ML20196H226
| ML20196H226 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 12/02/1998 |
| From: | Cruse C BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, TAC-M93444, TAC-M93445, NUDOCS 9812090018 | |
| Download: ML20196H226 (2) | |
Text
n CHAM.F.s H. CRUSE Baltimore Gas and Electric Company Vice President Calven Cliffs Nuclear Power Plant Nuclear Energy 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 410 495-4455 December 2,1998 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Change of Valves in Scope of Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety-Related, Pcwer-Operated Gate Valves" (TAC Nos.
M93444 & M93445)
REFERENCES:
(a)
Letter from Mr. D. M. Crutchfield (NRC) to Mr. R. E. Denton (BGE),
dated August 17,1995, "NRC Generic Letter 95-07: Pressure Locking and Thermal Binding of Safety-Related, Power-Operated Gate Valves" (b)
Letter from Mr. C. H. Cruse (BGE) to NRC Document Control Desk, dated February 13,1996, "180-Day Response to NRC Generic Letter 95-07: Pressure Locking and Thermal Binding of Safety-Related, Power-Operated Gate Valves" On August 17,1995, the Nuclear Regulatory Commission issued Reference (a) to request that licensees take actions to ensure that safety-related, power-operated gate valves susceptible to pressure locking or thermal binding are capable of performing their safety functions. As a result of our continued review, and evaluation following conversations with your staff during the closeout inspection for Generic l
Letter 89-10, we are removing the Containment Hydrogen Purge Valves (IMOV6900, IMOV6901, 2MOV6900, and 2MOV6901) from the scope of our Generic Letter 95-07 Program.
kb in Reference (b), our initial response to Generic Letter 95-07, we noted the following for these valves:
[They]... are part of the Containment Purge System that is designed to maintain hydrogen concentration inside containment below 4% (volume). During power operation, these valves are used to maintain containment pressure and activity levels within Technical Specification limits.
These valves are normally closed and on receipt of a Safety injection Actuation Signal [SIAS),
Containment Radiation Signal, or high radiation signal, will automatically close. The isolation signals can be over-ridden after an accident if both hydrogen recombiners failed (Updated Final h'
9812090018 981202 PDR ADOCK 05000317 P
pyg
a Docum:nt Control Desk Dectmber 2,1998 Page 2 Safety Analysis Report Chapter 14.21). These valves could have a maximum containment pressure of 72 psig trapped in the bonnet. Calculations [using the Grand Gulf Methodology] were completed to ensure the actuator is capable of opening the valve with pressure locked in the j
bonnet. These valves are not susceptible to thermal binding because they are closed under 1
ambient conditions and would not be required to open for several days after an accident when temperatures will be about the same. The safety-related function of these valves is to close to maintain containment integrity, but an analysis is discussed in Updated Final Safety Analysis Report Chapter 14 to vent containment following an accident where both safety-related recombiners fail...
As a result of our change in scope, Baltimore Gas and Electric Company Calculation CA04496 will be revised to remove the subject motor-operated valves from the calculation. This calculation, which is available for your review, uses the Commonwealth Edison Methodology to calculate the amount of thrust
)
required to open the valves under worst-case pressure locking scenarios. The justification for changing the scope is as follows:
Per our Operating instruction OI-41B, "llydrogen System Purge Operation," the hydrogen purge valves are not opened prior to two days after an accident has occurred. Based upon industry testing and experience, we anticipate that the gas trapped in the bonnet will dissipate to reduce bonnet pressure prior to opening the valves.
In addition, we have high confidence that the hydrogen purge valves have enough developed thrust to overcome pressure locking. In addition, our calculations show that the Unit I containment hydrogen purge valve actuators (IMOV6900 and IMOV6901) have sufficient capability to overcome anticipated pressure locking forces. Following testing scheduled for the 1999 Unit 2 Refueling Outage, the same will be true of the Unit 2 containment hydrogen purge valve actuators (2MOV6900 and 2MOV6901).
Should you have additional questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, l
V t
l CHC/JMO/bjd cc:
R. S. Fleishman, Esquire H. J. Miller, NRC L
J. E. Silberg, Esquire Resident inspector, NRC S. S. Bajwa, NRC R.1. McLean, DNR A. W. Dromerick, NRC J. II. Walter, PSC