ML20079L458
| ML20079L458 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/30/1991 |
| From: | Joshua Wilson TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-15-R01, 91-15-R1, NUDOCS 9111060297 | |
| Download: ML20079L458 (4) | |
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4 i t when w r - vis.menauw nse October 30, 1991 U.S. Nuclear F.egulatory Conunission ATTN 3ccument Control Desk Wastingten, D.C.
20555 Gen tl e:ne n :
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In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NLOLEAR PLANT (SQN)'- FACILITY OPERATING LICENSES DPR-?7 AND i
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ENVIRONMENTAL CUALIFICATION - SPECI AL REPORT 91-13, REVISION 1 i
.The er. closed revision to the special report provides the schedule for completing the necescary correct,.!ve act. ions.
This revision satis:ies the commitment made in the special report submitted by letter dated
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. August-20, 1991. The original special report was submitted in accordance i
with Units 1 and 2 License Condition 2.H.
Revisions to the special report are annotated by vertical bars in the right-hand :rargi.n.
If you have any questions conceri.ing this submittal. please telephone Russell R. Therrpson at (6) $) 843-7470.
Sincerely, O
.5 N L. Wilson 1
l Enclosure ec:
See page 2 g 7,Z i
'9111060297 911630
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2 U.S. Nuc1har Regulatory Commission
-October.-30, 1991 cc ' (Enclosure ):
Mr. D. : E. LaParge, Project Manager l
U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville. Maryland 2085?.
SkC Resident Inspector Sequoyah Nuclear Plant
.2600- Igou1 Ferry Road Soddy-Daisy. Tennessee 37379 l
Mr.
B.'A.' Wilson, Pro 4ect Chief U.S. Nuclear Regulatory Commission Region'!I 101 Ma-tetta Street, NW, suite 2900 Atlanta, Georgia 30323 j
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ENCLOSURF 14-DAY TOLLOW-UP 4EPO4T SEQUOYAH NUrLEAR Pl. ANT (SQN)
SPECIAL REPORT 41-3, a vlsiuN i Desc rip ian of Ccud i t ion On August i, 1991,.<ith Units. and 2 aperating in Mode 1, a significant corre tive act. ton report fSCAR) was ioitiatej to doewuent that the calculated, free-field beta radiation doses t h a t. were used to environmentally tualify saf ety-related equipraent housed in small unsealed enclosures incide containrrent were nonconservative.
This condition was sut'sequently determined to be repartable on August I? under License condition T.H of the Lnits 1 and 2 operating licenses.
The beta radiation i n t"i t f or t he *nvir'nmental qualif! cat!er sf SQN aquipment is basec an a.a r.e r i. :alculation generated by IVA corporate Nuclear En g ine e r i a.; in 1M6.
The :alculat ian de termined a redut i.on f ac t ar ta t e applied ta the free-field beta dase
'o components inside ansealed ent;osures utilizirg
+n " effective infinite -laad" re f e renc e volume.
This reference voltene was t ased en the possible spertrum of beta energy levels, the associated probat 111:ies 0:
a a ven beta " art icle h wing, specific itial ene:gy, and the range
.n air i t' a t a beta particle an trivel at a.c i ven energy.
MN-specitic cairulations inen applied the reduction factor trem the generi c:t. culation to de t er nine a tree-field beta radiation dose far ibat component uside the enclosure.
As a result af a recent :alcalation review, the generic beta radiation doses were recalculated utilizing a state-of-the-art s ta t istical predict ;c n medei that nilites Monte Carlo methodology.
This method yielded higher free-field Deta radiatim, deses for equipaent than had tha vrig,inal generic :a '. c a l a t i o n.
The impactec equipment includes safety-related cables, splices, terminal blocks, nenetrations, transmitters, and safety-related nechanical valve seats.
Cause of Conditico The cause at this condition has been concluded ta be the renuit of the failure of the perrennel involved in the ariginal generic beta dose calculation ta realiae the linear reduction methadnlogy used provided nonconservat've results.
Eersonnel involved in the preparation anc verification of the calculatian had no :en parable aethodology readily available to ass m the accuracy ar validity of de calcalation rest its.
They primarily relied upon their experience in radiation analyses in reviewing the calculation.
The generic ralculation was also reviewed as part of the restart efforts for SQN and 13rowns Ferry Nuclear Plant (3FN).
These reviews encompased several aspects, including appropriate reference material, acceptable methodology, mercrical corre:tness, and ascurance that results were in accordance with the problem statement.
As no stancard criteria ta compare the methodology or the results we e readily available, the reviewers relied an industry e xperience to draw the tonclusiart that the calculation was acceptable
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- Corrective Actions
-Upon identification of the nonconservative beta dose valtea, it review of 10 CFR,50.49 equipment qualification records was performed.
Evaluations have been performed-f or the af f ected -equipment, and it has been concluded that the i
equipment' is qualifiable and capable of perf orming its design function.
Site-specific calculations and qualif.ication records to reflect the higher beta doses have not yet been performed.
An assessment of cables and splices sas performed by evaluating a detailed Monte Carlo analysis for exposed cables at BFN, This calculation allowed BFN to qualify cables to a much greater airborne free-field beta dose.
By adjusting the results of the 3FN esl:ulat!"n n that of S;N (adjusting for SQN's specific containment volame and power level ),
values for the expected beta dose for SQN were determined for unjacketed cables and splices inside
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unsealed enciesures. These-values lead to the conclusion tnat the 5QN cables and splices are qualifiable, t
For exposed cables, the NRC methodology provided in insrection and Enforcement Bulletin 79-ole, " Environmental Qualification af Class 1E Equipt,ent"
-(Enclosure 4, Section 4.1.0), along with crediting cperating tire requir erients, supports qualification.
Terminsi blocks were determined to be qualiflante utilizing the new volume reduction factors computed in the revised generic ' beta dose calculation.
A review'ot the calculations performed for the mechanical valve internala shows considerable conservatism in their preparatica.
Consideration of the new reduction-factors will not change the qualification status of the valves l
affected.
l-All other 10 CFR:50.49 components affected by the revised volume reduction
-methodology are qualifiable considering the revised volume reduction factors, shielding considerations, required operating times. and ; radiation thresholds of the component material.
I L Based on the above discussions ano engineering judgement, all 10 CFR 50.49
_ equipnent impacted by the new beta doce reduction f actors ' remains qualifiable
_andl continues to remain capaole of performing its intended design functions.
As such,' no operability concerns exist. A detailed corrective action plan has
. been developed to revise the-appropriate 10 CFR $0.49 qualificetion
-docnmentation. - The neceseary doctaentation revisions wil.1 be completed by-11ay 1,= 1992 -.
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Commitmenta
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The schedule for completing these documentation revisions will-be provided in a revision to this special report by November 1, 1991 (completed by
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Revision -1 of. this special report ).
2.. The necessary documentation revisions will be completed by Nay 1, 1992, PLO90204 / 75.
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