ML20141B411

Responds to Util Responding to GL 96-04, Boraflex Degradation in Spent Fuel Pool Storage Racks. Util Approach Acceptable to Resolve Issues of Boraflex Degradation in Subj Gl.Results of Evaluation Requested

ML20141B411
Person / Time
Site:	Grand Gulf
Issue date:	05/14/1997
From:	Donohew J NRC (Affiliation Not Assigned)
To:	Hagan J ENTERGY OPERATIONS, INC.
References
GL-96-04, GL-96-4, TAC-M95952, NUDOCS 9705150272
Download: ML20141B411 (5)

Text

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g-  % UNf7ED STATES

)] NUCLEAR REGULATORY COMMISSION

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.{ WASHINGTON. D.C. 20056 4001 J'

May 14, 1997

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'Mr. Joseph'J. Hagan .

, Vice. President, Operations GGNS

. .Entergy Operations, Inc. ,

P. O. Box 756

Port Gibson, MS 39150 i

~

SUBJECT:

-COMPLETION OF LICENSING ACTION REVIEW FOR GENERIC LETTER 96-04, ,

' - "BORAFLEX DEGRADATION IN SPENT FUEL POOL STORAGE RACKS," FOR  !

p GRAND GULF NUCLEAR STATION, UNIT l'(TAC NO. M95952)

Dear.Mr. Hagan:

l

Generic. Letter (GL) ~ 96-04, "Boraflex Degradation in Spent Fuel Pool Storage ,

L Racks," was issued by the Nuclear Regulatory Commission (NRC) to licensees on i June 26, 1996, to address the degradation of Boraflex material in spent fuel  !

storage racks. The GL requested that you (1) assess the capability of the ,

'Boraflex to maintain a 5-percent subcriticality margin and (2) to submit a j

-plan describing any proposed actions if this subcriticality margin cannot be i maintained by the Boraflex because of current or projected degradation of the  :'

material. You responded to the GL in your letter of October 16, 1996 (GNRO-96/00118), for Grand Gulf Nuclear Station, Unit 1 (GGNS).

In your response, you stated that the storage racks in the spent fuel pool and upper containment pool at GGNS use Boraflex as a neutron absorber to maintain

! 'the required subcriticality margin. The Boraflex is enclosed between stainless steel sheets with the edge strips welded in place to frame the Boraflex. A program monitors Borafle) Lehavior through the removal of coupon L specimens which are periodically removed and tested to determine the size and

' frequency distribution of gaps in the Boraflex panels. Tests are also e conducted each cycle in the same area of the spent fuel pool where the most j .

recently discharged spent fuel is stored. Following 10 to 14 months of irradiation, an operating cycle is about 18 months, the spent fuel is removed

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and tests are performed on at least 50 rack cells. These tests were initiated

. after the receipt of Information Notice (IN) No. 87-43 alerting licensees to the degradation of Boraflex panels.in the high-density spent fuel- racks at

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Quad Cities, Unit 1. The results, and an analysis of the results, for the six tests were' included in your letter of October'16,1996.

After the IN, a criticality analysis was also performed to demonstrate the t

safety of the storage racks at GGNS with Boraflex gaps as large as 6 inches

• and. submitted to the NRC on February 27,.'1989. On April 26 and June 7, 1990,  ;

i-an additional. analysis was submitted to address the storage of additional fuel  !

types,' The' analysis assumed that 6-inch gaps were present in the Boraflex panels.and included a 10% reduction in the B-10 areal density as an allowance to accommodate potential degradation due to water ingress. This analysis was-

. approved by NRC in its letter of July 16, 1990. j 13 * '

9705150272 97051'4

, NRC RECelHR COPY  :

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6 Joseph J. Hagan -

2-Because the sixth test and last in-pool test has shown gap sizes greater than .

the 6 inches assumed in the previous criticality analysis, you have stated t that the criticality analysis is being revised to include the results from the  ;

sixth test and an allowance.for Boraflex degradation due to water ingress.

Because the irradiation dose to the racks from the most recently discharged spent fuel in the test area is significantly higher than the other racks outside the test area, you state that the dose to these other racks will remain below the dose corresponding to the fifth test through the end of Cycle 9, the current operating cycle, and have placed the spent fuel from the

last refueling outage outside the test area. Because criticality analysis  !

assumptions were confirmed to bound the Boraflex configuration from the fifth test, you stated that the 5-percent subcriticality margin will be maintained 1 throuah the current operating cycle. You also stated that the revised analy' sis will be completed before the end of Cycle 9 and the next refueling

outage when spent fuel will again be placed in the spent fuel pool.

In addition to the criticality reanalysis to ensure that the 5-percent subcriticality margin will be meet for the life of the racks, you stated that .

4 . the in-pool tests will be continued until it is demonstrated that the Boraflex degradation in the panels .has reached equilibrium and it is confirmed that the  ;

test are bounded by the criticality analysis. l 4 Because silica concentrations in the spent fuel pool water are indications of I degradation of the Boraflex in the racks due to water ingress, you have provided pool silica concentrations from 1988 to April 1996. You pointed out that the rate of increase in silica concentrations following each refueling i outage has been slightly steeper in the most recent refueling outages. You stated that the indication of Boraflex degradation based on this change in i silica concentrations depends on a detailed evaluation of the pool design and operation which has not been conducted at GGNS. Because the Electric Power Research Institute has developed a system to perform this evaluation and the

system has been successfully applied at another site, you stated that a model is being developed to use this system to perform a detailed evaluation at GGNS before the next and the future refueling outages.

The staff has evaluated the information provided in your letter of October 16, 1996. Based on our evaluation, we conclude that your approach is acceptable to resolve the issues of Boraflex degradation in GL 96-04. Because we have been informed by your staff that the subcriticality reanalysis has been j completed, we request that you submit the results of the reanalysis, and your

conclusions and actions concerning the spent fuel racks and testing the o Boraflex material within 120 days of receipt of this letter. We also request

] that you provide the' results of the detailed silica concentration evaluation 4

of the GGNS spent fuel pool to be performed for the refueling outage, within 90 days after the evaluation is completed.

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Joseph J.. Hagan 1 If you have any questions regarding this matter, please contact Jack N.

Donohew at 301-415-1307. This letter closes out the staff's review under TAC No. M95952.

Sincerely,

h. N Jack N. Donohew, Senior Project Manager

[

N Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-416 cc: See next page 3

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o Joseph J. Hagan If you have any questions regarding this matter, please contact Jack N.

Donohew at 301-415-1307. This letter closes out the staff's review under TAC No. M95952. ,

i Sincerely, 1

A b ( 5/i +A 7 )

Jack N. Donohew, Senior Project Manager 1 Project Directorate IV-1 J Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-416 cc: See next page DISTRIBUTION:

Docket File PUBLIC PD4-1 r/f JRoe EAdensam (EGAl) JDonohew PGwynn, RIV ACRS OGC (15B18)

CRawes WBeckner SBloom JLyons Document Name: GG95952.LTR y[ M 0FC PM/PDh h LA/PD4-1 BC:SRNB/NRR LPM:PD4-2 NAME JDonohNp CHawesQn// JLyo'nY SBloomh DATE [/ *( /97 ,5 / 6 /97 // JZ-jg7 [/9 / /97 COPY kN0 V

YES/N0 YES/N0 k N0 0FFICIAL RECORD COPY

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. Nr.JosephJ.Hagan

~ Entcegy Operations, Inc.

Grand Gulf Nuclear Station j j cc:-

Executive'Vice President General Manager, GGNS

& Chief. Operating Officer Entergy Operations, Inc. >

Entergy Operations, Inc. P. O. Box 756  !

P.-O. Box 31995- Port Gibson, MS 39150 ,

- Jackson, MS 39286-1995 l Attorney General l Wise, Carter.. Child & Caraway Department of Justice >

P._0.. Box 651~ State of Louisiana  ;

-Jackson, MS 39205 P. 0. Box 94005 )

Baton Rouge, LA 70804-9005 i Winston.&.Strawn '

1400 L Street, N.W. - 12th Floor State Health Officer Washington, DC- 20005-3502 - State Board of Health ,

P. O. Box 1700 '

Director Jackson, MS 39205 Division of Solid Waste Management  ;

Mississippi Department of Natural Office of the Governor  :

Resources. State of Mississippi P. 0. Box 10385 Jackson, MS 39201-Jackson, MS 39209 i Attorney General 4 President, Asst. Attorney General claiborne County Board of Supervisors State of Mississippi Port Gibson, MS 39150 P. O. Box 22947 Jackson, MS 39225 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Vice President, Operations Support i 611 Ryan Plaza Drive, Suite 1000 Entergy Operations, Inc.

L Arlington, TX 76011 P.O. Box 31995 Jackson, MS 39286-1995

- Senior Resident Inspector i-

- U. S. Nuclear Regulatory Commission Director, Nuclear Safety Route 2, Box 399 and Regulatory Affairs Port Gibson, MS 39150 Entergy Operations, Inc.

i P.O. Box 756 Manager of Operations Port Gibson, MS 39150 Bechtel Power Corporation

- P.O. Box 2166 Houston, TX -77252-2166 1

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