ML20141F876
| ML20141F876 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/21/1986 |
| From: | Tiernan J BALTIMORE GAS & ELECTRIC CO. |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM NUDOCS 8604230211 | |
| Download: ML20141F876 (11) | |
Text
.
B ALTIMORE GAS AND ELECTRIC CHARLES CENTER P. O. BOX 1475 BALTIMORE, MARYLAND 21203 JosEPN A.TIERNAN Wct PRESIDENT NUCLEAR ENERGY April 21,1986 U. S. Nuclear Regulatory Commit,sion Office of Nuclear Reactor Regulation Washington, D. C. 20555 ATTENTION:
Mr. Ashok C. Thadani, Director PWR Project Directorate #8 Division of PWR Licensing-B
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 oc 50-318 Reactor Coolant System Vents SupplementalInformation
REFERENCES:
(a)
NRC letter from Mr. A. C. Thadani, to Mr. J. A. Tiernan, dated January 16,1986 (b)
BG&E letter from Mr. A. E. Lundvall, Jr., to Mr. J. R. Miller (NRC), dated December 22,1983 Gentlemen:
- As requested in reference (a), a meeting between representatives of Baltimore Gas and Electric Company and the NRC was held on March 10, 1986, to discuss the Technical Specifications for the Reactor Coolant System (RCS) high point vents. At that meeting, the NRC requested supplemental information to reference (b). This letter transmits the requested supplemental information and does not affect the Determination of Significant Haz trds Considerations as stated in reference (b). provides a technical comparison between our Power Operated Relief Valves (PORVs) and the design criteria for high point vents as stated in NUREG-0737, item II.B.I.
We feel the PORV design conforms substantially to the criteria, and that credit for the use of the PORVs as a backup to the pressurizer vapor space high point vent should be given.
. provides proposed Technical Specifications for the RCS high point vents.
There are two minor differences between these proposed Technical Specifications and those proposed by NRC at the March 10, 1986 meeting. Attachment 3 provides a discussion of and justification for the minor differences.
i m"
8604230211 860421 i
PDR ADDCK 05000317 p
Mr. Ashok C. Thadani April 21,1986 Page 2 in addition, the NRC requested information regarding the power supplies for the solenoid operated valves in the RCS high point vent paths. The solenoid valves are powered from the following 125 volt DC buses:
1- & 2-SV 103 - 125 volt DC Bus 11 Reactor Vessel Vent Path:
1- & 2-SV 104 - 125 volt DC Bus 11 Pressurizer Vent Path:
1- & 2-SV 105 - 125 volt DC Bus 21 1- & 2-SV 106 - 125 volt DC Bus 21 Should you have any questions regarding this matter, please do not hesitate to contact us.
Very truly yours, NW JAT/MTF/ WPM / dim Attachments cc:
D. A. Brune, Esquire
- 3. E. Silberg, Esquire D. H. Jaf fe, NRC T. Foley, NRC T. Magette, DNR
7_.
ATTACHMENT 1 The following is a comparison of the Calvert Cliffs Units 1 & 2 Power Operated Relief Valve (PORV) design with the general design criterion provided in NUREG-0737, item II.B.1, Clarification.
CRITERIA (1)
The important safety function enhanced by this venting capability is core cooling.
For events beyond the present plant design basis, this venting capability will substantially increase the plant's ability to deal with large quantities of noncondensible gas whic could interfere with core cooling.
(2)
Procedures addressing the use of the RC$ hig* point vents should define the conditions under which the vents should be used as well as the conditions under which the vents should not be used. The procedures should be directed toward achieving a substantial increase in the plant being able to maintain core cooling without loss of containment integrity for events beyond the design basis. The use of vents for accidents within the normal design basis must not result in a violation of the requirements of 10 CFR 30.44 or 10 CFR 30.46.
RESPONSE
Procedures addressing the use of the PORVs as a pressurizer vent will be implemented following issuance of the proposed license amendment.
CRITERIA (3)
The size of the RCS high point vents is not a critical issue. The desired venting capability can be achieved with vents in a fairly broad spectrum of sizes. The criteria for sizing a vent can be developed in several ways. One approach, which may be considered, is to specify a volume of noncondensible gas to be vented and in a specific venting time.
For containments particularly vulnerable to failure from large hydrogen releases over a short period of time, the necessity and desirability for contained venting outside the containment must be considered (e.g., into a decay gas collection and storage system).
RESPONSE
The pressurizer vent line consists of 3/4-inch tubing reduced down to 1/2-inch tubing which tees into the 1/2-inch tubing of the reactor vessel vent line and then connects to a 10-inch inlet pipe to the quench tank. For comparison, the PORVs
ATTACHMENT 1 are on 2-1/2-inch, schedule 160 piping. The PORV orifice is 1.353 square inches which corresponds to a 1.3-inch diameter hole. In addition, based on information provided in Reference (a), the minimum operating pressure for the PORVs is 75 psig.
CRITERIA (4)
Where practical, the RCS high point vents should be kept smaller than the size corresponding to the definition of Loss of Coolant Accident (LOCA)
This will minimize the challenges to the emergency core cooling system (ECCS) since the inadvertent opening of a vent smaller than the LOCA definition would not require ECCS actuation, although it may result in leakage beyond Technical Specification limits. On PWRs, the use of new or existing lines whose smallest orifice is larger than the LOCA definition will require a valve in series with a vent valve that can be closed from the control room to terminate the LOCA that would result if an open vent valve could not be reclosed.
RESPONSE
A motor-operated isolation valve is provided upstream of each of the PORVs to permit control room operators to isolate the PORV in the event of a failure.
CRITERIA (5)
A positive indication of valve position should be provided in the control room.
RESPONSE
Acoustic monitors are installed on the PORV discharge piping to provide indication of valve position in the control room. These monitors use an accelerometer to directly measure pipe vibration which is indicative of flow past the PORV. This combined with other indicators located on the same panel in the control room, such as power to PORV solenoid valves, quench tank pressure, and quench tank level will provide positive indication of valve position.
CRITERIA (6)
The RCS high point vent system shall be operable from the control room.
RESPONSE
The PORVs can be operated from the control room by pulling out at least two high pressure trip modules in the reactor protective system cabinet.
ATTACHMENT 1 CRITERIA j
- (7)
Since the RCS high point vent system will be part of the reactor coolant system pressure boundary, all requirements for the reactor pressure i
boundary must be met, and, in addition, sufficient redundancy should be incorporated into the design to minimize the probability of an inadvertent actuation of the system. Administrative procedures may be a viable option to meet the single-failure criterion.
For vents larger than the LOCA definition, an analysis is required to demonstrate compliance with 10 CFR 50.46.
RESPONSE
l l
The PORVs and the block valves are ASME Section 111, Class 1.
Piping is ANSI B31.7, Class I upstream of the PORV and ANSI B31.7, Class 11 downstream. Two existing analyses (FSAR 14.8, RCS Depressurization, and FSAR 14.17, Loss of Coolant Accident) consider the case of both PORVs opening without block valve isolation. Additionally, PORY failure reduction was addressed by TMIItem II.K.3.2 and, by Reference (b), the NRC Staff found our existing system to be acceptable.
CRITERIA (8)
The probability of a vent path failing to close, once opened, should be minimized; this is a new requirement.
Each vent must have its power supplied from an emergency bus. A single failure within the power and control aspects of the RCS high point vent system should not prevent isolation of the entire vent system when required. On BWRs, block valves are not required in lines with safety valves that are used for venting.
I
RESPONSE
1 1
Emergency power is supplied to the PORVs and to the block valves. The emergency power supplied to each PORY is independent from the emergency power supplied to its corresponding block valve.
l CRITERIA j
(9)
Vent paths from the primary system to within containment should go to those areas that provide good mixirg with containment air.
RESPONSE
Like the existing RCS high point vent system, the PORV discharges to the quench tank located inside the containment.
i m.
m
. m.
m.m.
m..
..m m.-
- m.
m.
m m
.-.m.
ATTACHMENT 1 CRITERIA (10)
The RCS high point vent system (i.e., vent valves, block valves, position indication devices, cable terminations, and piping) shall be seismically and environmentally qualified in accordance with IEEE 344-1975 as supplemented by Regulatory Guide 1.100, 1.92 and SEP 3.92,3.43, and 3.10. Environmental qualifications are in accordance with the May 23, 1980, Commission Order and Memorandum (CL1-80-21).
RESPONSE
The PORVs, block valves, and associated piping and controls are classified Seismic Class I, as is the existing RCS high point vent system. Though not part of the Environmental Qualification Program, the PORVs and block valves were designed, procured, and installed to meet the expected operating conditions.
Additional information concerning the operability of the PORVs and the block valves is provided in reference (a).
CRITERIA (11)
Provisions to test for operability of the RCS high point vent system should be a part of the design. Testing should be performed in accordance with subsection IWV of Section XI of the ASME Code for Category B valves.
RESPONSE
The block valves are tested in accordance with subsection IWV of Section XI of the ASME Code for Category B valves.
CRITERIA (12)
It is important that the displays and controls added to the control room as a result of this requirement not increase the potential for operator error. A human-factor analysis should be performed taking into consideration:
(a) the use of this information by an operator during both normal and abnormal plant conditions; (b) integration into emergency procedures; (c) integration into operator training; and (d) other alarms during emergency and need for prioritization of alarms, a
m_,,___._
~ _. -.
ATTACHMENT 1 I
i
RESPONSE
i f
All displays and controls associated with the PORVs already exist. The human j
factors aspects are being considered by our response to NUREG-0737, item 1.D.1, l
Detailed Control Room Design Review.
1 i
i References l
'(a)
Letter from Mr. A. E. Lundvall, Jr., to Mr. E. J. Butcher, Jr., TMl Action Item li.D.1, dated October 23,1985 (b)
Letter frosu Mr. J. R. Miller, to Mr. A. E. Lundvall, Jr., NUREG-0737 Items ll.K.3.1-Automatic PORY lsolation and li.K.3.2 - Report on PORVs for Calvert Cliffs Units 1 and 2, dated October 12, 1983 i
l t
9
ATTACHMENT 2 REACTOR COOLANT SYSTEM REACTOR COOLANT SYSTEM VENTS LIMITING CONDITION FOR OPERATION 3.4.13 One reactor coolant system vent path consisting of two solenoid valves in series shall be OPERABLE and closed at each of the following locations:
a.
Reactor vessel head b.
Pressurizer vapor space APPLICABILITY: MODES 1 and 2 Action:
a.
With the reactor vessel head vent path inoperable, maintain the inoperable vent path closed with power removed from the actuator of the solenoid valves in the inoperable vent path, and:
1.
If the pressurizer vapor space vent path is also inoperable, restore both inoperable vent paths to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY within six hours, or 2.
If the pressurizer vapor space vent path is OPERA 6LE, restore the inoperable reactor vessel head vent path to OPERABLE status within 30 days or be in at least HOT STANDBY within six hours, b.
With only the pressurizer vapor space vent path inoperable, maintain the inoperable vent path closed with power removed from the valve actuator of the solenoid valves in the inoperable vent path, and:
1.
Verify at least one PORV and its associated flow path is OPERABLE within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and restore the inoperable pressurizer vapor space vent path to OPERABLE status prior to entering MODE 2 following the next HOT 5HUTDOWN of sufficient duration, or 2.
Restore the inoperable pressurizer vapor space vent path to OPERABLE status with 30 days, or be in at least HOT STANDBY within six hours, c.
The provisions of Specification 3.0.4 are not applicable j
Calvert Cliffs Unit 1 & 2 3/4 4-32 Amendment No.
w t
ATTACHMENT 2 REACTOR COOLANT SYSTEM l
REACTOR COOLANT SYSTEM VENTS
[
LIMITING CONDITION FOR OPERATION SURVEILLANCE REQUIREMENTS - 4.4.13.1 Each reactor coolant system vent path shall be demonstrated OPERABLE by testing each valve in the vent path per Specification 4.0.5.
4.4.13.2 Each reactor coolant system vent path shall be demonstrated OPERABLE at least once per 18 months by:
a.
Verifying all manual isolation valves in each vent path are locked in the open position.
b.
Verifying flow through the reactor coolant system vent paths with the vent valves open.
l e
Calvert Cliffs Unit 1 & 2 3/4 4-33 Amendment No.
7 T
8 ATTAC19 TENT 2
^
BASES 3/4 4.13 Reactor Coolant System Vents i
i,
. Reactor Coolant System Vents are provided to exhaust noncondensible gases and/or steam from the primary system that could inhibit natural circulation core cooling.
The OPERABILITY of at least one reactor coolant system vent path from the (reactor vessel head) and the (pres-l surizer vapor space) ensures the capability exists to perform this function.
The valve redundancy of the reactor coolant system vent paths serves to minimize the probability of inadvertent or irreversible actuation while ensuring that a single failure of a vent valve, power supply or controp system does not prevent isolation of the vent path.
The function, capabilities, and testing requirements of the reactor coolant system vent systems are consistent with the requirements of item II.B.1 of NUREG-0737, " Clarification of TMI Action Plan Requirements," November 1980.
't 1
i i
1 s
i L
1 i
Calvert Cliffs Unit 1 & 2 B 3/4 4-13 Amendment No.
y.
ATTACHMENT 3 There are two minor differences between the RCS high point vents Technical Specifica-tions proposed by NRC at a meeting on March 10, 1936 and the Technical Specifications in Attachment 2 of this letter. The following is a discussion of the differences and justification for each.
1.
At the March 10, 1986 meeting, the NRC proposed that the Action Statements require COLD SHUTDOWN if OPERABILITY requirements could not be met.
BG&E proposes that the Actier/ Statements require shutdown to at least HOT STANDBY. This difference is justified since the high point vents are required OPERABLE in MODES I and 2, and it would be possible to repair the vents in HOT STANDBY.
2.
At the March 10, 1986 meeting, the NRC proposed that if a PORV were being used in place of an inoperable pressurizer vapor space vent, the inoperable ve nt would be returned to service prior to entering MODE 2 following the next H3T SHUTDOWN af ter 30 days.
BG&E proposes that the inoperable vent be returned to service prior to entering MODE 2 following the next FOT SHUTDOWN of suf ficient duration. This proposal would clarify the f act that the inoperable vent path should be repaired at the earliest opportunity. Also, it would not require extension of a shutdown for the sole purpose of repairing the pressurizer vapor space vent when a PORV is OPERABLE.
-