ML20198N951
| ML20198N951 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Oyster Creek |
| Issue date: | 04/25/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20151H203 | List:
|
| References | |
| FOIA-86-26 NUDOCS 8606060208 | |
| Download: ML20198N951 (18) | |
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OYSTER CREEK NUCLEAR GENERATING STATION MPA B-24 SAFETY EVALUATION REPORT By the Containment Systems Branch
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Background===
The staff reviewed the containment purge / vent system design a
and operating practices for Oyster Creek, and transmitted a request for additional information on this topic to the Licensee by letter dated January 4, 1982, from D.
Crutchfield, NRC, to I~. F i n f r o c k,
Jr.,
Jersey Central Power and Light Company.
The licensee responded to the staff's request for information by letters dated July 15, 1982, and January 13, 1983, from P.
Fiedler, General Public Utilities Nuclear, to D.
Crutchfield, NRC.
System Description
The purge / vent system at Oyster Creek utilizes containment isola-tion valves ranging in size from two inches to 20 inches in diameter.
Also, the licensee is replacing l the larger (greater than 2 inch diameter) isolation valves to acet staff operability requirements.
The staff's review is based on the information supplied by the licensee concerning these new valves.
Inerting/
deinerting of the containment (drywell and torus),is performed using the larger valves in the intet and exhaust penetrations in both the drywell and torus.
The two-inch valves are utilized for nitrogen makeup and for pressure control.
The purge / vent 6060gggg8860319 PATTERSO86-26 PDR l
. system is configured s,uch that the Lines penetrating containment have two isolation valves in series.
I Evaluation and Conclusions The purge system at 0yster Creek is not frequently used during plant operating conditions above cold shutdown (about 100-200 hours per year), and is only used when necessary for the safe operation of the plant.
The two-inch Lines are used for containment pressure control and for nitrogen make-up operations.
The staff has found that the rationale for purge / vent system operation at Oyster Creek, and the annual usage of the system, are acceptable for the fotLowing reasons:
1)
Operating experience at the oyster Creek facility j
has shown that purge system operation has not j
been extensive (100-200) hours per year).
2)
Inerting/deinerting of the containment and pressure control are necessary actions for the safe operation of the plant.
3)
The cost involved in replenishing the nitrogen is an incentive for the Licensee to restrict a
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purging and venting operations.
The staff recommended that Oyster Creek provide measures to ensure that isolation valve closure wiLL not be prevented by debris which could potentially become entrained in the escaping air and steam.
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. The information supplied by the licensee has demonstrated that the present design meets the staff recommendation.
The drywell purge intet and exhaust penet rat ions are located high on the drywelL walls and have radiation shields located 12 inches from their exits.
The reasons for the staff's finding that the potential f or debris reaching the dryweLL purge / vent containment isolation valves is negligibter are the use of fast closing isolation valves (five seconds) and the difficult paths debris must travel to reach the first isolation valve.
Debris would have to be carried up to the elevation of the penetrations travel around the radiation shields, and pass through over 20 feet of piping containing several'45 degree and 90 degree bends / before reaching the first isolation valve.
The Licensee contends that the wetwell purge / vent penetrations do not require debris screens because of their location.
The staff agrees with the Licensee's l
position since the wetwell is relatively free of debris.
Alsor because a LOCA woutd occur in the drywelle the suppression pool will act to entrain any debris in the air and steam flowing from the drywell to the wetwell.
The relatively small probability of deb rir reaching the wetwell purge / vent penetration combined with the use of fast closing isolation valves (five seconds) constitute the basis for the staff's finding that the present measures to j
prevent debris from entering the wetwell purge isolation valves I
are acceptable.
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The Licensee was requested to submit and analysis which demonstrates the acceptability of the provisions made to protect safety-related structures and equipment located beyond the purge / vent isolation valves against loss of I
function from the environment created by the escaping air i
and steam.
The only safety related equipment Located I
downstream of the purge isolation valves at Oyster Creek j
a re the standby gas treatment system (SGTS) trains.
To l
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pressure rise that would occur before the purge valves are
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1 the purge / vent exhaust system by installing blowout panets in the ducting just beyond the purge system outboard isolation valves.
These blowout panels witL be designed I
to prevent the design pressures of the SGTS and associated
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ductwork from being exceeded.
The staf f ag rees that this 1
l proposed modification wilL prevent any damage from occuring 1
to the SGTS and associated ductwork.
Therefore, it is the a
i staff's finding that the provisions to protect the safety-i related structures downstream of the purge / vent systen l
j isolation valves are acceptable.
The Licensee wilL be i
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required to provide formal documentation of the modifications i
described above and the schedule for completing the design c h ang e s.
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a-The licensee was requested to provide the amount of contai nment atmosphere that would be released through the purge / vent l
isolation valves before their closure in order for the staff to
- l evaluate the radiological consequences of a LOCA occurring while purging or venting.
The analyses provided by the l
Licensee considered only the two-inch purge / vent Lines being open at the time of a LOCA, and did not include the 18 and 20 inch purge / vent Lines.
Therefore, the staff conservatively calculated the amount of containment atmosphere that would be 1
released through att the purge / vent Lines that could be open 1
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at the time of a LOCA.
This value, 2000 pound mass of steam i
l and/or air, wilL be used in the staff's radiological analysis of the consequences of purging at the time of a LOCA.
As a result of the staff's study of valve Leakage due to seat det e ri o rat i on, periodic Leakage integrity tests of the purge /
vent iso Lation valves we re recommended for atL plants utilizing valves with resilient seats.
The new purge / vent j
system isolation valves currently being installed by the 3
I Licensee utilize a metal-to metal seating arrangement.
i T he re f o r e, staff recommendations related to testing of valves with resilient seats do not apply to Oyster Creek.
The i
Leak test f req uency specified in Appendix J to 10 CFR Part 50 is the only leak test frequency that would be applicable to the t
Oyster Creek purge / vent isolation va lv e s.
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Opernbility Qualification of Purge and Vent Valves Demonstration of operability of the containment purge and vent valves and the ability of these valves to close during a design basis accident is necessary to assure containment isolation. This demonsustion of operability is required by NUREG-0737, " Clarification of 11& Action l
I Plan Requirements," II.E.4.2 for containment purge and venf valves which are not sealed closed during operational conditions 1, 2, 3 and
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4.
1.
For each purge and vent valve covered in the scope of this review, l
the following documentation demonstrating compliance with the
" Guidelines for Demonstration of Operability of Purge and Vent Valves" (Attachment.2) is to be submitted for staff review:
A.
Dynamic Torque Coefficient Test Reports (Butterfly valves only) - including a description of the test setup.
B.
Operability Demonstration or In-situ Test Reports (when used)
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C.
Stress Reports D.
Seismic Reports for Valve Assembly j
(valve and operator) and associated parts.
E.
Sketch or description of each valve installation showing
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the following (Butterfly valves only):
l 1.
direction of flow 2.
disc closure direction 4
3.
curved side of disc, upstream or downstream (asyssnetric discs) i?
4.
orientation and distance of elbows, tees, bends, j ;,
etc. within 20 pipe diameters of valve it 5.
shaft orientation 6.
distance between valves
'r F.
Demonstration that the maximum combined torque developed by the valve in below the actuator rating.
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The applicant should respond to the " Specific Valve Type j
Questions" (Attachment 1) which relate to his valve.
j 3.
Analysis, if used, should be supported by tests which estab-j blish torque coefficients of the valve at various angles. As torque coefficients in butterfly valves are dependent on disc shape, aspect ratio, angle of closure flow direction and approach I
flow, these things should be accurately represented during tests.
Specifically, piping installations (upstream and downstream of the i
valve) during the test should be representative of actual field i
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1 installations. For example, non-symmetric approach flow from an elbow upstream of a valve can result in fluid dynamic torques of double the magnitude of those found for a valve with straight piping upstream and downstream.
4.
In-situ tests, when performed on a representative valve, should be performed on a valve of each size / type which is determined to represent the worst case load. Worst case flow direction, for example, should be considered.
5.
For two valves in series where the second valve is a butterfly valve, the effect of non-symmetric flow from the first valve should be considered if the valves are within 15 pipe diameters of each other.
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6.
If the applicant takes credit for closure time vs. the buildup of containment pressure, he must demonstrate that the method is conservative with respect to the actual valve closure rate.
Actual valve closure rate is to be determined under both loaded and unloaded conditions (if valves close faster at all, angles of opening under loaded conditions, no load closure time,may be used as conservative) and periodic inspection under tech. spec. require-I ments should be performed to assure closure rate does not increase with time or use.
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Specific Valve Type Questions The following questions apply to specific valve types only and need to be answered only where applicable. If not applicable,_sgate so.
i Y E A.
Torque Due to Containment Backpressure Effect (TCB)
For those air operated valves located inside containment, is the operator design of a type that can be affected by the containment pressure rise (backpressure effect) 1.e., where the containment pressure acts to reduce the operator torque capability due to TCB. Discuss the operator design with respect to the air vent and bleeds. Show ho.w TCB was calculated (if applicable).
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B.
Where air operated valve assemblies use accumulators as the fail safe feature, describe the accumulator air system configuration and its operation. Discuss active electrical components in the accumulator system, and the basis used to determine their quali-fication for the environmental conditions experienced. Is this i
system seismically designed? How is the allowable leakage from the accumulators determined and monitored?
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C.
For valve assemblies requiring a seal pressurization system (inflatable main seal), describe the air pressurization system configuration and operation including means used to determine their qualification for the environmental condition experienced. Is this system seismically designed?
D.
Where electric motor operators are used to close the valve has the minimum available voltage to the electric operator under both normal or emergency modes been determined and specified to the operator manufacturer to assure the adequacy of the operator to stroke the valve at accident conditions with these lower limit voltages available? Does this reduce voltage operation result in any significant change in stroke timing? Describe the i
emergency mode power source used.
E.
Where electric motor and air operator units are equipped with handwheels, does their design provide for automatic re-engagement of the motor operator following the handwheel l
mode of operation? If not, what steps are taken to preclude the possibility of the valve being left in the handwheel mode following some maintenance, test etc. type operation?
F.
For electric motor operated valves have the torques developed during operation been found to be less than the torque limiting settings?
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t Guidelines for Demonstration Of Operability of Purge and Vent Valves Operability c c' YJ In order to establish operability it must-be shown that the valve actuator's torque capability has sufficient margin to overcome or resist the torques and/or forces (i.e., fluid dynamic, bearing, seating, friction) that resist closure when stroking from the initial open position to full seated (bubble tight) in the time limit specified. This should be predicted on the pressure (s) established in the containment following a design basis LOCA.
Considerations which should be addressed in assuring valve design adequacy include:
1.
Valve closure rate versus time - i.e., constant rate or other.
2.
Flow direction through valve; AP across valve.
3.
Single valve closure (inside containment or outside centainment valve) or sinultaneous closure. Establish worst casei 4.
Containment back pressure effect on closing torque margins of air operated valve which vent pilot air inside containment'.
5.
Adequacy of accumulator (when used) siz.ng and initial charge for valve closure requirements.
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6.
For valve operators using torque limiting devices - are the settings of the devices compatible with the torques required to operate the valve during the design basis condition.
7.
The effect of the piping system (turns, branches) upstream and downstream of all valve installations.
8.
The effect of butterfly valve disc and shaft orientation to the fluid mixture egressing from the containment.
Demonstration Demonstration of the various aspects of operability of purge and vent valves may be by analysis, bench testing, in-situ testing or a combination of these means.
Purge and vent valve structural elements (valve / actuator assembly) must be evaluated to have sufficient stress margins to withstand loads imposed while valve closes during a design basis accident.
Torsional shear, shear, bending, tension and compression loads /
stresses should be considered. Seismic loading should be addressed.
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I Once valve closure and structural integrity are assured by analysis, testing or a suitable combination, a determination of the sealing integrity after closure and long term exposure to the containment environment should be evaluated. Emphasis should be directe'd at the effect of radiation and of the containment spray chemical eglutions on seal material. Other aspects such as the effect on sealfug from outside ambient temperatures and debris should be considered.
The following considerations apply when testing is chosen as a means for demonstrating valve operability:
Bench testing can be'used to demonstrate suitability of the in-service valve by reasor of its traceability in design to a test valve. The following factors should be considered when qualifying valves through bench testing.
1.
Wether a valve was qualified by testing of an identical valve assembly or by extrapolation of data from a similarly designed valve.
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2.
W ether measures were taken to assure that piping upstream and downstrear and valve orientation are simulated.
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3.
Whether the following load and environmental factors were considered s.
Simulation of IhCA
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Seismic loading c.
Temperature soak d.
Radiation exposure e.
Chemical exposure f.
Debris B.
Bench testing of installed valves to demonstrate the suitability of the specific valve to perform its required function during the pos,tulated design basis accident is acceptable.
1.
The factors listed in Items A.2 and A.3 should be considered l
when taking this approach.
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. j In-Situ Testing In-situ testing of purge and vent valves may be performed tb confirm the suitability of the valve under actual conditie When performing such tests, the conditions (loading, envif ent) to which the valve (s) will be subjected during the test should l
simulate the design basis accident.
NOTE: Post test valve examination should be performed to establish structural integrity of the key valve /
actuator components.
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OYSTER CREEK NUCLEAR GENERATING STATION i
N DOCKET NUMBER 50-271 OPERABILITY DEMONSTRATION OF CONTAINMENT PURGE AND VENT VALVE 1,S j~/
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l 1.0 Ristorical Background The licensee has been maintaining the purge and vent valves mechanically re-stricted from opening more than 30' in accordance with NRC's interim position as stated in the October 23, 1979 NRC letter. GPU committed to replace all containment purge and vent valves with qualified valves rather than qualifying 31, 1980. A subsequent letter the existing valves in their letter of Julyrequested an extension in the schedule for re-from GPU dated August 27, 1981 placing the containment purge and vent valves from December 1.1981 to the end The licensee's April of their cycle 10 reload refueling / maintenance outage.
submittal included a report number 4-01-82 by the Clow Corporation 1
19, 1984 containing operability demonstration information for the Clow replacement This information was reviewed and found to demonstrate operability for the Clow valves from the 90' full open position under LOCA conditions in valves.
26, 1984). The l
the proposed installation configuration (BNL TER dated Julysubmittal proposes c licensee's September 24, 1985 the existing valves with,Clow valves and contains an analysis (TDR 266, Revi-sion 1) that is intended to demonstrate valve operability for the existing valves under combined seismic and DBA/LOCA conditions from a restricted val opening angle of 30' open.
2.0 Preliminary Evaluation The existing valves are shown in the table below:
Valve Size Use Number (Inches)
Location Manufacturer _
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V27-1 18 Outside containment Centerline Drywell vent V27-2 18 Outside containment Centerline Drywell vent V27-3 18 Outside containment Rockwell Drywell purge V27-4 18 Outside containment Centerline Drywell purge V23-13 8
Outside containment Continental Drywell purge V23-14 8
Outside containment Fisher Drywell purge V23-15 8
Outside containment Continental Torus purge j
V23-16 8
Outside containment Fisher Torus purge j
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V28-17 12 Outside containment Fisher Torus vent l
V28-18 12 Outside containment Fisher Torus vent 24, 1985 submittal from CPU (Technical The analysis included in the September Data Report TDR Number 266, Revision 1, dated May 9, 1985) has been examined e
information for a complete review of operabil-and does not contain sufficient ity demonstration under the postulated accident conditions for the presently installed valves.
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The items listed below are intended as a guide for c'ompleting the information required to perform a valve operability review in order to comply with NUREG-0737 Item FtY.E.4.2.4.
IE, The licensee states on page 5 of TDR Dynamic Torque coefficients (Cr)_.
266, Revision 1, that the torque coefficients used in his analysis may be This is in-obtained from the valve manufacturers and references a letter.
Acceptable documentation in this area should in-adequate for a review.
reports that detail how the torque coefficients were determined clude test including a description of the test setup, test disc size and shape, aspect confidence can be estab-ratio, flow conditions, media used, etc., so that lished in the torque coefficients used in predicting valve dynamic loads.
The licensee's analysis TDR 266, Revi-
.Valve Installation Configuration _.
_sion 1 does not provide this information for each valve. Typically, the following information is required:
1.
Direction of flow.
Disc closure direction.
2.
Curved side of disc, upstream or downstream (asymmetric discs).
3.
Orientation and distance of elbows, tees, bends, etc. within 5 pipe 4.
diameters of valve.
5.
Shaft orientation.
6.
Distance between valves.
The licensee provides in TDR 266, Revision I the 4
1 Dynamic Torque Analysis _.
methodology used for,his torque analysis and references Oyster Creek Purge The and Vent Valve Analysis Calculation Book Calculation 1302 SX-322C-A07.
I referenced calculations, which should include assumptions used should be provided for the reviewer.
In order to demonstrate adequate torque margin by Actuator Torque Margin.
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comparing valve torque loads during closure to actuator closure torque availability, curves or incremental data, such as spring torque at various valve angles need to provided by the licensee.
The licensee has not indicated by ref-1 Seismic Qualification of Valves.
the valve assemblies are seismically qualified.
erencing documentation that
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As an example, for further guidance in understanding the type of information required for operability demonstration, the licensee should examine the Clow Number 4 " Purge and Vent Valve Operability Qualification Analysis Report" 82 submittod to the NRC with the CPU letter of April 19, 1984.
In addition, Attachment A to the November 29, 1982 NRC letter (V. Noonan to D. Crutchfield) e can be used as a guide for valve operability demonstration requirements.
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D(7A FT Finally, a comment on the statement 21, 1984 CPU submittal to the NRCi reproduced below contained in the February
- "The SER that was attached to your January 20, 1984 letter is factually incorrect.
In Section 3.0, JDegonse' ration, the SER refers to two (2) GPUN letters that were sent to the Nuc.
These letters deal with two (2) dif-ferent and separate approaches te the purge and vent questions.
The January 23, 1979 letter refers to the purge and vent valves presently in-stalled at Oyster Creek; while the January 13, 1983 letter addrelssed the new, qualified, purge and vent valves that are to be installed during
. the Cycle 11 refueling outage.
Because of thf.s confusion, the evaluation and summary sections of the SER state incorrect conclusions."
In examining the January 13, 1983 letter, the writer finds that the new, qualified purge and vent valves are not' addressed and therefore, takes excep-tion to GPU's statement.
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-3 Finally, a comment on the statement reproduced below contained in the February 21, 1984 GPU submittal to the NRC:
"The SEK that wac attached to your January
.0, 1984 letter is factually incorrect.
In Section 3.0, Demonstration, t se SER refers to two (2) CPUN letters that were sent to the NRC.
These letters deal with two (2) dif-ferent and separate approaches to the purge and vent questions. The January 23, 1979 letter refera to the purge and vent valves presently in-stalled at Oyster Creek, while the January 13, 1983 letter addressed the i
new, qualified, purge and vent valves that are to be installed during the Cycle 11 refueling outage. Because of this confusion, the evaluation and summary sections of the SER state incorrect conclusions."
In examining the January 13, 1983 letter, the writer finds that the new, qualified purge and vent valves are not addressed and therefore, takes excep-tion to CPU's statement.
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9 December 14, 1983 Note to:
J. Lombardo From:
J. Gray
SUBJECT:
0YSTER CREEK CORE SPRAY SPARGER AMENDMENT I agree with Colleen Woodhead's note to you to the effect that your SER wholly undercuts the basis for the proposed NSHC finding set out in your prior Federal Register notice of proposed action. Because of this, I believe you must either renotice this amendment providing another basis for the NSHC finding or, if you have no other basis, renotice giving a prior opportunity for hearing (as Colleen's note suggests) becauses you cannot make the NSHC finding.
I have an additional problem, however. This license change would modify the present license condition, which requires sparger replacement before any further operation, to allow operation without sparger replacement for the next fuel cycle, and operation beyond the next fuel cycle -
a contingent upon some undefined " acceptable" inspections. However, 60%
of the SER discusses how unreliable past inspections have been and essentially establishes that we have no basis today for determining that operation with the existing spargers would be safe. The SER actually says that we cannot assign any reliability to crack length measurements on which any deferral of sparger replacement could be based.
In contrast there is only one SER paragraph on why it is acceptable to operate without sparger replacement and that is rather vague and wholly unconvincing in view of the rest of the SER which clearly establishes that we don't know whether cracks are progressing and the sparger is degrading or not.
I see no justification for allowing further deferral of sparger replacement. Without a substantially more co.nvincing story on the adequacy of the existing sparger for another cycle of operation, I don't believe that you can issue this amendment.
(As an aside, your expectation that future inspections will allow meaningful comparisons with past inspection indications is not very useful. This SER fairly establishes that past inspection indications are unreliable. What purpose would be served in comparing future inspection results to past inspections in which we have no confidence).
f.. Gray
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