ML19340E011
| ML19340E011 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/05/1980 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 8101060149 | |
| Download: ML19340E011 (8) | |
Text
_,...-
4 a
TEfA
[,f* ** %g,(8, UNITED STATES J '$ ;'.f( }
NUCLEAR REGULATORY COMMISSION "i,we WA5Hi.\\G TON. D. C. 20535
'%1h/l OEC 5 1C80 Docket No. 50-395 q
c t,b i '
ci Mr. T. C. Nichols, Jr.
d 2
Vice President & Group Executive
. '[
Nuclear Operations
- P T'
South Carolina Electric & Gas Company
$/
j lIjl[
P. O. Box 764
,Q d
"3 Columbia, South Carolina 29281
'a ri
~o a
Dear Mr. Nichols:
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION In our review of your response to TMI matters, we have determined that additional information is required to enable us to complete our review.
Enclosed is a request for additional information related to item II.B.l.
We request that you provide this additional information not later than December 19, 1980.
If you cannot meet this schedule or if you require clarification, please contact the staff's assigned project manager.
Sincerely, c
Robert L. Tedesco, Assistant Director i
for Licensing Division of Licensing
Enclosure:
Request for Additional Information cc: See next page i
i 1
G, o 2
1 S101060 L
1
_ _.... _..,... _ - _ -... ~ _......., _.. _ _. _. _. _.. _ _
i s
Mr. T. C. Nichols, Jr.
Vice President & Group Executive i
Nuclear Operations South Carolina Electric & Gas Company P. O. Box 756 Columbia, South Carolina 29281 cc: Mr. William A. Williams, Jr.
Vice President South Carolina Public Service Authority 223 North Live Oak Drive 1
Moncks Corner, South Carolina 29461 J. B. Knotts, Jr., Esq.
i Debevoise & Liberman l
1200 17th Street, N. W.
Washington, D. C.
20036 Mr. Mark B. Whitaker, Jr.
Group Manager - Nuclear Engineering and Licensing South Carolina Electric & Gas Company P. O. Box 764 Columbia, South Carolina 29218 Mr. Brett Allen Bursey Route 1, Box 93C Little Mountain, South Carolina 29076 t
Resident Inspector / Summer NPS c/o U.S. NRC Route 1, Box 64 l
Jenkinsville, South Carolina 29065 1
I I
l I
i l,
. -... -. _,. -. _ _.. _.,. _,, -. _... -............ _ - _........ _ _. _.. ~ _. - -. -. ~
EfiCLOSURE REQUEST FOR ADDITIO:iAL 'NFOR?!ATICt1 Q211.133 Reactor Coolant System Vents Your response to TMI-related requiremnt item II.B.1 is not sufficient.
Provide all necessary infomation for your proposed Reactor Coolant System Vents including a detail system description, results of analyses, P& ids, operating procedures and technical specifications as required in the attached clarification for this item.
l 3
I i
l l
~~-w-7..,2,.
~,
II. B.1 REACTOR CCOLANT SYSTEM VENTS
(~
Position Each apolicant and licensee shall install reactor coolant system (RCS) and reacter vessel head high point vents remotely operated from the control room.
Althotgh the purpose of the system is to vent noncondensible gases from the RCS which may inhibit core r.coling during natural circulation, the vents must not lead to an unacceptable increase in the probability of a loss-of-coolant accident (LOCA) or a challenge to containment integrity. Since these vents form a part of the reactor coolant pressure boundary, the design of the events shall conform to the requirements of Appendix A to 10 CFR Part 50, " General Cesign Criteria." The vent system shall be designed with sufficient redundancy that assures a Icw probability of inadvertent or irreversible actuation.
Each licensee shall provide the follcwing information conc rning the design and operation of the high point vent system:*
(1) Submit a description of the design, location, size, and power supoly for the vent system along with results of analyses for loss-of-coolant accidents initiated by a break in the vent pipe. The results of the analyses should demonstrate compliance with the acceptance criteria of 10 CFR 50.46.
(2) Submit procedures and supporting analysis for operator use of the vents that also include the information available to the operator for initiating or terminating vent usage.
Chances to Previous Recuirements and Guidance
~
(1) The probability of a valve failing to close, once opened, s_hould be min w1 zed.
(2) Establishes environ = ental qualification (Commissica Order, May 23, 1980).
(3) Establishes provisions for testing.
5 (4) Delete requirements of September 27, 1979 letter frem Vassallo to applicants stating that vents shall be safety grade and shall satisfy single-failure criteria of IEEE-279. Vent systems are not required to have redundant paths. A degree of redundancy should be provided by powering different vents from different emergency busas.
(5) Documentation date changed to July 1,1981 and implementation date to July 1, 1982.
Clarification does not change NRC concept of requirement, but provides more detail on scope. The dates have been revised to provide time for procurement and installation.
^It was the intent of the October 30, 1979 letter to delete the requirement to meet the criteria of 10 CFR 50.44 and SRP 6.2.5 for beyond-design-basis events. The analysis requirements of Position 2 in the September 13, 1979
{,
letter are therefore unnecessary.
l II.8.1-1 t
._.s.
-:-=--.._3.._.._.,__
w r,-
Clarification A.
General (1) The important safety function enhanced by this venting capability is core cooling. For events beyond the present design basis, this venting capability will suostantially increase the plant's ability to deal with large quantities of noncondensible gas which could interfere with core cooling.
(2) Procedures addressing the use of the reactor coolant system 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 snould 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 50.44 or 10 CFR 50.46.
(3) The size of the reactor coolant 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 hycrogen 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).
(4) Where practical, the reactor coolant system vents should be kept smaller than the size corresponding to the definition of LOCA (10 CFR 50, Appendix A).
This will minimize the challenges to the emergency core cooling system (ECCS) since the inadvertent opening of a vent smalier than the LOCA definition would not require ECC5 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 seriesAvalve that can be closed from the control room to terminate the LOCA tha ould result if an open vent i
valve could not be reclosed.
gg g y (5) A positive indication of valve position should be provided in the centrol room.
(6) The reactor coolant vent system shall be operable from the control room.
(7) Since the reactor coolant system vent will be part of the reactor coolant system pressure boundary, all requirements for the reactor pressure 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 o
II.B.1-2 N 6 44 N*66 w'we e
LOCA definition, an analysis is required to demonstrate compliance with k
(8) The probability of a vent path failing to close, once opencd, should be minimized; this is a new requirement. Each vent must have its power supplieu..;m an emergency bus. A single failure within the power and control aspects of the reactor coolant vent system should not prevent isolation of the entire vent system when recuired. On BWRs, block valves are not required in lines with safety valves that are used for venting.
(9) Vent paths from the primary system to within containment should go to those areas that provide good mixing with containment air.
(10) The reactor coolant vent system (i.e., vent valves, block valves, position indication devices, cacle terminations, and piping) shall be seismically and environmentally qualified in accordance with IEEE 344-1975 as supple-mented by Regulatory Guide 1.100, J.92 and SEP 3.92, 3.43, and 3.10.
Environmental qualific;tions are in accordance with the May 23, 1980 Commission Order and Memorandum (CLI-80-21).
(11) Provisions to test for operability of the reactor coolant 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.
(12) It is impcrtant 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 considera-tion:
'a) the use of this information by an operator during both normal and abnormal plant conditions, (b) integration into emergency procedures, (c) integration into opsrator training, and i
i (d) other alarms during emergency and need for prioritization of alarms.
i B.
BWR Design Considerations l
(1) Since the BWR owners' group has suggested that the present BWR designs have an inherent capability to vent, a question relating to the capability of existing systems arises. The ability of these systems to vent the RCS of noncondensible gas generated during an accident must be demonstrated.
Because of differences among the head vent systems for BWRs, each licensee or applicant ;5e;1d address the specific design features of this plant and compare them with the generic venting capability proposed by the BWR owners' group.
In addition, the ability of these systems to meet the same requirements as the PWR vent system must be documented.
(2) In addition to RCS venting, each BWR licensee should address the ability l
to vent other systems, such as the isolation condenser which may be II.B.1-3
, y-l
--u--.
~
required to maintain adequate core cooling.
If the production of a large
(
amount of noncondensible gas would cause the less of function of such a system, remote venting of that system is required. The qualifications of such a venting system should be the same as that required for PWR venting systems.
C.
PWR Vent Design Considerations (1) Each PWR licensee should provide the capability.to vent the reactor vessel nead. The reactor vessel nead vent should be capable of venting noncondensible gas from the reactor vessel hot legs (to the elevation of the top of the outlet nozzle) and cold legs (through head jets and other leakage paths).
(2) Additional venting capability is required for those portions of each het leg that cannot be vented through the reactor vessel head vent or pres-surizer.
It is impractical to vent each of the many thousands of tubes in a U-tube steam generator; however, the staff believes that a procedure can be developed that assures sufficient liquid or steam can enter the U-tube region so that decay heat can be effectively removed from the RCS.
Such operating procedures should incorporate this consideration.
(3) Venting of the pressurizer is required to assure its availability for system pressure und volume control. These are important considerations, especially during natural circulation.
Acolicability This requirement applies to all operating reactors and applicants for operating license.
Imolementation Installation should take place by July 1,1982. Until staff approval is obtained, installation may proceed; but operating procedures should not be implemented and valves should be placed in a condition so as to minimize the potential for inadvertent actuation (e.g., remove power).
Type of Review A preimplementation review will be performed prior to authorizing use of the vent.
l Documentation Required t
l By July 1, 1981, the licensee shall provide the following information on the reaci.or coolant vent system for staff review:
(1) The information requested in items 1 and 2 under " Position";
II.8.1-4 l
l nump ewm-N-e-.g---a yeh.
(2) A discussion of the design with respect to conformance to the design I
criteria discussed under " Clarification," including ceviations, if any, with adequate justification for such deviations; and, (3) Supporting information including logic diagrams, electrical schematics, I
piping and instrumentation diagrams, test procedures, and technical specifications.
\\
Technical Soecification Chances Recuired Changes to technical specifications will be required.
I References Letter from D. G. Eishenut, NRC, to all Operating Nuclear Power Plants,
Subject:
Follewup Actions Resulting from the NRC Staff Reviews Regarding the Three Mile Island Unit 2 Accident, dated September 13, 1979.
Letter from H. R. Denton, NRC, to all Operating Nuclear Power Plants,
Subject:
Discussions of Lessons Learned Short-Term Requirements, dated October 30, 1979.
U.S. Nuclear Regulatory Commission, "NRC Action Plan Developed as a Result of the TMI-2 Accident," USNRC Report NUREG-0660, Vols. 1 and 2, May 1980.
Commission Orders, May 23, 1980 (CLI-80-21).
h II.S.1-5 eng>=-
. - =....
__--MQ-
,m.
I e
~
r.