L-87-424, Applicant Exhibit A-12,consisting of Util Forwarding Response to NRC 870901 Request for Addl Info Re Use of Boraflex in Rerack & Spent Fuel Pool Filter Demineralizer,Per 870612 Application for Amend to License
| ML20246M608 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 01/26/1989 |
| From: | Woody C FLORIDA POWER & LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| L-87-424, OLA-A-012, OLA-A-12, NUDOCS 8903270210 | |
| Download: ML20246M608 (9) | |
Text
g ~y-- -- . _ _ -
- P. O. 80x 14000. ANo SE ACn. 23WAM
/ - p & - l c3 -
. NUCLEAR REGULATORY COMMIS$10N
[/ '
Dochet No. 60' F6~0% Official Exh. No. __./_.2- -
in tne rnatter of //vick hv '/kd- M '
- - f ~DD aMetII?
Staff IDENTiflED W App!icant RECEIVED '
Intervenor REJECTED - DN OT 20 W Cont'g Off'r Contractor ~ OATE /~ M ~T f 7' Other Ylitness L-87-424 Reporter M t $cw Novru U. S. Nuclear Regulatory Commission l Atin: Document Control Desk Washington, D.C. 20555 1
Gentlemen:
~
Re: St. Lucie Unit I Docket No. 50-335 Spent Fuel Pool Rerack - Boroflex and Pool Cleanup By letter L-87-245, dated June 12, 1987, Florida Power & Light Company (FPL) submitted a proposed license amendment to permit replacement of the spent fuel pool rocks at St. Lucie Unit I to ensure that sufficient future capacity exists for storage of spent fuel.
By letter dated September I,1987 (E. G. Tourigny to C. O. Woody) the NRC Staff requested additional information in the area of the use of Boraflex in the rerock and the spent fuel pool filter demineralized it needed to continue its review of this proposed license amendment.
Attached is FPL's response to this request.
If additional information is required, please contact us.
Very truly yours,
..eth!!i.................... ... "n !!.iee!!n..!!....!?t!!!!!.
.'. oo
!!EEc" ng?" E!!fl"'
"(E IM!!,**
'25tpon UE" Group V i c esident UnE Am!cuun l Nuclear Energy ;q'u. u. gwW ",, ' "2L"
~1*
- Unj
- 9 g.
m,,isay gd;gustooi.=
, g.:gg gagg,,
sutaa.. u. oon, va.
,y,,
COW /EJW/gp Attachments cc: Dr. J. Nelson Grace, Regional Administrator, P s%n 11, USNRC Senior Resident inspector, USNRC, St. Lucie Plent 8903270210 890126 PDR ADOCK 05000335 G PDR EJWI/029/l an FPL Group company
m _.
4 I
ATTACHMENT ' ,
l RESPONSES TO NRC LETTER
- DATED SEPTEMBER 1,1987 (E. G. Tourigny to C. O. Woody)
-)
1 l
l' .l
'l EJ.WI/029/2 4'
\
I t i QUESTION #1 Recent anomalies have been identified in the Quad Cities and Point f Beach spent fuel pools due to Borafier shrinkage caused by I Irradiation. Based on this, provide justification to demonstrate j the continued acceptability of Boraflex for application in the St l Lucie spent fuel pool.
RESPONSE: Boraflex is the neutron absorbing poison used in the new St Lucie Unit i spent fuel racks. This material assures a shutdown margin of 5% with no boren in the spent fuel pool water. Additional details are provided in Section 4.7.2 of the St Lucie Plant Unit !
No 1 Spent Fuel Storage Facility Modification, Safety Analysis Report, transmitted via letter L-87-245 dated June 12, 1987.
Borafier has undergone extensive qualification testing to study l the effects of gamma and neutron irradiation in various l environments and to verify its structural integrity and stability l as a neutron absorbing material. These tests indicated that Borafier maintains its neutron attenuation capabilities when l subjected to an environment of berated water and 1.03 x 1011 l rads gamma radiation. Additionally, further tests (l) have
~
recently been conducted and preliminary results indicate that some l shrinkage (a maximum of cbout 2%) can occur in Boraflex, and that this shrinkage is complete at approximately 1 x 1010 rads gamma.
Three plants (Point Beach, Prairie Island and Quad Cities) have-l reported the results of their Boraflex surveillance. Of these three, the Boraflex material used at Point Beach Nuclear Power Plant has received the highest accumulated dose. This Boraflex material has been in use for a total of five years, and some of the Boraflex panels have received a 20 year-equivalent radiation dose due to the spent fuel management techniques used at Point Beach. The examination of the 2" x 2" sample coupons at Point Beach (which had a maximum exposure of 1.6 x 1010 rads gamma) showed that the coupons had experienced changes in physical
, characteristics such as color, size, hardness, and brittleness, with some sample thinning. However, the nuclear characteristics of the samples had not experienced any unexpected changes, and the boron absorbing properties of the samples met the acceptance criteria for maintaining the 5% A k/k shutdown margin. Point Beach also examined two full size (150" long x 8" wide) Boraflex panels, which had a maximum exposure of about 1 x 1010 rads gamma. These panels had a far lesser amount of physical changes than the 2" x 2" sample coupons. Thus, the examination of the Point Beach coupons and Boraflex panels indicates that, while some physical changes in Borafier may occur with accelerated radiation exposure, the Boraflex will retain its neutron absorbing characteristics.
(1) Irradiation Study of Boraflex Neutron Absorber, Interim Test Data, Bisco Products, Inc. Technical Report No NS-1-050 (Interim), June 25, 1987, j Rev. O.
l 0093L/0017L
)
i QUESTION #1 RESPONSE: Prairie Island has also examined two large (8" x 12") Borafier (continued) coupons (2). One of the coupons (which had a 6 month exposure) had an appearance similar to the as-manufactured Boraflex. The i other coupon (which had a 12 month exposure) had some slight "
physical changes similar to that experienced by the Bornflex panels at Point Beach.
The Boraflex panels in the Quad Cities racks (which had an exposure of about 109 rads gamma) were examined by a neutron surveillance technique. Gaps were noted in the Borafier panels, ,
and review of the size and number of gaps was performed. This :
review indicated that the gaps were attributed to a rack design j and fabrication process which did not allow the Boraflex to shrink without cracking. The Quad Cities racks were designed to hold smaller BWR fuel. The fabrication process required the Boraflex material to be glued to the stainless steel fuel rack walls. Also, the Boraflex remained tightly clamped during service. This did not allow for the predicted shrinkage of Boraflex and as such gaps developed. Less than half of the Boraflex panels at Quad Cities had gaps, varying in length up to a maximum of 4", and were located at various locations along the height of the panels. Akeff analysis of the Quad Cities spent fuel pool demonstrated that these gaps did not cause Quad cities -
to exceed its 0.95 limit on k egg.
The St Lucie racks are designed to hold the larger PWR fuel assemblies. The Boraflex sheets are not glued or clasped in place, but instead are supported by the stainless steel cell walls, stainless steel cover sheets and/or connecting strips, as illustrated in Figures 4-7 and 4-8 of the St Lucie Plant Unit No 1 Spent Fuel Storaae Facility Modification, Safety Analysis Report, transmitted via letter L-87-245 dated June 12, 1987.
, This arrangement allows the Boraflex sheets to contract freely in Region 2 and the exterior cell walls of Region 1, with no mechanism for restraint of the Borafier. For the interior cell 1 walls of Region 1, as illustrated on coordinate C-2 of Joseph Oat Corporation drawing D-8286, REV. 1, provided with Response ~1a of FPL Letter L-87-422, dated October 20, 1987, the Boraflex_taaimilarly allowed to contract without restraint unless and until the _
potential Boraflex shrinkage is sufficient to result in contact between the Boraflex cutouts and the cell wall to covet ih~eet spot welds. Should these spot welds act as a restraint ~oh the Boraflex,theywouldeffectivelypintheBoraflexinplje, preventing formation of any large gaps due to further shrinkage
- f Boraflex.
(2) May 26, 1987 memorandum from Ray W Lambert of Electric Power Research Institute to Attendees of Boraflex Review Meeting at the EPRI Workshop of May 20, 1987, EPRI-RP-2813-4.
0093L/0017L
QUESTION #1 RESPONSE: The St Lucie spent fuel racks design requires oversized (in (continued) length) Boraflex sheets to be used to provide a four inch shrinkage allowance, and that allowances for the elastic rebound of the Boraflex material be made before installation should the material be stretched during shipment or handling. The installation of the material in a stretched or restrained condition is not permitted. Florida Power & Light Company has a full-time Quality Assurance representative assigned to-the fabricator's shop to ensure that the specification requirements are adhered to. The installation of torn or cracked sheets of Boraflex is never permitted.
In conclusion, the St Lucie racks design features and fabrication procedures ensure that any shrinkage of the Boraflex sheets during in service irradiation will not result in potential criticality problems for the stored fuel by:
Using oversized Boraflex sheets to provide a four inch allowance for potential Boraflex shrinkage.
Allowing for Boraflex shrinkage with no restraint mechanism.
Preventing large gap formation over long ters irradiation in -
l Region 1 interior cell walls.
Providing for installation of Boraflex in a non-stretched condition, with no tears or cracks.
Maintaining a full-time Florida Power and Light Company Quality Assurance representative during fabrication in addition to the Boraflex manufacturer's and rack fabricator's own Quality Assurance staff to ensure specification l
. requirements are met.
Further, the experience at Point Beach indicates that some ;
physical changes may occur in Baraflex, but that the Boraflex i will retain its neutron attenuation properties. Both testing of i Boraflex and the experience at Quad Cities indicate that some shrinkage in Boraflex may occur, but that this shrinkage is limited to a maximum of about 2% of the length of the Borafier.
This resulted in some gaps in the Quad Cities Boraflex panels because the racks did not permit the Boraflex to shrink without cracking. In any case, due to the small size and the random orientation of the gaps, the calculated k erg of the Quad Cities spent fuel pool did not exceed the 0.95 11mit. Since there are differences in the installation process of the Borafier used at Quad Cities and St Lucie 1, the anomalie,s experienced at Quad Cities are not expected at St Lucie.
0093L/0017L
- ' _ - ~ - -
r.~-
L QUESTION #2 Based on the recent information pertaining to degradation of Boraflex, provide any changes to the inservice surveillance program for Boraflex and describe the frequency of examination and acceptance criteria for continued use.
RESPONSE: To confirm that the Boraflex at St Lucie is acceptable for continued use, as described in Section 4.8 " Testing and In-Service Surveillance" of the St Lucie Plant Unit No 1 Spent Fuel Storage Facility Modification, Safety Analysis Report, transmitted via L-87-245 dated June 12, 1987, FPL will conduct an in-service surveillance program. This program will evaluate both Region 1 and Region 2 Borafier samples.
Based on industry observations that small surveillance coupons i are not representative of (e.g., show significantly more degradation than) full length Boraflex sheets, FPL has increased the size of the surveillance coupons to 5" x 15". No other changes in FPL's surveillance program are proposed at this time, however, FPL plans to monitor the results of industry programs currently underway to evaluate the performance of Boraflex, and may propose changes in the surveillance program at a future date.
In the current program, two types of tests for each Region are planned - a long term test, with coupons surrounded by the same spent fuel assemblies during the entire irradiation period, and an accelerated test, with coupons surrounded by freshly discharged spent fuel assemblies each refueling. The long term test coupon examination frequency is after irradiation times of 90 days, 180 days, 1 year, 5 years, 10 years, 15 years, 25 years ;
and 35 years. The accelerated test coupon examination frequency is after each discharge from the second discharge to ninth discharge rack utilization. Acceptance criteria for continued
. use are dimensional changes no more than 2.5% from the original, hardness not less than 90% of the original, and minimum areal density of boron not less than the original. Any test results exceeding these limits will require an engineering evaluation to j determine continued acceptability.
l 0093L/0017L
~,
i 1
l l s QUESTION #3 Describe the corrective actions to be taken if degraded Boraflex specimens or absorber sheets are found in the spent fuel pool.
RESPONSE: FPL will follow the industry efforts concerning the performance of Boraflex. EPRI, Bisco .(the manufacturers of Boraflex) and several utilities are analyzing data as it becomes available and !
will notify the industry of the results. FPL will. evaluate these 1 results and determine whether any additional actions are warranted for the St Lucie Unit 1 spent fuel racks. I In the meantime, the St Lucia design provisions and fabrication i procedures indicated in response to Question #1 ensure that
) currently understood observations of Boraflex degradation will not result in potential criticality problems for the stored fuel.
In addition, the following corrective action options to assure continued safe storage of St Lucie spent fuel would be considered by FPL if unexpected degradation problems are detected:
- 1) The degraded Boraflex could be evaluated to determine whether the degradation and any expected future degradation would adversely affect FPL's ability to satisfy the .95 k gf limit for the St Lucie spent fuel pool. If the pool could still satisfy this limit, no further action would be neces sary.
- 2) Administrative controls could be imposed on the enrichment and/or burnup of fuel to be placed in or adjacent to storage cell locations that have degraded Boraflex to assure that the keff would remain less than or equal to the .95 limit.
, 3) A poison asterial such as a control rod or burnable poison l
, could be added to any new fuel assembly to be placed in a I storage cell with degraded Boraflex. This would reduce the keff to less than or equal to the .95 limit.
- 4) Poison plates could be added into the space between the fuel assembly and the cell wall to assure a k gg of less than or equal to .95. .
- 5) FPL has taken no credit for the 1720 ppa soluble boron concentration in the spent fuel pool water. This boron concentration is equivalent to a 2hke gg of .17 to .18 for the as-designed racks, as indicated in Table 3-1 of the St Lucie Plant Unit No 1 Spent Fual Storase Facility Modification, Safety Analysis Report, transmitted via letter L-87-245 dated June 12, 1987, resulting in subcriticality even with a postulated significant loss of boron from the Boraflex.
i 0093L/0017L
4 l
- j l
QUESTION #3 !
RESPONSE: 6) The storage cells with the degraded Boraflex could be blocked I off to prevent loading of any fuel assembly into the . cell. I
- 7) The storage racks with the degraded Boraflex could be coated with boron with a sufficient density to assure keff of less than or equal to .95.
1 l
O qe' fu 0093L/0017L
e QUESTION #4 Provide information regarding criteria for replacing the filter desineralizer of the spent fuel pool clean-up system to ensure its effectiveness to handle the high-density storage. j RESPONSE: The filter demineralized of the spent fuel pool clean-up system a' for St Lucie Unit No 1 consists of the purification filter and the ion exchanger. The criteria for replacing the purification filter and the ion exchanger is limited by operating procedures to not exceed a differential pressure of 20 psis across each i component. ;
No significant increase in the volume of solid radioactive wastes is expected due to the new high density spent fuel racks. Other plant operating experience with high density fuel storage has not indicated any noticeable increase in the solid radioactive wastes J generated by the increased fuel storage capability. Additional details are provided in Section 5.2 of the St Lucie Plant Unit No 1 Spent Fuel Storage Facility Modification, Safety Analysis Report, transmitted via letter L-87-245 dated June 12, 1987.
Therefore, the criteria for replacing the filter demineralized of the spent fuel pool clean-up system ensures its effectiveness to handle the high-density storage.
s 1
1 l
1 i
~
~
' 4 vW'e -&. . ., ', > y ,q **/
0093L/0017L i