consideration to the whole i
rule.
prevent confusion with RT correlations used for other l
purposes, the correlation in the final NS rule was defined by the tenn i
RT which is used for, PTS screening.
PTS DR
2 AllG 121935 At the time the PTS rule was put into final fom, it was believed that the RT correlation it contained was adequately conservative for the purpose of Ntablishing a screening criterion.
During the relatively long time p
period consumed by the collegial process for rule promulgation, including two separate six month periods by the Comission for their review, the RT During that time, the NRC's evaluation of kcorrelation remained frozen.
p r reactor data and improved correlation techniques continued, with i
the most recent product of that effort being the proposed Reg. Guide 1.99, i
Rev. 2 (recently presented to CRGR) containing RT,
correlations for use in evaluating pressure-temperature limits during n 1 operations.
If the Rev. 2 correlations were used in place of the RT correlation, then higher values of RT would be predicted for a few hnts that have high P
nickel content we1[s.S However, several features in the proposed Rev. 2 T
correlation will likely be the subject of considerable discussion and potential disagreement in the technical comunity when Rev. 2 is issued for i
public coment.
These features involve assumption of a different i
relationship for data fitting, division of the previous single data set into one data group for base materials and a separate data group for weld materials, and elimination of previously used data from research reactors.
They warrant coment by the technical comunity, and until the anticipated coments are resolved, we do not believe the conservatism of the present RTFTS correlation in the PTS rule is called into question.
Accurate values of materials and fluence parameters are essential for the m eningful application of either correlation.
For example, based on current flux levels and the staff's limited infomation on assumed material co'nposition, it was reported to the CRGR at its review of Reg. Guide 1.99, Rev. 2 on July 24, 1985 that the Reg. Guide Rev. 2 correlation predicts the Ft. Calhoun plant would exceed the screening criterion in 1987 (the i
current RT correlation, by contrast, predicts a 1996 date). However, we understand Nat for cycle 10, beginning this fall. Ft. Calhoun will load p
selected fuel assemblies containing several half length poison rods in the-most effective outer row positions, which will cause a significant reduction in flux at the welds that are closest to the RT The effect of this change on the date of exceeding tN screening E
limits.
screening limit has not been quantified, but we believe it will be significant.
In addition, Omaha Public Power District has an effort underway to quantify the material composition of the critical welds.
Preliminary results indicate that it is likely that significantly lower values of RT and Pgence RT will be justifi able following this effort.
Accurate f
reEtion and materials data will be submitted in early 1986 as required by the PTS rule. Using that data, we expect that the screening criterion will be predicted to be exceeded in the mid 1990's or later even if the Reg.
Guide, key. 2 correlation is used.
1 We recomend that the proposed Reg. Guide 1.99, Rev. 2 be issued for public coment.
During the coment period, the PTS rule will remain in place.
i Licensees and the technical comunity will consider the technical merits of the proposal, including its effect on their plants for non-PTS purposes, chiefly as the basis for pressure-temperature limits, which must meet Appendix G 10 CFR Part 50.
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AUG2 2 585 In addition. it.will be made clear in the package issued for public coment that the licensees'may also consider and coment on the proposed change's effect on the calculated PTS risk at their plant, assuming the Rev. 2 correlation if justified, would at some future time replace the RT correlation in the PTS rule.
Following resolution of comments, oSN general agreement is reached regarding the best waf1 conservatism of Ne*
to calculate RT N
then it will be appropriate to re-evaluate the overa PTS rule, and consider whether amendment of the PTS rule is desirable.
At that time, we will have available the plant-specific materials and fluence l
values that the PTS rule requires all PWR Licensees to submit early in 1g86. This will allow us to much more accurately assess the effects on all plants that would result from a changeover to the Rev. 2 method.
l We believe this is the best way to proceed, given the necessity of regulating in a conservative but realistic and consistent way while at the same time encouraging technical progress and improvement in basic understanding of complex phenomena such as material property changes (RTET) during neutron irradiation.
We believe this plan is consistent with the agreements reached at the nesting with you on August 2. Ig85.
We therefore plan to revise the Reg.
Guide 1.99. Rev. 2 package to make clear the relationship of the Guide to the PTS Rule as described above, and then resubmit the package to the CRGR.
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bl 11 m n virector g ffice of Nuclear Reactor Regulation O
Robert 8. Minogue. Director Office.of huclear Reguistoty Research 1
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