ML20151P155
| ML20151P155 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/01/1988 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 1525, NUDOCS 8808090229 | |
| Download: ML20151P155 (11) | |
Text
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TOLEDO l
l EDISON
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DONAM) C SHELTON Vce Preecert-Nuties Docket No. 50-346 M ' N * "'"
License No. NPF-3 Serial No. 1525
/ugust 1, 1988 United States Nuclear Regulatory Commission Documant Control Desk Vashington, D. C.
20555 Subj ect :
Containment Hydrogen Purge System Use During Plant Heatup and Power Ascension Gentlemen:
This letter provides an updFled status and additional information regarding venting of containment ivr pressure control during plant heatup and power a.ccension at the Davis-Besse Nuclear Power Station (DBNPS), Unit No. 1.
During plant heatup and power ascer.sior: (plailt operating Hedes 1-tp it is nc:essary to ver.1 the containment in order to maintaic, the internal pressure within DBN?S Tnchnical Specification 3.6.1.4 requirements.
In resyonse to an NRC letter of November 19, 1979 (LJg Noc 466) requesting information on how the l
DBNPS purge and vent systems satisfy the requirements of the NRC Branch Technical Position (42P) CSB 6-4, Toledo F-dison (TED) provid:3 a discussion of the Containment Purge and Exhaust System (Serial No. 577, dated January 18, 1980). -Similar information was nct provided for the Containment Hydrogen Furge (C1P) $ystem because, as indicated in that letter, the CHP system was not used for ccntainment pressure or temperaturo control during plant operation.
In TED's le.tter of March 14, 1983 (Serial No. 920), a commitment was made to maintain the Containment Purge and Exhavst isolation valves (CV5005 through 5008) closed in H6 des 1 through 4 vith control pover t. the valves removed until the Safety Features Actuation Signal Block Inhibit Feature vas installed.
Toledo Edisca no longer plans to install the ;1cek 2r.hibit feature, but rather to maintain these isolation valves closed with valve control power removed (see Serial No. 1504).
Subsequent to the commiteent to maintain valves CV5005-5008 I
closed, containment venting has been accotaplished by opening the CHP valves (CV5037 and CV5038) and relieving containment pressure to the station vent using the CHP System. The CHP System has a 0.5 inch orifi;? to limit flov.
Since f,fhbh O
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THE 10LEC3 EDISON COMPANY EDtSON PLAZA 300 MTSON AVENUE TOLEDO, Om 43652
Dockat No. 50-346 Licensa No. NPF-3 Serial No. 1525 Page 2 Seria) No. 577 indicated that the CHP System was not used for this purposer this letter serves to revise our notification to the NRC of the past and intended future use of the CHP System for containment pressure control.
TED intends to use the CHP System in the future to relieve containment pressure during plant heatup and power ascension using the CHP System as discussed below.
An evaluation of compliance of this system with the requirements of BTP CSB 6-4 is provided in Attachment i to this letter.
It oiscusses each item of the BTP in numerical order as indicated in NUREG-0800, Standard Reviev Plan (SRP),
Section 6.2.4.
The following is a synopsis of the CHP System operation during containment pressure reduction. The synopsis supplements the information provided in the attachment.
During plant heatup and power ascension (Modes 1-4) CHP valves CV5037 and CV5038 are opened to reduce the containment internal pressure.
A Safety Feate:e Actuation System (SPAS) incident leve) 2 signal vil) close the valves on a high containment pressure or a reactor coolant system low pressure condition. This feature vill not be blocked or overridden for use in containment pressure control.
The effluent flovpath vill be through 4-inch containment penetration piping and metor-oper but terfly valves to the 2-1/2 iach (~ 219 f t.
long) piping vhich is in' use for the hydrogen recombiner. The normal CHP HEPA and charco-embly is protected during containment pressure release by clos.
'ly locked open manual valve, CV60, upstream of the filter assembly ng the CHP containment isolation valves. This ensures the filte.
amaged and available for post-LOCA use.
The flow during plant heatup o..
er ascension is then directed through a new HEPA and charcoal filter assembly to the fuel handling area atmosphere. The effluent flovpath, described above, is shown on the simplified piping and instrument diagram for the containment hydrogen purge system presented herein as.
Because the use of the CHP isolation valves for containment pressure reduction occurs during plant heatup and power ascension, the radiation level in the containment is expected to be lov. The CHP valves, when not in use for containment pressure reduction, are normally closed. They would be required to j
open only atter a LOCA when the concentration of hydrogen in the containment has reached the 3 percent control limit. The DBNPS Updated Safety Analysis Report indicttes that this limit vould be reached in excess of 110 days after the LOCA event.
Based on the above, and the dircussion provided in Attachment 1 indicating compliance with the BTP CSB 6-4 Acceptance Criteria, TED believes that the use of the CHP piping as described abose for containment pressure reduction in operating Modes 1 through 4 is acceptable.
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Dockst No.'50-346 Liqtnsa No. NPF-3 Serial No. 1525 Page 3 Should you have any questions or require additional information, please contact Mr. R. V. Schrauder, Nuclear Licensing Manager at (419) 249-2366.
Very tr y yours, 10' RMC/ sag Attachments cc: A. B. Davis, Regional Administrator A. V. DeAgazio, NRC/NRR DB-1 Project Manager DB-1 Resident Inspector i
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Dock'st No. 50-346 Lic:nsa No. NPF-3 S: rial No. 1525 Page 1 Discussion of Containment Hydrogen Purge System and Branch Technical Position CSB 6-4 Acceptance Criteria i
1
Docket No. 50-346 License No. NPF-3 Serial No. 1525 Page 2 Branch Technical Position CSB 6-4 Discussion B.1.a General Design Criterion 54 requires The Containment Hydrogen that the reliability and performance Purge isolation valves capabilities of containment isolation (CV5037 & CV5038) are valves reflect the importance of safety 4 inch motor operated of isolating the systems penetrating butterfly valves designed the containment boundary. Therefore, by Fisher Controls.
They the performance and reliability of the are designed and tested in purge system isolation valves should be accordance with ASHE consistent with the operability Section III, Subsection assurance outlined in BTP HEB-2, NC and ND.
They are "Pump and Valve Operability Assurance qualified to Seismic Program" (also see SRP Section 3.10).
Class I requirements and The design basis for the valves and they have'been verified capaole actuators should include the buildup of closing during the of containment pressure for the LOCA containment maximum break spectrum, and the supply line transient pressure and exhaust line flows as a function (37 psig) resulting from of time up to and during valve the worst break LOCA. The closure.
valves are designed to function for a 45 psig differential pressure.
B.1.b The number of supply and exhaust only one exhaust line is lines that may be used should be being used during limited to one supply line and one containment pressure re-exhaust line, to improve the re-duction.
liability of the isolation function as required by General Design Criterion 54, and to facilitate compliance with the requirements of Appendix K to 10CFR50 regard-ing the containment pressure used in the evaluation of the emergency core cooling system effectiveness and 10CFR100 regarding offsite radiological consequences.
B.1.c The size of the lines should not The Containment Hydrogen exceed about eight inches in Purge valves discharge inte i
diameter, unless detailed a 4 inch line which is justification for larger line subsequently reduced to sizes is provided, to improve 2 1/2 inches.
This small the reliability and performance line size vill facilitate capability of the isolation and compliance with the re-containment functions as required quirements of 10CFR50
Docket No. 50-346 Licensa No. NPF-3 Serial No. 1525 i
Page 3 Branch Technical Position CSD 6-4 Discussion by General Design Criterion 54, Appendix K and ensure the and to facilitate compliance with offsite radiological the requirements of Appendix K to consequences are within the 10CFR50 regarding the containment 10CFR100 requirements.
pressure used in evaluating the ECCS effectiveness and 10CFR100 regarding the offsite radiological consequences.
B.l.d As required by General Design The Containment Hydrogen Criterion 54, the containment Purge isolation valves isolation provisions for the meet the requirements purge system lines should meet for the containment the standards appropriate to isolation system as-CSF; i.e., quality, redundancy, described in Section testability and other appropriate 6.2.4.2 of the USAR.
criteria, to reflect the importance Although the valve to safety of isolating these lines.
arrangeaent does not General Drsign Criterion 56 comply with the explicit establishes explicit requirements requirements of General for isolation barriers in purge Design Criterion 56 which system lines, designates:
- 1) One locked closed isolation valve inside and one locked closed isolation valve out-side containment; or
- 2) One automatic isolation valve inside and one locked isolation valve outside containment; or
- 3) One locked closed isolation valve inside and one automatic isolation valve outside containment; or
- 4) One automatic isolation valve inside and one automatic isolation valve outside containment, the exception to General Design Criterion 56 (two motor operated valves outside containment) complies with the intent of BTP CSB 6-4 relative to provisions for quality, redundancy and testability. This arrangement is consistent with the original design as presented in FSAR Section 6.2.4.2.
Dockst No. 50-346 Licensa No. NPF-3 Sarial No. 1525 Page 4 Branch Technical Position CSB 6-4 Discussion B.1.e To improve the reliability of The Containment Hydrogen the isolation function, which is Purge isolation valves addressed in General Design are actuated by diverse Criterion 54, instrumentation parameters (high and control systems provided to containment pressure, lov isolate the purge system lines RC pressure) and by a should be independent and separate and independent actuated by diverse parameters; e.g.,
source of power to each containment pressure, safety
- valve, injection actuation, and containmant radiation level.
Furthermore, if energy is required to close the valves, at least two diverse sources of energy shall be provided, either of which can effect the isolation function.
B.I.f Purge system isolation valve closure The Containment Hydrogen times, including instrumentation Purge isolation valve delays, should not exceed 5 seconds, closure time, including to facilitate compliance with 10CFR100 instrument delays, is regarding offsite radiological 75 seconds, as indicated in consequences.
Technical Specification Table 3.3-5.
Although this closure time exceeds the closure time recommended by the NRC (5 seconds), it has been evaluated and concluded that the small amour.t of containment atmosphere dis-charged during closure vill not affect compliance with 10CFR100 vith regard to offsite radiological consequences.
B.l.g Provisions should be made to ensure The Containment Hydrogen that isolation valve closure vill Purge isolation valves not be prevented by debris which are protected from debris could potentially become entrained entrained in the escaping in the escaping air and steam, air and steam. A stainless steel mesh is velded to the entrance of the piping upstream of the valves to ensure valve closure vill not be affected by debris.
DockstLNo. 50-346 Lictnsa No. NPF-3 Sarial No. 1525 Page 5 Branch Technical Position CSB 6-4 Discussion B.2 The purge system should not be The Containment Hydrogen relied on for temperature and Purge system is used to humidity control within the relieve pressure during containment.
heatup and power ascension and is not relied on for temperature or humidity control within the containment during normal power operation.
B.3 Provisions should be made to Apart from its use following minimize the need for purging an accident, the Containment of the containment by providing Hydrogen Purge system is containment atmosphere cleanup used during heatup and power systems within the containment.
ascension for containment pressure reduction only.
Therefore, the use of this system is limited.
B.4 Provisions should be made for testing Provisions for periodic the availability of the isolation testing of the isolation function and the leakage rate of the valves are in place and are isolation valves during reactor operation.
described in Section 6.2.4.4 of the-USAR. This testing can be performed during reactor operation.
B.S.a An analysis of the radiological The Containment Hydrogen consequences of a LOCA should bc Purge isolation valves performed. The analysis should be vill be automatically closed done for a spectrum of break sizes, by SFAS signal generated by and the instrumentation and setpoints pressure transr.itters tant vill actuate the purge valves PT2000-2003 for a containment closed should be identified. The pressure of 18.4 psia or by source term used in the radio-pressure transmitters PTPC2A3, logical calculations should be based RC2A4, RC2B3, RC2B4 for a on a calculation under the terms of reactor coolant pressure of Appendix K to detereine the extent 1620.75 psig. The amount of of fuel failure and the concomitant steaa released through this release of fission products, and the system during the isolated fission product activity in the primary valves clesure vill be less coolant activity. A pre-existing iodine than 75 lbs.
This release spike should be considered in determining was calculated assuming a primary coolant activity.
The volume of containment pressure of 37 containment in which fission products psig and a valve closure time
Docket No. 50-346 Licenas No. NPF-3 Serial No. 1525 Page 6 Branch Technical Posiscion CSB 6-4 Discussion are mixed should be justified, and the of 75 seconds. Assuming an fission products free the above sources iodine spiking source term of should be assumed to be released through 60 pCi/gm of dose equivalent the open purge _ valves during the maximum I-131 in the primary coolant, interval required for valve closure. The the thyroid dosed at the site radiological consequences should be boundary vill be less than 0.2 within guideline values.
Rem.
Credit for filters and plateout is not considered.
Thus the expected doses through this path are only a small fraction of 10CFR*00.
B.5.b An analysis should be performed The Containment Hydrogen which demonstrates the acceptability Purge isolation valves provisions made to protect structures vill be discharging, during and safety-related equipment; e.g.,
containment pressure re-fans, filters, and ductvork, located duction, into the piping beyond the purge system isolation provided for the hydrogen valves against loss of function from recombiner. This is the environment created by the escaping approximately 219 ft. of air and steam.
1/2 inch diameter piping rated at 150 lb. and seismically qualified.
This piping terminates in the fuel handling area. The discharge of steam to this area vill not affect the operation of safety related equipment required to mitiga.te the consequences of a LOCA. The piping vill connect to a temporary HEPA and charecal filter and vill be used for containment depressurization during plant j
heatup and power ascension.
1 The filter assembly is not j
safety related or seismically qualified.
Failure of this 4
filter assembly in the event of a LOCA or seismic event vill not affect the function of safety related equipment.
D.5.c l
An analysis should be performed An analysis of the contain-of the reduction in the containment ment pressure reduction pressure resulting from the partial through the 2 1/2 inch
Dockat No. 50-346 Licensa No. NPF-3 Sgrial No. 1525 Page 7 Branch Technical Position CSB 6-4 Discussion loss of containment atmosphere during Hydrogen Purge line for a the accident for ECCS backpressure duration of 75 seconds has determination.
determined that the containment pressure response envelops *,he B&V assumed minimum back pressure and, thus, the ECCS analysis is not affected.
B.S.d The maximum allovable leak rate The Containment Hydrogen of the purge isolation valves Purge isolation valves should be specified on a case-by-case are designed for a basis giving appropriate consideration differential pressure to valve size, maximum allovable leakage of 45 psig.
This differential rate for the containment (as defined in pressure is higher than the Appendix J to 10CFR50), and where peak pressure against which appropriate, the maximum allovable the valves must close.
The bypass leakage fraction for dual valves are tested for containments.
leakage, in place, as part of the Integrated Leak Rate Test (ILRT) and Local Leak Rate Test (LLRT). The allovable leakage of the valves under LOCA conditions is determined, in combination with the other leakage paths, as part of the ILRT and LLRT, with acceptance criteria established in Technical Specification 3.6.1.2.c
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