ML20052C248
| ML20052C248 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 04/28/1982 |
| From: | Garrity J Maine Yankee |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM JHG-82-76, MN-82-86, NUDOCS 8205040532 | |
| Download: ML20052C248 (5) | |
Text
EDISON DRIVE MAIRE *QUARHEE Alom/CPol'KRCOMPARU*
avaugra, ua,ne oagas g)M3 (207) 623-3521 O
April 28,1982 MN-82-86 JHG-82-76 s
United States Nuclear Regulatory Commission
, f-\\
Washington, D. C. 20555 g@
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Attention: Office of Nuclear Reactor Regulation ch Division of Licensing Q
G 4" Q g A[S Operating Reactors Branch #3 v v l
Mr. Robert A. Clark, Chief 41 p \\
Reference:
(a) License No. OPR-36 (Docket No. 50-309)
(b) USNRC letter to MYAPCo dated February 23, 1982 (c) MYAPCo letter to USNRC dated January 15, 1982, MN-82-04 (d) MYAPCo letter to USNRC dated July 20, 1981, FMY-81-107
Subject:
TMI-II.B.1 RCS Vent System, Additional Information l
Dear Sir:
1 Reference (b) requested the subject additional information to supplement our i
submittal, Refemnce (d).
This letter provides a partial response to this request.
Maine Yankee is in the process of preparing an operating guideline for the mactor coolant system vent system.
This guideline, which will be submitted to the NRC by July 1,1982, will provide the basis for procedures addressing mactor coolant system vent system operation.
As indicated in Reference (b),
the plant procedures need not necessarily be reviewed prior to design app roval.
Therefore, instead of submitting the procedures for review as committed to in Reference (c), we will have the procedure available on site prior to declaring the RCS Vent System operational.
We trust this information is satisfactory; however, should you have further questions, please contact us.
Sincerely yours, MAINE YANKEE ATOMIC POWER COMPANY W&
Of John H. Garrity, Senior Director Nuclear Engineering & Licensing JHG:at 8205040532 820428 PDR ADOCK 05000309 P
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MAINE YANKEE ATOMIC POWER COMPANY ENCLOSURE TO MN-82-86 Response Request for Additional Information Pertaining to Item II.B.1, "RCS High Point Vents"
~
1.
. Submit operating guidelines for reactor operator use of the Reactor Coolant _ System - Vent System (RCSVS).
Resoonse See the cover letter.
2.
Verify that the orifices in the pressurizer vent line and the line.that the reactor vent ties into are smaller than the size corresponding to the definition of a loss-of-coolant accident (10 CFR Part.50, Appendix A) by providing a calculation of the maximum rate of loss of reactor coolant from the largest breaks that can be postulated in the pressurizer or reactor vent lines [ reference NUREG-0737 Item II.B.1 Clarification A.(4)].
Response
A break in the piping downstream of the orifice in the pressurizer vent line_ would result in a leakage rate of approximately 50 gpm.
A break in the piping in the reactor vent line-downstream of the orificed section would result in a leakage rate of approximately 40 gpm. These leak rates are well within that which corresponds to the definition of a loss-of-coolant accident. Detailed calculations are available for NRC review in the design package maintained at the plant.
3.
The following items apply to the portions of the RCSVS that form a part of the reactor coolant pressure boundary, up to and including the second normally closed valve [ reference NUREG-0737 Item II.B.1
~ Clarification A.(7)]:
a.
Verify that the piping, valves, components, and supports are classified Seismic Category 1.
Response
The portions of the RCSVS that form a part of the reactor coolant.
pressure boundary,' up to and including the second normally closed valve are Seismic Category 1.
Detailed design calculations are available for NRC review at Yankee Nuclear Services Division.
b.
Provide the design temperature and pressure of the piping, valves, and components.
Resoonse The design temperature and pressure of the piping, valves, and components are the same as the ' piping systems that the vent lines tie into; 2485 psig and 6500F.
MAINE YANKEE ATOMIC POWER COMPANY Page Two Enclosure to MN-82-86 c.
Describe the instrumentation that has been provided to detect and measure RCSVS isolation valve seat leakage (reference Appendix A to 10 CFR Part 50, General Design Criterion 30).
Resoonse Valve position indication is available for all four valves, with two valves in each vent path.
Also, both vent paths tie into lines which discharge into the pressurizer quench tank.
The quench tank has temperature, level, and pressure indication and alarms in the main control room.
These indications can be used to detect and measure isolation valve seat leakage.
d.
Describe the materials of construction and verify that they are compatible with the reactor coolant chemistry and will be fabricated and tested in accordance with SRP Section 5.2.3, " Reactor Coolant Pressure Boundary Materials."
Resoonse The materials of construction are in.accordance with the applicable piping classes-of the Maine Yankee Piping Specification.
Fabrication and testing were done.in accordance with established plant procedures. Details are available at the plant for NRC review.
e.
Demonstrate that internal missiles and the dynamic effects associated with the postulated rupture of piping will not prevent the essential operation of the RCSVS (i.e., at least one vent path remains functional)(reference Appendix A to 10 CFR Part 50, General Design Criterion 4).
Resoonse The pressurizer vent valves and piping are located within the pressurizer cubicle.
The reactor vent valves and piping are located on the chargirg floor outside of the cubicle.
They are separated by a concrete wall approximately 18" thick. A cross connect line between the two vent ' paths is supported directly off of the wall.
The ~only area which could be subject to internal missiles is inside the pressurizer cubicle.
This would disable only one vent path, leaving the other vent path functional.
MAINE YANKEC ATOMIC POWER COMPANY Page Three Enclosure to MN-82-86 4.
Verify that the following RCSVS failures have been analyzed and found not to prevent the essential operation of safety-related systems required for safe reactor shutdown or mitigation of the consequences of a design basis.
accident:
- Seismic failure of RCSVS components that are not designed to a.
withstand the safe shutdown earthquake.
Response
The only portion of the RCSVS which is not Seismic Category 1 is the 1" discharge piping downstream of the second isolation valve.
The failure of this piping will not prevent the essential operation of safety-related systems.
b.
Postulated missiles generated by failure of RCSVS components.
Resoonse The only potential missile sources are the motor-operated valves, and they are not located near any safety-related equipment.
t Dynamic effects associated with the postulated rupture of RCSVS c.
piping greater than one-inch nominal size.
Response
The RCSVS piping is all less than or equal to 1".
d.
Fluid sprays from RCSVS component failures. Sprays from normally uroressurized portions of the RCSVS that are Seismic Category-1 and Safety Class 1, 2, or 3 and have instrumentation for detection of leakage from upstream isolation valves need not be considered.
Response
Fluid sprays from RCSVS component failures will not prevent the essential operation of safety-related equipment since none of this equipment is in the areas that would be affected by fluid sprays.
MAINE YANKEE ATOMIC POWER COMPANY Page Four Enclosure to MN-82-86 5.
Verify that the RCSVS valves fall closed upon loss of power, or provide a reliability analysis consistirg of a failure mode and effects analysis
-(R4EA) or equivalent qualitative analysis that shows that no single active component failure could result in failure to close after intentional opening of an RCSVS path.
In particular, if the vent valves do not fait closed and if the cross-connect piping between the pressurf m ind reactor vessel head sent paths is being used, a power failure would prevent the isolation of the vent path [NUREG-0737 Item II.B.1 Clarification A.(6)].
Resoonse The RCSVS valves are' motor-operated and, therefore, fail as is on a loss of power. Each vent path contains two valves in series, powered from different emergency power supplies.
After intentionally opening an RCSVS vent path, a loss of c.e power supply or an active failure of one valve will not prevent the vent path from being isolated by the remaining valve.
If the cross-connect piping is used as a vent path, two valves powered from the same emergercy power supply would be utilized.
This path would be subject to a single active failure, i.e., the loss of the one power
.Jpply, which would prevent the isolation of this vent path.
- However, this vent path would be utilized only if a single active failure has already disabled the normal vent paths. Before using the cross-connect vent path, the potential consequences of a single failure preventing isolation of this vent path would have to be weighed against the consequences of not venting.
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