ML17347B672
| ML17347B672 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 02/11/1987 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Lear G NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17347B673 | List: |
| References | |
| CON-NRC-87-12 VPNPD-87-48, NUDOCS 8702190666 | |
| Download: ML17347B672 (6) | |
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NSCOnS]n FleCtnC PO E'R COMPAN 231 W. MICHIGAN.P.O.BOX2046, MILWAUKEE.Wl53201 (414) 277.2345 VPNPD-87-48 NRC-87-12 February ll, 1987 Document Control Desk U.S.
NUCLEAR REGULATORY-COMMISSION Washington, D.C.
20555 Attention:
Mr. George Lear, Director PWR Project Directorate No.
1 Gentlemen:
DOCKET NOS.
50-266 AND 50-301 RESULTS OF EXAMINATION OF POISON INSERT ASSEMBLIES REMOVED FROM THE SPENT FUEL STORAGE RACKS POINT BEACH NUCLEAR PLANT, UNITS AND 2 Our July 23, 1986 letter advised you of our intent to remove two poison insert assemblies from the spent fuel storage racks and examine them.
In that letter, we also committed to provi-ding you the results of our examination.
Our report, "Results of Boraflex Examination, Point Beach Nuclear Plant" is enclosed with this letter and provides the examination results and our conclusions.
In the enclosure, we note that the full-length inserts in the spent fuel fuel racks are in excellent condition.
The full-length Boraflex inserts have behaved largely as predicted for the gamma exposure
- received, experiencing embrittlement and some dimensional shrinkage.
Overall, the Boraflex inserts were found suitable for performing their intended function.
On the other hand, the 2" x 2" samples in our surveillance program have reached a state where the Boraflex is friable and easily degraded.
The neutron attenuation properties of the samples were confirmed by testing at the Georgia Institute of Technology.
However, t)gir physical integrity showed deteri-oration at doses of 1 x 10 rads gamma and greater.
q3'
Document Control Desk February 11, 1987 Page 2
Currently, the average spent fuel rack position has accumulated a
gamma dose equivalent to six years exposure or 3 x 10 rads gamma.
Thelgamples have been irradiated to gamma exposures up to 1.6 x 10 rads gamma.
The full-length Boraflex insert ygich was examined received accelerated gamma exposures of 1 x 10
- rads, because it was adjacent to the sample location.
This dose is equivalent to 20 years.for the average spent fuel rack loca-tion.
We have concluded from the comparison of the two programs that the samples are not representative of the full-length Boraflex inserts.
The differences observed between the physical condi-tions of the full-length sheets and smaller samples are possibly attributable to differences in methods of encapsulation, Boraflex
- geometry, and handling frequency.
We do believe, however, that permeation of acidic spent fuel pool (SFP) water into Boraflex has a role in diminishing the integrity of the Boraflex material.
It further appears that the extent of SFP water permeation into Boraflex is a function of gamma dose received.
Our report pro-vides additional information to support these conclusions.
To monitor the condition of boraflex in the Point Beach spent fuel racks, we intend to modify future surveillance as follows:
1.
Since the samples do not appear representative of the full length Boraflex sheets and have limited value in predicting the onset of Boraflex degrada-tion in the spent fuel racks, we will terminate the Point Beach surveillance program in REI-25, "Spent Fuel Rack Neutron Absorbing Material Surveillance Specimen Program."
This includes eliminating the requirement to place freshly discharged spent fuel adjacent to the sample location every six months.
2.
In the place of the current surveillance
- program, we will examine another full-length Boraflex sheet in approximately 5 years from the present.
The recom-mended insert is at positjon SN-40/41, as it currently has exposures of 1.5 x 10 rads gamma.
3.
Subsequent examinations will be performed at locations and intervals to be determined after the next inspection.
4.
We will continue to follow the industry's development of data regarding Boraflex.
Document, Control Desk February ll, 1987 Page 3
- Overall, we believe our examination has confirmed the continued serviceability of the full-length Boraflex inserts in the'oint.
Beach spent fuel racks.
If you have questions concerning our
- report, please do not hesitate to contact us.
Very truly yours, C.
W. Fay Vice President Nuclear Power Enclosure Copy to NRC Resident Inspector NRC Regional Administrator, Region III
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