ML19289E969
| ML19289E969 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/26/1979 |
| From: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| NUDOCS 7905290712 | |
| Download: ML19289E969 (11) | |
Text
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Tif474 B ALTIMORE G AS AND ELECTRIC COMPANY P.O. B O X 14 7 5 B ALTIM O R E. M A RYL A N D 212OJ ARTHUR E. LUN OVALL,J R.
VeCE Pat teotest
- Swees, April 26,1979 U. S. Nuclear Regulatory Commission Docket Nos. 50-317 Division of Inspection and Enforcement 50-318 Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention: Mr. Boyce H. Grier, Director Gentlemen:
The attached information is provided per the reouest of IE Bulletin 7B AB.
Regarding items 2, 6 and 11 of this Bulletin, we are presently working with our Nuclear Steam Supply System supplier (Combustion Enaineering, Inc.) to complete a review of the procedural and/or design aspects of these items as they apply to the Calvert Cliffs plants, the intention being to prevent or mitigate the possibility and consecuences of void formation.in the Reactor Coolant System similar to that which evidently occurred durina the Three Mile Island Unit 2 incident.
It is expected that the initial phase of this review will be completed by April 30, 1979 and that any procedural changes which result from this review will be implemented by May 4, 1979. We intend to supolement the infomation orovided herein, as new and tstter information is derived and further analyses are completed.
Should you have further questions regarding this natter, we would be pleased to discuss them with you.
Very truly yo
/
. E.'Lundv 17, Jr.
Vice President - Supply AEi./ RED /dds Attachments 79052907(1 t v xY3
, n,.,
205 330
-Page Two-Copies To:
J. A. Biddison, Esouire G. F. Trowbridge, Esquire E. L. Conner, Jr,, NRC Office of Inspection and Enforcement, NRC R. Sanacore, /merican fluclear Insurers
^95' 331
RESPONSE TO IE BULLETIN 79-06B 1
ITEM 1 A detailed briefing regarding the Three Mile Island Unit 2 incident was given at our site by representatives of the NRC Divisions of Inspection and Enforcement and Operator Licesing on April 19, 1979.
It is our understanding that this briefing meets the requirements of this bulletin item.
ITEM 2 Please see accomoanying cover letter.
ITEM 3 The containment isolation (CIS) initiation and safety injection (SIAS) initiation are described in FSAR Chapter 7, Figures 7-10, Sheets 1 and 2.
CIS is initiated by high containment pressure with the setotint at a measured 4.25 PSIG.
SIAS is initiated by hiah containment pressure with the setpoint at a measured 4.25 PSIG or low pressurizer pressure.
CIS is not automatte.311y initiated by SIAS, but both will occur sinultan-eously on high containment pressure.
In order to more precisely ensure the retention of radioactive gases 2nd liouids within the Containment buildino, a steo has been added to the applicable plant emeraency procedure (EOP-5, Loss of Reactor Coolant) requiring that the following containment penetrations be isolated by the Control Room Goerator from the Control Room upon the receipt of automatic safety injection initiation.
1.
Containment Purge (inlet and outlet) 2.
Reactor Coolant Drain Tank Pump 3.
Waste Gas System 4.
Containment Atmosphere Sanole 5.
Containment Nonnal Sump 6.
Peactor Coolant Samole 7.
Containment Heating Water 8.
Steam Generator Blowdown A design review is now in progress to determine the feasibility and rossible advantages of incorocrating an automatic feature to initiate the isolations described above upon safety injection initiation.
.y
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RESPONSE TO IE BULLETIN 79-06B 2
ITEM 4 Even though the present Technical Specifications only require the presence of one licensed operator per unit in the Control Room, it has been the practice of plant management to augment this staffing with an extra licensed person per unit when the unit is at power operation.
It is the function of this extra person (designated the " Reactor Operator") to ensure the most economical operation of the unit by the devotion of his primary attention to the manipulation of the control rods, the boration/
dilution controls and the Turbine controls to optimize core / unit outout.
In order to respond to the requirements of this bulletin iten, the Nuclear Plant Engineer-Ocerations has directed by means of his " Standing Instruct-ions" that upon the receipt of a plant trip, the Reactor Operator, having no further responsibilities for reactivity control, shall irmediately direct his sole attention to the maintenance and/or restoration of feed-water flow via the main feed pumps or auxiliary feed pumps as required by the situation. All other Control Room functions for the affected unit are to be carried out by the Control Roon Operator and the Senior Control Room Operator.
In the event the mannino level of the Control Roon is altered such that a
" Reactor Operator" is not available for each unit, a person specifically trained in the operation of the auxiliary feedwater system will be made available to assume these duties.
A design review is in progress to determine the feasibility and possible advantages of incorporating a feature to automatically initiate auxiliary feed flow.
ITEM 5 A chance was entered into the plant emergency procedure for loss of reactor coolant on April 14, 1979, to identify specific indications to be used in identifying an open PORV and to direct that the aoprooriate block valve be closed should one of the PORV's remain stuck open.
ITEM t, Please see accompanying cover letter.
'052 276-m y 333
RESPONSE TO IE BULLET C 79-06B 3
ITEM 7 Our review of all safety-related valve positions, positioning recuirements and nositive controls to assure that they remain positioned in a manner to ensure proper operation of engineered safety features (ESF) included these safety-related valves in the following systems:
Safety Injection Containment Cooling Containment Penetration Room Ventilation System Containment Iodine Removal Auxiliary Feedpump Room Cooling Hydrogen Purge Auxiliary Feedwater Support Systems:
Component Cooling, Service Water, and Salt Water Our review concluded that all of these safety-related valve positions (normal line-uo), positioning requirements (nosition on esc actuation),
and positive controls (position assumed on loss of power and locked valve line-up as described in more detail below) do assure that the valves remain oositioned in a manner to ensure procer operation of ESF.
Various sections of the Technical Snt cifications (as noted below) require that surveillance he nerformed to assire the correct ncsitioning of valves in systems important to safety. Thes1 systems and the related Technical Specifications sections are:
SYSTEM TECHNICAL SPECIFICATIONS SECTION Chemical Volume Control (Boration) 4.1.2.1.b and 4.1.2.2.b ECCS Subsystems 4.5.2.b.2 Auxiliary Feedwater 4.7.1.2.a.2 Component Coolino 4.7.3.1.a Service Water 4.7.4.1.a Salt Water 4.7.5.1.a Specifically, the Technical Specifications require that valves in these systems which are not " locked, sealed or otherwise secured" in position be verified to be in the correct position monthly.
In imnlementina these surveillance requirerents, each system was reviewed and all valves in those systens for which misalignment could adversely affect system operation where noted (vents and drains on normally filled, pressurized systems are not included, since their mispositioning would be immediately apparent; likewise, instrument stop valves are not included since the associated instruments are checked during routine surveillance and cali-bration).
Control Valves, Motor Operated Valves, and Solenoid Valves g rg _ 2.7 7 T95" 334
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RESPONSE TO IE BULLETIN 79-06B 4
which have indication in the Control Room are monitored in a Surveill-ance Test Procedure perfomed monthly (as reauired by the Technical Specifications). Other (manual) valves are listed in a " Locked Valve List" associated with the " Pre-Startup Checkoff" procedure. These valves are aligned to the positions reauf red by this list prior to enterina the operational mode for which the system is required and they are secured in position with a chain clipped tocetbr at the ends, as described in FSAR Section 12.3. Additionally, each of these valves is marked with a color-coded tag, desionating its nomal position to be.
open or closed. Wher.ever the plant is in a mode of oneration other than
" cold shutdown" or " refueling", these valves are controlled by a " locked valve deviation log" kept by the Senior Control Room Operator. That is, the repositioning of any of these valves is recorded in the log and maintainea as outstanding until it is returned to its normal position, when it is cleared from the log.
In the event maintenance is being perfomed which requires the isolation of fluid systems for personnel or equipment safety purnoses, a " Safety Tagging" orocedure is used which identified each vah/e involved in the isolation scheme. These valves are " tanged" in the isolated positicn as authorized by the Shift Suoervisor and each valve is listed in the master log kept by the " Tagging Authority". After completion of the maintenance, this tagging list is used to aid in repositioning the affected valves.
As a result of reviewing the Three Mile Island Incident and in response to this bulletin, the following actions have been taken with resoect to the control of the positionina of valves in systems covered by the afore-mentioned Technical Specifications:
1.
The importance of the precise control of the " locked valve deviation log" has been emphasized to all Control Pool and Senior Licensed Operations personnel. All deviations from the " Locked Valse List" whether it be for testing, maintenance, or operational pu5 poses, shall be noted in this log.
2.
The femal review of the current status of this loa will be reauired as a shift turnover item for the Senior Control Room Operator.
3.
In addition to the requirements of the Technical Specifications that a monthly check be perfomed of valves which are not " locked, sealed, or otherwise secured in position", the Nuclear Plant Engineer-Ooerations has directed that a check of the locked valve list be oerfomed (in accessible areas of the plant) on a monthly basis.
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RESPONSE TO IE BULLETIN 79-068 5
^
ITEM 8 The containment 1 solation system (CIS) is designed to prevent the release of any potentially radioactive fluids or gases from the containment follow-ing an accident. The closure of the isolation valves effectively seals all flow paths from the containment. To open an isolation valve following automatic closure by the containment isolation system the initiating para-meter must have cleared, the operator must manually reset the isolation signal, and position the valve handswitch to open.
Containment isolation signals cannot be blocked before or after initiation and there are no process control systems which will automatically open a contair. ment iso-lation system valve. Once the containment isolation system is initiated the operators cannot override, therefore, inadvertent transfer of radio-active fluids and/or gases will not occur during an incident. Upon CIS initiation, the position of all handswitches associated with cont'ainment isolation system valves are placed in the position corresponding to the valve isolation position. This ensures that inadvertent transfer of radioactive fluid and/or gases will not occur when the containment isolation systen is reset.
The one exceotion to the override critoria stated above is the ability to override the containment isolation sicnal' (CIS) for the instrument air system containment isolation motor operated valve.
This override is providad to supplement the air accumulator system inside containment, for boron orecipitation control, followina an incident if the instrument air system outside containment is available.
Since the nonnal system flow is into containment with a check valve provided at the penetration, the potential to transfer radioactive gases out of contain-ment is not credible. Administrative control and nrocedures are provided to assure that this key operated handswitch override is not inadvertently utilized.
The following systems are nonnally isolated but may be required fellowing an incident:
1.
Containment Sumo Recirculation.
Normally closed and is then opened on low refueling water tank level to facilitate SI recirculation.
2.
Gas Analyzing System (Hydrogen /0rfgen).
Locked closed.
3.
Hydrogen Purge System. Locked closed.
4.
Shutdown Cooling System. Locked clo nd.
The systems and flowpaths listed below are normally used to transfer fluids or cases out of containment and receive an automatic Containment Isolation Signal (CIS). Containment isolation is upon high containment pressure. Containment purge isolation is also initiated uoon high con-tainment radiation.
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RESPONSE TO IE BULLETIN 79-068 6
1.
Containment Purge System The containment purce system is isolated on hich containment pressure (CIS) or hich containment radiation (CRS).
Both conditions must be cleared and reset, as described above, to coerate the system. Containment ourge operations are restricted in accordance with Mr. R. W. Reid'c (NRC) letter of November 29, 1978 and our resoonse of January 12, 1979.
2.
Letdown Line to the Chemical and Volume Control System.
Isolated by CIS.
3.
Containment Nonnal Sump to Miscellaneous Waste Processing System.
Isolated by CIS.
4.
Reactor Coolant Drain Tank to Reactor Coolant Haste Processing System.
Isolated by CIS.
5.
Reactor Coolant Sampling System.
Isolated by CIS.
6.
Reactor Coolant Pump Controlled Bleedoff.
Isolated by CIS.
7.
Reactor Coolant Drain Tank and Pressurizer Ouench Tank Vent.
Iso-lated by CIS.
The inability to block or override isolation signals, the reset criteria, the unavdilability of process control system overrides, the established administrative controls and procedures, and the inherent fail-safe design of CIS assures the continued operability of the isolation system.
ITEM 9 Whenever any safety-related systen is removed from service, such an action must be exolicity aoproved by the Shift Supervisor.
In the case of a maintenance action, the Shift Supervisor must authorize the tag-out or renoval of the system from service; in the case of surveillance test-ing, the Shift Supervisor must authorize the test to be performed.
In either event, the operability of redundant safety-related equionent is checked by the Shift Sunervisor before his authorization is civen. Gen-erally, this check is to verify that the redundant train is not out of service due to a tag-out or other testino; the assumption being that routine surveillance testino on the redundant eaufpnent oer the reouire-ments of the Technical Specifications serves as oroof of coerability.
When certain pieces of equipment are removed from service or certain alterations in equipment line-ups are performed, the operability of
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RESPONSE TO IE BULLETIN 79-06B 7
redundant equipment is assured by actual testing and/or line-up verifi-cation as required by the Technical Soecifications (for example, the alteration of a diesel generator or Class IE Power Supply Line-Ups).
When equinment is returned to service after maintenance, it is the responsibility of the Senior Control Room Operator (SCRO) to verify the restoration of the equipment to service. This action is formally acknowledaed on the Maintenance Request; any post-maintenance testing perfomed is also noted on the Maintenance Request before it is signed as completed by the SCR0.
Upon completion of surveillance testing, the Shift Supervisor,must be infomed that the test has been completed and at that time take the steps necessary to return the system to nomal. Any out of specification conditions observed during the test are noted by the Shift Supervisor for his action as necessary to ensure the operability requirements of the Technical Specifications are met.
ITEM 10 Our best interpretation of the reauirements of item 10 leads us to believe that the NRC desires a new cateqory of reportinc in advance of reports made in conjunction with the implementation of our Site Emergency Plan. Our present reporting reouirement, associated with this plan, reouires our Site Emergency Director or Emergency Coordinator to contact the Recion I office after the declaration of a " Site" or
" General" Emergency.
Evidently, in view of the Three Mile Island (TMI) incident, this report is not considered to provide the necessary warn-ing desired by the NRC.
In order to provide an earlier notice of the
.... reactor not (beino) in a controlled or expected condition of operation", we have adopted a policy of reporting within one hour any plant condition which reauires the automatic or manual initiation of the ECCS systen. Based on the scenario provided for the TMI incident, where ECCS initiated in two minutes, we feel this criteria should satisfy any advance warning desire the NRC has.
It is our understanding, based on conversations with out Project Insoector (Mr. D. F. Johnson, of Region I), that the " continuous comunications channel" referred to in this item of the bulletin would be satisfied by a telenhone " hot line" between the olant and Reaion I headouarters. How-ever, due to uncertainty as to the exact arrangements desired by the Comission, it is requested that this matter be clarified in return correspondence.
Until such tire as this is clarified, reports will be made to the Region I headquarters (phone number, 215-337-5000).
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RESPONSE TO IE BULLETIN 79-06B 8
ITEM 11 In the event of hydrogen accumulation in the containment one (1) of two (2) independent electric hydrogen recombiners will be utilized as the crimary means of hydrocen control. The recombination of free hydrogen and oxygen is accomplished by heating the air to the reaction tcmoerature for the recombination of hydrogen and oxygen.
Each recombiner is designed to indeoendently maintain the hydrogen concentration inside the contain-ment below 4 volume percent.
All materials used in the recombiners are compatible with the environmental conditions inside the reactor contain-ment during nomal operation and following an incident. All comnonents are capable of maintaining all nomal loads as well as incident loads, including seismic loads and temperature and pressure transients from a LOCI.
Each reconbiner system consists of a control panel, located in the Control Room, a power cabinet located in the auxiliary building, and a recombiner located on the operating deck of the containment.
There are no moving parts or controls inside the containment. The recombiner is a comoletely passive device, air flow thru the unit is by natural convection. There is no need for cooling water or any other plant service other than electrical power. The recombiners are located on opposite sides of the containment, outside the secondary shield wall, to minimize the orobability of missile or water jet impingement. Each recombiner systen is completely isolated from and independent of the other recombiner system.
The electrical power for each recombiner is supplied from separate, redundant, emergency 480 volt load centers.
The control panel contains all necessary instrumentation to operate, monitor and test the recombiners.
Proper recombiner operation after an incident is determined by monitoring at the control panel, the electric power supplied to the recombiner.
For equipment test and periodic checkout thentocounles with readout at the control panel are provided for monitoring temperatures in the recombiner.
These thennocouples are not necessary to assure proper operation. Based on the recombiners cualification, and location of the controls and oower eouiement, the hydmgen recombiners may be placed in operation at any time as reouired by procedures. Operation of the recombiners is governed by administrative contml and pmcedures.
The containment hydrogen portion of the gas analyzing system is used to determine the hydrogen concentration of six points inside the contain-ment.
The cas analyzing system is installed in the sample room located in the Auxiliary BuiTding.
Each hydroqen panel contains one hydrogen analyzer, one nultiocint recorder for recording each measured sample, one progranmer for sequential and/or random selection of individual readout, and alarm contacts for activation of a master alarm in the Control Room.
The containment hydrogen samole lines are isolated durino normal olant operation.
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RESPONSE TO IE BULLETIN 79-06B 9
The hydrogen monitoring equipment is desianed to monitor the containment atmosphere under incident conditions. Operation of the system is governed by administrative control and procedures. The following areas in each containment are monitored:
Samole Points 1.
Containment - North of Primary Shield 2.
Containment - South of Primary Shield 3.
Containment - Pressurizer Comoartment 4.
Containment - East at Elevation 135 5.
Containment - West at Elevation 135 6.
Containment Dome at Elevation 189 Sections 6.8 and 14.9 of the FSAR describe in detail the provisions made at Calvert Cliffs to control hydrogen accumulation in the Containment following a " maximum hypothetical accident". As stated therein, opera-tion of the electric recombiners would be init'ated twenty-four hours after the accident, thereby liniting hydrogen concentrations to 2.1 volume cercent, well below the flammability limit set forth by Safety Guide 7.
The nresent means for removal of hydrogen from the Reactor Coolant System (RCS) consists of " degassing" the letdown stream via the Volume Control Tank.
It is expected that this procedure could effectively be used ir a cost-accident situation. As stated in the accompanying cover letter, we are presently being assisted by our NSSS supplier in further review of post-accident RCS hydrogen generation and removal; design and/or procedure changes which result from this review will be imnlemented accordingly.
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