ML20024C958
| ML20024C958 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 07/15/1983 |
| From: | Broehl D PORTLAND GENERAL ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| TAC-46735, NUDOCS 8307210223 | |
| Download: ML20024C958 (10) | |
Text
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s N M MOcuptuor Donald J.Broehl Assstant Vice Preskjent J
July 15, 1983 1
Trojan Nuclear Plant Docket 50-344 License NPF-1 Director of Nuclear Reactor Regulation ATTN:
Mr. Robert A. Clark, Chief Operating Reactors Branch No. 3 Division of Licensing U. S. Nuclear Regulatory Cosuaission Washington DC 20555
Dear Sir:
Fire Protection Exemption Request and Additional Technical Justification Relative to Certain Appendix R Audit Findings The purpose of this letter is to request an exemption from certain Appendiz R requirements and to provide additional justification and clarification in response to certain findings identified as part of the NRC Appendix R audit of the Trojan Nuclear Plant conducted during the week of June 20-24, 1983. to this letter is a request for exemption, pursuant to 10 CFR 50.12, from the fire protection requirements of Section III.0 of Appendix R to 10 CFR 50 for the reactor coolant pump oil collection system holdup capacity.
Attachments 2 and 3 to this letter are. technical justifications supporting redundant safe shutdown capabilities for the boric acid transfer pumps and pressurizer heaters. PCE previously committed, in a July 8, 1983 letter to NRC Region V, to provide this justification ~. The redundant capability described in Attachments 2 and 3 is currently available as backup for the boric acid transfer pumps.and pressurizer heaters, and will be reviewed in detail for conformance to Appendix R criterla as part of our detailed Appen-
-diz R receview. Based on this review, the-identified redundant equipment will either be modified to meet. Appendix R requirements, or further exemp-
- tions from Appendix R requirements will be requested, if justified.
We'have also included, as Attachment 4, a cIsrification of the fire area
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definition as used by PGE in its initial Appendix R review. This clarifi-cation is important'in' understanding the cause of several of the findings identified during the NRC Appendix R audit.
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W Geriard MCostyxviy Mr. Robert A. Clark July 15, 1983 Paae 2 As indicated in PGE's letter of July 8, 1983 to Region V, we expect to file further exemption requests from Appendix R requirements as our detailed Appendix R reanalysis progresses.
It was also noted in our July 8 letter that any deficiencies identified during this review will be promptly re-ported in accordance with Technical Specification requirements, and any necessary modifications of Plant design or administrative controls will be performed as expeditiously as reasonably achievable. Further exemptions from Appendix R requirements will be requested only where strong justifica-tion of equivalent protection to the requirements of Appendix R exists.
Sincerely,
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av Attachments c:
Mr. Lynn Frank, Director Ctate of Oregon Department of Energy Mr. John B. Martin Regional Administrator U. S. Nuclear Regulatory Conunission Region V N\\
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h Trojan Nuclear Plant Mr. Robert A. Clark Docket 50-344 July 15, 1983 License NPF-1 Page 1 of 2 ATTACHMENT 1 APPENDIX R EXEMPTION REQUEST FOR REACTOR COOLANT PUMP OIL COLLECTION SYSTEM PGE committed to install a reactor coolant pump (RCP) oil collection system prior to the issuance of Appendix R to 10 CFR 50.
Section III.O of Appendix R requires that " leakage shall be collected and drained to a vented closed container that can hold the entire lube oil system inven-tory".
Although each of the two oil collection tanks are sized to hold more than the entire lube oil system inventory from a single RCP, the design basis for this system did not assume that all four RCP lube oil systems would fail simultaneously. During the Appendix R audit, the NRC provided a clarification that Appendix R was meant to apply to the entire lube oil system of all four RCPs. Therefore, exemption is requested from Section III.O of Appendix R to 10 CFR 50 for the Trojan Nuclear Plant to the extent that leakage be collected and drained to a container that can hold the entire lube oil system inventory (ie, from all four RCPs).
Justification for this request is as follows.
Each of the four RCPs has a self-contained lubricating oil system of 265-gal capacity. A Seismic Category I oil spillage collection system has been installed for each RCP.
This collection system consists of a set of catch basins, drip pans, and enclosures assembled as attachments to the pump motor at strategic locations to contain or catch any spilled or leaking oil and direct it to a suitable drain. The drains then direct any spilled or leaking oil to a collection tank.
Two collection tanks of 306-gal capacity are provided to collect spilled oil. Each tank serves two pumps (A & D, B & C) and is located midway between each pair of pumps. The tanks are vented directly to Containment atmosphere. Any tank overflow would be to the immediate floor area beneath tho tank and would ultimately drain to either 4-in floor drains provided in the vicinity of each RCP, or additional floor drains and drainage sumps between the RCPs. These drains are routed to the Containment Building sump.
The oil collection system is designed to keep oil leakage away from hot spots on the pump or pump motor. The central leakage points protected include 4-in. connections, drain plugs, fill points, upper and lower reservoirs, site glasses, lift pumps, and external oil coolers. Any RCP oil fire would be limited to a small amount of residual oil that remains on pumps or collection system surfaces and could be easily extinguished manually by hose stations provided on the 45-ft elevation inside contain-ment. It is unlikely that any overflow from the collection tanks would come into contact with hot RCS surfaces since the tanks are separated by more than 25 ft horizontally from, and are on a lower elevation than, each RCP.
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r Trojan Nuclear Plant Mr. Robert A. Clark Docket 50-344 July 15, 1983 License NPF-1
' Attachment 1 Page 2 of 2 Therefore,-given the low probability of-gross rupture of multiple RCP lube oil systems that would result in overflow of the' collection tank, and the low probability.that in an overflow event oil ignition would However,-modifications will be made in order _to ensure that.any overflow occur, the present design poses no threat to safe shutdown capability.
from the'RCP oil collection tanks will be properly contained and/or drained so that it'will not present a fire hazard to redundant safety-related equipment. This will be accomplished by implementing one of the following options: 1) curbing under the tanks to channel any overflow to nearby floor drains, 2) running a hard-piped connection from the overflow pipe to a nearby floor drain 3) installing additional tank capacity, or 4)-providing a dike around each existing collection tank with a holding capacity large enough:to contain the lube oil volume of one RCP.
i The latter option is. currently preferred, but a final decision will depend on further design review. The proposed schedule for implementing the selected design option is during the 1984 refueling outage.
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Trojan Nuclear Plant Mr. Robert A. Clark Docket 50-344 July 15, 1983 License NPF-1 Page 1 of 1 ATTACHMENT 2 JUSTIFICATION SUPPORTING REDUNDANT SAFE SHUTDOWN CAPABILITY FOR BORIC ACID TRANSFER PUMPS PGE-1012 identifies the boric acid transfer (BAT) pumps as required for safe shutdown. The BAT pumps and boric acid tanks are located on Eleva-tion 51 ft of the Fuel Building. The pumps and tanks are located in the same fire area, but in a room separate from other areas on this elevaFlon.
Elevation 61 ft is provided with three hose stations, two 20-lb dry chemical extinguishers, and fire detectors located near the boric acid panels, BAT pumps, and in the coseidors.
The BAT pumps and boric acid tanks provide the normal supply of boric acid for RCS boration and ensure sufficient boric acid solution to achieve a cold shutdown from full power operation immediately following refueling with the most reactive control rod not inserted, plus operating margins. However, as discussed in Updated FSAR Section 9.3.4.3.1, an adequate quantity of boric acid is also available in the refueling water storage tank (RWST) to achieve cold shutdown conditions.
In the event of a fire that damages the BAT pumps, the RWST outlet could be aligned to the suction of the centrifugal charging pumps (CCPs), and letdown flow manually controlled to the Chemical and Volume Control System (CVCS) holdup tanks, to effect RCS boration. Existing Plant procedures (Off-Normal Instruction ONI-10. " Emergency Boration") address this method of RCS boration.
The capability to achieve cold shutdown without the BAT pumps has been confirmed by analysis. The analysis demonstrated that boration requirements at core beginning-of-life (BOL) are greater than at core end-of-life (EOL). The analysis further demonstrates that a shutdown margin of 1.6 percent with the RCS at 200*F can be achieved using 2000 ppm boron from the RWST at BOL with the most reactive control rod withdrawn. This would require charging approximately 10 percent of the RWST volume to the RCS, and letdown of reactor coolant approximately equivalent to the volume of one (of three) CVCS holdup tank.
Since safe shutdown can be achieved without using the BAT pumps, the current fire protection design of the BAT pumps is considered adequate.
This position is also consistent with Item 4(1) of Enclosure 1 to NRC Generic Letter 81-12, dated February 20, 1981, in that boration capability can be provided by a charging pump taking suction from a borated water supply. As part of PGE's detailed reanalysis of Appendix R, the redun-dant method described above for boration capability will be reviewed for conformance to Appendix R criteria. Any identified deviations from Appendix R criteria will be resolved either by modifying existing Plant fire protection features and/or procedures, or by a justified exemption 7
request.
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Trojt3 Nucloce Picat Mr. Rab rt A. Clerk Docket 50-344 July 15, 1983 License NPF-1 Page 1 of 4 ATTACHMENT 3 JUSTIFICATION SUPPORTING REDUNDANT SAFE SHUTDOWN CAPABILITY FOR PRESSURIZRR HEATERS PGE-1012 identifies the pressurizer heaters as required for safe shut-down. Load Centers B09 and Blo, which contain breaker controls for the pressurizer heaters, are located on Elevation 45 ft of the electrical penetration area outside Containment. Fire protection features for this area include an automatic suppression system, fire detectors, a hose station, and portable fire extinguishers.
Subsequent evaluation has shown that Plant cooldown via natural circula-tion to cold shutdown conditions can be achieved without the availability of the pressurizer heaters. Procedures currently in place (Emergency Instructions EI-0, " Reactor Trip"; EI-0.1,'" Reactor Trip Recovery"; and EI-0.2, " Natural Circulation Cooldown") provide adequate guidance to the operator to conduct such a cooldown without pressurizer heaters.
Control of RCS pressure is important to maintain sufficient subcooling margins and preclude inadequate core cooling. Assuring that a sufficient
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pressure is maintained is complicated by the unavailability of pressurizer heaters because shrinkage of the primary coolant as well as ambient heat i
losses from the pressurizer tend to reduce primary pressure. Two techniques are available, however, to malatain adequate subcooling margins:
a.
Cooldown the RCS faster than the pressurizer.
b.
Use centrifugal charging pumps (CCPs) to compress the pres-surizer vapor space and/or any void formations.
(If necessary, the RCS can be operated in a water-solid condition.)
Analysis indicates that the pressurizer will cool at a rate of approxi-mately 10*F per he due to ambient heat losses alone. Assuming.pressuriz-l
'er_ level can be maintained during RCS cooldown, changes in pressurizer j=
temperature, and therefore pressure, will result only from the ambient losses.
If the RCS cooldown rate is greater than the pressurizer cooldown rate, then the subcooling margin available immediately after reactor trip will always be maintained. In particular,-an analysis was performed.to show that RCS temperature could be. reduced to 350*F while
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the pressurizer temperature remains above RCS bulk temperature. Once
.below 350*F, the Residual Heat Removal (RHR) System would be utilized to i
maintain pressure control and continue the cooldown, in.accordance with General Operating Instruction GOI-4, " Plant Shutdown From Not Standby to Cold Shutdown."=
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Trojan Nuclear Plant Mr. Robert A. Clark Docket 50-344 July 15, 1983 License NPF-1 Page 2 of 4 A description of this analysis follows.
Background documentation pro-vided with Westinghouse Owners Group (WOG) Guidelina ES-0.1, " Reactor Trip Recovery," indicates pressurizer conditions of 637'F/ 2000 psia /
30 percent level and RCS temperature of 557'F exist following a reactor trip from full power. The remaining scenario and parameter valves are
= based on PGg's analysis. Due to a loss of offsite power, natural circu-lation is established to remove decay heat. Without pressurizer heaters, ambient heat losses will tend to reduce the pressurizer temperature.
Under saturated conditions, pressurizer pressure will decrease propor-tionally. Pressurizer level is maintained at 30 percent, even if the moderator temperature decreases, by use of the centrifugal charging pumps.
By evaluating changes in pressurizer heat content from one temperature condition to another and comparing the change to an ambient heat loss rate (conservatively assumed to be 208 kW), the length of time required for such a temperature change to occur can be determined. Time intervals of 7.5 he for the pressurizer to cool from 637*F to 567*F, and 6.3 he for the pressurizer to cool from 567*F to 500*F, were calculated.
An RCS cooldown rate of 15*F per he was then coupled to these time spans i
to determine what RCS temperatures could be attained. A total time span i
of 13,8-he allows for an RCS cooldown from 557*F to 350*F.
These results are illustrated on the attached figure. Note that more than a 50*F sub-t cooling margin is maintained.
The WOG Guideline ES-0.2, " Natural Circulation Cooldewn," recommends a natural circulation cooldown rate of not more than 25*F per he to assure that the upper head region cools as quickly as the active portion of the RCS.
The status of control rod drive mechanism (CRDM) cooling fans also impacts how soon after RCS cooldown below 350*F that the RCS may be de-pressurized (to 400 psia) to place the RHR System in operation. The deliberately slow cooldown rate and operation of CRDM cooling fans tend to minimize the possibility of void formation in the upper head region.
A 15*F per he cooldown rate with all CRDM cooling fans operating assures that void formation in the upper head is not a problem and that the RCS can be depressurized to 400 psia and placed on RHR just as soon as an RCS temperature less than 350*F is established.
Trojan emergency procedures, based upon the WOG Guidelines,. provide adequate operator guidance in conducting a natural circulation cooldown.
However, operability of pressurizer heaters is assumed. Without heaters, some restriction on-auxiliary spray and pressurizer level changes will be i -
necessary to maintain the appropriate RCS pressure. Possible clarifica-tion of the existing procedure with respect to pressure control is being evaluated. At the very least, Plant cooldown without pressurizer heaters j
will be included in the operator training program.
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Trojan Nuclear Plant Mr. Robert A. Clark Docket 50-344 July 15, 1983 License NPF-1 Page 3 of 4 m
Even in the event that CRDM cooling fans are not operable and/or diffi-culty in maintaining natural circulation cooldown is experienced such that the cooldown rate is less than 15*F/hr, safe shutdown can be achieved. However, operators may be required to make additional use of CCPs to control RCS pressure. Compression of the pressurizer vapor space may be necessary to maintain relatively high RCS pressure for longer periods of time.
Trojan emergency procedures provide operator guidance in dealing with inoperable CRDM cooling fans, void formation, and varying natural circu-lation cooldown rates.
In any event, natural circulation cooling is not dependent upon subcooled conditions if void formation is kept in check.
Since safe shutdown can be achieved without using the pressurizer heaters, the current fire protection design of the pressurizer heaters is con-sidered adequate. This position is also consistent with Item 4(3) of to NRC Generic Letter 81-12 which indicates that either charging pumps or pressuciter heaters (and use of the letdown system) can be used for reactor coolant system pressure control capability. As part of PGE's detailed reanalysis of Appendix R, the redundant method described above for RCS pressure control will be reviewed for conformance to Appen-dix R criteria. Any identified deviations from' Appendix R criteria will be resolved either by modifying existing Plant fire protection features and/or procedures, or by a justified exemption request.
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Trojan Nuclear Plant Mr. Robert A. Clark Docket 50-344 July 15, 1983 License NPF-1 Page 1 of 1 ATTACHMENT ~4 CLARIFICATION OF FIRE AREA DEFINITION PREVIOUSLY USED BY PGE A major cause of several findings identified during the NRC Appendix R sudit, conducted on June 20-24, 1983, is the more restrictive defini-tion of the term " fire area" being imposed by the NRC.
PGE based its initial Appendix R review on the analysis contained in PGE Topical Report,
'PGE-1012. " Trojan Nuclear Plant Fire Protection Review", since it 1) de-scribed the fire protection design and analycis used for Trojan, 2) docu-mented the resolution of NRC questions and positions, and 3) served as a basis for the NRC's approval of fire protection design at Trojan (see NRC Safety Evaluation Reports dated March 9, 1978, March 25, 1980, and October 6, 1980). The assumptions used in the fire hazards analysis are described in Section 3.2 of PGE-1012 and in the response to NRC Question Nos. 47 and 48 (tha latter were submitted to the NRC on June 8, 1977 as part of Amendment 2 to PGE-1012).
PGE's response to Question 47(a) stated the following:
"The term "affected area" is defined as a " fire zone" or an area containing combustibles bounded by either physical barriers such as walls, doors or dikes, or spatial separation, which tends to isolate one area from another. The "affected area" is originally celected on the basis of engineering judgment and then analyzed to justify its selected boundary. If the boundary cannot be realistically justi-4 fled, the affected area is expanded to barriers that can withstand the maximum calculated fire and realistically be justified."
Since this analysis was approved by the NRC, and the term " fire area" was not redefined in Appendix R to 10 CFR 50, PGE's Appendix R compliance review was based on those areas identified in PGE-1012 as containing redundant. safe shutdown components. Since Section III.C of Appendix R gives protection criteria for redundant equipment located "within the same fire area", the Appendix R fire protection review was based on the fire areas considered in PGE-1012.
The NRC's use of a more restricted definition of the term " fire area" becare readily apparent during the Appendix R audit conducted at Trojan last month. Additional clarification was also obtained last month when PGE obtained an internal NRC memorandum from R. H. Vollmer to D. G.
Eisenhut, dated May 25, 1983, which provides clarification-of NRC positions on certain Appendix R requirements. This memo' included a clarification of the definition of fire area and a recommendation that j
the clarification be sent by letter to all licensees. The clarification l
. pertains to plants such as Trojan whose fire hazards analysis were based on' fire zones (not bounded by fire barriers) rather than firefareas l
(bounded by fire barriers),'and states that the more restricted term l
should be used in Appendix R reviews.
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