JPH0579160B2 - - Google Patents
Info
- Publication number
- JPH0579160B2 JPH0579160B2 JP61043134A JP4313486A JPH0579160B2 JP H0579160 B2 JPH0579160 B2 JP H0579160B2 JP 61043134 A JP61043134 A JP 61043134A JP 4313486 A JP4313486 A JP 4313486A JP H0579160 B2 JPH0579160 B2 JP H0579160B2
- Authority
- JP
- Japan
- Prior art keywords
- water level
- pressurizer
- flow rate
- primary coolant
- full
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 113
- 239000002826 coolant Substances 0.000 claims description 37
- 238000000605 extraction Methods 0.000 claims description 13
- 239000012071 phase Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000008602 contraction Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
Landscapes
- Massaging Devices (AREA)
- Control Of Non-Electrical Variables (AREA)
- Control For Baths (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は、加圧水型原子力発電所の加圧器に適
用される加圧器の水位制御装置に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water level control device for a pressurizer applied to a pressurizer of a pressurized water nuclear power plant.
［従来の技術］
加圧水型原子炉の１次冷却材循環系に含まれる
加圧器は、通常運転中、容積の約60％が液相で他
は気相を構成しており、その１次冷却材循環系の
運転圧力を一定に保持し通常の負荷変化に伴う１
次冷却材の熱膨張および収縮による圧力変化を許
容範囲内に制限するとともに、いかなる場合でも
最高使用圧力を越えないように制御されている。[Prior art] During normal operation, approximately 60% of the volume of the pressurizer included in the primary coolant circulation system of a pressurized water reactor is in the liquid phase and the rest is in the gas phase. 1. Maintaining the operating pressure of the material circulation system constant and responding to normal load changes.
Pressure changes due to thermal expansion and contraction of the secondary coolant are limited within an allowable range, and are controlled so as not to exceed the maximum working pressure under any circumstances.
ところで、加圧水型原子力発電所の停止過程に
おいては、加圧器を通常水位から満水水位までも
つていく操作を行うが、この操作は運転員が手動
によつて行われている。この場合、加圧水型原子
力原子力発電所では、１次冷却材循環系内の１次
冷却材の量を制御するため１次冷却材の充填ライ
ンと抽出ラインが接続されているが、この加圧器
の満水操作は、充填ラインからの１次冷却材の充
填流量を増加させて水位を上昇させている。 By the way, during the shutdown process of a pressurized water nuclear power plant, the pressurizer is moved from the normal water level to the full water level, and this operation is performed manually by the operator. In this case, in pressurized water nuclear power plants, the primary coolant filling line and extraction line are connected to control the amount of primary coolant in the primary coolant circulation system; The full water operation increases the filling flow rate of the primary coolant from the filling line to raise the water level.
［発明が解決しようとする課題］
ところが、この加圧器満水操作では、満水とな
る時点で加圧器水位上昇率が高い場合、加圧器の
圧力が急上昇してしまう。これは第３図ａ，ｂに
示すように満水水位L0の前では加圧器上部に気
相があり、圧力変動は小さいが、満水となつて気
相が削減した時点taでは加圧器は１次冷却材のみ
の単相となる。従つて、この満水の時点taで１次
冷却材を加圧器に送ると、加圧器内の圧力は急上
昇してしまう。[Problems to be Solved by the Invention] However, in this pressurizer filling operation, if the pressurizer water level rise rate is high when the pressurizer is filled with water, the pressure in the pressurizer will rise rapidly. This is because, as shown in Figure 3 a and b, before the full water level L 0 , there is a gas phase at the top of the pressurizer and the pressure fluctuation is small, but at the time ta when the water is full and the gas phase is reduced, the pressurizer is at 1 It becomes a single phase with only secondary coolant. Therefore, if the primary coolant is sent to the pressurizer at the time ta when the water is full, the pressure inside the pressurizer will rise rapidly.
そこで本発明は加圧器満水操作を自動化し、か
つ満水時における加圧器の圧力急上昇を防止でき
る加圧器の水位制御装置を提供することを目的と
する。 SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a water level control device for a pressurizer that can automate the filling operation of the pressurizer and prevent a sudden increase in the pressure of the pressurizer when the pressurizer is filled with water.
［課題を解決するための手段］
本発明は上記問題点を解決し目的を達成するた
めに次のような手段を講じたことを特徴としてい
る。すなわち、１次冷却材循環系を流れる１次冷
却材の温度、この１次冷却材の充填流量および抽
出流量を受けて前記加圧器における水位を推定す
る水位推定手段と、この水位推定手段により推定
された推定水位と満水水位とから満水時の水位変
化率を零にする推定水位と満水水位との差に比例
した充填流量制御信号を求める充填流量演算手段
とを具備したことを特徴としている。[Means for Solving the Problems] The present invention is characterized by taking the following measures in order to solve the above problems and achieve the objects. That is, water level estimating means estimates the water level in the pressurizer based on the temperature of the primary coolant flowing through the primary coolant circulation system, the filling flow rate and the extraction flow rate of this primary coolant, and the water level estimating means estimates the water level in the pressurizer. The present invention is characterized by comprising a filling flow rate calculation means for calculating a filling flow rate control signal proportional to the difference between the estimated water level and the full water level, which makes the water level change rate at full water zero to zero, from the estimated water level and the full water level.
［作用］
このような手段を講じたことにより、１次冷却
材温度、この１次冷却材の充填流量および抽出流
量から加圧器の水位を推定し、この水位推定値と
満水水位とから満水時における水位変化率を零と
する推定水位と満水水位との差に比例した充填制
御信号を演算して求めて充填流量を制御する。[Function] By taking such measures, the water level of the pressurizer can be estimated from the primary coolant temperature, the filling flow rate and the extraction flow rate of this primary coolant, and the water level at full water level can be estimated from this estimated water level value and the full water level. The filling flow rate is controlled by calculating and determining a filling control signal proportional to the difference between the estimated water level and the full water level, where the water level change rate is zero.
［実施例］
以下、本発明の一実施例について図面を参照し
て説明する。[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.
第１図は加圧器の水位制御装置の全体構成図で
ある。同図において、１は原子炉であり、これに
蒸気発生器２、循環パイプ３及び１次冷却材ポン
プ４からなる１次冷却材循環系が接続され、これ
に更に加圧器５が連通して設けられている。 FIG. 1 is an overall configuration diagram of a water level control device for a pressurizer. In the figure, 1 is a nuclear reactor, to which a primary coolant circulation system consisting of a steam generator 2, a circulation pipe 3, and a primary coolant pump 4 is connected, and a pressurizer 5 is further connected to this. It is provided.
この加圧器５は、通常運転中、容積の約60％が
液相で他は気相を構成しており、その運転圧力を
一定に保持し通常の負荷変化に伴う１次冷却材の
熱膨張および収縮による圧力変化、つまり原子炉
１、蒸気発生器２および１次冷却材ポンプ４の１
次冷却系に含まれる各機器での熱により１次冷却
材の体積変化を吸収して許容範囲内に制限すると
ともに、いかなる場合でも最高使用圧力を越えな
いように制御するものである。 During normal operation, approximately 60% of the volume of the pressurizer 5 is in the liquid phase and the rest is in the gas phase, and the operating pressure is maintained constant and the thermal expansion of the primary coolant occurs due to normal load changes. and pressure changes due to contraction, i.e. 1 of reactor 1, steam generator 2 and primary coolant pump 4.
Changes in the volume of the primary coolant due to heat generated by each device included in the secondary cooling system are absorbed and limited to within an allowable range, and the pressure is controlled so as not to exceed the maximum working pressure under any circumstances.
また、循環パイプ３には１次冷却材の充填ライ
ンが接続されており、この充填ラインに充填流量
制御装置６が設けられている。なお、循環パイプ
３には、更に抽出ラインが接続されている。 Further, a filling line for primary coolant is connected to the circulation pipe 3, and a filling flow rate control device 6 is provided to this filling line. Note that an extraction line is further connected to the circulation pipe 3.
さて、加圧器５の満水操作時における加圧器５
での圧力急上昇を防止するために加圧器水位推定
装置７および充填流量演算装置８が設けられてい
る。 Now, the pressurizer 5 when the pressurizer 5 is filled with water.
A pressurizer water level estimation device 7 and a filling flow rate calculation device 8 are provided to prevent a sudden rise in pressure.
加圧器水位推定装置７は、１次冷却材温度Ｔ、
充填流量G1および抽出流量G2を受けて加圧器５
の水位の変化率を演算し求めてその水位を測定す
る機能を持つたものである。 The pressurizer water level estimating device 7 calculates the primary coolant temperature T,
Pressurizer 5 receives filling flow rate G1 and extraction flow rate G2
It has the function of calculating and determining the rate of change in the water level and measuring the water level.
具体的には、第(1)式を演算することによつて水
位を推定する。 Specifically, the water level is estimated by calculating equation (1).
dL／dt＝a1（dT／dt）＋a2（G1−G2） ……(1)
ここで、ｔは時間、a1、a2は定数である。こ
の第(1)式から加圧器５の水位の変化率（dL／dt）
が求められ、さらに第(1)式の右辺を積分すること
によつて水位が求められる。dL/dt=a1(dT/dt)+a2(G1-G2)...(1) Here, t is time, and a1 and a2 are constants. From this equation (1), the rate of change in the water level of the pressurizer 5 (dL/dt)
is determined, and the water level is determined by integrating the right-hand side of equation (1).
また、充填流量演算装置８は、加圧器水位推定
装置７により求められた推定水位と加圧器５の満
水水位との差を求め、満水時における水位変化率
が「０」となるように推定水位と満水水位との差
に比例した充填流量制置信号Ｓを充填流量制御装
置６に送出する機能をもつたものである。具体的
には水位変化率と満水水位L0と推定水位Ｌとの
差が比例するようにする。つまり、
（dL／dt）＝ｂ（L0−Ｌ） ……(2)
（ｂは定数）
を求め、この第(2)式と上記第(1)式とから充填流量
G1を演算し求める。つまり、
G1＝G2−（a1／a2）・（dT／dt）＋（ｂ／a2
）・（L0／Ｌ）……(3)
である。従つて、この充填流量G1により充填流
量制御信号Ｓが作成されて送出される。 In addition, the filling flow rate calculating device 8 calculates the difference between the estimated water level obtained by the pressurizer water level estimating device 7 and the full water level of the pressurizer 5, and adjusts the estimated water level so that the rate of change in water level at the time of full water becomes "0". It has a function of sending a filling flow rate control signal S proportional to the difference between the filling level and the full water level to the filling flow rate control device 6. Specifically, the water level change rate and the difference between the full water level L 0 and the estimated water level L are made to be proportional. In other words, (dL/dt)=b(L 0 −L)...(2) (b is a constant) is calculated, and from this equation (2) and the above equation (1), the filling flow rate is
Calculate and find G1. In other words, G1=G2−(a1/a2)・(dT/dt)+(b/a2
)・(L 0 /L)...(3). Therefore, a filling flow rate control signal S is created and sent out based on this filling flow rate G1.
次に、上記の如く構成された装置の作用につい
て説明する。１次冷却材の温度は、原子炉１、蒸
気発生器２および１次冷却材循環系に含まれる機
器での熱の発生、吸収により変化し、その結果そ
の体積変化が生じる。従つて、この体積変化によ
り加圧器５における水位が変動する。また、１次
冷却材の容積は、抽出流量と充填流量とに差が生
じれば変化する。このように、１次冷却材の温度
変化や抽出流量の変動に対して充填流量を制御す
ることによつて加圧器５における水位が制御され
る。 Next, the operation of the apparatus configured as described above will be explained. The temperature of the primary coolant changes due to the generation and absorption of heat in the reactor 1, the steam generator 2, and the equipment included in the primary coolant circulation system, resulting in a change in its volume. Therefore, the water level in the pressurizer 5 fluctuates due to this volume change. Further, the volume of the primary coolant changes if there is a difference between the extraction flow rate and the filling flow rate. In this way, the water level in the pressurizer 5 is controlled by controlling the filling flow rate in response to changes in the temperature of the primary coolant and fluctuations in the extraction flow rate.
さて、加圧器５の満水操作にあつては、１次冷
却材の温度Ｔ、充填流量G1および抽出流量G2と
が検出されてそれぞれ加圧器水位推定装置７に送
られる。この加圧器水位推定装置７は、１次冷却
材温度Ｔ、充填流量G1および抽出流量G2を受け
て上記第(1)式を演算することによつて水位の変化
率を求める。そして、第(1)式を積分し、水位を推
定する。 Now, when the pressurizer 5 is filled with water, the temperature T of the primary coolant, the filling flow rate G1, and the extraction flow rate G2 are detected and sent to the pressurizer water level estimating device 7, respectively. This pressurizer water level estimating device 7 calculates the rate of change in the water level by calculating the above equation (1) in response to the primary coolant temperature T, the filling flow rate G1, and the extraction flow rate G2. Then, equation (1) is integrated to estimate the water level.
この水位の推定値Ｌは充填流量演算装置８に送
られ、この充填流量演算装置８は上記第(2)式から
推定水位Ｌと満水水位L0との差を演算して求め、
水位の変化率（dL／dt）を満水時における水位
変化率を「０」とするようにする。そして、上記
第(3)式を演算することによつて充填流量G1を求
める。この充填流量G1の充填流量制御信号Ｓが
充填流量制御装置６に送出される。 This estimated value L of the water level is sent to the filling flow rate calculation device 8, and this filling flow rate calculation device 8 calculates the difference between the estimated water level L and the full water level L0 from the above equation (2).
The rate of change in water level (dL/dt) is set so that the rate of change in water level when the water is full is "0". Then, the filling flow rate G1 is determined by calculating the above equation (3). A filling flow rate control signal S for this filling flow rate G1 is sent to the filling flow rate control device 6.
なお、このとき加圧器５における水位の変化が
第２図ａに示してあり、また加圧器５における圧
力が第２図ｂに示してある。つまり、満水時にな
つても加圧器５内の圧力は一定となつている。 At this time, the change in the water level in the pressurizer 5 is shown in FIG. 2a, and the pressure in the pressurizer 5 is shown in FIG. 2b. In other words, the pressure inside the pressurizer 5 remains constant even when the water is full.
このように上記一実施例においては、１次冷却
材温度Ｔ、１次冷却材の充填流量G1および抽出
流量G2から加圧器５の水位を推定し、この水位
推定値Ｌと満水水位L0とから満水時における水
位上昇を停止する推定水位Ｌと満水水位L0との
差に比例した充填流量制御信号を演算して求めて
充填流量を制御するので、加圧器５の水位を自動
的に制御することができ、特に満水操作時の制御
を自動的にできて運転員の負担を軽減できる。そ
して、この操作は、満水時の水位変化率を「０」
に制御するので、満水時の加圧器５における圧力
の急上昇を防止できる。従つて、満水操作に要す
る時間を短縮できる。 In this way, in the above embodiment, the water level of the pressurizer 5 is estimated from the primary coolant temperature T, the filling flow rate G1 and the extraction flow rate G2 of the primary coolant, and this estimated water level value L and the full water level L 0 are calculated. Since the filling flow rate is controlled by calculating and determining the filling flow rate control signal proportional to the difference between the estimated water level L that stops the water level rise at full water level and the full water level L0 , the water level of the pressurizer 5 is automatically controlled. In particular, control during full-water operation can be performed automatically, reducing the burden on the operator. Then, this operation sets the water level change rate at full water to "0".
Therefore, it is possible to prevent the pressure from rising rapidly in the pressurizer 5 when it is full of water. Therefore, the time required for the filling operation can be shortened.
なお、本発明は上記一実施例に限定されるもの
ではなく、その主旨を逸脱しない範囲で変形でき
る。 It should be noted that the present invention is not limited to the above embodiment, and can be modified without departing from the spirit thereof.
［発明の効果］
以上述べたように本発明は、１次冷却材の温
度、１次冷却材の充填流量および抽出流量を受け
て加圧器における水位を推定する水位推定手段
と、この水位推定手段により推定された水位と満
水水位とから満水時の水位上昇を停止する推定水
位と満水水位との差に比例した充填流量信号を求
める充填流量演算手段を備えたものである。[Effects of the Invention] As described above, the present invention provides a water level estimating means for estimating the water level in a pressurizer based on the temperature of the primary coolant, the filling flow rate and the extraction flow rate of the primary coolant, and the water level estimating means. The system is equipped with a filling flow rate calculation means for calculating a filling flow rate signal proportional to the difference between the estimated water level and the full water level, which stop the rise of the water level when the water is full, from the estimated water level and the full water level.
従つて、本発明によれば、１次冷却材の温度、
この１次冷却材の充填流量および抽出流量から加
圧器の水位を推定し、この水位推定値と満水水位
とから満水時における水位変化率を「０」とする
推定水位と満水水位との差に比例した充填流量制
御信号を演算して求めて充填流量を制御するの
で、加圧器満水操作を自動化し、かつ満水時にお
ける加圧器の圧力急上昇を防止できる加圧器の水
位制御装置を提供できる。 Therefore, according to the invention, the temperature of the primary coolant;
The water level of the pressurizer is estimated from the filling flow rate and extraction flow rate of the primary coolant, and the difference between the estimated water level and the full water level is calculated from this estimated water level value and the full water level, assuming that the water level change rate at full water is "0". Since the filling flow rate is controlled by calculating and determining a proportional filling flow rate control signal, it is possible to provide a water level control device for a pressurizer that can automate the filling operation of the pressurizer and prevent the pressure of the pressurizer from rising rapidly when the pressurizer is filled with water.
第１図は本発明に係わる加圧器の水位制御装置
の一実施例を示す全体構成図、第２図は本発明装
置の作用を説明するための図、第３図は従来装置
の作用を説明するための図である。
１……原子炉、２……蒸気発生器、３……循環
パイプ、４……１次冷却材ポンプ、５……加圧
器、６……充填流量制御装置、７……加圧器水位
推定装置、８……充填流量演算装置。
Fig. 1 is an overall configuration diagram showing an embodiment of the water level control device for a pressurizer according to the present invention, Fig. 2 is a diagram for explaining the operation of the device of the present invention, and Fig. 3 is an illustration for explaining the operation of the conventional device. This is a diagram for 1... Nuclear reactor, 2... Steam generator, 3... Circulation pipe, 4... Primary coolant pump, 5... Pressurizer, 6... Filling flow rate control device, 7... Pressurizer water level estimation device , 8... Filling flow rate calculation device.
Claims (1)
る加圧器の水位制御装置において、 前記１次冷却材循環系を流れる１次冷却材の温
度、この１次冷却材の充填流量および抽出流量を
受けて前記加圧器における水位を推定する水位推
定手段と、 この水位推定手段により推定された推定水位と
満水水位とから満水時の水位変化率を零にする前
記推定水位と前記満水水位との差に比例した充填
流量制御信号を求める充填流量演算手段と、 を具備したことを特徴とする加圧器の水位制御装
置。[Scope of Claims] 1. In a water level control device for a pressurizer communicating with a primary coolant circulation system of a pressurized water reactor, the temperature of the primary coolant flowing through the primary coolant circulation system, the primary coolant water level estimating means for estimating the water level in the pressurizer in response to the filling flow rate and the extraction flow rate; and the estimated water level that makes the water level change rate at full water level zero from the estimated water level estimated by the water level estimating means and the full water level. A water level control device for a pressurizer, comprising: a filling flow rate calculation means for determining a filling flow rate control signal proportional to the difference between the full water level and the full water level.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61043134A JPS62201396A (en) | 1986-02-28 | 1986-02-28 | Water-level controller for pressurizer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61043134A JPS62201396A (en) | 1986-02-28 | 1986-02-28 | Water-level controller for pressurizer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62201396A JPS62201396A (en) | 1987-09-05 |
| JPH0579160B2 true JPH0579160B2 (en) | 1993-11-01 |
Family
ID=12655374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61043134A Granted JPS62201396A (en) | 1986-02-28 | 1986-02-28 | Water-level controller for pressurizer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62201396A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0643461U (en) * | 1992-11-25 | 1994-06-10 | 日本電信電話株式会社 | Underground buried object protection net |
-
1986
- 1986-02-28 JP JP61043134A patent/JPS62201396A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0643461U (en) * | 1992-11-25 | 1994-06-10 | 日本電信電話株式会社 | Underground buried object protection net |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62201396A (en) | 1987-09-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR890001252B1 (en) | Feedwater control system | |
| US6198786B1 (en) | Methods of reactor system pressure control by reactor core power modulation | |
| US4650633A (en) | Method and apparatus for protection of pump systems | |
| JPS62480B2 (en) | ||
| JPS629413A (en) | Power plant control equipment | |
| JPH0579160B2 (en) | ||
| US3660229A (en) | Reactor control system | |
| JPH09171093A (en) | Method and apparatus for protecting a pressurized water reactor from nuclear boiling limits and boiling in hot pipes | |
| JPS6117803A (en) | Method and device for controlling nuclear boiling-region position of liquid heating steam-generator | |
| JP2653798B2 (en) | Boiler and turbine plant control equipment | |
| JP4038142B2 (en) | Reactor power controller | |
| JPS59170912A (en) | flow control device | |
| KR810001339B1 (en) | Water supply control system for nuclear power plant | |
| JP3735458B2 (en) | Core flow measurement device | |
| JPH06337298A (en) | Condensate flow rate controller for pwr plant | |
| JP3388320B2 (en) | Container level control method and apparatus | |
| JPS6322534B2 (en) | ||
| JPH04285500A (en) | Output controller for generator | |
| JPS6285887A (en) | Core stabilizer for boiling water type reactor | |
| JPS6132403Y2 (en) | ||
| JPS6139046Y2 (en) | ||
| JPS58219982A (en) | Connecting plant of nuclear power installation and sea water desalting apparatus | |
| JP4504889B2 (en) | Water supply control device | |
| JPS6176993A (en) | Reactor water supply control method and device | |
| JPS5949484B2 (en) | Steam generator water level control device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |