ML19264B561
| ML19264B561 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/26/1973 |
| From: | Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Vandenburgh D YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8011180357 | |
| Download: ML19264B561 (2) | |
Text
h j
OCT 28 B73 Docket No. 50-29 Yanime Atomic Electric Company ATTN: Donald E. Vandenburgh Vice President 20 Turnpika Road Westboro, Massachusetts 01581 Centlemen:
By lettar dated Septen.ber 21, 1973, you proposed certain modifications to the Yankee reactor protection system intended to increase the reliability of the scram permissive relay instrurentation in line with the criteria discussed in our latter of Septesiber 13, 1973. We have completed our review of your proposed modifications and find that they do not provide an acceptable degree of reliability for the scram bypass functions, consistent with the stated criteria.
The criteria outlined in our letter of September 13, 1973, require in part that bypassing of scram functions shall only be possible manually and that by-
- passed scram functions be reinstated automatically when the turbine nozzle pressure is greater than that equivalent to 15 se.
Your proposed instrumentatica chanEes do not provide for automatic removal of scram bypasses on incre.asing signal pressure.
Thus, if the signal pressure vera inadvertently lost to the permissiva relays while at power above 15 We, with the manual switch left in the scram bypass position, the associated scram functions would be bypassed. Contrary to the intent of the stated criteria, the scram bypass system depends on nhinistrative controls to insure that scram functions are operable when the reactor is at power.
Bacause of the importance of the scram functions to reactor safety, it is necessary that the Yankee scram bypass instrumentation be upgraded to conform with the critaria outlined in our letter of September 13, 1973.
In summary, to meet these critaria the modified instrumentation should provide that scram functions can only be bypassed mannally and then only when below 15 We.
Further, that upon reaching a praset va3ns of the turbine noz=le pressure (corresponding to 15 MWe) this increasing signal pressure should cause automatic reset to the non-bypans mode.
N 4
Yankee Atomic Electric Compan) OCT C A 1973 We request that you submit by November 26, 1973, a description of the necessary modifications to the scras bypass instru:w. station to maat the criteria of our latter of Sept 2mber 13, 1973, as summnrized above, including your schedule for implementing the changas.
Sincerely,
$ YoI S O e~ 5 f d
W 1A J. Skovholt Assistant Director for Operating Raactors Directorate of 1.icensing DISTRIBUTION:
Docket File RP Reading File Branch Peading File AEC PDR JRBuchanan, ORNL DJSkovholt R0 (3)
BJSchemel TJCarter IBurger SATeets GChipman
,,_L1 Ry__
[d
...L ORB #1,,
,,,,Q,0RB,,,#,1 L : 0RB,#,1,,,
0 orncr >
GChipmanh',M h
i e
%URNAME>
E ONS t $5$ ------
?- Y S. 5-.
DATT >
Imm AIC-318 (Rev. 9-53) AICM 0240
.ss-ie-sies H 44Ws