Reactor Protection System Power Supplies (Generic Letter 78-32)
GL78032
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
August 11, 1978
Docket No. 50-367
TO ALL FACILITIES ON ATTACHED LIST
Gentlemen:
SUBJECT: REACTOR PROTECTION SYSTEM POWER SUPPLIES
Criterion 2 of the Commission's General Design Criteria (Appendix A to 10
CFR Part 50) requires in part that systems important to safety, such as the
reactor protection system, be designed to withstand the effects of
earthquakes. Reactor protection systems are required to be Class IE
systems, hence they are seismic Category I. The normal reactor protection
system power supplies for most General Electric Company boiling water
reactor nuclear steam supply systems, except for those utilizing solid state
reactor protection systems, consist of redundant alternating current
motor-generator sets which are not seismically qualified.
During the course of our review of Georgia Power Company's operating license
application for its Edwin I. Hatch Nuclear Plant Unit No. 2 (Docket No. 50-
366), we questioned the adequacy of the protection afforded the reactor
protection system against possible sustained over-voltage, under-voltage, or
underfrequency conditions from the reactor protection system power supplies.
Specifically, we questioned the capability of the reactor protection system
power supplies to accommodate the effects of earthquakes without
jeopardizing the capability of the reactor protection system to to perform
its intended safety function.
We determined that a sequence of events initiated by an earthquake can be
postulated which could result in damage to the reactor protection system
components with the attendant potential loss of capability to scram the
plant. This sequence of events includes (1) the occurrence of an earthquake
that would cause the undetected failure of a voltage sensor, (2) the failure
of a motor-generator set resulting in an abnormal output voltage , (3) the
persistence of this abnormal output voltage, undetected by visual
observations and surveillance testing, for a time sufficient to damage
reactor protection system components, and (4) failure of these components in
such a manner that results in the loss of capability to scram the plant.
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We, therefore, required that prior to startup following the first scheduled
refueling outage, Georgia Power Company install Class IE systems approved by
us and capable of de-energizing the reactor protection system power supplies
when their output voltages exceed or fall below or their output frequencies
fall below limits within which the equipment being powered by the power
supplies has been designed and qualified to operate continuously and without
degradation. With such systems, the designs of the reactor protection system
power supplies will conform to the applicable requirements of Criterion 2 of
Appendix A to 10 CFR Part 50.
Consistent with our finding on Hatch Unit 2, we require that all applicants
for licenses to construct and operate plants utilizing General Electric
Company boiling water reactor nuclear steam supply systems with non-seismic
Category I alternating current motor-generator sets as the normal reactor
protection system power supplies install Class IE systems approved by us and
capable of de-energizing the reactor protection system power supplies when
their output voltages exceed or fall below or their output frequencies fall
below limits within which the equipment being powered by the power supplies
has been designed and qualified to operate continuously and without
degradation.
We will implement this requirement as follows:
(1) For those applicants with applications in the construction permit stage
of the review process, we request that within 30 days of your receipt
of this letter, you amend your application to reflect your commitment
to (a) install such systems prior to initial fuel loading and (b)
provide the details of the system design in your Final Safety Analysis
Report.
(2) For those applicants in the post-construction permit stage, we request
that within 30 days of your receipt of this letter, you document by
letter your commitment to (a) install such systems prior to initial
fuel loading and (b) provide the details of the system design in your
Final Safety Analysis Report.
(3) For those applicants with applications in the operating license stage
of the review process, we request that within 30 days of your receipt
of this letter, you amend your application to reflect your commitment
to (a) install such systems prior to initial fuel loading and (b)
advise use of your schedule for providing the details of the system
design in your Final Safety Analysis Report.
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- 3 - August 11, 1978
Because of the relatively large number of plants involved and the similarity
of the reactor protection system power supply designs, we anticipate that
you, the other affected applicants, and the General Electric Company may
wish to combine efforts in this matter. In the interest of standardization
and minimizing the impact of our review of these systems, we encourage such
a combined effort.
Sincerely,
Roger S. Boyd, Director
Division of Project Management
Office of Nuclear Reactor Regulation
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FACILITIES TO RECEIVE GENERIC LETTER NO. 26
PLANT DOCKET NUMBER (S)
Bailly 50-367
Clinton 1 & 2 60-461 & 462
Douglas Point 1 & 2 50-488 & 499
Fermi 2 50-341
Grand Gulf 1 & 2 50-416 & 417
Hope Creek 1 & 2 50-354 & 355
La Salle 1 & 2 50-373 & 374
Montague 1 & 2 50-496 & 497
Nine Mile Point 2 50-410
Perry 1 & 2 50-440 & 441
River Bend 1 & 2 50-458 & 459
Shoreham 50-322
Susquehanna 50-387 & 388
WNP-2 50-397
Zimmer 1 50-358
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