ML19263D331
| ML19263D331 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 03/20/1979 |
| From: | Goodwin C PORTLAND GENERAL ELECTRIC CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| TAC-06906, TAC-6906, NUDOCS 7903270467 | |
| Download: ML19263D331 (3) | |
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March 20, 1979 Trojan Nuclear Plant Docket 50-344 License NPF-1 Director of Nuclear Reactor Regulation ATTN:
Mr. A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Dear Sir:
The Nuclear Regulatory Commission, upon approval of Amendment 29 to Trojan's Operating License, requested that Portland General Electric furnish the results of radiation surveys which confirm the effectiveness of the modified biological shield design.
The radiation surveys have been completed and are summarized in the attachment. The results, obtained at 100 percent power, are for water bags over the inspection ports and no shielding over the reactor cavity annulus.
The results indicate that neutron dose rates throughou t the Containment are generally lower than predicted except for streaming in the vicinity of the reactor pressure vessel at Points 1, 3, and 3A.
At Point 3A, measured neutron dose rates are about three times higher than predicted.
Neutron dose rates below the operating floor (Elevation 93 ft) were less than 5 mrem /hr. The neutron measurements were taken using a PNR-4 neutron survey meter with an upper scale reading of 5000 mrem /hr. The maximum dose rate of 11.5 rem /hr. at Point 3A was extrapolated from 50 percent power data and subsequently confirmed by independent measure-ments by NRC Region V and Battelle Northwest Labs.
Battelle Northwest Labs is conducting a survey at operating nuclear sites to determine neutron energy spectra and response characteristics of various neutron monitoring devices. Trojan has participated in this 7\\
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Mr. A. Schwence r March 20, 1979 Paze two survey. Prelimina7 results from cther plants indicate thrt the PNR-4 survey meter may over-respond by a factor of three at the low to inter-mediate neutron energies typically found inside P'n~d Containments. This effect may explain the factor of three discrepancy between measured and predicted results.
Sincerely o
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C. Goodwin, Jr.
Assistant Vice President Thermal Plant Operation and Maintenance CG/JWL/JLT/4kkl0A16 Attachment
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