ML19345B549
| ML19345B549 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 10/29/1980 |
| From: | Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19345B548 | List: |
| References | |
| 870, NUDOCS 8012010607 | |
| Download: ML19345B549 (12) | |
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l VINGINIA ELucTurc Asp Powen Comssy H acnwows),VznorN EA 20265 October 29, 1980 Mr. Robert L. Tedesco Serial No. 870 Assistant Director for Licensing NAPS /JWO:rab Division of Licensing Docket Nos. 50-3:,3 U. S. Nuclear Regulatory Commission 50-339 Washington, D. C.
20555 License Nos. NPF-4 NPF-7
Dear Mr. Tedesco:
We have evaluated the results of your review cf the Emergency Action Levels of Section 4 of the North Anna Power Station Emergency Plan, as contained in your letter of August 4, 1980. Our responses to your comments are enclosed, as is a revision to the plan which resulted f rom your comments.
Sincerely,
../
B. R. Sy ia Manager, Nuclear Operations and Maintenance
Enclosures:
Vepco Response to NRC Review of North Anna Emergency Plan Emergency Actica Levels Revised North Anna Emergency Plan Table 4.1. dated 10-24-80 C30E'E ?? I71,Ci' IDF on."A;;p3 D
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General Emergency Category Initiating Condition No.2 (Loss of 2 of 3 fission product barriers with a potential loss of the 3rd barrier)
NRC Comment Initiating Condition 2 is the loss of 2 of the 3 fission product barriers with a potential loss of the third barrier.
The emergency action level for this condition only considers 1 of the 3 possible ways in which 2 of the 3 fission product barriers may be lost. The plan considers the case where the fuel has been breached and the integrity of the reactor coolant system has been compromised.
Not mentioned are the accidents where:
(1) the fuel has been breached and the e
containment has faihd to isolate; or (2) when the reactor coolant system has lost its integrity and the containment has failed to isolate.
The emergency action levels which are given are vague. The terms " confirmed loss" or "high potential" do not constitute fixed observable conditions. The loss of fuel cladding integrity can be indicated by in-core temperatures, containment building radiation levels, reactor coolant system radioactivity levels, pressure vessel water level, or by the process radiation monitors.
The integrity of the reactor coolant system can be determined from the pressure vessel water level, the pressurizer water level, the pressurizer pressure, and the containment pressure. The potential for a loss of the third barrier can be indicated by a loss of offsite power, a loss of the emergency core cooling systems, or a system which har approached its designed pressure limits and which is tending the exceed those limits. For example, a containment building pressure of 40 or 50 psig, and a steadily rising containment building pressure ma: ---- H e n t e a suitable emergency action level.
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-VEPCO Response i
We agree with your comment and have revised the plan accordingly.
Site Emergency Category Initiating Condition No. 1 (Known major loss of coolant accident)
VRC Comment Initiating Condition 1 is a major loss of coolant accident. North Anna correctly interprets this as an accident which can be identified by monitoring the containment pressure and the pressurizer pressure. The pressurizer level, the coolant level in the pressure vessel, and the temperature difference between the inlet and outlet of the pressure vessel may also be used as emergency action levels. However, the North Anna plan states that the signals must not
's be spurious.
The licensee should either increase the reliability of the emergency action
- f levels which are used or the licensee should state which corroborating signals would be used to determine whether the emergency action levels are or are not spurious.
VEPCO Response In choosing the indications for a major loss of coolant accident it was felt that a safety injection caused by either high containment pressure or low-low pressurizer pressure was the most indicative of this condition, since it is the protective feature designed to mitigate this accident. Pressurizer level was not used as it was recently removed as one of the initiating signals for safety injection as a result of the lessons learned from TMI. Reactor vessel level is not used as it is not presently indicated. Temperature difference between the inlet and outlet of the reactor vessel is not felt to be a positive indication of this accident. The statement concerning spurious signals is l
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VEPCO Response (cont.)
intended to prevent declaring a Site Emergency when no emergency condition exists simply because a spurious SI has been initiated.
For example, a spurious SI might be caused by an error on the part of an instrument technician during the performance of a periodic test. This type of spurious SI sheuld not require the declaration of a Site Emergency and the Shift Supervisor can easily determine that the signals were spurious by checking the associated meter indication for the actuating signals. Therefore, we feel that no change is warranted.
Initiating Condition No. 2 (Loss of core subcooling)
NRC Comment s
Initiating Condition 2 is a loss of core subcooling. The emergency action level is a subcooling margin of 0* F or less. This margin is not very large.
a It is recommended that the margin should be increased with a simultaneous indication of decreasing saturation margin. Corroborating emergency action
,clevels could be high reactor building pressure or high reactor coolant activity.
VEPCO Reponse This condition is intended to correspond to a degraded core with possible loss of coelable geometry as listed in NuReg-0610. High containment pressure will not result from this condition alone and, therefore, should not be used as a corroborating indication. High coolant activity could be used as a corroborating indication, but IL ielt that loss of subcooling alone is sufficient indication of a high probability of degraded core with possible loss of coolable gemoetry.
A 0*F subcooling margin is used since a greater margin would not be indicative of a high probability of a loss of coolable geometry. Therefore, we do not feel a change to this condition is warranted.
Initiating Condition No.4 (Steam line break with significant primary to secondary leakage and indication of fuel damage)
NRC Comment initiating Condition 4 is a main steam line break with significant primary-to-secondary leakage and indication of fuel damage. The emergency action levels for identifying significant main steam line breaks and primary-to-secondary leakage are adequate. However, the indications of fuel damage are not adequate in that North Anna relies solely on indications of specific activities in the coolant. Under conditions of stagnate flow or subcooling (presence of voids in the primary system) such an emergency action level would not be adequate.
(See the discussion under the general eme,rgency category).
VEPCO Response We agree with your comments and have added high core temperature as an indication of fuel damage.
Initiating Condition No. 7 (Loss of all functions needed to take the unit to hot shutdown)
NRC Comment Initiating Condition 7 is a loss of all functions needed to take the unit to hot shutdown. The licensee response is that this condition would occur if all the following systems were lost:
auxiliary feedwater system boric acid transfer, pressurizer heaters, atmosphere steam dump, charging pumps, and letdown isolation valves.
It is recommended that pressurizer heaters be deleted from this list of systems, since a loss of the other 5 systems would be significant enough to warrant classification of a site emergency.
VEPC0 Response We agree with your comment and have removed pressurizer heaters from the list.
Initiating Condition No. 8 (Major damage to spent fuel in the containment or fuel building)
NRC Comment Initiating Condition S is major damage to spent fuel in a containment or fuel building. The emergency action level' is based upon the weight of an object i
i which impacts the spent fuel. The weight of this object is not measureable in a control room. The licensee should refer to the emergency action levels which are based upon radiation indications in the alert and unusual event categories. The use of reactor vessel water level as an emergency action
_ level for this initiating condition should be consistent with other initiating conditions which relate to fuel damage.
VEPC0 Response r
We agree with you comment concerning the weight of the object and have changed e
the indication to one based on radioactivity levels. However, we have retained the water level indication since this is a valid indication during refueling operations or in the spent fuel pit and is, in fact, referenced as an indication in NuReg-0610.
Initiating Condition No. 10 (Loss of all annunciators for more than 15 minutes with the unit not shutdown or with a unit transient occurring while the annunciators are lost)
NRC Comment Initiating Condition 10 is a loss of all annunciators for more than 15 minutes or loss of annunciators during a transient. North Anna has not addressed the second condition. The loss of annunciators during a transient has not been assigned an emergency action level.
It is suggested that the emergency action level be rewritten to state:
" Annunciators panels a - k are all inoperable l
for more than 15 minutes or during a declared emergency."
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i VEPC0 Response The indication, as presently written, as as follows:
" Annunciator Panels A thru K are all inoperable for more than 15 minutes
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with unit not shutdown or, in the judgment of the Shif t Supervisor, a transient is occurring on the unit."
This statement does cover a transient condition and we;do not feel a change is warranted.
Initiating Condition No. 11 (Projected doses at the site boundary of from 0.5 i
Rem to 2 Rem whole body exposure or 1 Rem to 12 Rem thyroid exposure):
NRC Comment Initiating Condition 11 is a projected wh, ole body dose at the site boundary of 0.5 to 2 rem.
The emergency action levels do not indicate that estimates of leakage from the containment would be used to project doses at the site boundary.
The emergency actica levels should be augmented to include an action level or a set of conditions determined by a containment area radiation monitor.
VEPCO Response The examples of initiating conditions for site emergencies gi' en in NrReg-0610 has the following example:
"These dose rates are projected based on other plant parameters (e.g.,
radiation level in containment with let**. rate appropriate for existing containment pressure) or are measured in the environs."
Since we operate a subatmospheric containment, we would expect no outleakage unless we had an elevated containment pressure caused by either a loss of f
coolant accident or a secondary line break in the containment, and this second accident would have to involve significant primary to secondary leakage to l
pose any threat of release.
Both of these accidents require declaration of a l
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L VEPCO Response (cont.)
Site Emergency which will result in monitoring teams being immediately dispatched to the site boundary.
It is our feeling that the readings obtained by t*.ase teams are a much better indication than a dose projection based on a containment pressure, an assumed leak rate and a radiation level reading. Therefore, since NuReg-0610 offers the option of projected dose rates or actual measurements, we do not feel a change is warranted.
Initiating Condition No. 15 (Evacuation of the Control Room where control of the shutdown systems is not established within 15 minutes)
NRC Comment Initiating Condition 15 is an evacuation,of the control room where control of the shutdown systems is not established within 15 minutes. The licensee identifies the safety systems which must be brought under control within 15 minutes, however, there is no stated means of verifying that the systems are in fact under control.
It is difficult to understand how the license could detect a lack of control in these systems from an onsite location.
VEPCO Response The controls for all the systems listed, as well as indications of associated system parameters, are located on the Auxiliary Shutdown Panel which is located outside the Control Room and would be manned upon evacuation of the Control Room. This panel is specifically designed to allow the operator to place the unit in hot shutdown and maintain it in this mode when the Control Room is inaccessible. Established procedures guide the operator in the operation of this panel and these systems during this condition and it should be readily apparent whether-control of these systems has been established. Therefore, we do not feel a change is warranted.
m A
t Alert Category Initiating Condition No. 1 (Severe loss of fuel cladding)
NRC Comment l
Initiating Condition 1 is a severe loss of fuel cladding integrity. The emergency action level is 300 microcuries per gram of reactor coolant dose equivalent iodine-131, as determined by sampling and analysis. A specification of allowable concentrations of iodine-132, iodine-133, or iodine-135 may be more appropriate. The simpler analysis indicated in the emergency action level could be appropriate for a remote measuring device.
The specification of sampling and analysis implies that the power plant's radioanalytical capabi-lities should be adequate to perform an i,sotopic analysis of radioiodine. The i
shorter lived radioiodine isotopes are better indicators of fuel damage than iodine-131.
In addition, high core temperature, low pressure vessel water
- . P level, or high containment building radioactivity levels may constitute accept-able emergency action levels.
i VEPCO Response The use of dose equivalent I-131 determines the concentration of I-132, I-133 and I-135 and then converts them to an I-131 equivalency.
This technique is standard in the nuclear industry and is the technique specified in the North Anna Technical Specifications for specific activity. Therefore, we do not feel a change in sampling technique is warranted.
In addition, we do not feel that the use of reactor vesse1~ water level or high containment radioactivity levels are appropriate since we presently have no means of monitoring reactor
~
vessel water level and since loss of fuel cladding will not result in high containment radioactivity levels unless there is a loss of reactor coolant system intergrity. We do agree that high core temperature may be indicative of fuel clad failure and, therefore, have added this indication.
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Initiating Condition No.9 (Reactor coolant pump locked rotor at power leading to fuel fiflure)
NRC Comment Initiating Condition 9 is a locked rotor in a reactor coolant pump leading to fuel failure. See ptevious comments relating to a reliance on reactor coolant specific activity as an emergency action level for fuel failure.
t VEPCO Response The results of the accident analysis for this accident indicate that no loss of primary coolant system integrity or core geometry will result, even under the worst case assumptions. Therefore, no major release of radio-activity to the containment or the environment can be expected to occur and the only reliable indication of fuel damage would be reactor coolant activity levels. For this reason, we do not feel that a change to this condition is warranted.
Initiating Condition No.10 (Failure of the reactor protection system to initiate and complete a trip when required)
NRC Comment Initiating Condition 10 is a failure of the reactor protection system to initiate and complete a scram when required. The licensee relies upon "no rod bottom lights" to detect a failure of control rods to fully insert. The licensee should also use indications of neutron fle.< or rate of change of neutron flux (reacror period) as emergency action lavels.
VEPC0 Response While the absence of rod bottom lights has historically been used as an indication of a failure to trip, we agree that absence of a neutron flux decrease is also indicative of a failure to trip and have revised the indications to include tais.
Initiating Condition "o.
11 (Fuel damage accident with release of radioactivity to the containment or fuel building):
NRC Comment Initiating Condition 11 is a fuel damage accident with release of radioactivity to the containment or fuel building. The emergency action level does not specify whether a " release of fission products" refers to a release from the fuel bundle or a release from the site. This emergency action ievel might be rewritten to specify a confirmation of the presence of fission products released from the fuel.
VEPCO Response The indications have oeen changed to more, clearly indicate that the release of fission products is from the fuel.
Notification of Unusual Event Category Initiating Condition No. 3 (Fuel damage indicated)
NRC Comment Initiating Condition 3 is an indication of fuel damge.
(See the previous comments concerning the use of reactor coolant activity as the sole indicator of fuel damage.)
VEPCO Response The assumption for this condition is that minor fuel damage has occurred, but l
l that no potential for releases exceeding the 10 CFR 100 limits at the site l
boundary exists unless further degradation of safety systems occurs.
(See l
NuReg-0610 and Tech Spec Bases.)
In this case the only real indicatins of fuel damage available are primary coolant specific activity and Reactor Coolant High Range Letdown Monitor readings, since other indications such as high core temperature or high containment radioactivity levels should not be prasent for -
l VEPCO Response (cont.)
this condition.
If they are present, other conditions are indicated, requiring classification as an Alert or Site Emergency, depending on the indications present. Therefore, we do not feel that any change to this indication is warrana.ed.
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