ML20197B228
| ML20197B228 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/16/1997 |
| From: | Jeffery Wood CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2497, IEB-96-004, IEB-96-4, NUDOCS 9712230318 | |
| Download: ML20197B228 (9) | |
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$501 North State Route 2 Oak Ha@on Ohio 43449u9760 419-249-2300
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Docket Number 50-346,72-14 License Number NPF-3 Serial Number 2497 December 16, 1997 United States Nuclear Regulatory Commission Document Control Desk
. Washington, D. C. 20555-0001
Subject:
Final Responses to NRC Bulletin Number 96-04, " Chemical, Galvanic, or other Reactions in Spent Fue1 Storage and Transportation Casks," and Related Requests for Additional Information for the Davis-Besse Nuclear Power Station Ladies and Gentlemen:
Toledo Edison (TE) received Nuclear Regulatory Commission (NRC) Bulletin Number 96-04, (TE Log Number 1-3716), " Chemical, Galvanic, or other Reactions in Spent Fuel Storage and Transportation Casks," dated July 5,1996. On August 19,1996, TE provided an initial response (TE Serial Number 1-1106) which provided a schedule for responding to Action Items 1(a),1(b),
1(c),1(d) and 2, of the cubject bulletin. The TE response schedule was based on the projected schedule provided by VECTRA Technologies, Inc. (VECTRA) for review and assessment of the bulletin's required actions. VECTRA submitted their initial assessment and response to Action Items 1(a),1(b) and 1(c) of Bulletin 96-04 (VECTRA Document Number 31-89604-102, Revision 0) on August 16,1996, and committed to provide a supplemental report for these three Action Items on or before October 20,1996. The VECTRA supplemental report (VECTRA Document Numbr 31-B9604-102, Revision 1), which detailed the complete results of their Part I test program, u submitted on October 18,1996. Subsequently, TE completed review of the
- VECTRA _ supplemental report and provided a plant-specific response (TE Serial Number 2425) to Action Items 1(a),1(b) and 1(c) for the Davis-Besse Nuclear Power Station (DBNPS) on December 17,1996 and committed to provide the TE response to Action items 1(d) and 2, after VECTRA had completed their assessment of these two items.
~ VECTRA received a Request for Additional Information (RAI) dated March 24,1997, after the 1NRC review was completed of the msponses provided by VECTRA and the utilities using the
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Standardized NUHOMS System (SNS). A parallel RAI was made to the utilities us which, in part, referenced the VECTRA response. The TE RAI " Request for Additional -
-Information - NRC Bulletin 96-04, Chemical, Galvanic, or Other Reactions in Spent Fuel Storage and Transportation Casks,"(TE Log Number 1-3817) was dated April.11,1997.
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Doc'ket Number 50-346,72-14
' License Number NPF-3 Serial Number 2497 -
Page 2 VECTRA submitted their response to Action items 1(d) and 2 (VECTRA Report Number 31-B9604-103) of Bulletin 96-04, on April 30,1997.
As a result of the NRC RAI to VECTRA, a revised response wa, submitted by VECTRA for Action items 1(a),1(b) and 1(c) on August 5,1947. This submittal included an enclosure to answer the specific questions of their RAI and VECTRA Report Number 31-B9604-102, revision 2, which incorporated the answers to the VECTRA RAI.
To allow, for a consolidated review of all the VECTRA submittals, on July 28,1997, TE commit-ted (TE Serial Number 2475) to submit a response to Bulletin 96-04, Action Items 1(d) and 2, plus the response to the RAI (TE Log Number 1-3817) issued to TE by October 29,1997. On October 27,1997, Mr. A. G. Hansen, NRC Project Manager for the DBNPS, was informed by telephone conference that submittal of this response would be delayed until the week of November 10,1997.
On November 6,1997, Marissa Bailey of the NRC Spent Fuel Project Office informed TE by telephone that the NRC was going to accept the VECTRA responses to Bulletin 96-04 and that another RAI would be issued to TE. In this telephone conference, TE stated that the final TE response to Bulletin 96-04 and the new RAI would be submitted by the due date specified in the new RAI. The subsequent RAI received (TE Log Number 5172) was Med November 17,1997 and s.seded in entirety the previous RAI (TE Log Number 1-3817,1 ed April 11,1997. The NRC also issued " Safety Evaluation of VECTRA Technologies Response to NRC Bulletin 96-04 for the NUHOMS-24P and NUHOMS-7P Dry Spent Fuel Storage Systems" on November 17, 1997, (TE External Correspondence Number EXT-97-02028) in support of the NRC acceptance of the VECTRA responses.
The submittals made by VECTRA and the NRC Safety Evaluation of the VECTRA bulletin responses have been reviewed by TE. Attachment 1, NRC Bulletin 96-04 Responses, summarizes the TE responses for Action items 1(a) and 1(b), revises the TE response to Action Item 1(c),
provides the TE response for Action items 1(d) and 2, and respo.ds to the RAI issued to TE on November 17,1997.
Should you have any questions or require additional information, please contact Mr. James L.
Frech, Manager - Regulatory Affairs, at (419) 321-8466.
Very truly yours,
, :i I LM/laj cc:
A. B. Beach, Regional Administrator, NRC Region Ill S. J. Campbell, DB-1 NRC Senior Resident Inspector A. G. Hansen, DB 1 NRC/NRR Project Manager Utility Radiological Safety Board
_ ' : Doc'ket Number 50-346,72i14 <
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License Number NPF-3' r
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.. Serial Number 2497" j
. Enclosure
'Page1" RESPONSE TO NRC BULLETIN 96-04 FOR.
- DAVIS-BESSE NUCLEAR POWER STATION!
o UNIT NUMBER 1 J
This letter is submitted in conformance with Atomic Energy Act of 1954 Section 182a as
. amended and 10CFR50.54(f), in response to NRC Bulletin 96-04, (Log No.1-3716), " Chemical, Galvanic, or Other Reactions in Spent Fuel Storage and Transportation Casks."
By:
[P J.fWood, Vice President - Nuclear Sworn to and subscribed before me this -16th Day of December,1997.
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Notary Public, Statsfof Ohio Nora-Lynn Flood
-My Commission' expires September 4, 2002.
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' Docket Number 50-346,72-14
- License Number NPF-3 Serial Number 2497-Attachinent 1 4
Page 1 of 6 NUCLEAR REGULATORY COMMISSION BULLETIN 96-04 RESPONSES A. Summary of Responsy to Action Items 1(a) and 1(b)
Reauested Actions 1(a) Review the cask materials, including coatings, iobricants, and cleaning agents, to determine whether chemical, galvanic, or other reactions among the materials, contents, and environment can occur during any phase ofloading, unloading, and handling, storage, and transportation. Consideration should be given to all environments that may be encountered under normal, off-normal, or accident conditions.
1(b) Evaluate the effects of any identified reactions to determine if any adverse conditions could result during cask operations, including loading and unloading. Consideration should be given, but not limited, to:
(i) generation of flammable or explosive quantities of hydrogen or other combustible gases; and (ii) increased neutron multiplication in the fuel in a cask because of boron precipitation from a chemical reaction among the borated water and cask materials.
Summary of Responses-The Toledo Edison (TE) response for these two Action Items (TE Serial Number 2425) was submitted on December 17,1996. This response is supported by +e VECTRA Part I report submitted by VECTRA on October 18,1996 (VECTRA Document Ember 31-B9604-102, Revision 1), which was further amended as Revision 2 and submitted by VECTRA to the NRC on August 5,1997. The NRC stated in its letter of November 17,1997 to TE, that VECTRA had satisfied the requested actions and required responses to the bulletin.
4 B. Revised Response to Action Item 1(c)
Reouested Action 1(c) Review current cask operating procedures to determine if adequate controls and procedures are in place to minimize hazardous conditions that may be created by any identified reactions.
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Doc'ket Number 50-346,72-14 License Number NPF-3 Serial Number 2497 Page 2nf 6 Summary of Responses The TE response to this Action Item was submitted on December 17,1996,(TE Serial Number 2425). This response was supported by the VECTRA Pnrt I report (VECTRA Document Number 31-B9604-102, Revision 1) submitted by VECTRA on October 18,1996.
As a result of the NRC review of these responses, a Request For Additional Infonnation (RAI) was made to TE on April 11,197, (TE Log Number 1-3817). The RAI (TE Log Number 1-3817) was superseded by a new RAI (TE Log Number 5172) made to TE on November 17,1997. Revision 2 of the VECTRA Document Number 31-B9604-102 is responsive to the concems identified by the NRC in the RAI issued to VECTRA. The revised TE response to Action Item 1(c) is embodied in the TE response to the NRC RAI (TE Log Number 5172) found in Section D of this attachment.
C. Responses to Action Items l(d) and 2 Reauested Action 1(d) Evaluate the effects of any identified reactions to determine if their reaction products could reduce the overallintegrity of the cask or its contents during storage or transportation. Determine if the reaction products could adversely affect the cask ability to maintain the structural integrity and retrievability of the spent fuel tk ughout the term of the license or to transport fuel safely. Consideration should be given, but not limited, to:
(i) cl.anges in cask and fuel cladding thermal properties, such as emissivity; (ii) bi iding of mechanical surfaces, especially fuel-to-basket clearances; and (iii) degradation of any safety components, either caused directly by the effects of the reactions, or by the effects of the reactions combined with the effects of long-term exposure of the materials to neutron and gamma radiation, high temperatures, or other possible canditions.
Response
VECTRA submitted a response to this Action Item on April 30,1997 (VECTRA Document Number 31-B9604-103, Revision 0) which is responsive to the Requested Action for the DBNPS. The VECTRA report summrizes their methodology for evaluating this item. This methodology assessed the by-products of the hydrogen generation reaction and the impact on the overall integrity of the Dry Shielded Canister (DSC) and its contents. This evaluation concluded that:
Doc'ket Number 50-346,72-14 License Number NPF-3 Serial Number 2497 Page 3 of 6 Thermal properties of the cask components remain unaffected by the reaction products because the oxide film produced by the hydrogen generation reaction is only a few microns thick and has a negligible impact on the heat transfer inside the DSC.
Retrievability due to mechanical binding and criticality performance are not impacted by the hydrogen generation reaction because neither the fuel nor DSC internals' geometry is changed due $ the minimal oxide film formation.
The NRC stated in its letter of November 17,1997, to TE, that VECTRA had satisfied the requested actions and required responses to the bulletin.
Reauested Action 2.
For storage casks currently loaded with spent fuel, determine the extent, if any, of the chemical, galvanic, or other reactions that have occurred, and the effect of these reactions on the cask ability to maintain the structural integ:ity and retrievability of the spent fuel throughout the term of the license.
Response
VECTRA submitted a response to this Actio,'.cm on April 30,1997,(VECTRA Document Number 31-B9604-103, Revision 0) which is i.,ponsive to the Required Action for the DBNPS. Hydrogen generation is limited to the time during which the DSC aluminum surfaces are in contact with borated water. After the DSC is drained of borated water, vacuum dried and inerted with helium, no additional hydrogen is expected to be formed by this mechanism. The NRC stated in its letter of November 17,1997 to TE, that VECTRA had satisfied the requested actions and required responses to the bulletin.
D. Resoonse to the Reauest For Additional Information Dated November 17.1997 Toledo Edison received a Request For Additional Information (TE Log Number 1-3817) dated April i 1,1997, with regard to the TE response (TE Serial Number 24-25) submitted for Actions items 1(a),1(b) and 1(c). In the letter to TE transmitting this RAI, the NRC expressed significant concern that the TE response to Action Item 1(c) contained in TE Serial Number 2425, submitted on December 17,1996, stated that TE would al'ow the hydrogen concentration to rise to combustible levels before taking corrective action. The NRC furtFcr stated that the TE response was insufficient in that it did not provide a specific hydrogen concentration at which to initiate corrective action to lower hydrogen concentration. By the response provided, TE did not intend to allow hydrogen concentration to rise to a concentration that would initiate combustion during welding or cutting operations. Toledo Edison agrees with the NRC Staff acknowledgment that 60 DSCs, at four different reactor sites, have been loaded and welded without any type of ignition indications on incidents, and that the staff does not h7e a safety issue, at this time, regarding the use of the NUHOMS system. This conclusion is further supported by the Safety Evaluation of VECTRA's
Docket Number 50-346,72-14
- License Number NPF-3 Serial Number 2497 Page 4 of 6 response to Bulletin 96-04 for the NUHOMS-24P Dry Spent Fuel Storage System issued by the NRC on November 17,1997.
The NRC issued to TE," Request for Additional Information Based on the Nuclear Regulatory Commission's Acceptance of VECTRA Technologies' Response to NRC Bulletin 96-04" (TE Log Number 5172) on November 17,1997, which superseded in its entirety the RAI (TE Log Number 1-3817) dated April i1,19" 7. The following responses supersede the TE response to Action item 1(c) submitted on December 17,1996, within TE Serial Number 2425. The NRC letter transmitting the RAI contained the following statements:
VECTRA's bulletin response recommended adopting 60% of the lower flammability limit of hydrogen (i.e.,2.4% hydrogen by volume) as a safe upper limit for the hydrogen cencentration in the vapor space of the NUHOMS Dry Shielded Canister (DSC) before and during welding or cutting operations. VECTRA also recommended monitoring the DSC vapor space at a frequencv to be assessed by each NUHOMS user. For DSCs with flame-sprayed aluminum, the staff believes that the DSC vapor space should be monitored continuously during welding or cutting to ensure that VECTRA's recommended safe upper limit is not exceeded.
As requested in the enclosed RAI, please indicate whether you agree with and how you will in plement VECTRA's response and recommendations. If you do not plan to implement any or all of VECTRA's recommendations, describe andjustify your alternative course of action.
The November 17,1997, RAI specifically requested TE to:
Describe in detail how the recommendations made in the VECTRA Technologies, Inc.
(VECTRA), Report No. 31-B9604-102, Revision 2, for hydrogen control and monitoring will be implemented. At a minimum, the information provided should:
Reauest 1 Describe the methods used to control and monitor hydrogen before and during welding, grinding, or cutting operations associated with loading or unloading activities.
Response
Based upon a review of the VECTRA submittals, the DBNPS procedures for loading and/or unloading will be revised prior to the next dry spent fuel storage campaign which at this time is dependent on resolution of the NRC Demand for Information issued to VECTRA. Two methods, described below, will be used to monitor hydrogen concentv. tion. Control of hydrogen is addressed in the response to Request 3 found below.
I INket Number 50 346,7214
' License Number NPF 3 Serial Number 2497 Attachment i Page 5 of 6 During lording operations, a DSC vapor space does not exist until the DSC liquid level is lowered m preparation for welding of the DSC Inner Top Cover. After the liquid level is lowered and prior to initiating welding of the DSC Inner Top Cover, continuous monitoring of the DSC Vapor Space will be initiated to analyze for hydrogen concentration. Monitoring I
will be set up to draw a continuous sample through a hydrogen analyzer that will provide a continuous measurement of DSC vapor space hydrogen concentration. A hydrogen concentration of less than 2A p.. at hydrogen by volume will be the safe upper limit applied prior to commencing the DSC Inner Top Cover tack welds. The procedure, " Dry Fuel Storage Loading"(DB NE-06472), wi'l provide for assessment of the initial results of this monitoring prior to commencing tack welding operations. The DSC vapor space will be j
- continuously monitored until the DSC/ Inner Top Cover welding is complete.
Just prior to striking an arc to initiate welding, a sniff :: heck will be made in the immediate vicinity of the Inner Top Cover weld with a hand held hydrogen gas detector (such as a GasTech Trace Techtor) to detect leakage of hydrogen from the DSC vapor space past the shield plug and inner top cover. These actions will verify that a flammable concentration of hydrogen does not exist when a wcld are is struck.
Grinding of the DSr/ Inner Top Cover, while in place on the DSC, would only occur if a weld repair was m.cessary after inspection. Continuous sampling of the DSC vapor space will be in effect until the DSC/ inner Top Cover weld is complete, as stated above.
This sampling regimen will provide adequate assurance that a flammable concentration of hydrogen does not exist at the time welding operations for the DSC/ Inner Top Cover are in progress. Laboratory tests and analysis by VECTRA indicate the increase in hydrogen concentration in the time frame of this welding operation (approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) will not be excessive. When this weld is complete, the DSC vapor space will be isolated from any welding or grinding ignition source.
During DSC unloading operations, access to the inside of the DSC is not obtained until the vent port cover plate is removed. The procedure," Dry Fuel Storage Unloading"(DB-NE-06471), requires a gas sample of the DSC atmosphere be obtained and evaluated prior to venting the DSC to determine precautions to be employed during DSC venting. This sample would indicate the presence of any hydrogen. Continuous monitoring of the DSC atmosphere will t e initiated after DSC reflooding and will continue until the DSC Inner Top Cover cutting is complete.
Reauest 2 Specify the DSC hydrogen concentration that will be set as the safe upper limit before and during welding or cutting operations.
DocLet Number 50-346,72-14 License Number NPF-3 Serial Number 2497 Page 6 of 6
Response
i VECTRA's response dated August 6,1997, recommended adoption of 60 percent of the Irwer Flammability Limit (LFL) as a safe upper limit before and during welding or cutting operations. The DBNPS will adopt 2.4 percent of hydrogen by volume as a safe upper limit for DSC vapor space hydrogen concentration before and during DSC welding / cutting operations as applied to the procedures described in the responses to Request Numbers 1 and
- 3. This criteria, as stated in the August 6,1997, VECTRA response,is based or ANSFISA-S12.13, Part 1 - 1986, "Perfonnance Requirements, Combustible Gas Detectors."
Reauest 3 Describe the actions to be taken if the safe upper limit b exceedsd.
Ru.aonse i
If the acceptance criteda for hydrogen concentration is exceeded for any of the samples specified above, loading or unloading operations will be suspended until the hydrogen concentration condition is evaluated and corrective actions are completed to control the hydrogen concentration by ventilating or purging the DSC vapor space with nitrogen.
Ventilation or purging of the DSC vapor space will be of a sufficient volume to reduce the hydrogen concentration of the vapor space to a concentration below the acceptance criteria stated above to accommodate completion of welding, grinding or cutting operations. The concentration of hydrogen in the vapor space that will be acceptable to recomr. :nce welding, grinding or cutting operauons will depend on factors such as the apparent rate of hydrogen generation within the DSC and the projected time required to complete the operation being performed. Ventilation or purging will be performed, as necessary, to ensure that hydrogen concentrations remain below 2.4 percent hydrogen by volume (60 percent of the Lil) during the welding, grinding or cutting operations discussed in the response to Request Number 1.