ML20008G255
| ML20008G255 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 06/02/1981 |
| From: | Wells D DETROIT EDISON CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20008G254 | List: |
| References | |
| IEC-78-05, IEC-78-5, NUDOCS 8107070177 | |
| Download: ML20008G255 (1) | |
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I June 2, 1981 U. S.' Nuclear Regulatory Commission Region ill 799 Roosevelt Road Glen Ellyn, IL i
Gentlemen:
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-A review of our files indicates that we do not have a copy of IE Circular No. 78-05, " Inadvertent Safety injection During Cooldown", issued May 23, 1978. We would appreciate receiving a copy of this Circular.
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'6 MAY 2 61978 MEMORANDUM FOR: Those on Attached List Helen Pappas, Chief, Administrative Branch FROM:
SUBJECT:
IE CIRCULAR NO. 78-05 The attached IE Circular No. 78-05 titled " Inadvertent Safety Injection During Cooldown" was sent to the following licensees on May 26, 1978, for information:
American Ele'etric Power Service Corporation Indiana and Michigan Power Company D. C. Cook 1, 2 (50-315, 50-316)
Commonwealth Edison Company Braidwood 1, 2 (50-456, 50-457)
,C Byron 1, 2 (50-454, 50-455)
Zion 1, 2 (50-295, 50-304)
Consumers Power Company Midland 1, 2 (50-329, 50-330)
Palisades (50-255)
Northern States Power Company Prairie Island 1, 2 (50-282, 50-306)
Tyrone Energy ! ark 1 (50-484)
Public Service of Indiana Marble Hill 1, 2 (50-546,.50-547)
Toledo Edison Company Davis-Besse 1 (50-346)
Union Electric Company Callaway 1, 2 (50-483, 50-486)
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2-MAY 261378 Those on Attached List Wisconsin Electric Power Company Point Beach 1, 2 (50-266, 50-301)
Wisconsin Public Service Corporation Kewaunee (50-305)
Helen Pappas, Chief Administrative Eranch Attachments:
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IE Circular No. 78-05 2.
List of IE Circulars Issued in 1978
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U.S. NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT REGION III May 26, 1978 IE Circular No. 78-05 INADVERTEi.'T SAFETY INJECTION DURING COOLDOWN Salem 1, a four-loop Westinghouse PWR, was being cooled from Mode 3 (hot standby) to Mode 5 (cold shutdown) on January 23, 1978. With one reactor cooling pu=p eperating, the atomospheric relief valves on all four steam generators 2.r; used to remove heat from the reactor coolant system. When reactor coolant pressure and average temperature were at 1500 psig and 403 degrees f ahrenheit, an inadvertent safety injection occurred due to low pressure in the steamline from one of the steam generators. Water at 61 degrees f ahrenheit was transferred from the refueling water storage tank te C
the reactor coolant system resulting in thermal shock to the safety injec-tion nozzles. Operator action limited the duration of the safety injection to 2 to 4 1/2 minutes.
The nuclear steam system supplier had inferred the licensee that 50 safety injections using refueling water et 40 degrees fshrenheit would not result in excessive strers at the safety injection nozzle. Because Salem-1 has had an unexpectedly large number of inadvertent safety injections, the licensee is taking action to reduce the frequency with which they occur.
There are a number of contributing factors which lead to inadvertent safety inject' ion when the reactor is being cooled from Mode 3 to Mode 5.
These factors include: (1) operation of a single reactor coolant pump instead of reactor coolant pumps in opposed cooling loops, (2) lack of pressure recording instruments for the steamlines, and (3) use of atmos-pheric relief valves instead of steam dump valves.
The reactor vessel inlet nozzles for the four reactor cooling loops are not equally spaced on the circumference of the reactor vessel. Two pairs of inlet nozzles are located on opposite sides of the vessel. The azimuthal separation between the inlet noczler, of each pair is approxi-mately 45 degrees. With one reactor coolant pump in operation, backflow occurs in the other three cooling loops and is expected to be greatest in the Icop with the nearest adjacent inlet nozzle. Because of the different flow rates in the four cooling loops, the task of controlling the cooling rate in each steam generator is difficult. If the atmospheric relief valves on each steam generator are positioned alike, the cooling rate will
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.NL IE Circular No. 78-05 May 26, 1978 be grcatast in the steam generator receiving the least reactor coolant rflow and thus the least heat. Therefore, the saturation pressure in that steam generator falls more rapidly than in the other steam generators.
When the pressure in any steamline is 100 psi less than the pressure,in any two of the other three steamlines, a safety injection occurs.
So that the flow rates will be more nearly equal in the four reactor cooling loops, the licensee has changed the procedure for coo?ing from Mode 3 to Mode 5.
The revised procedure requires that two reactor coolant pumps in opposing reacter cooling loops be in operation when available.
While cooling from Mode 3 to Mode 5, the Salem-1 operator monitors the pressure in each steamline and adjusts the position of each atmospheric relief valve as necessary to =aintain an equal rate of pressure decrease.
The operator's task is more difficult than necessary because steam genera-tor pressures are indicated but not recorded on the control panel.
The steam generators can also be cooled using the steam dump valves when the condenser is available. The steam dump valves are in stea= lines
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connecting the mixing bottle to the condenser. The mixing bottle is a large dia=eter manifold which receives steam from all four steam generators.
Use of the steam du=p valves and the mixing bottle, instead of the atmos-pheric relief valves, causes heat transfer in each steam generator to be essentially self regulating and to tend to maintain the same pressure in each steamline. For this reason the licensee has changed the procedure for cooling from Mode 3 to Mode 5 to require that the steam du=p valves be used when the condenser is available.
Holders of Operating Licenses for PWRs which have experienced problems with inadvertent safety injections during cooldown and holders of construction permits for PWRs should consider actions which would minimize the frequency of those occurrences.
No written response to this circular is required. If additional information is needed regarding this matter, please contact the Director of your NRC Regional Office.
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IE Circular No. 78-05 May 26, 1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Circular Subject Date Issued To
'of Issue No.
78-01 Loss of Well Logging 4/5/78 All Holders of
.a Well Logging Source Source Licenses 78-02 Proper Lubricating 011 4/20/78 All Holders of for Terry Turbines Reactor Operating Licenses (OL) or Construction Permit (CP) 78-03 Packaging Greater Than 5/12/78 All Holders of Type A Quantities of Reactor Operating Licenses (OL),
C Few Specific Activity Construction Radioactive Material Permits (CP), Fuel for Transport Cycle, Priority I
'terial and Waste Disposal Licenses 78-04 Installation Error That 5/15/78 All Holder of an NRC Could Prevent Closing of Operating License (OL) or Construction Fire Doors Permit (CP) i Enclosure Page 1 of 1 l
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