ML20006C554
| ML20006C554 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/02/1990 |
| From: | Hairston W GEORGIA POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9002080219 | |
| Download: ML20006C554 (3) | |
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- w. o. H.ir. ton, ni sena m rmaru February 2,1990 0210 t w.w onmanons
. Docket Nos.
50-424 50-425 U. S. Nuclear Regulatory Commission i
ATTN: Document Control Desk Washington, D. C.
20555 Gentlemen:
V0GTLE ELECTRIC GENERATING PLANT RESPONSE TO INSPECTION REPORT NOS. 50-424/89-33 AND 50-425/89-38 The subject inspection report, concerning the inspection conducted by Mr. J. F.
1 Rogge and Mr. R. F. Aiello during the period of October 28 - December 1, 1989, contains several comments regarding the autoniatic function of the pressurizer y
power operated relief valves (PORVs).
Since testing of this automatic function was the subject of a previous violation (Inspection Report Nos. 50-424/89-31 and 50-425/89-36 and our response dated 1-16-90, log number ELV-01235), Georgi.a Power Company believes that a response to these comments is appropriate.
The enclosure to this letter provides our position with respect to the statements made.in the. subject inspection report concerning the automatic function of the PORVs.-
Please contact this office if you have any questions.
Sincerely,
{
J4. W W. G. Hairston, III WGH,III/NJS/gm Enclosure c(w):
Georaia Power Company Mr. C. K. McCoy Mr. G. Bockhold, Jr.
Mr. P. D.-Rushton Mr. R. M. Odom NORMS U. S. Nuclear Reaulatory Commission Mr. S. D. Ebneter, Regional Administrator Mr. D. B. Matthews, Director, Project Directorate 11-3 Mr. R. F. Aiello, Senior Resident inspector, Vogtle 7
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ENCLOSURE GEORGIA POWER COMPANY RESPONSE TO COMMENTS MADE PERTAINING TO THE AUTOMATIC FUNCTION OF THE PORVS Page 6 of Inspection Report Nos. 50-424/89-33 and 50-425/89-38 contains several comments concerning the automatic function of the pressurizer PORVs.
The following clarification is provided with respect to these comments:
COMMENT 1:
"TS 3/4.4.4 bases states that the PORVs and steam bubble function to relieve RCS pressure during all design transients, up to and including the design step load decrease with steam dump."
CLARIFICATION FOR COMMENT 1:
It is incorrect to infer from the TS bases that the PORVs are necessary to maintain the plant within the envelope of the safety analysis. The PORVs do function to relieve RCS pressure and it is desirable that they function as designed.
However, Westinghouse standards for transient and accident analyses state that control systems are not assumed to operate unless their operation will cause the results of the transient or accident analysis to be more severe.
The PORVs perform a control function in the same manner as the pressurizer sprays and heaters.
COMMENT 2:
"Two cases, for.both the minimum and maximum reactivity feedback, are analyzed in the FSAR, Chapter 15, paragraph 15.2.3.2.1.
One case takes full credit for the effect of pressurizer spray and power-operated relief valves in reducing or limiting the coolant pressure with safety valves available."
CLARIFICATION FOR COMMENT 2:
Section 15.2.3 of the FSAR discusses the turbine trip transient. One case does indeed assume the operation of the PORVs. However, in keeping with the Westinghouse standards mentioned above, the PORVs are assumea to operate because their operation makes the DNB considerations for this transient more severe.
The second case analyzed takes no credit for the PORVs in order to maximize the pressurization of the primary for this event.
The FSAR states that the pressurizer safety valves and steam generator safety valves prevent overpressurization in primary and secondary systems. Therefore, when viewed in the proper context, the operation of the PORVs is clearly not required from the l
standpoint of the safety analysis.
l
l ENCLOSURE (CONTINVED)
COMMENT 3:
"The FSAR, Chapter 15, Table 15.2.3-1, indicates that with and without offsite power available for a feedwater system pipe break, pressurizer PORVs are expected to actuate in 19.5 seconds."
4 CLARIFICA110N FOR COMMENT 3:
This.particular entry in Table 15.2.3-1, cited above, refers to the feedwater system pipe break discussed in Section 15.2.8 of the FSAR.
In this case, the PORVs are assumed to operate because their operation causes the results of the j
accident to be more severe. Therefore, failure of the automatic function of the PORVs such that the valves did not open would result in this accident being less limiting.
COMMENT Aj.
"One of the major assumptions in the FSAR, Chapter 15, paragraph 15.2.8.2.1, used for a double ended rupture of the largest feedwater pipe at full power is that credit is taken for the pressurizer PORVs and the safety relief valves. No credit is takan for pressurizer spray."
CLARIFICATION FOR COMMENT 4:
See the clarification for Comment 3, above. The use of the words "taken credit for" is misleading and it is our intent to clarify the FSAR to prevent future misconceptions regarding the operation of the PORVs.
COMMENT 5:
"FSAR-Q, Question 420.19, states, "Using detailed schematics, describe the design of pressurizer power-operated relief valve control and the block valve control, and verify that no single failure will preclude the automatic actuation logic for all modes of operation."
CLARIFICATION FOR COMMENT 5:
(
While it is desirable that no single failure preclude automatic operation of the i
PORVs, the above discussion demonstrates that the PORVs are not assumed to operate for the purpose of accident mitigation in the safety analyses.
The fact that the PORVs are not susceptible to a single failure is not a basis for L
concluding that their automatic operation is necessary to maintain the plant i
within the envelope of the safety analysis.
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