ML20213D145
| ML20213D145 | |
| Person / Time | |
|---|---|
| Issue date: | 02/13/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML111220504 | List: |
| References | |
| CON-WNP-0332, CON-WNP-332, RTR-NUREG-75-087, RTR-NUREG-75-87 NUDOCS 8003240276 | |
| Download: ML20213D145 (4) | |
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- e U.S. Nuclear Regulatory Commission Office of Nuclear Reacter Regulation value-lamect Statement on PROPOSED ADDITION OF APPOSIX A TO STANDARD REVIEW PLAN PSRP 4.2. REVISION 2 DRAFT 1
!. P90P05ED ACTION This appendix provides (a) guidance for the analysis of fuel assembly loses (b) guidance for the detefeinetten of strength of fuel assembly components, and (c) acceptance criteM.
for the fuel assemely structural ressense to enternally applied forces such as arise in less-of-coolant accidents and earthquates.
II. SACKuW he systematic guidance or acceptance criteria exist for this analysis. The leerth Anna and 01aolo Canyon mothees are presently being used as procements, but there are many pretless with this proceeurs. For example, (a) these methods accesseneta the Westinghous, analysis and fuel design, but they are difficult to asely to other veneers, (b) these methods focus undue attention on spacer gries, (c) non-standere analyses, which are inconvenient to require, were eene for North Anna and 014s10 Canyon, and (d) some of the conservatisas accooted for these plants are unmarranted. This guidance plays an taportan-role in resolving two unresolved Safety Issues (A-2 and 8-6).
III. VaLUE A55ESSMENT This appendix will (a) provies fixed criteria and suitable mothees for all assigns and vendors, (b) allow the roeuction of unnecessary margin in areas that are now preventing (and would increasingly prevent) OL amorevel of the fuel for certain plants. and (c) result in a reduction in time spent reviewing relatively uniepertant analyses. The appendix is a clear statement of review requirements and will result in an overall inerevement in the quality of this review.
IV. !M84CT ASSESSMENT A. 3 There will be an aeditional exoense for the evaluation of the grid strength test rigs. This will involve consulting services from a testing laceratory, and the cost snould not azcoed $10.000. Any aeditional review effort C eated my the more
" comorenensive nature of tnis guisance snould be offset Dy savings in areas now tnougnt to De less f moortant.
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M There will be a small nuseer of aseitional coes runs reeufred during the geneMc review of veneer mothees and there will be a small increase in reeutred laboratory testing of spacer gMes. The potential esists that seen veneers any have to reconstruct their test rige if our evaluation shoue them to be inesequate.
From preliminary infocustion it appears that all current fuel destges will oest the new criteria. *herefore, the impact will be essentially confined to the first-time generic oseenstration of compliance, and little or no plant-specific impact is expected.
V. DEC!$ ION ON T W TIOeIICAL apo40ACH Many of the considerations in this appendix tere carried over free past review policies and es not need further discussion. Several new considerations tore questioned and usrrent highlfgnting.
I A diffeMag opinien was empressed by an NRC reviewer during the develgement of '
proceewree in this aspendix (see Attachment A). That reviewer receasensed that a best estiseta analysis of leads be coopered with a 95m95 tower talerance limit (LTI.) on seesured grid strength aM that the coopeHsen show a safety factar (conservative mergin) of at least 1.35. He offered cosaants on several other positions in the propose appendfx.
We have chosen a different approach for the following reasons.
1.
Best estinata comes are usually not ave 11aele for this ana5ysis. The fuel asseemly and reactor coolant system structural comes that have been subsitted to NRC for review are designed to be innerently conservative. The input values that we approve are usually also conservative.
2.
In the precedent-setting North Anne case, where we attempted to use best estimate analytical mothees, the conservative methoes, which had been reviewed, were modified in.a non-Mgorous way to elfeinste some of the conservatises. We believe it is better to keep fnherent conservatises that have been reviewed then to reseve them and substitute an artitrary safety factor. For North Anne,1.35 times the best-estiesta value is only 105 !arger than the conservative value without a safety factor.
3.
There is no assuestion in our wort that calculational methods are per*ect. To the contrary, we recogntre the difficulty in eooeling non-lineer phenomena and find it more reliaole to allow simplifying assuontions that are catantly conservative rather than striving for a best-estimate prediction with error bounds. The fatter is probanly not achievable with the present state of the ar*
4.
The proposed safety factars for staae flashing and pronounced sensitivity are conserative margins that the etnority position would elfeinate. These are recognized sources of cotential error that se believe should be accounted for.
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W retain the use of 95x95 LTL values (or siellar ASME cose values) for all camponenta escent spacer gries because (a) asseretely esfomme gries (even severely esfemos gries) aeoser incasaale of producing significant conseamences ans (b)
M gie spacer gH es eight samege fuel rees, control rods and guise tees. Because they are not acting as suocerting structural assers, using a mean yiele strength value ases not seen that 50E of the gries will " fail;" it means that 505 of the gH es eey be bent and SGE will not. Our mera over the past for years has shoun spacer gMes to be suscetaste to esfomstion, but it has not shown any seMous consequences of spacer gHe esfomation. We nelieve that excessive attention to grie Donavior has divertoe attention from the more insertant comenenta.
6.
A bencneart teet with staneere gMes is desireale because gMe feect testing is not a staneere procesure and large variations any entst from one test Mg to another. One veneer found an apparent incrosse in gH e strength on the orese of 20E anon he changed the hinge arrangement ei his insect penaulum. Some veneers swing peneulums un11e others droo weights or test statically. Our efforts to provies unifom conservatism in the analytical motheos would De seriously unsercut without some seens of knowing that all veneses were esasuring amoroziantely the sans strength presorty.
, VI. IM*'.DerfATION The methoes and eM te M a in this appenetz e sote proceeures that have been inclusee in plant safety analyses for several years.. Isolementation of the LOCA portion of these new procedures for operating reactors and recent operating Itcense actions will occur as part of the resolution of unresolvec Safety Issue A-2. For operating reactors. Ifconsees were notified in January 1978 Dy a letter free victor Stallo to susoly analyses conforming i
to forthcoming guidance. A steiler 1stter went to license acclicants from Roger Boys in Novemeer 1978. The forthcasing guidance, which incluses the LOCA pertions of this apoendix in their entirety, is containes in the generic report on the resolutten of Task A-2 ("AsptMc 81omeown Loans on Pwit PMeery Systems," MUREG-0609). Commleted analyses for both of these categoMes of plants are excocted in January 1900. For all other new plants, these new proceeures will De telementas routinely in the review process.
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