ML17187A898
| ML17187A898 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 04/05/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17187A897 | List: |
| References | |
| NUDOCS 9704080258 | |
| Download: ML17187A898 (4) | |
Text
UNITED STATES.
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055S-0001 EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING CORE SPRAY INSPECTION PLAN FOR D3Rl4 REFUEL OUTAGE
'COMMONWEALTH EDISON COMPANY DRESDEN NUCLEAR POWER STATION, UNIT 3 DOCKET NO. 50-249 1.0
- INTRODUCTION
- By letter dated October 3, 19.96, Commonwealth Edison* Company (ComEd, the licensee} submitted the core spray inspection pl~n for the Dresden Nµclear Power Station, Unit 3, upcoming D3Rl4 refuel outage.
ComEd intends to implement the recommendations from* the Boiling Water *Reactor Vessel and Internals Project (BWRVIP} "BWR Core Spray lnterna.ls Inspection and Flaw..
Evaluation Guidelines (BWRVIP-18}," dated July 26, 1996, in the performance of internal core spray examin~tions and e~aluations at Dresden, Unit 3.
ComEd beli.eves that the implementation of ~n inspection plan based upon these*.
recommendations 'will satisfy the IE Bulletin 80-13, "Cracking In Core Spray Spargers," *closeout commitment _regarding the performance of core spray sparger examinations at each refuel outage.
- 2. 0 EVALUATION
.ComEd developed the internal core spray i~spection plan in accordance with Section 3~ Inspection Strategy, of BWRVIP~l8. This section provides specific
- inspection recommendations.for both base 1 i ne i nspe*ct ions and reinspect ion of piping locations, core spray spargers, hidden welds, piping and sparger surfaces away from the welds, piping and.~parger brackets, and* any repairs that might be in.place.
ComEd intends to perform the baseline inspection of these locations duririg the D3Rl4 refuel outage.
The NRC staff notes that a safety evaloation report on BWRVIP-18 has not been completed.at this.time.
The NRC staff is *currently working.on resolution of* some putstanding issues with the BWRViP on this docume.nt.
However, these issues should not prevent licensees from fo 11 owing the guidance in BWRVI P-18 with the understanding.that the NRC staff* has not issued final approval of the guidance.
The BWRVIP-18 recommendations for the baseline inspection of the core spray spargers is discussed in Section 3.2.3, Sparger Locations. This section
'divides nuclear power plants into two types, geometry-tolerant plants and geometry-critical plants. The BWRVIP-18 defines these plant types as follows:
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ENCLOSURE
- 2. -
Geometry-tolerant.plants: These are plants where it*has*been shown that post-loss-of-coolant accident (LOCA) steaming of *the water at two-thirds core height is sufficient to meet fuel s*fety li~its; so spray distribution-per the design *is not essential. _For such plants, i.t is only nece$sary to deliver core spray w~ter inside. the shroud to maintain
. two-thirds core coverage.
Geometry-critical plants: These are plants._where _post-LOCA. steaming is not sufficient, so !llaintaining sparger geometry is critical to assure tttat the)analyzed minimum spray flow rate into~any given fuel bundle~is acc.ompl i shed according to the design.
. ComEd has.determined that Dresden, Unit 3, is a* geometry.:.tolerant plant. *
- because the -Or:esden, Unit 3, *LOCA analysis does not rely upon assumptions
. re.lated to the* sparger spray diStribution.. The LOCA analysis for Dresden~
Unit3~ is* performed using an*NRC-approved Siemens Power Corporation-(SPC)
- methodology. :According to SPC, the amoun~ of cooling *provided by the low.
.. pressure coolant inject.ion (LPCI) *system prior to core reflood is limited by
- . : countercurrent fl ow coridi ti ons and. riot by the core spray di stri but ion.
T_he
- spray _heat t'ransfer coefficients used by. SPC are supported by tests *with*
- countercurrent flow conditions ~t the upper tie plate.
Therefore, the SPC LO'CA analysis methodology does not rely on-.. any assumptions related to th~ LPCI
- .flow distribution (Reference 3)~ Notwithstanding, the NRC. staff conten'ds that no*reli~nce on cooling*:from L~~l-~pray d1strib~tion is bas~d.on the ~ssomption th~t the jet. pumps are. intact. and' thus; c"o.re spray water wi 11 be delivered *to
- the core,prio*r to* reflpod.
The NRC staff can not-conclude that Dresd.en, Unit 3, is.a geometry-,tolerant "plant at. this time, based on the status of _the review'
. of BWRVIP-18:
In addition, the NRC staff n'otes_ tha_t the baseline inspection of the core spray sp*argers is less** comprehensive for geometry:..tolerant plants than
- geometry-critical *pl ants.. These. differences involve the type of inspection
_:_ *.. that. is. performed at specific: sparger locations, i.e., CS VT-1 versus VT-3 for locations S3 and SB, and the*tirrie when the reinspection is performed~ i_;e.,
.. *.one cycJe for geometry-critical \\'ersus two* cycles for geometry-tolerant.~
These is~ues are currently being 'discussed with the*BWRVIP. _Nonetheless, th~
NRC staff find~ that the proposed baseline inspection of the core *.spray.*
sp.argers provides an acceptable level of safety to that provided in* past core
- spray sparger. inspections. under IE Bulletin 80-"13. *
. On-this basis, the NRC staff concludes that the proposed baseline* inspe.ction-*
plan fo,r the core spray spargers *is acceptable.~ Resolution of the remaini.ng
. *issues with respect to.. BWRVIP-18 should also resolve the determination whether
- Dresden, Unit *3, is geometry-tolerant plant and the *acceptable reinspect ion interval of the core _spray _sp*argers.
ComEd stated that if the installation.of 'a new rep~ir is required, then the repair will be baseline-examined in ~ccordance with Section 3.2.4 6f BWRVIP-
.18.
In addition, if repairs are required, then the licensee should provide an evaluation of the repairs to the NRC staff prior to restart of the unit.
3.0 CONCLUSION
The NRC staff concludes that the proposed baseline inspection of the core spray spargers is acceptable for Dresden, Unit 3, D3Rl4 refuel outage.
The resolution of the remaining issues related with the NRC staff review.of BWRVIP-18 should also resolve Dresden, Unit 3,.status as a geometry-tolerant plant and the appropriate reinspection interval of the core spray spargers.
Based on the above, the NRC staff has concluded that there is reasonable assurance that plant operation in this matter poses no undue risk to the health and safety of the publit.
The NRC staff is presently reviewing BWRVIP~l8 and while the NRC staff has not identified a~y ~ajor deficiencies in the. BWRVIP's technical assessment, neither has the NRC staff made.a determination as to its acceptability.
Therefore, the licensee should be advised that if concerns are found during the review of BWRVIP-18 and the licensee follows the ~WRVIP-18 guida~ce, the NRC staff may request that the licensee also address these concerns from a plant-spec~fic basis.
Pri nci p_a l Contributors:
Date:
- April 5, 1997 K. A. Kavanagh
- c. E. Carpenter j.
- 4. 0 REFERENCES I.*
Perry, J. S. '* Commonwealth Edison Company, to USNRC, "Dresden Nuc.lear Power Station Unit 3 Submittal of Core Spray*Inspection Plan for Dresden Unit 3, 11 October 3, 1996.
- 2.
Boiling Water Reactor Vessel and Internals Project (BWRVIP),
11 BWR C~t&
Spray Internals Inspection and Flaw Evaluation Guidelines (BWRVIP-18),
11 EPRI TR~l06740, July 1996.
- 3.
Riddle,. J.f-1.; Siemens PowE_!r Corpqration, to R.J. Chiil, Commonwealth Edi son Company, 11 Importance of LPCS Spray Di stri*but ion During a LOCA, 11 August 30, 1996.
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