ML17334A348
| ML17334A348 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 12/07/1981 |
| From: | Hunter R INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| AEP:NRC:0642, AEP:NRC:642, NUDOCS 8112140013 | |
| Download: ML17334A348 (8) | |
Text
4 REGULATORY INFQRh"ATION DISTRIBUTION SYSTEM (RIDS)
'. ACCESSION NBR;8112140013 OOC ~ DATE: 81/12/07 NGTARIZED:
NC FACIL.:50-315 Oonal d C.
Cock Nuc1 ear Power P1 anti Uni t 1r Inciana 50-316 Donalo C ~.Cook nuclear Power Pl anti Uni t 2r Inoiana AUTH ~ NAIvE AL'THOR AFFILIATION HLrNTERrR ~ ST Inciana
& Michigan Electric Co ~
REC IP. hIAMt HEC IP IEN1'FF ILIATION DENTONrH ~ RE Gffice of Nuclear Reactor Regulationr Director DOCKET 00315 SI.BJECT; Not i fies containme itrs ~ Moni four cont DISTRIBUTION CODE:
TITLE: Gener al Dis that incorrect statement r e isolation function of nt area Monitor R-2 was mace in 780501<0608 4
1205 tor rr 2 ooes not automatically initiate closure of aine'ent instrument room valves.
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INDIANA L MICHIGAN ELECTRIC COMPANY P. O. BOX 18 BOWLING GREEN STATION NEW YORK, N. Y. 10004 December 7, 1981 AEP:NRC:0642 Donald C. Cook Nuclear Plant Unit Nos.
1 and 2
Docket Nos. 50-315 and 50-316 License Nos.
DPR-58 and DPR-74 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 0>>~ ~Vayu::aIm1c~
4I cc)eiIss'Icy
Dear Mr. Denton:
This letter is to inform you of an incorrect statement made in three gast submittals regarding the isolation function of the Containment Area Monitor (R-2) in Units 1 and 2 of. the Cook Plant.
The Post-TMI radiation monitoring requirements have caused us to initiate extensive design modifications to the Cook Plant's Radiation Monitoring System (RMS).
During a recent design review of the upgraded RMS it was found that, contrary to our previous belief that the three containment radiation monitoring channels R-2, R-11 and R-12 automatically initiated closure of all 14 containment purge supply and exhaust isolation
- valves, R-2 does not automatically initiate closure of the four (4)
Containment Instrument Room valves.
Each of the Instrument Room purge supply and exhaust lines has two 14" automatic isolation valves in series, one inside containment the other outside containment.
The three submittals mentioned above are:
- 1) our May 1, 1979 letter (AEP:NRC:00185) responding to Action Item 9 of IE Bulletin No.79-06A, 2) our June 8, 1979 letter (AEP".NRC:00114A) on the matter of containment purging during normal plant operation, item 3, and 3) our December 5,
1979 letter (AEP:NRC:00295A) providing additional information on the RMS as it relates to purge system operation.
These three letters used as reference a
common set of functional logic diagrams which has been found to be in error.
In the three letters we made basically similar statements concerning the initiation of a
Containment Ventilation Isolation (CVI) signal to trip closed all 14 containment purge supply and exhaust isolation valves.
The. functional logic diagrams used showed R-2 as one of the many inputs to generate a CVI sfgnali The CVI output is.wired into each 'f the control circuits of the 14 purge isolation valves Sii2140013 8ii207 pot PDR ADOCK 05000315 P
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including the Instrument Room.
However, the output signal from R-2 is wired directly into each of the control circuits of 10 purge isolation valves and excludes the Instrument Room valves.
Please note that the Instrument
- Room, while located physically within the containment, is separate from the upper and lower containment.
It was judged originally that a
potential high radiation condition should not immediately impact required work that would be in progress in the Instrument Room by stopping its purge system.
On this basis, the tripping function of R-2 was designed to allow Instrument Room purging independent of that in the upper and lower containment.
If the air particulate or radiogas channels (R-ll or R-12) initiated a
- signal, the Instrument Room purge system would immediately shut down and its purge isolation valves would close.'ence, protection from a high containment radiation condition was always afforded.
Our review of the safety significance of R-2 not tripping closed the four Instrument Room purge isolation valves shows that only one of the many levels of defense designed into CVI is slightly degraded from what we had previously stated.
The CVI signal from the Reactor Protection System is automatically initiated from a variety of inputs which cause Safety Injection to occur (such as low pressurizer
- pressure, high differential pressure between steamlines, lower containment pressure high, etc) thus still maintaining a,diversity of containment purge isolation signals.
The radiation monitor inputs R-2, R-ll and R-12 are provided in the design as an additional means of enhancing the overall defense-in-depth philosophy already provided by other multiple inputs.
As mentioned
- before, 10 of the 14 purge isolation valves receive a trip-close signal from R-2 when the key lock control switch is in the refueling mode.
During the period when the three above-mentioned submittals were
- prepared, the functional logic diagrams were easily accessible and they were used to provide the requested quick turnaround in responding to the NRC concerns.
- However, the functional logic diagrams are not design documents and are generally not kept up-to-date nor do they undergo the reviews used for electrical design documents.
Although the three above-mentioned letters were submitted with, an improper reference used to generate parts of them, the design of CVI in the Cook Plant which incorporates inputs from diverse plant parameters including R-ll and R-12 at no time presented a situation that would endanger the health and safety of the public.
We are processing a Licensee Event Report on this matter for submittal in 30 days to NRC Region III in accordance with our Technical Specifications.
We are taking the necessary steps to have R-2 initiate CVI in our RMS design.
Until such a design change is implemented we will maintain the purge isolation valves closed in the Instrument Room in operating modes 1, 2, 3 and 4.
This restriction applies to both Units 1 and 2 except during normal surveillance testing of the valves.
Upon implementation of the above mentioned design change the restriction will no longer be applied.
P
This document has been prepared following Corporate Procedures which incorporate a reasonable set of controls to ensure its accuracy and completeness prior to signature by the undersigned.
e y truly yo rs, unter Vice President cc:
John E. Dolan Columbus R.
W. Jurgensen D.'V; Sheller Bridgman R.
C. Callen G. Charnoff Joe Williams, Jr.
James G. Keppler Director of U.S.
NRC Region III NRC Resident Inspector at Cook Plant - Bridgman
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