ML20011A028
| ML20011A028 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 09/30/1981 |
| From: | Carroll J JERSEY CENTRAL POWER & LIGHT CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-05.B, TASK-3-5.B, TASK-RR NUDOCS 8110060374 | |
| Download: ML20011A028 (4) | |
Text
I Jersey Central Power & Ught Company Madison Avenue at Punchbowl Road L
Mornstown New Jersey 07960 201 539-6111 Septenber 30, 1981
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17REN.kd),
y Mr. Dennis M. Crutchfield, Chief
!w Operating Reactors Branch #5 J-! 00I G D3W -9
- z Division of Licensinf, M
6 U. S. Nuclear Regulatory Commission u.s. r""#
-t Washington, D. C.
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Gentlemen:
Subject:
Oyster Creek Nuclear Geneiating Station, Docket No. 50-219, SEP Topic III-5.B, Pipe Break Outside Containment U. S. NRC letter, dated April 16, 1981, to Jersey Central Poder G Light Company requested additional information regarding the proposed installation of a leak detection system on emergency condenser piping on the 75-foot elevation at Oyster Creek. This proposed plant modification is described in JCPSL letter, dated October 6,1980, to the U. S. NRC. to this letter provides the information which was requested.
Sincerely,
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. T. Carroll, Jr.
Acting Director Oyster Creek 1r Enclosure l
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8110060374 810930 PDR ADOCK 05000219 i
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Jersey Central Power & Light Companj is a Membar of the General Pubhc Utikties System
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RESPONSE TO NRC REQUEST FOR INFORMATION HIGH ENERGY LINE BREAK OUTSIDE CONTAINMENT SEP TOPIC lil-5.8 Responses to NRC request for additional information in NRC letter (D. M.
Crutchfield) to JCP&L (l. R. Finfrock, Jr.), dated April 16, 1981, are given below. The request for information is repeated below with each response.
1.
Request for information P rov i de justification for not proposing barriers, separation, and/or installation of an isolation valve inside containment on the steam supp ly lines as methods for mitigating the effects of high energy line breaks for this pip hg.
Respong As epor+ed in JCP&L letter, dated February, 1980, and in a meeting with the NRC on March 25, 1981, engineering design studies (and some component procurement) have been undertaken to determine practical and ef f ective methods to provide protection against the adverse consequences of a postulated break in the emergency condenser piping on the 75-foot level of the reactor building outside primary containment.
These studies included evaluation of the feasibility and effectiveness of (1) adding pipe whip restraints and jet impingement barriers to protect the isolation valves outside containment and (2) instal I ing a third isolation valve in the steam Iine of the emergency condenser piping just inside the containment. The results of these evaluai'ons showed that neither of these modif ications cou ld reasonably be accomplished on a retrofit basis in a manner which would ef fectively resolve all of the potential areas of concern and also not impose other significant limitations on access for in-service inspection and maintena' 3.
The main results of the evaluations which lead to this conclusien are sumarized below:
A.
Evaiuation of installing isolation Valves inside Containment This alternative method of providing isolation capability in the event the damage to the valves and piping outside containment is not practical or desirable for the following reasons:
1.
Insufficient space existt inside containment to install these motor-operated va l ves w i thout signi f icant modi f ication to existing piping and structures inside containment. The reason for this is the limited annular space between the drywell and reactor vessel at the 75-foot elevation.
2.
The location of the valves, high in the containment in the small annular space between the vessel and the drywell, would make disassembly and maintenance of the valves extremely dif ficult and hazardous.
3.
Installation of additional isolation valves inside containment would
p not provide a complete solution to the consequences of damage to the ist ation valves outside containment in that l' would not meet the single-active-f allure criterion of NUREG/CR/75/C87.
B.
Installation of Pipe hhip Restraints and Barriers Outs!de Containment The f easibility of adding pipe whip restraints and barriers to protect the emergency condenser isolation valves outside containment from the consequences of postulated breaks iri the numerous runs of emergency condenser steam and return piping on the 75-foot elevation was evaluated by determining applicable pipe whip and jet impingement design loads, performing ensite inspections to determine access conditions and availability of supports fer a restraint system, and preparing preliminary design studies.
T he conc l u s i or.: of this work are as follows:
1.
Because of the magnitude vf the design loads (approximately 250 kips in any direction) due to pipe whip or jet impingement. single restraint / barrier structure would be massive, involving use of structural frame assemblies made up of about 16"-deep beams. Further, since all of the emergency condenser steam and return Iines penetrate the containment in the same general area, restraining all of the lines at the isolation valves would probab y require a restraint structure which is of the order of 8'x15' in overali size.
The practical problems and interf aces which would be encountered in installing and support!ng such a structure in the existing space are judged to be significant.
2.
An ef fective restraint system is required to not only react direct pipe whip and jet impingement loads, but al so to carry any bending or torsional moments resu lti ng from pipe breaks remote f rora the isolation valves.
This requirement wou ld necessitate the installation of multiply restraint systems, each of which is similar to that described above, on the 75-foot level.
The f easibili ty of accomplishing this in the space available and using the adjacent floor as the supporting structure for all restraints has not been determined but would be extremely difficult, if possible.
3.
The containment shel l and emergency condenser piping penotrations are calculated to grow due to thermal expansion by up to about 1-3/4" relative to the adjacent reactor bailding floor at the 75-foot level. This wouId normalIy be accomodated by pr oviding gaps of up to 1-3/4" between the piping and the restraints to preverit over-stressing of the piping in the event of a pressurization event in the drywell.
In this case, however, because of the stif f ness of the piping and the relatively short lengths involved, such gaps wou ld preven
- the restraints f rom limiting the loads and moments imposed on the isolation valve-to piping welds to acceptable values.
This problem would require the design and development of very large snubbers with capacities in the 250 kip range, each, and it is not considered likely that if this were done, the required number of snubbers could be arecmodated with their supporting structures in the space available.
4.
Finally, the installation of a restraint system, such as described above, would impose severe limitations on access to the valves, their operators, the emergency condenser piping and fittings, and connecting welds and would thus limit in-service inspections and maintenance of these components.
For the above reasons, JCP&L has ruled out as undesirable and impractical
s.
the installation of pipe whip restraints and barriers to protect the e 9rgency condenser isolation valves and piping f ran the ef fects of postulated pip breaks in th i s area.
As a result of the evaluations summar i zed above, JCP&L has proposed the installation of a local leakage monitoring system to detect any leakage due to small cracks in these lines bef ore a signi ficant pipe break can occur.
2.
Request for Information Provide a schedule for submitting analyses to demons' rate that if this piping does fail, " leak before break" would be the expected f _. lure mode.
Response
Analyses to demonstrate that the emergency condenser piping on the 75-foot level will leak before a significant break could occur will be performed and the results transmitted to the NRC by December, 1981.
3.
Request for information The NRC staff position is that an augmented inservice inspection program must be instituted for those lines that rely on a leakage detection system to detect through wall leakage.
Prov i de a schedule f or submitting a proposed inservice inspection program.
Re_soonse In addition to the installation of a local leakage monitoring system as described in JCP&L submittal, dated October 6,1980, JCP&L proposes to augment the required in-service inspection of piping welds in tae emergency condenser system on the 75-foot level as foilows:
Visual examinations for evidence of leafage will be made with the system pressurized prior to or during each refnaling shutdown.
l The frequency of in-service in.
.ans presently required by the Oyster Creek Technical Speci f ications wil l be doub l ed; that is, the welds in the system on the 75-foot level will be inspected on a schedule which will cover alI of the weIds in each 5-year period.
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