ML19290E300
| ML19290E300 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/20/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19290E297 | List: |
| References | |
| NUDOCS 8003100174 | |
| Download: ML19290E300 (9) | |
Text
Enclosure 1 SAFETY EVALUATION 3.0 EVALUATION The following provides our evaluation of the incomplete items.
Numbers in parenthesis following each heading refer to the Sections of our previously issued SER which address these incomplete items.
3.1 Protection of Essential Power Sources (3.2.1)
Our SER noted that the licensee would review the electrical power distribution system and routing of non-essential load cables connected to essential power sources required for safe shutdown to verify that the integrity of redundant power supplies is not dependent upon operation of isolation devices operated by fault currents resulting from fire damage.
The licensee's submittal dated January 30, 1978, indicated that this review has identified three cases where the integrity of redundant power supplies is dependent upon operation of isolation devices operated by fault currents resulting from fire damage. Two of these are non-essential cal 'es fed from motor control centers which do not supply safe mutdown loads.
Fire induced faults on these cables, if not cleared by the load supply breakers would be cleared by the main feed breaker.
The opening of the main feed breaker would not affect safe shutdown.
In the third case, Train "B" cables are in the same tray with a non-essential cable from a train "A" motor control center which provides power to safe shutdown loads.
If the load supply breaker for these cables failed to clear fire induced faults, the power to safe shutdown equipment connected to these buses could be lost.
The requirement for not depending on fault curmnt actuated devices to assure the integrity of redundant power supplies is found in Revision 1 to Regulatory Guide 1.75.
This guide applies to plants whose construction permits are issued on or after February 1, 1974. Appendix A to BTP 9.5-1 includes the divisional cable separation guidelines of Regulatory Guide 1.75, i.e.,
the 3' horizontal and 5' vertical separation distance required between redundant cable trays.
It was not inte7dec to backfit all the requirements of Regulatory Guide 1.75.
Because Vermont Yankee's construction pennit was issued in November 1966, it need not be backfitted to these requi rements.
Reasons for not requiring such a backfit are:
(1) breakers are designed for the express purpose of providing protection against faults; (2) the coordination of breakers (that is, the sizing and timing of sequential breakers in a zoned protection system) is such as to cause the load breaker to open at a much lower current value than the main feed breaker and in a shorter time, thus preventing the loss of the loads fed by the same main breaker and bus; (3) the fire induced simultaneous faulting of a number of load cables to produce sufficiently high currents of sufficient duration to cause a main breaker to open is highly unlikely due to the short time required for a breaker to clear faults in comparison with the slower time progressed nature of a fire; and (4) in the unlikely event a main feed breaker were to open because of a load line fault, the breaker could be closed to nrovide power to the remaining loads once the failed braner has been cleared manually.
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. Based on the above stated reasons and the fire protection provided for these cables, we conclude that further separatica of these cables for the purpose of protecting against loss by the described failure of fault actuated devices is not required.
3.2 Flame Retardant i.iatings (3.2.2)
Our SER noted that the use of flame retardant coatings on electrical cables in trays and risers in the switchgear room has been recomended by the staff and that the licensee would evaluate the impact of flame retardant coatings on cable derating to determine if sufficient design margin exists to use this method to improve the fire resistance of electrical cables.
The licensee's submittal dated January 30, 1978, indicated that the application of a fire retardant coating to all electrical cables routed in cable trays in the switchgear room is not feasible because there is no derating margin.
The licensee has previously committed to install an automatic CO2 suppression system which is actuated by smoke detectors.
By letter dated September 14, 1979, the licensee agreed to coat the cables in cable trays at divisional crossovers. The cables will be coated for a minimum distance of 5 feet beyond the nearest redundant division cables. A fire stop will be provided in any conduit connecting one safety train to another.
In addition, where conduit containing safety related cable from one division crosses cable trays containing safety related cable from a redundant division, fire r tardant coatings which extend to a minimum of 2-1/2 feet beyond the conduit crossing will be provided. He has agreed to add coatings at redundant divisional crossovers and to show capability to achieve and maintain shutdown conditions independent of the switchgear room.
We accept the proposed application of flame retardant coatings at the crossovers of redundant divisions as a means of slowing the progress of a fire in the switchgear room.
3.3 Primary Containment Analysis (3.2.4)
Our SER noted that the fire hazards analysis for the primary containment was not completed and the adequacy of the fire protection features could not be evaluated.
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. The containment is not presently inerted although it is anticipated that inerting may be necessary in the future to satisfy other requirements. However, the licensee has indicated via telecon that the modifications he proposes are dependent on the outcome of the staff's decision on inerting. The area between the biological shield and containment wall contains support equipment including recirculation pumps, motors, and auxiliaries. Combustibles consist of 50 gallons of lube oil in each of the recirculation pumps. The motors are equipped with sensors for oil and bearing temperature. Armoflex combustible pipe insulation is installed in the containment.
The fire protection for the containment consists of containment sprays, temperature sensors, and oil level alarms. There are no fire detection systems. The air temperature is, however, detected by RTD's.
Because of the lack of detection, the concentration of cables near pumps and penetration areas, limited access, and the probable loss of some nuclear instrumentation and rod position cabling, the licensee by letters dated January 30, 1978 and September 14, 1979, proposed the following modifications:
1.
A means for early detection of oil fires inside the containment.
'2.
A collection system for small oil leaks from each reactor recirculation pump motor.
3.
Fixed (manual) suppression for oil fires at each reactor recirculation pump motor (density of.3 gpm/sq. ft.).
4.
Replacement of all combustible "armoflex" insulation with non-combustible insulation.
We accept replacement of combustible insulation with non-combustible insulation; however, the fire protection does not meet minimum requirements for BWR containments. We will require the following:
Standpipe and hose stations shall be outside the drywell with adequate lengths of hose to reach any location inside the drywell with an effective hose stmm.
The Reactor Recirculation Pump lubrication system shall be protected by either an oil collection system, or an automatic fire suppression system.
. Oil collection srtems shall be capable of collecting lube oil from all po'.atial pressurized and unpressurized leakage sites in the reactor recirculation pumps' lube oil systems and drain the oil to a vented closed container.
Requirements for a flame arrestor in the vent shall be determined on the basis of flash point characteristics of the oil involved.
Leakage points to be protected shall include lift pump and piping, overflow lines, lube oil cooler, oil fill and drain li.es and plugs, flanged connections on oil lines and lube oil reservoirs where such features exist on the reactor recirculation pumps. Leakage shall be collected and drained to a closed container that can hold the entire lube oil system inventory. The drain line shall be large enough to accommodate the largest potential oil leak.
To provide adequate protection for an SSE, one of the following should be provided:
a.
The lube oil system components whose failure could result in leakage should be designed to withstand an SSE without leakage; and, the dropping of oil collection system components during an SSE should not cause loss of operability of safety-related equipment; or b.
The oil collection system should be designed to withstand an SSE and continue to be able to collect and drain leakage that may occur during an SSE.
In this case the oil collection system should be adequate to collect-oil from any external lube oil piping not designed to withstand an SSE, in addition to leakage from points identified above.
If an automatic fire suppression system is selected, either the automatic and manual fire suppression system or the lube oil system components whose failure could result in leakage should be designed to withstand an SSE.
All of the above requirements are now included in Appendix R to 10 CFR Part 50 which became effective at a future date.
We, therefore, expect that the licensee will conform to these requirements. Subject to conformance to these requirements, these items are satisfactorily resolved.
. 3.4 Gas Suppression Systems (3.2.5)
Our SER noted that the licensee would provide the description for the actuation of automatic CO2 systems including those interlock features incorporated to disable the system when personnel would be working in the area.
The licensee's submittal, dated September 14, 1979, indicated that both the switchgear room and the cable vault systems will operate in a similar manner upon actuation of ionization detectors. Upon the receipt of each of three successive alarms, an output signal is sent frwn a counting module to initiate a preprogramed, sequential response function. The first detector alarm will sound local bells and an alert signal at the main and local control panels. The second detector alarm will automatically close all associated fire campers and shutdown room exhaust fans.
The third detector alarm will automatically trip the C02 System and provide local and remote indication that the CO2 System has been activated. Both detection and trip systems are to be electrically supervised including the abort switches. Backup CO2 suppression for the cable vault is actuated directly from a pull station and a directional valve.
Both systems will have a 30 second evacuation time delay and alarm for personnel safety.
In addition, override abort switches will be provided to enable local fire fighting.
Use of these switches will be strictly controlled via fire fighting training and procedures.
We have reviewed the proposed system with particular attention to the location, spacing, number of detectors, and actuation logic. The location of the detectors is reasonable. The detectors are located on the ceiling in a deep beamed area.
There are two detectors per deep beamed area. The system requires three detectors to alarm before actuation of the system occurs. With this logic, the response time for actuation may be too long because of the ceiling obstructions thus allowing a deep seated fire to propagate.
The detection system has the flexibility to provide one, two, or three detectors in the actuation logic. The licensee via telecon on January 14, 1980, indicated the actuation mechanism will be changed to provide two detectors in the actuation logic in place of three detectors.
We find that the design of the gas suppression systems is acceptable.
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! 3.5 Radiological Consequences of Fires (3.2,6)
Our SER noted that the licensee would evaluate the radiological consequenc6s of fires in the radwaste and advanced off-gas building.
By letters dated January 30, 1978 and September 14, 1979, the licensee provided analysis concerning the radiological consequences of fires and proposes special training for fire fighting in the Radwaste and A0G building areas is adequate to assure that personnel will not be unduly exposed to radiation during fire fighting operations in these areas.
We conclude that the radiological effects of a fire cannot be more severe than those the licensee has considered in other accident analysis. The fire protection for this area is acceptable.
_3. 6 ADMINISTRATIVE CONTROLS - (3.2.9)
Our SER ind ated that the licensee agreed to provide a descriptio of his administrative controls for fire protection to the guidelines in NRC's document, " Nuclear Plant Fire Protection Functional Responsibilities, Administrative Controls and Quality Assurance."
By letter of September 13, 1977, the licensee addressed these controls in his Fire Protection Plan. On July 31, 1978, we forwarded the licensee our evaluation of this plan. By letters dated January 30,1978, April 13,1978 August 14, 1978, September 7,1978, October 13, 1978, and September 10, 1979, the licensee provided the requested additional information about their proposed administrative controls. We have evaluated these submittals and find that the licensee complies with our admini-strative control guidelines except for our concerns about: (1) training of fire brigade support personnel; (2) fire brigade drill frequency; (3) controls to be used for untreated wood; (4) the assignment of the Shift Supervisor as the Fire Brigade Leader; and (5) control of ignition sources in safety related areas. These concerns and their evaluations and required resolutions are as described herein.
By letter dated August 14, 1978, the licensee indicates their five man brigade has two levels of training, i.e., three members of the primary fire fighting team will be fully trained whereas the two assigned security personnel will receive only training necessary to perfonn their support roles. We have evaluated this proposal and find that it does not comply with the provisions of the staff position for the training of support personnel assigned to the fire brigade. We will require the licensee to comply with this staff position, " Minimum Fire Brigade Training," as noted in Enclosure No. 2.
By letter dated October 13, 1978, the licensee proposed to provide:
(1) two drills per year for each fire brigade; (2) one drill on the back shift for each brigade and one drill to be unannounced for each brigade; and (3) one drill out of ten, each year with the Town of Vernon Fire Department. By letter dated Septerber 10, 1979, the licensee then proposed a different drill program which concerns only three primary fire fighting team members and the two security support personnel. This program essentially requires that the primary team members will drill two times per year and security personnel would drill two times or less per year. We have evaluated these proposals and we find they do not satisfy the provisions of our guidelines or our July 31, 1978 staff position on this matter and, therefore,
. are not acceptable. To resolve our concerns, we will require that fire drills shall be performed at regular intervals but not to exceed three months for each fire brigade. Each individual member of the fire brigade, including the support personnel, shall participate in at least two drills per year.
At least one drill per year shall be performed on a back shift for each fire brigade. A sufficient number of these drills, not less than one for each fire brigade per year, shall be unannounced.
By letters dated August 14, 1978 and September 10, 1978, the licensee indicates that the Shift Supervisor will be the on-scene Fire Brigade Leader because: (1) in his absence the Supervisory Control Room Operator who is equally qualified is authorized by position and licensee to respond to all normal and emergency conditions,and (2) the Shift Supervisor is most familiar with the plant layout and is frequently outside the control room to investigate any abnomal conditions. We have evaluated the licensee's responses and we find they do not satisfy the provisions of our July 31, 1978 staff positions on this matter and are, therefore, not acceptable. To resolve our concern, we recommend that the 1icensee:
(1) submit a commitment that the Shift Supervisor (s) responsibilitie, for the overall operation and safety of the plant would not conflict, in any way, with the responsibilities of an "on the scene" Fire Brigade Leader during a fire emargency; (2) provide assurance that the Supervisory Control Room operator assigned to supervise the control room in the absence of the Shift Supervisor has equivalent qualifications to the Shift Supervisor and meets the requirements of Section 4.3.1 ANSI /ANS-3.1-1978, "American National Standard for Selection and Training of Nuclear Power Plant Personnel;" and (3) assure an approved procedure is available which clearly defines the Supervisory Control Room Operator's duties and responsibilities in assuming the position of Shift Supervisor during a fire emergency.
The licensee by letter dated September 7,1978, indicates that smoking, welding cutting, griading and open flamework (hotwork) are controlled in accordance with their AP0042 procedure.
This procedure requires a permit and a fire watch for hotwork in certain plant areas with high combustible loading, and only in safety related areas with a significant combustible loading.
The plant fire protection coordinator reviews the exceptions to these controls. We have eval'uated the licensee's response and we find it does'not satisfy the provisions of our July 31, 1978 staff position and is, therefore, not acceptable. To resolve this concern, we will require that administrative controls be prepared and instituted to assure all safety related areas and areas hazardous to safety related equipment are protected from fire damage or loss resulting from work involving ignition sources, guch as welding, cutting, grinding or open flamework.
STAFF POSITION MINIMUM FIRE BRIGADE TRAINING CONCERN During our evaluation of the training given to fire brigade members, the issue of whether all members of a five man fire brigade need be given identical training has been considered.
In several instances licensees have proposed two levels of training for fire brigade members. These evaluations have established the minimum acceptable level of training.
STAFF POSITION We prefer that all fire brigade members receive training in accordance with the staff guidelines set forth in " Nuclear Plant Fire Protection Functional Responsibilities, Administrative Controls and Quality Assurance," June 14, 1977: : Fire Protection Organization :
Fire Brigade Training :
Fire Fighting Procedures Where the five man fire brigade has two levels of training, at least three members shall have training which fully conforms to the staff guidelines; however, two members may be expected from the training requirements listed below:
- 1. :
1.0a (6) The direction and coordination of the fire fighting activities.
1.0a (9)
Detailed review of fire fighting procedures and procedure changes.*
1.0a (10) Review of the latest plant modifications and changes in fire fighting plants.
The excepted personnel should have general training in these subjects.
- The only portion of this item excepted is that associated with the fire fighting strategies which have been developed to conform with, item d.
The strategies established for fighting fires in all safety-related areas and areas presenting a hazard to safety-related equipment.
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