ML20154J908
| ML20154J908 | |
| Person / Time | |
|---|---|
| Issue date: | 07/30/1985 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Harold Denton, Minogue R Office of Nuclear Reactor Regulation, NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20151L097 | List: |
| References | |
| REF-GTECI-A-49, REF-GTECI-RV, RTR-REGGD-01.099, RTR-REGGD-1.099, TASK-A-49, TASK-OR NUDOCS 8603110113 | |
| Download: ML20154J908 (1) | |
Text
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UNITED aTATEs ENCLOSURE 2 NUCLEAR REGULATORY COMMIS$10N
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%,,,, JUL80 585 MEMORANDUM FOR: Harold R. Denton, Director NRR '
Robert B. Minogue, Director, RES FROM: William J. Dircks Executive Dimetor for Operations
SUBJECT:
PRESSURIZED THERMAL SHOCK RULE AND DRAFT REGULATORY GUIDE 1.99, REVISION 2 On July 26, 1985 I sent the enclosed Information Paper to the Comission alertin Shock (g them to differences between the recently issued Pressurized " Radiation ThermalPTS) rule Damage to Reactor Vessel Materials." I wish to inform the Comission as completely and as soon as possible on the implications of these differences and the proposed nsolution.
First, there exists a question in ny mind about the lack of coordination and/or integration on these issues. Given the history of the PTS rule development by NRR and RES and the attendant visibility of this matter, how did these two matters proceed without being properly integrated and coordinated. I request each cf you provide me with an explanation on this issue.
Second, there exists the question 'as to what is the recosenended course of action to resolve any potential differences between the PTS rule and the draft Regulatory Guide. I request a coordinated NRR/RES plan be provided for resolution of this matter. NRR shall assume the lead responsibility for final resolution.
Please be prepared to brief me on the first issue and your preliminary plans ,
~
to resolve the second issue imediately following the staff meeting on '
August 2. 19R5. l q :
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William h ircks l Executive Director for Operations
Enclosure:
Information Paper 851443 B603110113 B50906 ]
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ENCLOSURE 3 j
s f'#%g* uusito sTAvas NUCLEAR REGULATORY COMMISSION
,f was novo =.o c.seau l \,...../ AUG12 985 MEMORANDUM FOR: William J. Dircks. Executive Director for Operations i FROM: Harold R. Denton, Director l Office of Nuclear Reactor Regulation I
! Robert 8. Minogue. Director '
! Office of Nuclear Regulatory Research
SUBJECT:
RELATIONSHIP OF RT CORRELATION IN THE PTS .
i RULE TO OTHER RT NDdORRELATIONS(YOURMEMORANDUM i- 0FJULY30,1985IDT J
l This memorandum explains the relationship between the recently promulgated l
) PTS rule, keg. Guide 1.99. Rev.1. and the recently proposed Reg. Guide 1.99. Rev. 2. This memorandum also contains RES and NRR's recommendations regarding how to proceed with the proposed Reg. Guide 1.99. Rev. 2.
l1 The recently promulgated PTS rule (published in the Federal Register on July 23,1985) contains its own RT other procedures for calculating R1#TS), which correlation the rule(to requires distinguish it from licensees to use when evaluating their pet's RT for comparison to the i
! was ta con from a regression analysis perfordeE on the PWR surveillance data available at the time of the initial fomulation of the PTS rule in late 1982 (SECY 82-465. November 1982). The RT correlation in Reg. Guide 4 1.99 Rev. 1 dated April 1977 (whichNDis used primarily to set pressure-temperature limits for nomal operation), was taken from a bounding curve for the data available at that time, consisting of about 2/3 i experimental data from research reactors and only 1/3 surveillance data
- - from power reactors. ,
l The staff deliberately chose not to incorporate the Reg. Guide 1.99 RT
! correlation into the PTS rule because: 1)itwasdesiredtohavethelatM 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 rule was drafted (late 1982); and 2) it was recognized that Reg. Guide 1.99 might be subject to repeated twvision because the technology is improving and the surveillance data base is continually expanding, and it was desired not to subject the PTS screening criteria to constant changes, with the resultant . variability in impact, and 3) it was believed necessary to include a prescribed method of calculating RT so that the overall conservatism of the rule would not be upset by 1Ensee or NRC changes to the RT correlation without giving serious consideration to the whole rule.N0[o prevent confusion with RT correlations used for other l mrposes, the correlation in the final ES rule was defined by the tem TTPTS which is used for PTS screening.
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At the time the PTS rule was put into final form, it was believed that the Ri of pNtablishing a screening criterion. correlation During the it contained relatively longwastime adequately c period consumed by the collegial process for rule promulgation, including i
' two separate six month periods by the Comission for their review, the RT p correlation remained frozen. During that time, the hRC's evaluation of hr reactor data and improved correlation techniques continued, with the most recent product of that ef fort being the proposed Reg. Guide 1.99, Rev. 2 (recently presented to CRGR) containing RT correlations for use in evaluating pressure-temperature limits during r3bal operations. If the Rev. 2 correlations were used in place of the RT correlation, then higher values of RT nickel content we1[s.5 1 would be predicted for a few@ ants that have high However, several features in the proposed key. 2 correlation will likely be the subject of considerable discussion and potential disagreement in the technical comunity when Rev. 2 is issued for public coment. These features involve assumption of a different
- relationship for data fitting, divisior, 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 comment by the technical comunity, and until the anticipated coments are resolved, we do not believe the conservatism of the present PTS correlation in the PTS rule is called into question.
RT Accurate values of materials and fluence parameters are essential for the meaningful application of either correlation. For exaciple, based on current flux levels and the staff's limited information on assumed material composition, it was reported to the CkGk at its review of Reg. Guide 1.99 Rev. 2 on July 24, 1985 that the Reg. Guide, Rev. 2 correlation predicts 1 .
the Ft. Calhoun plant would exceed the screening criterion in 1987 (the 1
current RT p correlation, by contrast, predicts a 1996 date). However, we understand Nat for cycle 10, beginning this fall, ft. Calhoun will load 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 limits. The effect of this change on the date of exceeding N screening screening limit has not been quantified, but we believe it will be significant. In
- addition, Gnaha Public Power District has an effort underway to quantify the saterial composition of the critical welds. Preliminary results indicate that it is likely that significantly lower values of RT and RT will be justifiable following this effort. Accurate Pgence f
rebtion 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.
Guice, key. 2 correlation is used.
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.
Licensees and the technical comunity will consider the technical merits of the proposal, including its effect on their plants for non-P15 purposes.
chiefly as the basis for pressure-temperature limits, which must meet Appendix G, 10 CFh Part 50. '
l
.* 3 AUG J t 385 In addition, it will be made clear in the package issued for public coment that the licensees may also consider and connent on the proposed change's effect on the calculated PTS risk at their plant, assuming the Rev. 2 i correlation, if justified, would at some future time replace the RT correlation in the PTS rule. Following resolution of connents, o$N general agreement is reached regarding the best way to calculate RT N then it will be appropriate to re-evaluate the overall conservatism of Ne' PTS rule, and consider whether amendment of the PT5 rule is desirable. At that time, we will have available the plant-specific materials and fluence values that the PTS rule requires all PWR Licensees to submit early in 1986. 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.
i 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 t i same time encouraging technical progress and improvement in basic l understanding of complex phenomena such as material property changes t (RTNDT) during neutron irradiation.
l be believe this plan is consistent with the agreements reached at the i meeting with you on August 2, 1985. We therefore plan to revise the keg.
Guide 1.99 Rev. 2 package to make clear the relationship of the Guide to the PTS Rule as described above, and then resubciit the package to the CRGR.
&b) R n wn, uirector Office of Nuclear Reactor Regulation
\ '
0
. Robert B. Minogue, Director i Office of huclear Regulatory Research 1
b s
l i
ENCLOSURE 4 PROPOSED ADDITION TO THE INTRODUCTION IN DRAFT REGULATORY GUIDE 1.99 REVISION 2 WHEN IT G0ES OUT FOR PUBLIC COMMENT A SIMILAR PARAGRAPH IS TO BE INCLUDED IN THE COVER MEMORANDUM SENDING REVISION 2 TO THE UTILITIES AND OTHERS FOR COMMENT The calculative procedures given in paragraph C.I.a of this draft Guide are not the same as those given in the Pressurized Thermal Shock rule
- for calculating RTPTS, the reference temperature that is to be compared to the screening criterion given in the rule. Issuance of Regulatory Guide 1.99, Revision 2 for public coment in no way affects the recently promulgated PTS rule. Licensees and the technical comunity are requested to coment on the technical merits of this proposal, including its effect on their plants for non-PTS purposes, chiefly as the basis for calculation of pressure-temperature limits as required by Appendix G. 10 CFR Part 50.
Licensecs 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 PTS correlation in the PTS rule. Following resolution of coments, and once general agreement is reached regarding the best way to calculate RT NDT, then it will be appropriate to re-evaluate the overall conservatism of the PTS rule.
- " Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events," Federal Register, July 23, 1985, pp. 29937-29945 l
1
c OD L CHANGES IN REGULATORY GUIDE 1.99, REVISION 2 BASED ON COMENTS RECEIVED AT THE JULY 24, 1985 CRGR MEETING
- 1. p.1, 2nd 1 - Paragraph added to explain the relationship of the Guide to the PTS rule
- 2. p. 9,1st 1 - References to General Design Criterion 31 was deleted from the Implementation section because it refers to " postulated accident conditions," among others, and it was desired to avoid any implication that the Guide is to be used for the calculation of RT for comparison with the screening criterion in the PTS rule. PTS CHANGES IN REGULATORY GUIDE 1.99, REVISION 2 BASED ON COMMENTS BY M. A. TAYLOR IN HIS MEMORANDUM TO THE CRGR MEMBERS. DATED JULY 19, 1985
- 1. p. 6,1st 1 - Deleted reference to the Standard Review Plan to avoid potential regulatory confusion. The reference was not essential to the Guide.
- 2. p. 6. Footnote - Clarified the meaning of the reference to welding flux.
- 3. p. 8, 1 C.3. -
Added a footnote to clarify the meaning of the reference to " low levels" of certain residual elements.
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