L-96-004, Supplemental Response to NRC Generic Letter 96-04, Boraflex Degradation in Spent Fuel Pool Storage Racks
| ML051230320 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/25/2005 |
| From: | Scarola J Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GL-96-004, HNP-05-004 | |
| Download: ML051230320 (4) | |
Text
James Scarola g3 Progress EnergUy J1ce Pepsi~daent Harris Nuclear Plant Progress Energy Carolinas. Inc.
APR 2 5 2005 Serial: HNP-05-004 U.S. Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO. I DOCKET NO. 50-400/LICENSE NO. NPF-63 SUPPLEMENTAL RESPONSE TO NRC GENERIC LETTER 96-04, "BORAFLEX DEGRADATION IN SPENT FUEL POOL STORAGE RACKS" Ladies and Gentlemen:
On June 26, 1996, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 96-04, "Boraflex Degradation In Spent Fuel Pool Storage Racks," which requested licensees that use Boraflex to (1) assess the capability of the Boraflex to maintain a 5-percent subcriticality margin and (2) submit to the NRC a plan describing its proposed actions if this subcriticality margin cannot be maintained by Boraflex material because of current or projected future Boraflex degradation. On October 24, 1996, Carolina Power and Light Company (CP&L), now doing business as Progress Energy Carolinas, Inc., submitted the Harris Nuclear Plant (HNP) response to the Generic Letter.
This letter is to supplement the previous response to GL 96-04 by providing recent information regarding Boraflex management of both the PWR and BWR spent fuel racks at HNP. provides the supplemented response. Please refer any questions regarding this letter to Mr. Dave Corlett at (919) 362-3137.
I declare, under penalty of perjury, that the attached information is true and correct (Executed on APR 2 5 2005 )*
Sincerely, JS/rgh
Attachment:
- 1. Supplemental Response to Generic Letter (GL) 96-04, "Boraflex Degradation In Spent Fuel Pool Storage Racks" c:
Mr. R. A. Musser, NRC Sr. Resident Inspector Mr. C. P. Patel, NRC Project Manager Dr. W. D. Travers, NRC Regional Administrator P.O.
Box 165 New Hill, NC 27562 T > 919.362.2502 F > 919.362.2095 to SERIAL: HNP-05-004 SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO. I DOCKET NO. 50-400/LICENSE NO. NPF-63 SUPPLEMENTAL RESPONSE TO GENERIC LETTER (GL) 96-04, "BORAFLEX DEGRADATION IN SPENT FUEL POOL STORAGE RACKS" All licensees of power reactors with installed spent fuel pool storage racks containing the neutron absorber Boraflex are requested to:
- 1. Provide an assessment of the physical condition of tihe Boraflex, including any deterioration, on the basis of current accumulated gamma exposure and possible water ingress to the Boraflex and state whether a subcritical margin of S percent can be maintainedfor the racks in unborated water. Monitoring programs or calculational models in effect or being developed, or an estimation of anticipated concerns based on the specific rack design, are considered an appropriate basis for this response.
Response
The Harris Nuclear Plant (HNP) currently stores spent fuel from Brunswick Units I & 2, Harris Unit 1, and Robinson Unit 2 in its spent fuel pools. Several of the racks contain Boraflex.
Boraflex degradation is occurring in both the BWR and PWR spent fuel racks as confirmed by recent calculations performed by NETCO using the RACKLIFE code. The RACKLIFE calculation shows that as of October 2004, the average degradation for the PWR Boraflex racks is approximately 15%. The average loss in the BWR Boraflex racks is less than 4%,
which is substantially less than the PWR racks due to the lower gamma exposure in the BWR racks. Evaluations have been performed for the current operating cycle to verify that the Boraflex racks meet the 5-percent subcriticality margin in unborated water. HNP plans to perform new criticality analyses as needed to eliminate credit for Boraflex in both the BWR and PWR racks.
The RACKLIFE code is used to monitor the degradation. HNP also monitors Boraflex degradation using long-term Boraflex surveillance coupons and silica trending. The long-term coupons are used to represent the average loss of Boraflex. The most recent long-term coupon (removed in 2002) indicated approximately 17% Boraflex degradation. Silica trend data in the spent fuel pools, as discussed later, continues to show an increasing trend, indicative of the Boraflex degradation.
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..7 Attachment I to SERIAL: HNP-05-004 All licensees are further requested to:
- 2. Szubmit to the NRC a description of any proposed actions to monitor or confirm that this 5-percent subcriticality margin can be maintainedfor the lifetime of the storage racks and describe what corrective actions could be taken in the event it cannot be maintained.
Response
As discussed above, NETCO performed RACKLIFE calculations to predict Boraflex rack degradation. HNP monitors Boraflex degradation using long-term Boraflex surveillance coupons and silica trending. The long-term coupons are used to represent the average loss of Boraflex. Silica trend data in the spent fuel pools continues to show an increasing trend, indicative of the Boraflex degradation.
Evaluations have been performed for the current operating cycle to verify that the Boraflex racks meet the 5-percent subcriticality margin in unborated water. HNP plans to perform new criticality analyses as needed to eliminate credit for Boraflex in both the BWR and PWR racks.
- 3. Licensees should describe the resultsfrom any previous post operational blackness tests and state whether blackness testing, or other in-situ tests or measurements, will be periodically performed.
Response
HNP has not performed any blackness testing and does not intend to do so. Long-term surveillance coupons results correlate well with the RACKLIFE predictions. HNP plans to perform new criticality analyses to eliminate credit for Boraflex.
- 4. Chronological trends ofpool reactive silica levels, along wvith the timing of significant events such as refuelings, pool silica cleanups, etc., should be provided. Implications ofhow these pool silica levels relate to Boraflex performance should be described.
Response
Silica trend data is attached which shows the silica concentration in spent fuel pools A and B and each refueling outage. Based on the silica concentration and the pool volumes, there is approximately 65kg of dissolved silica in the spent fuel pools. This mass represents an average boron loss of approximately 14% across all of the Boraflex racks, which correlates well with the current RACKLIFE estimate of HNP rack conditions. HNP has not performed pool silica cleanups.
Page Al-2 of 3 to SERIAL: HNP-05-004 HNP Silica RFO7 RFO8 RFO3 RFO4 RFO5 RFO6 RFO9 RFO10 RFO11 RF012 20000 -
18000 -
16000 -
14000 -
M 12000 a.
o 10000 -
U
~ 00 6000 -
4000-2000
-ed May-90 Sep-91 Jan-93 Jun-94 Oct-95 Mar-97 Jul-98 Date Dec-99 Apr-01 Sep-02 Jan-04 May-05 Oct-06 l
a Fuel Pool A Fuel Pool B -
Expon. (Fuel Pool A) ---
Expon. (Fuel Pool B)
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