AECM-88-0205, Followup Ro:Re Incident Involving Stuck Peripheral Orifice Fuel Assembly During Second Refueling Outage.Stuck Bundle Successfully Removed W/O Complications.No Plans Exist to Reuse Formerly Stuck Assembly

Followup Ro:Re Incident Involving Stuck Peripheral Orifice Fuel Assembly During Second Refueling Outage.Stuck Bundle Successfully Removed W/O Complications.No Plans Exist to Reuse Formerly Stuck Assembly

ML20206F239
Person / Time
Site:	Grand Gulf
Issue date:	11/15/1988
From:	Cesare J SYSTEM ENERGY RESOURCES, INC.
To:	Ernst M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
AECM-88-0205, AECM-88-205, NUDOCS 8811210046
Download: ML20206F239 (6)

Text

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M90tAWEE. INC.

NN runmewn November 15, 1988 U. S. Nuclear Regulatory Comb: ion Region II 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 Attention: Mr. Malcolm Ernst, Acting Regional Administrator

SUBJECT:

Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 Followup Report on Stuck Peripheral Orifice fuel Asse.-bly AECM-88/0205 Via letter dated November 21, 1987 System Energy Resources, Inc. (SERI) comitted to provide a followup report on the incident involving a stuck peripheral orifice fuel assembly during the second Grand Gulf Nuclear Station refueling outage.

The attached followup report discusses both the incident and SERI's ,

resolution of it.

If you need additional information, please let me know.

Yours truly, r

a JGC:bwt gg

- c.

Attachment

, cc: Mr. W. T. Cottle (w/a) g Mr. T. H. Cloninger (w/a) 7^' Mr.R.B.McGehee(w/c))

Mr. N. S. Reynolds (w/a gh Mr. H. L. Thomas (w/o) g<z Mr. H. O. Christensen (w/a)

Mr. L. L. Kintner, Froject Manager (w/a) h'a L Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Comission p Mail Stop 14B20 Washington, D.C. 20555 g l 1

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J14AECH88101302 - 1 ' " " I ".e 1 , w' '.'. n " ..a" ",, # l 1 ' " '

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hM. / Oh GRAND GULF NUCLEAR STATION FOLLOWUP REPORT ON SECOND REFUELING OUTAGE STUCK PERIPHERAL ORIFICE FUEL ASSEMBLY I. INTRODUCTION On November 19, 1987 during the second refueling outage (RF02) at Grand Gulf Nuclear Station (GGNS), attempts to remove a peripheral orifice fuel assembly failed. SERI detennined that this resulted from misalignment between the fuel assembly nose piece and the peripheral fuel support casting.

In order to dislodge the stuck assembly, activities not currently allowed by the GGNS Technical Specifications had to be performed: specifically the use of a force greater than that specified and the use of equipment other than the main hoist. Similar events occurring previously at two foreign BWR-6 facilities had been safely resolved by a similar approach to that proposed for use at GGNS.

To remove this stuck assembly, relief was needed from the GGNS Technical Specification requirements. SERI requested (via letter AECM 87/0230 dated November 21,1987) that the Nuclear Regulatory Comission grant enforcement discretion with respect to these requirement 3 to allow activities for the sole purpose of dislodging and removing the stuck fuel assembly. The NRC granted the enforcement di.scretion on November 23, 1987.

SERI comitted to provide the NRC with a followup report on the event regarding the results of ongoing evaluations and final disposition of the problem. These results are discussed later in this report.

II. BACKGROUND On November 19, 1987 during the RF02 core shuffle, while attempting to remove peripheral fuel assembly LJSO47 (core location 01-32), the load  :

limit trip set at approximately 1200 pounds was activated without assembly I novement. An inspection of the fuel assembly upper grid location revealed that the assenbly was about one inch lower than the surrounding assemblies.

The face adjacent assemblies were removed anc upon inspection of fuel assembly LJSO47 by remote video, SERI discovered that the assembly nose piece was not positioned in the peripheral support casting, but was instead wedged beside the support casting.

Several attempts were made to dislodge the assembly with the fuel grapple, and each atO mpt failed due to a load limit trip at approximately 1200 pounds.

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4 r

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Attachment to i AECM-88/0205 l I

Consultation with General Electric indicated that similar problems had i occurred at two foreign BWR-6 facilities on peripheral orifice fuel I assemblies, r

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, Recognizing relief was needed from the GGNS Technical Specifications to remove the stuck assembly, SERI submitted a request for enforcement l i discretion via letter AECM-87/0230 dated November 21, 1987. In that  !

letter, fo'iowing a similar approach to that used successfully at the i foreign BWR-6 facilities, SERI described the detailed procedure to be  ;

used to remove the stuck assembly. The procedure was to provide that:

1. Only essential personnel associated with the fuel assembly t removal would be present on the refueling floor. Unrelated refueling floor activities would be suspended.

2. Technical Specification requirements for core alterations would  ;

remain in effect, ,

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3. Using the solar crane hook as an attachment point a manually  !

operated clainfall and a load indicator would be hooked in series

! with the General Purpose Grw',e for applying force to the stuck r I

assembly. Administrative controls would b9 4mplemented to  ;

prevent vertical and la'.eral movement of toe polar crane during E

times that the grapple was engaged to the assembly.

1 4. An attempt would then be made to dislodge the misaligned fuel l I assembly with the chain fall using a maximum force of f 2000 pounds. i l

l S. If the above was unsuccessful, a hook was to be lowered and r i inserted into the nose piece of the fuel a nembly. An upward .

! force of up to 1000 pounds as measured by an in line load l

> indicator would be exerted on the hook while lifting the fuel  ;

j assembly with the chain fall as described above. l t

6. Administrative controls would prohibit removal of the fuel  !

assembly from the core by any method other than the refueling  ;

4 platform main holst. Use of the chain fall would be restricted r

! to correcting the misalignment only. l l The letter also dit;ussed safety considerations including thermal hydraulic analysis of flow effects resulting from the stuck fuel assembly, j

! effect of flow and power levels on the stuck anembly itself, and effect t I

of flow on the remainder of the core. SERI addressed load analysis and i rtdiological consequences of the proposed actions as well. Conmitments were made with regard to corrective and followup actions. These will be  ;

discussed later in this report.

l Via telephone conversation (MT! 87/0104) the NRC granted the enforcement j discretion on November 23, 1987. Written confirmation was provided by  ;

the NRC via letter (MAEC-87/0316) dat.d 12/11/87. l 1

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~ Attachment to AECM-88/0205 t

i III. REMOVAL OF STUCK ASSEMBLY  !

On November 24, 1987, under special instructions to Material Nonconformance  !

' Report 0382-87, fuel assembly LJSO47 was removed via the following method: [

Using the polar crane as an attachment peint, a manually operated chainfc11 and a load indicator was installed in series with the General Purpose Grapple.  ;

The General Purpose Grapp' was attached to the fuel i assembly bail handle and load was gradually increased.  !

At approximately 1600 poundr., fuel assembly LJSO47 l broke free and was reseated in the support casting. [

LJSO47 was then transferred to the spent fuel pool per i approved movement sheets. [

On November 25, 1987 end November 26, 1987 fuel assembly LJSO47 and the i following reactor internals were inspected for damage: l i

1 Peripheral fuel support fillet weld,  !

2 Peripheral support casting,  !

3 Area around support casting, and [

4 Top guide.  ;

The above listed inspections as performed by General Electric personnel I and witnessed by SERI personnel showed no evidence of assembly or reactor }

W ernal damage. j IV. CORRECTIVE,AND FOLLOWUP ACTIONS A. In order to assure similar misalignment of the peripheral assemblies .

does not occur again and to verify that no additioral misalignment l existed in the fuel assemblies already loaded as a result of the i RF02 core shuffle, the following actions were performed:

1) Of the twenty-eight peripheral locations, with the I peripheral support castings, the fuel assemblies '

installed prior to November 19, 1987 were visually  !

verified for proper seating. The remaining fuel assemblies were viewed as the assembly was actually ,

lowered into place for proper seating.

2) In addition to the above, all the peripheral fuel assemblies were visually verified, from a side (

view, to be at the e.orrect height by viewing the j fuel channel proximity to adjacent fuel channels.  ;

l B. Procedure 09-S-02-106, "Core Loading Verification", was revised i as committed to in AECM-87/0230. l

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.. Attachment to AECH-88/0205 C. In accordance with the inspection requirements as described in AECM-87/0230, the following inspections were performed:

On November 25, 1987, following removal from the reactor core, fuel assembly LJSO47 was visually inspected for wear marks, scuffing, and other signs of damage. The inspection included the nose piece, upper tie plate / bail handle and the channel. No areas of damage were observed.

In addition to the above, the fuel channel was removed from LJSO47 and an inspection was performed on the fuel rods. There were no observed areas of fuel damage or overheating.

On November 26, 1987 a visual inspection was performed on the reactor internals in the area of interest surrounding the binding of fuel assembly LJSO47. The inspection included the peripheral fuel support fillet weld, the peripheral support casting and the top guide.

There were no observed areas of damage.

D. SERI submitted Operating Plant Experience Report 2281 to thE Institute of Nuclear Power Operations on November 25, 1987. The report described the incident and was submitted following the successful renoval of the fuel assembly from the core.

E. General Electric verbally notified domestic BWR-6 facilities of the incident. RICSIL No. 014, "Misalignment of BWR-6 Peripher.ti Fuel Bundles," was issued on December 14, 1987.

F. SERI documented the event in Incident Report 87-11-14. "GGNS Stuck Fuel Assembly."

G. An evaluation of the removed assembly was performed to detert.ine if further inspections were warranted. The results of that evaluation are summarized below.

General Electric has calculated the minimum critical power ratio for the stuck fuel assembly during cycle 2 operdtion. The results of this calculation snow excess margin to transition boiling.

Consequently, SERI has elindnated the possibility of thennal hydraulic damage to the stuck assemoly during cycle 2.

No damage to the stuck fuel assembly was expected to occur during the removal process. After the stuck assembly was removed, a video inspection was performed. The bundle was de-channeled during this video inspection. As noted in the Incident Report, no evidence of damage could be seen on either the channel or the bundle, J14AECM88101302 - 6

Attachment to AECM-88/0205 In SERI's opinion, this video inspection provides an adequate assessment of the bundle condition. In addition, SERI will not  ;

reinsert this fuel assembly without prior discussion with the NRC.

As such, further inspections of this fuel assembly are not expected to provide additional information, and so are not planned.

I A similar event occurred at a foreign BWR-6 in which a peripheral fuel assembly was misaligned from the support piece, operated through a I cycle, and found to be stuck dtring refueling operations. As part of i SERI's investigation of inspection needs and alternatives, this BWR plant was contacted. From discussion with a representative of this  !

fo *eign BWR, SERI learned that a video inspection had been performed l on their stuck assembly. No evidence of damage was seen during this video inspection, and according to General Electric the bundle has l since been reinserted in the core.

SERI has concluded that the stuck assembly experienced no thermal I hydraulic damage during cycle 2 operation and no damage during the removal process. These conclusions are based on analysis and an underwater video inspection. The assembly is not planned for reuse,  ;

and will not be reinserted without discussion with the NRC.

Consequently, no further evaluation is warranted at this time.

General Electric concurs with this position, t

V. CONCLUSION The stuck bundle was successfully removed without complications. SERI has completed those actions committed to in the request for enforcement discretion. Other BWR-6 facilities have been informed of the occurrence.

i No plans exist to reuse the formerly stuck assembly. Actions to preclude

! occurrence have been completed.

SERI plans no further followup actions at this time, i

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